Evaluation of sulfur containing amendments for soil crusting, seedling emergence of tomato and DTPA extractable micronutrients
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Evaluation of sulfur containing amendments for soil crusting, seedling emergence of tomato and DTPA extractable micronutrients
Khan, Mohammad Jamal, M.S.
The University of Arizona, 1992
UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106
EVALUATION OF SULFUR CONTAINING AMENDMENTS FOR SOIL
CRUSTING, SEEDLING EMERGENCE OF TOMATO AND
DTPA EXTRACTABLE MICRONUTRIENTS
by
Mohammad Jamal Khan
A Thesis Submitted to the Faculty of the
DEPARTMENT OF SOIL AND WATER SCIENCE
In Partial Fulfillment of the Requirements For the Degree of
MASTER OF SCIENCE
In the Graduate College
THE UNIVERSITY OF ARIZONA
1992 2
STATEMENT BY AUTHOR
This thesis has been submitted in partial fulfillment of requirements for the advanced degree at the University of Arizona and is deposited in the university Library to be made available to borrowers under rules of Library.
Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or part may be granted by the head of the major department or the Dean of the Graduate College which in his or her judgement the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.
SIGNED:,
APPROVAL BY THESIS DIRECTOR
This thesis has been approved on the date shown below:
Hinrich L. Bohn Professor of Soil and Water Science 3
ACKNOWLEDGMENTS
I avail my self of this opportunity in communicating my sincere appreciation and heartfelt gratification to Dr. H.L. Bohn, Chairman of my thesis committee for his wise guidance, encouragement and timely correction of this manuscript.
I express my indebtedness and gratitude to Dr. David M. Hendricks, who helped me in analytical work and allow me to work in his laboratory. I was fortunate enough to have him on my committee. He has a wonderful ability to tell me that I have erred on some technical points or that I just have not made my self clear.
I also express my appreciations to Dr Jack L. Stroehlein, Dr. G.R. Dutt and Dr. Akif A. Hussen for their help during the course of this study.
There is another group without whom this text would not exist. They are Dr. M.M. Yocoub, Mohammad Yousaf, Mohammad Javed, Rizwan ullah, Akbar Ali Khan, Saud and Mohammad Anwar Baig. They have encouraged me, supported me, guided me and (occasionally, and with good reason) tormented me. Dr. Yacoub taught me a great deal about all the aspects of this research. Mohammad Yousaf typed and read almost everything I write and keep me on track with his comments.
I would also like to thank TIPAN Project and NWFP Agricultural University Peshawar (Pakistan) for their financial support throughout this study.
Last but, by no mean least my thanks to my parents, brothers, sisters and other family members for their love, support, encouragement and phone call which gave me the patience necessary for this work. 4
TABLE OF CONTENTS
Page
LIST OF ILLUSTRATIONS 6
LIST OF TABLES 7
ABSTRACT 8
1. INTRODUCTION 9
2. LITERATURE REVIEW 13
Soil Crusting and Sodicity 13
Crust Prevention and Control 17
Gypsum and Sulfur Bearing Amendments for Reclaming Sodic Soil .... 19
Gysum as an Amendment 20
Sulfuric Acid as an Amendment 23
Iron and Aluminum Sulfate as an Amendments 26
Calcium Polysulfide as an Amendment 27
Effect of Sodicity and Amendments on Micronutrient Availability 29
3. MATERIALS AND METHODS 33
Experimental Work 34
Soil Analysis 36
Plant Analysis 37
4. RESULTS AND DISCUSSION 38
Surface Crust and Seedling Emergence 38 5
TABLE OF CONTENTS-Continued
Dry Matter Yield 42
Chemical Soil Analysis 45
Soil Salinity 48
Exchangeable Sodium Percentage (ESP) 50
DTPA-Available Micronutrients 53
Micronutrient Concentration in Plants 60
5. SUMMARY AND CONCLUSION 66
6. LITERATURE CITED 69 6
LIST OF ILLUSTRATION
Figure: Page
1. Box (120 x 60 cm) showing six strips and the treatment application above the rows 35
2. Crust strength as a function of applied sulfur containing amendments 40
3. The effect of amendments on the numbers of seedling emergence 41
4. Tomato dry matters yield as a function of applied chemical amendments 43
5. The change in pH with depth of soil treated with amendments 47
6. The change in EC with depth of soil treated with amendments 49
7. The change in ESP with depth of soil treated with amendments 51
8. The effect of amendments application on DTPA extractable Zn 55
9. The effect of amendments application on DTPA extractable Mn 57
10. The effect of amendments application on DTPA extractable Fe 59
11. Zn concentration of plants as a function of amendments 62
12. Mn concentration of plants as a function of amendments 63
13. Fe concentration of plants as a function of amendments 65 7
LIST OF TABLES
Table: Page
1. Effect of chemical amendments on crust strength and seedling emergence 39
2. Effect of chemical amendments on dry matter yield 44
3. Effect of chemical amendments on soil pH 46
4. Effect of chemical amendments on electrical conductivity 50
5. Effect of amendments on ESP 52
6. Effect of amendments on DTPA extractable Zn,Cu, Fe and Mn 56
7. Effect of amendments on Zn, Cu, Fe and Mn concentration of tomato seedlings (whole plant) 61 8
ABSTRACT
A greenhouse experiment was conducted to evaluate the effect of five amendments
(H2S04, A12(S04)3.18H20, FeS04.7H20, CaS5 and CaS04.2H20) on crust formation, seedling emergence, dry matter yield (DMY) of tomato and soil properties in a sodic soil from the
Safford Agricultural Center. When applied in equivalent quantities (600 kg/ha S), sulfuric acid and Al-sulfate proved to be the best anti-crusting agents and gypsum the least. Tomato seedling emergence and DMY increased with addition of H2S04 followed by gypsum.
Sulfuric acid was superior in reducing ESP in 0-3 cm depth, while EC was increased with additions of all amendments. In 3-8 cm depth the amendments affected pH, EC and ESP less than at the 0-3 cm depth. DTPA extractable and plants concentrations of Zn, Fe and Mn significantly increased with the addition of various amendments, while Cu was not effected by any amendments. 9
CHAPTER 1
INTRODUCTION
Sodic soils have poor soil water air relationships, which adversely affects plant growth and are difficult to work under dry conditions. Excessive accumulations of certain elements by plants growing in sodic soil may result in tissue rupture and reduced growth.
Elements commonly found in toxic concentration include sodium, molybdenum, boron and bicarbonates (Lai and Stewart, 1990).
Salt-affected soils on a global basis occupy an estimated 952.2 million ha of land, constituting nearly 7 % of the total land area or 33 % of areas of the potential agricultural land of the world (Gupta and Abrol, 1990). To keep pace with population growth an alternative will be to increase cultivated areas to reduce pressure of food shortages particularly in poor, populous countries. Reclamation of salt affected soils will provide a unique opportunity for increasing bioproduction and alleviating pressure on current cultivated soils.
On the basis of determinations made on soil samples and influence of salts on soil properties and plant growth, salt-affected soils are classified into two broad groups, saline soils and alkali soils (Szabolcs, 1974; Gupta and Abrol, 1990).
Alkali soils contain an excess of exchangeable sodium and have sodium carbonate as an important soluble salt. Calcareous soils containing soluble carbonates, exchangeable sodium percentage (ESP) greater than IS and saturated paste pH greater than 8.2 manifest problems associated with alkalinity. It has been reported that an ESP of greater than 15 is usually associated with soil paste pH of 8.2-8.3 (Szabolcs, 1974; Abrol and Bhumbla, 1978). 10
Agarwal et al. (1982) reported a direct positive relationship between ESP and soil pH
for calcareous alkali soils. The high amount of exchangeable sodium associated with high
pH (caused by the presence of NaHC03 and NaC03) causes dispersion of soil aggregates,
lower hydraulic conductivity and formation of a soil crust which adversely affect the plant growth.
Sodic soils on the other hand having a high sodium adsorptive ratio (SAR) which does not necessarily mean a high pH (Kelley, 1948; Beek and Breeman, 1973). In nature, strongly alkaline soils invariably have high sodicity while in this text the word sodicity will be used for simplicity.
Sodic soils have more than 15 % of the soil cation exchange sites occupied by sodium. In fine textured soils values as low as 7 may cause problems especially with low soluble salt contents (Stroehlein and Pennington, 1986).
Crust formation is one of the common features of sodic soils which depends on soil
ESP and electrolyte concentration. The high ESP and low salt concentration induces colloidal dispersion, which contributes to the formation of a dense crust. The practical value of the effect of soil ESP on infiltration rate and crust formation is very important. The effect of soil crusting on seedlings depends on crust strength and thickness as well as the size and vigor of the seedling (Richards, 1953). Hillal (1972) reported that emergence of bean seedlings in a fine sandy loam soil was reduced from 100 to 0 % when crust strength increased from 108 to 273 mbars, whereas Allison (1956) found that the emergence of sweet corn was prevented only when crust strength exceeds 1200 mbar. However the critical crust strength preventing seed emergence depends largely on crust thickness, plant species, and soil wetness (Hillel, 1972). 11
The availability of nutrients, especially micronutrient cations, is reduced in sodic
soils. This low availability is not necessarily related to high ESP but rather with high pH
values. This relationship of micronutrient and alkalinity has been reported in many articles
and books (Lai and Stewart, 1990; Tisdale et al., 1985; Shkolnik, 1984).
The reduced iron availability is due to high pH level which is common to high
bicarbonate soils, rather than the specific ionic effect of bicarbonate. The high pH levels of
sodic soils might accentuate deficiencies of many micronutrients (Bohn et al. 1985).
Reclamation of sodic soils requires that water pass through the profile to carry added
divalent ions (usually Ca) into, and flush exchangeable sodium out of, the root zone. This
can be accomplished by adding chemical amendments. Amendments are materials that
directly or indirectly furnish divalent cations for replacement of exchangeable Na+. The kind
and amount of chemical amendments to be used for reclaiming sodic soils depends on soil
characteristics, the desired rate and extent of exchangeable sodium replacement and costs.
Sulfur and sulfur containing compounds are primarily used for maintenance and improvement
of soil and water affected by salts and sodium (Stroehlein and Pennington, 1986; Gupta and
Abrol, 1990; Prather et al., 1978; Yacoub, 1991). The commonly used amendments are
gypsum, sulfuric acid, aluminum sulfate, iron sulfate, calcium sulfate, calcium polysulfide,
calcium chloride and pyrite. The choice depends on cost and availability.
Many studies have been conducted to evaluate the effectiveness of these amendments
but very few comparative studies so far have been done and the rate and methods and time of placements still need to be investigated. Keeping in view the world wide concern for
improving salt affected soils it was thought worth while to study the effects of sulfiir 12 containing amendments on reducing the soil crust, ESP and pH. A further objective is also to evaluate the amendments affects on micronutrient availability in soil and their uptake by plants. CHAPTER 2
REVIEW OF LITERATURE
Soil Crusting and Sodicitv
Soil crust, a hard compact surface layer has a prominent effect on a number of soil processes, such as a reduction of infiltration and increase in runoff, a slowing of the soil atmospheric gas exchange and an interference with seed germination. Soil crusting has been widely blamed for poor aeration and stimulated considerable interest of soil scientists and agronomists in its effect on the emergence and early development of seedlings.
Taylor (1971) studied the emergence of seedlings in soil with a crust and reported that when an elongating shoot encounters a crust, that is too hard to break through, it may grow horizontally and sometimes emerge through cracks.
Chen et al. (1980) reported two types of crusts by their mechanisms of formation:
(1) those which formed as a result of water drop impact called structural crusts, and (2) those formed by translocation of fine soil particles and their deposition at a certain distance from their original location refered to as depositional crust. The latter is mainly a function of Na which bring about dispersion of the soil. In the same citation, Chen et al. (1980) reported that deposition was marked by the presence of a thin skin also about 0.1 millimeter thick.
Mclntyre (1958) found that the crust consists of two parts: an upper skin seal attributed to compaction of raindrop impact and a deeper "washed in" region of decreased porosity, attributed to fine particle movement and accumulation. He measured thickness of
0.1mm and 2mm for the skin seal and "washed in" zone, respectively. 14
Bresson and Boiffin (1990) studied crust development on a loamy Aquic Hapludalf near Paris in an experimental field to which fertilizers and amendments had been applied.
These treatments over the period of 57 years had induced a range of organic matter contents and exchangeable cation percentages. The macroscopic aspects of soil surface was closely monitored during crusting, and microscopic characterization was carried out at every main crust development stage. Crusting followed the general pattern: 1) sealing of the soil surface by a structural crust; 2) development of depositional crust. Even in the sodic plot where the depositional crust appeared early, the structural crust developed first. They concluded that the process of crust development was faster in a sodic soil, with the earlier and more rapid depositional crust development was mainly due to more dispersion and thickening of the structural crusts.
Miller and Gifford (1974) reported the characteristics that make surface soil especially susceptible to crusting are low organic matter content, high exchangeable sodium and high silt content. These are all related to low structural stability, so that aggregates are easily broken down due to the impact of slaking action of water. A dense massive structure can result, and the soil forms into a hard crust upon drying.
Kemper and Noonan (1970) studied the addition of calcium and sodium to the soil and showed that both Ca and Na have important effects on infiltration. They concluded from their study that Na decreased infiltration because it allowed the aggregates to disperse while
Ca prevented the dispersion and made the surface more stable. It was further reported that the decreased surface crusting and increased seedling emergence can be achieved by applying a narrow band of gypsum over the seeded row, using approximately 100 to 200 kg/ha.
Hillel (1982) studied the effect of crusting on seedling emergence, crust formation 15 and factors affecting crusting formation. He observed that soils exhibiting strong crusting restrict the emergence of seeds. The seedling emergence can only occurs through cracks in the crust. However the critical crust strength which prevents emergence obviously depends on crust thickness and soil wetness as well as on plant species and depth of seed placement.
It was further noted that the crust strength increases as the rate of drying decreases and as the degree of colloidal dispersion increases. As water evaporates, the soil surface often become charged with relatively high concentration of sodic salts and consequently, with a high ESP. With further infiltration by rain or irrigation water salts are leached but the ESP remains high, which induces colloidal dispersion and contributes to the formation of a dense crust.
McNeal and Coleman (1966) studied the effect of solution composition on soil hydraulic conductivity for seven soils of varying mineralogy. They noted a decrease in hydraulic conductivity, with decreasing electrolyte concentration and increasing SAR. The decrease was particularly pronounced for soil high in 2:1 layer silicates, labile hydraulic conductivities being exhibited by those soils containing the most montmorillonite. A soil containing amorphous material was much more stable than the average and a soil high in kaoinite and sesquioxides was usually insensitive to variation in solution composition.
Upadhyaya et al. (1989) conducted a field experiment to measure the soil crust strength with a fully automatic, portable instrument which was developed to measure soil crust strength in shear, rupture, and resistance to penetration. Field tests revealed that the shear technique does not estimate the crust strength reliably. However, both maximum rupture, force per unit width of the crust and maximum penetration force correlate with crust thickness. 16
Shainberg (1985), in his review on the effect of exchangeable sodium and electrolyte
concentration on crust formation, summarized that crust formation is due to two
complementary mechanisms: (1) mechanical breakdown of soil aggregates by the beating action of raindrops, followed by compaction of a thin layer at the soil surface; and (2) chemical dispersion of clay which depends on soil ESP and the electrolyte concentration of the applied water. With soils exposed to rain, 3-5 % exchangeable Na is enough to cause clay dispersion, crust formation and very low infiltration. In his review, he further summarized that the crust consists of two distinct parts: (1) an upper skin seal attributed to compaction by raindrop impacts and (2) a "washed in zone" of decreased porosity attributed to the accumulation of clay particles. When the soil ESP is less than 1, chemical dispersion of clay and the formation of a "wash in zone" is prevented. Conversely, when the ESP of the soil > 4-5, clay movement and the formation of the thick crust (washed in layer) are the dominant mechanisms.
Stroehlein and Pennington (1986) reported that sodic soils have more than 15 % of the soil cation exchange sites occupied by Na but in fine textured soil values as low as 7 may cause problem especially with low salt water and 2:1 swelling clays. Exchangeable sodium also causes high pH values.
Miller and Gifford (1974) reported that the quality of irrigation water,as well as the method and rate of application influence the formation and hardness of a crust. The SAR, a measure of the hazard,is the most important water property related to crust formation.
Some of the sodium salts in water are concentrated at the soil surface by evaporation. If enough sodium is adsorbed by the surface soil, it will disperse and reswell by irrigation or 17
rain and the crust forms without any mechanical energy input to arrange and compact the soil
particles.
Crust Prevention and Control
Crust formation primarily reduces infiltration and affects seedling emergence. The
objectives of all management action has been to minimize the crust formation produced by
either raindrops impacts or chemical dispersion of clay by sodium and to improve the
infiltration rate. A number of organic and inorganic chemicals has been studied by
researchers and plant growers.
Cary and Evans (1974) presented a detailed discussion on prevention and management
of crusted soil. In their review, three main factors were mentioned that are responsible for
crusting include low organic matter, high exchangeable sodium and high silt content. Their
review of literature and research work showed that surface mulching, addition of organic
matter, keeping the soil moist during germination, and use of gypsum can prevent the effect of crusting by improving hydraulic conductivity and emergence of seeds.
Agassi et al. (1982), Kazman et al. (1983) and Keren and Shainberg (1981) reported that chemical dispersion can be prevented by spreading phosphogypsum (or other readily available electrolyte source). In one of their studies Agassi et al. (1981) reported that phosphogypsum at the rate of 5 tons/ha prior to the rain prevented the formation of crust and improved the infiltration rate. Phosphogypsum acted as a slow release salt (Keren and
Shainberg, 1981) supplying sufficient electrolytes to the rain water and preventing clay dispersion. In their study, they further reported that phosphogypsum application increased 18 the final infiltration rate of a sandy loam soil from 7.5 to 12 mm/hr for the sample with an
ESP of 1 and from 0.6 to 10 mm/hr for a soil sample with an ESP of 11.6.
Kumar and Hazra (1989) studied the direct and indirect effects of soil crust strength, soil moisture content and soil management practices (tillage, sowing rates, mulching and breaking soil crust with hand hoe) on seedling emergence of cluster bean (Tetragonolobal grown under dry conditions. Both soil crust strength and soil moisture content showed a significant effect on seedling emergence, but their indirect effect via soil management practices was very low. Among soil management practices, mulching with dry grass at 5 tons/ha soon after sowing and removing the mulch 10 days later was very effective in increasing seedling emergence.
Miyamoto and Stroehlein (1975a,b,c, 1986) extensively studied the effect of sulfuric acid on reclamation of sodic soil. They showed that sulfuric acid provide faster leaching and water movement than does equivalent amount of gypsum. Sulfuric acid showed a greater removal of Na than gypsum and effectively prevented the crust formation.
Kemper and Noonan (1970) reported that the use of gypsum application to sodium affected soils increases the infiltration rate and helped in flocculating the soil. Kemper and
Miller (1974) reported that gypsum applications increased the emergence of seedlings and deceased surface crusting. Sodium is one of the prominent factors in dispersing clay particles and formation of crust. Alawi (1977) reported that gypsum can be effectively used in the reclamation of sodic and saline sodic soil,if these soils are not calcareous, but if there is sufficient calcium carbonate in soil, sulfuric acid will be more beneficial than gypsum. Ryan and Stroehlein (1973) reported that bicarbonate removal from water with sulfuric acid can improve nutrient uptake by crop/plants and can be beneficial in reducing soil crusting, where precipitated calcium carbonate acts as a cementing agent and encourages crusting.
Gypsum and Sulfur Bearing Amendments for Reclamaing Sodic Soil
Reclaiming of sodic soils requires the removal of exchangeable Na+ and its replacement by the more favorable calcium ions in the root zone. According to Lai and
Steward (1990) amendments are materials that directly or indirectly through chemical or microbial action, furnish divalent cations (usually Ca2+) for replacement of exchangeable sodium. Ayers and Westcot (1985) define amendments as substances or materials which improve soil by modifying its physical properties rather than by adding appreciable quantities of plant material. Fuller and Ray (1963) in their report stated that gypsum and sulfur bearing chemicals are not used in the Southwest (Arizona) as plant nutrients since semi-arid and arid soils are usually well supplied with these elements. They further mentioned that gypsum and sulfur bearing amendments are used primarily to improve soil physical condition.
The most commonly used amendment for reclaiming sodic (Alkali) soils can be classified into two broad groups (Gupta and Abrol, 1990; Stroehlein and Pennington, 1986),
(1) those that are soluble calcium salts: CaS04.2H20, CaCl2, phosphogypsum and (2) acids or acid formers: H2S04, iron sulfate, aluminum sulfate, lime sulfur and pyrite.
All chemical amendments share a common characteristic when applied under appropriate soil conditions in that they supply soluble calcium. Acid amendments react immediately with lime to produce soluble calcium. Iron sulfate and aluminum sulfate react with lime and the end product of this reaction are gypsum and Fe and A1 oxides. Gypsum 20
can be used for replacement of sodium and the iron and aluminum salt acts as a cementing
agent holding soil particles together.
Gypsum as an Amendment
Gypsum is one of the most commonly used amendments for the reclamation of sodic
soil because of its low cost, availability and ease of handling. Many published results demonstrate the effectiveness of gypsum in deflocculation, allowing leaching to proceed and prevent crusting.
Loveday (1984) reported that gypsum dissolved to provide, first, a level of electrolyte in the soil solution which maintains sufficient permeability to allow water entry into and through the soil profile and at the same time, provide Ca2+ for exchange with Na. The strength of a surface crust is largely dependent upon its moisture content and because gypsum treatment slows the rate of surface drying (Loveday and Scottor, 1966), the rate of crust development, as well as the strength, will be affected.
Shainberg et al. (1982) pointed out that for calcareous soils, the surface soil may be susceptible to dispersion and crusting under raindrop impact, even though reasonable physical properties may occur throughout most of the profile. In such a situation, gypsum may prevent crust formation by maintaining a sufficient electrolyte concentration.
Mclntyre et al. (1982) conducted field investigations on water and salt movement in an irrigated swelling clay soil, and found that without gypsum, 292 mm water infiltrated in
379 days of ponding, wetting the profile to 2.1 m; with gypsum at 10 tons/ha, 605 mm infiltrated in 145 days, enough of which passed beyond 2 m to raise the groundwater level 21 by 10 m. Data from this experiment clearly demonstrated the presence of low hydraulic conductivity in the upper profile which was ameliorated by the addition of gypsum. In the same experiment Mclntyre et al. (1982) found depths of chloride, beyond which accumulation occurred to be 1.0 m in the absence of gypsum and 2.8 m with gypsum.
Stroehlein and Pennington (1986) in their review on sulfur compounds for soil and irrigation water, reported that gypsum effectiveness is mainly governed by its solubility, fineness and purity; thus it should be finely ground in order to increase its solubility. They further emphasized that gypsum should be mixed with soil in order to increase its contact and solubility as well as its effectiveness.
Fuller and Ray (1963) reported that gypsum is sufficiently soluble in water for effective use on soil, although much less so than some other common soluble salts. At ordinary temperatures, a saturated soil contains about 0.25 percent or 2500 ppm gypsum.
In the same citation, Fuller and Ray (1963) further elaborate that under field condition the solubility of gypsum is influenced by the presence of other salts, time, temperature and fineness and that solubility may be increased several fold if finely ground gypsum is applied.
Mohammad (1972) studied the effect of various sulfur compounds on soil permeability and irrigation water quality and reported that gypsum supplies calcium directly to replace the exchangeable Na+ and sulfuric acid dissolved calcium and magnesium carbonate and bicarbonate which will replace the exchangeable sodium that can be removed by leaching.
He further concluded that the addition of sulfur compounds to low salt irrigation water improved water movement through soil. Gypsum was more economical than sulfur dioxide and sulfuric acid.
Elshout and Kamphorst (1990) reported that the cost of sodic soil reclamation can be 22
reduced when coarse grade gypsum is used as the production and transport prices of this
gypsum are much lower than that of agricultural grade gypsum. In a feasibility study,
laboratory experiments were conducted to evaluate the leaching water requirements for fine
gypsum grades of different particle size distribution. It was concluded from their study that
the leaching water requirement does not differ significantly for the mixture studied, provided
that the percolation rates are low. The total time of reclamation appears to increase with
increasing particle size. It was further concluded that highest efficiency was achieved when
an amount equal to the gypsum requirement was partly mixed with the soil and partly applied
onto the soil surface.
There is a substantial volume of work on gypsum under field condition. Shainberg
et al. (1989) in their review on use of gypsum on soils, reported that the yield of maize,
soybeans, coffee, wheat, rice, beans, peaches, apples, cotton, tomato and alfalfa was
appreciably increased when gypsum was applied to the soil as an amendments. This increase
might be achieved in two ways, first the efficient utilization of other nutrient and calcium as
a secondary element and secondly due to improved physical condition of the soil i.e, good
aeration, optimum infiltration and leaching etc.
Loveday (1974) showed a general relationship between crust strength, seedling
emergence and demonstrated increases of 100% in emergence with gypsum treatment.
Further work by Shannugganathan and Oades (1983b) has confirmed the positive effect of gypsum on emergence, and shown the importance of reducing clay dispersion in establishing good crop stands. 23
Sulfuric Acid as an Amendment
Sulfuric acid is most likely to be considered for reclamation of highly sodic soils which are calcareous and where rapid reclamation is desired.
Overstreet et al. (1951) described the reaction of sulfuric acid in releasing adsorbed sodium under the most efficient condition as follows:
H2S04 + 2CaC03 + 4Na(ad) = = = = > 2Ca(ad) + Na2S04 + 2NaHC03
+ The soluble Na salts, Na2S04 and NaHC03 are removed from the soil by leaching with irrigation water. Under the least efficient conditions the action of sulfuric acid of sulfuric acid can be described as follows:
H2SO4 + CaC03 + 2Na(ad) = = = = > Ca(ad) + Na2S04 C02 + H20
From the above equation, it can be seen that most efficiently one atom of sulfur is associated with the release of four atoms of absorbed sodium whereas least efficiently one atom of sulfur is associated with the release of two atoms of sodium.
Stroehlein and Pennington (1986), in their review on the use of sulfur compound for soil and irrigation water treatment, reported that sulfuric acid not only increases the
2 electrolyte content of water but, reduces or removes the carbonate (C03 ' and bicarbonate
(HCXV) as well.
H2S04 + Ca(H2C03)2 = = = = > CaS04 + 2H20 + C02
H2S04 + CaC03 = = = = > CaS04+H20+C02
This reduces the adjusted SAR which shows that Ca will tend to remain in the solution rather than precipitating out as CaC03 (Miyamoto et al. 1975a).
Alawi et al. (1980) studied the effects of relatively low rate of 93 % H2S04 (2.24 24 tons/ha) and gypsum (3.84 tons/ha) in terms of plant yields (sudan grass) and chemical properties for a two year period. Sudan grass yields were increased significantly by the addition of sulfuric acid and gypsum for the first year but only with sulfuric acid the second year. Soil salinity and ESP were reduced significantly by both amendments one season after application. Sulfuric acid was generally superior to gypsum in terms of yield increases and soil improvement. This study demonstrate the usefulness of low rates of soil applied amendment. Of particular interest is H2S04 which gave significant results at lower rates than gypsum and which is often available as a low-cost byproduct.
Yahia el al. (1975) studied the use of sulfuric acid on reclamation and revegetation of calcareous and sodic soils. The rate of water penetration was measured in columns as well as boxes after concentrated (93%) sulfuric acid was applied to the soil surface. It was concluded that the rate of water penetration increased with increasing acid application rates, but then decreased, with optimum application rates ranging from 5 to 15 metric tons/ha.
Acid was especially effective in increasing the rate of water penetration in sodium affected calcareous soils. The authors further stressed that sulfuric acid may be useful for increasing water penetration of soils of semi-arid regions.
Prather et al. (1978) carried out a laboratory column study on sodic soil reclamation using two soils high in exchangeable sodium and cation exchange capacity. Three amendments (CaS04.2H20, CaCl2.2H20 and H2S04) were used singly as well as in combination to test their effectiveness and efficiencies with respect to amount of amendments, time, and leaching needed. It was noted that H2S04 was more effective than CaS04 and resulted in a more desirable ESP profile than CaCl2. Combining either CaCl2 or H2S04 with 25
CaS04 (proportion of 1/4 and 3/4, respectively) appreciably reduced the time and leaching
needed to achieve reclamation as compared with CaS04 alone.
Stroehlein and Alawi (1981) conducted field and laboratory experiments to determine
the effects of three qualities of irrigation water and their interaction with gypsum and sulfuric
acid on infiltration rate and time and water requirement to leach a saline sodic soil. It was
concluded that sulfuric improved the infiltration rates significantly with all sources of
irrigation water.
Ryan et al. (1977) reported the effect of sulfuric acid application to soil and water on growth and chemical composition of sorghum in greenhouse experiments. Dry matter yield
and plant uptake of P and Fe were significantly increased by treating the soil with acid. In one other study Ryan et al. (1974) reported that the application of H2S04 significantly
increased the DTPA extractable Fe, Mn and Zn.
Chand et al. (1977) evaluated in field experiments the efficiency of eight amendments on soil properties and crop growth in a highly sodic soil. When applied in chemically equivalent quantities gypsum, aluminum sulfate and sulfuric acid were nearly equally effective in improving the soil properties and the yield of barley.
Gumma et al. (1976) studied the effect of sulfuric acid on sodium hazard of irrigation water. Sulfuric acid was applied to the waters at sufficient rates to prevent calcium precipitation under an open system, ranging from 2.1 to 4.7 meq/1. At these acid rates, the pH of irrigation water remained above neutral, however, SAR and ESP in all cases tested were reduced and increased the hydraulic conductivity.
Miyamoto and Enrique (1990) studied the comparative effect of chemical amendment on salt and Na leaching and found that gypsum and sulfuric acid treatment provided lower 26 ratio of sodicity to salinity in percolating solution and relating uniform hydraulic conductivity throughout the soil depth.
Iron and Aluminum Sulfate as an Amendments
Stroehlein and Pennington (1986) reported that when iron and aluminum sulfate are applied to moist soils,they hydrolyze rapidly, producing sulfuric acid as shown by the following reaction.
A12(S04)3 + 6H20 = = = = > Al(OH)3 + 3H2S04
FeS04 + 2H20 = = = = > Fe(OH)2 + H2S04
In the above reaction the acid produced reacts with lime to produce soluble calcium as with direct application of H2S04. It was further reported that iron sulfate is commonly recommended for correcting iron chlorosis in alkaline soils.
Manukyan (1976) reported that ferrous sulfate was more effective in improving aggregate stability and infiltration than H2S04. Iron sulfate contains about 12% sulfur and usually is known as copperas or cake. It is often obtained as a by-product of mining industry. Fuller and Ray (1963) reported that iron sulfate reacts rapidly in a moist soil. The end product of this reaction is gypsum and iron oxides. The gypsum can be used to replace sodium, and the Fe salts acts as a cementing agents holding soil particles together. Studies conducted by Miyamoto and Enriquez (1990) indicated that sulfate of Fe and A1 behaved similarly to gypsum, agreeing with the field study of Chand et al. (1977). It appears that the strong aggregation action of Fe and Al claimed by the product distributor was not reflected in improved soil structure or between water intake than that obtained by gypsum. Studies 27 conducted by Wada et al. (1983) shows that aggregation ability of Fe and A1 is not stronger than that of Ca.
Botkin (1933) studied the effect of acidifying amendments (FeS04, A12(S04)3.18H20) and found that iron and aluminum sulfate reduced soil alkalinity and facilitated water percolation and improved the permeability in alkali (sodic) impermeable soil.
Bower (19S9) studied the effects of chemical amendments for improving sodic soil and reported that solid, granular materials of aluminum and iron sulfate usually have a high degree of purity and are soluble in water and decompose to sulfuric acid which in turn supplies soluble calcium through its reaction with lime. It was also reported that sulfur, sulfuric acid, lime sulfur, iron sulfate and aluminum sulfate application lowered the ESP and increase soluble salts in sodic soil. It was further reported that iron sulfate and aluminum sulfate are generally expensive which was the only objection to using them as an amendments for salt affected soil.
Yaqoub (1991) conducted field and green house experiment to study the effects of soil amendments on crusting, seedling emergence and yield of onion, tomato and peppers. It was found that aluminum sulfate reduced the soil pH and EC more than H2S04, and gypsum and was second in rank as anticrusting agent. He further concluded that A12(S04)3 reduced seedling emergence which might have been due to its toxicity.
Calcium Polvsulfide as an Amendment
Calcium polysulfide (CPS) or lime sulfur (CaSs) is a highly alkaline, brown liquid.
Upon reacting with water the sulfur is precipitated as finely divided elemental sulfur. Thus it might go through the same process as powdered sulfur before it can react with calcium in
the soil to make gypsum (Fuller and Ray 1963). Stroehlein and Pennington (1986) reported
that when CPS is added to water the pH initially increases. While the polysulfides are
alkaline, dilution with water lowers the pH below 10, and S separates in a colloidal form.
The Ca2+ then attaches to clays and replaces exchangeable Na+.
Cairns and Beaton (1976) found that ammonium polysulfide (APS) produced better
yields than CPS and CPS provided higher infiltration rates than APS at equal rates of sulfur.
Mohammad et al. (1979) found increasing infiltration rates with gypsum and S02, but
CPS reached a maximum with a low or intermediate rate. Failure of high application rates was attributed to plugging of soil surface pores with the colloidal sulfur.
McGeorge et al. (1956) reported the usefulness of various polysulfide compound as
soil amendments. They concluded that when applied at rates equivalent to the "gypsum requirement" these compounds increase permeability; however, at the lower rates (e.g.
2xl0Vl ha"1), usually recommended commercially, they may be ineffective.
In comparing CPS, APS and sulfuric acid in the Imperial valley, California, Robinson et al. (1968) found that APS increased water intake rates more than CPS. For three San
Joaquin Valley soils responsive to both gypsum and sulfur dioxide, CPS was ineffective
(Mohammad, 1972).
Tisdale et al. (1985) reported that CPS is mainly used as a soil conditioner and treatment of irrigation water to improve penetration into soil. They showed the following reaction of CPS when added to soil or water.
CaSs + HjO + C02 = = = = > H2S + CaC03 + 4S 29
Because of the colloidal nature of sulfur deposited from polysulfide, it conversion to
sulfate takes place quite rapidly.
Loveday (1984) reported that acidulents such as S and polysulfides must be oxidized
by soil microorganisms. Their effectiveness in field experiments has been variable, perhaps
being related to the presence or absence of appropriate microbial populations.
Effect of Sodicitv and Amendments on Micronutrient Availability
Nutrients such as boron and molybdenum are not likely to limit plant growth in sodic
soils. In fact, with increasing sodicity and soil pH, concentrations of these elements increase in the soil solution and at higher concentration they could prove toxic. However when alkali soils are amended with gypsum and leached, the concentration of these nutrients drops to safe limits and are no longer toxic to plants (Gupta and Abrol, 1990).
The availability of Zn, Cu, Fe and Mn is severely effected in salt affected soils either due to abnormal pH or antagonistic effects of other cations predominant in salt-affected soils.
Yacoub (1991) studied the effects of various amendments on DTPA extractable Zn, Cu, Fe and Mn and found that gypsum decreased extractable Zn and Mn but did not affect the Fe and Cu content. It was further noted that sulfuric acid treatment did not significantly affect the DTPA extractable Zn,Cu,Fe and Mn while aluminum sulfate increased Fe and Zn, decreased Cu but did not affect Mn content.
Foy (1984) reported that an increase in Ca uptake would be expected to reduced Mn absorption. A review by Shainberg et al. (1989) reported that there is also general but less complete agreement that Mn uptake is increased following gypsum application. The reasons 30 for this enhanced Mn uptake is not readily apparent. One reason however, may be the high
Mn concentration of soil solution upon gypsum treatment.
The availability of micronutrients especially of Mn, Zn and Fe, are mainly governed by soil pH. The pH of sodic soil is often more than 8.5 and drastically reduces the availability of these elements to plants. Of special concern is the availability of Zn which has been extensively studied in the rice growing area of India. Shukla and Prasad (1974) reported a large yield increase upon Zn fertilization of alkali soils which is due to the role of zinc in improving the tolerance of crops to a sodic environment. Singh et al. (1983),
Singh and Abrol (1985b) have shown that soil pH chiefly governs Zn solubility and they further reported that the level of sodification was of little consequence.
Singh and Abrol (1983) reported that high ESP had no effect on the Mn, Zn and Cu contents of plants but the Fe accumulation was enhanced. It was further reported that the dry matter, grain and straw yields were decreased with increasing ESP.
Singh et al. (1983) studied the effect of graded levels of four chemical amendments
(CaS04.2H20, CaCl2, A12(S04)3 and (FeS04) on pH of alkali soils and DTPA extractable zinc status of amended soil. Little influence on Zn availability was shown except at high application rates of FeS04, which led to a sharp reduction in soil pH.
Rudakova et al. (1970) reported that plant tissues showing deficiency of zinc were always accompanied by high accumulation of iron. The above mentioned observation demonstrates the antagonistic effects of iron on zinc availability. In one other experiment
(Paribok and Alekseyeva Popova, 1965) with tomato plant it was shown that the uptake of iron, copper, manganese and phosphorous was enhanced under a condition of zinc deficiency.
Verma and Abrol (1980) conducted field studies to investigate the effect of gypsum 31 and pyrites on yield and chemical composition of rice and wheat grown on a highly sodic soil. It was noted that Fe content was higher in the pyrite treated plot than gypsum plots , while Mn content was higher in the gypsum treated plot confirming the antagonistic relationship between Fe and Mn. It was further concluded that the concentration of Fe, Zn and Cu in wheat of the control were higher mainly because of very poor plant growth.
Lindsay and Norvell (1978) developed a DTPA extraction soil test for Zn, Fe, Mn and Cu. They established critical nutrients levels for maize which were: 0.8, 4.5, 1.0 and
0.2 ppm for Zn, Fe, Mn and Cu, respectively. DTPA was selected as the chelating agent because it can effectively extract all four micronutrient metals.
Khan et al. (1987) evaluated the efficiency of five copper extraction procedures in 15 different soils (calcareous, pH > 7.5) of Pakistan and found that EDTA was the best method in term of its high extraction capacity followed by the DTPA soil test under alkali conditions.
Martinez et al. (1987) studied the combined effect of salinity and N fertilization on micronutrient contents in tomato and cucumber plants. It was concluded that salinity generally increased the leaf concentration of micronutrients, except for Mn in cucumber plants where the reverse was true.
Hassan and Olson (1966) studied the influence of applied sulfur on the availability of soil nutrients for corn nutrition. They reported that the heaviest rate of sulfur (5000 ppm) produced toxic effects, a consequence of sharp pH reduction and excessive S and Mn uptake.
They further pointed out that sulfur treatment was beneficial to Cu nutrition at early growth stages while Zn availability increased with decreasing pH.
Ryan et al. (1974) treated four calcareous Arizona soil with sulfuric acid applied in varying degrees of saturation of the acid titrable basicity (ATB) of soil and observed that at 32 less than 100% saturation there was a significant increase in water soluble Mn and in DTPA extractable Fe and Mn as compared with untreated soil. They further concluded that the amounts of Fe and Zn extracted with DTPA increased with the rate of acid application and with time of acid/soil contact at the higher level of acidification.
In one other study Ryan et al. (1977) reported increased uptake of Fe with increasing amount of H2S04 applied. CHAPTER 3
MATERIALS AND METHODS
A greenhouse study was conducted to evaluate the efficiency of various sulfur containing amendments on reducing crust, percent germination of tomato seedlings and the
DTPA extractable micronutrients. A bulk sample of the surface soil (0-20 cm) was obtained from Safford Agriculture Center, air dried and then sieved (2mm).
The Safford Agricultural Center of the University of Arizona, College of Agriculture is located in the Gila River Valley near the town of Safford in south eastern Arizona at the elevation of 900 meters above sea level and at latitude of 32° 29' and longitude of 109° 41'.
This station is 25.5 ha in size, was established in 1946 for agriculture production research.
The station has been used mainly for crop research in relation to saline and sodic soil conditions and related soil and water management. Well water is of poor quality and water diverted from the Gila river usually contains a large amount of suspended materials. The soil sample collected for this study was from a field containing Guest clay as maped by Post et al. (1977). The soil is classified as fine, mixed thermic family of Vertic Torrifluents. The control section averages between 35 and 60 % clay. A substantial amount of montmorillonite is present and is probably the most abundant constituent. The pH ranges from 7.9 to 8.1 with organic matter content less than 2 %. The electrical conductivity ranges from 2 to 6 dS/m with CaC03 equivalent of 0.7 to 2 %. The soil is highly susceptible to swelling, shrinking and crusting. The swelling of clay particles in confined systems causes the size of soil pores to decrease, resulting in low permeability (Mitchell and Donovan, 1991). Poor permeability is viewed as an agronomic problem with severe consequences in arid and semiarid regions due to increased salinity and sodicity and poor soil aeration.
Experimental Work
Greenhouse work was begun in 19 June, 1991. Planter boxes of 60 x 20 (length and width) were used for this experiment. The ground and sieved (2mm mesh size) soil was arranged in the boxes as in a furrow system. The soil depth was 8 cm on average with approximately 12 kg of soil in each division of the boxes (Figure 1).
The experiment was laid out in a randomized complete block design with five treatments and control and five replications for each treatment. The different sulfur containing amendments applied were sulfuric acid, aluminum sulfate, ferrous sulfate, calcium polysulfide and gypsum. Amendment application rates were equivalent to 600 kg/ha as sulfur.
Amendments were applied to the dry soil as follows: Aluminum sulfate [A12(S04)3
18H20], ferrous sulfate (FeS04.2H2) and gypsum (CaSO^Hj) were mixed uniformly with soil in the upper top furrow. Sulfuric acid (H2S04) was applied as a 2 M concentration to the soil surface after tomato seed were sown. Calcium polysulfide (CaS5) was mixed with sufficient water to be spread uniformly over the entire strip in the planter box after sowing the seeds.
Twenty seeds of Rosa tomato (Lvcopersicum esculatuml were sown on 19 June, 1991 with a plant to plant distance of 2.8 cm apart in each row. Seed emergence count was recorded daily for 40 days, beginning 12 days after planting. The planter boxes were irrigated with tap water (ECW =0.38 dS/m) once after 2 days. After 48 hours of irrigation, 35
•20 CM—»| Divider Between Strips
Seeds Soil' Treatment Chemical Box
120 CM
Figure 1. Box (120 x 60 cm) showing six strips and the treatment application above the rows. the penetrometer measurments were made. Penetrometer reading at 5 locations within each
treatment box were averaged. A penetrometer model Cl-700 made by Soil Test, Inc was
used for measuring the crust formation strength. The penetrometer readings were taken at
the time when the soil was neither too dry nor too wet following Yacoub (1991).
The tomato seedlings were harvested on August 4, 1991. The fresh matter was
washed once with deionized water and twice with distilled water to remove the dust and dirt
particles. The biomass was air dried and then dried in an oven for 48 hours at 75°C. The
dry matter yield was recorded as an indication of the effect of sulfur containing chemical
amendments on crust caused by high sodicity.
Soil Analysis
Soil samples from each treatment and replication plots (0-3 and 3-8 cm depth) were
collected and taken to the laboratory. The samples were air dried, ground and passed
through a 2 mm sieve for further soil chemical analysis.
The pH and electrical conductivity were measured on the basis of 1:1 soil water suspension following USDA Salinity Handbook 60 (Richards, 1954).
The trace elements, Zn, Cu, Fe and Mn were extracted by the DTPA soil test
(Lindsay and Norvell, 1978). Twenty ml of 0.005 M DTPA solution was added to 10 gram
soil and shaken on horizontal shaker at a rate of 120 cycles per minutes. After 2 hours
shaking, the suspension was filtered through Whatman 42 filter paper. The filtrate was
analyzed for Zn, Cu, Fe and Mn in Instrumental Laboratory (IL) Vidio 12 using Atomic
Absorption Spectrophotometry and appropriate standards and instrumental parameters
recommended by the manufacturer. 37
Sodium adsorption ratio (SAR) was calculated from the individual cation Ca, Mg and
Na determinations in 1:1 soil water suspension after filtering through Whatman 42 filter paper and the amount of Ca, Mg and Na were determined with ICP (Inductively Coupled
Plasma Optical Emission Spectroscopy). The ESP was calculated from SAR following the
USDA Handbook 60 equation.
Plant Analysis
Trace elements (Zn, Cu, Fe and Mn) in plant samples were determined following wet ashing (Metson, 1972). One gram of ground sample of plant material were weighed in to
Erlenmeyer flasks containing an air condensor and 20 ml concentrated HN03 was added.
The flask was boiled for 2 hours under low heat and then allowed to stand over night. After
24 hours, 10 ml water followed by 10 ml HN03 and 10 ml HCL04 were added and heated until the initial vigorous reaction was over. The solution was gently boiled and the digestion continued for about 1 hour after the disappearance of HN03. After boiling, the solution was allowed to cool and 6N HC1 was added and returned to the hot plate (at low temperature ) and digested for a few minutes to bring into complete solution. The solution was filtered through a Whatman 40 filter paper into a 100 ml volumetric flask and diluted up to the mark.
Zinc, Cu, Fe and Mn were determined with the IL Vidio 12 atomic absorption spectrophotometer by using appropriate standards and instrumental parameters. CHAPTER 4
RESULTS AND DISCUSSION
Surface Crust and Seedling Emergence
Variations in crust strength as measured with a penetrometer and seedling emergence as affected by sulfur bearing amendments are presented in Table 1 (Figure 2). The surface crust strength ranged from 0.31 to 1.21 kg/cm2 being highest for the control plot and lowest for the sulfuric acid treatment. Higher penetrometer readings indicate hard crusts with high resistance to seedling emergence. The values for sulfuric acid and aluminum sulfate were at par but significantly different from iron sulfate, lime sulfur and gypsum. These results show that sulfuric acid is the best anticrusting agent to be used followed by aluminum sulfate.
The superiority of sulfuric acid has been reported by Prather et al. (1978), Overstreet et al.
(1951), Miyamoto et al. (1975), Alawi et al. (1980), and Chand et al. (1977). The high performance of sulfuric acid may be attributed to the fast removal of sodium which acts as a dispersing agent and is a major cause of crust formation. In this study sulfuric acid performed better than gypsum which is in apparent contradiction with the column study of
Miyamoto and Enriquez (1990) who indicated similar performance of both treatments on reclaiming sodic soils. In their soil the dissolution of gypsum was probably faster due to the light textured soil used. These results are also in agreement with the previous work of
Yacoub (1991) who reported the superiority of sulfuric acid as a anticrusting agent.
The average numbers of seedlings emergence as influenced by various amendments are given in Table 1. The highest number (i.e. 13) was recorded from the 39
Table: 1. Effect of chemical amendments on crust strength and seedling emergence.
Treatment Crust Strength Seedling emergence
(Penetrometer reading) (number)
kg cm2
Control 1.21 a* 7.2 be*
H2S04 0.31 d 13.4 a
A12(S04)3 0.34 d 6.2 c
FeS04 0.67 c 10.4 be
CaS< 0.69 c 11.0 be
CaS04 0.89 b 11.8b
LSD (0.05) 0.14 4.84
* Means followed by same letter(s) are not significantly different at the 0.05 level according to LSD test. Means of 5 replications.
sulfuric acid treated plot which was significantly different from the other treatments
(Figure 3). The second highest number was in the gypsum applied plot. The results of the control, iron sulfate and lime sulfur treatments were similar while aluminum sulfate showed the least number of seedling emergence which was significantly less than the control plots.
Visual inspection of the plots throughout the experiment showed that there were more and wider cracks in the untreated plot while the soil treated with acid was fluffy in appearance.
The highest emergence of seedlings due to acid application was due to reduced crust as 40
Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 2. Crust strength as a function of applied sulfur bearing amendments. 41
14.0
Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 3. The effect of amendments on the numbers of seedling emergence. 42 reported by Yacoub (1990), and Cary and Evans (1974). The lowest seedling emergence in the aluminum sulfate treated plot might be due to A1 toxicity. The aluminum toxicities are further confirmed from the fact that initially more seedligs emerged but, following one week from the initiation of the experiment, the seedlings died showing root damage by aluminum.
In addition, aluminum sulfate increased the toxicity by producing highest salt concentration in the root zone to which young tomato seedlings are sensitive (Ayers and Westcott 1985).
In view of the well established beneficial effect of gypsum, its ineffectiveness on crust strength deserves comments.
Although the penetrometer reading (crust strength) was high, the seedling emergence ranked second after sulfuric acid treatment. The explanation that most readily presents itself is that the gypsum treatment slowed the rate of surface drying (Loveday and Scottor, 1966), the rate of crust development and final strength affected since surface crust strength is very largely dependent on its moisture content. These surface strength effects have been recorded in terms of marked improvements in seedling emergence and establishment.
Drv Matter Yield
The trends of the effect of amendments on crust strength and seedling emergence are reflected in the dry matter yield of the tomato crop. The dry matter yield obtained (Figure
4) is also gnificantly higher for the sulfuric acid and gypsum treated plots (Table 2). The average dry matter yields of tomatoes with sulfuric acid and gypsum were nearly at par (4.82 and 4.43, respectively) but slightly lower for gypsum treatment. These results are in agreement with the previous work of Alawi et al. (1980), who reported significantly higher 43
Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 4. Tomato dry matters yield as a function of applied chemical amendments. 44
Table: 2. Effect of chemical amendments on dry matter yield of tomato.
Treatment Dry matter yield (g)
Control 2.97 b*
H2S04 4.82 a
A12(S04)3 2.94 a
FeS04 2.93 b
CaS5 3.34 b
CaS04 4.43 a
LSD (0.05) 1.05
* Means followed by same letter(s) are not significantly different at the 0.05 level according to LSD test.
higher yield of sudangrass with application of H2S04 and gypsum. Chand et al. (1977), and
McGeorge (1956) also reported similar results. The average yields obtained with aluminum sulfate, iron sulfate, lime sulfur and control were significantly lower. Depressed yield with aluminum sulfate and iron sulfate may be due to their abnormally high concentration initially just as it was responsible for low rate of seedling emergence. The beneficial effects of calcium polysulfide (CPS) has been reported by McGeorge et al.(1956), Muhammad et al.
(1979), and Cairns and Beaton (1976) but in the present work, this amendments was less effective. There may be several reason for its ineffectiveness, the most prominent relates to CPS oxidation is due to the presence or absence of an appropriate microbial population. 45
If appropriate microorganisms are not present and sufficient time is not given for complete oxidation of CPS to sulfuric acid and gypsum, the desired benefits can hardly be achieved.
Therefore, for better utilization of calcium polysulfide, the crop should be grown after oxidation takes place. On the other hand Muhammad et al. (1979) found decreased rates of infiltration when high rates of CPS were applied which they reported is due to the plugging of soil surface pores with the release of colloidal sulfur. This may be one of the reasons for lower seed germination and dry matter yield in CPS treated plot.
Chemical Soil Analysis
Results of the pH analysis of soil samples collected from the surface (0-3 cm) and subsurface soil (3-8 cm) after harvesting tomato seedlings are summarized in Tables 3.
Lowering of soil pH is a major objective of applying acid to calcareous sodic soil. All amendments were at least somewhat successful in this regard especially in the 0-3 cm depth.
A significant decrease was observed with the addition of aluminum sulfate followed by iron sulfate and sulfuric acid (Figure 5). As was expected a sharp decrease from sulfuric acid application was not apparent which might be due to neutralization by CaC03 in the soil surface. Gypsum application caused only a slight depression which was not significantly different from the control plot. These results are in agreement with the previous work of
Ryan and Stroehlein (1973), Stroehlein and Pennington (1986), Gumma et al. (1975), Hassan and Olson (1966), and Alawi et al. (1980). Yacoub (1991) reported that aluminum sulfate was the most effective in reducing pH which may be due to its high concentration on the top 46
Table: 3. Effect of chemical amendments on soil pH.
Treatment pH (0-3 cm) pH (3-8 cm)
Control 8.25 c* 8.19 c*
H2SO4 7.54 ab 7.84 a
AI2(SO4)3 7.33 a 8.00 ab
FeS04 7.47 a 7.99 ab
CaSj 7.64 b 7.84 a
CaS04 8.06 c 8.14 c
LSD (0.05) 0.23 0.20
* Means followed by similar letter(s) are not significantly different at the 0.05 leve according to LSD test. Means of five replications. layer of soil. Soil pH values for 3-8 cm depth were very similar to the data shown for the shallower depth.
As compared to the pH of 0-3 cm depth, there was a slight reduction in the pH value of the control plots in 3-8 cm depth. The reason for this small reduction might be due to root production of C02 which dissolved CaC03 and the production of HC03. which slightly depressed the pH but this justification may not true for the plots treated with amendment.
The similarity of pH for the two depths is supported by the previous work of Nefae and
O'Connor (1978). 47
pH (0-3 cm)
pH (3-8 cm)
Control H2S04 AI2S04 FaS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 5. The change in pH with depth of soil treated with amendments. 48
gQil Salinity
Dissolved salt concentrations were assessed by measuring the electrical conductivity
(EC) of soil water extracts (1:1) for the 0-3 and 3-8 cm depth separately using a portable digital electrical conductivity meter. The EC of all the treated soils in top 0-3 cm depth was almost 2 times higher than in the control plot (Figure 6). The average EC values obtained with H2S04, FeS04, CaS5 and gypsum were not significantly different from each other but aluminum sulfate produced significantly higher salinity than gypsum and was similar with the rest of the treatments (Table 4). The lowest value of 3.61 dS/m was recorded in the control plots. This increased salinity is due to electrolytes resulting from the reaction of acidic amendments with alkaline calcareous soil.
These results are in apparent contradiction with the field work of Yacoub (1991) who reported decreased salinity with the addition of sulfuric acid, aluminum sulfate and gypsum.
This contradiction is not surprising because with the application of acid forming amendments the EC increases initially and finally diminishes if sufficient water is ponded on the surface to leach out the salts. In our case, the water ponding in the boxes was not possible and the salts that released were moving up and down upon drying and wetting. The EC value for the 3-8 cm depth were also significantly affected by the various amendments but the values obtained were much smaller than noted for the shallower depth. In this case the trend was somewhat different in that sulfuric acid and lime sulfur were effective in increasing the salinity. This may be due to the deep penetration of these two amendments which were applied with water and may be due to their uniform distribution throughout the depth of the 49
EC (0-3 cm)
EC (3-8 cm)
Control H2S04 AI2S04 Treatment (600 Kg/ha S)
Figure 6. The change in EC with depth of soil treated with amendments. 50
Table: 4. Effect of chemical amendments on electrical conductivity.
Treatment EC dS/m (0-3 cm) EC dS/m (3-8 cm)
Control 3.61 a* 3.41 a*
H2SO4 6.76 be 5.87 c
A12(S04)3 7.04 c 4.73 b
FeS04 6.81 be 4.50 b
CaSj 6.68 be 5.62 c
CaS04 5.97 b 4.32 b
LSD (0.05) 0.97 0.87
* Means followed by similar letter(s) are not significantly different at the 0.05 leve according to LSD test. Means of five replications. box. The small depression of EC in the 3-8 cm depth due to surface applied amendments
(sulfate of Fe, Al and Ca), might be their precipitation on the surface soil.
The increase of salinity upon addition of acid forming amendments has been reported by Miyamoto and Enriquez (1990), Chand et al. (1977), Nefae and O'Connor (1978),
O'Connor and Lee (1978), and Shadfan and Hussen (1985).
Exchangeable Sodium Percentage (ESP)
The ESP data calculated from SAR after harvesting the tomato seedlings in 0-3 and
3-8 cm depths are presented in Figure 7 (Table 5). The ESP of the untreated soil (20%) was 51
ESP (0-3 cm) * ESP (3-8 cm)
20.4 20.q
18.0
15.6 15.7 1S.I 15.4 1 il 14.7
|13.' || I • 11 llH H2S04 AI2S04 F#S04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 7. The change in ESP with depth of soil treated with amendments. 52
Table: 5. Effect of amendments on ESP.
Treatment ESP ESP
(0-3 cm depth) (3-8 cm depth)
Control 20.0 a* 20.4 c.
H2SO4 13.2 a 14.7 a
A12(S04)3 13.8 a 15.8 a
FeS04 13.4 a 15.4 a
CaS5 14.5 b 15.7 a
CaS04 15.6 c 18.0 b
LSD (0.05) 0.95 1.57
* Means followed by similar etters are not significantly different at the 0.05 level according to LSD test. Means of 5 replications. significantly high. Sulfuric acid treatment generally produced the lowest ESP in the surface
0-3 cm depth but ESP in the 3-8 cm depth was slightly higher (Miyamoto and Enriquez,
1990). The pronounced effect of sulfuric acid on dry matter yield, crust prevention and seedling emergence are best reflected in the reduction of ESP. The clear and persistent superiority of sulfuric acid over the rest of the amendments is also reported by Prather et al.
(1978). The ESP values obtained for aluminum sulfate and iron sulfate were comparible to the sulfuric acid treatment. Aluminum sulfate and iron sulfate are considered best for displacement of Na from the exchange site but their use in field studies is limited due to their toxic effect and increase availability of heavy metal by plants as a result of sharp reduction in pH. Therefore, if speedy reclamation is desired their application will be highly beneficial.
Lime sulfur was ranked fourth in reducing ESP as was expected due to its dependance on microbial oxidation. In the short time of the greenhouse experiment, lime sulfur efficiency has always been under estimated. Gypsum resulted the least and shallowest removal of exchangeable Na of all amendments applied (Prather et al. 1978). This can be accounted for by the limited solubility and plugging of soil pores by gypsum (Yahia et al.
1975). Chand et al. (1977) also showed that gypsum is relatively less soluble and require more time and water for its dissolution as compared with other amendments. Similarity, Dutt et al. (1972) reported that gypsum is effective in reducing the sodium content of soil in the
Safford area, but the application rates required are generally excessive.
By comparing the ESP values of the surface soil with the 3-8 cm depth, showed a small increase in ESP values but as whole the pattern of ESP in the 3-8 cm depth reduction with respect to amendments applied was the same as was noted in the surface soil. This small increase in surface soil may be attributed to the swelling nature of clay
(montmorillonite) or more precipitation of Al, Fe, and Ca, on the surface soil.
DTPA-Extractable Micronutrients
DTPA-extractable Zn, Cu, Fe and Mn as affected by various amendments are shown in Table 6. DTPA extractable Zn exceeded the critical limits (Lindsay and Norvel 1978, 0.8 ppm for maize, and Takkar and Mann (1975), 0.6 ppm for rice in sodic soils). However, the increased Zn content due to amendment addition was significant (P=0.05), as compared 54
to untreated plot. The highest Zn content (14.23 mg/kg) was noted when iron sulfate was
added as an amendment followed by H2S04 treatment, while aluminum sulfate was least
effective (Figure 8). The increased in concentration of available Zn in the treated soil is due
to the reduction of pH by the amendments. The DTPA available Zn was negatively
correlated with pH of 0-3 cm depth (r = - 0.65). Singh et al. (1983), Sherma et al. (1982),
and Takkar and Singh (1978) reported the inverse relation of pH and DTPA available Zn
content. Singh, et al. (1983), and Singh and Abrol (1985b) reported that soil pH is the major
factor that governs Zn solubility, the level of sodiflcation was of little consequence in their
study. The effect of various amendments on DTPA Zn availability (Singh et al., 1983)
shows that iron sulfate, gypsum and aluminum sulfate were equally effective in increasing
the Zn content in sodic soils. Our results were in agreement with the previous work of
Sherma et al. (1982), Singh et al. (1983), and Takkar and Singh (1978). It can be concluded
that pH is the major factor controlling the availability, rather than soil sodicity. It should
also be noted that not all basic soils are Zn deficient because of mechanisms such as chelation
of Zn by naturally occurring organic substances may compensate for the low solubility of Zn
at high pH.
Copper is not expected to be deficient in Safford soil because of low organic matter
content which reduces the chance of chelation and fixation. However, the high pH value, dry weather conditions and the calcareousness of soils in Arizona are not conducive to the
availability of copper. From the results in Table 6, it is apparent that soil treated with the
various amendments did not affect the DTPA extractable Cu. Singh and Abrol (1983)
reported a similar results. According to Lindsay and Norvel (1978) and Khan et al. (1987),
the Cu level was greater than the critical limits. Therefore, the Safford soil contains Cu at 55
Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 8. The effect of amendments application on DTPA extractable Zn. 56
Table: 6. Effect of amendments on DTPA extractable Zn, Cu, Fe and Mn.
Treatment Zn Cu Fe Mn
(mg/kg) (mg/kg) (mg/kg) (mg/kg)
Control 1.6 c 43.8 11.8 a* 20.9 a*
H2SO4 10.6 a 40.9 21.7 b 29.5 a
A12(S04)3 9.5 a 46.5 14.7 ab 52.3 b
FeS04 14.3 b 45.1 53.9 c 36.4 ab
CaSj 9.8 a 40.6 15.5 ab 46.3 b
CaS04 8.5 a 46.0 15.8 ab 25.1 a
LSD (0.05) 3.34 - 9.74 16.04
* Means followed by similar letters are not significantly different at the 0.05 leve according to LSD test. Means of 5 replications. levels that are not toxic nor deficient to plants. That is confirmed by Brady (1984) who suggested that the copper range (5-150 ppm) in soil is sufficient for all agricultural crops.
Plant available (DTPA) Fe values as a function of various sulfur bearing amendments are given in Table 6. The available Fe generally increased with various amendments but the highest (P = 0.05) amount was observed when iron sulfate was added followed by sulfuric acid treatment. The results obtained for the control, aluminum sulfate, and lime sulfate were comparable statistically but the lowest Fe content was extracted from untreated soil (Figure 9). There was a negative relation (r = - 0.42) with pH in the upper 0-3 cm 57
60.0
52.3 50.0
X 40.0
B
C 30.0 •j0) a S c 20.0
10.0
0.0 Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 9. The effect of amendments application on DTPA extractable Mn. 58 depth. Tisdale et al. (1985) reported that Fe3+ and Fe2+ in solution decreases 1000 fold and
100 fold, respectively , for each unit increase in pH. Interestingly enough, the addition of aluminum sulfate reduced the pH the most but the DTPA extractable iron content was not reflected in this treatment which suggests that the effect of a particular acid treatments on the availability of nutrients in one soil does not necessarily exhibit a similar effect in other soils
(Nefae and O'Connor, 1978). The main reason for the differential effect of acid on various soils is the different buffering capacities of those soils which can be determined by the acid titrateable basicity (ATB) index as suggested by Miyamoto et al. (1973). Soil acidification with H2S04, FeS04, (NH4)2S04 and A12(S04)3 is also reported by Gupta and Cornfield
(1964). The significantly high value of DTPA extractable Fe in the iron sulfate treated plot was not due to pH but may be attributed due to the application of Fe (Barbaria and Patel
1980).
Tne results of DTPA extractable Mn were significantly affected by the addition of various amendments (Figure 10). The significantly negative correlation (r= -0.80) of Mn and pH is worth noting. The maximum reduction in pH was observed in the aluminum sulfate treated plot, thus the significantly higher Mn concentration is observed in this soil.
It is worth mentioning here that the lowest seedling emergence and reduced dry matter yield might be the result of Al and Mn toxicities. In all the treated and untreated soils the Mn concentration was above critical limits (Lindsay and Norvel, 1978). Gypsum was least effective in increasing the availability of Mn because it is least effective in reducing the pH.
Yacoub (1991) also reported the superiority of aluminum sulfate for increasing Mn availability. 59
Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 10. The effect of amendments application on DTPA extractable Fe. 60
Micronutrient Concentration of Plants
Zinc concentration was high in plants grown in soils treated with sulfuric acid
followed by gypsum.These two amendments were significantly different from the other
amendments and the untreated plots. Plants grew less well in the control, and the Al and Fe
sulfate treated plots. From the data in Table 7 (Figure 11), it is clear that the Zn
concentration was greater then the critical levels (11 ppm Takkar and Mann,1975) in the
control and iron sulfate treated plots. The low uptake of Zn in the control might be due to
Na toxicities. Firing and scorching of the tips and margins of lower leaves was observed in
the control plot which resembles typical Na toxicity (Takkar and Nayyar, 1981). No visual
deficiency symptoms of Zn were observed in the iron sulfate treated plots but the low stand
of tomato may be indicative of an antagonistic effect of Fe on Zn uptake of plants.
Antagonistic effects of Fe on Zn has been reported by Takkar and Nayyar (1981) in the rice growing areas of India. Tisdale et al. (1985), also reported antagonistic effect of Zn with
Fe, Cu and Mn. Many of the results have been confusing because the accentuated symptoms
of Zn deficiency are not always accompanied by reduction in Zn concentration.
Tomato is mildly sensitive to low levels of available Zn (Tisdale et al., 1985), so that
plant yields in calcareous sodic soils can be increased with addition of Zn fertilizers. The
increased Zn concentration in the gypsum treated plot is supported by Takkar and Nayyar
(1981) who reported almost similar results.
The Cu concentration in tomato seedlings was not significantly affected by any of the amendment. The results of the control were almost comparable with the treated plots 61
Table: 7. Effect of amendments on Zn, Cu,Fe and Mn concentration of tomato seedlings (whole plant).
Treatment Zn Cu Fe Mn
(mg/kg) (mg/kg) (mg/kg) (mg/kg)
Control 4.8 d* 30.3 131 d* 24.3 c*
H2S04 21.6 a 31.5 282 b 39.5 b
A12(S04)3 14.8 b 29.0 198 b 60.8 a
FeS04 8.9 c 37.3 1434 a 36.9 b
CaSs 16.5 a 32.0 133 d 24.5 c
CaSO, 19.4 a 33.5 140 d 27.0 c
LSD (0.05) 4.84 212.22 7.12
* Means followed by similar letters are not significantly different at the 0.05 level according to LSD test. Means of 5 replications. indicating that Cu is very high in the Safford soil for most agricultural crops with little chances of Cu deficiency.
In case of Mn concentration in plants (Figure 12), the effects of various amendments was significant (p = 0.05). The highest value (60.8 mg/kg) was observed in the Al-sulfate treated soil followed by H2S04 and iron sulfate addition. The results of lime sulfur, gypsum and control plots were at par showing that Ca uptake (not determined) might depress Mn concentration in plants. Foy (1984) reported reduced Mn absorption when plant Ca uptake was high. In the Al-sulfate, Fe-sulfate and H2S04 treated plots the increased uptake may be 25.0
21.6
20.0 'hfl a \ M 6 w 15.0 c • oH <+> 2 £ g io.o c 6 £ 5.0
0.0 Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 11. Zn concentration of plants as a function of amendments. 63
70.0
Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 12. Mn concentration of plants as a function of amendments. 64 due to reduction in pH by these amendments. Garey and Barber (1952) in one of their studies on Mn availability with sulfur addition reported that the Mn content of soybean increased over the check with addition of chemical amendments and the increase was consistent regardless of the chemical applied. In addition, the role of treatments which lower the pH level is important. Their effects are related directly with the magnitude of the pH reduction.
There was a dramatic increase in Fe uptake by the plant when FeS04 was added as an amendment (Figure 13). The highly significant value (1434 mg/kg) suggests that the low seedling emergence and yield of tomato as compared to other treatments may be due to iron toxicity. The results of control, gypsum and lime sulfur were comparable, but the addition of H2S04 increased the tissue Fe concentration. Tisdale et al. (1985) reported 50-250 ppm sufficiency level of Fe in plant tissues. Ryan et al. (1985) reported increase in plant uptake of Fe with addition of H2S04. It can be concluded from these results that the poor growth of the tomato plants in the Fe treated plot might be due to higher concentration of Fe
(Verma and Abrol, 1980). 1600.0
1434.0 1400.0
-So 1200.0 X
wS 1000.0 c o | 800.0 a | 600.0 o u £ 400.0
200.0
0.0 Control H2S04 AI2S04 FeS04 CaS5 CaS04 Treatment (600 Kg/ha S)
Figure 13. Fe concentration of plants as a function of amendments. 66
CHAPTER 5
SUMMARY AND CONCLUSION
Although considerable progress has been made in the past toward understanding the problems associated with management of salt-affected salts, yet the rehabilitation of such lands is proceeding at snail's pace. This is because farmers of salt-affected soils have poor resource endowment, which is not readily enhanced by the fragile and uncertain infrastructure. Reclamation of salt-affected soils requires additional agriculture inputs such as amendments, water and infrastructure for drainage. Requirements of extra resources for practicing agriculture on such lands limits the pace of reclamation on an intensive scale.
The purpose of the present study was to evaluate and identify the efficiency of sulfur bearing amendments on reducing surface crust, seedling emergence of tomato, dry matter yield, DTPA extractable micronutrients and micronutrients concentration of tomato plants in the greenhouse. A bulk soil sample (0-20cm) was obtained from Safford Agricultural Center of the University of Arizona, College of Agriculture, University of Arizona. The ground and sieved soil (2 mm mesh size) was arranged in boxes as in a furrow system. The experiment was laid out in a randomized complete block design with five amendment treatments and control with five replications for each treatment. The amendments applied were H2S04,
A12(S04)3.18H20, FeS04.7H20, CaS5 and CaS04.2H20. Rates were equivalent to 600 kg/ha as sulfur. Tomato seeds were sown in each planter box at the rate of 20 seeds per box.
The penetrometer index showed that sulfuric acid was the best anti-crusting agent followed by AI2(S04)3 while gypsum was least efficient but significantly better than control.
The seedling emergence values showed a highly significant superiority of H2S04 over other 67 treatments and the control. The dry matter yields from H2S04 and gypsum plots were significantly higher than other treatments and control.
Aluminum sulfate and iron sulfate were more effective in reducing soil pH in 0-3 cm followed by sulfuric acid, however the differences among these three amendments were not significant. Gypsum did not lower the pH appreciably and was comparable to control. The values obtained for pH in 3-8 cm depth followed the same trend statistically as in 0-3 cm depth but was not reduced as was observed in 0-3 cm depth.
Electrical conductivity was increased significantly by aluminum sulfate and iron sulfate in 0-3 cm depth followed by H2S04 against control and gypsum but the increase in
EC at 3-8 cm was comparatively less.
With respect to ESP and reclamation, H2S04, Al-sulfate and Fe-sulfate treated plots showed a high degree of superiority over untreated, gypsum and lime sulfur treated plots.
However, gypsum and lime sulfur were significantly different from untreated plots.
Over all, these results showed that H2S04, Al-sulfate and Fe-sulfate were superior followed by gypsum. Lime sulfur was not as beneficial in reclaiming sodic soil as the rest of the amendments and the reason is that insufficient time elapsed for oxidation of the lime sulfur. It seems possible that the action of oxidizing microorganisms may have been inhibited by the severe sodic condition in this study.
Iron sulfate and H2S04 were effective in increasing DTPA extractable Zn and Fe, while DTPA extractable Cu was not affected by the addition of any amendments. DTPA extractable Mn was highly increased by aluminum sulfate treatment followed by lime sulfur.
Plant Zn concentration was significantly increased by sulfuric acid and gypsum and iron sulfate was less effective showing antagonism. A somewhat similar picture was shown by 68 the Cu concentration in plant as was shown for DTPA extractable Cu. The effect of amendments were short of significance as compared to untreated plot. Addition of Al-sulfate slightly reduced Cu concentration in plants.
Iron concentration was significantly higher in plots treated with iron sulfate which may be toxic to plants. Gypsum, lime sulfur and untreated plots showed no significant differences. The Mn concentration was significantly increased by Al-sulfate treatment followed by H2S04 and Fe-sulfate. The effectiveness of gypsum and lime sulfur on Mn uptake was negligible as compared to untreated plots.
In view of the above summarized results, it can be concluded that the choice of amendments depends upon (1) soils, (2) the time required for amendments to react in the soil, (3) the availability of the materials (equipments and infrastructure), and (4) the cost of amendment per unit of Ca it supplies either directly or indirectly by reaction with CaCO, in soil. The rate at which various correctives become effective varies widely. Lime sulfur is slow acting, because of the intermediate biological reaction which is necessary. Gypsum is effective as soon as it goes into solution. Sulfuric acid is very quick acting. Iron sulfate and
Al-sulfate are also quick acting but, may cause toxicities to the delicate roots growing at the time of germination. These conclusions must be viewed in light of experimental field conditions. 69
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