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Home , Ammonium chloride, Ammonium sulfate

AS A : CHLORIDE

EFFECTS ON YIELDS AND UPTAKE OF NUTRIENTS BY CROPS

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

Robert Woodson Teater, B.S., M.S. The Ohio State University

1957

Approved by:

Adviser Department of Agronomy AC KNOWLED GEMENTS

The author wishes to express his sincere appreciation and thanks to Dr. H. J. Mederski under whose supervision and guidance this study was conducted; to Dr. G. W. Volk for his advice, encouragement, and criticism of the manu­ script; and to Dr. E. 0. McLean and Dr. C. J. Willard for criticism and assistance in preparing the manuscript.

Thanks is also extended to other faculty members and graduate students of the Department of Agronomy for their assistance and cooperation during the course of the study.

The author is grateful for the financial assistance provided by the Columbia Southern Chemical Corporation through a grant-in-aid agreement with the Ohio Agricultural

Experiment Station.

For her patience and assistance the author is deeply grateful to his wife. TABLE OF CONTENTS

Page

INTRODUCTION...... 1

REVIEW OF LITERATURE ' . 5

NATURE AND SCOPE OF THE INVESTIGATION...... 12

I. GENERAL FIELD STUDIES

MATERIALS AND METHODS. * ...... 13

Soil, Crops, and ...... 13

Sampling and Harvesting...... 14

Analytical Procedures...... 15

EXPERIMENTAL...... 21

Comparison of and Ammonium in Broadcast Applications for Continuous Corn...... 21

Procedure...... 21

Results and Discussion...... 21

Comparison of Ammonium Chloride and in Row Applications for Corn...... 30

Procedure...... 30

Results and Discussion...... 31

Comparison of Ammonium Chloride, and Ammonium Sulfate for when Applied at Planting...... 33

Procedure...... 33

Results and Discussion...... 33

iii \

Page

Comparison of Ammonium Chloride, Ammonium Nitrate, and Ammonium Sulfate for Wheat Applied as Spring Top Dressing...... 34

Procedure...... 37

Results and Discussion...... 37

Comparison of Ammonium Chloride, Ammonium Nitrate, and Ammonium Sulfate for Oats when Applied at Planting...... 38

Procedure...... 38

Results and Discussion...... 38

SUMMARY AND CONCLUSIONS...... 4l

II. NUTRIENT ION UPTAKE STUDIES

MATERIALS AND METHODS...... 43

Technique of Study...... 43

Analytical Methods...... 46

EXPERIMENTAL...... 49

Optimum Time and Solution Concentration for Accumulation of KC1 by Corn Seedlings...... 49

Procedure...... 49

Results and Discussion...... 49

Relative Competitive Effects of Chloride, Nitrate, and Phosphate Anions on Their Mutual Uptake by Corn Seedlings...... 51

Procedure...... 52

Results and Discussion...... 52

iv Page

Exchange of Plant with in the Outside Solution...... 59

Procedure...... 60

Results and Discussion...... 60

SUMMARY AND CONCLUSIONS...... 65

LITERATURE CITED...... 65

AUTOBIOGRAPHY...... 70

v LIST OP TABLES

Page

Table 1. Effect of form of nitrogen and rate of broadcast application on yield of corn. . . . 23

Table 2. Chloride content of Miami silt loam plow layer under different fertilization treatments over a two year period...... 24

Table 3. Chloride content of corn plant leaves grown on Miami silt loam under different fertilization treatments...... 26

Table 4. Nitrogen and phosphorus content of corn leaves as compared to chloride content. . . 28

Table 5- Effect of high applications of ammonium chloride and ammonium sulfate on pH. . 29

Table 6. Effect of source of nitrogen on yield of corn and on chloride* nitrogen* and phosphorus content of the leaves...... 32

Table 7* Yield of wheat as affected by various sources of nitrogen and rates of fertili­ zation...... 35

Table 8. Chloride content of wheat plants and grain yield as affected by various sources and rates of nitrogen...... 36

Table 9 . Chloride content of soil* chloride and nitrogen content of oat plants* and yield of oats as affected by various nitrogen carriers and rates of application...... 39

Table 10. Effect of absorption time and solution concentration on accumulation of KC1 by corn seedlings...... 50

Table 11. Change in pH of KC1 solution after absorp­ tion by corn seedlings for different periods of time...... 50

vi Page

Table 12. Uptake of various combinations of potassium salts by corn seedlings...... 5^-

Table 13. The effects of aeration and nitrate con­ centration of the substrate on uptake of nitrate and loss of chloride by corn seed­ lings...... 62

vii LIST OP FIGURES

Page

Fig. 1. Cell assembly used to determine chloride. . . 17

Fig. 2. Potentiometric titration of 15 ml. of 0.01 N KC1 solution with 1/71 N AgNO^. . . . 19

Fig. 5. Eleven day old corn seedlings grown in silica sand...... ■ ...... 47

Fig. 4. System for aeration of corn seedlings during uptake studies...... 47

Fig. 5. Relative effects of the complementary ions Cl“ or HgPO^ on the uptake of NOz" by corn seedlings...... 55

Fig. 6. Relative effects of the complementary ions NO" or HpPO: on the uptake of Cl" by corn seedlings...... 56

Fig. 7 . Relative effects of the complementary ions Cl“ or NOz on the uptake of HpPOju by corn seedlings...... 57

viii INTRODUCTION

Ammonium chloride is produced primarily as a by-product of the for making . Normally, the ammonium chloride is decomposed by lime and the formed is recycled in the process. However, with an out­ side source of ammonia, the ammonium chloride may be extract­ ed from the process and used as a nitrogen fertilizer or for other purposes. As a nitrogen fertilizer it would com­ pete with other nitrogen materials provided it was economi­

cally priced and that the total chloride content would not

exceed the point where injury to crops occurs.

The effects of chloride have been reported to be either beneficial or detrimental depending upon the concentration,

growth medium, crop, and climatic conditions. The -essenti­

ality of for plant growth has been neither fully

affirmed nor denied. At any rate, large quantities are not

required. In fact, it has long been known that large quanti­

ties are in some way detrimental to most crops. Rather large

amounts of potash fertilizer in the form of potassium chlor­

ide are being applied to the in eastern United States.

Thus, additional amounts of chloride may bring about a tem­

porary but undesirable excess of soil chlorides immediately

following the application of fertilizer.

1 The purpose of this investigation is to evaluate ammonium chloride as a source of nitrogen for field crops and to secrue information relative to its properties and effects on soil-plant relationships. The mechanism of chloride injury will he a prime consideration in this in­

vestigation. REVIEW OP LITERATURE

The element chlorine occurs in most soils and plants and it is usually in the form of soluble chlorides.

The chloride ion, being extremely mobile, is held very slightly by soils and may be taken up by most plants with extreme ease. The amount of Cl in plant material is quite variable. The extremes of Cl content in Kentucky burley tobacco were 0.02 to 1.05 per cent and in some dark grades the extremes were 0.04 to 2.99 per cent (44). The use of fertilizers containing Cl increases the Cl content of the sap of corn plants in approximate proportion to the amount supplied in the fertilizer (39). Irwin (30) found the average Cl concentration of the cell sap of Nitella to be

0.128 M. This value was much higher than that of the water in which the plant had grown.

The presence of Cl in plant material has led to several investigations concerning plant requirements for and toler­ ance to this element. The literature on this subject,

though not extensive, is difficult to coordinate and summar­ ize because of the diverse experimental conditions and pro­ cedures employed in both the field and laboratory.

Although the essentiality of Cl for plant growth has not been wholly accepted, most work shows some beneficial response from its presence in small quantities. Eaton (17) reported beneficial effects of this element for growth of tomatoes and cotton in sand and solution cultures. Lipman

(34) found that buckwheat and peas were improved when Cl was present in the solution cultures. Recently, Broyer (9) and his associates have indicated that Cl is essential and have proposed its classification as a micrometabolic nutrient element for higher plants.

Whereas small concentrations of Cl may be beneficial to some plants, excessive amounts usually are detrimental.

Attempts have been made to set tolerance levels for some plants (9)j however, these usually must be quite general.

Eaton (17) points out that

the terms "critical concentration," limit of tolerance," and "threshold values," ...do not appear to be well suited to descriptions of responses of plants to chloride and sulfate salts. ...The limit of tolerance of any plant appears to be an intangible concept, since death takes place slowly over a range of concentrations.

Thus plant tolerance to Cl is ill-defined unless con­ ditions are specified in detail. Some crops are more tol­ erant to high Cl concentrations than others. Sugar beets and asparagus are considered to be very tolerant to Cl while clover and sugar cane-are reported to be extremely sensitive to its presence (2). Flax, potatoes, hemp, buckwheat, digi­ talis, and lupine are all sensitive to a surplus of Cl (46).

Tottingham (49) observed that the variety of the plant was more important than the type of soil in determining the

effect of chlorides.

Morphological and physiological effects in the plant

attributed to the presence of Cl are quite varied. In­

vestigations with potatoes have indicated that the use of

chloride when compared with sulfate resulted in a decrease

in starch and dry matter content of the tuber (4, 16, 26).

With an increase of chloride in the medium the Cl content of

the potato plant was, as a whole, increased. In general,

greater vine yields were obtained with the chloride than

with the sulfate treatment.

Garner and his associates (22) found that an applica­

tion of 100 pounds or less of Cl per acre may seriously

interfere with carbohydrate metabolism in tobacco plants

by disturbing the amylolytic activity in the leaf. Ex­

cessive starch accumulated in the leaves which became thick­

ened. Excessive Cl produced muddy leaf colors in the cured

tobacco and altered the toughness and elasticity of the

leaves. The adverse effect of Cl on combustibility was

partly due to reduction in the amount of KgO which may have

existed in the leaf in combination with organic .

In studying the importance of Cl for vegetable plants

Schuphan (43) found that Cl brought about xeromorphic

changes in the morphology of the plants, increased the con­

centration of the cell sap, reduced transpiration and in­

creased water uptake. Owing to its effect on enzyme activity excessive amounts of Cl interfered with carbohydrate metabol­ ism. Hydrogen ion concentration was increased in the sap of plants by increased Cl (39) but not by SO^ (17). Other physiological effects are reviewed quite thoroughly by

Miller (38).

The foregoing review of some effects of Cl on plant growth emphasizes the caution which must be exercised with use of any Cl bearing fertilizer. Because of price* KC1 has been and probably will continue to be a primary source of potassium. The practical use of ammonium chloride depends on whether or not field crop plants will "tolerate" Cl in addition to that supplied as KC1.

The most extensive research with NH4CI from the stand­ point of field use has been conducted in Europe. A mixture of KC1 and NH^Cl secured by the application of the Solvay process to sylvinite was produced in France and Russia under the name of Potazote (46). I. G. Farben in Germany discon­ tinued the production of NH^Cl as a fertilizer in 1933 and switched to Kalammonium* a mixture of limestone and NH^Cl.

Results from use of these materials are quite complex and may be studied in the survey by Weishut (51).

In field experiments on an alluvial soil in India* Ghosh and associates (24) found that NH^Cl and the double (3/4

NH/jN and 1/4 NO^-N)* both containing about 26 per cent nitro­ gen* were as effective as equivalent amounts of (NH^gSOlj in increasing yields of wheat and paddy. NH4CI at 40 pounds of nitrogen per acre doubled the Cl content of wheat, mainly in the straw. Chloride accumulation in the surface soil was rapidly decreased by irrigation. Results reported from a

12 year lysimeter study in Tennessee (36) showed 70 per cent recovery of Cl from added NH4CI in the second year and 96 per cent recovery by the fourth year. From these and earlier findings it was concluded that measurable accumulations of chlorides would not develop in soil or in subsoil from the use of fertilizer Cl in humid regions.

Besides rainfall and condition of subsoil drainage the accumulation of Cl would depend on the extent to which it is held by soil colloids. Toth (47) measured the adsorption of Cl by clays before and after the free iron oxides had been removed, and found the untreated clays adsorb this ion. The Cecil soil, high in iron oxides, adsorbed Cl up to 5 meq. per 100 g. After removing the free iron oxides it adsorbed only 0.2 meq. He theorized that under condi­ tions, Cl ions replace OH ions associated with the free iron oxides.

Much of the work with NH4CI and other Cl bearing fert­ ilizers has been concerned with the ease with which-Cl is taken up by plant roots and its effect on uptake of other ions. Pettinger (39) reported that fertilizer Cl increased the Cl content of corn sap, the increase being proportional to the amount supplied by the fertilizer. He also noted that Cl from KC1 exerted a residual effect on Cl content of the sap 15 years after application. Kretschmer, et al. (32) working with a number of vegetable plants found that Cl ab­ sorption and accumulation was closely related to the quantity in the substrate. Substitution of Cl for nitrogen did not appear to be significant.

From the time of Van Itallie's classical work (50) and

continuing through some extensive studies by Bear and his associates (5 * 32, 50) several attempts have been made to

explain the differential uptake of plant nutrients on the basis of the ion-equivalent constancy in plants. According

to this concept the ratio of the sum of the cation milli-

equivalents to the anion milliequivalents in any one plant

species tends to be constant, regardless of variations in mineral supplies, if other environmental factors are stan­

dardized. Expressed as a simplified equation:

+ ^ + ^,a = constant N + Cl + S + P

From the equation it follows that an increase in absorption

of any one anion results in either the reduction in absorp­

tion of one or more other anions or an increase in uptake

of one or more cations.

It is readily apparent that a high Cl concentration in

the growth medium may significantly affect the uptake of N,

P, and S. Although this seems theoretically sound, experi­

mental evidence to support this theory is rather inconclusive (17.> 2j5j 32, 51)* Bear (5 ) found that topdressings of KC1

on field alfalfa caused a reduction in absorption of N, P,

and S. He also relates that substitution of Cl for these protein elements results in lower protein content of the

plant and, in many cases, a lower nutrient value. There is

other evidence that substitutions may occur (32), although

just as many investigations have shown no significant sub­

stitutions (4l, 51). Buchner (10) found that P or N con­

tent of the plant were not influenced by increased amounts

of Cl, but more Cl was taken up in the presence of NHj| than

NO3 . This increased amount of Cl uptake in the presence of

NH^-N has also been reported by other investigators (l, 5j

26).

Some substrate factors which were found to influence

high Cl uptake by tobacco include low contents of nitrogen,

potassium, and calcium, and high phosphorus and (42).

After studying the effects of CaCl2j and NagSO^ on the up­

take of ions from nutrient solutions by red kidney

beans, Gauch and Wadleigh (23) concluded that salt absorp­

tion involves an extremely complex series of interrelated

processes.

So diverse have been the results of ion uptake studies

that our knowledge on this subject is somewhat confused.

Mere analysis of plant tissue grown under various conditions

has not been sufficient to provide clear cut answers. More fundamental studies have become necessary. The mechanism, 10 or mechanisms, of ion uptake by plant roots has received much attention recently. Two excellent reviews concerning theories on this mechanism have appeared (20, 35).

Epstein and his associates have published several re­ cent papers on the subject of ion uptake by plant roots

(18, 20, 21, 33). The essential features of Epstein's theory are stated as follows:

...All indications are that many types of cells and tissues contain appreciable spaces which tend to be in equilibrium with solutions that bath them, so far as inorganic ions and certain other solutes are concerned. Penetration of ions into these "free" or "outer" spaces is reversible and non- metabolic, but may be prerequisite to subsequent active, metabolic transport. There is widespread agreement that this active transport involves "carriers". The functioning of these carriers is characterized by the attachment of the ions to carrier molecules, the movement of the resultant carrier-ion complex through some barrier interven­ ing between an "outer" and an "inner" space or phase, and subsequent discharge of the ions into the "inner" phase.

By using radioactive elements and excised roots Epstein found that Ca, Sr, and Ba compete forthe same binding sites oncarriers whereas Mg does not (21). He also found that halides interfere with each other (have same absorption sites) but that NO^ does not interfere with halide (18).

Prom these studies he reasons that ions recognized as being similar in chemical behavior tend to act as metabolic analogs in the absorption process and to compete for identical sites on the carriers affecting active ion transport. Somewhat in contrast, Butler (1 3 ), working with young wheat plants, found 11 that nitrate antagonized Cl uptake to a high degree * whereas, phosphate did not appear to do so at all. This suggested that H2PO21 may be absorbed by an entirely different mechanism.

The literature bearing on the subject of ammonium chloride to date may be summarized as follows:

(1) The primary consideration in the use of ammonium

chloride as a fertilizer is the effect of the

Cl ion.

(2) Small quantities of Cl may be essential to crop

growth but large quantities can be detrimental.

(3 ) The Cl ion is only slightly held by soil colloids,

does not accumulate in soils in humid climates,

andis readily absorbed by most plant roots.

(4) The accumulation of Cl in plant tissues does not

necessarily indicate the specific toxicity of Cl.

(5) It is suggested that the effect of Cl on the ab­

sorption of other anions may interfere with nitro­

gen, phosphorus, or sulfur nutrition. NATURE AND SCOPE OP THE INVESTIGATION

The possibility of using ammonium chloride as a ferti­ lizer was studied in two phases. First, a series of field experiments were designed to compare ammonium chloride with other sources of nitrogen for corn, oats, and wheat. Eva­ luations were made on the bases of field observations, grain yield, and anion absorption. The effects of ammonium chlo­ ride on soil chloride accumulation and pH were also consider­ ed.

Second, the important and controversial effect of chlo­ rides and other anions on anion uptake was studied using a solution culture technique. Eleven day old corn seedlings were used as an assay crop. .Preliminary studies revealed that these seedlings accumulated ions very rapidly from aerated solutions. Estimates of ion uptake and accumula­ tion were based on nutrients removed by the seedlings from the circumambient solutions.

12 I. GENERAL FIELD STUDIES

MATERIALS AND METHODS

Soil, Crops, and Fertilizers

The field experiments reported in this study were con­ ducted on Miami silt loam located on the Ohio State Univer­ sity. .farm at Columbus. Soils of the Miami catena were form­ ed from high lime till of the Late Wisconsin Age. The Miami silt loam is a Gray-Brown Podzolic soil developed under well- drained conditions. The soil in these particular experi­ ments was situated on slightly undulating topography where

both internal and external drainage was good. A further

description may be obtained from Conrey, et al. (15).

The variety of corn used in the corn experiments was

W64. It is a yellow dent hybrid commonly grown in Ohio.

In the small grain experiments, Seneca wheat and Clinton 59

oats were used.

Ordinary commercial brands of ammonium sulfate, ammonium

nitrate, and were used for fertilization.

Ammonium chloride was supplied by the Columbia-Southern Chemi­

cal Corporation. Where special mixed fertilizers were needed

they were prepared by mixing the materials in a portable con­

crete mixer. Either a standard grade of 0-20-20 was used as

a base and the desired nitrogen carriers were added or com­

pletely synthetic mixes were made by using various carriers

15 14 of N and K and commercial triple superphosphate as a phos­ phorus carrier. Finely sieved and air-dried Brookston soil was found to he an excellent filler were needed.

Sampling and Harvesting

All soil samples were obtained by using a soil auger.

Composite samples of each plot were obtained by making bor­ ings to a depth of 6-7 inches in at least five sites. The soils were placed in paper bags, air-dried in the laboratory, sieved through a 20 mesh sieve and stored in ice-cream car­ tons for future analyses.

Corn tissue samples were obtained by cutting a leaf from the same position on each of 10 stalks at random in each plot. When early samples were obtained the leaf above the basal leaf was taken. Samples during the "milk stage" of development were obtained by taking the leaf opposite the ear leaf. Oat and wheat tissue samples were obtained by selecting 20 plants at random from each plot just prior to heading. The plants were cut close to the ground with scissors. All green tissue was placed in paper bags, dried at 75° C in a forced air oven, ground in a Wiley mill to pass a 40 mesh screen, and stored in glass powder jars.

The two center rows from each corn plot were hand har­ vested. The total weight of ear corn and total ears per plot were recorded. Two rows of kernels from 10 ears selected at random from each plot were removed and placed 15 in moisture-proof bags for moisture determination. Moisture determinations were made on a moisture meter used by the

Ohio Seed Improvement Association. Total yields were cal­ culated on the basis of 15 per cent moisture. Wheat and oats were harvested by combine and the total weight of grain per plot was recorded. Moisture determinations were made by oven-drying at 105° C. and yields were calculated on a 15 per cent moisture basis.

Analytical Procedures

Gravimetric or volumetric methods for determining soil and plant chlorides_are laborious and time consuming. The application of the silver-silver chloride electrode to the electrometric determination of chlorides as suggested by

Best (6 ) and Snyder (45) offers the advantage of greater rapidity. With this method, determinations may be made directly on the soil or plant material suspension or decant­ ed extract. Turbidity is not a factor.

In this study the electrometric procedure was further modified and adapted to the use of the Beckman Model K Auto­ matic Titrator. Finding the end point by use of the galvano­ meter or pH meter as suggested by Best and Snyder can be quite tedious on samples that vary greatly in Cl content.

The Automatic Titrator eliminates this undesirable character­ istic .

The theory of the electrometric method is based on the 16 potential difference between the Ag-AgCl electrode and a reference electrode at the end point of the titration of Cl ions with AgNO-j. The potential of the Ag-AgCl electrode at

the end point of this titration may be calculated by the

following equation:

EAg = E°Ag “ H ln [cT-J

E°Ag ^as va-1-ue -0.2223 volts at 25° C. The value of Cl- at the end point in the titration is approximately 1 x

10“5 at 25° C., from the of AgCl in water. Solv­

ing the equation gives a value of -0.5181 volts at 25° C. A

saturated calomel electrode was used as a reference half­

cell instead of the quinhydrone electrode used by Best and

Snyder. Preliminary work showed that diffusion of KC1

through the salt bridge connection in the tip of the elect­

rode was very slow, yet significant, and caused drifting of

the end point. To remedy this, a KNO^ salt bridge was made

according to Piper (40) and attached to the side of the calo­

mel electrode (Figure 1). This assembly gave rapid response

and provided a sharp end point.

The saturated calomel half-cell has a potential of -0.2415

volts. The cell potential at the end point of the titration

may be calculated by subtracting the potential of the reduc­

tion electrode (calomel) from the potential of the oxidation

electrode (Ag-AgGl). This gives a value of 0.2766 volts or

approximately 277 millivolts. Therefore, by setting the mv 17

Stirrer

Delivery Tip Calomel

KNO

Fig. 1. Cell assembly used to determine chloride. 18 dial on the titrator to 277 mv it should be possible to auto­ matically titrate a sample of any Cl ion concentration to its end point. The validity of this procedure was checked by three different methods:

(1) The cell assembly was placed in 0.010 N KC1 and by

revolving the mv dial on the machine the potential

was found to be 100 m.v. By calculation., the

potential of Cl at this concentration should be

101 mv. Consequently, the actual potential agrees

favorably with the calculated potential.

(2) The number of ml. of 1/71 N AgNO-^ needed to titrate

or precipitate 15 ml. of 0.010 N KC1 was calculated

to be 10.64 ml. Several of these titrations were

made and the average volume used was 10.65 ml.

(5) A titration curve was run by adding small increments

of 1/71 N AgNO-j to 0.010 N KC1 and reading the

potential after each addition. The flex point was

found to be approximately 280 mv (Figure 2). This

is very close to the calculated end point potential

of 277 mv.

The procedure used to determine soil chlorides was as follows:

(1) Place 20 gm. of soil in 100 ml. of distilled water.

(2) Let stand approximately 4 hours, shake 15 minutes on

an Eberbach automatic shaker, and let stand 15 19

320

d 280 ■H •P

200

16 0

2 6 8 10 12 16 1/71 N AgN03, ml. Fig* 2. Potentiometrlc titration of 15 ml* of 0.0.1 H KG1 solution with 1/71 N Ag minutes to settle.

(5) Take a 50 ml. aliquot from the supernatent extract

and titrate on the automatic titrator with the

potential set at 280 mv.

Some preliminary work showed 100 per cent recovery of Cl from soil to which known amounts of KC1 had been added.

The procedure used for extracting chlorides from plant material was that suggested by Best (7). The plant extract was titrated electrometrically by use of the automatic titrator.

Soil pH was determined with a Beckman pH meter on a 1:5 soiliwater solution. Total nitrogen in the leaf tissue was determined by the Kjeldahl procedure using HgO as a catalyst.

Phosphorus in the plant material was determined by the phospho- vanado-molybdate method as suggested by Barton (5). Phos­ phorus was extracted from the plant material by dry ashing in the presence of magnesium acetate. Light transmission was determined by use of the Bausch and Lomb Spectronic 20 Colori­ meter set at 475 nyL. EXPERIMENTAL

Comparison of Ammonium Chloride and Ammonium Sulfate in Broadcast Applications for Continuous Corn

This experiment was designed to determine the effect of various rates of ammonium chloride on the growth and yield of corn, and on soil chloride content and soil pH.

Procedure. - Two nitrogen carriers, ammonium sulfate and ammonium chloride, were compared at four nitrogen levels,

0, 50, 100, and 200 pounds per acre. The experimental de­ sign was a randomized complete block with four replications.

The NH4CI and (NHii^SO^ was plowed down after being broad­ cast on the surface by use of the fertilizer attachment on a conventional grain drill. The drill was calibrated at all three rates for both fertilizers. After plowing, the soil was fitted by usual methods and corn was planted with a Ferguson two-row corn planter. The corn was row fertili­ zed at planting with 250 pounds of 0 -20-20 per acre.

The 0-20-20 fertilizer added about 40 pounds of Cl per acre to the soil. The 50, 100, and 200 pounds of nitrogen per acre in the form of NH4CI added about 155> 270, and 5^0 pounds of Cl per acre, respectively.

Results and Discussion. - The corn stand in 1955 was very poor and spotty. Dry weather following planting de­ layed germination and the corn and young seedlings were damaged by birds and rodents. The corn was replanted but

21 22 the replant did not mature properly. Final stand count ranged from 7*900 plants per acre in the plot with the poor­ est stand to 16,200 in the best stand plot.

Observations during germination and emergence revealed no differences or effects due to fertilizer treatment.

Leaf samples taken at two stages of growth showed no varia­ tion in dry weight production due to treatment. The corn yield data as shown in Table 1 was not significant.

An excellent corn stand was obtained with the 1956 planting. Again, no detectable differences between treat­ ments appeared during germination, emergence, or early growth. Near the end of the growing season the check plots showed foliar symptoms of nitrogen deficiencies but the number or size of developing corn ears did not appear to be affected. Nitrogen source did not have a significant effect on appearance or the number and size of corn ears. The 1956 corn yield data is shown in Table 1. The F-value for treat­ ments was not significant.

The accumulation of Cl in the soil under mid-western climatic conditions could be important. Effects of residual

Cl which might accumulate in the soil after repeated high applications of fertilizer must be considered. The soil in this experiment was sampled to a depth of 7 inches periodi­ cally over a two year period and the chloride content is shown in Table 2. These data reveal the extreme mobility of the chloride ion. The first samples were taken July 14, 23

Table 1. Effect of form of nitrogen and rate of broad­ cast application on yield of corn.

Yield, bushels per acre Treatment 1955 1956

Check, No N 85.6 94.0

NH4CI, 50 lb. N/A 00 ro 98.6

NH4CI, 100 lb. N/A 70.5 100.4

NH4CI, 200 lb. N/A 62.4 92.9

(NH4)2S04 , 50 lb. N/A 72.8 95.5

(NH4)2S04, 100 lb. N/A 73.6 97.6

(NHi[)2S04, 200 lb. N/A 80.3 97.5

E-values not significant at 0.05 per cent level. Table 2. Chloride content of Miami silt loam plow layer under different fertili­ zation treatments over a two year period.

Chloride content, ppm. 1955 1956 1957 Treatment July :14* Aug. 13 Apr. 13 June 11* July 16 Aug. 22 May 25

Check, No N 13 10 9 24 17 7 18

NH4CI, 50 lb. N/A 45 53 11 48 29 14 19

NH4CI, 100 lb. N/A 95 118 12 82 46 31 23

NH4CI, 200 lb. N/A 149 194 13 106 104 60 23

(NH4)2S04, 50 lb. N/A 15 7 7 25 20 7 18

(NH4)2S04, 100 lb. N/A 15 7 8 21 14 7 18

(NH4)2S04, 200 lb. N/A 15 7 7 17 16 7 18

*Fertilizer application date in 1955 was May 21. Fertilizer application date in 1956 was May 8 .

ro 4=- 1955 after fertilizer application on May 21. Only about 50 per cent of the added Cl was detected on the first sampl­ ing date. By August 15 the Cl content of the topsoil had

increased in the treatments where Cl was applied indicat­

ing an upward movement and accumulation due to water move­ ment and evaporation. During the summer of 1956 the Cl

content decreased steadily throughout the growing season.

Of most significance are the values for the April, 1956 and

May 1957 samples. These samples were taken after winter

leaching and before the spring fertilizer application. The

soil Cl content at these periods indicates that only very

slight amounts are retained against winter leaching in the

topsoil of Miami silt loam. Prom these and other findings

(57) it appears that Cl in soils having good internal

drainage will be rapidly dissipated, especially in a cli­

mate or season where rainfall greatly exceeds evaporation.

Although Cl is not synthesized into any organic com­

pounds in the plant, it is readily taken up from the sub­

strate by most plants. Table 5 shows the per cent Cl in

corn plants grown on soils of varying Cl content. These

values are based on leaf analysis. By comparing Tables 2

and 5 it can be seen that, in general, the Cl content of

the corn plant is directly proportional to the amount in

the soil. These values are in line with those reported by

Pettinger (59). Even the highest percentages found in the

plant, 1.4 and 1.2 per cent, are not in the range which 26

Table 3. Chloride content of corn plant leaves grown on Miami silt loam under different fertilization treatments.

Chloride content, per cent 1955 1956 Treatment July l4 Aug. 13 July 16 Aug. 22

Check, No N 0.82 0.81 1.10 0.59

NH^Cl, 50 lb. N/A 0.92 0.89 1.31 0.79

NH4CI, 100 lb. N/A 0.93 1.07 1.41 0.83

NH4CI, 200 lb. N/A 1.04 0.89 1.23 0.81

(NHj^gSO^, 50 lb. N/A 0.74 0.73 1.07 0.64

(NH2|)2S04, 100 lb. N/A 0.73 0.76 0.87 0.55

(NH^gSOjp 200 lb. N/A 0.75 0.77 0.88 0.62 27 wou.ld be considered as being critical.

Assuming the anion equivalent constancy theory to be applicable in this case, one might expect that an increase in chloride content of the plants would bring about an in­ crease in cation content or a decrease in other elements such as N and P which are taken up as anions. A decrease in N or P uptake of course would be the most critical.

Table 4 shows the N, P, and Cl content of corn leaves sampl­ ed August 22, 1956 when the corn was in late milk stage of growth. Prom these data there is no apparent evidence that uptake of Cl has affected the uptake of N or P. In similar experiments at the Ohio Agricultural Experiment Station at

Wooster it was found that increased Cl uptake had no signi­ ficant effects on uptake of any of the other major cations or anions.

The effect of large applications of NH4CI on soil pH

is a matter of practical importance, especially in soils where the rotation contains leguminous crops. It has been postulated by some European workers (51) that Cl depletes

the soil of calcium because of the very soluble CaCl2 which

is formed. Table 5 shows the pH of the soil in the check

treatment and the two treatments containing the highest

applications of NH4CI and (NHi|.)2S04 sampled through two crop­ ping seasons. Both fertilizer treatments caused increased

soil acidity, (NHi^SO^. slightly more than NH4CI. This was also true in the other treatments receiving lesser amounts 2 8

Table 4. Nitrogen and phosphorus content of corn leaves as compared to chloride content.

Per cent of dry w t . on August 22, 1956 Treatment Cl N P

Check, No N 0.59 5.42 0.25

NH4CI, 50 lb. N/A 0.79 3.66 0.26

NH4CI, 100 lb. N/A O .85 3.81 0.29

NH4CI, 200 lb. N/A 0.81 3.92 0.29

(NH4)2S04, 50 lb. N/A 0.64 3.89 0 .30

(NH4)2S04, 100 lb. N/A 0.55 3.78 0.26 (NH4)2S04, 200 lb. N/A 0.62 3.84 0.26 Table 5. Effect of high applications of ammonium chloride and ammonium sulfate on soil pH.

Soil pH 1955 1956 Treatment July 14 Aug. 13 April 14 June 11 July 16 Aug. 22

Check, No N 6.7 7.0 7.0 6.9 6.8 7.1

NH4CI, 200 lb. N/A 6.3 6.4 6.7 6.2 6.4 6.5 (NH4)2S04, 200 lb. N/A 6.1 6.4 6.6 6.3 6.1 6.1 30 of the fertilizers.

Comparison of Ammonium Chloride and Ammonium Sulfate in Row Applications for Corn

In the event that ammonium chloride could compete economically with ammonium sulfate as a source of nitrogen it would be available for use in mixed fertilizers. The use of NH4CI plus the conventional use of KC1 in mixed fertilizer would increase the Cl content of such a fertili­ zer to the point where it might be critical for use in row applications. In order to investigate such a possibility the following experiment was designed.

Procedure. - Two 10-10-10 fertilizers were prepared by using 0-20-20 as a base and adding NH4CI to the one and

(NH4 )2S04 to the other as nitrogen carriers. These two fertilizers, plus 0-10-10 containing no nitrogen, were applied to corn in the row at the time of planting at the rate of 300 pounds per acre. The new type Ferguson planter was used. The drill on this planter applies the fertili­ zer through a separate shoe just in front of and below the seed drop. The three fertilizer treatments were arranged in 5 replications of randomized complete blocks. At the rate of 300 pounds of fertilizer per acre the 0-20-20 and the 10-10-10 containing (NH4 )2S04 added approximately 30 pounds of Cl per acre, and the 10-10-10 containing NH4CI added about 115 pounds of Cl per acre. Results and Discussion. - There were no apparent effects of these three fertilizers on germination or stand count. There were some early differences in rate of growth and color between nitrogen and no nitrogen treatment, how­ ever, these differences were not so apparent by tasseling stage. Source of nitrogen (NH4CI or (NH4 )2S04) was of no significance as far as growth was concerned.

The more important data from this experiment are

summarized in Table 6. There were no significant differ­

ences in yield among the various treatments. As in the broadcast experiment, the chloride content of the leaves

varied directly with-the amount contained in the applied

fertilizer. The Cl content of the leaves was higher in

July than in August. This is probably due to the fact that

young plants are usually higher in mineral salts than older

ones, but may also be due to the high concentration of Cl

in- the root zone of the young plants because of the row

application. Also, since nitrogen was applied in the

ammonia form, the uptake of the NH^ ion might increase the

Cl uptake as reported by some workers (4, 9 , 25). This

might be especially true in cool, damp seasons which are

not conducive to rapid nitrification. . Table 6 . Effect of source of nitrogen on yield of corn and on chloride, nitrogen, and phosphorus content of the leaves.

Per cent in corn leaves, 1956 Yield Cl Cl N P Treatment bu./A July 16 Aug. 26 July 16 July 16

0-10-10 300 lbs./A 8i.o 0.72 0.41 3.04 0.22

10-10-10 (N from NH^Cl) 300 lbs./A 82.0 1.08 0.65 3.29 0.20

10-10-10 (N from ( N H ^ S O a,.) 300 lbs ./A 83.0 O .67 0.49 3.38 0.20

VIrv> 33 Comparison of Ammonium Chloride, Ammonium Nitrate and Ammonium Sulfate for Wheat when Applied at Planting

The following experiment was designed to evaluate the

effect of various nitrogen carrying fertilizers on early

growth and final grain yield of wheat.

Procedure. - Three 5-10-10 fertilizers were prepared

by using 0-20-20 as a base and adding the required amount

of either NH4CI, NH^NO^j or (NH^^SO^. These three fertili­

zers plus 0 -10-10 as a check made a total of four fertili­

zers. Each of the four fertilizer mixtures were applied at

the rates of 250 and 500 pounds per acre, making a total of

eight treatments. The design of the experiment was a split

plot with two rates of fertilizer as the main plots and the

four fertilizers as sub-plots. There were four replications

of each main plot. The fertilizer was applied at the time

of planting by the fertilizer attachment on the grain drill.

Results and Discussion. - Source of nitrogen had no

apparent effects on either germination or growth of the

young wheat in the fall and spring. After heading and just

prior to ripening, the plots receiving the 500 pound rate

of fertilizer showed slightly more vigor than those receiv­

ing 250 pounds per acre. This was especially true of those

containing nitrogen.

Some lodging occurred in nearly all plots in a diagon­

al pattern across the experimental area. In general, lodg­

ing appeared more frequently in the plots receiving the higher rates of nitrogen. This lodging is the probable reason for the smaller grain yields in the plots receiving the higher rate of fertilization, Table 7- It should be stressed, however, that any conclusions drawn from the yield data may be partially invalidated by lodging losses and bird damage prior to harvest. Statistical analysis showed no significant differences due to treatment. Ghosh and his associates (24) in India found that NH4CI was equally as effective as (NH^JgSO^ for -fertilization of wheat.

Because of the winter leaching of Cl from the soil, as shown in the first corn experiment, it is highly unlike­ ly that any spring damage to wheat could accrue from fall fertilization with NH4CI.

Comparison of Ammonium Chloride, Ammonium Nitrate, and Ammonium Sulfate for Wheat Applied as Spring Top Dressing

To prevent winter leaching losses of nitrogen and to provide a ready source of nitrogen for rapid spring growth, it is sometimes advantageous to apply nitrogen to winter wheat as a spring top dressing. This type of fertilizer application, since it is readily available to the young growing plants, would tend to accentuate differences be­ tween NE^jNO-j, (NH4 )2S04 and NH4CI as nitrogen carriers for spring top dressing of wheat. 35

Table 7 . Yield of wheat as affected by various sources of nitrogen and rates of fertilization.

Yieldj bu ./A Treatment 250 lb./A 500 lb./A

0-10-10 (No N) 32.5 29.8

5-10-10 ( (NH4)2S02|-N) 35.8 34.9

5-10-10 (NffyNO^-N) 33.9 32.8

5-10-10 (NH4CI-N) 36.6 33.1

F-value not significant. 36

Table 8 . Chloride content of wheat plants and grain yield as affected by various sources and rates of nitrogen.

Treatment Per cent Cl Yield May 30 bu ./A

Check, No N 0 .8 l 41.5

(NH4)2S04, 15 lb. N/A 0.80 38.0

NH4N0^, 15 lb. N/A 0.79 42.9

NH4CI, 151b. N/A 1.17 41.5

(NH4 )2SC>4 , 30 lb. N/A 0.76 42.3 NH4NO3 , 30 lb. N/A 0.82 36.6

NH4CI, 30 lb. N/A 1.27 42.9

P-value not significant for yield data. 37 Procedure. - Thirty-two plots of wheat were planted

in the fall of 1955 with a basic fertilizer application of

0-20-20 at the rate of 150 pounds per acre. Seven treat­ ments were applied to these plots in the spring of 1956.

They consisted of NH^Cl, NH4NOJ, and (NH^JgSO^, each at

the rate of 15 and 50 pounds of nitrogen per acre, and a

check plot with no nitrogen. The experimental design was

a split plot with rates of nitrogen as main plots and

fertilizer materials as sub-plots. There were four repli­

cations of each main plot. The nitrogen was applied by use

of the fertilizer attachment on a conventional grain drill.

Results and Discussion. - The data in Table 8 show

that neither rate nor source of nitrogen had a significant

effect on the growth or yield of wheat. The data also show

that although the Cl content of the plants increased this

increase did not influence yield.

It should be pointed out that wheat yields on the plots

receiving spring top dressing of nitrogen were about 7 bu./A

higher than those reported in the previous experiment where

all fertilizer was applied in the fall. This occurred in

spite of the fact that there was no apparent response to

nitrogen applied in the spring, Table 8 . It was observed,

however, that much less lodging occurred in the plots re­

ceiving spring applications of nitrogen, even though they

were on the same soil type and adjacent to the experiment

receiving all fertilization in the fall. This difference 38 in lodging tendency is difficult to explain.

Comparison of Ammonium Chloride, Ammonium Nitrate, and Ammonium Sulfate for Oats when Applied at Planting

Procedure. - Three 10-10-10 fertilizers were prepared by using 0 -20-20 as a base and adding the required amounts of either NHi|Cl, (NH^JgSO^, or NH^NO^. These three fert­ ilizers, plus 0 -10-10 as a check, were applied to oats at rates of 250 and 500 pounds per acre. The eight treatments were applied in four replications of a split plot design.

Rates of fertilizer were the main plots and fertilizer materials were the sub-plot treatments. The oats were planted April 20, by means of a grain drill and the fert­ ilizer was applied at that time.

Results and Discussion. - During early growth the oats responded well to nitrogen treatments. Both rates of nitro­ gen improved the color and rate of growth. There was no apparent difference in early growth between plots receiv­ ing the different sources of nitrogen.

The Cl content of the soil on June 11, when the oats were heading, and July 27, just after harvest, are shown in

Table 9. These data show that the Cl content of the soil was higher in the plots receiving nitrogen as NH^Cl in all but the 500 pounds per acre treatment at the June 11 samp­ ling period. The reason for this cannot be fully explained, especially since the concentration was up on July 2 7 . The increase in soil Cl content between June 11 and July 27 in Table 9. Chloride content of soil, chloride and nitrogen content of oat plants, and yield of oats as affected by various nitrogen carriers and rates of application.

Cl content of soil, ppm1 Per cent in plants, June 11 Yield Treatment June 11 July 27 Cl N bu./A

250 lb./A

0-10-10, Check 15 13 0.83 2.23 53.0

10-10-10, (NHi^SO^-N . 13 15 0.61 2.32 54.1

10-10-10, NH^NO^-N 1? 13 0.60 2.61 56.3

10-10-10, NH4CI-N 20 23 1.33 2.46 42.3

500 lb./A

0 -10-10, check 18 19 0.77 2.40 59.2

10-10-10, (NH4 )2S04-N 16 16 0.94 2.68 39.5

10-10-10, NlfyNO^-N 14 19 0.96 2.64 52.3

10-10-10, NH4CI-N 16 35 2.00 2.55 46.4

P-value not significant for yield data.

VO 40 this treatment and some others (Table 9) may have been partly due to upward movement of Cl with soil moisture dur­ ing this summer period. Another possibility would be the release of Cl to the soil by plants near the end of matur­ ity. This may occur either by diffusion or exchange through the cell walls or by actual leaf drop-off from the plants to the soil surface and subsequent and leaching of this material.

Also shown in Table 9 are the percentages of Cl and N in the plant material on June 11. The amount of chloride in the oats was proportional to the amount added in the fertilizer, the highest value of 2.0 per cent Cl is fairly high for plant material. The per cent nitrogen seemed to be relatively constant and independent of the amount of Cl in the material.

There were no significant differences in yield due to treatments. However, the data was somewhat inconclusive because of irregular lodging and bird damage in the plots.

Most of the variation in yield was due to lodging losses.

Lodging did occur to a greater extent in the high nitrogen treatments and that was reflected by lower yields in some of these treatments, Table 9. SUMMARY AND CONCLUSIONS

Ammonium chloride as a source of nitrogen for field crops was compared with other common nitrogen sources in a series of field studies. Evaluations were made on the basis of germination and general growth; chloride, nitrogen, and phosphorus content of the leaves; grain yield; chlo­ ride accumulation in the soil; and changes in soil pH. The following conclusions may be drawn:

1. Germination and growth of corn, wheat, and oats

fertilized with ammonium chloride were not differ­

ent from that fertilized with either ammonium sul­

fate or ammonium nitrate.

2. Chloride content of the plants varied directly as

the amount supplied in the fertilizer, however,

increased chloride content of the plant had no

significant effects on per cent of nitrogen or

phosphorus in the plant.

3. There were no significant differences in yield of

corn, oats, and wheat where ammonium chloride was

compared with other sources of nitrogen. The

yield results, however, were somewhat inconclusive

because of poor stand of corn and lodging losses

and bird damage in the small grain.

4. The amount of chloride accumulating in the top-

41 soil after two years of heavy fertilization with ammonium chloride was insignificant. Depletion of chloride from the soil was seasonal * remaining static during summer months and mainly disappearing over winter.

Both ammonium chloride and ammonium sulfate in­ creased the soil acidity. II. NUTRIENT ION UPTAKE STUDIES

MATERIALS AND METHODS

Technique of Study

One of the most controversial phases of chloride effects in plant nutrition is that of anion competition during the process of ion absorption. In other words, could one anion, being in excess in the substrate, compete with or substitute for another anion during uptake? And, if so, could this anion, after being accumulated in the plant, be exchanged for some other anion in the substrate?

If it could be shown that Cl does not directly interfere with uptake of other anions or that it could be exchanged

by the plant for other anions outside the plant then its

detrimental effects could be attributed primarily to in­

ternal physiological effects.

The existence and extent of ion competition is diffi­

cult to resolve. It is somewhat presumptous to conclude

that competition,per se, has occurred solely on the basis

of plant analysis at the end of a growing season. Adverse

physiological effects caused by increased uptake of one

ion might limit the uptake of another ion. For instance,

it has been postulated (5) that increased chloride uptake

interferes with organic acid synthesis and subsequent amino

acid and protein synthesis. The resulting decreased nitro- 44 gen content in the plant would thus appear to have been anion competition.

Because of the fundamental importance of ion uptake re­ lationships, a need exists for new methods of study. Pre­ vious studies have been conducted primarily with excised root systems. The use of excised roots is prompted partly by convenience and partly by convention. In this study, an effort was made to utilize entire plants in short-time absorption studies. This entire plant approach would more nearly simulate natural conditions and the short-time ab­ sorption period would eliminate many physiological variables.

In fundamental studies such as this, it is necessary to produce for each experiment a large number of uniform plants (absorbing systems) with certain desirable character­ istics resulting from conditions imposed during the pre­

liminary growth period. Conditions which facilitate rapid

salt absorption include: adequate oxygen supply, low ini­

tial salt content of plants, source of carbohydrate and,

obviously, a salt supply. These conditions are further

elaborated upon by Hoagland and Broyer (8 , 28). In general,

the plants should be in a state of high metabolic activity

and capable of carrying on further respiration.

The use of 3 week old barley plants as suggested by

Hoagland and Broyer (28) at first seemed ideal. However,

difficulties were encountered in obtaining uniform, healthy plants. Some attention was then directed to the use of 45 corn seedlings. Preliminary work revealed that corn germinated in silica sand in the greenhouse and watered with tap water grew very rapidly unitl about the twelfth day when nitrogen and other nutrient ion deficiences first began to show. At twelve days the plants were eight inches high with well developed fibrous roots and a low salt con­

tent .

Prom these preliminary observations the following

technique for studying nutrient ion uptake was developed.

1. Twenty corn seeds were planted in each of several

2 -gallon glazed pots about 2/5 filled with pure

silica sand. These pots had drain holes in the

bottom so that over-watering would not result in

anaerobic conditions.

2. The pots were watered as needed, depending on eva­

poration and transpiration losses during the

germination and early growth phase.

5. On the eleventh day the seedlings were removed from-

the pots and the roots washed free of sand with a

stream of water.

4. The seedlings were selected for uniformity and

divided at random into groups of six plants,

Figure 5> to be used for the absorption studies.

5. Each group of 6 plants was placed in a 1-quart,

wide-mouth mason jar containing 500 ml. of the

solution under study. It was not necessary to 46

support the plants beyond the support provided by

the mouth of the jar.

6 . The solutions were aerated by use of the apparatus

shown in Figure 4. Air from the manifold was dis­

tributed through sections of tygon tubing* each

containing a 2 -inch piece of glass capillary tube

to help equalize the air pressure in the system.

The actual aerator in the solution consisted of an

L-shaped piece of glass tubing terminated by a

1-inch piece of tygon tubing which had been pierced

several times with a teasing needle and the end

plugged with a piece of glass rod. This aeration

apparatus proved to be very satisfactory.

7. The amount of salt accumulated during the absorp­

tion period was determined by analyzing the sub­

strate before and after absorption.

8 . Previous work (28) has shown that root systems ab­

sorb much more rapidly in the presence of a readily

available carbohydrate source which facilitates re­

spiration. To supply this* 5 ml. of 0.1 per cent

glucose solution was added to each jar.

Analytical Methods

Chloride in the nutrient solution was determined by a modification of the electrometric method as suggested by

Best (7) and as outlined earlier in this text. Nitrate 47

JUL • 57

Fig. 3>. Eleven-day old corn seedlings grown in silica sand.

Fig. 4. System for aeration of corn seedlings during uptake studies. nitrogen was determined by the Kjeldahl procedure by re­ ducing the nitrate to ammonia with Devarda's alloy (40).

Phosphorus was determined by the phospho-vanado-molybdat mathod (3) using a Bausch and Lomb Spectronic 20 Colori­ meter set at 475 m ^ . Potassium was determined on the

Beckman Model DU Spectrophotometer. EXPERIMENTAL

Optimum Time and Solution Concentration for Accumulation of KC1 by Corn Seedlings

Procedure. - Although there is much work in the litera­ ture concerning optimum solution concentration and minimum time required for accumulation of salts by excised roots

(8, 28, 31), very little is known about this subject as re­ gards whole plants. Prior to making the study of anion competition, preliminary studies were conducted to deter­ mine optimum solution concentration and absorption time.

Potassium chloride was used as a single substrate salt in distilled water. Solution concentrations of 0.005 M, 0.02

M, and 0.05 M and absorption times of 12 hours, 36 hours, and 60 hours were arranged in a 3 x 3 factorial with 3 re­ plications. Corn seedlings were grown and prepared as de­ scribed under "materials and methods." All work was con­ ducted in a shaded greenhouse during the month of June.

Results and Discussion. - The results of this experi­ ment are shown in Table 10. Except for the 0.05 M solution, the uptake of K exceeded that of Cl in all cases. Hoagland

(27) using excised roots in KBR solution also showed that

K absorption exceeded Br absorption by about 75 pe^ cent.

This increased K absorption over Cl is also reflected by the drop in pH during absorption, Table 11. The increased uptake of K ions was evidently accompanied by movement of

49 50

Table 10. Effect of absorption time and solution concen­ tration on accumulation of KC1 by corn seedlings.

Solution concentration Absorption 0.005 M 0.02 M 0.05 M time K Cl K Cl K Cl

Mea,.. absorbed per liter solution

12 hr. 1.22 0.76 2.90 2.27 2.82 4.19 56 hr. 1.54 0.82 4.68 2.99 5.84 4.65 60 hr. 1.91 1.25 4.09 2.55 5.84 4.56

L.S.D. (P = 0.05) = 1.28 for Cl L.S.D. (P = 0.05) = 1.19 for K

Table 11. Change in pH of KC1 solution after absorption by corn seedlings for different periods of time.

Absorption KOI concentration time 0.005 M 0.02 M 0.05 M

pH of solution

0 hr. 6.1 6.0 6.0 12 hr. 4.2 4.0 4.0 56 hr. 5.7 5.6 5.8 60 hr. 5-5 5.5 5.4 51

H Ions in the opposite direction through the uptake mechan­ ism.

An increase in solution concentration caused signifi­ cant increases in Cl uptake at all three absorption times.

Uptake of Cl did not increase significantly with absorp­ tion time above 12 hours. An increase in solution concen­ tration caused significant increases in K uptake only be­ tween the 0.005 M and 0.02 M concentrations. Uptake of K increased significantly with absorption time only in the

0.02 M solution up to 56 hours. Based on these results a solution concentration of 0.05 M and a 56 hour absorption period were selected as being suitable for future uptake studies.

Relative Competitive Effects of Chloride, Nitrate, and Phosphate Anions on Their Mutual Uptake by Corn Seedlings

The objective of this experiment was to determine the extent of anion competition during ion uptake by corn seed­ lings. The effect of one ion on the uptake of another is difficult to study. For example, varying the concentration of one anion, such as chloride, simultaneously varies the concentration of the associated cation of the chloride salt. This affects both the anion and cation concentration in the nutrient solution, changes the ostmotic pressure of the solution, and complicates any conclusions which might be drawn from variations in ion uptake.

The approach used in this study was similar to that 52 used to study the well known complementary ion effects in soil. Solutions containing a single cation species and two anion species as complementary ions in varying concen­ trations were used as uptake media. By plotting uptake curves for all anion combinations the relative competitive effects of any two anions on the uptake of another could be determined. If the anions could be shown to differ in their effects then the conclusion that anion competition occurs would be justified.

Procedure. - Eleven-day old corn seedlings were placed in 500 ml. of each of 13 solutions shown in Table 12. All solutions were 0.03 M with potassium being the only cation in all solutions and chloride, nitrate, and phosphate rang­ ing from zero to 0.03 M as indicated. Each of the 13 treat­ ments occurred in three replications. The solutions were analyzed before and after a 36 hour absorption period to determine the amount of each ion taken up by the plants.

Results and Discussion. - During the absorption period, some leaf tip burn or scalding appeared in the solutions containing the higher concentration of HgPO^ . There was also a slight yellowing of lower leaves throughout the treatments. Otherwise the corn seedlings remained in a healthy condition.

The uptake of various combinations of the salts of

KC1, KNO-^, and KH2PO4 is shown in Table 12. Since the con­ centration of potassium was constant throughout the series 53 of treatments, any variations in amount absorbed should be due to the influence of the associated anion or anions.

The amount of K absorbed was quite variable and does not seem to form a definite pattern. In the one-salt solutions in Table 12 most K was absorbed in the presence of NO-^, treatment E, least in the presence of HgPO^, treatment I, and the Cl salt, treatment A, was intermediate. In general, there was an increase in K absorption with an increase in anion absorption.

The relative effects of chloride, nitrate and phos­ phate on absorption may be likened to the complementary ion effect in soil. For example, how does the presence of chloride as compared to phosphate affect the uptake of nitrate at varying concentrations? The actual amount of each anion absorbed in the presence of the other, express­ ed as milliequivalents absorbed per liter of solution are shown in Table 12. These relationships are also portrayed graphically in Figures 5* 6 , and 7*

The uptake of nitrate was greater in the presence of phosphate than in the presence of chloride as shown in

Figure 5. Whether this was due to a stimulation of the up­ take mechanism by phosphate ions or competition with nitrate by the chloride cannot be definitely concluded, however, the latter is a more likely explanation. According to Ep­ stein (18) competition could not occur at the absorption sites since the sites are either chemically or positionally Table 12. Uptake of various combinations of potassium salts by corn seedlings.

Solution molarity before Meq. absorbed per liter absorption solution Solution K+ Cl~ NO^ h2po^ K+ Cl~ NOj H2P04

A 0.030 0.030 - - 2.36 2.58 --

B 0.030 0.020 0.010 - 1.07 1.55 2.2 -

C 0.030 0.015 0.015 - 2.36 1.36 3.0 -

D 0.030 0.010 0.020 - 3.20 0.93 3.4 -

E 0.030 - 0.030 - 4.69 - 3.6 -

F 0.030 0.020 - 0.010 2.13 1.78 - 1 .6l

G 0.030 0.015 - 0.015 2.56 1.41 - 1.61

H 0.030 0.010 - 0.020 2.56 1.08 - 1.07

I 0.030 - - 0.030 2.13 - - 1.61

J 0.030 - 0.020 0.010 2.56 - 5.0 1.36

K 0.030 - 0.015 0.015 3.00 - 5.4 1.74

L 0.030 - 0.010 0.020 2.56 - 4.4 1.74

M 0.030 0.010 0.010 0.010 3.41 0.77 5.0 1.89 VJl 4=- i.5 Belativeeffects ofthe complementary 5*Pig.ions NO “ ahsorfoed, meq./liter solution 0orCl" N HoP0 l orCl“ HoPO corn seeallngs. iT on on theuptake of NO “hy Solution concentration 0.015 0.015

*‘- H .Cl” complementaryion 2 ion P ascomplementary 0 i), as ^

55 56

HgPO^” as complementary Ion NO ” as complementary ^ Ion g

o to

>d U o m

d

0.03 m c r 0*015 0 M N03“ or H2P02,” 0,015 Solution concentration Fig, 6, Belatlve effects of the complementary Ions N0 o“ or H5P0^“ on the uptake of 01“ by corn Bt “ " 57 — ■— NO^- as complementary Ion 01“ as complementary Ion

•Hg 5

H O CQ u ■p© ■H p H a* 3 i >o © 2 ■go 03

'g 1 V CM W N.V

0.0-3 HgPOi," 0.015 0 0 M 01“ or NO- 0.015 0.03 Solution concentration Fig. 7 . Belatlve effects of the complementary lonB Cl- or N0o“ on the uptake of HgPO]T by c o m seedlings. different for different ions. The possibility still exists that competition may occur as a kind of overall, electrical equilibrium condition. For example, assume a room is being filled by people through two entrances, one for ladies and one for men. The seats are being filled at random as soon as members of either sex enter. Further assume that the entrance for ladies is much larger and they are being ad­ mitted much more rapidly. As soon as the room is filled and there are no more seats available there will be more

ladies than men, not because of competition at the entrances but because one sex could enter more rapidly at a different site. This same condition may hold true with ion entrance

into plants. It is known that chloride enters the plant

very readily and by so doing it may satisfy the electri­

cal balance in the plant to such an extent that the potent­

ial for absorption of other anions is greatly diminished.

This reasoning is somewhat in line with the anion equiva­

lents constancy theory.

Figure 6 shows that slightly more chloride was taken

up in the presence of phosphate than in the presence of

nitrate. This further suggests that some type of competi­

tion occurred between nitrate and chloride. It may be not­

ed in Figure 6 that the uptake of chloride was directly

proportional to the concentration of chloride in the nut­

rient solution. This was also shown in Table 10. 59

Of those solutions studied, uptake of phosphate seemed to he more or less constant regardless of phosphate con­ centration or the complementary anion, Figure 7* This agrees with Butler's suggestion (13) that phosphate may be

taken up by a different mechanism. It also indicates that

it would be highly improbable that chloride concentration in the soil would be of such magnitude as to cause decreas­

ed phosphate uptake.

It is generally believed that plants do not accumulate phosphate to any extent and this nutrient is not normally associated with luxury consumption in the field. However,

the amount of phosphate accumulated by the plants in this

experiment was quite high.

Exchange of Plant Chlorides with Ions in the Outside Solution

It has been demonstrated that plants absorb chloride

very readily both from the soil and from nutrient solutions.

Since chloride is not synthesized into organic compounds but remains in the plant in inorganic form, it would be of

interest to know to what extent it is reversible with the

substrate. If chloride, after entering the plant, were re­

versible or exchangeable with ions in the outside media

then any detrimental effects arising from its presence would

be minimized. An experiment was designed to study this

possibility. Procedure. - Thirty groups of corn seedlings were placed in 0.03 M KC1 solution for 36 hours as described under methods and materials. At the end of this period the seedlings had absorbed an average of 3.1 meq. of chloride per liter of solution. The seedlings were removed from the

KC1, washed in distilled water and placed in varying con­ centrations of KNO-^. The concentrations used were 0.030 M,

0.0225 M, 0.015 M, 0.0075 M and zero or distilled water.

Three replications of these five treatments were aerated as usual and another identical series was merely placed in

the solutions and not aerated in order to determine what

effect respiration had on ion loss or exchange. The plants

in both the aerated and non-aerated KNO^ solutions were allowed an absorption or exchange period of 36 hours. They were then removed and the solutions were analyzed for chlo­

ride and nitrate content.

Results and Discussion. - At the end of the second ab­

sorption period the plants in the non-aerated solutions were

not visibly affected by lack of oxygen. Less nitrate was

taken up in the non-aerated solutions than in the aerated

solutions, especially in the higher concentrations, Table 13.

Aeration had little effect on the loss of chloride from the

seedlings.

The plants lost about 50 per cent less chloride to

distilled water than to solutions containing nitrate. With

the exception of zero nitrate concentration, the plants lost the same amount of chloride to the solution regardless of the nitrate concentration. The total amount of chloride lost to distilled water was about 10 per cent of that pre­ viously absorbed while that lost to solutions containing nitrate was about 20 per cent of the amount present in the plants.

Prom these data it appears that chloride present in the plant is at least partially in equilibrium with the outside solution. The chloride lost to the distilled water may be comparable to that amount occupying the "apparent free space" of the plants as proposed by Epstein (20).

This'amount is assumed to be freely diffusable with the outside solution. An additional 10 per cent seems to be readily exchangeable with ions in the outside solution.

The status of the remaining 80 per cent in the plant is not known. 62

Table 13. The effects of aeration and nitrate concentra­ tion of the substrate on uptake of nitrate and loss of chloride by corn seedlings.

NO-3 absorbed Cl lost NO5 conc. meq./l. solution meq./l. solution of substrate Aerated Non-aerated Aerated Non-aerated

0 0.0 0.0 0.35 0.26

0.0075 M 1.7 1.5 0.62 0.51

0.0150 M 2.6 1.7 0.54 0.57

0.0225 M 3.1 2.3 0.58 0.54

0.030 M 3.5 2.3 0.56 0.54 SUMMARY AND CONCLUSIONS

In order to arrive at the more fundamental relation­ ships governing chloride ion effects a technique was developed wherby eleven-day old corn seedlings were used as an assay crop for short time absorption studies in the greenhouse. Short-time absorption studies are advantage­ ous because many growth variables associated with the physiology of the plant are essentially eliminated. This type of study may also be adapted to the soil to determine the availability of various nutrient ions. Preliminary studies in nutrient solutions gave the following results:

1. Eleven-day old corn seedlings absorbed ions from

aerated solutions very rapidly and in measurable

quantities.

2. More nitrate was taken up by the plants in the

presence of phosphate than in the presence of

chloride.

3. Slightly more chloride was taken up in the pre­

sence of phosphate than in the presence of nitrate.

4. The amount of phosphate taken up was independent of

phosphate concentration in the substrate or the pre

sence of a complementary anion.

5. Approximately 10 per cent of the chloride previous­

ly absorbed by corn seedlings was lost to distill­

ed water in 36 hours. 64

6 . Approximately 20 per cent of the chloride previous­

ly absorbed was lost to solutions containing vari­

ous nitrate concentrations. The amount of chloride

lost was constant regardless of nitrate concentra­

tion, nitrate uptake, or aeration of the solution.

In general summary, there appears to be no great problem associated with the use of ammonium chloride as a source of nitrogen for grain crops in this climate. Even though chloride is accumulated in plants, there is little evidence

that its interference with absorption of other essential anions is of any importance. LITERATURE CITED

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65 66

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51. Weishut, P. T. 1954 Ammonium chloride as a fertilizer (Lit. Rev.). Research Rept. No. BR7844. AUTOBIOGRAPHY

I, Robert Woodson Teater, was born in Nicholasville,

Kentucky, February 27j 1927. I received my secondary school education in the public schools of Jessamine County,

Kentucky, and my undergraduate training at the University of Kentucky, which granted me the degree Bachelor of

Science in General Agi?iculture in 1951. After serving two years in the United States Infantry in this country and Korea I entered The Ohio State University as Research

Assistant in the Department of Agronomy in 1953. From this University I received the degree Master of Science in 1955- I held the position of Research Assistant in the Department of Agronomy at The Ohio State University for two additional years while completing the requirements for the degree Doctor of Philosophy.

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