EFFECTS of BORON and SODIUM TOXICITY on the GROWTH of LEAFY AMARANTH (Amaranthus Cruentus)

nd 2 World Irrigation Forum W.1.5.01 6-8 November 2016, Chiang Mai, Thailand

EFFECTS OF BORON AND SODIUM TOXICITY ON THE GROWTH OF LEAFY AMARANTH (Amaranthus cruentus)

Adeniran, K.A.1, Amodu, M.F.2, and Adelodun, B.3

ABSTRACT

Boron and sodium toxicity on the growth and yield of leafy amaranth (Amaranthus cruentus) crop were studied using 4 x 2 factorial in Randomized Complete Block Design (RCBD), replicated thrice. The treatments included: no-Boric acid and no- NaCl salts, 5mmol/cm of Boric acid and 20mmhos/cm of Sodium Chloride, 15mmol/cm of Boric acid and 40mmol/cm of NaCl and 25mmhos/cm of Boric acid and 60mmol/cm of NaCl. Interactions between treatments were also considered. Equal amount of irrigation water was applied manually and the same level of fertilizer was imposed on the treatments arranged in pots. Plant height, numbers of leaves, leaf area, root length and plant weight were determined and statistically analyzed. The results show that amaranth plant was affected by simultaneous salinity and boron toxicity. Plots treated with minimum toxicity; 5mmol/cm of Boric acid [B(OH)3] and 20mmol/cm of NaCl (B₃NaCl₁) recorded the highest fresh and dry matter accumulation on the seventh week, 52.6g and 7g respectively, while treatment with Boric acid [B(OH)3] and 40mmol/cm of NaCl (B₃NaCl3) recorded the lowest fresh and dry matter accumulation of 7.8g and 1.7g respectively for the same period. Plots treated with 5mmol/cm of Boric acid [B(OH)3] and 20mmol/cm of NaCl recorded the lowest values of 26.8cm, 16.1cm, and 38.5cm2 for plant height, root growth and leaf area respectively. The highest plant height and leaf area values of 23.3cm and 2 102cm was recorded for plants treated with B₃NaCl1 during the eight week of growth. The results show that the low sodium chloride combined with moderate boron acid concentration favours crop growth.

Keywords: Boron, sodium toxicity, Amaranthus cruentus, Boric acid and Sodium Chloride.

1. INTRODUCTION

Salinity effecis on plants may be osmotic effects, specific-ion toxicity and/or nutritional disorders (Läuchli and Epstein, 1990). Plants undergo characteristic changes from the time salinity stress is imposed until they reach maturity (Munns, 2002). Boron (B) is a member of the subgroup III of metalloids and has intermediate properties between metals and nonmetals (Marschner, 1995). Tanaka and Fujiwara (2007) reported that Boron is essential for plant growth and its availability in soil and irrigation water is an important determinant of agricultural production. In soil solution, Shorrocks (1997) reported that Boron exists primarily as boric acid [B(OH)3], which is leached out under high rainfall causing B deficiency. But, under low rainfall, Boron accumulates to toxic levels for the plant (Reid, 2007), which is common in arid and semiarid regions with high-boron groundwater (Tanaka and Fujiwara, 2007). Saline 2 - 2- - irrigation water contains dissolved SO4 , CO3 , and HCO3 of Ca and Mg. When these are in excess, plant roots cannot draw nutrient solution from the soil. Na toxicity has the opposite effect of salinity on soils. The physical processes associated with

1 Associate Professor, Department of Agricultural and Biosystems Engineering, University of Ilorin, P.M.B. 1515, Ilorin, Kwara State, Nigeria. *E-mail: [email protected]. 2 Researcher: [email protected]. 3 Researcher: [email protected].

1 nd 2 World Irrigation Forum W.1.5.01 6-8 November 2016, Chiang Mai, Thailand high Na content are soil dispersion and clay platelet and aggregate swelling. Soil dispersion causes clay particles to plug soil pores, resulting in reduced soil permeability. When such soils are repeatedly wetted and dried, it then reforms and solidifies into almost cement-like substance with little or no structure (Henderson, 1981). The objective of this study was to determine the effects of B and Na toxicity on the growth and yield of leafy amaranth (Amaranthus cruentus).

2. MATERIALS AND METHOD

2.1 Description of the Study Site

The pot experiment was done using sandy-clay loam soil in the experimental plot of the Department of Agricultural and Biosystems Engineering, University of Ilorin, Ilorin, Nigeria, from 30th April, 2012 to 6th July, 2012. The study site is located on latitude 08° 30’N and longitude 04° 35’E with an elevation of about 340m amsl, and measures 22.5 m2. Ilorin falls into the Southern Guinea Savannah Ecological Zone of Nigeria with annual precipitation of about 1300mm, having a bimodal distribution. The rainy season starts around March, with a short dry spell in July. The long dry spell begins in November and ends in March.

2.2 Layout and Instrumentation

Rain shelter was constructed using bamboo posts and transparent polythene roof slanting in one direction, to shield crops from rainfall and from direct sunlight. The pots were filled with air-dried soil weighing 10kg of sandy clay loam soil including the pot. The filled pots were then spaced 10cm × 10cm along and within the row between pot of same treatment and 20cm when separating various treatment and their replicates.

2.3 Experimental Design

The study was conducted using 4 x 2 factorial in a Randomized Complete Block Design, replicated thrice. The pots (Figure 1) were grouped under four categories of treatment, namely, 1, 2, 3 and 4; all receiving the same amount of irrigation water applied manually. Treatment 1 is the control, while treatment 2, 3 and 4 were subjected to varied treatment levels. The treatments are as follows:

1. Control; No-Boron and No-Sodium-ion treatment.

2. Minimum toxicity; 5mmol/cm Boric acid [B(OH)3] and 20mmol/cm NaCl.

3. Moderate toxicity; 15mmol/cm Boric acid [B(OH)3] and 40mmol/cm NaCl.

4. High toxicity; 25mmol/cm Boric acid [B(OH)3] and 60mmol/cm NaCl.

Interactions between the treatments were also considered. These treatments were imposed four weeks after germination.

2.4 Soil physical properties

Soil physical properties, including the soil water properties were determined by adopting standard methods.

2.5 Crop Management

Amaranth seed (24 g) was mixed with 200g of 2mm sieved air dried soil and the mixture was broadcast. The seed germinated within 4-6 days and thinning was done

2 nd 2 World Irrigation Forum W.1.5.01 6-8 November 2016, Chiang Mai, Thailand

2 weeks after planting to three plants per bucket. When the plant height was about 6cm, NPK (15-15-15) fertilizer was added by adopting the optimal rate of 90 kg/ha as recommended by Ojo (1998). The application was 2.0 g/plant i.e. 6g/bucket for the stand of three plants. Weeding was done manually. Plant samples were selected at random on weekly basis to determine plant height, leaf area, root length, number of leaves, and plant weight (fresh and dry matter) for all the treatments. All measurements were done following standard procedures.

Figure 1: Pot arrangement

3. RESULTS

3.1 Soil physical and weather conditions

Table 1 shows that the soil contains 74.6% Sand, 23.2% Clay and 2.2% Silt, and texturally, the soil is Sandy clay loam. The bulk density of the soil was 1.45g/cm3. The moisture content of the soil was determined by gravimetric method. Soil field capacity and irrigation frequency were calculated from the moisture content, depth and bulk density. Table 1 indicates that high temperatures prevailed during the study with humid conditions in the last three weeks of study.

Table 1. Average meteorological conditions during the period of study

Temperature Temperature inside Relative Relative outside the rain Humidity Humidity the rain shelter Rainfall Week shelter o inside the outside the o ( C) (mm) ( C) rain shelter rain shelter Max Min Max Min (%) (%) 1 38.3 25.2 32.5 21.6 64.6 69.5 Nil 2 38.4 25.3 32.7 22.0 62.4 67.5 Nil 3 37.8 25.6 31.5 21.7 63.8 68.2 Nil 4 36.7 25.6 31.2 21.8 64.2 68.6 Nil 5 37.4 22.6 31.6 21.6 64.8 69.3 Nil 6 35.5 22.1 30.5 21.2 65.6 69.8 20.5 7 32.7 23.2 30.2 21.1 64.5 71.2 32.6 8 34.8 23.1 31.3 21.4 74.5 76.5 35.4

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3.2 Soil chemical properties

The chemical analysis from the soil sample before imposing the treatments is given in Table 2, which shows that the soil is acidic and high in organic matter.

Table 2. Chemical properties of experimental soil

Soil property Initial quantity Soil property Initial quantity CEC (Meq / 100g pH in water (1:1) 5.6 1.39 soil) pH in KCl 4.75 Ca2+ 5.91 Organic matter (%) 112 Mg2+ 7.69 Total Nitrogen 1.40 Na+ 2.75 Available P (mg/kg) 1.83 K+ 2.60 ESP (%) 11.98

3.3 Plant growth parameters

3.3.1 Fresh matter accumulation

Figures 2 and 3 show that initially there was a gradual increase in the weight of both fresh and dry matter of the experimental crop as the crop grows older.

60 Bₒ NaClₒ 50 Bₒ NaCl₁ 40 Bₒ NaCl₂ Bₒ NaCl₃ 30 B₁ NaClₒ 20 B₁ NaCl₁ 10 B₁ NaCl₂ 0 B₁ NaCl₃ Fresh Fresh matter (g/plant) Week Week Week Week Week Week Week B₂ NaClₒ 3 4 5 6 7 8 9 B₂ NaCl₁ B₂ NaCl₂ B₂ NaCl₃ Period of growth (weeks) B₃ NaClₒ B₃ NaCl₁ Figure 2. Fresh matter accumulation of plant on weekly B₃ NaCl₂ basis B₃ NaCl₃

8 Bₒ NaClₒ Bₒ NaCl₁ 6 Bₒ NaCl₂ Bₒ NaCl₃ 4 B₁ NaClₒ B₁ NaCl₁ B₁ NaCl₂ 2

(g/plant) (g/plant) B₁ NaCl₃ B₂ NaClₒ 0 B₂ NaCl₁ Week Week Week Week Week Week Week B₂ NaCl₂ Dry matter accumulation 3 4 5 6 7 8 9 B₂ NaCl₃ Period of growth (weeks) B₃ NaClₒ B₃ NaCl₁ Figure 3: Dry matter accumulation on weekly basis B₃ NaCl₂

But after week six, reduction in the weight of the plants occurred. Plots treated with B₃NaCl₁ recorded the highest fresh and dry matter accumulation on the seventh week as 52.6g and 7g respectively, while treatment B₃NaCl₃ recorded the lowest fresh and dry matter accumulation of 7.8g and 1.7g respectively for the same period.

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3.3.2 Effects of toxicity on plant height

Figure 4 reveals that during the sixth week, for plant height, treatment B3NaCl3 recorded the least value 26.8cm. Thus, the plant reacted more to the treatment than others exposed to less serious level of toxicity, while treatment B3NaCl1 having the highest value 64.2cm for plant height shows that the low sodium chloride salt neutralised the high boric acid applied. Figure 4 shows that during the seventh week of growth, treatment B1NaCl3 recorded the lowest value for plant height (28.80cm).This shows that pots under this treatment were seriously affected by the high NaCl concentration than that of the boric acid.

80 BₒNaCl₀ 70 BₒNacl₁ BₒNacl₂ 60 BₒNacl₃ 50 B₁Naclₒ 40 B₁Nacl₁ 30 B₁Nacl₂ 20 B₁Nacl₃ Plant height (cm) 10 B₂Naclₒ 0 B₂Nacl₁ B₂Nacl₂ Week Week Week Week Week Week Week B₂Nacl₃ 3 4 5 6 7 8 9 B₃Naclₒ B₃Nacl₁ Period of growth B₃Nacl₂ B₃Nacl₃ Figure 4: Average plant height

3.3.3 Effects of toxicity on root growth and leaf production

Figure 5 shows that during the eighth week of growth, B3NaCl3 recorded the lowest value 16.1cm for root length. This result shows that the treatment seriously affected the growth of the test crop, This is reflected in low value (15) of the number of leaves (Figure 6) and the leaf area, 38.5 cm2 (Figure 7). The highest value of 23.3 cm was recorded for plants treated with B₃NaCl1 during the eight week of growth, showing that low sodium chloride application favours root growth. The same treatment, 2 B₃NaCl1 recorded again very high values (82) in Figure 5 and 102cm in Figure 7 for number of leaves and leaf area, respectively. During the ninth week, Figures 4 to 6, the plant has grown to its third stage of growth and development with no subsequent increase in the plant growth parameters, this implies that; at the final growth stage of the plant life span, the plant height, root length, leaf area remain stagnant and flowering begins.

30 Bₒ NaCl₀ 25 Bₒ Nacl₁ Bₒ Nacl₂ 20 Bₒ Nacl₃ 15 B₁ Naclₒ B₁ Nacl₁ 10 B₁ Nacl₂

Root Length Root Length (cm) 5 B₁ Nacl₃ B₂ Naclₒ 0 B₂ Nacl₁ Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 B₂ Nacl₂ B₂ Nacl₃ B₃ Naclₒ Period of study (Weeks) B₃ Nacl₁ B₃ Nacl₂ Figure 5. Effects of toxicity on root growth B₃ Nacl₃

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60 BₒNaCl₀ 50 BₒNacl₁ 40 BₒNacl₂ 30 BₒNacl₃ B₁Naclₒ 20 No. of No. of leaves B₁ Nacl₁ 10 B₁Nacl₂ 0 B₁Nacl₃ Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 B₂Naclₒ B₂NaCl₁ B₂Nacl₂ B₂Nacl₃ Period of study B₃Naclₒ Figure 6. Effects of toxicity on number of leaf B₃Nacl₁ B₃Nacl₂ B₃Nacl₃

200 Bₒ NaCl₀ Bₒ Nacl₁ Bₒ Nacl₂ 150 Bₒ Nacl₃ B₁ Naclₒ 100 B₁ Nacl₁ B₁ Nacl₂ 50 B₁ Nacl₃ Leaf Area Leaf (cm2) B₂ Naclₒ B₂ Nacl₁ 0 B₂ Nacl₂ Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 B₂ Nacl₃ B₃ Naclₒ B₃ Nacl₁ Period of study B₃ Nacl₂ Figure 7. Effects of toxicity on leaf area B₃ Nacl₃

3.3.4 Statistical analysis plant growth parameters

The statistical result for plant growth parameters at the end of each week from the 3rd to the 9th week are presented in Tables 3 to 5. Table 3 is for the means of the four treatments and their interactions on weekly basis. This shows fresh matter accumulation increased rapidly during the weeks at 1% α level. Table 4 shows that dry matter also increased at 1% α level while the effect of treatment on the results obtained was significant at 10% level. These values show that the plant responded to the fertilizer applied than the treatments imposed. Figure 4 shows that treatment B₀NaCl₁ has the highest value of 37.35 cm for plant height. This implies that the treatment caused little or no toxicity, while B2NaCl1 with the least value 22.2cm for plant height shows that toxicity affected plant growth

Table 3. Statistical Analysis of Treatment Means on Fresh Matter Accumulation

Source Variation SS Df MS F P-value F crit

Treatment 647.7357 47 43.1824 1.3905 0.174ns 1.8018

Weeks 4469.5755 5 893.9151 28.7854 0.001* 2.3366

Error 2329.0861 235 31.0545

Total 7446.3974 287

*significant at 1% level, ns not significant

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Table 4. Effect of Treatment Means-Dry Matter Accumulation of Plant

Source of Variation SS Df MS F P-value F crit

Treatment 13.8929 47 0.9262 1.6450 0.0819* ** 1.801

Weeks 82.1683 5 16.4337 29.1872 0.001* 2.3366

Error 42.2283 235 0.5630

Total 138.2896 287

*significant at 1% level, ***significant 10% level

Table 5. Statistical analysis on growth parameters

Groups Count Sum Average Variance

Plant height 48 769.80 48.11 75.14

Root Length 48 317.40 19.84 3.91

Number of Leaves 48 604.20 37.76 45.54

Leaf Area 48 1108.75 69.30 552.83

Fresh matter 48 310.40 19.40 25.74

Dry matter 48 38.52 2.41 0.36

3.3.5 Predicting fresh and dry matter accumulation

Data used in Figure 2 were used to predict fresh matter accumulation. Using the t-test as shown in Table 6, rate of fresh matter production was done. A predictive modeling equation of the form (eqn. 1) was developed.

Fresh matter = -2.579375 + 0.0542(Treatment) + 3.7351(Time), r2=0.725 (1)

Where Treatment = Dosage of B₃NaCl₁

The values of the predicted fresh matter production in eqn 1 were compared with the ones used in Figure 2. The comparison is shown in Figure 8. Data used in Figure 3 were used to predict dry matter production. Using the t-test as shown in Table 7, rate of dry matter production was done. A predictive modeling equation of the form (eqn. 2) was developed.

Dry Matter = 0.2513-0.0020(Treatment) + 0.4539(Time), r2=0.646 (2)

Where Treatment = Dosage of B₃NaCl₁ The dry matter production predicted by eqn 2 were compared with the ones used in Figure 3. The relationship between both values is as shown in Figure 9.

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60 50 Fresh_matter 40 30 Predicted Fresh_matter

20 Fresh Fresh Matter 10 0 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 Case Figure 8. Observed and Predicted Fresh Matter

Dry_matter 6 Predicted Dry_matter

4 Dry Dry Matter 2

0 1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93

Case Figure 9 Observed and Predicted Dry Matter using the model

Table 6: Effects of treatment and time on fresh matter accumulation

Parameters P value Std Error -95% 95% t Stat

Fresh matter -2.5794 0.1654 1.8450 -6.2432 1.0845 -1.3980

Treatment 0.0543 0.6917 0.1365 0.2167 0.3253 0.3978

Period 3.7352 0.0000 0.3684 3.0036 4.4667 10.1392

Table 7: Effect of Time on dry matter accumulation of plant

Parameters P value Std Error -95% 95% t Stat

Dry matter 0.2513 0.3695 0.2786 0.3020 0.8045 0.9018

Treatment 0.0020 0.9225 0.0206 0.0429 0.0389 0.0975

Period 0.4539 0.0001 0.0556 0.3435 0.5644 8.1597

4. DISCUSSIONS The results of the physical properties (Table 1) and the chemical properties (Table 2) of the soil used in the study shows that the low SAR and pH values of the soil conditions before the introduction of the treatments did not influence the toxicity level.

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Figures 2 and 3 show that little amount of sodium ion is required by the test crop, Amaranthus cruentus for its growth, while the test crop can accommodate high boron ion content. This shows that sodium toxicity seriously affected the crop than boron salinity. This result shows why pots treated with B₃NaCl₁ recorded the highest value fresh and dry matter production, while plots treated with B₃NaCl3 recorded the lowest fresh and dry matter production values (Figures 2 and 3). Figures 4 to 7 confirmed again the results, plant growth indices used such as plant height, number of leaves, leaf area and root length were very high on plots tread with B₃NaCl₁ and least for those treated with B₃NaCl3. Therefore, high boron content in the treated pots affected the crop more than high boron ion concentration. The high values of the regression coefficient, r2=0.725 and r2=0.646 for fresh and dry matter accumulation respectively revealing that the predicted values were close the real values.

5. CONCLUSIONS From the results of this study, deduction can be made, that amaranth plant growth is very rapid at early stage and it is more sensitive to sodium chloride toxicity than that of boric acid. At week nine the highest plant height was 66.65cm in treatment B2NaClOand the least plant height was 9.90cm in treatment B2NaCl1 at week three. Combined Boron toxicity and NaCl salinity caused severe toxic effects on growth. The study also shows that reduced uptake of boric acid in the presence of sodium chloride.

REFERENCES

Henderson, D. W. 1981. Influence on Soil Permeability of total salt concentration and sodium in irrigation water. A conference of biosalinity, the problem of salinity in agriculture: a joint conference of Egyptian, Israeli, and American Scientists. Water Resources Center Contribution, No. 14.University of California, Davis.51-53. Läuchli A. and E. Epstein. 1990. Plant responses to saline and sodic conditions. In K.K. Tanji (ed). Agricultural salinity assessment and management. ASCE manuals and reports on engineering practice No, 71. pp 113–137 Marschner, H. 1995. Mineral nutrition of higher plants. Second edition. Academic Press, London, pp. 388– 390. Munns, R. 2002. Comparative physiology of salt and water stress. Plant Cell Environ. 25:239–250. Ojo, O.D.1998. Journal of Vegetative crop production, Vol. 4(1), P HworthPress.Inc, pg 80. Reid, R. 2007. Update on boron toxicity and tolerance in plants. In: Xu F, Goldbach H.E, Brown P.H, Bell R.W, Fujiwara T, Hunt C.D, Goldberg S, Shi L, eds. Advances in Plant and Animal Boron Nutrition. Springer, Dordrecht, the Netherlands, pp. 83-90. Tanaka, M. and Fujiwara, T.2007. Physiological roles and transport mechanisms of boron: perspectives from plants. Eur. J. Physiol. (DOI 10.1007/s00424-007-0370-8). Shorrocks, V.1997. The occurrence and correction of boron deficiency. Plant Soil 193, 121-148. Simmonds, N.W(Ed). Longman, London, pg 4.