Essay: Yield response to salinity and sodicity of irrigation water

PRELIMINARY GUIDELINE FOR YIELD RESPONSE TO SALINITY AND SODICITY OF IRRIGATION WATER UNDER NORTH NILE DELTA CONDITIONS

ABSTRACT

Preliminary Guideline of tolerance of soybean, canola, sunflower, cotton and sugar beet crops to salinity and sodicity of irrigation water were introduced through long term lysimeter experiments in sand culture under North Delta climatic conditions. Linear equation of different crops indicate that, the relative yield decrement oh with increasing unit of ECw were 16.02 , 14.59, 13.88, 6.44 and 5.31 oh for sunflower, canola, soybean, cotton and sugar beet, respectively under SAR 10. Also, increasing the SAR of irrigation water increased the adverse effect of EC* on the crop yield. The crops under consideration could be arranged in the following descending order, according to their tolerance to salinity of irrigation water.

Sugar beet >Cotton > Soybean > Canola > Sunflower.

The multiple regression equations described the combined effect of ECw and SARw on crop yield were:

Yield decrement %:

= -28.708 + 14.884 ECw + 1.608 SARw

= -25.541+ 17.0l6 ECw + 1.098 SARw

= -16.089 + 14.867 ECw + 0.784 SARw

= -21.116 + 6.135 ECw +1.286 SARw

= -22.323 + 4.9028 ECw +1.0 SARw

For soybean, sunflower, canola, cotton and sugar beet crops, respectively’

Key words: Guideline, Irrigation water, Salinity, Sodicity

INTRODUCTION

Field crops are differing greatly in their response to salinity according to species, variety, physiological stage of plant growth and environmental conditions (Balba, 1962, FAO, 1976 and Mffiries, 1988). Mass, (1986), tabulated a number of economic crops according to their tolerance to salt and stated that, cotton and sugar beet are tolerant crops while soybean is moderately tolerant and sunflower is moderately sensitive crop. The salt tolerance of various crops are conventionally expressed (after Mass and Hoffman, l977), in terms of relative yield, threshold salinity value (a) and percentage decrement value per ECw unit over the threshold (b), while soil salinity is expressed in terms of ECe, in dS/m, as the follows:

Y=100-b(ECe-a)

The use of saline water for irrigation should be evaluated for the specific conditions where it is used, since the crop yields depend on leaching fraction and. climatic factors at the same locality. It was also found that, the model recommended for the relation between yield and soil salinity by Mass, dose not fit well for yield and irrigation water salinity Abd El-Gawad and Ghaibeh, (l998). Systematic approach was suggested by Abd El-Gawad and Ghaibeh, (l997), to determine the relative yield as a result of increasing salinity of irrigation water. Therefore they considered the EC in equation of Mass represents the mean electrical conductivity of the irrigation water throughout the season, and they suggested quadratic and exponential equations as follows:

Y= A + B (EC – T) + C ( EC – T)2 and

Y= A exp (EC – T)

Where A is the absolute yield, B is the slope, EC is the mean value of electrical conductivity of the irrigation water throughout the season, and T salinity threshold expressed in dSm-l. The effect of salinity and sodicity on plant growth is related to high osmotic pressure of soil solution which results in decreasing the physiological availability of water, and accumulation of toxic ions within the plant tissues, (Tavassoli, 1980). In this respect, El-Shakweer and Barkat, (1984) stated that, seed cotton yield was reduced to 600/o by raising of salinity of irrigation water from 200 to 8000 ppm and to 80% by raising of Adj. SAR from 10 to 30. Also, they added that the reduction of seed cotton yield due to salinity was increased as Adj SAR increased.

On the other hand, Dkl (1993) reported that, the drop in the cotton yield amounts to 25% with irrigation water salinity up to 6000 ppm. Abd El-Gawad and Ghaiba (1998), stated that, the reduction of cotton yield were 11, 9.8 and 9.1% when the EC of irrigation water increased one unit at zero, 0.15 and 0.30 leaching fraction, respectively. They added that, the ECw of zero yield were 13.8, 15.0 and 15.7 dSm-l at the previous levels of leaching fraction. Concerning soybean yield, DRI, (1993), stated that, the yield of soybean was highly related to the irrigation water salinity where the yield was reduced by 12, 37 and 74% at salt concentration of 1500, 2400 and 3100 ppm, respectively. The sugar beet yield decrement amount to 25Yo with EC of irrigation water 7.5 dS/m and soil salinity 11 dS/m while the same reduction in soybean yield was detected with ECw 4.02 dS/m and the ECe 6.2 (FAO, 1976). Mass (1986) stated that, cotton and sugar beet are tolerant crops while sunflower is moderately sensitive to salinity. He also stated that the soybean is moderately tolerant crop, and its yield was reduced by 16% with increasing one unit of ECw. The objectives of this study are to evaluate the usability of low quality water with different levels of ECw and SARw for irrigating five crops and to introduce a primary guideline of salt tolerance for these crops under local conditions. In this cconcern, Mohamedin et al. (2010) observed the negative effect of wither soil salinity and /or water table depth on wheat, sunflower and cotton yields grown in the east Nile delta region. The study found that wheat and sunflower were more tolerant to the shallow water table depth rather than soil salinity effect. On contrary, shallow water table depth was negatively affect cotton yield due to the length of cotton roots.

MATERIALS AND METHODS

Long term experiment was conducted in lysimeters using sand culture technique at Sakha Agricultural Research Station in five successive growing seasons started in summer season 2012, to study the effect of salinity and sodicity of irrigation water on the yield of soybean, canola, sunflower, sugar beet and cotton crops. The experiment was conducted in split-plot design with three replicates. Three levels of sodium adsorption ratio, SAR (10, 15 and 20) were assigned in the main plots, while the salinity levels occupied the subplots. The levels of salinity as electrical conductivity EC, were 1, 2, 4, and 8 dS m-1 for soybean, Sunflower and canola crops, and were 2, 4, 6, and 8 dS m-l for cotton and 4, 8, 12 and 16 dS m-1 for sugar beet crop. The control plots were irrigated with fresh water (EC: 0.5 dSm-1). Hogland’s nutrient solution was used with all treatments to supply the crops with essential macro and micro elements. Artificial salty solutions with different levels of EC and SAR were prepared using NaCl and CaCl salts. After germination, the plants were thinned to fixed uniform and well-distributed plants per plot. Fresh water was used for irrigation till complete germination, then the plants were watered with Hoagland solution containing salt mixture in different concentrations. In order to avoid salt shocking the young seedling, the solutions were applied stepwise to the cultures to reach the finally required concentration. To obtain fixed osmotic pressure and to avoid moisture stress, water losses by evapotranspiration was daily compensated.

RESULTS AND DISCUSSION

1. Effect of Salinity and Sodicitv of Irrigation Water on Yield:

The yield or the economic value of the crop is taken as a criterion when cultivated plants are compared together according to their tolerant to salt. Usually the relative yield of the crops irrigated with saline water is compared with its absolute yield with fresh water. The salt level of soil causing a 50% or 25% yield depression are taken as the tolerable soil salt level for the given crop, (FAO,I973). Data of absolute and relative yield of sugar beet, soybean, sunflower, canola and cotton as influenced by different levels of salinity and sodicity of irrigation
water are listed in Tables (1-5) As a general trend
, the yields of different crops decreased as salinity and sodicity levels in irrigation water increased. The relatively decrement in the yields were differed from crop to another on based of their tolerant to salinity and sodicity. Cotton and sugar beet are tolerant crops, while sunflower and canola are moderately sensitive while soy bean is moderately tolerant crops. These results are in good agreement with those obtained by FAO, (1976) Mass, (!986) DM, (1993) and Rhoodes et al (1992)

2. Mathematical Relations between Relative Decrement of Different Crop Yield and Salinity of Irrigation Water under Different SAR Levels.

Data of relative decrement of yield versus salinity and sodicity of irrigation water were evaluated throughout linear equation for each crop. The relative yield decrement %o represent the dependant variable while the salinity expressed in EC dSm-l represent the independent variable and the equation takes the form Y: ax + b

Where: y: Relative decrement %; x: Salinity of irrigation water

a: Slope (yield reduction % with increasing EC*by one unit); b: The intercept.

Table (1): Yield of sugar beet (kg/plot) and Relative Decrement o/o as affected by salinity sodicity of irrigation water.

ECw (ds/m) Yield Relative Decrement %

SAR 10 SAR 15 SAR 20 SAR 10 SAR 15 SAR 20

4 3.23 2.95 2.70 6.38 14.49 21.74

8 2.75 2.53 2.25 20.29 26.67 34.78

12 1.88 1.65 1.42 45.51 52.17 58.84

16 1.05 1.00 0.85 69.57 71.01 75.36

Fresh water 3.45 0

Table (2): Yield of soybean (g/plot) and Relative Decrement o/o as affected by salinity sodicity of irrigation water.

ECw (ds/m) Yield Relative Decrement %

SAR 10 SAR 15 SAR 20 SAR 10 SAR 15 SAR 20

1 105 100 95 7.08 11.50 15.93

2 90 88 85 20.35 22.12 24.78

4 58 53 35 48.67 53.10 69.03

Fresh water 113 0

Table (3): Yield of sunflower (g/plot) and relative decrement o/o as affected by salinity sodicity of irrigation water.

ECw (ds/m) Yield Relative Decrement %

SAR 10 SAR 15 SAR 20 SAR 10 SAR 15 SAR 20

1 138.0 132.0 118.2 3.16 7.37 17.05

2 110.3 105.2 100 22.60 26.18 29.82

4 86.2 75.1 68.2 39.51 47.30 52.14

8 29.2 13.9 13.1 78.84 89.47 88.92

Fresh water 142.5 0

Table (4): Yield of canola (g/plot) and Relative Decrement o/o as affected by salinity sodicity of irrigation water.

ECw (ds/m) Yield Relative Decrement %

SAR 10 SAR 15 SAR 20 SAR 10 SAR 15 SAR 20

1 290 280 260 3.33 6.67 13.33

2 210 200 180 30.00 33.33 40.00

4 150 140 130 50.00 53.33 56.67

8 100 90 70 65.52 67.86 73.08

Fresh water 500 0

Table (5): Yield of cotton (g/plot) and relative decrement o/o as affected by salinity sodicity of irrigation water.

ECw (ds/m) Yield Relative Decrement %

SAR 10 SAR 15 SAR 20 SAR 10 SAR 15 SAR 20

2 72.60 65.22 60.17 2.05 12.10 18.82

4 64.28 58.18 53.33 13.28 21.51 28.05

6 53.12 47.83 42.18 28.33 35.47 43.09

8 44.50 39.13 34.12 39.96 47.21 53.97

Fresh water 74.12 0

Fig (1): Relation between salinity of irrigation water and yield decrement % under different SAR levels.

Different liner equations for every crop and representative graphics described these equations were presented in Fig(1) Linear equations and representative graphics of different crops indicate that, the relative yield decrements % with increasing one unit of ECw were 16.02, 14.59,13.88, 6.44 and 5.37% for sunflower, canola , soybean, cotton and sugar beet crops, respectively. Also, it could be observed that, with increasing SAR, the crop reduction o/o increase with increasing ECw. Also, it could be concluded that, the crops under consideration can be arranged in the following descending order, from salt tolerant of view.

Sugar beet < Cotton < soybean < Canola < Sunflower.

3. Preliminary Guide line for Effect of Salinity and Sodicity of Irrigation Water on Some Field Crops at The North Delta.

Data illustrated in Table (7) and Fig (2) represents a guideline introduced from previous linear equations of crops. The table includes the expected yield reduction of 10, 25,50,75,90 and 100% due to increasing irrigation water salinity under three levels of SAR. Data indicate that each increase in irrigation water salinity will cause a proportionate decrease in the yield. Data also indicated that, sugar beet crop is the most tolerant crop followed by cotton, while sunflower is the least one. On the basis of, 50% reduction in crop yield, the crop can be arranged in the descending order from salt tolerant point of view, sugar beet > Cotton > soybean > Canola > Sunflower. Data also indicate that the hazard effect of SAR on the yields was increased with increasing of ECw of irrigation water and vice versa.

Comparing data presented in preliminary Guideline Table (7) with Guideline introduced by FAO, l976 for cotton, sugar beet and soybean crops, Table (6). It could be concluded that, Values of ECw causing 50% reduction of yield were 9.39, 12.7I and 4.1 dS m-l in the current Guideline while the corresponding values of FAO were 12, 10.0 and 5.0 dSm-l for cotton, sugar beet and soybean crops, respectively. Zero yields were detected at 17.28, 22.0 and 7.7 dSm-l while the values of FAO were 18.0, 16.0 and 6.7 dSm-l for the previous crops.

The differences of values between the current Guideline and FAO Guideline may be due to the soil salinity effect, which was taken into consideration by FAO, while the effect on crop yield was related to salinity of irrigation water only in the current Guideline.

Table (6): Yield decrement to be expected for some crops as results of soil and irrigation water salinity (FAO, 1976).

Crops Yield decrement

Zero 10% 25% 50% 100%

ECw ECe ECw ECe ECw ECe ECw ECe ECw ECe

Cotton 5.1 7.7 6.4 9.6 8.4 13.0 12.0 17.0 18.0 27.0

Sugar beet 4.7 7.0 5.8 8.7 7.5 11.0 10.0 15.0 16.0 24.0

Soy bean 3.3 5.0 3.7 5.5 4.2 6.2 5.0 7.5 6.7 10.0

Table (7): Yield Decrement to be expected for Certain Crops due to Salinity and sodicity of irrigation water.

SAR 10

ECw

Crops 10% 25% 50% 75% 90% 100%

Soy bean 1.225 2.305 4.106 5.907 6.988 7.708

Sunflower 1.325 2.262 3.822 5.382 6.318 6.943

Canola 1.145 2.173 3.887 5.601 6.629 7.315

Sugar beet 5.260 8.060 12.71 17.37 20.02 22.024

Cotton 3.460 5.680 9.39 13.09 15.32 16.80

SAR 15

ECw

Crops 10% 25% 50% 75% 90% 100%

Soy bean 1.079 2.101 3.804 5.506 6.528 7.209

Sunflower 1.166 1.997 3.384 4.770 5.602 6.157

Canola 1.004 2.013 3.695 5.377 6.386 7.058

Sugar beet 3.630 6.700 11.83 16.95 20.03 22.08

Cotton 3.610 6.070 10.16 14.26 16.71 18.35

SAR 20

ECw

Crops 10% 25% 50% 75% 90% 100%

Soy bean 0.953 1.746 3.069 4.392 5.185 5.714

Sunflower 0.909 1.774 3.216 4.658 5.524 6.101

Canola 0.747 1.735 3.382 5.029 6.017 6.676

Sugar beet 1.850 5.090 10.50 15.91 19.15 21.317

Cotton 3.370 5.820 9.920 14.01 16.47 18.110

4. The
Combined Effect of ECw and SARw:

The combined effect of salinity and sodicity of irrigation water on the relative yield decrement of every crop is described through the multiple regression
equations using the Management Scientist software program, version 1.1 designed by R. Anderson et al.1988 as follows:

4.1 Soybean crop: Yield decrement % = -28.708 + 14.884 ECw + 1.608 SAR (R2=97.1%);

4.2 Sunflower crop: Y = -25.541 + 11.016 ECw + 1.098 SAR (R2=99.6%);

4.3 Canola crop: Y= -16.089 + 14.867 ECw + 0.784 SAR (R2= 100%);

4.4 Cotton crop Y= -21.1 16 + 6.135 ECw+l.286 SAR (R2= 99.9);

4.5 Sugar beet Y= -22.324 + 4.902ECw + 1.0 SAR ( R2: 99.6 %).

Fig (2): Yield Decrement to be expected for Certain Crops due to Salinity and sodicity of irrigation water.

content was increased with organic manure combined with sulphur. The increases were more pronounced with increasing the application rate of organic manure. The differences in the content of organic matter in the soil may be due to the differences in decomposition degree of the added organic manure. These results were similar to that reported by (Awad, I99I , Ghazy I994 and Abd Allah, 1998).

Concerning the soil organic matter content after the second and third crops, data indicate that the values of soil organic matter content was decreased by the time because the decomposition of applied manure was increased with increasing decomposition period , temperature and microbial activities. The values of OM of the surface layers were higher than those of the deeper layers.

It can be concluded from the above results that, increasing the application rate of organic manures up to 22.5 ton /fed increased soil organic matter content. Also, the residual effect of organic manures on soil organic matter is different due to their chemical composition and the degree of mineralization.

5. Content of soil sulphate (SO4=)

Data in Table (3) reveal that, there were considerable effects of the sulphur application on the formation of sulphate ions. The amounts of SO4= was increased from 1.13 and 1.0 to 1.35 and l.2l meqlI00g soil in surface and subsurface layers, respectively due to addition of sulphur. On the other hand, the application of organic manure in presence of sulphur produced higher amounts of SO4=. The sulphate content in the soil was gradually decreased with the time, may be due to the leaching of SO4= in drainage water and decreasing the amount of SO4= released from organic manures in the later stages as well as the uptake of SO4= ions by plants. These results were in good agreement with those obtained by Bayoumi et al, (1985).

6- Available Macro Nutrients of Soil:

Data in Table (4) showed the effect of different sources of organic manures in presence of sulphur on the total nitrogen content, available phosphorus and potassium in the studied soil. Data show that total nitrogen in soil that received organic manure combined with sulphur was higher than untreated soil. The percentage of total nitrogen in soil was relatively higher with sewage sludge than with farmyard manures. Meanwhile, the total nitrogen content was slightly affected with the rates of organic manure in both soil depths.

The availability of P in the soil may be influenced by adding elemental sulphur and organic materials. The oxidation of elemental sulphur leads to formation of sulphuric acid which reacts with calcium phosphate increasing the availability of P. The organic acids, which result from the microbial decomposition of added organic matter, may solubilize the insoluble phosphate forms by chelating action and lowering soil pH (Stevenson, 1982). The values of available P was slightly increased after harvesting the second crop, and then decreased after harvesting the third crop, may be due to exhausting of the added sulphur by the time and rising the pH of-the tested soil due to its buffering action.

Data in Table (4) show that values of available P was greatly increased with organic manure combined with sulphur. ‘The effectiveness of different treatments can be arranged according to the following descending order: (S+ TSS t (S +FYN4) were obtained with higher rate of added organic materials (22.5 ton / fad).

The organic matter definitely plays an active role in the availability of K+ in soil. Potassium releasing from non-exchangeable form takes place when the equilibrium between various forms is unbalanced. This may occur when the soluble and low exchangeable forms of K are exhausted through plant absorption. (Abou Zeid et al, ,1992).

Data in Table (4) show that the available K was increased from 410 to 434 and from 428 to 429 ppm in surface and subsurface soil, respectively as a result to addition of sulphur. This may be attributed to the increase of soil biological activities with sulphur application and cort sequent increase soil acidification and K availability. The values of available K were gradually decreased after harvesting the third crop, maybe due to decline the activity of S-oxidation micro-organisms by the time.

The effectiveness of sulphur was pronounced in plots treated with different sources of organic manure especially sewage sludge. The effects of different organic wastes on the availability of K in the tested soil were different and may be due to the differences in chemical composition and the decomposition rate of organic manure.

II- Effect of Sulphur and Organic Manure on Crop Yield

1- Sugar beet:

Data in Table (5) show that the addition of sulphur significantly increased the yield of roots and sugar. The yield of roots and sugar were 24.22 and 4.14 tons/fad, respectively as a result of sulphur application compared with 20.35 and 3.15 tons/fad for roots and sugar yield, respectively with untreated soil. This effect may be due to sulphuric acid which lower the pH and increases the availability of some nutrient elements and hence positively affected the crop yield. Also, the effect of sulphur in increasing yield of sugar beet might be attributed to increasing the depth of root zone resulting in higher uptake of nutrients and thereby increasing the vegetative growth and yield, (Abd El-Fattah et al, 1990 and Abd-Allah, l998).

Concerning the combined effect of sulphur and organic manures on the yield of roots and sugar, data in Table (5) show that application of organic manures combined with sulphur produced higher amounts of roots and sugar compared with sulphur alone. The application of sewage sludge was more effective than farm yard manure on root yield. This may be due to the high content of organic matter and low salinity of sewage sludge compared with farmyard manure.

2- Seed melon:

Data in Table (5) show that seed melon yield with sulphur was significantly increased over the control. The seed yield was increased from 305.0 to 391.0 kg/fad, and the percent of the increase was 28.38% over control. This may be due to that the residual effect of sulphur acts as an amendment for soil alkalinity and gradually decrease the ESP values. The results of the residual effect of organic manure combined with sulphur on seed melon yield are given in Table (5). These results indicate that there.are significant increases in seed melon yield and the highest increase in yield were obtained by sewage sludge combined with sulphur where percent of increase was 38.79o/o over the control. On the other hand, effect of organic manure rates on seed yield was insignificant.

3- Egyptian Clover:

Data of the residual effect of sulphur alone or mixed with organic manures on the dry matter of clover (sum of 3 cuts) are given in Table (5). The dry yield with sulphur was clearly increased over the control by 34.1%.

The residual effect of sulphur in soil can be extended over five successive agriculture seasons and the increa
se in crop production depends upon the rate of added sulphur (Hilal, 1990).

The results of the residual effect of organic manures combined with sulphur on yield of clover show that the yield was generally increased over the control. The highest dry weight was obtained with sewage sludge where dry matter was increased by 54.69% over the control and by about 9oh over the yield obtained by farm yard. These differences of the residual effects of organic materials maybe due to their chemical composition, degree of decomposition and their pH which impact on the availability of the nutrients in soil (Hassanien et al , 1992 and Abd-Allah, I998).

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