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Response of wheat to saline irrigation and drainage
Agricultural water management ELSEVIER
Agricultural Water Management 32 (1997) 285-291
Response of wheat to saline irrigation and drainage B.K. Khosla, R.K. Gupta Cenrral Soil Sulinity Research Institute, Karnd-132
001, Haryanu, India
Accepted 3 July I996
Abstract The response of wheat (Triticum aesriuum L.) to varying depths of irrigation, quantity applied and to the drainage conditions was studied in 2 m X 2 m X 2 m size lysimeters with a sandy loam soil. Saline water with an electrical conductivity of 8.6 dSm_’ was irrigation. The treatments included four irrigations of 5 cm depth, four irrigations of 7 three irrigations of 9 cm, scheduled on the basis of cumulative pan evaporation, while the
of water filled in used for cm, and
drainage conditions were represented by the drained and undrained lysimeters. Another treatment, using good quality water for irrigation, represented the potential yield of the crop. The growth parameters, as well as the yield, showed an improvement with larger irrigation depth increments in the drained lysimeters. But, in contrast, in the undrained lysimeters, the yield was reduced with larger irrigation depth increments, mainly due to a sharp rise in water table depth during the irrigation cycles. The rise and fall in water table showed a high sensitivity and were also highly disproportionate to the irrigation and evapotranspiration events. The yield tended to be higher with a smaller depth of water applied more frequently in the undrained lysimeters. But, in view of the limitations of conventional surface irrigation to apply water in smaller depth increments, an improved drainage is imperative for cropping in shallow saline water table conditions. 0 1997 Elsevier Science B.V. Keywords: Lysimeters; Irrigation depth increments; Drainage; Water table
1. Introduction The availability of water plays a crucial role in crop production in the arid and semi-arid regions because of the scanty rainfall. The introduction of new irrigation projects, however, has often led to a rise of ground water table and consequently salinisation of the soil. It is estimated that nearly 50% of all the irrigated lands in the world are affected by secondary salinisation, alkalinisation and waterlogging (Szabolcs, 1975). Soil salinity in India, which is invariably associated with the occurrence of a shallow and saline water table, has been posing a serious threat to agriculture in the 0378.3774/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved. PI/ SO378-3774(96)01272-3
286
B.K. Khosla, R.K. Gupta/Apkxlturul
Water Manu~ement 32 (19971285-291
canal irrigated areas of arid and semi-arid regions, although it was recognised a long time ago that the policy of providing surface drainage alone will not serve the purpose (Bhumbla, 1981). Amongst various measures, drainage and irrigation practices play a significant role in alleviating the problem. In the present study, the response of wheat to varying irrigation in relation to drainage conditions was examined, utilising saline water for irrigation.
2. Materials
and methods
The study was conducted in 2 m X 2 m X 2 m size lysimeters filled in with a sandy loam soil (sand, silt, clay content 59.0%, 21.7% and 18.9%, respectively) and having a bulk density of 1.45 g cme3. The soil moisture characteristic curve was prepared from the tensiometric data using mercury manometers and the soil water content determined gravimetrically (Fig. 1). The irrigation treatments comprised (i) four irrigations of 5 cm depth, (ii) four irrigations of 7 cm depth and, (iii) three irrigations of 9 cm depth, applied on the basis of cumulative pan evaporation (CPE). Whereas (i) and (ii) corresponded to a CPE of 50 mm, (iii> was scheduled after a CPE of 70 mm. The first irrigation was, however, applied at the time of crown root initiation which is considered a critical stage. Saline water having an electrical conductivity of 8.6 dS rn- ’ and SAR 13.2 mmolf5 ll’.” was used for irrigation. The drainage conditions were represented by free or gravity drainage and a closed outlet at the bottom, designated, respectively, as drained and undrained lysimeters. A control treatment, irrigated with good quality water (EC,, 0.4 dS m- ‘> was also included, to provide potential yield of the crop. All the treatments were replicated three times in a completely randomised block design. Wheat (variety HD 2009) was sown in rows 20 cm apart after a presowing irrigation of 5 cm. Fertiliser N, P,O, and K,O were applied at 75 kg ha- ’, 60 kg ha-’ and 30 kgha-‘, respectively, at the time of sowing and N was again applied along with the first irrigation. A sizeable area surrounding the lysimeters was cropped uniformally with wheat in order to minimise any microclimatic variations and boundary effects. The
01
’
O-20 Soil
’
O-28 water
’
I
036
content
’
’
’
044
(cm3
Fig. I. Soil moisture characteristic
cm-3
1
curve.
’
0.52
B.K. Khosla, R.K. Gupta /Agricultural
Nov.
Fig. 2. Cumulative
Dee.
pan evaporation
Jon.
Water Munqement
Feb.
and rainfall distribution
32 (1997) 285-291
Mar.
281
Apr.
during the growth period
growth parameters recorded were the plant height, number of tillers, ear heads and their length, representing 1.6 m row length, in addition to the grain and straw yield. The water table was recorded in the undrained lysimeters by connecting a vertical transparent plexi glass tube to the bottom of lysimeters. Soil samples were obtained at the time of sowing and harvest in 20 cm increments to a depth of 180 cm and water content was determined gravimetrically. The samples were ground to pass through a 2 mm sieve and analysed for electrical conductivity in 1:2 soil water extract. The U.S. open pan evaporation and rainfall data were obtained from a nearby observatory. The cumulative pan evaporation and rainfall distribution during the growth period of the crop are presented in Fig. 2.
3. Results 3.1. Crop response The data on various growth parameters and yield as affected by the treatments are presented in Table 1. A higher grain yield was obtained with increased depth of irrigation and quantity of water applied in the drained lysimeters. But, in contrast, in the undrained conditions, the yield showed a decline due to larger irrigation depth increments of 7 cm and 9 cm depth. Although the treatment differences were statistically non-significant, the relative yield (taking the grain yield obtained in the T, treatment as 100%) was increased by nearly 20% in T4. compared with the T, treatment in the drained conditions. In the undrained conditions, the yield was rather more in the case of smaller (T,) than the larger irrigation depth increments (T, treatment). The variations in yield were also reflected in the growth parameters and the yield bearing attributes. The plant height was lowered significantly in the T, treatment, compared with the control. This indicated that in the case of impeded drainage, the plant growth was affected to a
288
B.K. Khosla, R.K. Gupta /Agriculturul
Table 1 Growth parameters Treatment
Wuter Munagemenr 32 (1997) 285-291
and yield as affected by various treatments
Plant height (cm) Days after sowing
Effective tillers
Number of ears
Ear length (cm)
(g)
Relative yield (%)
Grain yield
52
77
94
T, T, T3 T4 Undrained
36.6 34.9 36.3 35.3
66.9 64.2 68.1 66.1
87.6 79.3 86.8 85.6
225 196 217 248
201 163 165 202
10.4 10.0 10.1 10.3
206 161 176 206
100 78 85 99
T, T6 T, CD (0.05)
37.4 37.8 28.9 4.1
67.3 68.2 58.5 3.4
86.9 87.8 77.0 7.3
179 195 168 47
152 174 140 33
9.7 10.0 9.6 0.6
183 157 162 NS
89 76 79
T, represents
control.
Drained
greater extent by larger irrigation depth increments. Similarly, the number of tillers and earheads were observed to be higher in the drained lysimeters and increased with depth of irrigation but showed a significant reduction in the T, treatment, representing undrained conditions. 3.2. Fluctuations
in water table
The fluctuations in water table depth during the growth period are shown in Fig. 3. The mean water table depth, standard deviation and coefficient of variation for selected
O-
40 Y 9 $g
80-
$ e B
120 -
P 160 -
200-
Fig. 3. Fluctuations
in water table depth (arrows indicate the timings of irrigation).
B.K. Khosla, R.K. Gupta/Agricultural
Water Management 32 (1997) 285-291
289
Table 2 Mean water table depth, standard Treatment
Days after sowing
deviation
and coeffkient
of variation
Mean water table depth km)
Standard deviation
Coefficient of variation (%)
TS
27 39 59
83 130 176
29.5 14.9 4.5
35.4 11.4 2.6
Tb
27 39 59
140 157 188
25.8 15.5 2.6
18.4 9.9 1.4
T,
27 49 98 110 125 136
6 102 I8 124 42 149
3.4 7.3 6.0 13.1 26.5 15.1
53.7 7.2 34.1 10.6 62.7 10.1
days are presented in Table 2. The water table depth showed a sharp rise in the undrained lysimeters, particularly when the irrigations comprised a larger depth increment. In T, treatment, when 9 cm depth of water was applied at each irrigation, the average rise of water table during the various irrigation cycles was to the extent of 16 cm cm-’ of water applied. The sharp rise in water table was followed by an initial rapid decline, which resulted mainly due to the evapotranspiration losses. This indicated that in shallow water table conditions, application or withdraw1 of water can result in a highly disproportionate rise as well as fall in water table. Gillham (1984) also observed a high sensitivity of water table to irrigation and evapotranspiration events and attributed it to an increase in the gas phase pressure in the unsaturated zone above the water table during the infiltration process, and the variable specific yield which decreased as the water table approached ground surface. The standard deviation and coefficient of variation (Table 2) tended to be higher when water table was at shallow depths following irrigation cycles and the values decreased with lowering of the water table depth.
4. Discussion The reduction in growth as well as grain yield of wheat during saline water irrigation in the undrained lysimeters was mainly associated with larger irrigation depth increments and due to the sharp rise in water table depth. It was seen that in the case of T, treatment the water table remained within 50 cm depth for a cumulative period of 18 days during the growth period of the crop. The occurrence of saline water table at rather shallow depths limited the proliferation of roots to lower depths and the soil water uptake was, thus, adversely affected. Chaudhary et al. (1974) observed that an increase
290 Table 3 Cumulative
B.K. Khosla, R.K. Gupta/Agriculturul
soil water depletion
Water balance components
(cm)
Initial soil water content Soil water content at harvest Depth of irrigation water applied Rainfall Cumulative soil water depletion
Water Management
32 (1997) 285-291
in 0- 180 cm depth Drained lysimeters TZ
T,
43.6 3 I .9 25.0 6.8 43.5
52.6 42.0 33.0 6.8 50.4
Undrained
51.2 39.0 32.0 6.8 5 I .o
lysimeters
TX
T6
T,
60.2 45.8 25.0 6.8 46.2
55. I 47.3 33.0 6.8 41.6
61.3 55.7 32.0 6.8 44.5
in salinity of ground water caused greater reduction in wheat yield with shallow than with deep water table, and the total water use was decreased from 58.8 cm when the water table was at 150-52.9 cm when the water table occurred at 60 cm depth. The cumulative soil water depletion was also calculated in the present study from the water balance components and is presented in Table 3. The values were in general higher for the drained as compared to the undrained conditions. It was only when water was applied in smaller depth increments (T,) that the soil water depletion tended to be more in the undrained than the corresponding T, treatment in the drained lysimeters. It was earlier pointed out (Shainberg and Shalhevet, 1984) that a higher frequency during saline water irrigation resulted in higher yield. A relatively greater reduction of yield in the undrained, compared with drained conditions, may also be related to higher accumulation of salts at the surface in the undrained lysimeters.
5. Conclusions The study indicated that the growth and yield of saline water irrigated wheat was affected to a greater extent in the undrained than the drained conditions, particularly when the irrigations comprised a larger depth increment, as these resulted in a sharp rise in water table. The rise as well as fall in water table during irrigation cycles, when drainage was lacking, showed a high sensitivity and were also highly disproportionate to the depth of irrigation and the evapotranspiration events. Although, with smaller depth of water applied more frequently, the yield tended to be higher in the undrained conditions, and considering the usual limitations of surface irrigation to apply water in smaller depth increments, improved drainage is imperative for cropping in shallow and saline water table conditions.
Acknowledgements Thanks are due to Arjen Kumar for providing the technical help, R.K. Madaan typing the manuscript and Purshotam La1 for preparing the figures.
for
B.K. Khosla, R.K. Guptu /Agricultural
Water Management
32 (1997) 285-291
291
References Bhumbla, D.R., 1981. Land and water management and agricultural production in India. J. Indian Sot. Soil Sci., 29: 403-418. Chaudhary, T.N., Bhatnagar, V.K. and Prihar, S.S., 1974. Growth response of crops to depth and salinity of ground water, and soil submergence. 1. Wheat (Tritium aestiuum L.) Agron. J., 66: 32-35. Gillham, R.W., 1984. The capillary fringe and its effect on water-table response. J. Hydrol., 67: 307-324. Shainberg, I. and Shalhevet, J. (Editors), 1984. Soil salinity under irrigation processes and management. Springer-verlag, New York, pp. 349. Szabolcs, I., 1975. Present and potential salt-affected soils-an introduction. FAO Bull. 31. Prognosis of salinity and alkalinity, pp. 9-13.
Agricultural Water Management 32 (1997) 285-291
Response of wheat to saline irrigation and drainage B.K. Khosla, R.K. Gupta Cenrral Soil Sulinity Research Institute, Karnd-132
001, Haryanu, India
Accepted 3 July I996
Abstract The response of wheat (Triticum aesriuum L.) to varying depths of irrigation, quantity applied and to the drainage conditions was studied in 2 m X 2 m X 2 m size lysimeters with a sandy loam soil. Saline water with an electrical conductivity of 8.6 dSm_’ was irrigation. The treatments included four irrigations of 5 cm depth, four irrigations of 7 three irrigations of 9 cm, scheduled on the basis of cumulative pan evaporation, while the
of water filled in used for cm, and
drainage conditions were represented by the drained and undrained lysimeters. Another treatment, using good quality water for irrigation, represented the potential yield of the crop. The growth parameters, as well as the yield, showed an improvement with larger irrigation depth increments in the drained lysimeters. But, in contrast, in the undrained lysimeters, the yield was reduced with larger irrigation depth increments, mainly due to a sharp rise in water table depth during the irrigation cycles. The rise and fall in water table showed a high sensitivity and were also highly disproportionate to the irrigation and evapotranspiration events. The yield tended to be higher with a smaller depth of water applied more frequently in the undrained lysimeters. But, in view of the limitations of conventional surface irrigation to apply water in smaller depth increments, an improved drainage is imperative for cropping in shallow saline water table conditions. 0 1997 Elsevier Science B.V. Keywords: Lysimeters; Irrigation depth increments; Drainage; Water table
1. Introduction The availability of water plays a crucial role in crop production in the arid and semi-arid regions because of the scanty rainfall. The introduction of new irrigation projects, however, has often led to a rise of ground water table and consequently salinisation of the soil. It is estimated that nearly 50% of all the irrigated lands in the world are affected by secondary salinisation, alkalinisation and waterlogging (Szabolcs, 1975). Soil salinity in India, which is invariably associated with the occurrence of a shallow and saline water table, has been posing a serious threat to agriculture in the 0378.3774/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved. PI/ SO378-3774(96)01272-3
286
B.K. Khosla, R.K. Gupta/Apkxlturul
Water Manu~ement 32 (19971285-291
canal irrigated areas of arid and semi-arid regions, although it was recognised a long time ago that the policy of providing surface drainage alone will not serve the purpose (Bhumbla, 1981). Amongst various measures, drainage and irrigation practices play a significant role in alleviating the problem. In the present study, the response of wheat to varying irrigation in relation to drainage conditions was examined, utilising saline water for irrigation.
2. Materials
and methods
The study was conducted in 2 m X 2 m X 2 m size lysimeters filled in with a sandy loam soil (sand, silt, clay content 59.0%, 21.7% and 18.9%, respectively) and having a bulk density of 1.45 g cme3. The soil moisture characteristic curve was prepared from the tensiometric data using mercury manometers and the soil water content determined gravimetrically (Fig. 1). The irrigation treatments comprised (i) four irrigations of 5 cm depth, (ii) four irrigations of 7 cm depth and, (iii) three irrigations of 9 cm depth, applied on the basis of cumulative pan evaporation (CPE). Whereas (i) and (ii) corresponded to a CPE of 50 mm, (iii> was scheduled after a CPE of 70 mm. The first irrigation was, however, applied at the time of crown root initiation which is considered a critical stage. Saline water having an electrical conductivity of 8.6 dS rn- ’ and SAR 13.2 mmolf5 ll’.” was used for irrigation. The drainage conditions were represented by free or gravity drainage and a closed outlet at the bottom, designated, respectively, as drained and undrained lysimeters. A control treatment, irrigated with good quality water (EC,, 0.4 dS m- ‘> was also included, to provide potential yield of the crop. All the treatments were replicated three times in a completely randomised block design. Wheat (variety HD 2009) was sown in rows 20 cm apart after a presowing irrigation of 5 cm. Fertiliser N, P,O, and K,O were applied at 75 kg ha- ’, 60 kg ha-’ and 30 kgha-‘, respectively, at the time of sowing and N was again applied along with the first irrigation. A sizeable area surrounding the lysimeters was cropped uniformally with wheat in order to minimise any microclimatic variations and boundary effects. The
01
’
O-20 Soil
’
O-28 water
’
I
036
content
’
’
’
044
(cm3
Fig. I. Soil moisture characteristic
cm-3
1
curve.
’
0.52
B.K. Khosla, R.K. Gupta /Agricultural
Nov.
Fig. 2. Cumulative
Dee.
pan evaporation
Jon.
Water Munqement
Feb.
and rainfall distribution
32 (1997) 285-291
Mar.
281
Apr.
during the growth period
growth parameters recorded were the plant height, number of tillers, ear heads and their length, representing 1.6 m row length, in addition to the grain and straw yield. The water table was recorded in the undrained lysimeters by connecting a vertical transparent plexi glass tube to the bottom of lysimeters. Soil samples were obtained at the time of sowing and harvest in 20 cm increments to a depth of 180 cm and water content was determined gravimetrically. The samples were ground to pass through a 2 mm sieve and analysed for electrical conductivity in 1:2 soil water extract. The U.S. open pan evaporation and rainfall data were obtained from a nearby observatory. The cumulative pan evaporation and rainfall distribution during the growth period of the crop are presented in Fig. 2.
3. Results 3.1. Crop response The data on various growth parameters and yield as affected by the treatments are presented in Table 1. A higher grain yield was obtained with increased depth of irrigation and quantity of water applied in the drained lysimeters. But, in contrast, in the undrained conditions, the yield showed a decline due to larger irrigation depth increments of 7 cm and 9 cm depth. Although the treatment differences were statistically non-significant, the relative yield (taking the grain yield obtained in the T, treatment as 100%) was increased by nearly 20% in T4. compared with the T, treatment in the drained conditions. In the undrained conditions, the yield was rather more in the case of smaller (T,) than the larger irrigation depth increments (T, treatment). The variations in yield were also reflected in the growth parameters and the yield bearing attributes. The plant height was lowered significantly in the T, treatment, compared with the control. This indicated that in the case of impeded drainage, the plant growth was affected to a
288
B.K. Khosla, R.K. Gupta /Agriculturul
Table 1 Growth parameters Treatment
Wuter Munagemenr 32 (1997) 285-291
and yield as affected by various treatments
Plant height (cm) Days after sowing
Effective tillers
Number of ears
Ear length (cm)
(g)
Relative yield (%)
Grain yield
52
77
94
T, T, T3 T4 Undrained
36.6 34.9 36.3 35.3
66.9 64.2 68.1 66.1
87.6 79.3 86.8 85.6
225 196 217 248
201 163 165 202
10.4 10.0 10.1 10.3
206 161 176 206
100 78 85 99
T, T6 T, CD (0.05)
37.4 37.8 28.9 4.1
67.3 68.2 58.5 3.4
86.9 87.8 77.0 7.3
179 195 168 47
152 174 140 33
9.7 10.0 9.6 0.6
183 157 162 NS
89 76 79
T, represents
control.
Drained
greater extent by larger irrigation depth increments. Similarly, the number of tillers and earheads were observed to be higher in the drained lysimeters and increased with depth of irrigation but showed a significant reduction in the T, treatment, representing undrained conditions. 3.2. Fluctuations
in water table
The fluctuations in water table depth during the growth period are shown in Fig. 3. The mean water table depth, standard deviation and coefficient of variation for selected
O-
40 Y 9 $g
80-
$ e B
120 -
P 160 -
200-
Fig. 3. Fluctuations
in water table depth (arrows indicate the timings of irrigation).
B.K. Khosla, R.K. Gupta/Agricultural
Water Management 32 (1997) 285-291
289
Table 2 Mean water table depth, standard Treatment
Days after sowing
deviation
and coeffkient
of variation
Mean water table depth km)
Standard deviation
Coefficient of variation (%)
TS
27 39 59
83 130 176
29.5 14.9 4.5
35.4 11.4 2.6
Tb
27 39 59
140 157 188
25.8 15.5 2.6
18.4 9.9 1.4
T,
27 49 98 110 125 136
6 102 I8 124 42 149
3.4 7.3 6.0 13.1 26.5 15.1
53.7 7.2 34.1 10.6 62.7 10.1
days are presented in Table 2. The water table depth showed a sharp rise in the undrained lysimeters, particularly when the irrigations comprised a larger depth increment. In T, treatment, when 9 cm depth of water was applied at each irrigation, the average rise of water table during the various irrigation cycles was to the extent of 16 cm cm-’ of water applied. The sharp rise in water table was followed by an initial rapid decline, which resulted mainly due to the evapotranspiration losses. This indicated that in shallow water table conditions, application or withdraw1 of water can result in a highly disproportionate rise as well as fall in water table. Gillham (1984) also observed a high sensitivity of water table to irrigation and evapotranspiration events and attributed it to an increase in the gas phase pressure in the unsaturated zone above the water table during the infiltration process, and the variable specific yield which decreased as the water table approached ground surface. The standard deviation and coefficient of variation (Table 2) tended to be higher when water table was at shallow depths following irrigation cycles and the values decreased with lowering of the water table depth.
4. Discussion The reduction in growth as well as grain yield of wheat during saline water irrigation in the undrained lysimeters was mainly associated with larger irrigation depth increments and due to the sharp rise in water table depth. It was seen that in the case of T, treatment the water table remained within 50 cm depth for a cumulative period of 18 days during the growth period of the crop. The occurrence of saline water table at rather shallow depths limited the proliferation of roots to lower depths and the soil water uptake was, thus, adversely affected. Chaudhary et al. (1974) observed that an increase
290 Table 3 Cumulative
B.K. Khosla, R.K. Gupta/Agriculturul
soil water depletion
Water balance components
(cm)
Initial soil water content Soil water content at harvest Depth of irrigation water applied Rainfall Cumulative soil water depletion
Water Management
32 (1997) 285-291
in 0- 180 cm depth Drained lysimeters TZ
T,
43.6 3 I .9 25.0 6.8 43.5
52.6 42.0 33.0 6.8 50.4
Undrained
51.2 39.0 32.0 6.8 5 I .o
lysimeters
TX
T6
T,
60.2 45.8 25.0 6.8 46.2
55. I 47.3 33.0 6.8 41.6
61.3 55.7 32.0 6.8 44.5
in salinity of ground water caused greater reduction in wheat yield with shallow than with deep water table, and the total water use was decreased from 58.8 cm when the water table was at 150-52.9 cm when the water table occurred at 60 cm depth. The cumulative soil water depletion was also calculated in the present study from the water balance components and is presented in Table 3. The values were in general higher for the drained as compared to the undrained conditions. It was only when water was applied in smaller depth increments (T,) that the soil water depletion tended to be more in the undrained than the corresponding T, treatment in the drained lysimeters. It was earlier pointed out (Shainberg and Shalhevet, 1984) that a higher frequency during saline water irrigation resulted in higher yield. A relatively greater reduction of yield in the undrained, compared with drained conditions, may also be related to higher accumulation of salts at the surface in the undrained lysimeters.
5. Conclusions The study indicated that the growth and yield of saline water irrigated wheat was affected to a greater extent in the undrained than the drained conditions, particularly when the irrigations comprised a larger depth increment, as these resulted in a sharp rise in water table. The rise as well as fall in water table during irrigation cycles, when drainage was lacking, showed a high sensitivity and were also highly disproportionate to the depth of irrigation and the evapotranspiration events. Although, with smaller depth of water applied more frequently, the yield tended to be higher in the undrained conditions, and considering the usual limitations of surface irrigation to apply water in smaller depth increments, improved drainage is imperative for cropping in shallow and saline water table conditions.
Acknowledgements Thanks are due to Arjen Kumar for providing the technical help, R.K. Madaan typing the manuscript and Purshotam La1 for preparing the figures.
for
B.K. Khosla, R.K. Guptu /Agricultural
Water Management
32 (1997) 285-291
291
References Bhumbla, D.R., 1981. Land and water management and agricultural production in India. J. Indian Sot. Soil Sci., 29: 403-418. Chaudhary, T.N., Bhatnagar, V.K. and Prihar, S.S., 1974. Growth response of crops to depth and salinity of ground water, and soil submergence. 1. Wheat (Tritium aestiuum L.) Agron. J., 66: 32-35. Gillham, R.W., 1984. The capillary fringe and its effect on water-table response. J. Hydrol., 67: 307-324. Shainberg, I. and Shalhevet, J. (Editors), 1984. Soil salinity under irrigation processes and management. Springer-verlag, New York, pp. 349. Szabolcs, I., 1975. Present and potential salt-affected soils-an introduction. FAO Bull. 31. Prognosis of salinity and alkalinity, pp. 9-13.