EFFECT OF DIFFERENT DRAIN DEPTHS ON SOIL HYDROLOGY AND CROP PRODUCTION OF RICE AND WHEAT CROPS

Abstract

The present work was carried out during summer and winter seasons on rice and wheat crops cultivated in an open field at Zankalon area, Sharkia Governorate, Egypt, to study the effect of drain depth on soil hydrology, salinity and crop production of rice and wheat crops. Three drainage treatments were used i.e. conventional drainage depth (drain depth 1.20 m, T120), controlled drainage depth (drain depth 0.60 m, T60) and without drainage depth ( drain depth 0.0 m , T0 where the drain outlet was completely blocked) to achieve this target. The obtained results reveal that, the total amounts of irrigation water applied to different treatments during the growing season were arranged in a descending order: conventional drainage depth (T120) > controlled drainage depth (T60) > without drainage depth (T0) for both rice and wheat crops. Using T60 and T0 treatments for rice crop saved 32.7 and 49.7 % of the applied water as compared with the T120 treatment, respectively. The irrigation intervals were 2.0, 3.0 and 5.0 days for T120, T60 and T0 treatments, respectively. This means that, using T60 reduced the number of irrigations by 40 % which reduces the irrigation cost. On the other hand, there is a little difference between the total amounts of irrigation water applied to the different treatments cultivated with wheat crop. The total amounts of drainage water drained from the soil cultivated with rice crop at T120, T60 and T0 treatments were 2069.6, 1065.0 and 0.0 m3/fed, respectively, but at wheat crop they were 305.9, 292.1 and 0.0 m3/fed., respectively. Concerning the fluctuation of water table for wheat crop, the results emphasized that at T120 treatment, 80% of the measured water table levels were fluctuated within the depths of 50-75 cm, to >100 cm below soil surface. While, it never reached the depth of 0-20 cm below soil surface. Under T60 and T0 treatments about 90% of the measurements were fluctuated within the depths of 0-50 cm below soil surface during rice cultivation. On the other hand, 63% of the measured water table during the wheat growing season fluctuated at the depth less than 100 cm at T0 treatment. While, 85 % and 66 % from measured water table levels during the growing season were fluctuated at depth more than 1.0 m for T120 and T60 treatments, respectively. The values of relative ground water depths (RGWD) at rice were 1.3, 0.3 and 0.4 for T120, T60 and T0 treatments, respectively. Whereas, under wheat crop, they were 2.0, 1.8 and 1.4 for the same above mentioned treatments, respectively. It is clear that (RGWD) values were more than one at all wheat treatments, and also in case of T120 treatment cultivated with rice. This may be attributed to the fact that the fluctuating water table rises to the soil surface after irrigation but soon it falls down to the drain depth. The highest grain yield of both rice and wheat were obtained from plant grown under the T120 treatment. This means the effect of drain depth on grain yield was positive. Crop water productivity (CWP) values for rice grain were 0.75, 1.34 and 1.68 kg/m3 for conventional, T60 and T0 treatments, respectively. Whereas, the (CWP) values for the wheat grain, were 1.01, 0.9 and 0.90 kg/m3 for the above mentioned treatments respectively. Using the T120 treatment, the obtained results proved that more salts were leached from the soil to drainage water followed by T60 for both crops under the study. On the other hand, more salts were accumulated in soil layers during the growing season in both crops in the soil of T0 treatment.