YIELD OF WHEAT IS INCREASED THROUGH IMPROVING THE CHEMICAL PROPERTIES, NUTRIENT AVAILABILITY AND WATER PRODUCTIVITY OF SALT AFFECTED SOILS IN THE NORTH DELTA OF EGYPT

The lysimeter experiment was carried out twice in consecutive two years (2014-15 and 2015-16) at Sakha Agricultural Research Station, Kafrelsheikh, Egypt to study the effect of three irrigation levels water (i.e., 100, 110 and 120% field capacity (FC), two rates of gypsum (G) (i.e., 50 and 100% G) and three sources of nitrogen (90 kg nitrogen (N), 10 t compost (C) and 7.5 t C + 45 kg N (CN) fed(-1) (fed = 4200 m(2))) on grain yield of wheat, water relations and soil chemical properties. Water consumptive use (WCU) was markedly increased due to the increase of the level of irrigation, rate of gypsum (G) and CN source (7.5 t C + 45 kg N fed(-1)). Irrigation with water amount equal to 120% FC recorded the highest values of WCU 1433 and 1570 m(3)fed(-1) in both seasons. Water productivity (kg grain m(-3) water) for either water application (WA) in both seasons or WCU in the second season was decreased by increasing level of irrigation from 100 to 120% FC in the second season, while the inverse was true for WCU in the first season. The highest mean values of water productivity for WCU 1.816 and 1.791 kg m(-3) were obtained with the irrigation level of 120% FC in the first season and 100% FC in the second season, respectively. Gypsum rate and N source have an effect on the productivity of irrigation water (WP) for WA and WCU, where the highest mean values for both the two irrigations efficiency were recorded under 100% G requirements and CN (7.5 t C + 45 kg N fed(-1)). The interaction of 110% FC x 100% G x 7.5 t C + 45 kg N fed(-1) produced the highest values of WP for WA (1.245 and 1.374 kg grain m(-3) WA) in both seasons. Grain yield fedd.(-1) was increased significantly with the irrigation level from 100 to 120% FC in both seasons, G rate and CN source. Grain yield (GY) did not differ significantly due to the levels of irrigation water between 120 and 110% FC in both years. Application of 100% G and 7.5 t C + 45 kg N fed(-1) at any irrigation level were among those treatments having high GY, being insignificant. The mean values of electrical conductivity (acidity; ECe) and soil sodicity (SARe) were affected by irrigation treatments, G rates and nitrogen sources. A stronger reduction in soil ECe and SARe were recorded under the irrigation level of 120%FC, 100% G and 10 t compost in both seasons. While the soils ECe and SARe were increased by application of chemical N fertilizer alone or with compost. Therefore, it can be concluded that irrigation with water amount equal to 110 or 120% FC, 100% G requirements and 7.5 t C and 45 kg N fed(-1) was the best treatment for getting high GY, improving the soil chemical properties, nutrients availability and increasing the water productivity of salt-affected soil in North Delta of Egypt.