Simple Approaches to Quantify Yield Production and Soil Responsibility to Different Water Qualities and Moisture Depletion

This study is an attempt to quantify the effect of different water qualities interacted with different moisture
depletion levels on crop yield and leaching requirement for salt affected soil. Barley crop was cultivated on sandy soil
as a pots experiment in the open field, in Ismailia, Egypt. Three water qualities were collected from different resources
to represent three different water qualities: 1) Nile water, 0.4 dS m-1, 2) Salam Canal, 0.8 dS m-1 and 3) Diluted Sea
water, 7.4 dS m-1. Winter barley has been irrigated with the three different waters, where each type was applied under
three different levels of soil moisture depletion: 25 %, 50 % and 75 % of soil field capacity. An empirical model to
predict yield production was developed and evaluated in comparison to some common models such as models of
Stewart and Maas-Hoffman's models. The results showed that the suggested model could be used as reliable approach
to predict the relative yield of barley cultivated in sandy soil under different water salinities and soil moisture depletion
levels, as well as the leaching requirement of such salt affected soils irrigated with saline water. The validation of the
common used Hoffman's equation for leaching requirements, LR, had been tested based on leaching curve experiment.
The results indicated that the developed model for yield prediction may be successfully adapted to estimate the relative
yield as a function of both water salinity and depletion level of soil moisture. Based on the data of leaching experiment
a relative over-estimation of the LR was obtained using Hoffman's equation compared to that estimated from Oster's
equation. The amounts of water applied based on Oster's equation could be reduced to about one-third of that calculated
according to Hoffman and led to the provision of large amounts of water available for irrigation.