DYNAMIC EQUILIBRIUM FOR DETERMINING DRAIN SPACING FOR DIFFERENT SOILS

ABSTRACTThe main purpose of drainage is to provide a root environment that is suitablefor the maximum growth of plants. This study is conducted to find the drain spacingusing dynamic equilibrium concept for four different soils with different drain depths,and compare the results with those obtained for the peak irrigation period and the steadystate equations using arithmetic, geometric and exponential means.The study included soil texture and hydraulic conductivity tests for four differentsoils. The drainable porosities of soils were found from especial curves. Two crops werechosen(maize and cotton) and their water requirement and growing season wereestimated from previous studies. A computer program was made to obtain the drainspacing using the previously mentioned methods. The drain spacings obtained with thedynamic equilibrium concept were higher than those obtained with the peak irrigationperiod .The difference in drain spacing becomes more evident with greater depths andhigher values of drainable porosity. The drain spacing required for maize is higher thanthat for cotton. This means that the spacing is affected by both soil type and crop