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