Changes in DTPA Extractable Copper, Iron, Manganese and Zinc Following Waterlogging and Application of Sewage Sludge and Animal Manure in Two Different Types of Soil

The effects of waterlogging, sewage sludge and animal manure on the concentrations of DTPA extractable copper, iron, manganese and zinc were investigated in two different types of soil. A factorial experiment based upon a completely randomized design of two replications containing duration of waterlogging at six levels (0, 1, 3, 7, 15, 30 days), source of organic fertilizer at three levels (control, animal manure, sewage sludge) and soil type at two levels (one alkaline loamy sand soil and one acidic clay soil) was carried out under laboratory conditions. Equal quantities of animal manure and sewage sludge, at a rate of 30 grams per kilogram of soil, were added. During waterlogging period, the water level was maintained 3 cm above the soil surface. The results showed that by increase in the duration of soil waterlogging, the DTPA extractable Fe and Mn in both soils and for all treatments increased significantly with the degree of increase in acidic clay soil being more than that in alkaline loamy sand soil. Following waterlogging, manganese reduction rate was more than iron in acid clay soil for all treatments except control. By increasing the duration of soil waterlogging, the DTPA extractable Cu and Zn for both soils and in all treatments decreased significantly with the level of decrease in acidic clay soil being higher than that in the alkaline loamy sand soil. By application of sewage sludge and animal manure, the DTPA extractable Cu, Fe, Mn, and Zn in both soils increased significantly with the level of increase being dependent on the duration of soil waterlogging. There existed significant regression equations between the duration of soil waterlogging and concentrations of DTPA extractable Cu, Fe, Mn, and Zn in both soils and for all treatments. Following waterlogging, the pH in an alkaline soil increased for all the treatments. The pH in an alkaline soil increased following the application of animal manure while being decreased following application of sewage sludge.