Limitation on Water Retention Improvement by Organic Fertilizer in Coarse Textural Soils

Abstract

Incubation of duck manure or composted filter pressed cake in sandy loam soil (Ban Bung soil series) or loamy sand soil (Thai Muang soil series) at ratio of manure to soil of 0:1, 0.25:1, 0.5:1, 0.75:1 and 1:1 (by volume) at 50% water holding capacity for 1, 2, 4, 8, 12 weeks caused 1) reduction in bulk density and 2) increasing in moisture content at -0.033 MPa as increasing rate of added organic matter. These effects maintained longer than 12 weeks. To improve water retention at -0.033 MPa from Pw = 10% up to Pw = 20%, for a sandy loam (Ban Bung soil series) needs organic matter addition at ratio about 0.4:1 to 0.5:1 while a loamy sand (Thai Muang soil series) needs as high as ratio 0.5:1 to 0.75:1, which is too high for cultural practice.