Effect of tillage on crack formation and water losses during fallow and pre-saturation period in irrigated rice lands
1995
Cabangon, R.J. | Bui Duc Qut | Pasuquin, E.M. | To Phuc Tuong | Quick, G.R. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Irrigating cracked, previously puddled soil involves considerable water losses due to water flow through cracks, bypassing the soil matrix (bypass flow). A field experiment was conducted to compare the effects of tillage methods on crack formation and water losses during the fallow period and pre-saturation irrigation. Rod cultivation was carried out by an implement (rod cultivator) which consists of a rotating horizontal rod attached to a hand tractor that cuts the top soil and subsoil. The four treatments, T1=untilled; T2 = rod cultivation when soil strength (P) at 2.5 cm depth, measured by a penetrometer, was 10 kg/sq cm; T3 = rod cultivation when P = 14 kg/sq cm; T4 = rotovated, were arranged in randomized complete block design with four replications. Rotovation and rod cultivation (T3) treatments were done when soil moisture content at the 0-10 cm soil layer was 0.38 while rod cultivation (T2) was done at 0.43 soil moisture content. Cracks reached depths at 110, 97, 102, and 98 mm from soil surface in T1, T2, T3, and T4, respectively. Crack depth at T1 was significantly higher than the tilled treatments. Maximum difference was observed at 20 days after tillage. Evaporation at 0-30 cm depth in T1 was significantly more than in other treatments during drying. T2 and T4 reduced bypass flow losses by 42 and 37 percent, respectively as compared to T1. Rotovation and rod cultivation at low soil strength are potential methods in reducing evaporation and bypass flow losses in irrigated puddled ricelands
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