Resumen de Tillage and irrigation effects on crop yields and soil properties under the rice�wheat system in the Indian Himalayas

Rajasri Bhattacharyya, S. Kundu, S.C. Pandey, K.G. Singh, H.S. Gupta

• Conservation tillage systems generally improve soil organic C (SOC), plant available water capacity (PAWC), aggregation and soil water transmission. A field experiment was conducted for 4 years (2001�2002 to 2004�2005) to study tillage (conventional tillage (CT) and zero tillage (ZT)) systems. The selected irrigation treatments were at four levels (I1: pre-sowing (PS), I2: PS + active tillering (AT)/crown root initiation (CRI), I3: PS + AT/CRI + panicle initiation (PI)/flowering (FL), and I4: PS + AT/CRI + PI/FL + grain filling (GF)), applied at the critical growth stages on rice (Oryza sativa L.) and wheat (Triticum aestivum L.). Their effects on direct seeded rice productivity and soil properties (SOC and selected physical properties) after rice and wheat harvest were investigated. Soil organic C contents after rice and wheat harvest in the 0�15 cm soil depth were higher under ZT than under CT. Soil organic C increased significantly with I2 over I1 for both crops and with I4 over I2 for the wheat crop. The PAWC was significantly higher with ZT than CT. Zero tilled and frequently irrigated plots showed enhanced infiltration characteristics (infiltration rate, cumulative infiltration and sorptivity) and saturated hydraulic conductivity. Both direct seeded rice and wheat yields were not significantly different in the plots under ZT and CT. There was a significant increase in both rice and wheat yields in the plots under I2 over I1. However, water use efficiency between irrigation treatments was not significantly different. Hence, under direct seeded rice�wheat system in a sandy clay loam soil of the sub-temperate Indian Himalayas, farmers may adopt ZT with two irrigations in each crop for optimum resource conservation.