Effect of tillage on soil and crop properties of wet-seeded flooded rice

No-tillage (NT) is an alternative cropping system for saving costs and conserving soils relative to conventional tillage (CT). However, NT effects on paddy soil and rice growth are still controversial or not fully understood. A fixed field experiment was conducted to compare soil and crop properties between NT and CT wet-seeded flooded super hybrid rice in Changsha, Hunan Province, China. After 6 years of continuous cropping, NT had higher contents of active organic carbon, NaOH hydrolysable N and NH4OAc extractable K and higher activities of invertase, unease and acid phosphatase at 0-5 cm soil depth, higher bulk density at 5-10 cm soil depth, and higher contents of double acid Pat 5-10 cm and 10-20 cm soil depths. NT or associated soil compaction caused an adverse root environment for NT rice at early growth stage, which resulted in a lower capacity of photosynthetic carbon metabolism and consequent reductions in number of tillers and aboveground biomass accumulation before heading. However, no reductions were observed in total aboveground biomass and grain yield in NT rice, because the negative effects of NT or associated soil compaction on aboveground biomass production before heading were compensated for by its positive effects on aboveground biomass accumulation after heading. On one hand, the reduction in growth before heading of NT rice made its population density lower but more suitable during heading to 20 days after heading, which led to a more appropriate leaf area index, a lower leaf senescence and a consequent increase in net assimilation rate. On the other hand. N uptake was delayed in NT rice, which was another critical factor in determining its low leaf senescence. Our study suggests that the negative effects of NT or associated soil compaction on crop growth at early growth stage do not necessarily become concerns in NT wet-seeded flooded rice production. (C) 2012 Elsevier B.V. All rights reserved.