Effects of tillage intensity, planting time and nitrogen rate on wheat yield following rice.

摘要

Puddling coarse-textured soils for rice culture in the irrigated tract of the Indo-Gangetic Plains causes high soil strength in the upper layers. This may adversely affect growth and yield of following upland crops. It is possible that no-tillage (NT) in wheat (without residues of preceding rice crop) could aggravate this problem and reduce fertilizer nitrogen (N) use efficiency. In certain production scenarios, NT has been reported to be advantageous because it allows for earlier planting of wheat by eliminating delays caused by tillage. This study examined the combined effects of two crop establishment options for wheat in relation to fertilizer N and planting time following puddled rice cultivation in an irrigated environment of Punjab, northwest India. Combinations of two establishment systems, NT-direct planting and conventional-tillage (CT) with soil disruption to 0.10 m depth in main plots, with two N rates, 120 and 150 kg ha-1 in subplots, were evaluated. Variation in planting time, 31 October (D₁) and 7 and 10 November (D₂), was used to evaluate effect of planting-earliness. Under D₁ in NT, grain yield of wheat was comparable to that under D₂ in CT. However, under no advancement of wheat planting in NT, grain yield was 0.2-0.3 t ha-1 less than that in CT. This yield reduction in NT could be overcome by adding 30 kg ha-1 more fertilizer N suggesting that tillage enhanced N use efficiency. These tillage gains are ascribed to the greater extraction of profile stored and applied water and nutrients because of denser crop rooting caused by reduction in soil strength and less weed competition. Higher N use efficiency in CT suggests that farmers could achieve fertilizer N savings with this system. Comparing the tillage systems showed that NT was more cost-effective than CT even after accounting for the cost of additional fertilizer N (saving of Rs. 1685 ha-1) to overcome associated yield penalties under no advancement in planting time.