干旱区生态环境知识资源中心

In the Indo-Gangetic plains of south Asia, conventional tillage (CT) and removal of crop residues have been the major cause of declining soil fertility. While zero tillage (ZT) farming combined with retention of crop residues as surface mulch are well known to improve soil quality and crop productivity in different climatic zones, only limited knowledge exists on the performance ZT technology in the Indo-Gangetic plains. A field study was conducted under subtropical arid climate to elucidate short-term effects of different tillage, residue mulch and N fertilizer regimes on the productivity of irrigated maize grown for five cropping seasons. Treatments included CT and ZT; each with mulch (M+) or without mulch (M-), and with N (N+) or without N (N-). Fate of the fertilizer-N applied to the 5th maize crop was also investigated using N-15 tracer. After five cropping seasons, soil organic C (SOC) in the arable soil layer was higher under ZT compared to CT (29% increase), under M+ compared to M- (16% increase) and under N+ compared to N- (13% increase). Highest SOC was recorded under ZT-M+-N+ treatment (19.1 Mg ha(-1)) and the lowest under CT-M--N- (10.7 Mg ha(-1)). Nitrogen application increased the grain yield; the increase was higher under ZT than under CT in three cropping seasons. Mulch application reduced the grain yield in four cropping seasons. During all growing seasons, the grain as well as total biomass yields were highest under ZT-M--N+. Recovery of the fertilizer-N in soil (0-100 cm depth) ranged from 28 to 39% of the applied with lowest recorded under ZT-M-. The fertilizer-N recovery in plant was highest (40%) under ZT-M-, whereas the total fertilizer N recovery in the soil-plant system was not influenced by tillage or mulch regimes. Plant-N derived from soil (Ndfs) was higher under ZT compared to CT (47% increase), and under M+ compared to M- (15% increase); the highest Ndfs was recorded under ZT-M- (31-68% increase). While mulch had no effect on the added-nitrogen-interaction, the latter was significantly higher under CT compared to ZT (65% increase). Results suggested that as compared to other tillage/mulch regimes, ZT without mulch produced similar or higher grain yield and showed highest fertilizer-N use efficiency in continuous maize cropping system under subtropical conditions prevailing in the Central Punjab, Pakistan.