Short Response of Spring Wheat to Tillage, Residue Management and Split Nitrogen Application in a Rice-Wheat System

A field experiment was conducted to study the impact of tillage, crop residue management and nitrogen(N) splitting on spring wheat(Triticum aestivum L.) yield over 2 yr(2010-2012) in a rice(Oryza sativa L.)-wheat system in northwestern Pakistan. The experiment was conducted as split plot arranged in randomized complete blocks design with three replications. Treatments comprised six tillage and residue managements: zero tillage straw retained(ZTsr), zero tillage straw burnt(ZTsb), reduced tillage straw incorporated(RTsi), reduced tillage straw burnt(RTsb), conventional tillage straw incorporated(CTsi), and conventional tillage straw burnt(CTsb) as main plots and N(200 kg ha-1) was applied as split form viz., control(no nitrogen & no splitting, N0S0); 2 splits of total N, half at sowing and half at the 1st irrigation(i.e., 20 d after sowing(DAS))(NS1); 3 splits of total N, 1/3 at sowing, 1/3 at the 1st irrigation, and 1/3 at the 2nd irrigation(NS2); 4 splits of total N, 1/4 at sowing, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation(45 DAS), and 1/4 at the 3rd irrigation(70 DAS)(NS3); and 4 splits of total N, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation, 1/4 at the 3rd irrigation, and 1/4 at the 4th irrigation(95DAS)(NS4) as sub plots. The results showed that the most pikes m-2, grains/spike, 1 000-grain weight, grain yield, and N use efficiency(NUE) were obtained at zero tillage, straw retained and 4 splits application of total N(i.e., at sowing 20, 45 and 70 d after sowing). The results indicated that ZTsr with application of 200 kg N ha-1 in 4 equal splits viz. at sowing 20, 45 and 70 d after sowing is an appropriate strategy that enhanced wheat yield(7 436-7 634 kg ha-1) and N efficiency(28.6-29.5 kg kg-1) in rice-wheat system.