The detrimental effects of rice-based cropping systems in South Asia, such as excessive water use, environmental pollution and poor nutrient use efficiency have given impetus to develop more sustainable cropping systems. Soybean meets most of its N requirement by biologically fixed nitrogen (BNF) and requires significantly less irrigation water than rice. Under the umbrella of the CRP D15009 on conservation agriculture from the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture (http://www-naweb.iaea.org/nafa/swmn/applied-research.html), two 4-yr field experiments were conducted to investigate the impacts of integrated nutrient, crop residue and no-tillage management (conservation agriculture) on the productivity and sustainability of soybean-wheat and soybean-rapeseed cropping systems. Sixteen treatments (split-split plot design) consisted of a control, 100% of recommended fertilizer (Soybean: 20kg N + 60kg P2O5 ha-1; Wheat: 120kg N + 60kg P2O5 ha-1; Rapeseed: 100kg N + 30kg P2O5 ha-1), 100% NP + 10t ha-1 farmyard manure (FYM) and 125% NP with and without crop residues in both conventional-tillage (CT) and no-tillage (NT) systems. Soybean, wheat and rapeseed residues (3, 6 and 4t ha-1, respectively) were incorporated in CT and spread on the soil surface in NT. BNF, N-balance and soil moisture were screened using nuclear and isotopic techniques (15N-dilution technique, 15N-balance and neutron probe). The results revealed that soybean and wheat yields were comparable under both CT and NT (without crop residue), suggesting that these crops could be grown under NT without any yield loss. The application of 100% NP + 10t FYM ha-1 [GD1] produced significantly higher soybean yields and had residual effect on wheat and rapeseed, and BNF by soybean ranged from 79-93kg N ha-1. Minimum soil disturbance and retained crop residue conserved soil moisture, enhanced BNF (soybean) by 20%, and improved soil health (mineralizable and microbial N, labile carbon pools and water stable aggregates). However, surface-retained crop residue reduced surface soil temperature, hence delayed winter-wheat's germination, slowed down growth at early stage, reduced N uptake, enhanced fertilizer N losses and consequently reduced wheat yield by about 10%.[GD2]
[GD2]Seems to be contradictory with your statements above that there was no difference between yields. Corrected
[GD2]Seems to be contradictory with your statements above that there was no difference between yields.