In the NT and BCT systems, the BVD-523 clinical trial amounts of fertiliser N applied to wheat were a, b 0 (N0), c, d 50 (N50) and e, f 100 (N100) kg N/ha. Indicators: wheat (W) and chickpea (CP) yield, water-use efficiency (WUE), gross margin (GM) and soil organic carbon in 0–0.3-m depth (OC) Specifically, NT performed better than CT and BCT in all sustainability indicators, except when no fertiliser N was applied to wheat (Fig. 1; Table 1). Enhanced sustainability with NT, was first of all, a consequence of soil water conservation
with the residue mulch. Residue retention also improved levels of OC, except when no fertiliser N was applied. The minimum N rate required for the NT system to outperform the reference PD-0332991 nmr system was N25 (not shown). When no fertiliser N was applied, N limitations reduced wheat yield, GM and WUE (but not OC), and, ultimately, the sustainability of all tillage systems. However, chickpea benefited somewhat from residual soil moisture left from a preceding N-limited wheat crop, which explained why the chickpea indicators yield, WUE and GM performed slightly better as in the reference system (CT with N50). The modelling showed that burning wheat stubble in the BCT system constrained Z-VAD-FMK molecular weight sustainability by reducing
revenue (consequently GM) at N rates of N0, N25 and N50 (Fig. 1d). Revenue was lost primarily by missing out on the productivity benefits from soil water conservation and by not selling straw as animal feed (Table 1). Application of high N rates (N75 and N100) compensated for revenue losses incurred by burning wheat stubble (Fig. 1f). Detailed diagnostic
evaluations of causes and effects, and variability and trend of the indicator values complemented the integrated assessment using sustainability polygons. These are presented in Appendix C. Table 1 Average grain yield, water-use efficiency (WUE), gross margin Rho (GM), gross revenue (GR) from grain and straw sales, and soil organic carbon (OC) in wheat–chickpea rotations (1980–2005) simulated with conventional tillage (CT), burn-conventional tillage (BCT) and no-tillage (NT) Wheat Chickpea Rotation CT BCT NT CT BCT NT CT BCT NT Yield (t/ha) 1.70 (0.93) 1.73 (0.94) 2.80 (0.75) 0.83 (0.36) 0.82 (0.37) 1.66 (0.37) WUE (kg/ha/mm) 5.67 (2.66) 5.72 (2.69) 11.95 (2.93) 2.79 (0.77) 2.76 (0.78) 6.00 (1.07) GM (€/ha) 309 (204) 237 (183) 431 (146) 230 (119) 227 (121) 463 (119) GR grain (€/ha) 370 (202) 375 (203) 607 (162) 295 (128) 292 (131) 589 (132) GR straw (€/ha) 77 (24) 0 0 13 (4) 13 (4) 0 OC (t/ha)a 20.00 (0.63) 19.24 (0.49) 20.70 (1.52) Results are given for an N fertiliser rate of 50 kg N/ha applied at wheat sowing. Results for CT are those of the reference system (details are given in text).