Zero tillage with wheat straw on the soil surface as such (ZTsas) improved soil fertility and cotton yield. Field experiment was carried out to study the impact of conservation tillage practices and N management on Bt. cotton for five years (2011–2012 to 2015–2016). Tillage methods kept as main treatments (zero tillage plus wheat straw as such on the soil surface {ZTsas} and minimum tillage plus wheat straw incorporated {MTsi}. In sub-plot four N doses were N50, N100, N150, and N200 kg ha–1. Cotton yield and fiber characteristics of Bt. cotton (CIM-616) were examined during the study years. ZTsas treatments had more bolls per plant and heavier weight per boll than those of the MTsi treatments. Averaged over years, ZTsas gave significantly higher seed cotton yield than MTsi. The treatments N150 gave significantly better seed cotton yield than the other treatments. ZTsas with N150 resulted in higher cotton yields than the MTsi plots. ZTsas had accumulated higher soil organic matter and total soil N compared to MTsi. Compared to MTsi plots, the ZTsas treatments had greater amount of water stable aggregates and mean weight diameter. The N150-200 plots produced higher percentage of WSA and MWD than other plots. Favorable soil physical properties have contributed to enhanced seed cotton yield in ZTsas with N150 than in MTsi. ZTsas treatments had higher 100-cotton seed weight, GOT, fiber length, and strength at N150-200 compared to other tillage system. The fibre fineness revealed that ZTsas had no unfavorable impact on fiber fineness compared to MTsi. This study reveals that Bt. cotton can be grown under ZTsas systems with optimum N fertilizer.

Keywords: Bacillus thuringiensis, conservation tillage, nitrogen, aggregate stability, yield and quality, TSN and SOM