Influence of seasonal variability and conservation tillage on flower production and boll retention of Bt cotton (Gossypium hirsutum)

An experiment was conducted at Central Institute for Cotton Research, Nagpur, Maharashtra, to monitor flower and boll production in Bt transgenic cotton (Gossypium hirsutum L.) hybrid (‘RCH 2 Bt. hybrid’) as influenced by climatic factors and conservation tillage practices in selected treatments. Two reduced tillage (RT) systems, with limited soil disturbance in the form of inter-culture operations (RT1) and no soil disturbance (RT2), were compared with the conventional tillage treatment (CT). The tillage treatments comprised subplots with and without green manure. Conservation-tillage treatments had 12–15% more bolls retained on a plant than the conventional tillage. Irrespective of the tillage systems, flower and boll production varied among years. Flower production correlated negatively with the maximum and minimum temperature (P<0.0001) and maximum and minimum relative humidity (P<0.001) during both the seasons. In general, sunshine hours and evaporation rate showed a non-significant positive correlation with flower production. In both the seasons, negative correlation was observed for boll production with maximum and minimum temperature (P<0.0001) and minimum humidity (P<0.40). Boll production correlated positively with evaporation rate, but the relationship was significant in the second season (P<0.01). Boll retention was 54.3% higher in the first season compared to 43.6% in the second season due to lower mean maximum and minimum temperature. In general, temperature, relative humidity and evaporation rate were positively correlated with the number of bolls shed. These results indicate that seasonal variability has a greater impact on flower and boll production, irrespective of tillage treatments. Conservation-tillage systems may modulate and modify the adverse climatic effects such as high temperature and increasing moisture stress.