Influence of microclimate on crop growth, soil respiration and carbon sequestration under varied agronomic management in sali paddy in Assam

A field experiment was conducted in 2016 and 2017 in Golaghat district of Assam, India to find out the influence of varied crop microclimate imposed by two crop establishment techniques of rice viz. System of rice intensification (SRI) and conventional, transplanted on 26^th June, 10^th and 25^th July at four different hill densities (20cm x 10cm, 20cm x 20cm, 25cm x 20cm & 25cm x 25cm) on crop performance as well as soil respiration, and carbon influx in the kharif paddy. Crops grown under SRI showed enhanced plant growth parameters such as plant height, tillers number per square meter in comparison to conventional establishment throughout the growing period. Regardless of crop establishment techniques and hill densities, early transplanted crops showed better growth parameters and grain yield. Similarly, with the increase in hill density, crop performance in terms of growth and yield was found to be inferior while the wider hill density recorded improved growth traits which resulted in increased yield. SRI establishment also owed significantly superior grain yield over the conventional one. Significantly greater emission of CO₂ measuring 455.28 mg CO₂ m^-2 d^-1 higher than that of conventional one was recorded under SRI establishment. SRI crops at wider hill density recorded appreciably higher soil organic carbon (SOC) build-up which was found gradually decreasing towards closer density, where as in conventional establishment it was significantly lower at wider spacing (25cm x 20cm and 25cm x 25cm). The study also indicates considerable impact of crop microclimate on optimal carbon farming in rice cultivation.