Assessment of performance of potato crop under modified microclimates in rice based cropping system of Upper Brahmaputra valley zone of Assam

A field experiment was conducted during rabi, 2017-18 in Assam Agricultural University, Jorhat to identify appropriate adaptive strategies for combating ill effect of heat and moisture stress through modifying microclimate in rice-potato double cropping system. The potato variety – Kufri Jyoti was planted in split plot design with 3 dates starting from 10 November at 10 days interval (main plots) and three mulching treatments with water hyacinth, black polythene and without mulching (sub-plots) following recommended agronomic practices. The study revealed that there were 11.8 and 7.0 per cent increase in average soil moisture content under water hyacinth and black polythene, respectively as compared to non-mulched treatment. On the other hand, soil temperature was 0.5 to 1.5 °C (morning) and 1.1 to 2.3°C (evening) lower under water hyacinth, but 1.2 to 2.1°C (morning) and 1.7 to 2.6 (evening) higher under black polythene as compared to non-mulched crop. In all planting dates, crop growth parameters like LAI and biomass production were observed to be highest under water hyacinth, followed by black polythene and without mulching. Among the mulching treatment the highest and lowest tuber yield was recorded under water hyacinth (120.81 q ha-1) and non-mulched treatment (85.0 q ha-1), respectively in all planting dates.It was found that the tuber yield was significantly and positively correlated (at 5% level) with the average soil moisture retention (mm) in upper 30 cm layer of soil during tuber formation to physiological maturity (r =77*). Increase in tuber yield (up to 42.2%) under water hyacintheven in case of late plantings (beyond 10 November) was probably due to increase insoil moisture retention (8.1 to 15.7 %) and reduction of soil temperature (1 to 1.8°C) under water hyacinthwhich endowed with favorable hydrothermal environment as compared to that under black polythene and non mulched treatment.