Impact of modified microclimate on the performance of green gram under different planting systems in Upper Brahmaputra Valley Zone of Assam
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Date
2021
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AAU, Jorhat
Abstract
A field experiment was conducted during the summer, 2021 in the Instructional-Cum-Research (ICR) Farm of AAU, Jorhat to study the Impact of modified microclimate on the performance of green gram under different planting systems in UBVZ Assam. The variety SGC-16 was grown in a split-plot design with 3 dates of sowing (D1-20th February, D2-6th March, and D3-20th March) in main plots and three planting systems (P1 – ridge and furrow, P2 – raised bed with two rows in bed and P3 –flat bed ) in sub-plots, with three replications following recommended agronomic practices. Microclimatic parameters such as soil temperature (10 cm depth) and soil moisture content at two depths (0 - 15 cm and 15 - 30 cm) were recorded at regular intervals. The different components of photo-synthetically active radiation (PAR), viz., incident (IPAR), and transmitted (TPAR) were recorded at 7 days intervals using line quantum sensor (Model LQM-70-10) at local noon time (11:30 AM). Crop growth parameters viz., plant height, leaf area index and dry matter accumulation, phenological observations and yield attributing characters, and seed yield were recorded. Agro-climatic indices viz., growing degree day (GDD), heliothermal unit (HTU), phenothermal index (PTI), and heat use efficiency (HUE) for biomass and seed yield were computed following standard procedures. The daily maximum temperature never exceeded 37.6°C, but the daily minimum temperature went below 20°C (up to 12.4°), which was detrimental to the crop. The average soil moisture content in the upper 30 cm soil profile was the highest in the D3 (80.39 mm), followed by D2 (75 mm) and D1 (66.4 mm). As compared to P3, the decrease in weekly evening soil temperatures under P1 and P2 was up to 2.1 and 1.4°C, respectively. Incident PAR (IPAR) during the crop growth season varied from 712 to 1721 μ mol s-1 m-2. In all dates of sowing and planting systems, the lowest transmitted PAR was recorded in the case of D3 date of sowing and in P1, when the crop was with full canopy coverage. The crop took 4 to 11 days, 28 to 35 days, 34 to 43 days, 39 to 50 days, and 62 to 75 days to attain the different phenological events, such as emergence, bud formation, flowering, pod initiation, and physiological maturity, respectively under different sowing dates and planting systems. Irrespective of sowing dates mean maximum leaf area index was recorded in P1 (2.06), followed by P2 (1.91) and P3 (1.77). The biomass production at maturity was highest in D3 (15.6 g plant-1), which decreased in earlier dates of sowing, while it was highest under P1 (14.6 g plant-1), followed by P2 (13.4 g plant-1) and P3 (11.6 g plant-1), irrespective of sowing dates. The seed yield of green gram cultivar SGC-16 sown under different sowing dates and planting systems ranged from 286.3 to 681 kg ha-1 with an overall mean of 509.8 kg ha-1. Irrespective of sowing dates, the highest GDD accumulation in the entire growth period was recorded under the P1 (1010°C day) system, followed by P2 (973°C day) and P3 (930°C day). The accumulation pattern of PTU by the crops under different treatments was similar to that of GDD. HUE for total biomass production and seed yield ranged from 2.61 to 4.01 kg ha-1°C-1 and 0.38 to 0.65 kg ha-1°C-1, respectively. Regression studies showed that there were linear significant relationships between total biomass, seed yield, and max LAI with iPAR .Correlation studies between seed yield, and thermal indices confirmed the existence of a significant and positive correlation between them.