Modification of hydrothermal regimes under bed planted wheat

Abstract

In a study on sandy loam soil of Indian Agricultural Research Institute (IARI) farm of New Delhi, soil hydrothermal environment under bed planted wheat was compared with conventionally flat planted wheat for evaluating the suitability of bed-planting system for the semiarid climate of this region. The soil temperature and water contents of the 0–20 cm soil profile under bed and conventional planting were monitored during drying cycle after 2nd and subsequent irrigations. Results revealed that mostly soil water content under bed planting was lower by 0.5–1% (w/w) than under conventional system mainly due to lower application of irrigation water and because of more porous soil environment. But it was also noticed that by applying irrigation at 22 days interval, soil water under bed remained within the available soil water range. It was observed that under both methods of planting magnitude of the maximum temperature decreased with an increase in soil water content, but for both high and low soil water contents (SWC), the temperatures were higher by 0.5–3 °C at the surface and subsurface (up to 20 cm) under bed than under conventional flat planting. Soil temperature data collected at 2 h interval during the day to monitor the maximum soil temperature showed that magnitudes of the peak at all depths were higher in bed planting and their arrival times were also earlier than in conventional planting. Again, at low SWC, peak soil temperature at the surface was near or higher than aerial temperature and at higher SWC, it was lower than aerial temperature. For similar aerial temperatures (30 °C), with an increase in SWC, both volumetric heat capacity and thermal diffusivity increased and their magnitude on bed was lower than that on conventional planting.