Optimum time of sowing for rainfed winter chickpea with one-pass mechanised row-sowing: an example for small-holder farms in north-west Bangladesh

The time of sowing chickpea (Cicer arietinum L.) in the High Barind Tract of north-west Bangladesh is critical to crop success. To ensure adequate emergence and subsequent crop growth, chickpea relies on residual soil moisture stored in the profile after rice (Oryza sativa L.) cultivated in the preceding rainy season. With the development of mechanised, one-pass minimum tillage sowing, the time between rice harvest and chickpea sowing is decreased, and temperature constraints that limit biomass and/or pod formation and filling may be avoided. Minimum tillage may also limit evaporation from the soil surface compared with traditional, full cultivation procedures. The objective of this study was to identify the optimum sowing time to achieve adequate crop establishment and limit exposure of the chickpea crop to terminal drought and heat stress later in the growing season. Over three experimental seasons, chickpea sowing dates were spread from 22 November to 22 December. Soil water content, crop growth and temperature were monitored to determine the optimum sowing time. Over all seasons and sowing dates, the volumetric soil water content in the seedbed under minimum tillage remained within 17-34%, a range non-limiting for chickpea establishment in glasshouse and field experiments. Late planting (after 10 December) exposed seedlings to low temperatures (35°C), resulting in unfilled pods and depressed grain yield. The preferred sowing time was determined to be 30 November to 10 December to reduce the risk of high temperatures and low soil water content during chickpea reproductive growth causing terminal heat and drought stress, respectively. Mechanised sowing in one operation allows farmers to optimise their time of sowing to match seed requirements for soil water at emergence and may assist farmers to avoid temperature stresses (both low and high) that constrain chickpea vegetative and reproductive growth