Managing impact of climatic vagaries on the productivity of wheat and mustard in India

Abstract

Wheat and mustard crop is highly vulnerable, particularly in the semi-arid and arid regions of India. The climate is warming through the processes such as CO₂ and changed pattern of temperature and precipitation resulting in heat and drought stresses, respectively. The effect of increasing temperature during grain filling stage of wheat causes substantial reduction in grain yield. The effect of low temperature (frost) during podding and seed development stage in mustard causes freezing injury in seeds and sizable reduction in seed yield.  In this review paper response of wheat and mustard crop to weather extremes and management practices such as time of sowing, selection of resistance cultivars, mulching, seed priming, foliar spray of salts, use of extra irrigation water, foliar spray of micronutrients, sprinkler, wind barrier etc. to mitigate the temperature and moisture stress effect on the productivity of wheat and mustard crop  have been discussed. Above ground dry weight of wheat and its rate decreased with increasing water stress at each stage. The averaged values of damage threshold temperatures  compiled from the literature were 31 °C for flowering and 35 °C for grain filling of wheat. Changes in average daily maximum temperature during flowering and grain filling had a negative effect on grain yield of 518 kg/ha and 1140 kg/ha, respectively for every 1 degree increase in average maximum temperature in South Australia. Temperature rise would be most harmful for the crop in eastern region, followed by central and northern India, where winter season temperature is comparatively higher than northern region. Rainfed mustard was less vulnerable to temperature rise in northern India as compared to other two central and eastern India. Rise in atmospheric temperature reduced leaf area index, grain number as well as weight of grains which was in turn reflected in yield of mustard crop. Seed yield reduction occurred by low water availability during stem elongation, flowering and pod development in mustard. Priming with moringa water extract and ascorbate substantially improved the tissue water status, membrane stability, gas exchange, water productivity of the plant. Late sown wheat crop faces high temperature stress during ripening phase. Delayed sowing reduces the tillering period and hot weather during critical period of grain filling lead to forced maturity thereby reduces the grain yield. Application of mulches in wheat produced higher grain yield over without much wheat. Organic mulches provided better soil water status and improved plant canopy in terms of biomass, root growth, leaf area index and grain yield as compared to inorganic mulch. The foliar spray of KNO₃ (0.5%) at 50 per cent flowering stage, 1.0 per cent KNO₃ during anthesis stage, 2.5 mM of arginine, spray of zinc, extra irrigation water during grain filling stage increased the productivity of wheat under high temperature stress.

 Light irrigation in mustard crop one day before frost occurrence protects from frost damage by improving heat transfer and heat capacity.  Plastic mulch raises the surface temperature of the soil nearly 10 °C over   bare soil.  Smoke particles are usually less than 1 µm in size, reflect visible radiation but trap the long wave radiation and so are effective in preventing rapid cooling of surface near ground. Mixing air and liquid materials in the right proportion to create many small bubbles is the secret to generate foam with low thermal conductivity. Organic mulches (straw and saw dust) provided better soil water status over ash mulch.