Evaluating temperature thresholds and optimizing sowing dates of wheat in Bihar

Abstract


 Studies on wheat-weather relationship were carried out at Pusa (25.98 oN, 85.67 oE, 52 m), Bihar situated in middle Gangetic plains of India, with three popular wheat cultivars viz. RW 3711, HD 2824 and HD273, grown under five fixed dates of sowing viz. 15 November, 25 November, 5 December, 15 December and 25 December, for five consecutive rabi seasons from 2011-12 to 2015-16. Thresholds of maximum temperature (Tmax), minimum temperature (Tmin) and bright sunshine hours (BSH), associated with higher productivity, occurring at different phenophases, were determined. Results revealed that temperature played a crucial role in achieving higher grain yield of wheat. Both Tmax and Tmin during flowering to milking and flowering to maturity phases increased with delayed sowing dates beyond 25 November with consequent reductions in grain yield. During 50 % flowering to milk stage, Tmax and Tmin above 24.6 oC and 11.6 oC, respectively, reduced grain yield below 4000 kg ha-1; significant reduction in grain yield was also noted beyond maximum temperature of 26.9 oC. During flowering to milk and flowering to maturity phases, Tmax and Tmin exhibited highly significant negative correlation with grain yield, indicating higher temperatures causing lower grain yield. With delayed sowing, sensitive phases of the crop experienced higher air temperatures which led to reduction in grain yield. An increase of Tmax from 29.2 to 32.1 oC during flowering to maturity phases reduced the wheat productivity drastically in this region of Indo-Gangetic plains. Grain yield declined by 399 kg ha-1 per 1 oC rise in Tmax during 50 % flowering to maturity stage. Considering grain yield vis-à-vis temperature regimes during flowering to maturity stage, the most important recommendation for the farmers of the region would be to finish wheat sowing before 25 November in order to enable them to escape terminal heat stress in wheat and thereby realizing higher grain yield. The anthesis-time management by manipulating sowing dates could be a realistic adaptation strategy for attaining optimum grain yield under changing climate scenario.

Groundwater irrigation is critical for adapting wheat systems to warming temperatures in the Eastern Indo-Gangetic Plains in India

“…Wheat will be negatively impacted by warming temperatures in India, and one way to reduce this negative impact is by sowing wheat earlier (Kalra et al 2008, Balwinder-Singh et al 2015, Dubey et al 2020, Nesar et al 2022. Despite the importance of early sowing, many farmers sow wheat late in the eastern IGP, past the optimal date of November 25th recommended by agronomists (Sattar et al 2020). This is despite the fact that earlier wheat sowing is associated with large yield gains, superseding the importance of all other crop management variables in this region (McDonald et al 2022, Paudel et al 2023.…”

“…This is critical given that wheat is especially sensitive to high temperatures during the grain filling period prior to maturity (Asseng et al 2002, Lobell et al 2012, Liu et al 2016, Zhao et al 2016. Studies have shown that it is optimal to sow wheat across the IGP prior to November 25th (Ortiz-Monasterio et al 1994, Sattar et al 2020, and with every one day delay in wheat sowing after this period, there is a 0.8%-1.5% loss in wheat yields (Randhawa et al 1981, Lobell et al 2012. Despite the importance of early sowing, many farmers in the eastern IGP, particularly in the state of Bihar, sow wheat late, with some areas planting wheat as late as early January (Jain et al 2016, Chakraborty et al 2019, Newport et al 2020, Ishtiaque et al 2022.…”

Responses of phenology, yield attributes, and yield of wheat varieties under different sowing times in Indo-Gangetic Plains

“…The sum of deviations of maximum and minimum temperatures from optimum thresholds was calculated at critical growth phases for each date of sowing, and based on the largest deviations, heat stress was identified for the crop sown on different sowing dates. In this study, the sum of deviation from optimum thresholds of maximum temperature and minimum temperature for the sensitive growth phases, viz., flowering to milking and flowering to maturity, was calculated by taking 25°C and 12°C as optimum threshold maximum and minimum temperature, respectively, for flowering to milking (F-Mlk) and 27°C and 14°C as threshold maximum and minimum temperatures for flowering to maturity (F-Mat) stages (Sattar et al, 2020 andSrivastava, 2021).…”

Climate Science, Solutions and Services for Net Zero, Climate-Resilient Food Systems

“…Similarly, a minimum temperature of 16.8°C during the 50% flowering to the milking stage and a minimum temperature of 18°C during the 50% flowering to maturity stage significantly affected the crop yield, and it produced a yield below 2.0 t ha −1 . For achieving a yield target of 4.0 t ha −1 or more, Sattar et al (2020) while working on crop weather relationships on wheat observed that the maximum and minimum temperatures from sowing to tiller formation should be 23.7 and 11.8°C, respectively. Similarly, the maximum and minimum temperatures from 50% flowering to milking should be 24.6 and 11.6°C, respectively, and from 50% flowering to maturity, it should be 29.2 and 14.4°C, respectively (Table 5).…”

“…About 80% of wheat sowing is delayed in the region beyond the period of 25 November, forcing the crop to encounter higher temperatures (terminal heat) during the growing season (end of February to March) (Sattar et al, 2023). Therefore, terminal heat stress associated with dry westerly wind is a serious climatic constraint for successful wheat cultivation in India, particularly when it occurs during the grain-filling stage (Sandhu et al, 2016;Sattar et al, 2020). In one study on wheat, Poudel et al (2021) observed that the optimum temperature during the anthesis and grain-filling stage ranges from 12 to 22°C.…”