Response of Mung Bean (Vigna radiata (L.) R. Wilczek) to an Increasing Natural Temperature Gradient under Different Crop Management Systems

Abstract

AbstractIncreasing temperatures pose a significant threat to crop production in the tropics. A field experiment was conducted with mung bean at three locations in Sri Lanka representing an increasing temperature gradient (24.4–30.1 °C) during two consecutive seasons to (i) determine the response of mung bean to increasing temperature and (ii) test a selected set of crop management practices aimed at decreasing essential inputs such as water, synthetic pesticides and inorganic nitrogen fertilizer. The control treatment (T1) consisted of standard crop management including irrigation, chemical crop protection and inorganic fertilizer application. Adaptation system 1 (T2) included mulching with rice straw at 8 t ha−1 with 30 % less irrigation and crop protection and nutrient management as in T1. Adaptation system 2 (T3) included crop protection using a pretested integrated pest management package with water and nutrient management as in T2. In adaptation system 3 (T4), 25 % of the crop's nitrogen requirement was given as organic manure (compost) at 0.8 t ha−1 while 75 % was given as inorganic fertilizer with water management and crop protection as in T3. Durations of both pre‐ and post‐flowering phases were reduced with increasing temperature. In the warmer (25.4–30.1 °C) yala season, seed yield (Y) of T1 decreased with increasing temperature at 366 kg ha−1 °C−1. However, in maha season, Y did not show a significant relationship across the narrower temperature gradient from 24.4 to 25.8 °C. Pooling the data from both seasons showed a second‐order polynomial response with an optimum temperature of 26.5 °C. In addition to shortened durations, reduced crop growth rates and reduced pod numbers per plant were responsible for yield reductions at higher temperatures. In yala, yields of all adaptation systems at all locations were on par with yields of the respective controls. Furthermore, yala yields of T2 and T3 were less sensitive than T1 to increasing temperatures (265 and 288 kg ha−1 °C−1). In maha, T3 and T4 had greater yields than the control at the relatively cooler site while having lower yields than the control at the warmer site. Maha yields of T2 were on par with the control at both temperature regimes. While demonstrating the significant temperature sensitivity of mung bean yields, results of the present work showed that components of the tested adaptation systems could be promoted among smallholder farmers in Asia, especially in view of their long‐term environmental benefits and contributions to sustainable agriculture in a warmer and drier future climate.