Drought risk management for increased cereal production in Asian Least Developed Countries

摘要

Drought stress is a serious abiotic factor inhibiting nutrient acquisition by roots and limiting cereal crop production in Asian Least Developed Countries (LDCs). Many studies revealed that balanced fertilization can improve photosynthetic activity by stabilizing superoxide dismutase (SOD) activity, improve proline, abscisic acid (ABA) and make the crop drought tolerant with efficient root system and finally improve crop yield. To mitigate drought stress, along with the usage of resistant and efficient genotypes, soil and foliar applications of macro- and micro-nutrients are being used in Asia. According to drought sensitivity index, the efficient genotypes are found more drought-tolerant than the inefficient ones. Studies revealed that irrigation alone is not sufficient to obtain satisfactory grain yield without balanced fertilization. At drought stress, the efficient genotypes accumulate higher quantities of ABA and proline, and exhibit higher activities of SOD, as compared with inefficient genotypes through greater nutrient accumulation by their longer and thinner root systems with high efficiency. Under severe drought with low nutritional status, the rate of photosynthesis, particularly water-use efficiency (WUE) increases in the efficient genotypes than in the inefficient ones. Consequently, these physiological and morphological parameters result in better yield performance by efficient use of water. Under drought, soil application of NPK along with foliar application of zinc (Zn), boron (B) and manganese (Mn) increase grain yield as well as micronutrients concentration of the grain. The rate of photosynthesis, pollen viability, number of fertile spikes, number of grains per spike, and WUE are increased by late foliar application of these micronutrients. This indicates that, by increasing WUE foliar application of Zn, B and Mn at booting to anthesis can reduce the harmful effects of drought that often occur during the late stages of cereal production in Asian LDCs. Therefore, it can be concluded that soil application of Zn, B and Mn in early stage combined with foliar application in late stage, especially at the flowering stage, is a promising approach to alleviate drought stress. Another attractive environmental friendly approach is to select efficient and drought tolerant genotypes with a more efficient root system. These findings are of high relevance for farmers? practices, the extension service and fertilizer industry to mitigate the drought stress in Asian LDCs. A few recommendations are made for extension of scientific knowledge to find more scope in support of mitigating drought situation.