Rice wheat cropping system in Nepal: Issues concerning sustainability

Abstract

Rice wheat cropping system has been widely adopted in Nepal since very long, but much less been studied about the sustainability aspects of this practice. South Asian countries-, as well as other rice-growing countries, have already experienced different ecological and environmental impacts of the long-term rice-wheat system. Also,climate change seems to inflict the rice-based farming system to a varied extent depending uponagroecological regions. In the meantime, the growth in yield of rice is plateauing to less than 1.5% although productivity is well below other South Asian countries. With the heightening consumption of agrochemicals and its subsequent impact on air, water and soil have to be taken into consideration. Rice-wheat system being heavy consumer of nutrient and waterraises question about the sustainable consumption of resources. The increasing dominance of hybrid varieties posses' threat of extinction of local landraces of rice. Apart from environmental and agronomic issues it also maybe affected by socio-economic issues of Nepalese farming families. Extensive studies are yet to be done, but practices like conservation agriculture and sustainable intensification practices are found to make system more resilient. The aim of this review is to discuss such issues associated with sustainability and propose some probable sustainability measures.

Role of Conservation Agriculture in Sustainability of Rice-Wheat Cropping System in Nepal

“…Average maximum CH4 emission from rice fields was found to be 28 kg/ha/season under rainfed conditions from studies conducted at Nepal Agricultural Research Council (NARC), Khumaltar. As for wheat crop it acts as a sink for CH4 and the major greenhouse gas isN2O.This alteration of wetting and drying cycle in RWCs promotes N2O emission (Lamsal and Khadka, 2019).…”

“…Furthermore, the loss of SOM is accelerated by reduction in biological nitrogen fixation and facilitation in mineralization of SOM during wheat crop season (Lamsal and Khadka, 2019). The heavy use of chemical fertilizers has contributed to the poor OMC ultimately declining the soil fertility in more than 60% of the cultivated land (Khanal et al, 2012).…”

“…In Nepal, 0.52-million-hectare areas suffer from drought. Due to conventional agriculture such as tillage operation, burning of crop residue rather than incorporating it to soil practiced in Nepal, soil moisture loss is higher (Lamsal and Khadka, 2019). The Ganga basin (India-Nepal) has the highest anthropogenic groundwater loss rate (~22.56±3.8 km3 per year) which is about 42% of total use (Tiwari et al, 2009).…”

“…Nepalese Rice-Wheat Cropping system is at risk of depletion of organic and inorganic components of soil unless residue of corresponding biomass is replenished into soil. For stabilizing the agriculture ecosystem, crop residue plays an important role by providing plant nutrients (Lamsal and Khadka, 2019). The application of crop residue has higher impact than the application of green manure.…”

“…This system requires sufficient irrigation, agrochemicals (fertilizers and pesticides), micronutrients and organic inputs. This nutrient-rich environment acts as a catalyst for the growth of phytopathogens and insect-pest (Lamsal and Khadka, 2019). Higher dose of nitrogenous fertilizers aimed for increasing yield also promotes disease and insects in wheat.…”