Summary and Keywords
Planned crop rotation offers a pragmatic option to improve soil fertility, manage insect pests and diseases, and offset the emission of greenhouse gases. The inclusion of legume crops in crop rotations helps to reduce the use of external nitrogen inputs for legumes and other crops because legumes may fix the atmospheric nitrogen. This also helps to reduce the environmental pollution caused by volatilization and leaching of applied nitrogen. The inclusion of allelopathic crops in rotation may be useful to suppress noxious weeds due to release of the allelochemicals in the rhizosphere. The rotation of tap-rooted crops with shallow rooted crops may result in efficient and productive use of nutrient resources and conservation of soil moisture. Continuous monoculture systems may cause the loss of biodiversity. Land fallowing is an efficient agricultural management technique mostly practiced in arid regions to capture rainwater and store it in the soil profile for later use in crop production. During fallowing, tillage operations are practiced to enhance moisture conservation in the soil. Keeping soil fallow for a season or more restores soil fertility through nutrient deposits; increases organic matter, microbial carbon, and soil microbial diversity; and improves the soil’s physical properties, including aggregation stability and reduced soil compaction due to decreased traffic. In addition, fallowing of land provides biological means of pest (weeds and insects) control by disrupting the life cycle of pests and decreasing reliance on pesticides. Land fallowing can help offset the emission of greenhouse gases from agricultural fields by reducing traffic and increasing carbon sequestration within the soil. Summer fallowing may help to preserve moisture in diverse soil types in the rainfed regions of the world, although it may reduce the carbon sequestration potential of soils over the long term. Energy resources are decreasing, and the inclusion of energy crops in crop rotation may be highly beneficial. Many of the processes, factors, and mechanisms involved in crop rotation and land fallowing are poorly understood and require further investigation.
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