Rhizobium-Legume Symbioses: Heavy Metal Effects and Principal Approaches for Bioremediation of Contaminated Soil

Abstract

Intercropping is the system of simultaneously growing two or more crops on the same land area with a definite row arrangement. However, it is very much important to ensure that component crops do not compete with each other for space, moisture, nutrients, and solar radiation. Cereal+legume intercropping provides a greater scope for minimizing the adverse impact of moisture and nutrient stress in addition to improving system productivity and soil health. Researchers reported significant enhancement of system productivity in intercropping besides supplying diversified food. By improving chemical, biological, and physical environment in the soil, legumes can check the declining productivity of cereal-based cropping system. It is important to identify the best intercrops and to assess appropriate doses of nitrogen (N) for the cereal components in intercropping systems considering the sparing effect of biological nitrogen fixation (BNF) from the leguminous component. A number of indices such as land equivalent ratio, crop equivalent yield, relative crowding coefficient, competition ratio, aggressivity, actual yield loss, etc. have been suggested to evaluate the competition between cereal and legume intercrops and advantage of intercropping compared to sole cropping. Although there are some constraints for practicing cereal+legume intercropping systems in large scales like limited availability of good-quality seeds, biofertilizers, and technical and proper scientific knowledge for the complex intercropping system, there is a very good potential to increase the productivity and profitability from resource-poor agricultural systems by adopting this system besides reducing farmers’ risks and improving the soil quality in the long term.