Impact of cropping systems on pedogenic distribution and transformations of micronutrients, plant accumulation and microbial community composition in soils: a review

Different types of agricultural cropping systems involving wheat coupled with rice, maize and cotton are adapted by most of the farmers around the world. In order to increase the production of food grains with the adaptation of these cropping systems, intensive cultivation is required which eventually needs more quantity of macro as well as micronutrients. The availability of micronutrients to plants is majorly affected by cropping patterns and their profile distribution and the chemical pools. For instance, rice–wheat (R-W) cropping system depletes the available micronutrients status in soil. Many crops have a deep root system that allows them to fulfill their micronutrients requirement from deeper soil layers. In pedon, the surface layer of soil is richer in micronutrients than sub-surface soils. Thus, the knowledge of all the forms or fractions of micronutrient in soil and conditions that help in converting them to their available forms is essential. Excessive use of macronutrient fertilizers in soil with alkaline pH, results in an upsurge accumulation of micronutrients under R-W system. Consequently, it is essential to understand the relationship between accumulation of micronutrients by plants and different chemical pools of micronutrients and their distribution in the pedon. Also, the incorporation of different crops in various cropping systems has a marked influence on microbial communities in soil which play a crucial role in nutrient cycling, gaseous exchanges, aggregation and soil biochemical processes that ultimately influences crop productivity and soil health. Thus, imaging the extent of micronutrient availability to plants, various fractions of micronutrients and microbial community in soil under different cropping systems is necessary.