Nitrogen in Chernozems under Traditional and Direct Seeding Cropping Systems: A Review

Abstract

The functional role of nitrogen in the formation of crop yield on chernozems under conditions of traditional and direct seeding (DS) cropping systems is considered. In the course of long-term experimental studies of DS cropping system on chernozems, considerable experience has been gained and has found efficient practical application. It is shown that the effect of nitrogen as the most important element in the composition of humic substances influencing the fertility of chernozems depends on the variability of environmental factors, the forms and rates of nitrogen fertilizers, the rotation systems, and the soil treatment technologies. The DS cropping system has been tested for 4–10 years on experimental fields of the Stavropol Agricultural Research Institute and in a number of farms in Stavropol region. The obtained data on the yields of cereal crops and the application of fertilizers attest to the importance of the formation of a mulching layer of plant residues on the surface of ordinary and southern chernozems in the DS systems. This layer contributes to a gradual accumulation of nitrogen, protects the soil from erosion, and increases the number and mass of earthworms. Nitrogen in the DS cropping systems on chernozems in Russia is characterized by the high mobility and the capacity for considerable transformation. In this context, further investigations and special experiments are necessary to gain better knowledge of the behavior of nitrogen in different cropping systems. In particular, the relationships between nitrogen fluxes, agrophysical soil properties (aggregate-size distribution at the macro and micro levels), and specificity of the organic matter in different subtypes of chernozems under different cultivation technologies have to be clarified. In general, the role of DS cropping systems in farming practices has become more significant in the recent years; application of the DS cropping system is considered a positive factor in maintaining and restoring soil fertility.