Changes in the balance of humus in the soil of five-field crop rotation depending on fertilizer systems

Abstract

Studies conducted on deep, medium-loamy typical chernozem within a long-term five-field crop rotation have shown that the removal of all by-products from the fields (soybean, winter wheat, sunflower, spring barley, and grain corn), regardless of the fertilisation system, leads to a negative humus balance ranging from 551 to 1305 kg/ha. When only wheat and barley straw is removed, the humus balance also remains negative across all experimental variants, but at significantly lower levels—ranging from 179 to 277 kg/ha. In contrast, when all by-products of the crops in rotation are used as organic fertiliser, the humus balance becomes positive, amounting to 8–398 kg/ha. The main source of humus formation in the soil is the crop residues of cultivated plants in the rotation. Through their humification, 1.66 times more humus is formed compared to that derived from the by-products of the three main crops. According to the index of agricultural ecologisation and the applied rates of organic fertilisers, the rotation variant in which byproducts are used as organic fertiliser and 16 t/ha of manure + N112P100K86 is applied qualifies as having an intensive level of agricultural ecologisation. The productivity of the crop rotation in which all crop by-products are removed from the fields is 11–13% lower than that of the rotation where by-products are used as organic fertiliser in three fields.