Productivity of fodder crop rotations and their impact on the fertility of leached chernozem

Abstract

The paper presents the results of the study on the effect of methods for improving a six-field fodder crop rotation on productivity indicators and the content of macroelements available for plants (nitrogen, phosphorus and potassium) in a layer of 0-40 cmof leached chernozem in two rotations. Field studies were carried out in 2008–2019 in the conditions of the forest-steppe zone of Western Siberia. Improvement techniques included introduction of mineral fertilizers, oversowing legumes and oversowing legumes alongside the use of fertilizers. Oversowing legumes in crop rotation fields resulted in the productivity which was not lower than with the application of mineral fertilizer system. When fertilizers were applied, collection of dry matter in the first and second rotation from a unit of crop rotation area increased by 1.6–1.7 times compared to the control, namely 4.20 and6.30 t/ha, respectively, whereas when legumes were sown in each field, the increase was 1.5–1.8 times (3.97–6.59 t/ha). When both these methods were combined, the yield of dry matter in rotations increased by 1.6–1.8 times (4.32–6.98 t/ha). The alternation of crops in the crop rotation alongside improvement methods during the first two rotations contributed to the 1.7 times increase of nitrate nitrogen in the 0–20 cm layer with the use of mineral fertilizers (3.9 mg/kg of soil), and with legume oversowing – 2.5 times (5.7 mg/kg). The positive effect of crop alternation on the reserves of mobile phosphates in the soil in the control crop rotation was identified. The total amount of mobile phosphates in the experiment was 68 mg/kg in the 0–20 cm layer, and 21 mg/kg in the 20–40 cm layer. By the end of the first rotation, their increase reached 108 and 99 mg/kg, by the end of the second – 239 and 214 mg/kg, respectively. By the end of the second rotation, there was a slight increase in exchangeable potassium in the 0–40 cm layer in the control crop rotation, which was more significant in the 20–40 cm layer – from 97 to 103 mg/kg. In 2018, the mineral fertilization system of cereal crop rotation led to a decrease in exchangeable potassium compared to the control from 116 to 104 mg/kg of soil in the 0–20 cm layer, and from 103 to 91 mg/kg in the 20–40 cm layer. The removal of exchangeable potassium with the yield of cultivated crops due to crop rotation improvement methods exceeded its return with plant residues.