Productivity of spring wheat as the first crop after fallow forecrops

The article presents data on the research, carried out from 2017 to 2020, on the impact of fallow as a forecrop and of chemicalization backgrounds on the yield of spring soft wheat. Wheat was cultivated as the first crop in field fallow-grain four-course crop rotation in the southern forest-steppe of the Omsk Region. Different types of fallow were studied: pure black, chemical and green fallow; in the last one, rapeseed was sown as a green fertilizer starting from the second half of July. Over 4 years, the following average amounts of spring wheat grains were obtained: 3.40 t/ha after rapeseed green fallow, 3.29 t/ha after pure black fallow, 3.23 t/ha after pure chemical fallow. Treatment with ammophos (N12P52) during sowing and with the herbicide Puma Plus, EC (1.4 l/ha) during the tillering phase provided for significant yearly increases in the wheat grain yield. Over 4 years, treatment with fertilizers led to an average increase of 0.447 t/ha, while treatment with herbicides led to an average increase of 0.207 t/ha. The main reasons for the grain yield increase were an augmentation in the plant germination rate and a steadier development of each single plant. Over the research period the plant germination rate ranged between 65.8 and 67.4% depending on the type of fallow forecrop. Treatment with chemicals provided for an increase in the plant germination rate of wheat up to 1.6-3.2%. Treatment with chemicals led to an augmentation in the mass per single plant up to 1.06-1.52 g when using only the fertilizer, up to 0.35-0.76 g when using only the herbicide, and by 1.09-1.67 when using both the fertilizer and herbicide. The highest mass per plant was observed after green fallow and amounted to 5.66 g, while it was inferior by 0.42 g after pure black fallow and by 0.52 g after chemical fallow.