The research was aimed at studying the effect of various types of crop rotation on crop productivity, weed infestation, and humus content in a typical chernozem in the northeast of the Central Chernozem Region. The work was carried out in 1992–2008 in crops of monocrops and in crop rotations: row-grain (with bare fallow and non-fallow forecrop) and grain-fallow row (black fallow, green manured fallow–mustard). Mineral fertilizers (N30P30K30) were applied after mustard was planted under winter wheat, and manure (20 t/ha) was used in black fallow. We observed a decrease in weediness of crops by on average 4.5 times in crop rotations as compared with permanent cultivation. The introduction of a fallow field (black fallow) into the crop rotation reduced weed infestation by 2.2 times, including by three times by perennial species in comparison with the occupied fallow. Weediness in the variant with black fallow decreased by 3.4 and 5.5 times, respectively, relative to the non-fallow forecrop. The yield of crops was higher in crop rotation than in monocrop by 1.26 t/ha for winter wheat, by 0.90 t/ha for barley, by 1.09 t/ha for peas, and by 5.5 t/ha for sugar beet. The introduction of green manured fallow provided a significant (by 0.17%) increase in the humus content over a 9-year period in comparison with the initial amount. In the crop rotation with black fallow without fertilizers, its decrease by 0.14% was recorded. The annual application of 20 t/ha of manure into black fallow contributed to a significant increase in the humus content by 0.06% as compared to the initial one. The average productivity over the years of research increased by 210 grain units in crop rotation with green manured fallow relative to the crop rotation with black fallow and by 430 grain units/ha in the variant of applying mineral fertilizers in relation to green manured fallow without fertilizers and by 0.63 grain units in comparison with the crop rotation with black fallow.
Shabalkin et al. (2025) studied this question.