The aim of the research is to study the role of plant residues of intermediate seeding of forage crops in regulating the biological factors of fertility recovery of irrigated gray-brown (chestnut) soils in the arid zone of Azerbaijan. The object of the study is the Gyanja-Kazakh massif, irrigated gray-brown (chestnut) soils (Irragri Kastanozems) of the Kura-Araks Low-land. Field experiments and analyzes of plant and soil samples were carried out by generally accepted methods. It has been found that the variants are arranged in a row according to regu-lation of soil fertility biological factors: rye + vetch + rape – corn + soybean + sorghum + ama-ranth – barley + vetch > barley + vetch + rape – corn + soybean + sorghum + amaranth – bar-ley + vetch > alfalfa > sainfoin > alfalfa (crop sowing) > virgin soil > barley – corn > rye – corn > corn (spring sowing) > corn + soya + sorghum + amaranth (spring sowing) > barley for grain. It was found that in the arid zone under irrigation it is possible to obtain three yields of green mass per hectare per year and to accumulate 152.5 centners of dry mass of plant resi-dues (variant winter rye + vetch + rape (1st yield) → corn + soybean + sorghum + amaranth (2nd yield) → barley + vetch (3rd yield)) in the soil layer 0–25 cm. In spring, summer and au-tumn, the number of microorganisms in the soil ayer 0–25 cm was 23.3·10⁶, 10.2·10⁶ and 19.8·10⁶ in 1 g of soil, invertase activity was 23.3; 20.5; 21.9 mg of glucose/(g of soil·24 hours), catalase – 25.1; 21.4; 22.6 cm³ O₂/(g soil·min), soil respiration – 301, 221, 249 mg CO₂/(m²·h) and cellulose decomposition – 40.0; 36.4; 36.9 %. In the soil layer 0–25 cm, the humus balance increased (+0.60 t per ha). These indicators were lower in other cases.
Key words: gray-brown (chestnut) soil, biological factors, fertility, intermediate crops, microorganisms, enzymes, soil respiration.
