Modern system of agriculture provides active use of vegetable remains as local organic fertilizer. However, the cultivation of crops on various agricul-tural background changes chemical composition of vegetable remains resulting in unpredictability of their transformation in humus substances. The re-searches on chemical composition of vegetable remains studying were conducted on the perma-nent establishment of Northern Trans-Urals SAU which is located in the northern forest-steppe. From all studied cultures peas took leading place accord-ing to the content of nitrogen in the vegetable re- mains - 1.6 % of the weight. In other cultures the content of nitrogen varied within 0.5-0.7 % of the weight. The maximum value of the content of po-tassium was noted in oats straw - 1.6 % of the weight, in other grain crops it varied within 0.8- 1.0 %. The content of phosphorus in the vegetable remains of crops was minimum - 0.2-0.3 % of the weight. High content of calcium was noted in the vegetable remains of colza and peas - 1.8 and 2.0 % respectively that more than twice exceeds the values of other cultures. The cultivation of grain crops on options with planned productivity of up to 6.0 t/hectare of grain promoted the accumulation of nitrogen in straw up to 1.2 % of the weight exceed-ing the control twice. When modeling the process of accumulation of nitrogen in collateral production of grain crops grown up at various level of mineral food it is possible to use the regression equation of type: ; where x - the dose of nitric fertilizers, kg of active ingredient on hec-tare; y - the content of nitrogen in straw, per cent. The coefficient of approximation of this equation makes more than 0.9 units. The introduction of in-creasing doses of mineral fertilizers practically did not influence the content of phosphorus and potas-sium in grain crops straw.