The influence of winter rape area in the crop rotation to the soil agrochemical properties and composition of humus

Subject to the winter rape area in crop rotation, the change of the sod gley light loam soil agrochemical properties among them humus composition was established. After the first Crop rotations rotation in the soil the hydrolytic acidity increased by 67,0-74,0%, base saturation degree decreased by 18,4-20,4%, exchange acidit, reduction tendency was noticed. During the increase of winter rape area in crop rotation (75%) the hydrolytic soil acidity increased essentially. After the first crop rotations rotation humus in the soil decreased by 14,0-16,0%. The smallest amount of total nitrogen was found in the crop rotation in which winter rape occupied 25% of the area (decrease by 30,0%), and the biggest amount was found where winter rape made 75% of the crop rotation area (decrease by 25,0%). The nutrient substances available for plants decreased in the soil as well, but the amount of mobile sulphur in the crop rotation with 25% of rape area increased 3,6 times and with 75%-5,0 times. In the crop rotations with different winter rape area after the first rotation the humus composition changed: ratio of humic and fulvic acids decreased from 0,88 (before the preparation of the experiment) to 0,45-0,47. Humus type in the arable soil turned from humatically-ful vatic. Humic and fulvic acids fractions regrouped. Firmaly bound with the soil mineral part acids made the biggest humic acids part (40,2-43,9%), and the free acids made the smallest part (17,7-18,7%). The amount of free humic acids was 10,0-13,0% bigger than before the preparation of the experiments and the amount of calcium humates 69,0-89,0% smaller. After the first rotation fulvic firs fractions increased 2,1-2,5 times and the second fractions by 43,0-58,0%. After the first rotation the amount of calcium humates was 2,2-2,7 times less than the fulvic acids of analogic fraction. After the first rotation the degree of organic carbon humification decreased by 24,0-36,0%. This process went on most rapidly in the crop rotation with the smallest winter rape area (25%). In this crop rotation a more intense organic, matter mineralization tendency should be noted as well. In the event of increase of winter rape area in the crop rotation up to 75% owing to the growth of soil acidity these processes slow down, calcium humates optical density decreases.