The Soil Quality Affected By Different Amount Of Biogas Slurry In Wheat Planting Field

Biogas fertilizer is a kind of high quality organic fertilizer, have been found after the biogas projects have been developed in China. Biogas fertilizer is not only more clean and higher efficient than compost and farm manure, but also can reduce many soil and environmental problems brought by the improvement of long-term application of chemical fertilizer. In this paper, six treatments, i.e. treatment 1 (no fertilizer), treatment 2 (fertilizers single),3 (biogas manure mixed chemical fertilizer), treatment 4 (low quantity of biogas manure), treatment 5 (medium quantity of biogas manure) and treatment 6 (high quantity of biogas manure), were designed, respectively. The wheat yields, soil physicochemical property, soil nitrification density, nitrate nitrogen content and soil heavy metal content was explored. The results were as follows:1.In different fertilizer applying treatments, although the soil organic matter, total nitrogen, available nitrogen content, available phosphorus content, and available potassium content had some variation, there was no significant difference. Among them, soil total nitrogen of treatment 3 increased from 1.0541 g kg-1 (preplanting) to 1.0945 g kg-1 (harvest); however, the soil total nitrogen content of other treatments was decreased; the soil total nitrogen of treatment 2 decreased from 0.9812 g kg-1 to 0.3828 g kg-1, which was significantly lower than that of other treatments, with a drop to 61%. The soil alkali-hydrolysable nitrogen content declined sharply as well, the average decline was 37%, and there was no significant difference among the treatments.2.The results suggested that the nitrification intensity in different treatment soil was very different, and nitrification intensity in treatment 2 and 4 soil was significantly higher than that of the other treatments; the nitrification intensity at different growth stage soil varied as the following order:wheat tillering stage> filling stage> jointing stage, and the highest soil nitrification intensity appeared in wheat tillering stage; the soil nitrate content in wheat tillering stage was significantly higher than that in the seedling stage, jointing stage and filling stage; while at wheat tillering stage, the soil nitrate content of treatment 2 was higher than that of the rest treatments.3. Though the concentration of heavy metal, including chromium, copper, zinc, lead, nickel, was somewhat increased in different treated soil after the whole wheat growing season, the heavy metal content in soils accorded with the national soil environment quality standard (GB15618-1995); and there has not appeared the status that heavy metal polluting soil. The heavy metal content in the soil increased gradually along with the amount of biogas fertilizer increasing. The results also showed that, after application of chemical fertilizers, the soil heavy metal content increased significantly; for example, After wheat harvest, the concentration of Cu2+ in treatment 2 soil increased from 4.57 mg kg-1 to 9.70 mg kg-1, increase by 112%, which suggested that chemical fertilizers application could increase the soil heavy metal content rapidly in a short time. Similarly, manganese, iron, magnesium content in the tested soil was rising with the increase of applying biogas slurry content.4.The results revealed that when the applying amount of biogas slurry reached to 27000 kg hm"2, the wheat yield got 350.46 kg 667 m"2, which achieved the same yield level with the conventional chemical fertilizer application. Combination of the soil environment evaluation analysis, the recommended amount of biogas fertilizer applying in practice was 27000 kg hm-2.