Establishment and Application Demonstration of Standards for Agricultural Biogas Slurry Returning to Field in Citrus Orchard

Abstract

In this paper, we take citrus orchard as target, evaluate the safety of agricultural biogas slurry by comparing the properties of unfermented manure and biogas slurry from 27 farms in Chongqing. The results indicate that the amount of harmful heavy metal element in biogas slurry completely meets the requirements in China agricultural standards "Biogas Fertilizer" (NY/T 2596) and "Organic Fertilizer" (NY 525), indicating the biogas slurry is safe to use as fertilizer. These results provide data support in formulating a stricter standard about the limitations of harmful heavy metal containment ratio in biogas slurry. Biogas slurry can replace chemical fertilizer partly, and can be popularized as a good new type of liquid fertilizer. A certain amount of biogas slurry irrigation can basically meet the supply of nitrogen and phosphorus nutrition, and zero use of chemical fertilizer (nitrogen and phosphorus) come true. However, the content of biogas slurry varies greatly, the measurement of fertilizer efficiency is complex, and it cannot meet the balanced supply of all mineral nutrients, which will lead to the imbalance of nutrient abundance and deficiency. The nutritional diagnosis should be used to monitor the nutritional level of trees, guide the control of abundance and deficiency, enhance the efficiency of citrus orchards to absorb the effective elements of biogas slurry, and improve the yield and quality of citrus. Through monitoring the runoff quality of the orchard returned with biogas slurry, it is found that the runoff quality of the orchard is inferior V. Total phosphorus and granular phosphorus are the main contaminating sources of the outflow runoff in orchard. This indicates that the problems of nitrogen and phosphorus pollution need to be prevented and controlled in the process of returning the biogas slurry to the orchard. It is necessary to establish the landscape system of fruit grass in the orchard and the interception system of flood interception ditches, sediment pockets and buffer ponds in order to sand, retention and reduction of particulate phosphorus. Based on this, a bunch of agricultural biogas slurry returning technology model suitable for modern ecological citrus orchard planting was summarized. The technical standards for biogas slurry harmlessly returning to citrus orchard and technical specification for formula fertilization of citrus nutrition diagnosis, were formed. It has been applied on a large scale in Chongqing three gorges reservoir area and national modern eco-agricultural demonstration base, and has achieved remarkable socio-economic and ecological environmental benefits. The results of this study provide data and technical support for the formulation of two new national standards of "Agricultural Biogas Slurry" and "Technical Specification for Harmless Treatment of Agricultural Biogas Slurry".