Nutrient cycling and utilization in a forage cultivation-cattle raising-biogas fermentation ecosystem in red soil regions

Rye grass and maize cultivated in mid-mellow hilly red soil were harvested to feed beef cattle.In the process of forage cultivation and cattle raising,two treatments were set,one of which was that forage was fertilized with chemical fertilizer only and was harvested to feed beef cattle(CK);another was that cattle feces and urine fermented in biogas pool was mixed with chemical fertilizer and the biogas-tank sludge,and applied to forage fields to grow animal feed.The results of two-year experiments show that the yield and nutrient accumulation of maize plants with the mixed application of biogas-tank sludge,are higher than those with chemical fertilizer only, but on the contrary,those of rye grass are lower.The application of mixed biogas-tank sludge can save chemical fertilizer by 1/2.There is little difference among cattle's digestion and recovery rate of nutrient of the same forage with different fertilization compositions, but there is significant difference among those of varieties and with different harvesting times of the forage. Most nutrients in the cattle's excrements can be recovered after biogas fermentation,saving about half of the input of the chemical fertilizer.The mixed application of biogas-tank sludge can maintain and improve the soil fertility,which provides better soil conditions for the sustainable production of forage.