Changes In Nitrogen And Phosphorus Of Dairy Cow Excreta During Generation, Collection,Stacking And Treatment Process

China’s livestock and poultry industry is developing rapidly, in the direction of intensive and large-scale, the amount of livestock and poultry manure discharge is also increasing, which contain large amounts of nitrogen and phosphorus. If livestock and poultry manure discharge is not treated in time, the environment would be seriously polluted. Controlling pollution of livestock and poultry industry has reasonably become the focus of pollution prevention currently.This study monitored the nitrogen and phosphorus data of excreta at each stage and analyzed these data, which based on generation, collection, stacking and treatment process of dairy cow excreta. One hand, it could provide a reasonable method for feeding dairy cows and improve the situation of dairy cows by utilizing nitrogen and phosphorus in feeds; On the other hand, it could support the dairy cow excreta management and pollution prevention. Aims of the study were:estimating excreted amounts of nitrogen and phosphorus in manure of dairy cow based on their ingested amounts of feed nutrient ingested; monitoring changes of nitrogen and phosphorus during wastewater discharge, feces collection and temporary stacking process on dairy farm; monitoring changes of nitrogen and phosphorus during biogas slurry treatment process on dairy farm.Nitrogen and phosphorus amount was investigated in feed and manure in a large-scale dairy farm in summer and winter. The study aimed to develop a method of evaluating excreted amounts of nitrogen and phosphorus in summer and winter based on the relationship between ingested and excreted amounts of nitrogen and phosphorus in dairy farms. Studies showed that feed ingested of nitrogen and phosphorus in dairy cows in different physiological stages were significantly different (P<0.05). The excreted amount of nitrogen and phosphorus in feces and urine of dairy cows in different physiological stages was significantly different (P<0.05), and more than50%of the ingested nitrogen and phosphorus was allocated in feces and urine. Both the ingested amounts of nitrogen and phosphorus in feeds were significantly correlated in the excreted amounts of those in feces. urine and milk in summer and winter. According to the relationship between excreted/ingested amount of nitrogen and phosphorus of dairy cow at different stage of growth, an estimated model could be built by regression analysis. The model was used to evaluate data in feces management and pollution prevention in dairy farms.The study analog the process of wastewater discharge, feces collection and temporary stacking on dairy farm, and monitored the changes of nitrogen and phosphorus contents and forms during the whole process. During dairy cow feces collection, the amounts of feces would be lost and the collection rate would be reduced as the cause of the rinsing function of dairy cow urine. And the effect to feces which was high moisture content was more significant than low moisture content feces. The amounts of nitrogen would be lost during wastewater discharge process, and it had difference as the cause of different discharge modes and flowing distance; the loss amounts and amounts of nitrogen was more significant when wastewater discharge dispersedly; the more the loss amounts of wastewater was, the longer drainage ditch was. After stacking30days. pH. moisture content, total organic carbon, total nitrogen, ammonium nitrogen, nitrate nitrogen, carbon to nitrogen ratio and total phosphorus of feces were hardly changed. pH and carbon to nitrogen ratio were suitable for composting, but moisture content which was79.77%was too high to compost. The changes of pH, total organic carbon, total nitrogen and carbon to nitrogen ratio of feces were significantly different (P<0.05) as the cause of high-temperature environment and adding the litter. But the effect coming from the stack height was not significant (P>0.05). Therefore, the loss of nitrogen should be controlled when feces stacking at high temperature or adding the litter.Total nitrogen and phosphorus and chemical oxygen demand of effluent water through wastewater purification system were135.3mg/L.28.9mg/L and1325mg/L respectively, they were reduced by82.62%.62.74%and86.86%respectively. There are many nutrients in effluent water, it was suitable for Irrigating farmland. After biogas slurry was treated by filtration system, nitrogen and phosphorus of suspended solids would be intercepted on sieve and the amounts of nitrogen and phosphorus would be reduced into the farmland.In summary, the assignment of nitrogen and phosphorus what come from feeds of dairy cows among feces. urine and milk could change with different physiological stages of dairy cows and different seasons. There were errors in estimation of excreted amounts of feces and urine of dairy farm a year by using data of single season. When estimating the returning amounts of nitrogen and phosphors in excreted amounts of feces and urine, the changes of nitrogen contents and forms should be fully considered during the process of manure collection, stacking and transportation.