Loading capacity estimation and risk assessment of livestock manure in cultivated lands around Dongting Lake

Based on the status of animal husbandry in Dongting Lake area, the quantity of livestock manure was estimated using the excretive coefficient method and the loading capacity and risk conditions evaluated. The results show that the output of livestock manure, urine, BOD₅, COD and NH₃-N in Dongting Lake area in 2006 are 1 616.93×10⁴ t, 1 248.30×10⁴ t, 72.41×10⁴ t, 79.33×10⁴ t and 7.48×10⁴ t respectively. The average loading capacity of livestock manure reaches 19.25 t·hm^-2. Forewarning average risk level of livestock manure loading is 0.47. On the average, there is no environmental pollution, and there is still room to develop animal production in Dongting Lake area. However, some cultivated lands already show livestock manure pollution, a trend that can not be ignored.