Manure nutrient management mode in typical mixed crop-dairy farm

Abstract: Intensive dairy farms have developed rapidly in China over the last three decades, which have produced a lot of manure nutrients. However, due to the decoupling of crop-animal systems and poor manure management, large loss of nutrients from manure has led to serious environmental pollution. There is an urgent need to define an integrated manure management plan, which requires a quantitative understanding of nutrient balance and budget in a mixed crop-animal system. In this study, we reported a typical manure processing model so called "solid-liquid separation - compost+oxidation pond - manure application" from a dairy farm, and developed a comprehensive manure nutrient management plan using the data collection from farm investigation, soil, solid and liquid manure sampling and parameters collection from literatures. The results showed that dairy excretion N and P were 204 and 33 t/a with the breeding stock number of 2 978 dairy cattle, respectively. After manure collection and processing, the N and P amounts of manure nutrients were 126 and 27 t/a, which could be available for crop use. Manure management of lactating dairy cattle and young dairy cattle were different, therefore the amount of their manure nutrients supply were quantified, respectively. The collection rate of manure N and P nutrient was 131 and 23 t/a in the lactating dairy cattle house, respectively. The manure from flood flushing system was treated by solid-liquid separation; therein the solid part of manure after solid-liquid separation could be composted as organic fertilizer applied to the field. At the same time, the liquid part could be treated by the oxidation pond as liquid manure to be returned to the field. The rate of manure N and P nutrient from lactating dairy cattle house was eventually 107 and 22 t/a, respectively. The young dairy cattle was mainly raised outdoor. Most of urine would be leaked and evaporated on the non-concrete ground, and the solid feces were collected regularly on a dry manure basis. Therefore, the amounts of solid manure N and P nutrient collected from young dairy cattle were 23 and 5 t/a, respectively. Finally, the amounts of N and P nutrient from young dairy cattle's solid manure composted were 19 and 5 t/a, respectively. Based on crop nutrient requirements and soil nutrient supply, considering the ratio of manure to inorganic fertilizer (50%) and current manure nutrient use efficiency (30%), the amounts of manure N and P that could be applied to arable land were 727.6 and 131.2 t/a with the land area of 1 473 hm2, respectively, which were greater than the amounts of available manure nutrients from the dairy farm under different N and P indices. Among them, total application rates of manure N and P nutrient for silage corn, grain corn, alfalfa, and apricot were 287 and 61.1, 213.8 and 22.2, and 226.0 and 47.7, 0.8 and 0.2 t/a, separately. Therefore, the land carrying capacity of manure N and P nutrient is sufficient in this typical mixed crop-dairy farm. Manure application management plan in the mixed crop-dairy farm shows that, 19 000 and 14 000 t organic fertilizer can be applied to the farmland, and 100% of organic fertilizer produced from dairy farms can be eliminated based on N and P application rules. A total of 1.40 and 2.53 million m3 waste water can be used as fertilizer in the dairy farm, which is 5.6 and 9.8 times the current amount of waste water based on N and P application rules, respectively. The implementation of comprehensive manure nutrient management plan can make full use of manure nutrient resources for crop growth and reduce the direct discharge of manure nutrient to the environment, thus ensuring long-term sustainable production in the mixed crop-dairy farms.