Technological design of slurry manure storage and returning to farmland for fertilization on large-scale dairy farm

In order to promote the healthy development of animal husbandry, China put forward the road of green development of agriculture. The combination of planting and breeding has become an inevitable choice. The utilization of manure back to farmland is an important way of waste treatment in dairy farms. There are three types of manure, including solid, liquid, and slurry manure, which can be used as organic fertilizers. At present, returning of solid manure (after composting) and liquid manure (after storage or anaerobic fermentation) to the cropland has become the main way in dairy farms in China, while the slurry manure (after storage) is widely used in developed countries, such as Europe and America. Compared to other types of manure, the slurry manure contained higher nutrient, showing a promising application prospect in the areas with sufficient farmland. The storage technology of slurry manure has some good characteristics, such as easy collection of excrement, saving storage areas, and low treatment cost. However, only a few application cases were realized in China. In this study, the following contents were investigated for the technological design of manure storage, including the amount of collected manure wastes, parameters of storage facilities, parameters of manure utilization to farmland, costs of operation and so on, the volume of slurry manure storage facilities and the matching land areas of manure returning to farmland were given at the end. The results showed that the obvious advantages can be found in the slurry manure technology. A scaled farm with 500 dairy cattle was taken as an example, where the amount of slurry manure was 17.33 t per day. There are two types of slurry manure storage facilities, under-floor storage pit inside the breeding house and manure storage lagoon outside. The length, width, and depth of one under-floor storage pit were 85, 12 and 2 m, respectively, which can meet the storage need of slurry manure produced during 9 months. In the scaled farm with 500 dairy cattle, it needed 5 under-floor storage pits, where the total volume was 10 200 m3. The length, width, and depth of one manure storage lagoon were 90, 30 and 2.2 m, respectively, with a total volume of 5 615 m3, which can meet the storage need of slurry manure produced during 9 months. The farmland area for the application of manure was closely related to crop species and planting system. If the planting crops were wheat, harvest once a year, 248.4 hm2 of farmland was needed for manure application. If the planting crops were corn, harvest once a year, 400.6 hm2 of farmland was needed for manure application. If the planting crops were wheat and corn, harvest twice a year, 122.8 hm2 of farmland was needed for manure application. If the planting crops were rice, harvest twice a year, 127.0 hm2 of farmland was needed for manure application. The cost of all slurry manure returning to farmland was 103.7 thousand yuan, saving about 228 thousand yuan a year, compared with that of chemical fertilizers, and the annual economic benefit is 124.3 thousand yuan. The finding can provide a potential support for the application of storage technology for slurry manure.