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The overuse of antibiotics has resulted in the prevalence of antibiotic resistance genes (ARGs) and antibiotic resistance bacteria (ARB) in the environment. High-density livestock farming is one of the major industries for antibiotic overuse. In this study, we sampled wastewater and manure at different stages of the feces treatment process from a dairy farm, as well as the soil in the farmland where the treated wastewater was being used for irrigation purpose. High-throughput Illumina sequencing was used to analyze the profiles of bacteria communities and ARGs. The results showed that the main ARG types were multidrug, aminoglycoside, glycopeptide, and tetracycline resistance genes, and Actinobacteria, Proteobacteria and Firmicutes were the main host bacteria phyla of these ARGs. The genus Nocardioides sp. and Ornithinimicrobium sp. were closely associated with the ARGs in the investigated samples. The relative abundances of ARGs in wastewater and manure were reduced by 68.5% and 62.1%, respectively, by the existing feces treatment process. Anaerobic fermentation and high-temperature fermentation were the most efficient treatment steps; the relative abundances of ARGs were reduced by 29.3% and 33.6% in the treated wastewater and manure, respectively. Irrigation with the treated wastewater significantly increased the abundance and diversity of ARGs and ARB in the surface soil of the farmland. The residual ARGs were found to transit through vertical gene transfer (VGT) and horizontal gene transfer (HGT) in soil. Therefore, the direct application of this inadequately treated wastewater and/or manure could risk spreading ARGs into the environment, and potentially impact human health. In order to effectively restrain the spread of ARGs, it is necessary to modify the wastewater and manure treatment processes and improve the regulations and guidelines of applying treated wastewater for irrigation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The mudflats along the East Coast of China can be important alternative sources for arable lands if amended by large amount of organic fertilizers. Rich in organic matter and other nutrients, dairy manure has been considered as the economic choice for an initial fertility driver. Therefore, the goal of this study was to evaluate the impact of dairy manure amendment (DMA) as an initial fertility driver at application rates of 0, 30, 75, 150, and 300 t ha–1 on soil physicochemical properties, biomass and growth of ryegrass (Lolium perenne L.) grown in mudflat soil. The results showed that the DMA decreased soil bulk density in comparison to the unamended soil. The organic matter (OM) content in mudflat soil increased with increasing DMA rates. The salinity of mudflat soil decreased with increasing DMA rates, and the salinity at 30, 75, 150 and 300 t ha–1 DMA rates, corresponded to decreases of 26.1%, 35.8%, 37.8% and 45.4%, compared to 8.63 g kg–1 in the unamended soil. Electric conductivity (EC) of mudflat soil decreased with increasing DMA rate, while cation exchange capacity (CEC) increased duo to DMA. The contents of total N, total P, alkaline N, and available P in mudflat soil increased with increasing DMA rates. The increment of green herbage yield of ryegrass at 210 DAS at 30, 75, 150, and 300 t ha–1 DMA rates were 257.7%, 303.5%, 414.8%, and 516.6%, compared to the unamended soil (p < 0.05). Soil total Cu and Zn increased while total Mn, Ni, and Cr remained unchanged in response to DMA due to the high Cu and Zn content in the dairy manure. However, The DMA increased most of available metals except for Ni. In summary, land application of dairy manure as initial fertility driver could be an effective and safe way to amend mudflat soil, due to the rapid development of soil initial fertility, which enhanced green manure ryegrass (Lolium perenne L.) growth. [ABSTRACT FROM AUTHOR]