Abstract
The effects of applied digested pig slurry on a vegetable crops field were studied. The study included a 3-year investigation on nutrient characteristics, heavy metals contamination and hygienic risks of a vegetable crops field in Wuhan, China. The results showed that, after anaerobic digestion, abundant N, P and K remained in the digested pig slurry while fecal coliforms, ascaris eggs, schistosoma eggs and hookworm eggs were highly reduced. High Cr, Zn and Cu contents in the digested pig slurry were found in spring. Digested pig slurry application to the vegetable crops field led to improved soil fertility. Plant-available P in the fertilized soils increased due to considerable increase in total P content and decrease in low-availability P fraction. The As content in the fertilized soils increased slightly but significantly (p = 0.003) compared with control. The Hg, Zn, Cr, Cd, Pb, and Cu contents in the fertilized soils did not exceed the maximum permissible contents for vegetable crops soils in China. However, high Zn accumulation should be of concern due to repeated applications of digested pig slurry. No fecal coliforms, ascaris eggs, schistosoma eggs or hookworm eggs were detected in the fertilized soils.
Highlights
China is one of the most important livestock breeding countries in the world
Low levels of total N and total P in the raw slurry in winter probably resulted from these substrates being partly absorbed by the bedding materials
Abundant N, P and K nutrients remained in the digested pig slurry, and the hygienic conditions of pig slurry were improved as well
Summary
Intensive livestock production involves the release of large amounts of manure that give rise to serious environmental concerns. 3.6 billion tons of livestock manure was produced in 2007 in China [1]. The anaerobic treatment of livestock slurries could reduce pollutants and produce biogas, but simultaneously produce lots of digested slurries [1,2,3]. These digested slurries, containing various elements and microbes, might cause secondary pollution unless they are effectively utilized or further treated
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