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Effects of manure applications on rates of phosphorus accumulation and phosphorus saturation degree increase in arable soils
Received:December 12, 2015  
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KeyWord:manure;soil phosphorus;saturation degree;accumulation rate
Author NameAffiliationE-mail
YAN Zheng-juan College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China  
CHEN Shuo College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China  
ZHOU huai-ping Institute of Agricultural Environment and Resource, Shanxi Academy of Agriculture Sciences, Taiyuan 030031, China  
YANG Zhen-xing Institute of Agricultural Environment and Resource, Shanxi Academy of Agriculture Sciences, Taiyuan 030031, China  
CHEN Qing College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China qchen@cau.edu.cn 
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Abstract:
      In intensive farming regions of China, high rates of manure applications to arable field over years have caused high phosphorus(P)accumulation in soil and the associated environmental risks. Here a long-term field experiment was conducted to quantify the effects of manure applications on rates of soil P accumulation and the degree of P saturation(DPS) increase, i.e., the increment in soil P content or DPS per 1 kg P surplus, in an effort to develop guidelines for rational P management and non-point source pollution reduction. Results showed that 22 years of continuous excessive P inputs increased soil P content and DPS. In 0~20 cm soil depth, soil P and DPS increased linearly with increasing P surplus. Compared with single chemical fertilizer application, manure incorporation had no significant effects on the ratios of soil total P increments to P surplus increments, but significantly increased the ratios of soil available P and DPS to P surplus increments. The increases in soil Olsen-P, CaCl2-P, and DPS per 1 kg P surplus were 0.071 mg P·kg-1(r=0.608, P=0.029), 0.003 mg P·kg-1(r=0.528, P=0.066), and 0.036%(r=0.863, P=0.002) in the 0~20 cm soil depth under manure incorporations each year, which were 3.3-, 6.0- and 1.2-fold greater than those under single chemical fertilizer application, respectively. The changes of soil DPS also increased linearly with the changes of soil P. In the 0~20 cm soil depth, the increments in DPS per 1 mg P·kg-1 increase in total P, Olsen-P, and CaCl2-P were 0.13%, 0.42%, and 7.78%, each year, respectively. In 20~40 cm soil depth, there was no significant linear correlation between the increases of soil P, DPS and P surplus. However, the difference of increase rates between manure incorporation and single chemical fertilizer application tended to be greater in 20~40 cm soil depth than in 0~20 cm depth, suggesting that manure applications favored the movement of P to subsoil. Manure applications accelerated the increases of soil available P and DPS, which in turn promoted the losses of P. In conclusion, rational manure management is the key to mitigating non-point source pollution in intensive farming areas.