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Effects of rainfall and fertilization on water quality of the Yujia River watershed in the northern Qinling Mountains
Received:July 06, 2016  
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KeyWord:rainfall;fertilization;nitrogen;phosphorus;organic matter;spatial distribution
Author NameAffiliationE-mail
GUO Ze-hui Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resource and Environment, Northwest A & F University, Yangling 712100, China  
LIU Yang Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resource and Environment, Northwest A & F University, Yangling 712100, China  
HUANG Yi-mei Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resource and Environment, Northwest A & F University, Yangling 712100, China ymhuang1971@nwsuaf.edu.cn 
YAN Jiang-tao Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resource and Environment, Northwest A & F University, Yangling 712100, China  
TENG Fei Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resource and Environment, Northwest A & F University, Yangling 712100, China  
WANG Yong-bin Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resource and Environment, Northwest A & F University, Yangling 712100, China  
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Abstract:
      With the purpose of investigating the mechanisms of how rainfall and fertilization affected the quality of ground water, we selected a typical Yujia River watershed in which eight water-sampling sections representing the watershed characteristics. Water quality(N, P and CODMn) was monitored after various rainfall intensities on Kiwifruit plots(main economical crop for the local) with three key fertilization time-points in early-spring, summer and late autumn. The results show that in Yujia River watershed the concentration of total N averages 6.51 mg·L-1(range:4.53~11.45 mg·L-1), the mean values for the concentrations of total P and CODMn are 0.312 mg·L-1(range:0.004~1.377 mg·L-1)and 3.15 mg·L-1(range:0.89~11.23 mg·L-1) respectively. As for the load of fertilization applications to water quality, the mean load of total N during early-spring fertilization is 227.03 g·d-1, with an increase of 73.34% to the whole watershed, the average load of total P during the summer fertilization is 11.36 g·d-1, with an increase of 117.36%. With regard to rainfall, the loads of the total N, total P and CODMn, during heavy rainfall period are 228.10 g·d-1, 9.94 g·d-1 and 174.53 g·d-1, with an increase of 35.93%, 84.31% and 69.65%, correspondingly. The concentration of total nitrogen and total phosphorus show a positive relationship with rainfall intensity. Therefore, as revealed by our data, rainfall is a main meteorological parameter to cause nitrogen loss in this region. Fertilization during early-spring contributes substantially to the increased N concentration, and the risk of water P pollution becomes stronger especially in summer fertilization. There is higher CODMn contamination after heavy rain in early-spring. The combined effect of the rainfall and fertilization is the main factor causing the non-point pollution in Yujia River watershed. The main polluting area of the watershed was middle-part concentrated, which was mainly caused by kiwifruit fertilization, additionally, pollution from local living-residents may also be a reason to the total pollution.