Changes of yields, soil properties and micronutrients as affected by 17-yr fertilization treatments

Author: Benyin Li ^{1, 2}, Mingbao Wei ³, Alin Shen ^1*, Jianmin Xu ², Hailin Zhang ⁴ and Fazheng Hao ⁵

Received 23 May 2009, accepted 26 September 2009.

Abstract

Plant essential and toxic microelement status in soil and crops can be affected by long-term fertilization practices. The main objective of this paper was to investigate the change of micronutrients and Cd in soil and brown rice after 17-yr cropping and fertilization treatments in Southeast China. The long-term fertilization experiment included treatments with different combinations of N, P, K and pig manure with or without straw incorporated. Soil pH, organic matter, available N, P, K and the contents of Cu, Zn, Fe, Mn and Cd in soil and brown rice were determined. Balanced chemical fertilizers (N, P, K) with the application of manure and incorporation of straw resulted in high available soil N, P, K, which produced highest yield of rice grain among the treatments. Manure application increased total Cu, Zn and Cd by 13-23, 5-8 and 138-162% and soil available Cu, Zn and Cd by 89-123, 61-71% and 212-225%, respectively, compared with their initial status. However, no such difference was observed for total soil Fe and Mn contents after 33 rice seasons. The Cu, Zn, Fe, Mn and Cd contents in brown rice were significantly affected by different longterm fertilization practices. The Cd contents in brown rice in three manure-applied treatments were 3 times (0.26-0.28 mg kg^-1) as high as that (0.08 mg kg^-1) in the control treatment, suggesting long-term application of pig manure from intensive livestock farms could result in Cd contents exceeding the upper limit of the criteria (> 0.2 mg kg^-1, National Standard for Food Hygiene). Attention should be paid to potential soil Cd contamination caused by long-term application of pig manure containing heavy metals.