Effects of longterm fertilization on contents of Zn, B, Cu, Fe and Mn in ricegrain and soil in yellow paddy fields of southern China

Based on data collected at the 26th year of a long term fertilization experiment in the yellow paddy in Fujian, we investigated the influences of different long-term fertilization regimes on the contents of micronutrients in rice grain and soil. The results show that compared with the control (without fertilization, CK), the contents of Zn, B and Cu of rice grains under the treatments of chemical fertilizer plus cattle manure (NPKM), chemical fertilizer plus straw (NPKS) and chemical fertilizer (NPK) are all increased more or less, especially under the treatment of NPKM which are increased by 14.3%, 25.1% and 465.2%, respectively. The contents of Mn of grains are also improved more or less under the NPKM and NPKS treatments, however, the Fe contents of grains are all significantly reduced in all fertilization treatments. Applications of the fertilizers, especially the NPKM and NPKS, increase the uptakes of grain micronutrients. There are declining trends of the available B, Fe, Zn and Cu contents of soil in the NPK treatment compared with the CK, moreover, in the NPK treatment, the available Zn and Mn contents of soil are decreased by 36.4% and 24.6%, respectively compared with the initial soil test. In contrast, the dropping tread was mitigated in the NPKM and NPKS treatments for above micronutrient. Applications of the NPKM, even increase available Zn, B and Mn contents of soil by 46.6%, 52.0% and 43.0% compared with the CK, respectively, which shows significant differences. The contents of organic matters are significantly and positively correlated to B, Cu and Zn contents of grains, and the amino acid and coarse protein contents of grains are significantly and positively correlated to the Zn contents of rice grains. In conclusion, the chemical fertilizers combined with cattle manure or straws，not only increase the micronutrient contents of rice grains, yields and some nutrient quality, but also mitigate the dropping trend of the micronutrient contents of soil to a certain extent, which is more suitable fertilization pattern for yellow paddy fields of southern China.