Effects of long term fertilization on rice grain qualities and soil fertility factors 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 characters of rice grain quality and the factors of soil fertility. The results show that compared with the control (No fertilization, CK), total essential amino acid contents of rice grain in the treatments of chemical fertilizer plus cattle manure (NPKM), chemical fertilizer plus straw (NPKS) and chemical fertilizer (NPK) are significantly increased by 256%, 161% and 131% respectively. Contents of coarse protein and starch are also 111-141 and 23-39 percentage points higher, respectively, with the most significant effect found in the NPKM treatment. Likewise, the N and P contents of rice grain are significantly higher in the NPKM, NPKS, NPK treatments compared with the CK, particularly with an increase of 261% and 311% in the NPKM treatment. Moreover, the Ca，Mg and S contents of rice grain in the NPKM treatment are increased as well compared with the CK treatment. The amino acid content of rice grain is significantly and positively correlated to the N, P, Mg and S contents of rice grain, and the starch content of rice grain is significantly and positively correlated to the N, Ca and S contents. Soil organic matter and nutrient availability(particularly K) are increased in the NPKM, NPKS and NPK treatments compared with the CK. Furthermore, the key fertility factors including soil organic matter, available N and available P are significantly and positively correlated with amino acid and starch contents of rice grain, and soil available N and available P are significantly and positively correlated with N content and P content of rice grain, respectively. In conclusion, the NPKM treatment is the best fertilization regime for yellow paddy fields, considering overall effects of fertilization on rice yield, grain quality and soil fertility.