EFFECTS OF LONG-TERM FERTILIZATION ON SOIL CARBON, NITROGEN, PHOSPHORUS AND RICE YIELD

Abstract

□ Fertilization plays an important role in soil fertility and rice yield. A long-term (1990–2006) field experiment was conducted at a typical subtropical hilly agriculture region in south central China. The objectives of this study are to investigate the effects of long-term fertilizations on i) accumulations and distributions of soil carbon (C), nitrogen (N) and phosphorus (P) in different sizes of water-stable aggregates (WSA); ii) dynamic change of soil C, N, and P over years; and iii) the rice yield. Application of organic materials (OM), especially in combination with chemical fertilizers, increased soil organic C (SOC), soil total N (N_T), and soil total P (P_T) concentrations in all sizes of WSA, and they more concentrated in WSA (>1 mm). However, single chemical fertilizers had little impact on SOC and N_T. There were significantly positive correlations between SOC and N_T in each size of WSA, (r≥0.977, n = 15, P < 0.01). It illuminated that application of organic materials benefited the conservation of soil nitrogen. However, application of organic materials had less impact on P_T. Variation of C/P was larger than C/N. P_T was mainly affected by input of phosphorus. Data over years showed that SOC and N_T continued to rise, whereas P_T tended to decline irrespective of treatments. Furthermore, economical chemical fertilizers application combining with green manure and half straw returning (NPK_e + SR) can produce approximate effects on P_T as conventional dose of chemical fertilizers (NPK_c). Average rice yield of NPK_c for 17 years was 9399 kg ha⁻¹. Compared with NPK_c, OM decreased yield by only 4.4%, which indicated that traditional organic fertilization could obtain relatively high yield. NPK_e + SR obtained approximate yield as NPK_c did, which showed that green manure and half amount of straw effectually reduced chemical fertilizers by about one third.

Keywords:

• long-term fertilization
• carbon
• nitrogen
• phosphorus
• rice yield

ACKNOWLEDGMENTS

This study was funded by the National Natural Science Foundation of China (41090283) and the International Science and Technology Cooperation Program of China (2012DFB30030).