长期有机物循环下红壤稻田的产量趋势及其原因初探

对长期定位的红壤稻田中CK（无肥）、N、NP、NPK及C、N＋C、NP＋C和NPK＋C等8个处理下的早、晚稻产量随时间的变化趋势（1990-2004年）及其原因进行了分析。结果表明，各处理下早稻产量均没有随时间呈显著上升或下降，晚稻产量比早稻产量的下降趋势更明显。其中，在施N肥和NP肥处理下晚稻产量呈显著下降（P〈0．05），NPK处理下产量的下降趋势也近似显著（P=0．097）。产量趋势受到了有机物循环、施肥和气候变化等因素的影响。有机物还田促进了土壤有机质的积累，改善了养分的供应，从而提高了稻谷的产量。长期不平衡施肥可能是造成N、NP、N＋C和NP＋C等处理产量呈下降趋势的主要原因，而较低的初始产量和较高的基础肥力可能使得CK和C处理的产量在较长时期内维持稳定。早、晚稻产量主要与其生育期内的积温和日照时数相关，而日照时数的减少可能是导致晚稻产量呈下降趋势的主要原因。

Yield Trends and Reasons for Their Change in Red-soil Rice Field with Long-term Organic Matter Circling

Trends of early- and late-rice yields under 8 different treatments, including CK(no fertilizer), N, NP, NPK, C, N+C, NP+C, and NPK+C, and the reason for their changes with years(1990-2004) were analyzed in a long-term fixed red-soil rice field. The results indicated that early-rice yield under different treatments did not significantly increase or decrease with time, but late-rice yield tended to decrease, compared with early-rice yield. Late-rice yield in treatments with N and NP significantly decrease (P<0.05), and the yield with NPK declined nearly significantly (P=0.097). Change of yield trends over time was influenced by organic matter circling, fertilization and climate. Organic matter circling increased accumulation of soil organic matter, supply of nutrients in soil and yield positively. Long-term unbalanced fertilization was probably the main reason for the yield declining in the treatments with N, NP, N+C, and NP+C However, lower initial yield and higher initial soil fertility probably maintained the yield for a long time in treatments with CK and C. Rice yield was mainly related with accumulated temperature and sunshine during their growth periods, and the reduction of sunshine over time was probably the main reason for the yield declining of late-rice.