我国不同区域农田养分平衡对土壤肥力时空演变的影响

Effect of Nutrient Balance on Spatial and Temporal Change of Soil Fertility in Different Agriculture Area in China

区域农田养分盈亏是驱动农田土壤肥力时空变化的主要因素。对我国6个农业生态试验站(海伦、沈阳、栾城、长武、常熟、鹰潭)站区农田土壤肥力在近年来时空演变的研究表明,除了海伦站黑土和常熟站水稻土的有机质和全氮平均含量下降外,其他站区均呈现增加趋势,主要原因是黑土和乌栅土有机质和全氮含量较高,目前农田有机C和N投入水平无法维持其平衡;6个站区土壤速效磷有增有减,而土壤速效钾除了栾城和鹰潭站区域外均呈降低趋势。从站区农田养分的年平衡与土壤养分的年变化量关系看,农田氮、磷、钾的盈亏量决定了土壤养分的变化方向。土壤有机碳和全氮的初始含量过高(分别超过15.1 g/kg和1.60 g/kg)时,也会导致其年际间的变化方向从增加变为降低。农田氮素盈亏量与土壤全氮变化量之间相关不显著,主要是由于化肥投入和作物籽粒输出的农田氮平衡不能完全代表土壤氮素的真实盈亏情况;而农田磷素和钾素的盈亏量与土壤速效磷和速效钾的年变化量的显著相关。

Nutrient budget of farmland system is a driving force on the change of soil fertility. The spatial and temporal change of soil nutrient contents in recent years was studied on a regional scale in 6 experiment stations in Chinese Ecological Research Network. The results showed that the average content of soil organic carbon and total nitrogen increased except in Hailun and Changshu Experiment Station areas where the main soil is black soil and paddy soil. The possible reason is that C and N balance of the farmland system was unable to maintain the higher content of soil organic carbon and total nitrogen in the two kind of fertile soils. Soil average available P contents increased or decreased without a common temporal trend in 6 stations, but soil average available K contents mainly decreased except in Luancheng and Yingtan Experiment Station areas. The nutrient budget of farmland system decided the direction and extent of temporal change of soil nutrient contents. For soil available P and K, their annual change amount showed a significant positive relationship with annual budget of farmland system. However, such relationship did not exist for soil total N because the balance only considering the input from fertilization and nitrogen biofixing and the output from crop uptake are unable to express the real budget of N in farmland system. Also, the initial contents of soil organic carbon and total nitrogen affect their change direction, which will turn from increase to decrease when the initial content of soil organic carbon and total nitrogen is larger than 15.1 g/kg and 1.60 g/ kg, respectively.