长期施肥对土壤有机质积累的影响

20年的NPK施肥定位试验，有利于深刻揭示土壤肥力特征与营养平衡规律。以位于黄淮海平原的中国科学院禹城综合试验站为例，探讨和估算了长期定量施肥对冬小麦（TriticuspaestvumL．）、夏玉米（ZeaMaysL．）生长和土壤有机质（SOM）的影响。结果表明，长期的N、P肥配施或N、P、K均衡施肥，可显著增加SOM储量，并且后者要优于前者；SOM增加主要集中在0-20cm深度的土层，40-60cm基本不变；生物量对SOM储量变化影响明显，NPK，NP处理作物生长良好，作物残体输人明显优于其他处理；0-40cm可以代表该区用以计算土壤固碳潜力，并且在N、P、K均衡施肥条件下，0-40cm土层中SOM储量长期以来持续增加，并未达到上限，每年的平均固碳速率（以C计）达182．8kg·hm-1，约是全球平均水平的1．5倍，全国平均水平的1．1倍。华北平原若按N、P、K均衡施肥，农田土壤每年固碳潜力将达到1．6-2．4Tg·a-1。

Effects of long-term fertilization on soil organic matter accumulation

A 20-year long-term fertilization test is conducive to reveal the characteristics of soil fertility and nutrition balance law. Taking Yucheng Comprehensive Experimental Station which is located in the Huang-Huai-Hai Plain for example, this paper explores and estimates the impact of long-term quantitative fertilization on growth of winter wheat （Triticusp aestvum L.） and summer maize （Zea Mays L.） and soil organic matter（SOM） accumulation The results are shown as follows： Long-term application of nitrogen（N） combined with phosphorus（P） or balanced fertilization of N, P, potassium（K） can significantly increase SOM reserves in the soil, and the latter exerts a more pronounced effect. SOM increase is mainly concentrated in the 0-20 cm depth of soil, and 40-60cm remaines basically unchanged. Biomass plays an important role in the change of SOM reserves, crop grows well with the treatments ofNPK, NP, and crop residues input is superior to those with other treatments. The depth of 0-40 cm can represent soils in the region to calculate the potential for carbon sequestration, the SOM reserves in the depth of 0-40 cm is continued to increase for a long time under the condition of balanced fertilization of N, P, K, and don＇t reach the upper limits. Average annual carbon sequestration rate of the soil is 182.8 kgC/hm2, which is approximately 1.5 times of that of the global average, 1.1 times of the national average. If North China Plain tries to transform soil with the measure of balanced fertilization of N, P, K, then the annual carbon sequestration potential of agricultural soils will reach 1.6 to 2.4 Tg.a-1.