DYNAMIC AND BALANCE OF SOIL NUTRIENTS UNDER LONG-TERM FERTILIZATION CONDITIONS I . Effects of fertilization on accumulation of soil humus and its qualities

Long- term trials of the effects of manure and chemical fertilizers on the accumulation of soil and its qualities were conducted in 1986~1991 in Russia and other places. The main results are as follow: 1.Application of manure has a better effect than NPK fertilizers on accumulation of soil humus. With the exception of sandy soil, the increase of soil humus was mainly in 0~60cm, and litter effect in lower layer. 2.Long-term application of manure and NFK fertilizers increased the content of component I of humus acid (free form and active R2O3 combined form) and the relative transport velocity, however, the content of component II of humus acid which combined with Ca2+ was decreased. The combination between component II of humus acid and Ca2+ declined, the dissolution of humus in water increased and the humus leached easily in the case of heavy rain or irrigation. 3.Application of manure and NPK fertilizers increased the content of soluble humus, and the adverse effect caused by high salinity on the crops under dry conditions could be reduced. 4.Long-term fertilization increased the hydrophilicity of soil, and the expansion volume, constant of expansion velocity, water absorbing capacity and the surface area of soil were also improved to a certain degree. The effects were less in the sandy loam soil than in silt loam and clay loam soil. 5.The content of methyl functional group of humus is an important index to evaluate the humification of soil. The experimental results showed that the content of methoxyl increased by 46%~300% in the acid soil with low fertility and by 17%~32% in the non-acid soil with high fertility under long-term fertilization condition.