Studies On Fertility Properties Of Degraded Soils Caused By Continuous Unreasonable Fertilization Practices And Their Restoration

Based on long-term experiments on soil fertility controlling in Hunan Province, the effect of different fertilization treatments on soil fertility characteristics and rice yield were studied with soil sampling and analyzing. And also, restoration effects of different fertilization measures on 3 degraded soils, which were caused by continuous unreasonable fertilization practices, were studied with pot experiments. The results were followed as below:1. The contents of total P, total K, alkali-hydrolyzable N, available P and K in the soils without fertilization in long term location experiments in 2004 was visibly less than that in the original soils before experiment, the content of soil available silica and CEC was less than that of the NPK treatment and the treatment of NPK combined with organic manure. The content of total P and available P in soil without P fertilization decreased to a very low level, and was less than the critical P value in soilst; while the contents of both soil total K and available K decreased significantly under the condition of long-term no K fertilizer. The content of soil organic matter, available silica, CEC, N, P and K nutrients increased evidently under the condition of chemical N, P and K fertilizers combined with organic manure. Those treatments of CK( without fertilization in long term) , NK(single nitrogen and potassium fertilization) all have lower yields. Treatment of OM30 and OM60 (combined with nitrogen, phosphorus, potassium and organic manure) could got sustainable high yield.2. After 1 year's restorations with 5 different fertilizations, the fertility of the soil treated with continuous no fertilization for a long time, has been improved to some extent. Of wihich 2 applying special rice fertilizer treatments (CK-ZY, CK-ZYM) has improved the soil fertility best, but they coused more serious nutrient leaching loss. The chemical NPK fertilizer combined with organic manure treatments CK-ZYM CK-NPKM could apparently enhance soil organic matter concentration and rice yield.3. For the soil treated with continuous no P fertilization, applying organic manure (NK-NKPM, NK-NKHPM) could increase soil organic matter and alkali-hydrolyzable N contents evidently. And heavy P fertilization could apparently enhance soil total P, available P and available K contents. Applying heavy P fertilizer combined with reasonable N, K fertilizer and organic manure(NK-NKHPM) could increase soil organic matter, total N, P and K,...