| As a kind of farming practices with economical and environmental merits, the conservation tillage in comparison to traditional farming has many advantages. Just because of these advantages, the countries all over the world have been making strong promotion. Although in China there has been a lot of achievements on conservation tillage research work in the past50years. It was still lack of the researches about change trend of crop yield and soil fertility in condition of long-term straw mulching and different fertilizer rates in two season rotation paddy, the researches about the optimal soil nutrient management in condition of conservation tillage. And based on this reason, this paper were to research the influence of different fertilizer rates to crop yields and soil fertility changes of conservation tillage, to provide the theory basis and the technical support for high yield fertilization and nutrition management of conservation tillage farmland. The main research results of this test obtained as follows:1. The effects of Nitrogen and potassium fertilizing on rice yield were good. Relative to the lowest nitrogen and no-potassium treatments, the average annual increase rate of rice yield of the optimal treatment150-60-90kg N-P2O5-K2O/hm2were respectively5.7%and5.9%, and the average annual increase rate of the application of phosphor fertilizer was0%; The effects of NPK fertilizer on wheat yield were good. Relative to the lowest nitrogen, no-phosphate and no-potassium treatments, the average annual growth rate of wheat yield of the optimal treatment180-75-90kg N-P2O5-K2O/hm2were respectivelyl2.6%,4.7%and9.2%.From the aspect of the annual production of rice and wheat, the rice and wheat yield significantly increased after straw mulching, the average annual growth rate were5.3%and12.1%respectively. Straw mulching in single season could save at least60kg N/hm,60kg P2O5/hm and45～60kg K20/hm2more than single application of chemical fertilizer treatment. The crop yield was higher than or equivalent to the single application of chemical fertilizer. Years of field trials showed that in the rice season the best fertilization scheme was150-60-90kg N-P2O5-K2O/hm2, namely the best fertilization ratio for1:0.4:0.6. The best wheat fertilization scheme was180-75-90kg N-P2O5-K2O/hm2, namely the best fertilization ratio for1:0.4:0.5.2. In rice-wheat rotation trial, comparing to conventional tillage, conservation tillage improved soil aggregates R0.25value, but decreased total porosity of the soil in depth of0～5cm and5～15cm by at least2.6%and4.3%, and increased soil compaction respectively by83.5Kp/cm2and101.7Kp/cm. Comparing to the control treatment,straw mulching not only could improve the soil aggregate content,but also could give rise to the vent capability of top soil, reduce the soil bulk density.The growth of the chemical fertilizer rate would cause the phenomena that0～5cm and5～15cm soil total porosity increase respectively by at least0.5%to0.7%and0.7～2.8%, and the soil bulk density reduce by at least0.03g/cm3and0.02g/cm3to0.05g/cm3, the top soil aggregates R0.25value improve significantly. Therefore the implementation of conservation tillage and reasonable increasing of chemical fertilizer has a significant effect to improve soil structure, improve soil aeration.3. In rice-wheat trial, conservation tillage gave rise to the content of all readily available nutrients and organic content of the top layer soil, especially in the0-5cm layer. The growth of the fertilization rate also could bring ascension to the total content of soil nutrients and organic matter content.To increase one of NPK fertilizer alone, it would cause the readily available nutrients content and available nutrients content of this element in soil rise up, and differences between treatments in0-5cm layer were significant, differences in5-15cm were not.4. In rice-rape rotation trial, relative to the lowest nitrogen, no-phosphate and no-potassium treatments, the average annual growth rate of rice yield of the optimal treatment165-60-90kg N-P205-K2O/hm2were respectively2.3%,1.0%and1.4%. Relative to the lowest nitrogen, no-phosphate and no-potassium treatments, the average annual growth rate of rape yield of the optimal treatment210-90-90kg N-P2O5-K2O/hm2were respectively10.3%,22.9%and2.1%.Straw mulching in single season could save at least30-90kg N/hm2,60kg P2O5/hm2and90kg K2O/hm2more than single application of chemical fertilizer treatment. The crop yield was higher than or equivalent to the single application of chemical fertilizer. Years of field trials showed that in the rice season the best fertilization scheme was165-60-90kg N-P2O5-K2O/hm2, namely the best fertilization ratio for1:0.5:0.7. The best rape fertilization scheme was210-90-90kg N-P2O5-K2O/hm2, namely the best fertilization ratio for1:0.4:0.4.5. In rice-rape rotation trial, conservation tillage made the top soil bulk density decrease by0.06g/cm3～0.24g/cm3, total porosity increase by5.0%to7.8%, soil aggregates R0.25value increase by2.05%and15.20%, while the control treatment played an opposite effect. In addition, under conservation tillage, the effect of increasing chemical fertilizers on soil physical indicators was not significant.6. In rice-wheat trial, the straw mulching gave rise to the content of all readily available nutrients and organic content of the top layer soil, especially in the0-5cm layer soil. But improving the fertilizer rates would decrease organic matter content. But nitrogen and phosphorus content were increased. |
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