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Effect Of Different Long-term Fertilization On Fertility Of Neutral Purple Soil

Posted on:2016-02-05Degree:MasterType:Thesis
Country:ChinaCandidate:M Y FengFull Text:PDF
GTID:2283330461968685Subject:Plant Nutrition
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Purple soil is widespread in the Sichuan basin. And neutral purple soil which is nutrient -riched and suitable for cultivation represents a specific and important land,, resource. However, the fertility of neutral purple soil has declined to some extent due to human activity such as fertilization and tillage during last decades. Therefore, integrative analysis for the influence of long-term different fertilization on integrated soil fertility of purple soil is essential for crop fertilization management and soil improvement with aim to sustain agriculture development in area of purple soil.In this study, we measured major indexes of soil fertility for soil samples collected,, from a long-term fertilization experiment at the national monitoring station of purple soil fertility and fertilizer efficiency in Chongqing. By doing this together with soil nutrient balance and crop yield, we quantified the fertility evolution of neutral purple soil under different long-term fertilizations and evaluated their integrated soil fertility and sustainability.The results showed that:(1) Neutral purple soil has relatively high fertility in our country. Field without fertilization for 20 years can still harvest yield of 4.9 t/hm2 (3.6 for rice and 1.3 for wheat). Long-term application of NPK fertilizer along or together with organic fertilizer can increase SOM, soil N status, soil available P and K, leading to high yield of rice and wheat and maintaining soil productivity and soil fertility of neutral purple soil. Whereas Unbalanced application of NPK fertilizer especially lack of N and/or P resulted in decline in SOM content and soil N, P and K supply capacity of neutral purple soil, and finally decrease crop yield and fertilizer use efficiency.(2) Nitrogen (N) fertilization is of importance to realize high yield of rice and wheat, but N fertilizer could not be applied along by year after year because this will resulted in continuous decrease in yield response and N use efficiency. Balanced application of N with phosphorous (P) and potassium (K) fertilizer increased crop N use efficiency with 37% for rice and 35% for wheat in average. Nitrogen balance in neutral purple soil was significantly related to amount of N input but had little relationship with soil total N and soil available N. This indicated that little N is retained in purple soil and N management should be paid more attention to feed the crops and avoid N loss to environment at the same time.(3) In rice-wheat rotation system, the accumulative recovery rate of P was 32%, indicating that nearly 68% of applied P fertilizer was built up in soil. It’s calculated that soil P surplus of 100 kg/hm2 will increase soil available P by 2.3 mg/kg. Considering the accumulation of soil available P, apparent balance of soil P and crop demand, maintained strategy (applied P rate equal to crop remove) is recommended for crop P management.(4) Compared with the soil before experiment, soil total K content had a decreasing tendency whether K fertilizer was applied or not. All fertilization treatments except NPK treatment with straw return (NPKS) resulted in depletion of soil native K. Therefore, long-term fertilization without K (NP) resulted in declined crop yield and consequently contribution of K fertilization to yield had increased from 7% in first 10 years to 12% in second 10 years. It was estimated that K rate (K2O) should be maintained at 282 kg/hm2 to sustain crop yield and soil K fertility. With the fact that China is poor in K resource, straw return would be an important strategy to reduce the soil K depletion and maintain soil K in areas with purple soil.(5) After 20 years of rice-wheat cropping, soil organic matter (SOM) in plow layer of neutral purple soil was kept same or improved slowly, but SOM content in sub plough layer (20-40 cm) declined obviously which may be associated with less organic material input due to shallow tillage and fertilization. Therefore, deep tillage and fertilization is necessary to maintain or improve the soil fertility of sub plough layer to maintain sustainable productivity of purple soil.(6) Long-term straw return with chemical NPK fertilizer (NPKS) had obviously positive effect on soil fertility and productivity compared with chemical NPK fertilization along. This treatment increased SOM and N content, and maintained soil K supply. This treatment also harvested the highest annual yield during in these years, which was 6% higher in rice yield and 2% higher in wheat yield when compared with chemical NPK fertilization along.(7) Neutral purple soil was obviously acidified due to chemical NPK application along or together with organic fertilizer. Rate of soil acidification was as high as 0.1 units per year under fertilization treatment containing chlorine fertilizers. In addition, soil acidification resulted in activation of some heavy metal elements in soil. Soil available plumbum and especially zinc and cadmium increased obviously with fertilization or not. For Sichuan basin, application of dolomite, limestone and other acidic soil conditioner to control soil acidification is recommended at filed scale.(8) Different long-term fertilization had substantially changed the integrated fertility of neutral purple soil as indicated by integrated fertility index (IFI). This index is significantly correlated with crop yields in 2001 and 2011, indicating the representation of IFI on integrative soil fertility. In the initial 10 years, values of IFI were increased by all fertilizations; whereas these values were decreased to some extent in all treatments except treatment with high fertilizer input in the second decade. Howere, the reason is unclear.
Keywords/Search Tags:Long-term fertilization, Integrated soil fertility, Neutral purple soil, Straw return
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