| Phosphate fertilizer is easily fixed to the difficult-to-use phosphorus such as Ca10-P after being applied to the soil,which is not conducive to crop absorption and utilization.When the phosphorus input is higher than the phosphorus uptake of the crop,the soil phosphorus will be in a surplus state,causing waste of phosphorus resources and Pollution of the soil environment.In this paper,fluvo-aquic soil which is the most important soil type in the Huang-Huai-Hai Plain was used as a material to study the effects of long-term fertilization molds on soil inorganic phosphorus in fluvo-aquic soils through a 28-year long-term field experiment,and to provide a theoretical basis for the adjustment of fertilization in farmland production.The main results are as follows:1.Effects of main inorganic phosphorus components in soil in long-term different fertilization modesWhen the phosphate fertilizer was not applied for a long time,the total amount of inorganic phosphorus in the soil decreased by 13.7%,and Ca2-P,Cas-P,Al-P and Fe-P decreased by 68.1%,30.2%,48.9%and 40.9%,respectively.There was no significant change in Ca10-P and O-P.When the phosphate fertilizer is applied for a long time,the total amount of inorganic phosphorus in the soil increases by 35.3%～121.1%.Due to the decrease of the amount of applied P,the soil Ca2-P in the fertilization mode increased rapidly in the first 13 years,and the characteristics of different changes in the last 15 years.In the 13 years before the experiment,the soil Ca2-P increased by 123.4%～541.5%.In the last 15 years,the application of chemical fertilizer,straw returning and organic-inorganic combined soil Ca2-P was maintained at 25.8～28.6 mg·kg-1,48.2～57.8 mg·kg-1.Since no organic fertilizer was applied since 2012,the soil Ca2-P with high organic and inorganic application was significantly reduced,with an annual decrease of 2.1 mg·kg-1.When applying phosphate fertilizer for 28 consecutive years,soil Cas-P increased by 177.6%～679.6%;soil Al-P increased by 172.5%.w392.9%;soil Fe-P increased by 127.4%～236.6%,Calo-P and O-P had no significant changes.When the phosphate fertilizer is not applied for a long time,the soil has a eumulative deficit of P 100 kg·hm-2,soil Ca2-P,Cas-P,Al-P,Fe-P,Ca10-P,O-P decrease by 1.7,4.5,2.7,2.5,0.9,6.5 mg·kg-1,respectively.When long-term application of phosphate fertilizer,soil cumulative surplus P 100 kg hm-2,soil Ca2-P,Ca8-P,Al-P,Fe-P,Ca10-P,O-P increased by 1.2～4.5,14.1～45.8,3.1～11.5,2.3～10.8,-0.6～14.8,0.6～7.2 mg·kg-1 respectively.2.Effects of long-term different fertilization modes on the activation coefficients of total phosphorus,available phosphorus and phosphorus in soil.For the 28th consecutive year,the total phosphorus in the soil without phosphate fertilizer decreased by 13.9%;the total phosphorus in the long-term application of phosphate fertilizer increased by 49.8%～132.8%.From the average of available phosphorus and PAC in the 28 years of fertilization,the available phosphorus and PAC in the soil without phosphate fertilizer decreased by 0.84 and 0.63 times,respectively.The soil available phosphorus in the four long-term phosphorus application modes increased by 1.06～5.70 times,and the soil PAC increased by 0.60～2.95 times than the initial value.For the 28th consecutive year,the phosphorus accumulation deficit of phosphate soil was 468.3 kg·hm-2,the soil was reduced by P 100 kg·hm-2,the soil available phosphorus decreased by 1.6 mg·kg-1,and PAC decreased by 0.26%.Single application of chemical fertilizer,straw returning to field,organic and inorganic application for 28 consecutive years,the soil accumulated surplus of 290.7,369.4,1946.1～2627.1 kg·hm-2,and soil cumulative surplus P 100 kg·hm-2,soil available phosphorus increased by 1.85～4.33 mg·kg-1,the soil phosphorus activation coefficient increased by 0.06%～0.48%.3.Contribution of different fertilization modes to soil inorganic phosphorusSoil Ca2-P,Ca8-P,Al-P and Fe-P are sensitive to phosphorus input and are not sensitive to changes in phosphorus input.The higher the phosphorus input,the higher the content.Soil Ca10-P and O-P are not sensitive to changes in phosphorus input and input.Straw phosphorus and organic fertilizer phosphorus can increase the content of easy-to-use phosphorus in soil,reduce the content of difficult-to-use phosphorus,and the best effect of organic fertilizer phosphorus.However,the effects of soil Ca10-P and O-P are basically the same.4.Rational phosphorus application based on phosphorus level in fluvo-aquic soilAccording to the relationship between soil available phosphorus and phosphorus surplus rate under different fertilization modes,the years required for each fertilization mode to reach the soil available phosphorus content(25 mg·kg-1)were predicted.The available phosphorus is from 6 mg·kg-1 to the target content of 25 mg·kg-1,and the single application of chemical fertilizer(P 77 kg·hm-2 per year)takes 11 to 12 years,and the straw is returned to the field(P 90 kg·hm-2 per year)It takes 12 years,and it takes 5 years for organic-inorganic compound application(P 140 kg·hm-2 per year),and 3.5 years for high-volume organic-inorganic application(P 210 kg·hm-2 per year).The available phosphorus decreased from 50 mg·kg-1 to the target content of 25 mg·kg-1,the application of chemical fertilizer and straw returning to the field(reduced P 30%)took 17～18 years;organic and inorganic application(reduced P 30%)It takes 9 to 10 years;a high amount of organic and inorganic compound application(reduction of P 70%)takes 5 to 6 years. |
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