Effects of Long-term Located Fertilization on Evolution of Available Phosphorus and Phosphorus Pool in Shandong Fluvo-aquic Soil

This study was conducted to investigate the effects of long-term located fertilization on soil phosphorus,the changes of soil available phosphorus(OlsenP),the evolution of soil total phosphorus(TP)and the ratio change of Olsen-P to TP(PAC)by 33-year fertilization experiments in winter wheat-summer maize rotation system in Shandong fluvo-aquic soil.Eight treatments were designed as no fertilization(CK),nitrogen fertilizer(N),nitrogen and phosphate fertilizer(NP),nitrogen and potassium fertilizer(NK),phosphate and potassium fertilizer(PK),nitrogen-phosphate-potassium fertilizer(NPK),reduced NPK fertilizer(N(15)PK),and increased NPK fertilizer(N_(25)PK).Meanwhile,eight organic fertilizer-added treatments were designed based on the application of inorganic fertilizer the same as the above ones.The results showed that TP,Olsen-P and PAC of treatments added with organic fertilizer were higher than those without organic fertilizer,and those of the treatments applied with phosphate fertilizer were higher than those of no phosphate fertilizer.With the increase of years,soil P pool decreased due to crop absorption,nutrient loss and morphological transformation and other causes under the treatments of without and only phosphate fertilizer,while remained stable under the treatments added with organic fertilizer.The PAC values were generally lower in fluvo-aquic soil,and it could be improved by the application of organic fertilizer.On the whole,the application of chemical phosphate fertilizer combined with organic fertilizer could improve the phosphorus content in soil and ensure the supply of phosphorus nutrition.This study would provide scientific basis for fertilization management and soil fertility in fluvo-aquic soil.

Storage and Spatial Variation of Phosphorus in Paddy Soils of China

Due to the growing concern about the agricultural phosphorus (P) losses pollution, an in-depth understanding of P in paddy soils of China would be helpful in providing a national perspective of the environmental impact of P cycling and fertility on China's farms. In this study, we evaluated the P storage and the P density of paddy soils in China, characterized the spatial variations of P among the subgroups of paddy soils and soil regions in China, and evaluated the P data using GIS-based analysis, which included a newly compiled 1:1 000 000 digital soil map of China, and using 1 490 soil profiles. The available and total P densities of paddy soils were 6.7 and 698.5 g m -3 , respectively. Overall in China, the total P storage within 1 m of paddy soils was estimated to be 330.2 Tg. The P density of paddy soils varied substantially with subgroups due to the different soil water regimes such as groundwater table and soil drainage. The P availability in paddy soils, especially in surface layer, was higher in high temperature and precipitation areas. Further research is needed to examine more anthropogenic impact factors, such as increasing use of chemical fertilizer.

Phosphorus and nitrogen in the soil interface between two plant residues differing in C/nutrient ratio:A short-term laboratory incubation study

In studies on the effects of mixing residues with different properties on decomposition rate and nutrient release,the extent of contact between the different residues is not known.In this study,we used an experimental design where crop residues were spatially separated by a layer of soil.Microcosms were set up using young faba bean residue(low carbon(C)/nutrient ratio,L)and mature barley straw(high C/nutrient ratio,H).The microcosms comprised of two caps of PVC tubes,each filled with moist soil.Between the two caps,there were three layers each separated from the others by fine nylon mesh with the middle layer being the moist interface soil.Microcosms had similar(H/H or L/L)or different(L/H)residue types,or only residue type(H/S or L/S)while the other cap had no residue.In treatments with only one residue,measured parameters,except microbial biomass P(MBP),were higher in L/S than H/S.In treatments with two residues,all parameters were lowest in H/H.In L/H compared to L/L after 14 days,available P and microbial biomass N(MBN)were lower,available N was similar and MBP was higher.After 28 days,available P and N were lower in L/H than L/L,but MBP and MBN did not differ.In L/H,measured resin P,MBP and MBN were higher than expected whereas available N was lower.The experimental design used in this study allows assessing the effect of residues on properties of the soil between them.