| It’s more and more important to improve the utilization rate of phosphorus in organic wastes because of the limitation of phosphorous resources. Long term use or abuse of organic materials may lead to the accumulation of soil phosphorus, while corps can take in only a minimum of it. Meanwhile, the increase of phosphorus in farmland runoffs can also increase the risk of eutrophication. Therefore, it’s necessary to figure out the mechanisms of transformation of phosphorus in organic materials treated soils, which makes a big difference to improve the bioavailability of phosphorus and the utilization rate of organic materials. This study investigated the transformation of phosphorus in organic material applied soils and its effects on the growth of crops and environmental impact.The obtained results are helpful to find theoretical evidence for choosing and applying organic materials and improve the utilization rate of phosphorous in organic materials. In the study,we firstly analyzed the characterizations of phosphorus forms in 7 organic materials including cattle manure(NJD), compost of sewage sludge(WD), biogas residues of pig manure(ZZ), biogas residues of cattle manure(NZ) and 3 composts of rural daily garbage(NSLD). Then we chose four of the materials to conduct a laboratory incubation experiment and a pot culture experiment to investigate the impact of different organic materials on the microbial biomass of soils, the mineralization of organic phosphorous and the availability of plants. The results are listed as follows:(1) The research of characterization of phosphorus forms in different organic materials shows that there is a great difference in total phosphorus (TP) and the total phosphorus of various forms (Pt) among different organic materials. The contents and proportions of phosphorus fractions in ZZ, NZ, NJD and WD follows the order of HCl-P> Residues-P>NaHCO3-P>NaOH-P>H2O-P, while follows the order of HCl-P> Residues-P>H2O-P>NaHCO3-P>NaOH-P in the three NSLDs. Most of P in organic materials exists in the forms that are easier to be extracted by strong extracting agents like HCl, which is difficult to be absorbed by plants. Phosphorus in all organic materials exist mainly in inorganic phosphorous. The higher proportions of inorganic phosphorus in NJD than those of NZ demonstrate that composting process is benefit for the mineralization of organic phosphorus in organic materials and thus improving its availability.(2) The soil culture experiment shows that organic materials can obviously increase the microbial biomass of soil carbon, nitrogen and phosphorous compared with the control. Soil from NZ treatment has a higher microbial biomass of soil carbon, nitrogen and phosphorous than those of other organic materials at the end of incubation due to its rich organic carbon and high C/N, which offers microorganisms a rich source of carbon. Meanwhile, uorganic materials can promote the mineralization of phosphorous and improve the contents of Olsen-P in soil. The WD and composted NJD have better effects on neutral and calcareous soils. Therefore, aerobic compost can be applied for agricultural use for the utilization rate of phosphorous. Organic phosphorous of fertilized soils increases compared with the control, but they decrease as a whole in the mass, which shows that phosphorous in soils amended with organic materials mainly mineralizes in the process of fixation and mineralization.(3) The pot culture experiment shows:The pH of fertilized soils decreases and the pH of soils with chemical fertilizers goes down much more than other organic materials. The decreasing range of pH of soils with organic materials doesn’t reach significant level. After application of organic materials, the organic matters of 3 soils increase obviously, The sample amended with ZZ has the biggest increasing range and sample amended with ZZ has the smallest. Phosphorus content such as fertilizing the soil total phosphorus has no obvious difference, but a significant increase than control.The fertilizer treatment increases the Olsen-P in soils to a significant level, which shows that the organic materials improve the availability of soil phosphorous. Different fertilizer treatments have different impacts on the plant heights, roots and shoot dry weight of corns. The plants applied with HF and WD grow faster than those in other treatments, while plants applied with 2 biogas manures grow relatively slower. The utilization rates of different fertilizer treatment make a significant difference. The utilization rate of phosphorous in NZ treatment is much smaller than in other treatments, while the NJD with aerobic compost and WD have bigger ones. |
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