Effect Of Long-term Fungi Residue Application On Phosphorus Forms And Its Availability In Paddy Soil

Being an essential nutrient element, phosphorus has been widely applied in agriculture in order to improve crop yield. However, too much phosphorus fertilizer application could bring serious problems such as land and water pollution. On the other hand, the rapid development of mushroom industry in recent years lead to vast residue produced, but the discarding of these residues as waste also caused increasingly environmental pollution. According to some studies, the mushroom residue contains large amount of lignin and mineral elements, such as phosphorus(P), which can be used as a good source of agricultural organic fertilizer and soil amendment. In order to investigate the effect of mushroom residue application on soil P content as well as P availability in soil, this study was carried out with a long-term field experiment on Wulangyuan farm, Wangdian town, Jiaxing City, Zhejiang province.Field experiment began from May, 2010 until May, 2014. Three levels of fungi residue and fertilizer treatments were carried out, a total of nine treatments(treatment 1: C0F0; treatment 2: C0F50; treatment 3: C0F100; treatment 4: C50F0; treatment 5: C50F50; treatment 6: C50F100; treatment 7: C100F0; treatment 8: C100F50; treatment 9: C100F100, where C represents chemical fertilizer, F represents fungi residue). By analyzing changes of soil P forms, the changes of inorganic and organic P contents and their contribution to total P, the effects of fungi residue applicatuon on P nutrient balance in rice-soil ecosystem were revealed. The main results were as follows:(1) Different forms of inorganic P were analyzed according to modified Hedley classification method. The results showed that: Different treatments had different effects on these four inorganic P contents. Compared to the only application of fungi residue or fertilizer, combination of fungi residue with fertilizers significantly increased the content of the high activity of inorganic phosphorus. i.e.NaHCO3-P., but had no significantly effect on HCl-P and residue P which are the two high stable P forms in soil. The inorganic P was decreased continually in the treatment with no fertilizer application due to the abstraction of crop every year.(2) According to the modified Hedley classification method used in present study, inorganic P was the main form soil P in the upper layer(0-20cm) in this paddy soil, accounting for 77.8% ~ 84.2% of total P, and organic P was only 15.8% ~ 22.2%. The main P was high stable P(residual P),accounted for 53.4%; followed by moderate reactive P(NaOH-P, HCl-P), with proportion of 39.5%; active inorganic P was minimum(NaHCO3-P), only 10.1% of total P content. Long term fungi residue and chemical fertilizer application resulted in soil P increase, both for inorganic and organic P. Compared with background soil, changes of different fractions of soil P were same trend in the treatment with no fertilizer applied, i.e., high available P(NaHCO3-P and NaOH-P) significantly decreased, whereas the high stable P, HCl-P and residual P, showed no significant change.(3) Long-term fungi residue and chemical fertilizer application could significantly increase the total P content in paddy soil, but different treatment had different increasing rate on soil total P content. Only chemical fertilizer application had significant improvement on total soil P when compared with only fungi residue application, which the latter showed no significant increase.(4) Long-term fungi residue and chemical fertilizer application could significantly increase the organic P content in soil. Only application of chemical fertilizer had no significant increase in soil organic P content, whereas only fungi residue application significantly increased soil organic P content. The long-term application of chemical fertilizer could significantly increase soil available P, but long-term application of mushroom residue had no significant effect on soil available P.In summary, reasonable ratio of fungi residue and chemical fertilizer application would lead to high yield crop production and saving P fertilizer.