过磷酸钙对石灰性土壤有效磷及无机磷组分的影响

Effect of superphosphate on available phosphorus and inorganic phosphorus fractions in calcareous soil

为研究水溶性磷肥在石灰性土壤中的转化,采用室内土壤培养的方法,在土壤中分别添加过磷酸钙0、6.25、12.5、25、50和100 mg/kg干土(即P0、P6.25、P12.5、P25、P50和P100处理),保持土壤湿度为田间持水量的70%~80%,在25℃恒温培养箱中培养120 d。培养期间在第1、3、7、15、30、60和120 d连续采样,测定土壤Olsen-P、CaC_(l2)-P和各无机磷组分的含量。结果表明,在石灰性土壤中施用过磷酸钙能显著增加土壤Olsen-P和CaC_(l2)-P含量,在一定的培养时间内,过磷酸钙转化为土壤Olsen-P和CaC_(l2)-P的比例不随施肥量的变化而变化。随着培养时间的延长,土壤有效磷含量逐渐下降,尤其是培养前期(前7 d)土壤有效磷含量显著下降,之后下降速率减缓。施入土壤中的过磷酸钙主要转化为Ca_(2)-P和Ca_(8)-P(两者之和约占90%),其次是Al-P和Fe-P(两者之和约占10%),在短期内O-P和Ca_(10)-P相对较为稳定。随着培养时间延长,Ca_(2)-P逐渐向Ca_(8)-P转化,在培养的前30 d转化速率较快,之后速率减缓。随着磷肥施用量的增加,Ca_(2)-P转化为Ca_(8)-P所需的时间逐渐延长。Olsen-P和CaC_(l2)-P含量均与土壤无机磷组分中的Ca_(2)-P、Ca_(8)-P和Al-P含量呈显著正相关,通过逐步回归分析表明,其中Ca_(2)-P是土壤Olsen-P和CaC_(l2)-P的主要来源。

The objective of this study was to explore the transformation of water-soluble phosphate fertilizer in calcareous soil.A soil incubation experiment was conducted.Different amounts of superphosphate(P 0,6.25,12.5,25,50 and 100 mg/kg dry soil)were added to the soil(recorded as P0,P6.25,P12.5,P25,P50 and P100 treatments),and the soil humidity was maintained at 70%~80%of the field capacity.The soil was incubated in a constant temperature incubator at 25℃for 120 days.Continuous sampling was performed on days of 1,3,7,15,30,60 and 120 during the incubation period.The contents of Olsen-P,CaC_(l2)-P and inorganic phosphorus fractions in soil were determined.The results showed that the content of Olsen-P and CaC_(l2)-P in calcareous soil was significantly increased by applying superphosphate.Within a certain incubation time,the proportion of superphosphate transformed into Olsen-P and CaC_(l2)-P in soil did not change with the change of fertilization amount.The soil available phosphorus was decreased significantly in the first 7 days of incubation,and then decreased slowly.The superphosphate applied to the soil was mainly transformed into Ca_(2)-P and Ca_(8)-P(the sum of the two was about 90%),followed by Al-P and Fe-P(the sum of the two was about 10%).In the short term,the contents of O-P,Ca_(10)-P were relatively stable.With the extension of incubation time,Ca_(2)-P gradually transformed into Ca_(8)-P,and the transformation rate was fast in the first 30 days of incubation,and then slowed down.With the increase of phosphorus fertilizer application,the time required for Ca_(2)-P transform into Ca_(8)-P gradually prolonged.The contents of Olsen-P and CaC_(l2)-P were significantly positively correlated with the contents of Ca_(2)-P,Ca_(8)-P and Al-P in soil inorganic phosphorus fractions.The stepwise regression analysis showed that Ca_(2)-P was the main source of soil Olsen-P and CaC_(l2)-P.