过磷酸钙用量对猪粪堆肥过程及磷形态变化的影响

摘要

[目的]过磷酸钙作为常用的畜禽粪便堆肥添加剂,具有减少氮素损失率并提高氮、磷养分含量等优点,但其对磷的有效性和形态的影响有待深入探讨.通过试验研究不同过磷酸钙添加量对猪粪锯末好氧堆肥过程的影响及堆肥中不同形态磷含量和形态之间的相互转化规律,以期为畜禽粪便堆肥中磷素的转化及合理施用提供科学依据. [方法]将猪粪和锯末以质量比(鲜重)4∶1的比例混合,然后按照猪粪和锯末干物质量的5％、10％、15％添加过磷酸钙,以不添加过磷酸钙作为对照(CK),进行42 d好氧堆肥,监测堆肥温度、含水率、pH、全氮、有机碳、全磷、有效磷、有机磷等指标. [结果]与CK相比,添加适量过磷酸钙可以显著提高堆肥的温度,增加高温持续期2～10d;提高堆肥物料的持水能力,加快有机碳降解.添加5％～15％的过磷酸钙可以显著降低堆肥初始pH值0.33～0.68个单位,有效抑制堆肥过程中铵态氮的挥发损失,CK、5％、10％和15％的处理在堆肥结束时的氮素损失率分别为29.4％、26.6％、18.5％和8.0％,全氮和全磷含量分别较堆肥初增加17.3～34.2％和37.0％～123.1％.CK有效磷含量随堆肥时间不断上升,第42 d较堆肥初增加73.0％,而添加过磷酸钙5％、10％和15％的处理有效磷含量显著降低,分别较堆肥初减少了4.0％、23.2％和41.8％.随着堆肥的进行,各处理中有效磷占全磷的比例均不断下降,表明堆肥过程降低了磷的有效性.堆肥前期以有机磷的矿化为主,后期以有机磷的合成为主,第42 d有机磷占全磷的比例CK最高(22.1％),添加5％、10％和15％过磷酸钙的处理分别为15.4％、11.0％和8.7％. [结论]猪粪堆肥中添加过磷酸钙,可以有效减少氮素损失,加快有机物料降解,以10％的添加量效果最佳;堆肥过程降低了磷的有效性,随着过磷酸钙用量的增加有效磷的比例不断下降;腐熟后堆肥中的磷以无机态为主,有机磷占全磷的比例随着过磷酸钙用量的增加而递减.%[Objectives] Calcium superphosphate is commonly used as an additive in animal manure composting,and can effectively reduce the nitrogen loss and increase the contents of nitrogen and phosphorus in the compost.However,its influence on availability and forms of phosphorus needs to be elucidated.[Methods] Swine manure (mixed with sawdust in 4 ∶ 1 ratio in fresh weight) was mixed with calcium superphosphate under 0,5％,10％ and 15％ (in dry weight) before being aerobically composted for 42 days.Temperature,water content,pH,organic carbon,C/N ratio,total nitrogen,total phosphorus,available P and organic P were measured during the composting.[Results] The addition of calcium superphosphate significantly increased the temperature and water-holding capacity of swine compost,and extended the thermophilic phase for 2-10 days.The addition amounts of 5％-15％ of calcium superphosphate significantly decreased the initial pH values of the compost by 0.33-0.68.The nitrogen losses after composting process,due to ammonium nitrogen volatilization,were 29.4％ (CK),26.6％ (5％ addition),18.5％ (10％ addition) and 8.0％ (15％ addition),respectively.The final total nitrogen and total phosphorus concentrations in all treatments increased by 17.3％-34.2％ and 37.0％-123.1％.Compared with the initial P content,the available P content in the treatment with no additive superphosphate was increased by 73.0％ after 42 days of the composting,while those in the treatments with 5％,10％ and 15％ superphosphate addition were decreased by 4.0％,23.2％ and 41.8％,respectively.During the process of composting,the ratios of available P over total phosphorous were continuously decreased in all treatments,demonstrating that the composting lowered the availability of phosphorous.The organic P was influenced by both the mineralization and phosphorus synthesis.In the final compost,the ratio of organic P to the total phosphorous was 22.1％ in the control,which was higher than the treatments with 5％,10％ and 15％ superphosphate addition,in which the ratios were 15.4％,11.0％ and 8.7％,respectively.[Conclusions] Calcium superphosphate addition in swine manure composting could effectively alleviate the nitrogen loss in the compost.The optimal addition of calcium superphosphate was 10％ in dry weight.The composting process decreased the availability of phosphorus in the compost,which was not conducive to the P absorption and utilization by crops.Inorganic phosphorus was the main form of phosphorous in the final compost,and adding superphosphate decreased the content of organic P in the final compost.