畜禽饲料磷源和粪尿磷施用量对磷淋失的影响

Effects of feed phosphorus supplement and manure phosphorus application on phosphorus leaching

近年来集约化养殖业发展和畜禽粪尿的不合理还田导致大量畜禽粪尿磷流失到环境。针对该问题,我国完善了饲料磷推荐使用标准,提出了加强畜禽废弃物资源化等措施,这些措施显著降低了畜禽粪尿磷排泄量和磷环境排放。然而,将优化饲料磷与畜禽粪尿施用协同管理能否降低畜禽粪尿磷淋溶风险及损失尚不明确。基于此,本文以饲喂高水溶性饲料磷源(磷酸一二钙, MDCP)和常规饲料磷源(磷酸氢钙, DCP)的畜禽粪尿为供试肥料,设计淋溶模拟试验,分析“饲料-粪尿-农田”磷素协同管理对不同形态磷淋溶量的影响,以期为我国畜禽粪尿还田的深入推进提供理论支撑。结果表明,与DCP相比, MDCP可降低仔猪、肉鸡、肉鸭和蛋鸡畜禽粪尿淋溶液中溶解性无机磷和溶解性有机磷浓度,其降低范围分别为18.2%~31.0%和19.4%~55.9%。MDCP处理降低了畜禽粪尿活性磷以溶解性无机磷和溶解性有机磷形式的损失。施用来源于DCP饲料磷源的畜禽粪尿时,仔猪、肉鸡、肉鸭和蛋鸡粪尿输入的活性磷分别有19.7%、6.9%、16.7%和6.3%以溶解性无机磷形态淋溶损失;然而,施用来源于MDCP的畜禽粪尿,上述4种畜禽粪尿输入的活性磷分别有18.3%、6.4%、12.8%和4.7%以溶解性无机磷形态淋溶损失。因此,未来为了促进畜禽粪尿科学还田,降低畜禽粪尿磷淋溶风险,建议采取“饲料-粪尿-农田”磷素协同管理措施。

Phosphorus(P)is a key element in agricultural production.However,the rapid expansion of livestock production,coupled with inefficient manure recycling,has resulted in significant losses of manure P to water bodies.In addition to fueling the growth of toxic algae,this pattern has led to significant financial losses.China has updated the recommended standards for the use of feed P and introduced measures to increase livestock manure recycling.These strategies greatly reduced P excretion and loss to water bodies.However,the effect of integrating optimal feed P management with appropriate field manure application to reduce manure P leaching remains unclear.Water bodies contain various forms of P,such as dissolved inorganic P(DIP)and dissolved organic P(DOP).These P fractions were converted to themselves and were affected by the application rate of manure P.In general,livestock manure is ap-plied based on its nitrogen content or without regard to its nutrient content,a practice that increases the risk of manure P loss.There-fore,appropriate application of livestock manure is crucial for mitigating the risk of P leaching.To promote manure recycling in China,a leaching simulation experiment was conducted using a two-factor,completely randomized block design.The two factors were the rate of total manure P application and manure derived from livestock fed different P supplements.Two rates of total manure P application were 50 mg(P)·kg^(−1)[equivalent to the crop requirement at 80 kg(P)·hm^(−2)]and 165 mg(P)·kg^(−1)[equivalent to farmer practice at 260 kg(P)·hm^(−2) in North China Plain].The dietary P supplements used were dicalcium phosphate(DCP)and mono-dicalci-um phosphate(MDCP).DCP is the most widely used phosphate supplement,while MDCP is a new,highly water-soluble phosphate with 18.5 times greater water-soluble P content than DCP.Each treatment was replicated three times,with the control group receiv-ing no fertilization.We analyzed the effects of optimizing feed P supplements and manure application rates on leaching in terms of various P forms.Compared with DCP,MDCP reduced the leachate DIP and DOP contents of pig,broiler,duck,and layer manures,with decreases ranging from 18.2%-31.0%for DIP and 19.4%-55.9%for DOP.The loss of active P in the form of DIP and DOP was reduced by MDCP.For example,the cumulative amounts of DIP in the leachate were 53.1,7.4,18.0,and 12.9 mg in pig,broiler,duck,and layer,respectively.These values accounted for 19.7%,6.9%,16.7%,and 6.3%of the active P in the applied manure,re-spectively.However,the manure derived from MDCP,the cumulative amounts of DIP leaching were 39.9,5.6,12.4,and 8.3 mg for pig,broiler,duck,and layer,respectively.These accounted for 18.3%,6.4%,12.8%,and 4.7%of the P in the applied manure,respect-ively.To reduce the risk of P leaching in the field,application of animal manure derived from highly water-soluble feed P supple-ments and optimizing the total P application rate is recommended.Additionally,factors,such as crop type,soil type,rainfall,and ma-nure composition,along with the principles of the 4R(right source,right rate,right time,and right place)should be considered to en-sure sustainable P management.