Ippolito J A, Barbarick K A, Norvell K L
Dep. of Soil and Crop Sciences, Colorado State Univ., Fort Collins, CO 80523-1170, USA.
J Environ Qual. 2007 Apr 5;36(3):764-72. doi: 10.2134/jeq2006.0308. Print 2007 May-Jun.
Biosolids land application rates are typically based on crop N requirements but can lead to soil P accumulation. The Littleton/Englewood, Colorado, wastewater treatment facility has supported biosolids beneficial-use on a dryland wheat-fallow agroecosystem site since 1982, with observable soil P concentration increases as biyearly repeated biosolids applications increased from 0, 6.7, 13, 27, to 40 Mg ha(-1). The final study year was 2003, after which P accountability, fractionation, and potential environmental risk were assessed. Between 93 and 128% of biosolids-P added was accounted for when considering conventional tillage soil displacement, grain removal, and soil adsorption. The Fe-P fraction dominated all soil surface P fractions, likely due to an increase in amorphous Fe-oxide because Fe2(SO4)3 was added at the wastewater treatment facility inflow for digester H2S reduction. The Ca-P phase dominated all soil subsurface P fractions due to calcareous soil conditions. A combination of conventional tillage, drought from 1999 to 2003, and repeated and increasing biosolids application rates may have forced soil surface microorganism dormancy, reduction, or mortality; thus, biomass P reduction was evident. Subsurface biomass P was greater than surface biomass, possibly due to protection against environmental and anthropogenic variables or to increased dissolved organic carbon inputs. Even given years of biosolids application, the soil surface had the ability to sorb additional P as determined by shaking the soil in an excessive P solution. Biosolids-application regulations based on the Colorado Phosphorus Index would not impede current site practices. Proper monitoring, management, and addition of other best management practices are needed for continued assurance that P movement off-site does not become a major issue.
生物固体废弃物的土地施用量通常基于作物对氮的需求，但可能导致土壤磷的积累。自1982年以来，科罗拉多州利特尔顿/恩格尔伍德的废水处理设施一直支持在旱地小麦-休耕农业生态系统场地进行生物固体废弃物的有益利用，随着每两年重复施用生物固体废弃物的量从0、6.7、13、27增加到40 Mg ha(-1)，土壤磷浓度明显升高。研究的最后一年是2003年，之后对磷的去向、分级以及潜在环境风险进行了评估。在考虑传统耕作导致的土壤位移、谷物收获以及土壤吸附的情况下，添加的生物固体废弃物中93%至128%的磷得以解释。铁磷组分在所有土壤表层磷组分中占主导地位，这可能是由于在废水处理设施进水口添加硫酸铁以减少消化器中的硫化氢，导致无定形氧化铁增加。由于土壤呈钙质条件，钙磷相在所有土壤亚表层磷组分中占主导地位。传统耕作、1999年至2003年的干旱以及生物固体废弃物施用量的不断增加，可能导致土壤表层微生物休眠、数量减少或死亡；因此，生物量磷减少明显。亚表层生物量磷大于表层生物量，这可能是由于受到环境和人为变量的保护，或者是由于溶解有机碳输入增加。即使经过多年的生物固体废弃物施用，通过在过量磷溶液中振荡土壤测定，土壤表层仍有吸附额外磷的能力。基于科罗拉多磷指数的生物固体废弃物施用规定不会阻碍当前场地的做法。需要进行适当的监测、管理并添加其他最佳管理措施，以持续确保磷向场地外的迁移不会成为一个主要问题。
