Between 62% and 92% of industrial and municipal wastewater in upper-middle, low-middle, and low income countries is discharged to the environment untreated, releasing valuable nutrients such as nitrogen (N) and phosphorus (P) into rivers, lakes, and oceans (Lipponen and Nikiforova, 2017). This, in addition to excess nutrients often present in agricultural runoff due to overuse and misuse of fertilizers, can lead to eutrophication, often causing irreparable damage to aquatic ecosystems. For these reasons, new techniques must be found to effectively recover waste nutrients and upcycle them into natural soil amendments that can be used to enrich soil quality and grow food for future generations while minimizing agricultural runoff. Duckweed is a small floating aquatic plant that can hyperaccumulate nutrients present in wastewater and agricultural runoff and then be harvested and reused to replace or supplement commercial soil fertilizers. As part of a two-year field trial, duckweed was tested for the second consecutive year in this study as a soil amendment in comparison to, and in combination with, commercial fertilizer for the growth of sorghum, a drought-resistant grain. Relative to fertilizer in all cases, soils amended with duckweed generated less ammonia and nitrate in surficial runoff. No differences in P in cumulative runoff were found among the different treatments (p = 0.509). Additionally, duckweed application produced sorghum grains with greater N and P content than other treatments (1.63 ± 0.03% N (p = 0.001) and 0.35 ± 0.0% P (p = 0.016)). Duckweed treatments also showed increased soil residue carbon and P after harvesting the crop. When normalized by germination rate, sorghum yield was similar across treatments. In agreement with first-year findings, the results indicated that duckweed may be a viable alternative to commercial fertilizer from an environmental and agricultural perspective, providing acceptable yields and contributing to the buildup of beneficial nutrients in the soil profile. Additional testing is needed to further evaluate potential germination inhibitors, greenhouse gas emissions (ex., N₂O), and efficacy when applied to different crops and soil types.

中上，低中和低收入国家的工业和市政废水中有62％至92％未经处理就排放到环境中，从而将宝贵的养分，例如氮（N）和磷（P）释放到河流，湖泊，和海洋（Lipponen和Nikiforova，2017年）。这不仅是由于过度使用和滥用化肥而经常在农业径流中出现的过量养分，还可能导致富营养化，并经常对水生生态系统造成不可弥补的损害。由于这些原因，必须找到新技术来有效回收废物养分并将其循环利用到天然土壤改良剂中，这些改良剂可用于丰富土壤质量并为后代种植粮食，同时最大程度地减少农业径流。浮萍是一种小型浮游水生植物，可以超量吸收废水和农业径流中存在的养分，然后将其收获并再利用以替代或补充商业土壤肥料。作为一项为期两年的田间试验的一部分，浮萍已连续第二年进行了土壤改良剂测试，与高粱（一种抗旱谷物）的商业肥料进行了比较，并与之配合使用。在所有情况下，相对于肥料，浮萍改良的土壤在地表径流中产生的氨和硝酸盐较少。在不同处理之间，累积径流中的磷没有差异（在这项研究中，浮萍连续第二年作为土壤改良剂进行了测试，与抗旱谷物高粱的商业化肥料相比，并与之结合使用。在所有情况下，相对于肥料，浮萍改良的土壤在地表径流中产生的氨和硝酸盐减少。在不同处理之间，累积径流中的磷没有差异（在这项研究中，浮萍连续第二年作为土壤改良剂进行了测试，与抗旱谷物高粱的商业化肥料相比，并与之结合使用。在所有情况下，相对于肥料，浮萍改良的土壤在地表径流中产生的氨和硝酸盐较少。在不同处理之间，累积径流中的磷没有差异（p  = 0.509）。此外，浮萍施用产生的高粱籽粒的氮和磷含量高于其他处理（1.63±0.03％的氮（p  = 0.001）和0.35±0.0％的磷（p  = 0.016））。浮萍处理还显示，收获农作物后土壤残留碳和磷增加。当通过发芽率归一化时，各处理间的高粱产量相似。与第一年的发现一致，结果表明从环境和农业的角度来看，浮萍可能是商业肥料的可行替代品，提供可接受的产量并有助于土壤剖面中有益养分的积累。需要进一步测试以进一步评估潜在的发芽抑制剂，温室气体排放量（例如，N ₂O），以及应用于不同作物和土壤类型的功效。