Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2020
Publication Date: 11/6/2020
Citation: Szogi, A.A., Takata, V.H., Shumaker, P.D. 2020. Chemical extraction of phosphorus from dairy manure and utilization of recovered manure solids. Agronomy [MDPI]. 10(11). https://doi.org/10.3390/agronomy10111725.
Interpretive Summary: When adequately applied to farm fields, dairy manure is a valuable source of nutrients essential for crop plant growth, such as nitrogen (N) and phosphorus (P). However, repeated land application of dairy manure can increase the amount of soil phosphorus above crop requirements because of the imbalance of N and P content (N:P ratio) in manure and harvested crops. The N:P ratio in plant biomass of most grain and hay crops is 8:1 against manures that usually have a smaller N:P ratio of less than 4:1. The soil P build-up can lead to soil P losses and contamination of lakes and rivers. This study evaluated a method to extract P from manure slurry, called Quick Wash, combined with a solid-liquid separation system to recover manure solids. The Quick Wash process uses a novel combination of acid, base, and organic reagents to extract P from manure solids while improving the N and P balance of recovered manure solids (RMS). Results showed that coarse RMS could have use as bedding for dairy cows. Incorporation of low-P RMS into soil provided higher N levels for plant growth than untreated dairy slurry. Our results suggest that including the Quick Wash in a dairy manure management system can lower costs of bedding material and manure hauling, recover P for use as fertilizer, and reduce the environmental impact of land spreading manure P.
Technical Abstract: Repeated land application of dairy manure can increase soil P above crop requirements because of manure's low N:P ratio (< 4:1). This soil P build-up can lead to off-site P transport and impairment of surface water quality. We evaluated a treatment process to extract P from manures, called Quick Wash, integrated with a double-stage solids separation system to recover coarse and fine manure solids. The Quick Wash process uses a combination of acid, base, and organic polymers to extract and recover P from manures, improving the N:P ratio of recovered manure solids (RMS). Results showed that coarse RMS could have use as bedding materials for dairy cows, and the fine acidified RMS with N:P > 10:1 can be used as a low-P organic soil amendment. A soil incubation test showed that acidified RMS stimulated N mineralization and nitrification having higher nitrate levels than untreated dairy slurry when incorporated into soil. Our results suggest that the inclusion of Quick Wash in a dairy manure management system can improve manure's value, lowering costs of bedding material and manure hauling, and recover P for use as fertilizer while reducing the environmental impact of land spreading manure P.