Response of soil health indicators to long-term dairy manure in a semiarid irrigated cropping system

Authors: Dungan, Robert - Rob; McKinney, Chad; Acosta-Martinez, Veronica; Leytem, April

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2022
Publication Date: 11/22/2022
Citation: Dungan, R.S., Mckinney, C.W., Acosta Martinez, V., Leytem, A.B. 2022. Response of soil health indicators to long-term dairy manure in a semiarid irrigated cropping system. Soil Science Society of America Journal. 86:1567-1610. https://doi.org/10.1002/saj2.20462.
DOI: https://doi.org/10.1002/saj2.20462

Interpretive Summary: The objective of this field study was to determine the response of commonly used soil health indicators to long-term dairy manure use in a tilled and irrigated cropping system in southern Idaho. The treatments were no fertilizer, inorganic fertilizer, and dairy manure applied annually or biennially. Soils were collected after seven years of manure application, then analyzed for twelve different soil health metrics. In general, the soil health metric values decreased with soil depth. The manure treatments had a significant effect on the indicators, which increased linearly with increasing manure application rate. Due to the strong influence of dairy manure on the indicators, all were significantly correlated with each other. Our results suggest that treatment of soil with dairy manure can improve soil health, but these results should be interpreted cautiously, as application of manure at high rates over long periods of time can have negative impacts on soil, crop, and environmental quality.

Technical Abstract: Dairy manure use in southern Idaho is an important practice to return nutrients to cropland soils, but there is little information regarding the effect of manure application rates on soil health metrics. The objective of this field study was to establish a soil health framework for soils treated with manure by evaluating commonly used biological and chemical indicators of soil health as affected by long-term dairy manure use in a tilled and irrigated cropping system. The treatments were no fertilizer, inorganic fertilizer, and dairy manure applied annually or biennially at rates of 17, 35, and 52 Mg ha-1 on a dry weight basis. A one-time spring soil sampling was performed seven years after project initiation at depths of 0-15 cm and 15-30 cm. The soils were analyzed for the following twelve soil health metrics: soil organic C (SOC), permanganate-oxidizable C (POXC), microbial biomass C (MBC), microbial biomass N (MBN), autoclaved citrate-extractable (ACE) soil protein, ß-glucosidase, ß-glucosaminidase, alkaline phosphatase, arylsulfatase, potentially mineralizable nitrogen (PMN), potential ammonia oxidation (PAO), and denitrification enzyme activity (DEA). In general, the soil metrics were greater at 0-15 cm than deeper in the soil profile. Annual and biennial manure treatments had a significant effect on the indicators at both soil depths, which increased linearly with increasing manure application rate. Due to the strong influence of dairy manure on the biological and chemical indicators, all were positively and significantly correlated with each other. Our results suggest that treatment of soil with dairy manure can be used to improve soil health as determined by the indicators. However, results should be interpreted cautiously, and our studies will continue to make adjustments as application of manure at high rates over long periods of time can have negative impacts on soil, crop, and environmental quality.