Impact of dairy wastewater irrigation and manure application on soil structural and water-holding properties

The livestock sector contributes about 40% of global agricultural output and uses over 30% of total feed-crop land. The sector's continuing growth has led to increased technology and larger-scale, commercialized agriculture, and it correlates to growth in by-products and waste, which can compromise the environment and human health. Although organic manure is an excellent soil fertilizer whose nutrient content increases crop yield, untreated and/or overapplied manure pollutes local water resources and can alter soil aggregate structure, potentially affecting soil health and available water. Proper livestock waste management is essential for sustainable food production. Waste reuse strategies exist, with goals such as minimizing freshwater consumption, improving food production, and contributing to energy production, However, each strategy has tradeoffs in environmental, energy, or monetary costs. This study provides a quantitative approach to evaluating waste impact on soil health and helps to better manage irrigation practices and water supply gaps in arid and semi-arid areas by better understanding how management practices affect physical soil health. The TypoSoil apparatus was used to measure and analyze the hydrostructural parameters (water-holding capacity and soil structure) of fine sandy loam (A horizon) and sandy clay (B horizon). Soils from the Texas A&M AgriLife Research Dairy (Stephenville, Texas) were collected and compared with control (untouched) soils. Waste (manure, bedding materials, wash water) was separated into liquid (passed through a natural lagoon treatment process) and solid components (applied as fertilizer). Approximately half the wastewater was reused as wash water, the remainder for irrigation. Although the soil varied substantially between sample locations, a statistically significant difference existed between the control and manure/wastewater applications in both the A and B horizons. Both applications improved plant-available water (AW) in the A horizon (40% and 30%, respectively) but deteriorated AW in the B horizon (25% and 30%). Thus, dairy farm waste is a viable source for agricultural use. © 2021 American Society of Agricultural and Biological Engineers