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Impact of Dairy Wastewater Irrigation and Manure Application on Soil Water Holding Capacity as a Water-Soil-Waste Nexus Study
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The livestock sector contributes to about 40 percent of the global value of agriculture output and takes over a third of total crop land for use as feed crop. The industry continues to grow in demand leading to an increase in technology and more large-scale, commercialized agriculture. However, large growth in operations correlates to large growth in by products and waste, which can compromise environment and human health. Organic manure can act as a wonderful soil fertilizer for increasing crop yield due to its nutrient content; however, if left untreated or over applied nutrients can pollute local water resources. The application of waste on land has been shown to alter soil structure, potentially changing the amount of water available in the soil for plants to grow. Thus, proper waste management from livestock production is an important part of maintaining sustainable food production. There are a handful of different waste reuse strategies with various goals such as minimizing the consumption of fresh water, improving food production, or contributing to energy production. However, each management technique comes with tradeoffs and associated environmental, energy, or monetary costs. At the Texas A&M AgriLife Research Dairy in Stephenville, Texas, waste composed of manure, bedding materials, and wash water is separated between liquid and solid components. Currently, a portion of the solids are applied to the land as fertilizer while the liquid waste goes through a natural lagoon treatment process. Approximately half of the wastewater is reused as wash water and the other half is for irrigation. To better understand how these management practices effect the physical soil health and thus food production, parameters indicative of water holding capacity and soil structure will be analyzed. Using the TypoSoil™ machine to collect measurements, the hydro-structural parameters of a fine sandy loam (A horizon) and a sandy clay (B horizon) soil were evaluated under current conditions of the dairy and compared to untouched soil. Although the soil itself was highly variable among the sample locations, a statistically significant difference between available water and Kbs was detected between the control and the manure and wastewater application in both A and B horizons. Interestingly, both manure and wastewater application improved plant available water in the A horizon by 30 and 40 percent respectively, but deteriorated plant available water in the B horizon by 30 and 25 percent.
Pinkerton, Taylor Cullen (2018). Impact of Dairy Wastewater Irrigation and Manure Application on Soil Water Holding Capacity as a Water-Soil-Waste Nexus Study. Master's thesis, Texas A & M University. Available electronically from