Effects of dairy manure and inorganic fertilizer on runoff water quality on common bermudagrass

Abstract

Dairy manure is produced in large quantities in concentrated areas of the United States. This nutrient source has been used in the crop industry for many years and could be a potential organic alternative for turfgrass production. Concerns over nutrient losses in surface water runoff and accumulation in surface soils have raised questions about application rates and the potential P and NO₃⁻ contamination in ground and surface water. Composted dairy manure was applied at none (0 kg P ha⁻¹y⁻¹), low and high rates of 100 and 200 kg P ha⁻¹ y⁻¹. Inorganic ferilizer applied as a 0-46-0 was applied at a high rate of 100 kg P ha⁻¹ y⁻¹, low rate of 50 kg P ha⁻¹ y⁻¹, and a control rate of 0 kg P ha⁻¹ y⁻¹. Turfgrass performance ratings of inorganic fertilizer treatments exceeded composted dairy manure performance ratings for color, quality, and density. Inorganic fertilizer treatments elevated tissue N concentrations above composted dairy manure treatment concentrations. Phosphorous tissue concentrations were not affected by either nutrient source or application rate. Dry matter production was greater for inorganic fertilizer treatments. Soil nitrate levels decreased across all treatments. Initial soil samples contained P concentrations of 40 to 50 mg P kg⁻¹ across all treatments. At the end of the study, P concentrations had increased to 162 mg P kg⁻¹ for the high inorganic fertilizer application and 154 mg P kg⁻¹ for the high composted dairy manure treatment. Dissolved phosphorous (DP) concentration losses in runoff, in the short-term, were greatest from inorganic fertilizer applied at the high rate. Long term DP losses were greatest from composted dairy manure treatments. Dissolved nitrate (DN) losses were greatest in the short-term from composted dairy manure applied at the high rate. Whereas, long term DN losses were greatest from inorganic fertilizer treatments applied at the high rate. Sediment P and TKN losses in runoff decreased over time and were not affected by either nutrient source or application rate. Runoff monitoring of nutrient losses provided information to suggest composted dairy manure and inorganic fertilizer should not be applied if runoff producing rainfall is expected.