Effects of Injection and Surface Applications of Liquid Swine Manure on Corn Yield and Soil Composition

A 3-year field experiment was conducted to study the agronomic effects of methods and rates of liquid swine manure application to Brookston-Crosby silt loam soil (fine, mixed mesic Aeric Ochraqualfs) cropped to corn (Zea mays L.). Swine manure (5.2–6.6% dry matter) from an anaerobic pit was applied to soil annually at 90, 135, and 180 t/ha by injection (30 cm below soil surface) and broadcast (surface) methods. These three rates provided averages of 428, 643, and 857 kg N/ha; 133, 200, and 266 kg P/ha; and 155, 232, and 310 kg K/ha per year; respectively. Check and inorganic fertilizer (168 kg N/ha, 56 kg P/ha, and 112 kg K/ha) treatments were also studied. The injection method of liquid manure application increased corn grain yield an average of 2,130 kg/ha each year, compared with the broadcast method at similar rates of application. Injection of swine manure was associated with higher corn-leaf N levels the first year; corn-leaf N, P, and K levels the second year; and corn-leaf N and K the third year of the study when compared with corn leaves from the broadcast method. Rate of manure application had little influence on corn-leaf analyses, and inconsistent effects on corn yield. Nutrient loadings of the soil from liquid manure applications were in excess of crop requirements, as evidenced by nutrient accumulations, particularly P and K, in the soil. Increases in soil nutrient levels at different depths in the profile reflected the initial placement of the manure by application methods (broadcast vs. injection). Volatile losses of NH₃-N from surface-applied liquid manure were reflected in lower corn yield response, lower corn-leaf N content, and lower soil NH₄⁺ and NO₃⁻ levels when comparing these parameters with the injection treatment. Application of liquid swine manure by injection at the 90 t/ha rate increased corn grain yield 14% above that from the inorganic fertilizer treatment.