As manure injection methods vary with modifications in application equipment, the availability of manure-N is probably altered. This study was conducted to quantify differences in the concentrations of inorganic (nitrate and ammonium) soil N and corn (Zea mays L.) yield as affected by vertical knife (VK) and horizontal sweep (HS) injection systems, and broadcast (BCST) applications. These manure application methods, plus a VK injection with nitrapyrin, were compared at a single manure rate at seven locations in Minnesota in 1992 and 1993. Soil inorganic N was measured at growth stages V1 and V4 and after grain harvest. Corn grain yield was also determined. At the V1 growth stage, inorganic-N from 0 to 2 ft depth averaged 24% higher in the manured treatments than in the nonmanured, unfertilized control. The average of the VK and HS treatments had 10% more inorganic-N than the BCST treatment and the HS resulted in 7% more inorganic-N than the VK. At the V4 growth state, similar results were measured—with the HS treatment having 8% more inorganic-N than the VK treatment. The impact of manure application methods on nitrate-N was greater than on ammonium-N for both in-season samplings. The use of HS resulted in significantly greater nitrate-N early in the growing season than did VK injection. Grain yields paralleled soil nitrate-N levels; average yields for the N responsive sites were 85, 107, 115, and 123 bu/acre for the control, BCST, VK, and HS treatments, respectively. While the use of nitrapyrin with VK injection delayed nitrification, the effect on yield was inconsistent. Research Question Manure application equipment manufacturers have developed numerous methods for applying liquid manure. As manure application methods vary, there may be differences in nutrient release, especially N. The primary objective of our research was to determine the effect of manure application method on inorganic N in the soil profile and on corn grain yield. Literature Summary While volatilization losses of N can be minimized by injecting manure, denitrification can be a significant N loss pathway for injected liquid manure. Research from Illinois, based on soil inorganic N measurements, has indicated that horizontal placement of manure beneath the soil surface could alleviate the potential for denitrification and possibly increase nitrification. Study Description Field studies were conducted at seven sites in south-central and west-central Minnesota in 1992 and 1993. Application methods for liquid dairy and swine manure included nonincorporated broadcast (BCST), vertical knife (VK) injection, VK injection with nitrapyrin, and horizontal sweep (HS) injection. Soil samples were collected twice early in the growing season and again after harvest to measure inorganic N, and corn grain yields were determined. Applied Question What effect does manure application method have on soil inorganic N quantity early in the growing season? Broadcast application of manure resulted in the lowest soil (nitrate + ammonium)-N concentrations at both in-season sampling times when compared with injected manure treatments (Fig. 1). Injecting manure, VK or HS, resulted in greater inorganic-N concentrations than broadcasting manure, with HS resulting in more inorganic-N in the soil than VK. The use of the nitrification inhibitor with VK delayed nitrification and had similar amounts of inorganic-N compared with HS at the V4 growth stage. Figure 1Open in figure viewerPowerPoint The effect of liquid manure application methods on corn grain yield and soil inorganic-N measured in the 0–2 ft depth at V1 and V4 growth stage. Were corn grain yields affected by manure application methods? Mean corn grain yield responses were similar to the inorganic-N concentrations measured in the soil due to manure application methods (Fig. 1). For the N responsive sites, the greatest yields (123 bu/acre) were measured with the HS treatment. This was significantly higher than the VK treatment (115 bu/acre). While there was considerable variation across location, there were no significant differences in grain yield due to adding nitrapyrin to the VK treatment. Whereas the BCST method yielded significantly more than the control, it was inferior to all injected application methods. Recommendations We recommend the use of HS injectors for liquid manure applications. This method of application provided the greatest amount of nitrate-N during the early growing season as well as the greatest yield. While the VK injection system with nitrapyrin also resulted in large quantities of nitrate-N during the growing season, the inconsistency in yields with VK methods limits its widespread endorsement.