On‐Farm Evaluation of Poultry Manure as a Nitrogen Source for Corn

Poultry manure in Iowa is primarily used for row crop production. However, producers question the proportion of total manure N that is available for plant uptake under local conditions and using local manure types. The objectives of this study were to estimate the first-year supply of plant-available N to corn (Zea mays L.) from three poultry manure types under producer crop management conditions across environments in Iowa, and to evaluate alternative soil and plant parameters as tools to assess N availability of poultry manure. Manure was applied at two rates, a low and high rate based on total N analysis of the manure (intending to supply approximately 84 and 168 kg total N), in addition to a no-manure control. The study was conducted at 18 locations from 2004 to 2006. Fertilizer equivalency determined from four rates of fertilizer N was used to estimate first-year poultry manure N availability. Across all manure types and sites, and using grain yield (GY) response, statistical confidence intervals indicated 38 to 55% of the total N applied with poultry manure was available to corn, with a mean 46% plant-available N. Analysis of postmaturity lower corn stalk NO 3 - -N concentrations indicated 41 % N availability, while leaf chlorophyll meter (CM) readings may be unreliable for estimating plant N availability as results indicated only 34% N availability. Soil NO 3 - -N concentrations in early June appeared to vary with added NH 4 + -N from the manure. This on-farm field study provided estimates of poultry manure plant-available N to corn with producer management systems and would include any volatile N losses during or after land-spreading.