Sidedressing corn with liquid manure is a better application timing to utilize manure nitrogen efficiently. A percentage of fall-applied nitrogen is converted to nitrate-N. The amount converted depends upon soil temperatures and days to incorporation after land application. This nitrate is environmentally lost through leaching or denitrification before corn planting and nutrient uptake. While the total corn nitrogen application rate is reduced by an N credit or measure of soil nitrate through a pre-sidedress nitrogen test, commercial fertilizer will often be applied at corn sidedress time. The combined fall manure and fertilizer N applied results in increased total nitrogen, increasing environmental N loss potential. In-crop manure application has the advantage that any ammonium N applied can offset the total N requirement of the corn crop.
The experimental objectives were to determine the economic, agronomic, and environmental outcomes of in-crop manure application versus a traditional fall manure application.
What Did We Do?
A trial comparing fall to in-crop liquid manure application to corn was established in the fall of 2019 at a USDA-ARS paired Edge-of-Field monitoring site in the Western Lake Erie Watershed. The trial used a before/after impact experimental design. Field one had fall-applied manure, then used UAN at corn sidedress time. The second field had only swine manure applied at corn sidedress timing. Data collected included corn yield, soil test, tissue test, imagery, and nutrient loss through tile and surface runoff. Aerial imagery utilized Normalized Differential Red Edge (NDRE) imagery measure on a 0-1 scale to quantify plant heath.
What Have We Learned?
The total applied nitrogen with fall manure/UAN application was 516 pounds per acre compared to 341 pounds per acre for in-crop manure application. Corn yield was improved by 17 bushels per acre with the in-crop manure application despite a dryer than normal production year where the treatment total yield was 136 bushels per acre. Tissue tests taken at R1 were similar between the two treatments with %N and %P lower than desired ranges. In-crop manure application resulted in a 0.63 NDRE index compared to a 0.60 NDRE index for fall manure/UAN application, indicating better plant health. The in-crop manure application had higher equipment and labor costs that were offset by reduced nutrient cost, plus higher yields improving net return by $95 per acre.
The applied nitrogen not recovered in the grain was 437 and 250 pounds per acre for the fall manure/UAN and in-crop manure application, respectively. Soil samples using a 0-12 core depth were taken after application (June), after harvest (November), and spring of the following year (March and May). Nitrate and phosphorous levels were higher for the in-crop application for all sampling periods prior to the May sampling. By May soil test levels were equal for both nutrients. Both nitrate and phosphorous levels in the 0-12 zone were within expected ranges. The estimated in-crop manure application effects had mixed results for tile and surface water quality outcomes measured in pounds per acre. For tile water DRP (-5%), Nitrates (-35%) were reduced while Total P (7%) increased. The surface water had lower nitrate (73%) but higher DRP (148%) and Total P (43%). Tile water is a greater pathway for offsite water movement.
Wheat was planted after soybean in fall 2021. The anticipated comparison is in-crop manure application compared to fall-applied manure/topdress fertilizer to supply needed N. A second corn in-crop to fall-applied manure/commercial fertilizer comparison is planned for the 2023 crop year. These projects are cooperation with USDA-ARS Soil Drainage Unit and Blanchard Valley Demo Farms.
An Ohio State University Extension initiative is looking at fall applied versus in-crop manure application at 10 paired field sites in 2022 and 2023. A second set of field trials are N rate trials 0-250 pounds of N in manured fields with 5 sites in 2022 and 2023.
Greg LaBarge, Field Specialist, Agronomic Systems, Professor, Ohio State University Extension
Corresponding author email address
Kevin King, Research Leader and Agricultural Engineer, USDA-ARS Soil Drainage Unit, and Jed Stinner, Hydrologic Technician, USDA-ARS Soil Drainage Unit
Blanchard Valley Demonstration Farms