Comparison of Poultry Litter and Commercial Fertilizer Rate and Application Timing on Environmental Nitrogen Loss, Corn Grain Yield, and Mineral Composition

Abstract

For efficient use of poultry litter (PL) as a nutrient source, it is critical to balance the amount of nitrogen (N) needed to maximize corn (Zea Mays L.) grain yield while reducing N loss to the environment. Besides, there are limited reports on whether the application of PL enrich corn ear (including grain, cob and husk) with some of the mineral elements it supplies such as nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg). The mineral composition of corn ear greatly impacts its nutritional value and potential use as human food and animal feed. This 2-year study (2018–19) investigated the effects of N source [PL and conventional fertilizer (CF) such as urea], application rate [0 (control), 168 (low rate) and 336 (high rate) kg total N ha-1), and time (single and split application) on corn grain yield, environmental N loss (ENL), and ear mineral composition studied at three locations [E.V. Smith Research Center (EVS), Wiregrass Research and Extension Center (WREC), and Tennessee Valley Research and Extension Center (TVREC)]. In a single application, the target N rate was applied pre-plant whereas in a split application, one-fourth of the target N rate was applied pre-plant and the remaining three-fourth side dressed at the V6 growth stage. A field-scale partial N budget was used to quantify environmental N loss (ENL). Nitrogen inputs included N contribution from the fertilizer treatments, and the background N (soil N mineralization, crop seed, biological N fixation, and atmospheric N deposition) while N outputs included plant N uptake, residual soil inorganic N (NH4-N + NO3-N) and total N lost to the environment i.e. ENL. Plant and soil samples (0-15 and 15-30 cm depths) were collected at harvest each year for measuring aerial dry matter and residual inorganic N content, respectively. Ear samples were also harvested at physiological maturity each year and analyzed for the contents of 11 mineral elements (N, P, K, Ca, Mg, S, B, Zn, Mn, Fe, and Cu). Relative to CF, the application of PL increased grain yield at EVS whereas no significant difference in yield was found at the other two locations (WREC and TVREC). No response to application timing for grain yield was observed at WREC but the split application of PL reduced grain yield at other two locations (EVS and TVREC). Increased application of PL resulted in greater grain yield at WREC and TVREC compared to a low rate. Averaged across EVS and WREC, drier growing conditions of 2019 lowered grain yield by about 29% than in 2018. Aerial plant dry biomass followed similar patterns as grain yield at EVS and WREC whereas the highest whole plant N concentration was attained from urea application relative to PL, regardless of the study site, application rate, and timing. We found no consistent results for ENL among N sources with significantly greater ENL reported from PL at WREC but no differences at TVREC. At EVS, urea had greater ENL than PL at a single application whereas the opposite was true at a split application. Application timing did not influence ENL at WREC and TVREC. However, ENL increased with increasing N rate ranging from 32 to 52% of the total N input. Poultry litter, regardless of application rate, time, and location, did not increase the concentration of selected mineral elements in the ear. Corn fertilized with CF had the highest ear concentrations of N, P, K, Ca, Mg, Zn, Mn, Fe, and Cu at all locations which increased with increasing N rate. Ear N concentration was dependent on the level of its plant-availability in the soil. However, ear levels of P, K, and other mineral elements were not in proportion to their soil levels rather dependent on ear N concentration. These results indicated that optimal levels of plant-available N (PAN) in the soil, irrespective of whether derived from PL or CF, ensures maximum accumulation of ear N along with P, K, and other elements.