Nitrous Oxide Emissions from Soil Amended with Low-Phosphorus Broiler Litter.

Regions of the United States with a high concentration of poultry farms have soils with excess nitrogen (N) and phosphorus (P) far beyond the agronomic requirement of crops because of recurrent land application of broiler litter. A new waste treatment technology developed by USDA-ARS, called “Quick Wash”, can recover phosphates from broiler litter while better balancing the N:P ratio of the treated litter for crop needs. While some studies have shown the addition of broiler litter to soil may increase nitrous oxide (N₂O) emissions, limited information is available on the effect of low-P broiler litter after the “Quick Wash” treatment. Our objective was to carry out a laboratory test to evaluate N₂O emissions from a Norfolk loamy sand amended with low-P broiler litter in loose or pellet forms as compared to N₂O emissions from broiler litter without the "Quick Wash" treatment. Undisturbed soil cores (15 cm x 5 cm diam.) received the following amendments:  un-amended soil (control), raw litter, pelletized raw litter, low-P litter, and pelletized low-P litter.  All cores were adjusted to 60 % water-filled porosity, enclosed in plastic jars, and incubated at 25°C for 68 d, with periodic N₂O emission measurements. The highest maximum N₂O flux peak was observed at incubation day 16 with the pelletized raw litter (348 ng N/cm²/h). Whereas much lower maximum flux peaks for the low-P litter (121 ng N/cm²/h) and the low-P pelletized litter (37 ng N/cm²/h) were both observed at incubation day 7. Accordingly, raw, raw pelletized, low-P, low-P pelletized litter, and un-amended soil had cumulative N₂O productions of 1261, 894, 407, 287, and 80 µg N₂O-N/kg soil, respectively. Further detailed discussion of the impact of these amendments on soil N₂O emissions will be included in our presentation.