Applying coal char to cattle pens for sustainable agriculture in the semiarid US High Plains

Applying high carbon (C) additive to cattle pens and land application of the resultant manure mix offers a potential strategy for optimizing manure and soil management while mitigating environmental concerns. An experiment was conducted in western Nebraska from 2019 to 2022 to evaluate the effect of adding coal char (∼290 g C kg⁻¹ by wt.) on feedlot manure's properties and stability and the interacting effect of manure-char on crop yields in a corn (Zea mays L.)–dry bean (Phaseolus vulgaris L.)–corn rotation. Treatments in the crop field included manure from pens with or without char (each at 34 and 68 Mg ha⁻¹; low and high rate), urea at 100% recommended nitrogen (N) rate with or without 45 Mg char ha⁻¹, and a control. Applying char to pens kept them drier following snowfall events. The high surface area and cation exchange capacity of char improved soil and manure nutrient retention. The 100% urea-N plus char treatment had a greater corn yield than the low-rate char–manure mix or high-rate manure in 2020. In 2021, there was a trend for higher bean yields with the high char–manure rate treatment than the control. In 2022, all the fertilized treatments had greater grain yields than the control. A one-time high-rate char–manure mix or manure application could replace 314 kg N ha⁻¹ and 90 kg P₂O₅ ha⁻¹ over 2 years without any yield penalty. This study underscores the synergy between char and manure or chemical fertilizers to improve nutrient balance and supply, ultimately enhancing crop production.