Effects of 3-nitrooxypropanol manure fertilizer on soil health and hydraulic properties

Supplementing beef cattle with 3-nitrooxypropanol (3-NOP) decreases enteric methane production, but it is unknown if fertilizing soil with 3-NOP manure influences soil health. We measured soil health indicators 2 yr after manure application to a bromegrass (Bromus L.) and alfalfa (Medicago sativa L.) mixed crop. Treatments were: composted conventional manure (without supplements); stockpiled conventional manure; composted manure from cattle supplemented with 3-NOP; stockpiled 3-NOP manure; composted manure from cattle supplemented with 3-NOP and monensin (3-NOP+Mon), a supplement that improves digestion; stockpiled 3-NOP+Mon manure; inorganic fertilizer (150 kg N ha^-1 and 50 kg P ha^-1 ); and an unamended control. Select chemical (K⁺ , Mg²⁺ , Mn⁺ , Zn⁺ , pH, and Olsen-P), biological (soil organic matter, active C, respiration, and extractable protein), physical (wet aggregate stability, bulk density, total porosity, and macro-, meso-, and micro-porosity), and hydraulic (saturation, field capacity, wilting point, water holding capacity, and hydraulic conductivity) variables were measured. The inclusion of monensin decreased soil Zn⁺ concentrations by 70% in stockpiled 3-NOP+Mon compared with stockpiled conventional manure. Active C and protein in composted conventional manure were 37 and 92% higher compared with stockpiled manure, respectively, but did not vary between 3-NOP treatments. 3-Nitrooxypropanol did not significantly alter other soil health indicators. Our results suggest that composted and stockpiled 3-NOP manure can be used as a nutrient source for forage crops without requiring changes to current manure management because it has minimal influence on soil health.