Particle Size Affects Nitrogen and Carbon Estimate of a Wheat Cover Crop

Accurate analysis of cover crop tissue for carbon (C) and nitrogen (N) analysis is needed to determine the C/N ratio, and for accurate estimation of N uptake. A critical component for accurate estimates is the sample‐grinding size. The objective of this study was to evaluate the impact of the cover crop grinding size on C, N, and C/N analysis. Wheat ( Triticum aestivum L.) aboveground biomass was sampled and ground to three different particle sizes (1 and 0.6 mm and pulverized). Each sample size treatment was replicated 33 times. Cover crops were evaluated for variation in concentration of C, N, and C/N ratio based on sample‐grinding size. Statistical analysis revealed that there were no differences between C and N concentration of 0.6 and 1 mm particles, which were always higher than that of pulverized samples. When absolute values are needed for developing prediction models, pulverizing samples for C, N and C/N ratio provides more accurate values with high precision. Sample sizes below 1 mm should be converted into pulverized sizes to standardize data for modeling and meta‐analysis purposes. Core Ideas Sample‐grinding size affected wheat nitrogen and carbon estimates. Carbon and nitrogen concentrations of 0.6 and 1 mm particles were similar. Pulverizing the samples increased the precision of the carbon and nitrogen concentrations. Data should be standardized for modeling and meta‐analysis purposes.