Carbon concentration predicts soil contamination of plant residues

Abstract

Dry matter estimations of field-harvested plant materials can be complicated by varying degrees of soil contamination. A quick and simple method of screening materials for potential soil contamination would avoid unnecessary analyses. Harvested forage biomass and soil-surface crop residues were collected from cool-season perennial pastures, a silvopasture, and no-tillage cropland to determine ash concentration. Samples were also analyzed for total carbon (C) and nitrogen (N) concentrations as part of routine plant analysis. When assessing ash and C concentrations along a gradient of soil contamination among 260 samples, a common regression was developed that had <1% coefficient of variation [Ash (g kg−1) = 999 − 1.89 × C (g kg−1), r2=.99, p