Assessing biological soil health through decomposition of inexpensive household items

Recognition that soil resources are fragile has increased interest in soil health promoting practices (SHPPs) and ways to monitor changes in agricultural soil health. To enhance this effort, inexpensive and user-friendly methods are needed. Especially methods to measure biological activity, which is central to soil health but current methods are expensive and inconvenient. Our objective was to quantify biological activity by monitoring decomposition (via mass loss) of common household items [green and rooibos tea (Camellia sinensis and Aspalathus linearis), bleached cotton (Gossypium hirsutum), and birch craft sticks (Betula spp.)], and compare these results with common laboratory measurements of biological soil health (microbial biomass carbon and nitrogen, permanganate oxidizable carbon, and potentially mineralizable carbon and nitrogen). First, we compared both strategies using correlation, including with the yield of the dominant crop in the region [maize (Zea mays L.)]. Second, we evaluated their response to several long-term SHPPs: (i) biochar, (ii) winter cover crops, (iii) nitrogen fertilizer, (iv) no-tillage, (v) diversified rotation, (vi) perennial crops, (vii) crop residue addition/removal, and (viii) prairie restoration. Correlations between decomposition and laboratory measurements were poor and often negative. Maize yield positively correlated with tea decomposition but not with the laboratory indicators. Based on ‘signal-to-noise’ ratios, or magnitude of SHPP treatment effect compared to variability, measurements of decomposition, especially mass loss of rooibos tea (for 4 days) and bleached cotton (for 35 days), outperformed many of the laboratory indicators in detecting treatment differences. Decomposition was also easier and less expensive than laboratory methods indicating it is a simple, yet scientifically defensible, alternative for measuring soil biological health in agroecosystems.