Rising plate meters and a capacitance probe estimate the biomass of chicory and plantain monocultures with similar accuracy as for ryegrass-based pasture

Abstract

Abstract It is useful to gain an estimate of herbage biomass when feed budgeting. However, none of the tools that are available to estimate biomass (e.g., the rising plate meter (RPM) or capacitance probe (CP)) have been tested on popular forage herbs, such as chicory or plantain. We tested the hypothesis that RPM and CP could be used to estimate biomass of first year pure chicory and plantain swards with accuracy at least as great as for ryegrassbased pasture. In two summer experiments at different locations in the Waikato, RPM, CP and uncompressed sward height (SH) readings were taken throughout regrowth within 0.2 m² quadrats in chicory and plantain swards, and ryegrass-based pasture. The herbage was then cut to ground level and oven-dried to estimate biomass. Linear equations relating biomass to mean readings were generated for each method, both within each experiment and as pooled datasets. In ryegrassbased pasture, the correlation coefficients (R²) were 0.73, 0.43 and 0.51 for RPM, CP and SH, respectively. For chicory swards, the pooled correlation coefficients (R²) were 0.73, 0.73 and 0.81 for RPM, CP and SH, respectively, while for plantain swards the R2 were 0.70, 0.59 and 0.68 for RPM, CP and SH, respectively. This led to the conclusion that the RPM was a suitable tool for the estimation of biomass in pure chicory or plantain swards as it had similar accuracy to calibration equations for ryegrass-based pasture. Farmers, at least in the Waikato, can estimate first year chicory or plantain biomass through the summer and autumn period using the following equations: Chicory biomass (kg DM/ha) = 86 × RPM reading + 235, or = 0.64 × CP reading + 437, or = 94 × SH - 190. Plantain biomass (kg DM/ha) = 94 × RPM reading + 455. Keywords: rising plate meter (RPM), capacitance probe (CP), chicory, plantain