An apparatus for Measuring Pasture Forage mass

J. L. Moyer, M. D. Schrock, D. W. Sweeney, R. R. Price, and K. W. Kelley

Southeast Agricultural Research Center and Biological & Agricultural Engineering, Kansas State University.

Abstract

Measuring pasture forage mass (FM) should be an integral part of grazing management.   However, measurement may not be performed properly if it is very time-consuming because of pasture variability that requires many observations for an accurate estimate.  This paper describes and evaluates an automated forage estimator “sled” that continuously records the height of a pivoting plate and the corresponding GPS readings as it is pulled over standing forage.  Plots of tall fescue (Festuca arundinacea) and bermudagrass [Cynodon dactylon (L.)Pers.] that were designed to study nitrogen responses were used to calibrate plate height of the forage estimator sled with FM.   The sled was pulled over the plots, and average plate height readings were regressed against FM flail-harvested from the plots.  Tall fescue FM ranged from 1000 to 6470 kg/ha (890 to 5770 lb/a) with a linear relationship between FM and plate height (r=0.95).  Bermudagrass FM ranged from 1270 to 11,310 kg/ha (1138 to 10,090 lb/a)with a quadratic relationship (r=0.87) between FM and plate height, apparently due to lodging at the higher nitrogen rates.  If plots with FM> 9,000 kg/ha were omitted, a linear relationship (r=0.96) was obtained.