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Predicting forage mass with nondestructive tools


Subjective visual estimations of forage mass are inaccurate and often lead to poor stocking decisions. Most literature on estimating forage mass with nondestructive sampling procedures involves plant species that are similar in structure (i.e. height) and have nearly complete ground cover. Accurate pasture mass measurement tools are needed for morphologically heterogeneous pastures managed under limited irrigation in a semi-arid environment.

In an article recently published in Agronomy Journal, five nondestructive sampling techniques were compared for predicting forage mass in alfalfa-tall wheatgrass pasture in the water-limited Southern High Plains. Procedures included pasture ruler, rising plate meter, ImageJ, PowerPoint® photo-point count, and normalized difference vegetation index (NDVI). Calibration models were developed and applied to external data to determine the predictive ability of each procedure.

The PowerPoint model was the most precise option if restricted to a single sampling procedure, whereas the combined (ImageJ + height) model possessed the superior combination of high R2 and low model error. The combined model would be most applicable since it did not saturate when measured forage mass exceeded 1200 kg DM ha-1. The continued use of ImageJ with canopy height measurements for forage mass prediction is attractive since they require simple equipment, are adaptable, and can be automated.

Read the full article in Agronomy JournalFree preview Sept 13 - Sept 20