Visual estimates of available herbage on hill country sheep pastures

Abstract

Available standing herbage over a range of sheep-grazed hill pastures was visually estimated by the same observer at regular intervals throughout the year. The results were compared with dry matter (DM) yield cuts from nine quadrats sited within each paddock. Linear regressions of yield on visual estimates were significant at all times (r 2 = 0.6-0.9). The analyses showed that the same observer can consistently assess paddock differences throughout the year and between years without using yield cut calibrations. However, the conversion of visual estimates to DM yield values was only possible on occasions in spring and early summer when pastures were green and residual coefficients of variability (RCV) were low. At other times of the year, when RCV values were high, the observer tended to under-estimate total DM over whole paddocks by over-estimating the green fraction and under-estimating the dead material and had difficulty in maintaining consistency with between-paddock assessments of paddocks of widely differing sward densities. Scoring a number of small plots within each paddock is preferable to whole-paddock estimation methods.

Long term effects of withholding phosphate application on North Island hill country: Te Kuiti

“…Measurements included monthly ewe and lamb liveweights (lamb liveweights from birth to weaning), wool weights at shearing in May and November (November only in 1983), wool quality measurements, weekly pasture cover assessments on all paddocks (Baars & Dyson 1981), pasture production measurements over set stocking and from an associated small-plot trial (using a cage cut method) and annual pasture composition measurements on 5 fixed transect lines in each paddock. Soil tests were done annually and fertiliser quality monitored before application.…”

“…Results follow a similar pattern to those for animal production, namely, little effect in the first year of withholding fertiliser, a marked reduction in year 2 and a levelling out thereafter at approximately 20% less production. Another approach to assessing pasture production was to visually assess pasture cover weekly on the three farmlets and by using previous calibration information (Baars & Dyson 1981) convert this to total dry matter (Table 5). The marked decline in the average feed available on the nil P farmlet is apparent.…”

Methods for Estimating Pasture Dry Matter on Dairy Farms in Northland

“…To date, farmers and advisers have been expected to recognise pasture DM, either from occasional calibration or from verification based on animal responses to preselected DM feeding levels. Scientific objections to such methods relate to the human variation in day-to-day visual estimation and to the need for numerous, careful, and independent assessments within a paddock to provide an accurate paddock estimate (Parker 1973, Baars and Dyson 1981, Stockdale 1984, Piggot and Morgan 1985. The inevitable conclusion is that the correct application of visual estimation methods (i.e.…”