Evaluation of the wheel‐point and step‐point methods of veld condition assessment

Abstract

A number of aspects of a technique recently developed to assess the agro‐ecological condition of veld were evaluated by 4 independent observers. Measuring the veld composition score yielded relatively repeatable results with a’ 95% confidence limit of ±6,43 units for any single estimate which may range from 0 to 100 units. The step‐point method yielded results on percentage veld composition and on veld composition score which did not differ in precision or in absolute amount from those obtained using the wheel‐point apparatus. Adoption of the step‐point method in preference to the wheel‐point method saves in equipment and manpower, and renders the technique usable by extension officers and farmers who normally do not have a wheel‐point apparatus. However, the step‐point method does not provide, an estimate of basal cover, and perhaps should not be used on uneven terrain or bushy veld. Using a circular‐quadrat 3,5 cm in diameter yielded a more precise index of basal cover than did the standard method using a point‐quadrat 1 mm in diameter. However, there are disadvantages in using the relatively large quadrat. Possible bias introduced into determining percentage species composition and composition score by using the nearest plant method were negligible.

Uittreksel

Sommige aspekte van ‘n onlangs ontwikkelde tegniek om die agro‐ekologiese toestand van veld te bereken, is deur vier onafhanklike waarnemers ge‐evalueer. Bepaling van veld samestellingtelling het relatief herhaalbare resultate gelewer, naamlik met ‘n sekerheidsperk van 95% vir ±6,43 eenhede vir enige enkele waardering wat ‘n omvang van tussen 0 en 100 eenhede gehad het. Die stap‐puntmetode het persentasie‐veldsamestelling en veldsamestellingtellings gegee wat nie in akkumatheid of in absolute hoeveelheid van die wat deur die wielpuntapparaat verkry is, verskil nie. Deur die stap‐puntmetode bo die wiel‐puntmetode te verkies, word gereedskap en mannekrag bespaar en kan die tegniek deur voorligtings‐beamptes en boere, wat normaalweg nie ‘n wiel‐puntapparaat besit nie, gebruik word. Die stap‐puntmetode gee egter nie ‘n bepaling van basalebedekking nie, en behoort moontlik nie in ruwe of beboste gebiede gebruik te word nie. ‘n Sirkelvormige kwadraat met ‘n deursnee van. 3,5 cm het ‘n meerpresiese indeks van basalebedekking gegee as die standaard metode waar ‘n punt‐kwadraat van 1 mm deursnee gebruik word. Die gebruik van die relatiewe groot kwadraat het egter nadele. Moontlike partydigheid wat in die bepaling van persentasiespesiessamestelling en samestellingtelling deur die naasteplant metode kan insluip, was onbeduidend.