An examination of methods of sampling herbage from small‐plot cutting trials

Abstract

Three experiments were conducted to measure variability in sampling for dry matter and crude protein determination in small‐plot cutting trials.

At one harvest of a trial comparing two strains of Panicum maximum, triplicate samples were drawn from the massed harvested material from each plot. The crude protein contents of these samples were determined in duplicate. There was little variation between the crude protein determinations for a single sample, but marked variation in dry matter and crude protein percentages between samples from the same plot. This suggested the need for examining sampling procedures.

Two sampling methods were compared in a trial comparing four grasses, a single sample of herbage being taken from every plot by each method. Sampling the standing herbage before harvest gave a lower estimate of dry matter content and an error mean square 42% less than taking the sample from the harvested material after massing.

Three sampling methods were later compared in the same trial, triplicate samples being taken by each method. Sampling the standing herbage again gave the lowest estimate of error mean square when the results from the four grasses were pooled, but the pattern varied when the grasses were analysed individually. Pre‐harvest sampling again produced a lower dry matter percentage than post‐harvest sampling. It is concluded that further testing is required before pre‐harvest sampling can be generally recommended.

Uittreksel

Die ondersoeke is uitgevoer om die variasie te meet by die neem van monsters vir die bepaling van droë‐materiaal en ruproteiën in kleinperseelsnyproewe.

Tydens die oes van ‘n proef waarin twee lyne van Panicum maximum vergelyk is, is triplikaat monsters uit die totale massa ge‐oeste materiaal getrek. Die ruproteiën van elk van die monsters is in duplikaat bepaal. Terwyl ‘n geringe variasie in die ruproteiën bepalings van ‘n enkele monster voorgekom het, was daar ‘n aansien‐like variasie in beide ruproteiën en droëmateriaal tussen monsters van dieselfde perseel. Dit het daarop gedui dat monsternemingstegnieke dringend ondersoek moes word.

In ‘n ondersoek waar vier grasse met mekaar vergelyk is, is twee monsternemingsmetodes uitgetoets. Elke metode het bestaan uit die neem van ‘n enkele monster uit elke perseel. ‘n Monster wat voor oes geneem is, het ‘n laer droëmateriaalinhoud gehad met ‘n standaardfout van 42% minder as ‘n monster wat na oes geneem is.

Drie monsternemingsmetodes is later in dieselfde proef met mekaar vergelyk. Triplikaat monsters is met elke metode geneem Monsterneming voor oes het weereens die laagste raming van standaardfout gegee waar die resultate van vier grasse saamgevoeg is, terwyl die patroon gevarieer het toe die grasse afsonderlik ontleed is. Monsterneming voor oes het weereens die laagste droëmateriaal gelewer tenoor monsterneming na oes. Verdere ondersoeke is egter nodig alvorens monsterneming voor oes algemeen aanbeveel kan word.