Evapotranspirasie en waterverbruiksdoeltreffendheid van verskillende grasspesies in die sentrale Oranje‐Vrystaat

Abstract

Evapotranspiration and water use efficiency of different grass species in the central Orange Free State. Evapotranspiration (Et) and water use efficiency (WUE) were determined for each of seven grass species during the 1986/87 and 1987/88 seasons. The highest and lowest mean daily Et of 2,39 and 1,66 mm were recorded respectively for Themeda triandra and Sporobolus fimbriatus. Between species, the average Et for the two seasons did not differ significantly. On average the highest and lowest WUE of 7,83 and 4,72 kg/ha above‐ground phytomass produced for each mm water evapotranspired, were recorded respectively for Cymbopogon plurinodis and Panicum stapfianum. The average WUE of C. plurinodis, Digitaria eriantha and T. triandra was 38% (P≤0,01) higher than that of the other four species. Under conditions of moisture stress the WUE of the above‐mentioned three species was the lowest and that of Eragrostis chloromelas the highest.

Evapotranspirasie (Et) en waterverbruiksdoeltreffendheid (WVD) is individueel vir sewe grasspesies oor die 1986/87 en 1987/88 seisoene bepaal. Die hoogste en laagste gemiddelde daaglikse Et van 2,39 en 1,66 mm het onderskeidelik by Themeda triandra en Sporobolus fimbriatus voorgekom. Die gemiddelde Et van die verskillende spesies het oor die twee seisoene statisties nie‐betekenisvol van mekaar verskil nie. Die hoogste en laagste gemiddelde WVD van onderskeidelik 7,83 en 4,72 kg/ha bogrondse fitomassa geproduseer vir elke mm water geevapotranspireer, het onderskeidelik by Cymbopogon plurinodis en Panicum stapfianum voorgekom. Die gemiddelde WVD van C. plurinodis, Digitaria eriantha en T. triandra was oor die proefperiode 38% (P≤0,01) hoër as die gemiddelde WVD van die ander vier spesies. Onder beperkte grondwatertoestande was bogenoemde drie spesies se WVD die laagste en die van Eragrostis chloromelas die hoogste.

Additional index words:

• Above‐ground phytomass
• hydraulic non‐floating lysimeters
• moisture stress