Evaluating maize production potential of selected semi-arid ecotopes using a water balance model

English: The quantitative evaluation of crop production potential is important for sustainable and wise land use as well as for food security where subsistence farmers are involved. It is of particular importance in arid and semi-arid areas where rainfall is marginal and variable. This study aims at making a quantitative evaluation of the maize production potential of the Glen/Hutton and Glen/Oakleaf ecotopes which are located at the Glen Agricultural Research Station in the semi-arid Free State Province of South Africa. The objective was to characterize the ecotopes, and to make long-term yield predictions with a yield prediction model using long-term climate data. A detailed profile description, soil analyses and an in situ drainage curve were made for the Glen/Oakleaf ecotope. Similar data for the Glen/Hutton ecotope was obtained from previous research work (Hensley et al., 1993; Hattingh, 1993; Hensley, personal communication, 2002). A neutron water meter (NWM) was calibrated for each horizon of the Oakleaf soil on the Glen/Oakleaf ecootpe. The plant available water (PAW), defined as the differences between the drained upper limit (DUL) and the lower limit (LL), for maize grown on the Glen/Hutton and Glen/Oakleaf ecotopes was 133 mm and 120 mm respectively. Considering a mature maize crop growing in summer on these two ecotopes, PAW can be defined as the difference between the crop modified upper limit (CMUL) and LL. Results for this parameter were 183 mm and 192 mm for the Glen/Hutton and Glen/Oakleaf ecotopes respectively. The reason for the relatively high value of the latter is its slower drainage rate, which enables the crop to extract more water while drainage proceeds between field saturation and DUL than in the rapidly draining Hutton soil. Yields measured on experiments on the two ecotopes for 12 seasons on the Glen/Hutton and 10 seasons on the Glen/Oakleaf ecotope indicate that these two ecotopes have similar production potentials. For the development
Afrikaans: Kwantitiewe evaluering van gewasproduksie potensiaal is belangrik vir volhoubare grondgebruik en voedselsekuriteit waar kleinboere betrokke is. Dit is veral belangrik in ariede en semi-ariede gebiede waar reënval marginaal en wisselvallig is. Die doel van hierdie studie was om so 'n evaluering te maak vir mielies op die Glen/Hutton en Glen/OakleaJ ekotope geleë op die Glen Landbounavorsingstasie in 'n semi-anede gebied in die Vrystaat Provinsie van Suid-Afrika. Die doel was om die ekotope te karakteriseer, en om lengtermyn oesopbrengs voorspellings te maak met behulp van 'n opbrengsmodel saam met langtermyn klimaatdata. 'n Gedetaileerde profielbeskrywing, grondontledings en veldbepaalde dreineringskurwe is gemaak vir die Glen/OakleaJ ekotoop. Vergelykbare inligting vir die Glen/Hutton ekotoop is verkry van vroeër navorsingswerk (Hensley et al,. 1993; Hattingh, 1993; Hensley, personal communication, 2002). 'n Neutron watermeter (NWM) is gekalibreer vir elke horison van die wortelsone van die Oakleaf grond. Die veldbepaalde plantbeskikbare water (pA JJ? vir mielies, gedefineer as die verskil tussen die gedreineerde boonste grens (DUL) en die onderste grense (IL), was 133 mm op die Glen/Hutton ekotoop en 120 mm op die Glen/OakleaJ ekotoop. Met 'n volwasse gewas op hierdie ekotope in die somer kan PAW gedefineer word as die verskil tussen 'n gewasaangepaste boonste grens (CMUL) en LL. Resultate vir hierdie parameter vir mielies op die Glen/Hutton ekotoop is 183 mm, en vir die Glen/OakleaJ ekotoop 192 mm. Die rede vir die relatiewe hoë waarde van laasgenoemde is die baie stadiger tempo van dreinering wat dan toelaat dat die mielies meer water bokant DUL kan ekstraheer terwyl dreinering nog plaasvind. Opbrengste gekry met veldproewe op die twee ekotope vir 12 seisoene op die GlenlHutton en 10 seisoene op die Glen/OakleaJ ekotoop dui daarop dat die produksiepotentiaal vir mielies op die twee ekotope min of meer dieselfde is. Vir die ontwikkeling van 'n opbrengsm
World Bank
EHRD