Grondversuring en bekalking van Oos-Vrystaatse gronde onder droëlandkoring

[摘要] English: The value of liming of agricultural land has been demonstrated all over theworld during the past century. Therefore liming as an agro-economicalpractice has been adopted widely by farmers with a beneficial impact onsustainable crop production for future generations. However, soil acidity isstill a common yield limiting factor for a variety of crops in the Free State,Mpumalanga, KwaZulu-Natal and parts of the Western Cape.Due to above mentioned reasons incubation and field experiments wereconducted over several years to quantify the following after liming of variousEastern Free State soils. Firstly, the changes in soil acidity parameters andsecondly, the growth and development of wheat cultivars that differ intolerance to aluminium (AI). Over time liming increased the pH(KCI) and decreased the percentage acidsaturation (%AS) significantly in the top- (0-200mm) and subsoil (200-400mm)of all the localities. In the topsoils a good correlation was obtained betweenpH(KCI) and %AS. An increase in pH(KCI) of 0.1 will more or less beconcomitant with a decrease of 5.5 in %AS. The amount of lime needed toraise the pH(KCI) or to lower the %AS up to a specific level, differed betweenthe localities because of buffer capacity. Since pH(KCI) showed a bettercorrelation with lime than %AS, it was decide to use pH(KCI) as parameter todevelop a model with which the lime requirement of a soil can be calculated:Y=8.3240X1-O.0459X2-1.0370, where Y=lime requirement (ton ha),X1=~pH(KCI and X2=clay content (%)At all localities the good AI-tolerant cultivar gave significant higher yields thanthe medium and poor AI-tolerant cultivars. When no lime was applied on theunlimed soils the good AI-tolerant cultivar produced economical yields, which was not the case with the medium and paar AI-tolerant cultivars. The mediumand poor Al-tolerant cultivars responded therefore very well to liming with yieldincreases up to 90%. The good, medium and poor Al-tolerant cultivarsshowed a yield decrease of 15% at an %AS of 30, 10 and 8, respectively.Considering that %AS correlated better with yield than pH(KCI), liming to therequired %AS of a cultivar is a possibility.Differences in AI-tolerance between cultivars resulted in that the optimumeconomic lime levels differ between cultivars. The optimum lime level of thecultivar with good AI-tolerance was the lowest, followed by the medium andpaar AI-tolerant cultivars. Liming of acid soil has become an expensive practice for farmers, which led tothe adoption of planting AI-tolerant cultivars to bridge the soil acidity problem.During this process soils has slowly started to deteriorate with anaccompanying lost of yield and income per hectare. The results of this studyclearly indicate the economical value of liming acid soils for wheat production.

[发布机构] University of the Free State