A field evaluation of the differential tolerance to soil acidity of forty-eight South African maize cultivars

A field experiment was conducted on a Normandien clay loam (Plinthic Paleudult) to compare the acid tolerance of 48 commercially grown maize (Zea mays L.) cultivars.Cultivars were compared in terms of grain yield, plant height and leaf AI content at four levels of lime (0; 2,5; 10 and 15 t ha -1).Statistically significant cultivar x lime interactions were noted in the case of all three criteria.In the absence of lime relative yields ranged from over 90% to less than 10%, relative plant height varied from approximately 80% to 50%, and relative leaf AI content from less than 150% to over 300%.With a few notable exceptions, probably caused by environment x cultivar interaction, cultivar ran kings obtained with the different performance criteria were generally very similar.After statistical separation of the cultivars into classes, either 'tolerant', 'intermediate' or 'intolerant' in their reaction to acidity, 23 of the cultivars were identically classed using either yield, height or AI content in the absence of lime as performance criterion.On average, 'tolerant' cultivars were 33% taller than 'intolerant' cultivars in the absence of lime, produced more than double the yield, and had a 60% lower leaf AI content.Significantly, several of the least acid tolerant cultivars were among the best pertormers in the absence of acidity.It is considered encouraging that such large cultivar differences in acid tolerance were observed.Not only is it apparent that wide genetic diversity already exists among local maize cultivars with regard to acid tolerance, but the magnitude of the differences is such that the practical consequences are inescapable.