Organic matter and its relation to maize crops on acid soils of Colombia

Abstract

To examine genotype * environment interactions with respect to the adaptation of maize (Zea mays) cultivars on acid soils of the tropics characterized by aluminium toxicity and low availability of nitrogen and phosphorus, a long-term field experiment was carried out on an Oxisol of the Eastern plains of Colombia [1997-99]. Treatments applied were as follows: two sources of organic matter (OM; chicken manure and cowpea shoots at 5 t ha-1 each), two phosphorus rates (25 and 50 kg P ha-1), two levels of limestone (0 and 1.5 t ha-1) and three maize cultivars with differential tolerance to soil acidity. The experimental results showed that grain yields remained fairly stable with time at all treatment levels. The application of OM combined with lime and P produced the highest yield increment compared to the unamended control. The maize cultivar Sikuani by far out-yielded the other cultivars in the unamended control treatment. The soil acidity-sensitive cultivar ICA had particularly very low yields in the control treatment. On the other hand, cultivar ICA had the largest grain yield response to lime, P and OM applications, followed by cultivars Clavito and Sikuani. Application of lime produced the greatest yield increase in cultivar ICA. Application of OM further significantly enhanced maize yields, whereas the effect of cowpea green manure was rather small. Mean grain yields over the five seasons at the highest level of soil amendments (combination of lime, P and OM) were 4843, 3879, and 4741 kg ha-1 for ICA, Clavito, and Sikuani, respectively. With combined lime/organic matter application the available P and the exchangeable aluminium in the soil changed from 6 to 32 mg kg-1 and from 2.1 to 0.2 cmolc kg-1, respectively, whereas the Al, Ca, and Mg saturation percentages changed from 73 to 6%, 10 to 35%, and 3.7 to 9%, respectively.