DRIS NORMS FOR MAIZE (ZEA MAYS L.) GROWN IN A NETWORK OF THREE TROPICAL SOIL FAMILIES

Benchmark Soil Project experiments were used to establish DRIS norms for maize and determine the influence of environment and genotype on DRIS norms.;It was shown that in general variations in concentration ratios tend to be minimized as yields increased. The method of selecting the high-yielding population resulted in significant differences in the means of optimum concentration ratios and/or their variances. By taking samples from the two highest yielding treatments per replicate per experiment, higher variances in concentration ratios were obtained in each location or soil family compared to variances in concentration ratios obtained from the highest yielding 15% samples. There were significant differences between the means as well as the variances of the Benchmark DRIS norms and the published DRIS norms. Benchmark DRIS norms were significantly higher than published norms. Most of the variance in the Benchmark DRIS norms could be attributed not to differences among soil families but to differences between and within experiments resulting from spatial, temporal and varietal differences.