GENETIC-IMPROVEMENT OF CORN FOR TOLERANCE TO HIGH PH SOILS

Iron deficiency chlorosis (FeDC) is a major problem for many crop and ornamental plants in Nebraska. The most severe conditions are in river valleys where soil pH may range from pH 5.0 or less, to areas with pH values over 10. The problem of FeDC in various degrees affects nearly 500,000 ha of corn (Zea mays L.) in Nebraska. On a global scale, mill ions of hectares are affected. Soils in most fields are not homogeneou s, thus high pH areas, where crop chlorosis prevails, are intermixed w ith areas of excellent soils that are capable of producing high yields . Corn breeding germplasms and experimental and commercial corn hybrid s were grown on four sites of Cozad silt loam, saline-sodic (Typic Hap lustolls) with pH ranges from 7.4 to 8.6. Marked differences in respon se to the pH 8.6 site resulted in no surviving plants in some genotype s to relatively normal appearing growth in others. No hybrids were fou nd that yielded as well on the pH 8.6 soils as they did on better soil s. However, several that did better on the more severe sites also grew well on lower pH soil. Poor performance on high pH soil (pH 8.0 and a bove) does not preclude a hybrid doing well on lower pH soils. To be o f greatest value, hybrids must produce well on the high pH soils and b e agronomically competitive with other hybrids on less severe sites.