MAIZE NODAL ROOT RESPONSE TO SOIL RIDGING AND 3 TILLAGE SYSTEMS

A greater understanding of maize (Zea,nays L.) nodal root response to soil ridging and tillage systems is needed to maximize the benefits of ridge-till and other conservation tillage systems. Field (1992 and 1993 near Marshalltown, IA) and greenhouse (two studies with two trials each) experiments were conducted to examine the effect of soil ridging, height of ridging, and three tillage systems (no-till, ridge-till, and chisel-plow) on the number and stem node position of maize nodal roots and on internode length. Field plants were ridged during cultivation. In the greenhouse, ridging was simulated by using polyvinyl chloride rings to hold soil around the base of plants. Numbers of nodal roots, numbers of nodes developing functional roots, internode lengths, shoot dry weights, and grain yields (field study) were determined. In one greenhouse experiment, unridged plants developed an average of 38.4 functional nodal roots, while ridged plants developed 50.0, an increase of 30%. In the same greenhouse experiment, ridging significantly increased lengths of Internodes 6 and 7, which were covered with soil during ridging. Average length of Internode 7 increased from 64 mm to 101 mm with ridging. Increasing ridge height increased internode length and number of nodal roots in the controlled greenhouse experiments, but not in the field. In field experiments, ridge-till caused development of significantly more functional nodal roots as compared with no-till (1992 and 1993) and chisel-plow (1992). Plants from no-till developed 53.1 and 46.0 functional nodal roots in 1992 and 1993, respectively, while plants from ridge-till developed 58.7 and 49.1 roots. Shoot dry might and grain yield were not affected by ridging or tillage treatments in the greenhouse or field.