Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Winter 1995 Figure 3. Root system patterns of two hybrids used in field research, Oldham and Rehm, University of Minnesota. 145 140 135 130 125 120 115 110 105 100 Yield - bu/A Pioneer 3732 Pioneer 3737 040040 040040 Fall Chisel Ridge-Till K2O rate - lbs/A Figure 2. Corn yields in two tillage systems as affected by hybrid and banded potash, yields avg. of two years, Oldham and Rehm, University of Minnesta, 1991-92. the ridge-till planting system at the West-Central Experiment Station at Morris. Stemming from this, a research project was initiated in the fall of that year to evaluate band and broadcast application of potassium fertilizer on corn in ridge-till and chisel planting systems. To be consistent, Pioneer 3732 and 3737 were used again. The study was repeated in 1992 and results of the two years are shown in Figure 2. Yields shown are averaged for the two years. The soil test value for potassium was 151 ppm. There was a substantial increase in yield of both varieties when 40 lbs/A of potash was fall-applied in the center of the ridge. At this site, the increase was nearly equal for both hybrids. The banded use of potassium also produced a substantial increase in yield of the Pioneer 3732 hybrid in the fall chisel planting system, the hybrid most susceptible to potassium deficiency. Root growth was also measured early in the growing season at this site to determine the effects of tillage system, hybrid, and potassium fertilization. To measure root growth and density, soil cores were taken at various distances from the corn plants at depths of 0 to 6, 6 to 12, and 12 to 24 inches. Samples were collected twice early in the growing season. Following sample collection, soil was washed from the roots, organic matter particles were removed from the samples, and measurements of root length were taken. Differences in development of the root systems were found (Figure 3) and might explain the difference of response between the two hybrids. Early in the growing season, the Pioneer 3732 hybrid appeared to develop a root system that explored less of the soil surface. In the absence of primary tillage, soil test potassium increased or stratified near the soil surface. By contrast, the Pioneer 3737 hybrid, because its root system developed close to the soil surface, was able to more effectively use the higher quantities of potassium found close to the soil surface. Difference in root development between the two hybrids seemed to disappear as corn grew throughout the season. Type of tillage system also had a substantial effect on the development of corn root systems. In ridge-till, a higher percentage of roots appeared to develop in and near the ridge early in the growing season. This difference in early-sea-son development can have a substantial effect on corn yield. More research needed Difference in the architecture of the root system may not be the complete explanation for the response to potash. Other factors, such as changes in bulk density of the soil, and changes in potassium chemistry as affected by moisture and temperature, might be involved. Future research is needed to address these possibilities. The use of banded potash to improve yields in the ridge-till planting system may remove a yield barrier frequently associated with the system. This, in turn, may stimulate farmer interest in the more rapid adoption of this widely accepted soil-conserving system. Oldham is a graduate student and Dr. Rehm is extension soil specialist at the University of Minnesota.
Fluid Journal 1996-1998