Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 19, 2000
Publication Date: N/A
Interpretive Summary: Interest in variable-rate seeding of corn has developed among producers and researchers as one component of precision farming. In this study we evaluated the agronomic and economic consequences of variable-rate seeding in Missouri. Corn was planted in strips of different seeding rates across fields with variation in soil electrical conductivity (EC). Corn was harvested using a combine with a yield monitor and corn population sensors The population sensors were important because they allowed us to measure actual harvested population. We found that harvested population varied considerably from seeding rate, and that the variation was not consistent across a field. We were not able to relate differences in corn yields to seeding rate but were able to relate these differences to harvested population. In some study fields, a single, uniform harvested population across the entire field would provide the highest return. In other fields, ,different harvested populations in areas of differing EC would produce higher returns. Even if uniform harvested population was the best approach, variable-rate seeding would be required to obtain that uniform population, due to variable reductions in plant numbers across the field. This research is important because it provides information on variable-rate seeding specific to Missouri conditions. Most previous research was conducted in the more productive areas of the central corn belt. Beneficiaries will include farmers who are interested in applying variable-rate seeding, extension personnel and crop advisors who need this information to advise farmers, and equipment manufacturers who wish to know if there is a market for variable-rate seeding technology.
Technical Abstract: Variable-rate seeding is now technically feasible and, at least in some situations, may have potential to maximize crop performance and/or maximize economic returns. This study evaluated the optimum harvested population for corn production in Missouri. The relationship of seeding rate and harvested population was also investigated. Seven site-years of studies were conducted in 1998 and 1999 on alluvial and claypan soils in Missouri. Soil electrical conductivity (EC) data were collected prior to planting. Experimental design was a randomized complete block with planting treatments in strips. Corn was planted at five rates using a commercially available variable-rate planter, and harvested by a combine equipped with a yield monitor and corn population sensors. Agronomic optimum plant densities were calculated using harvested population and apparent soil electrical conductivity data. Harvested populations as measured by a combine-mounted sensor were affected by soil and environmental factors. Several fields were shown to have an effect of seeding rate by soil EC interaction on yield. These fields required a variable harvest population to reach maximum yields. Economic returns based on matching optimum populations to soil EC were only slightly higher than having a uniform harvested population. Due to variable stand losses, variable-rate planting could still be required to obtain a uniform harvested population.