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Fluid Journal : Summer 2015
6 The Fluid Journal Summer 2015 Managing In-Field Spatial Variability Variable-rate seeding appears to be the logical way. The Fluid Journal • Official Journal of the Fluid Fertilizer Foundation • Summer 2015 • Vol. 23, No. 3, Issue #89 Spatial variability exists in most farming contexts and farmers are trying to find ways to further increase their productivity by managing this variability. Among the various input management options, variable rate seeding appears as a logical way to manage in-field spatial variability. Worldwide Within-field spatial variability of soil chemical and physical properties (Figure 1) exists in most agronomic environments around the world. There are many natural and anthropogenic (human-made) reasons ranging from geological properties, landscape positions, or climates to as simple as uneven hand broadcasting of inputs in small-scale farming, or merging of fields with different crop histories in medium- to large-scale farming. Quantifying Over the last two decades of precision farming, precision agronomists and soil Drs. L. Longchamps and R Khosla Summary: This study investigates the possibility of increasing crop productivity by optimizing seed rate based on soil fertility levels and productivity potential in various parts of the field. Corn was planted at different planting densities in a research field at Colorado State University. Soil properties were characterized for the entire study area and yield was recorded using a combine harvester equipped with a yield monitor. Results confirm that the relationship between yield and seed rate follows a quadratic curve. Results also indicate that optimal plant population and maximal yields were attained in parts of the field with higher fertility (e.g. higher yield class) than in locations of lower fertility (e.g. lower yield class). ▼ DOWNLOAD scientists have developed methods to quantify spatial variability that exists at the field scale. This has led to the realization that employing average values for managing crop inputs often over-estimates prescription in some parts of the field and under-estimates it in other parts of the field. To avoid these over- and under-estimations, agronomists and farmers are trying to develop site-specific crop management techniques that will enable them to manage the spatial variability that exists in their fields. Variable-rate seeding Plant population appears as a legitimate component of site-specific crop management in addressing spatial variability existing in crop fields. There is a growing interest in variable- rate seeding among farmers and practitioners. This, in part, is driven by increasing seed prices. As seed companies stack additional desirable traits into future crop varieties, the cost of seed will continue to rise. Hence, the technology to vary seed rate, coupled with sound scientific knowledge, will chart the way to make cropping more productive, efficient, and profitable. Some may argue that technology to vary seeding rate has arrived. Others may rightly point out that science to support the decision-making process to gainfully use the current technology is lacking. Objective The goal of this study was to experiment with variable-rate application of seed in a field and assess its effect on yield. Methodology Location. The study was conducted in Colorado during the 2014 crop growing season (April 2014 to October 2014). Climate. The climate of north-eastern Colorado is considered semi-arid as it receives less precipitation than potential evapotranspiration. However, 2014 received one inch above the normal level