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Title: TERRAIN EFFECTS ON CORN YIELD DURING A 7-YEAR SMALL PLOT STUDY

Author
item Meek, David
item Singer, Jeremy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/2/2006
Publication Date: 5/2/2006
Citation: Meek, D.W., Singer, J.W. 2006. Terrain effects on corn yield during a 7-year small plot study [abstract]. Eighteenth Annual Conference on Applied Statistics in Agriculture Programs. p. 17.

Interpretive Summary:

Technical Abstract: Landscape characteristics and spatial analyses are commonly used in precision agriculture research mainly in large fields or farm-scale trials. This study examines the effect of elevation or slope on corn yield for 7 years from a comparatively smaller, more conventionally sized, research field. The field’s low relief was thought to be inconsequential because the maximum plot average elevation difference was only 1.5 m. Each year the experiment was conducted on a field in Central Iowa with a total area of 12,300 m² in which final plot unit size was 99.87 m². The experiment is an ongoing multi-year tillage and compost study in a corn-soybean-wheat/red clover intercrop rotation, but only the corn yields are considered in this report. The design structure was a randomized complete block with 4 blocks. The treatment structure had two qualitative factors, tillage and compost. There were 3 tillage treatments: none, moderate, and intensive. The compost, which was split within each tillage main plot, was either present or absent. In 2005, global positioning methods were used to characterize the relief in terms of relative elevation (height above the lowest plot) and slope. When added in the yield ANOVA as a covariate, relative elevation was included in 4 of 7 years, although generally not in a simple linear form. In the other 2 years slope was included. Moreover, patterns were not consistent among years and, in some cases, expected treatment differences that were not evident in the ANOVA, were revealed. Elevation and slope were surrogates for annual environmental factors that were not available. In this field, the major factor was likely the plot level effect of water balance over each crop growing season. Thus, in the analysis of other small plot designed studies, researchers may need to consider the local terrain attributes and effects.