|Myers, D - UNIV OF MO|
|Hong, S - NAT INS AG SCI&TECH S KOR|
Submitted to: Proceedings of American Society of Agricultural Engineers
Publication Type: Proceedings
Publication Acceptance Date: July 31, 2003
Publication Date: July 31, 2003
Citation: KITCHEN, N.R., SUDDUTH, K.A., MYERS, D.B., DRUMMOND, S.T., HONG, S.Y. SITE-SPECIFIC PRODUCTIVITY ZONES DELINEATED USING BULK SOIL ELECTRICAL CONDUCTIVITY. AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS ANNUAL INTERNATIONAL MEETING TECHNICAL PAPERS. 2003. CD-ROM. PAPER 032340. ST. JOSEPH, MI. Technical Abstract: Efficient and cost-effective methods are needed for delineating sub-field productivity zones to improve soil and crop site-specific management. This investigation was conducted to answer the question of whether bulk soil electrical conductivity (ECa) and elevation could be used to delineate soil-based productivity zones (SPZ) for claypan soil fields that would agree with productivity zones delineated from yield map data (YPZ). Ten and seven years of combine-monitored yield maps were available for two Missouri claypan soil fields. The fields were generally cropped in corn and soybean. Soil ECa data were collected with a non-contact, electromagnetic induction-based ECa sensor (Geonics EM38) and a coulter-based sensor (Veris 3100). Elevation data were collected using a real-time kinematic GPS. Unsupervised fuzzy c-means clustering was independently used both on yield data to delineate three YPZ, and then on combinations of ECa and/or elevation data to delineate three SPZ. Outcomes of YPZ and SPZ were matched and agreement calculated with an overall accuracy statistic and a statistical index called the Kappa coefficient. The five SPZ outcomes that gave the highest Kappa coefficient were reported. Best performing combinations of ECa and elevation variables gave 60 to 70% agreement between YPZ and SPZ. We consider this level of agreement promising, especially considering the fact that there were many other yield-limiting factors unrelated to ECa and elevation. Generally multiple variables of ECa and elevation were better than a single variable for generating SPZ. Half of the years' maps showed yield spatial variability was primarily caused by moisture deficiency. Because of the heavy weighting from "deficit" moisture years, creating YPZ with only deficit years did not alter the combination of ECa and elevation variables that performed best, as compared to using all years to generate YPZ. The combination of ECa and/or elevation variables that gave highest agreement between YPZ and SPZ were field specific. Contrasting results from the two fields indicated field characteristics need to be taken into account when developing productivity zones. Based on these findings, we conclude ECa and elevation measurements could be reliably used for creating productivity zones on claypan soil fields.