|Tapela, M - BOTSWANA COLLEGE OF AGRIC|
|Baker, J - IOWA STATE UNIVERSITY|
|Cruse, R - IOWA STATE UNIVERSITY|
Submitted to: Tillage Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 20, 2003
Publication Date: June 20, 2003
Citation: COLVIN, T.S., TAPELA, M., MEEK, D.W., COOK, J.D., BAKER, J., CRUSE, R., KARLEN, D.L. A LOOK BACK AT A LONG TERM TILLAGE EXPERIMENT AND A LOOK FORWARD AT THE POTENTIAL FOR SITE SPECIFIC TILLAGE. TILLAGE CONFERENCE PROCEEDINGS. 2003. CD-ROM. WOOSTER, OH. Technical Abstract: A tillage experimental area has been in place since 1976. Five tillage treatments (moldboard, chisel, till plant, slot plant, spring disk) were compared using randomized complete block design with four replications. Ten years of records (1991-2000) from the experimental area were examined for long term trends. The no till corn yield in continuous corn was significantly less than all other treatments and over 20% less than the treatment using the moldboard plow in the fall. The no till treatment for corn following soybean was significantly lower than the fall moldboard plow treatment but numerically only 4% less. The potential for site specific management relates to the fact that multiple years of yield data from the same field usually exhibit both spatial and temporal variability. Often it is difficult to explain this variability because yield is affected by many factors including soil conditions, weather and management practices. This study was conducted to determine if yield maps, in combination with soil information, would explain the annual variation in corn (Zea mays L.) yield. The data were from the long term field study conducted on Typic Hapludolls and Typic Haplaquolls soils between 1998 and 2000. Analysis of variance showed no significant yield differences between tillage treatments in either 1998 (p=0.275) or 2000 (p=0.150). Significant differences were observed in 1999 (p<0.0001). Moldboard tillage was highest at 9.96 Mg ha 1 and slot planting lowest with 7.75 Mg ha 1. A paired t test showed no significant yield differences among soil types in 1998 (p=0.106) and 1999 (p=0.257). There were significant differences in 2000 (p=0.0001). Visual interpretation of yield maps with soil map unit overlays supported both statistical analyses. A significant season, and season by tillage interaction was identified. Significant differences in bulk density and penetration resistance influenced the mean yield for each treatment. Soil moisture levels in all treatments for 1998 and 1999 were not significantly different, but in 2000 there were significant differences (p=0.0185), with disk and moldboard treatments being significantly drier than the other tillage treatments. This study shows that soils and yield maps can be used to better understand results obtained by classical statistical methods.