Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: December 7, 1995
Publication Date: N/A
Field research was conducted in 1994 and 1995 at a site (Nashua, IA) where Narrow Strip Intercropping (NSI) systems have been established for four years. NSI involves the use of crop rotation, orienting these crops in narrow, contiguous strips alternating on the landscape. Two (corn and soybean) and three (corn, soybean, and oat plus Berseem clover) crop NSI systems were investigated for their effect on selected weed population parameters. The soil was a Kenyon loam and a ridge-tillage system was used. The experimental design was a randomized complete block, split plot with 4 replications. Weed seed densities in soil differed greatly between the two NSI rotations. Compared to the two crop rotation, corn plots in the three crop rotation had total weed seed banks that were reduced by 47 and 48% in 1994 and 1995, respectively. Soybean responded likewise, with 77 and 54% reductions observed in the two years. Differences in annual grass seed densities (primarily giant foxtail) contributed the bulk of the differences. In the two years of the study, total weed density prior to planting for the two crop rotation ranged from 103 to 433 plants per square m. Conversely, the three crop rotation produced a range of 3 to 99 plants per square m. In general, emergence of weeds throughout the season was also greater in the two crop rotation. However, the magnitude of these differences varied, primarily by year, with the most dramatic response found in 1994. Results of these observations suggested that inclusion of an oat/underseeded forage crop in the NSI system may reduce weed seed banks and weed populations in the row crops. Greater knowledge of the weed population dynamics associated with these alternative systems will help target appropriate management strategies.