Core Ideas: Cover crops can effectively suppress weeds after termination and up to early stage of crop growth. Use of cover crops for early season weed suppression did not affect grain crop yield, but improved yield of vegetable crops. Use of a single cover crop species provided early weed suppression similar to that of cover crop species mixtures. There were differences in cover crop and main crop management among studies that evaluated cover crop for weed suppression. Cover crops are gaining importance as their use has numerous benefits including improved soil health, reduced soil erosion, and weed suppression. Weeds are most competitive with crops at early growth stages, and a management strategy that ensures early season weed suppression in crops is crucial for crop growth, development, and yield. In this study, systematic and meta‐analytic reviews of published studies from 1990 to January 2017 were conducted to provide evidence on whether using cover crops can provide satisfactory weed suppression at termination of the cover crop and up to 7 wk after planting of the main crop. The impact of cover crops as a weed control input on main crop yield was also evaluated. A total of 46 relevant field studies were evaluated. Main crops were planted 1 to 3 wk after termination of the cover crops. Overall, our meta‐analysis results indicated that cover crops provided early season weed suppression comparable to those provided by chemical and mechanical weed control methods in cropping systems. The use of cover crops for early season weed suppression had no effect on main crop grain yields, but could increase vegetable crop yields when compared with no cover crop. Decisions about selecting cover crops species type (broadleaf or grass) or number (single or mixtures) were not as important as identifying cover crops with inherent characteristics that suppress weeds, such as high biomass productivity and persistent residue.

Cowpea (Vigna unguiculata (L.) Walp.) is an important legume crop with enormous nutritional, agronomic and economic value. Cowpea constitutes a large portion of the daily diet among many people in Africa, Asia, Central America, and Southern America. The United States was among the top 10 global producers of cowpea until 1967, when cowpea was grown primarily for soil management and livestock feed. With the projected increase in the minority population in the United States, from 25% in 1992 to 47% in 2050, it is expected that the consumption of cowpea in the nation will increase substantially. In this review, we provide information about cowpea production systems and prospects in the United States.

Widespread and repeated use of glyphosate resulted in an increase in glyphosate-resistant (GR) weeds. This led to an urgent need for diversification of weed control programs and use of PRE herbicides with alternative sites of action. Field experiments were conducted over a 4-yr period (2015 to 2018) across three locations in Nebraska to evaluate the effects of PRE-applied herbicides on critical time for weed removal (CTWR) in GR soybean. The studies were laid out in a split-plot arrangement with herbicide regime as the main plot and weed removal timing as the subplot. The herbicide regimes used were either no PRE or premix of either sulfentrazone plus imazethapyr (350 + 70 g ai ha⁻¹) or saflufenacil plus imazethapyr plus pyroxasulfone (26 + 70 + 120 g ai ha⁻¹). The weed removal timings were at V1, V3, V6, R2, and R5 soybean stages, with weed-free and weedy season-long checks. Weeds were removed by application of glyphosate (1,400 g ae ha⁻¹) or by hoeing. The results across all years and locations suggested that the use of PRE herbicides delayed CTWR in soybean. In particular, the CTWR without PRE herbicides was determined to be around the V1 to V2 (14 to 21 d after emergence [DAE]) growth stage, depending on the location and weed pressure. The use of PRE-applied herbicides delayed CTWR from about the V4 (28 DAE) stage up to the R5 (66 DAE) stage. These results suggest that the use of PRE herbicides in GR soybean could delay the need for POST application of glyphosate by 2 to 5 wk, thereby reducing the need for multiple applications of glyphosate during the growing season. Additionally, the use of PRE herbicides could provide additional modes of action needed to manage GR weeds in GR soybean.