Improving upon the interrow hoed cereal system: the effects of crop density and row spacing on intrarow weeds and crop parameters in spring barley

Abstract

Automated guidance systems have advanced precise inter-row hoeing in narrowly spaced cereals. Compared to other direct mechanical strategies, hoeing provides superior weed control and improved yields. However, weeds in the uncultivated intra-row zone may survive and compete intensely with the crop, causing yield loss. Therefore, improved intra-row weed management strategies in hoed cereals must be investigated. In spring barley (Hordeum vulgare L.), the effect of crop density was assessed at four levels (200, 300, 400, and 500 plants m−2); inter-row spacing at two levels (15 and 20 cm), relevant to the abilities of current automated equipment to hoe between narrowly spaced rows, and weed management treatment at three levels (no additional controls, herbicide, and pre-emergence tine harrowing). All treatments received inter-row hoeing, and a surrogate weed (Sinapis alba L.) was sown and monitored throughout experiments. The manipulation of crop density was a reliable method for suppressing the growth of intra-row weeds. As barley density increased from target 200 to 500 plants m−2, percent reduction in intra-row surrogate and ambient weed biomass (g m−2) increased from 49 to 82% and 53 to 99%, respectively. Increasing crop density caused a decrease in grain bulk density (kg hL−1) both years, and grain protein (%) and thousand kernel weight (g) in one year; whether these changes constitute a loss in grain quality depends upon end-use. While row spacing had no effect on intra-row weeds, crop yields were 7 to 8% less at 20 cm compared to 15 cm, incentivizing narrow row sowing. Barley yields were unaffected by increasing crop density, and the effect of pre-emergence tine harrowing was inconsistent. In one year, harrowing reduced surrogate and ambient weed biomass and increased barley yield; however, in another year, ambient weed biomass increased, and harrowing did not affect yield or surrogate weed biomass.

Cereal rye seeding rate does not affect magnitude of weed suppression when planting green within Mid-Atlantic United States

“…Similarly, Reed and Karsten (2022) showed no biomass response to increasing cereal rye seeding rates from 34 to 134 kg ha −1 when evaluating delayed termination (i.e., planting green) effects on soybean performance in Pennsylvania. Yet, a positive relationship between crop sowing density and weed suppression is well-described in the literature for small grain cash crops (Mohler 2001) and remains an important component of multi-tactic weed control in low-input systems (McCollough and Melander 2022). Perhaps one reason for the lack of seeding rate response in cover crop research is that sowing cereal rye after late-harvested crops in the fall, coupled with use of burndown herbicide applications prior to sowing, reduces the likelihood of significant winter annual weed emergence flushes that occur at or shortly after cover crop sowing.…”