Timing of post‐emergence weed harrowing

Abstract

Rasmussen J, Mathiasen H & Bibby BM (2010). Timing of post‐emergence weed harrowing. Weed Research50, 436–446. Summary The timing of post‐emergence weed harrowing was evaluated for two years in spring barley with crop‐weed selectivity and crop recovery as the key parameters measured. Selectivity describes the relationship between weed control and crop soil cover immediately after harrowing, with crop soil cover as the percentage of the crop that has been covered by soil due to harrowing. Crop recovery describes the relationship between crop yield loss and crop soil cover in the absence of weeds. Neither selectivity nor crop recovery was affected by timing within a period of two weeks in the early growth stages of spring barley. Selectivity was unaffected by year and 80% weed control was associated with crop soil cover in the range of 23–33%, for all combinations of year and growth stage. Crop recovery was affected by year, with an average crop yield loss of 3.5% caused by 25% crop soil cover in 2007 and complete recovery in 2008. A detailed study of crop growth and weed density in the period just after harrowing, showed that the recovery processes of crop and weeds were influenced by timing of harrowing, but this had no impacts on crop yield. In conclusion, timing of post‐emergence weed harrowing was not found to be crucial, given the condition that the aggressiveness of cultivation was adjusted to the growth stage.

Development and Testing of a Decision Making Based Method to Adjust Automatically the Harrowing Intensity

“…In cases of high weed competition and denser soils, nearly 45% crop soil cover was necessary to achieve 80% weed control [16]. In contrast, other studies suggested a maximum of about 25% crop soil cover [13]. However, higher degrees of crop soil cover than 25% resulted in 3% to 45% yield gain in case of high weed competition, and in cases of poor weed competition the yield loss effect due to harrowing was lower than 1% [16].…”

“…Our proposed harrowing system is advantageous owing to two main reasons. Firstly, it integrates relationships between crop soil cover, weed control and yield increase as a result of harrowing, e.g., as suggested by Weis et al [1], and Rasmussen et al [13]. Secondly, the variables required to determine those relationships ( i.e.…”

“…Higher intensity levels are achieved by decreasing the tine angle relative to a perpendicular axis to the field surface, increasing the depth of the implement, increasing driving speed or through various consecutive passes on the same day of cultivation [6,9,10]. The crop-weed selectivity of harrowing and crop recovery have been studied as key relationships to determine the optimal harrowing intensity [11–13]. Implement settings have not been investigated, thus they were a topic of this study.…”

Mechanical weed control in organic winter wheat

“…Indeed, Pannacci and Tei (2014), summarising the results of eight field experiments on the mechanical weed control in the same area, showed an average weed control efficacy of 37% and 73%, for spring-tine harrow and split-hoeing respectively. Furthermore, other authors affirmed that for the inter-row cultivators the trade-off between weed control and crop damage is not significant and weeds are generally well managed by cultivation, while whole-crop cultivators, like springtine harrows show varying and sometimes poor results (Cirujeda and Taberner, 2006;Cloutier et al, 2007;Peruzzi et al, 2007;Van der Weide et al, 2008;Rasmussen et al, 2010). However, it should be point out as by an economical point of view the inter-row cultivators, like split-hoeing or traditional hoeing, seems to be less sustainable than whole-crop cultivators, like spring-tine harrowing.…”

“…Therefore, selectivity, which is usually characterised by the relationship between weed control and crop damage, is a key parameter in post-emergence weed harrowing (Rasmussen et al, 2008;RuedaAyala et al, 2011). Because of low selectivity, post-emergence weed harrowing may reduce crop yields, especially if weed competition is low, timing is unfavourable or implement setting is inappropriate (Rasmussen and Nørremark, 2006;Rasmussen et al, 2010). Studies shown that the primary action with post-emergence tine harrowing was burying plants (Kurstjens and Perdok, 2000), even if uprooting has been acknowledged to play a role with weakly anchored plants (Kurstjens and Kropff, 2001).…”