Aarhus Universitets segl

Non-chemical management strategies for controlling intra-row weeds

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

Intra-row weeds are challenging to control using non-chemical management strategies. For example, it is difficult to remove weeds growing nearest the crop without inflicting crop damage; however, effectively managing intra-row weeds is highly important to limit yield losses resulting from competition for available resources. In the present thesis, various direct and indirect intra-row weed control methods are evaluated for cereal crops and row crops.

In MS I, within the hoed cereal system, where inter-row weeds are controlled, the effects of intra-row weeds on spring cereal growth and yield were described across two crop species (spring barley and spring wheat), two row spacings (narrow and wide) and two nitrogen rates (low and high). Intra-row weeds affected crop yields severely. Lower yield losses and improved intra-row weed suppression were observed in barley compared to wheat, the effects of row spacing were inconsistent, and nitrogen rate did not influence crop or weed response.

In MS II, the manipulation of crop density (ranging from 200– 500 plants m-2), inter-row spacing (narrow and wide), and the addition of pre-emergence tine harrowing were studied for their effects on intra-row weeds in hoed spring barley. A clear relationship between increasing crop density and decreasing intra-row weed density was described. While increasing the seeding rate proved to be a reliable method of weed control, weed response to pre-emergence tine harrowing was not consistent; both greater and lesser intra-row weed biomasses were observed. Row spacing did not affect intra-row weeds, although narrow row sowing produced greater crop yields.

Again, within the hoed cereal system, MS III investigated the effects of three post-emergence slurry placement methods, including application with standard trailing hoses, trailing shoes, and a new design combining the operation of rigid tines and trailing shoes. Crop and weed effects were largely absent. Combining tines and trailing shoes reduced the exposed surface area of slurry in the field, although this did not translate into lower ammonia emissions as was expected. Lower ammonia emissions were observed for trailing shoes, but only in one of three site years.

In MS IV, sugar beet tolerance to hoeing and flaming was studied to inform the development and operation of intelligent automated intra-row weeding machines. It was found that hoeing could be implemented from the cotyledon stage to the four-leaf stage at distances as close as 1 cm from crop plant center without inflicting damage. Sugar beet was more sensitive to flaming at early growth stages; therefore, flame weeding is not appropriate at the cotyledon stage. However, results suggest that direct flaming may be tolerated well enough in sugar beet from the two-leaf to the six-leaf stage to effectively control weeds growing in the close-to-crop zone of the intra-row. At the two-leaf stage, high-dose flaming was tolerated by sugar beet at distances of 1.5 cm and greater.

Finally, in MS V, the effects of cultivation tool (standard ducksfoot shares versus powered rotary hoes) and cultivation frequency (0–4 passes) were studied within a two-year cropping system that aimed to deplete the germinable weed seedbank in bands comprising the inter-row zone of a cereal crop in year one, which would become the intra-row zone of a row crop in year two. Therefore, reduced intra-row weed emergence was expected in year two. However, neither cultivation tool nor frequency had consistent effects on the germinable weed seedbank or intra-row weed emergence in year two. Increasing cultivation had both positive and negative effects on weed emergence in year two, but no seedbank response was observed.
OriginalsprogEngelsk
Antal sider149
StatusUdgivet - nov. 2022

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