Row spacing affects the ease of stubble handling at sowing and of controlling disease events in some crops. It also influences crop fertiliser use options. When all other factors are equal, narrow crop rows usually deliver much better crop competition than do wider rows. However, wider row spacings may in some instances lead to improved ability to obtain even crop establishment through more accurate seed and fertiliser measurement and placement. This can result in improved early vigour and ultimately increased crop competition.
When making decisions regarding row spacing, consider:
Paddock conditions (eg the weed burden and stubble load)
The capacity of the equipment or machinery available
Crop type and variety
Opportunities or limitations for pest control (eg inter-row weed control)
Opportunities for improved fertiliser placement (eg deep banding).
Whichever row spacing is used, always ensure an optimum sowing rate is maintained. Depth of seed placement, covering depth, seed–soil contact, crop density, fertiliser placement and under furrow soil strength are further considerations. These will affect the competitive ability of crop seedlings with weeds, and the germination and growth of weeds. Another important parameter in the sowing operation is the ratio of disturbed to undisturbed soil surface. Sowing equipment components should minimise soil surface disturbance. Each point on a tyne-based sowing machine will disturb a strip of soil equal to twice the operating depth of the point plus the width of the point. As operating speed increases, soil throw makes this ratio even higher. Weed seeds left on the soil surface are less likely to germinate and more likely to suffer predation.
Increasing crop density increases weed suppression. In cereals higher crop densities can achieve further suppression if narrower row spacings are used. When the weed burden is high the impact of weed competition on crop yield is high, and the benefit obtained from narrow rows on weed management procedures is significant.
It is important to match row spacing and sowing rate to obtain crop plant densities that are optimal for both yield and competition against weeds. For instance, in annual ryegrass seed production was reduced with narrow row spacings, particularly at higher sowing rates.
Article: CulturalWeedControl172 (permalink) Date: 9 January 2013; 7:46:47 PM AEDT