Modelling the effect of cultivation on seed movement with application to the prediction of weed seedling emergence.
In order to predict the optimum weeding period, a realistic estimate is needed of the size, timing and duration of a flush of weed emergence in a crop and the soil weed seed bank is the primary source of future weed populations. A vertical movement model was extended to include the effects of a rotavator, a spring tine, a spader and a power harrow on the horizontal displacement of weed seeds. The rotavator caused a backward movement of seeds; neither the spring tine nor spader had a significant effect on the horizontal displacement of seeds; whilst the power harrow had the greatest capacity to move seeds forward >0.5 m in the soil. The depth of burial and vertical movement models were combined to simulate the likely outcome of different sequences of spring tine, spader, rotavator and power harrow on subsequent weed seedling emergence. For example, sequences including multiple passes of a spader increased emerged seedling numbers, whereas when the rotavator dominated the sequence, a marked reduction in seedling numbers was predicted. The combined model provides the basis for a decision support system to aid weed control. Additionally, it provides a research tool to improve understanding of the dynamics of the weed seed bank and the implications of seed bed preparations for future populations.