- The temperate crop of sugar beet provides a third example of how plant protection practices have changed over time.
- Sugar beet growers in the UK grow their sugar beet crop on contract to a sugar company. When the harvested crop is transported to the sugar mill, the grower is paid according (a) the weight of the beets delivered and (b) the average quality (% sugar) of the beets.
- To maximise their income, growers aim for large, well-spaced plants with no gaps.
- The top part of the image shows the traditional way of establishing a sugar beet crop. Oxen were used for ploughing, then the seed was sown by hand.
- Once the crop plants reached seedling stage, farm labourers worked through the crop, using a hand hoe to:
1.Remove any weed seedlings that would compete with the crop and reduce yield. - 2.Thin the crop to a density that would result in large beets and an optimal yield per hectare.
- In more recent times, tractors are used to plough, and a seed drill used to sow sugar beet seeds in rows. However, the traditional hoeing practice to remove weeds and reduce a thickly sown crop to an “ideal” density was still necessary (see top diagram).
- As the labour cost of this practice was expensive, growers (and probably farm labourers) were keen to find another solution to achieving an “ideal” crop density. The development of the precision drill, which sows seeds to a specific density, was a step in this direction. Together with the use of herbicides to reduce weeds, both developments contributed to a reduction in the need for hoeing.
- The adoption curves in this graph summarise the sequence of events resulting in growers sowing their beet crop to a stand, finally eliminating hand hoeing.
- Precision drilling was adopted first, closely followed by an increase in the use of herbicide to reduce the hoeing required to remove weeds. The adoption of monogerm beet seed quickly enabled the practice of drilling to a stand to be adopted, removing the need for hoeing.
- The final adoption line shows a steady increase in the use of soil insecticide, due to the fact that the crop became much more susceptible to insect pest attack.
- This was because in crops previously sown to a high density, any beet plant destroyed by pests could often be compensated for by adjacent plants growing larger. In contrast, in a crop drilled to a stand, the greater distance between neighbouring plants means that compensation cannot occur: a destroyed plant results in the complete loss of a mature tuber.
