Optimerad höstveteetablering : en litteratursammanställning om såtid, radavstånd och utsädesmängd
Abstract: This bachelor thesis is intended to gather the knowledge and experimental data on the winter wheat crop production relevant for Swedish conditions, with focus on sowing time, row spacing and seed rate. This essay is a literature study with a minor component based on interviews with farmers producing winter wheat. The work is divided into a background part where basic knowledge of winter wheat physiology, development and environment interactions are described and one part where results of field trials studies are presented. Optimal date of sowing winter wheat depends on annual weather variations. Because it is difficult to forecast the weather the choice of sowing date should be based on weather statistics, production experience and previous results depending on sowing date. The date of sowing must also be adapted to the current field conditions to achieve the best results. In southern Götaland the recommended sowing period is 10th to 25th of September, in northern Götaland the recommendation is 10th to 20th of September and in southern Svealand 10th to 15th of September. If there is no capacity or conditions to sow the planned acreage in the recommended sowing period a slightly earlier sowing is preferred rather than a later sowing. Some years the early sown winter wheat gets declined yield according to winter losses, mainly due to pathogens. In southern Götaland the yield reduction caused by delayed sowing is smaller than in northern Götaland and the reduction is even higher in southern Svealand. In Sweden, 12,5 cm is the most common row spacing in grain production. In experiment with row spacing less than 10 cm, no or very small yield increases was observed comparing to 10 cm row space. Row spaces wider than 10 cm results in a decreased grain yield, especially in high yielding cultivations. The row space studies made in Sweden are old and based on smaller amount field trials, therefore there should be a motivation to carry out new experiments on row spacing. Based on the results found from the examined experiments, 10 cm is likely to be the most economically spacing option. It means a denser row spacing than commonly is used today. Wider row spacing can be interesting if it causes substantially reduced establishment costs, if it is able to compensate for a likely yield level reduction caused by the wider spacing. In organic cultivation wider row spacing is an opportunity for developed mechanical weed control, where a lower weed amount can increase the yield. Seed rate should be adapted to the growing location, sowing conditions and date of sowing. Seed rate can be varied relatively much without major differences in growing profitability if the growing conditions are good. In normal time for sowing about 350 viable kernels/m2 is recommended in southern Götaland, corresponding suitable seed rate in northern Götaland is about 400 and in southern Svealand just over 450 viable kernels/m2 is recommended. When sowing before suggested sowing period a decrease of seed rate with 10-20 % per week. If sowing is delayed after the optimum time, the recommendation is to increase the seed rate with 5-10 % per week instead. In case of limited nutrient availability or growing soils sensitive for drought is usually a reduction in seed rate by 10-15 % economically favorable. There is a need of new trials studying the effect of varying seed rates depending on row spacing under conventional conditions. This is motivated because of the limited numbers of available studies and the need of knowledge if the variety of row spaces will be more common.
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