Sowing and Planting

Plant succession

When building soil fertility, it is essential to carry out the right crop rotation, which requires reconciling agronomic timing and organisational measures also in periods of critical accumulation. Growing varieties that tolerate, for example, sub-optimal sowing dates or reduced soil pH can help.

Over the past 25 years or so, crop rotations have become simpler and shorter, mainly as a result of market conditions, i.e. the possibility of easily selling only certain crops. This approach has led to a very high share of cereals in the crop rotation (around 70%) and a very often excessive share of oilseed rape in the sowing structure. In this situation, it is necessary to pay particular attention to the resistance of varieties to pathogens and their tolerance to herbicide residues – neglect in this area produces negative effects very quickly, which cannot be reduced during cultivation. Breeding companies are meeting these needs and are introducing varieties with increased resistance, e.g. to cabbage syphilis in the case of oilseed rape, or to pod disease in the case of cereals. We should look for such varieties if, for example, the share of cereals or brassicas in the crop rotation is too high. However, it should be remembered that the feature of high pathogen resistance may be negatively connected with other plant features, e.g. high winter hardiness, which is often very important for us. Then it remains to look for a compromise, or to significantly restrict the cultivation of certain groups of plants, in specific fields, for several years. In the case of the succession of plants with their tolerance to herbicide residues applied to the preceding crop, the results of studies carried out by companies – manufacturers of plant protection products, as well as State Research Institutes – come to our assistance. These studies compare, for example, the tolerance of potato varieties to herbicides remaining in the soil when another crop in which they were applied has been eradicated and potatoes are subsequently planted. Another example is the tolerance of varieties of other plant species to herbicide residues in the soil when a frozen oilseed rape plantation that had been protected with them was eradicated.

The possibility of growing other substitute plants after eradication of a plantation where herbicides have been used is also indicated in the instructions for use of the plant protection product. Proper crop rotation implies a succession of plants that results in increased soil biological activity. Each plant group or species has its own set of pathogens. Therefore, rotation implies constant replacement of the plant groups cultivated, so as not to trigger pathogen accumulation. The diversity of plants grown is a factor that greatly reduces the intensity of any agrophages. Cultivating plants from other botanical families than those grown most often allows time to recover and reduce the population of harmful organisms. An example of this could be the cultivation of broad bean crops in a typical cereal rotation or with a high proportion of brassicas. A significant increase in the share of a species in the crop structure, for example winter oilseed rape or maize, makes it necessary to arrange the crop rotation in such a way as to limit the share. This is increasingly often the only way to meet the requirements of contractual agreements for the delivery of raw material to processing plants and, on the other hand, to ensure stable and high crop yields, which determine the financial effect of the holding. It is impossible to completely reduce the incidence of agrophages, which is due, among other things, to their presence in the environment. The Internet Agrophage Signalling System operated by the State Plant Protection and Seed Inspection at this address, as well as other decision-support systems already available, provide us with the possibility to track the current dates of appearance of agrophages and recommendations for their control.