- Fertilization efficiency and rapeseed yield level this year. The season is assessed by prof. Witold Szczepaniak from UP in Poznań.
- Based on the collected data, it can be concluded that, in general, the level of rapeseed yield this year was lower than in the previous year.
- The analysis shows that only in some regions/farms comparable yields were harvested, but in most cases they ranged from 50 to 80% of last year's yields.
Rapeseed yield lower than last year
In the light of the information presented, the question arises whether one of the reasons for the generally lower rapeseed yields could have been the lower efficiency of fertilization, which, as already mentioned, could have resulted from specific conditions in the past growing season? Of course, answering this question is not easy and requires a detailed analysis of economic conditions. We asked Prof. to reflect on this matter. Witold Szczepaniak from UP in Poznań.
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Autumn vegetation and rapeseed yield?
As the scientist notes, it should be noted that in the autumn of last year, rapeseed generally had good conditions for development. Especially in September, which was characterized by record average daily temperatures (although this concerned areas where there was no water deficit in the soil). This resulted in the fact that already at the turn of September and October in many plantations the plants showed the development that they should have before winter dormancy, i.e. they developed 10 to 12 fully developed leaves. And then they continued to develop until the end of November, when the first "attack" of winter occurred. Therefore, before winter, they were often characterized by above-average development.
However, provided that they had an appropriate pool of nutrients, especially nitrogen. It must be borne in mind that the greater the biomass, the greater the nutritional needs. Therefore, when growing rapeseed last year, it was necessary not only to plan appropriate pre-sowing fertilization (usually after cereals, 40-50 kg N/ha should be applied), but also to correct the fertilization during the autumn vegetation. It should be borne in mind that properly developed rapeseed accumulates about 80 kg N/ha in autumn, while overgrown plantations accumulate much more than 100 kg of this nutrient. Hence, in the absence of top dressing with nitrogen, deficiency symptoms appeared on many plantations, and it must be remembered that rapeseed builds the foundation for future yields in the autumn. Among other things, from the stage of 7-8 leaves, flower buds, i.e. future siliques, form, and the effectiveness of this process depends on the supply of nutrients to the plant, including nitrogen. Therefore, one of the reasons for lower rapeseed yields this year should not be seen in the lower efficiency of fertilization in autumn, but in the deficit of nutrients, especially nitrogen in relation to the demand, which, as already mentioned, was at an increased level.
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Rapeseed prices on MATIF are making up for losses
Spring season and rapeseed fertilization
At the same time, above-average plant development led to the depletion of nitrogen from the soil. Therefore, in spring, it was necessary not only to rebuild the concentration of this ingredient in plants but also in the soil, so that after resuming vegetation, the plants could regenerate after winter and develop an appropriate yield structure. Therefore, the spring dose of this ingredient, especially in plantations with deficiency symptoms, should be higher than last year. At this point, it should be recalled that properly developing rapeseed should absorb most of the nitrogen it needs before the beginning of flowering (at least 70, and preferably about 80%). To make this possible, nitrogen is usually applied in very early spring in two doses at a short interval. So that after the second dose, the plants have at least 4, and preferably 6-8 weeks to flower.
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Deal with sclerotia before sowing rapeseed
Fertilization was sometimes late. This year was special
Unfortunately, this year, due to the prevailing conditions, spring fertilization was often late, sums up Prof. Szczepaniak. This was due to both the inability to enter the field (excessive soil moisture) and the accelerated vegetation (due to weather conditions, the plants this year began to bloom 2-3 weeks earlier than in previous years). Therefore, in this situation, the lower level of rapeseed yield could result, among other things, from the lower effectiveness of spring nitrogen fertilization. All the more so because while above-average rainfall was recorded in the autumn and winter period, after fertilization the amount of rainfall was insufficient, especially in March, and then from the third decade of April to the second decade of May inclusive (or longer).
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Rapeseed in Lower Silesia and the Opole region is the worst in years?
Water limited the building of the crop
According to prof. Szczepaniak, the deficit of rainfall in the first period directly limited the effect of fertilizers, because in order to achieve their high effectiveness, they not only have to dissolve but also move deep into the soil, and after fertilization, at least several dozen liters of water/m2 are needed. However, in the second period, it contributed to a significant reduction of the yield components, i.e. the number of pods, seeds in pods and their weight. All the more so because it occurred already during the flowering of rapeseed, i.e. the development phase in which the plants have the greatest demand for water. And then it continued during the seed pouring period. Therefore, in many plantations this year, the plants not only had a smaller number of siliques, but they were much shorter than in previous years (they had a smaller number of seeds), which was the result of their development in autumn and spring.
