OFR: Influence of the choice of variety on the demand-based fertilisation | 21.09.2010

Which influence does the choice of variety have on a needs-based fertilisation? Does the growth height of the plants differ with respect to their uptake and use of nitrogen? Is the yield reaction variety specific dependent on the conductivity of the soil? These questions have recently been investigated by farmers throughout Germany in large scale variety trials.

In the so-called on-farm research Maximus winter oilseed rape semi-dwarf hybrids were compared with normal straw varieties with respect to their nitrogen uptake and yield stability. The assumption was that the “short ones” would differ clearly from the normal straw varieties with respect to the N uptake – founded on the changed root morphology, the more favourable corn-straw relationship as well as the delayed spring development, characteristic for the growth type. Furthermore, one assumed that the more competitive root system of the new growth type would be better suited to changing soil conditions, as are found within large fields.

In order to check this hypothesis, two trial series were laid out in the vegetation period 2008/09:

1. Trial series 1: In 6 trials the Maximus semi-dwarf hybrids PR45D03 and PR44D06 were compared to the normal straw hybrids PR44W22 and PR46W31.
2. Trial series 2: At 22 locations throughout Germany the semi-dwarf hybrid PR45D03 was compared to an own farm normal straw variety, each in a large field parcel.

The YARA N-Sensor was used to measure the N uptake of the plant stand up to the start of flowering. The soil heterogeneity occurring on the trial field was recorded with the soil scanner EM 38 in the form of its apparent electrical conductivity. The combine harvesters were equipped with yield mapping systems.

Specific N fertilisation?

According to the available results of trial series 2008/09, the clearest difference between semi-dwarf hybrids and typical varieties is not in the amount of nitrogen taken up and effecting yield. It lies in a temporally delayed N uptake after the winter. A large advantage in practice as: the early N requirement of normal straw varieties tempts farms to apply ammonium based fertiliser early on. The risk of loss of fertiliser into the atmosphere is thus increased since the soil is, for example, too wet or frosty and the plants are not able to take up the nitrogen. This pressure for early application disappears thanks to the weaker need of the semi-dwarf hybrids. This also lowers the risk of possible losses in the first N application.

Influence of the conductivity on grain yield

Growth type specific yield effects dependent on the electrical conductivity of the soil could not be determined in this investigation. The yield reaction dependent on the proportion of fine soil in the earth is thus not a suitable parameter for the selection of varieties.

Conclusion

According to the results available here, the noticeable short growth type of the semi-dwarf hybrid does not require a smaller application of N fertilisation, as is assumed by the lowered amount of plant material. However, the “shorter one” transforms the nitrogen into a higher yield. A clear delay is determined in the uptake after the winter. This makes lower demands on the availability of nitrogen in this time period.