Speaker
Description
Introduction
Sowing winter oilseed rape (WOSR, Brassica napus subsp. napus) with other species has been promoted in Europe for the last 10 years. Various advantages were pointed, like enhanced nitrogen nutrition (Lorin et al., 2016), improved weed control (Lorin et al., 2015) and less insect pest pressure (Breitenmoser et al., 2022). However, in the practice, farmers face difficulties to implement this technique, among them the choice of species intercropped with WOSR or the adaptation of the cropping technique.
Herbicides and insecticides are the most common phytosanitary products used in WOSR, with sometimes several insecticide applications in autumn and in spring. The role of service plants intercropped with WOSR in reducing weed pressure and pest damages has been assessed in field experiments, and in a farmers’ fields network.
Material and Methods
In order to assess the sowing of service plants with WOSR in the practice, an agronomy diagnosis was performed on 28 farmer’s field in the seasons 2018-2019 and 2019-2020. Additionally, the role of the addition of faba bean as service plant with WOSR was investigated in a two-year field trial. The impact of insect pests (Psylliodes chrysocephala, Ceutorhynchus napi, and Brassicogethes aeneus) was monitored over each season according to the standard procedures (i.e. number of larvae per plant (Berlese extraction), number of oviposition punctures, and number of insects per plant, respectively).
Results and discussion
The impact of the intercropping on weeds depends on the choice of species. A comparison of services plants species mixtures showed that non-legumes were the most efficient to increase service plants biomass in autumn and therefore reduce weed infestation, even when included in the mixtures at a low density. However, they can also negatively impact WOSR yield due to a high competition for light and nitrogen. Legume service plants were less competitive with WOSR but due to their slow development, their beneficial effect on the system could be low if they don’t produce enough biomass.
Among legume species, faba bean combines several interesting traits. With a fast development compared to other legume tested as service plants, it could relatively well compete with weeds without resulting in WOSR yield reduction, as it fixes more nitrogen. In field trials, faba bean was shown to mitigate damage caused by the pest complex of Psylliodes chrysocephala, Ceutorhynchus napi, and Brassicogethes aeneus, while having a positive impact on WOSR grain yield. Subsequent observations confirmed the effect on the pest complex. The mechanism behind these results, direct effect through visual or olfactive disruption or indirect effect through WOSR development are under study.
Sowing WOSR with companion plants has the potential to significantly reduce the impact of weed and insect pests on the cash crop, provided this technique is well managed. However, in the case of high pressure, additional measures are needed to secure high grain yields. Along with other alternatives (e.g., cultivar selection, early sowing, trap strip), this approach could reduce the use of synthetic chemistry in WOSR while supporting crop yield and promoting in-crop biodiversity and functional trophic groups.
References
Breitenmoser, S., Steinger, T., Baux, A. & Hiltpold, I. (2022) Intercropping Winter Oilseed Rape (Brassica napus L.) Has the Potential to Lessen the Impact of the Insect Pest Complex. Agronomy 12
Lorin M, Jeuffroy MH, Butier A, Valantin-Morison M (2015) Undersowing winter oilseed rape with frost-sensitive legume living mulches to improve weed control. Eur. J. Agron. 71, 96-105.
Lorin M, Jeuffroy MH, Butier A, Valantin-Morison M (2016) Undersowing winter oilseed rape with frost-sensitive legume living mulch: consequences for cash crop nitrogen nutrition. Field Crops Res. 193, 24-33.
| Keywords | Winter oilseed rape; service plants; pest insect damages ; |
|---|
