Speaker
Description
1. Introduction
Grain legumes are key species for the agroecological and dietary transitions due to the numerous services they can provide. However, they are known to be weak competitors against weeds leading to unstable yields. For instance, chickpea (Cicer arietinum) is one of the most commonly grown grain legumes worldwide but suffers from major yield losses because of its poor competitive ability against weeds. Besides, few references are available under European pedoclimatic conditions since chickpea is a marginal crop in Europe. Intercropping has been proved to be a relevant lever to control weeds but can cause yield losses in the main crop (Cheriere et al., 2020). Mechanically controlling the associated species could limit its negative impact on the main crop. This study investigates whether intercropping chickpea with a mechanically controlled service plant allows to facilitate its production by improving the competitive ability against weeds while mitigating interspecific competition.
2. Materials and methods
A field experiment (2023, 2024) was conducted in western France on chickpea-based intercrops. We selected five species of service plants varying in their morphological, physiological and phenological traits: spring oat (Avena sativa), faba bean (Vicia faba), white mustard (Sinapis alba), Sudan grass (Sorghum x drummondii) and Egyptian clover (Trifolium alexandrinum). Chickpea was sown at the recommended density in rows spaced 33 cm apart. In the intercrops, the service plant was sown in chickpea’s inter-row at 50% of the recommended density. Chickpea’s inter-row (service plant, weeds) was either mowed at the beginning of chickpea flowering or left without mechanical control. The selected service plants were contrasted in their response to mowing depending on their ability to regrow (oat, Sudan grass, clover) or not (faba bean, mustard) after being mowed. The experiment was arranged in four randomized complete blocks. Ground cover, accumulation of dry matter (chickpea, service plant, weeds) at 6 sampling dates (5 and 10 leaves, beginning and end of flowering, grain filling, harvest) and N content were measured. Grain yield and thousand grain weight (TGW) were also determined.
3. Results
Our results showed that weed control was the highest when chickpea was intercropped with oat reaching a weed biomass (14 g/m2) lower than the sole crop (82 g/m2) and three other mixtures (59 - 84 g/m2) at the end of flowering. Mowing the inter-row induced a lower weed biomass but only at the sampling date two weeks after the operation. Oat is the only service plant that affected chickpea’s yield dropping from 4 t/ha (sole crop) to 1.5 t/ha with fewer grains and a higher TGW. Mowing the inter-row had no effect on total grain yield and number of grains produced but did induce a higher TGW.
During crop establishment, oat accumulated more biomass (Fig. 1) and nitrogen than the other service plants. At the beginning of flowering, chickpea had a lower biomass and N content in the intercrop with oat than the other treatments. When the inter-row was mowed, chickpea biomass and N content measured at grain filling stage tended to be higher in the mixtures with oat and clover. The chickpea/oat intercrop covered the soil faster but reached a lower final ground cover than the other treatments.
4. Discussion
The intercrops that included a service plant with a delayed biomass production, ground cover and N acquisition compared to oat reached the same level of weed control than the sole crop despite having a higher final ground cover. An early competitive ability against weeds is therefore necessary to guarantee an effective weed control later on in the cycle. In our study, mowing the inter-row did not have a lasting effect on weed biomass.
Oat’s interspecific competition affected not only weeds but also chickpea. It led to a low yield with fewer grains and a higher TGW. The higher TGW observed when the inter-row was mowed without affecting the number of grains shows that we managed to mitigate the competition exerted on chickpea regardless of the associated species. The increasing trends in chickpea biomass and N content in presence of mechanical control support this observation. Overall, this study provides further knowledge on mechanical control as a lever to manage trade-offs between services in intercrops.
5. References
Cheriere et al., 2020. Field Crops Res., 256.
| Keywords | chickpea; intercropping; weed control; interspecific competition, mechanical control |
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