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As the first fruit produced on the island, the 'Queen Victoria' pineapple (Ananas comosus [L.] Merr.) holds an important role in the economy of Réunion Island. However, to reduce pest damage and ensure profitable production, pineapple crop remains largely intensive, relying heavily on synthetic inputs. Weeds are one of the most significant biotic constraints for pineapple producers, which are primarily controlled through plastic mulch and herbicides. The plastic mulch is not a long-term solution due to its composition and management after the pineapple cycle. French legislation is increasingly restrictive on the use of chemicals including herbicides, in response to demand for healthier and more environmentally friendly foods. More agroecological alternative solutions are needed, but studies on weed control during pineapple crop are limited. Understanding the impact of weeds on pineapple crop is essential for implementing effective solutions.
Because pineapple is a slow-growing plant with shallow roots, it suffers greatly from weed competition, particularly during a period of crop-weed interference defined as critical and which can reduce the crop's production capacity (Knezevic et al., 2002; Oliveira et al., 2021). Understanding this critical period would enable pineapple producers to optimize their weeding program, by knowing when to weed and reducing the number of interventions. The objective of this study is to determine the critical period of weed interference in pineapple crops. We aimed to address two research questions: i) What is the critical period of weed interference? ii) Which pineapple traits are affected by weeds, in terms of vegetative development, yield and quality at harvest? We conducted a field experiment at the CIRAD station on Réunion Island in 2022. The 3-replication design included 2 weeding regimes: weed-free plots (hand-weeded; CT) and weedy plots (no weeding; WD). Each regime consisted of 7 levels of weed duration, varying every 2 months from pineapple planting to harvest at 14 months i.e. 0, 2, 4, 6, 8, 10, 12 and 14 months of weed control or pineapple-weeds coexistence.
The results showed that the presence of weeds led to yield losses, in proportion to the weed cover duration: the longer weeds were present in pineapple plots, the higher the yield losses. Weed-free plot yields reached 33.9±5.9 tonnes per hectare, compared with 0.14±0.13 t/ha for the plots with the most weeds. The critical period of weed interference for a 5% yield loss was between 3 and 11 months after planting, i.e. 240 days. Beyond 8 months of coexistence between pineapples and weeds since planting, yield loss could reach 90%. The leaf emergence rates and weight of pineapple plants were significantly affected by the weed presence. Despite the continued presence of weeds, the pineapple plants remained alive at the end of the experiment but their cycle length was significantly prolonged, with flowering rates not exceeding 10% beyond 6 months of pineapple-weeds coexistence. In addition, pineapple quality at harvest was significantly affected from the fourth month of weedy plots. Fruit analysis showed lower Brix (sugar content) and higher acidity. These results suggest that yield reduction could be explained by a strong competition for resources between weeds and pineapples, with the degree of competition increasing with the duration of coexistence. This competition influenced pineapple yield components, reducing fruit weight, size and quality.
Understanding the critical period of weed interference is useful to do integrated weed management programs and facilitate the development of agroecological pineapple production systems based on the introduction of biodiversity to provide services such as weed control, soil fertility, erosion control. Combine knowledge of weed community composition and pineapple-weed interactions through a functional trait-based approach, it is possible to determine the type of species and the strategic time for planting cover crops and intercrops.
Knezevic, S.Z., Evans, S.P., Blankenship, E.E., Acker, R.C.V., Lindquist, J.L., 2002. Critical period for weed control: the concept and data analysis. Weed sci. 50, 773–786.
https://doi.org/10.1614/0043-1745(2002)050[0773:CPFWCT]2.0.CO;2
Oliveira, S.P. de, Santos, J.C., Leite, B.N., Santos, G.A.N. dos, Silva, J.F. da, 2021. Critical period of weeds interference in pineapple (Ananas comosus [L.] Merr.) crops. BASE 25, 120–128.
https://doi.org/10.25518/1780-4507.18985
| Keywords | agroecology; Ananas comosus; weed competition; agroecosystem; integrated weed management |
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