Rubber plantation ageing controls soil biodiversity after land conversion from cassava

The rapid expansion of perennial crops is a major threat to biodiversity in Southeast Asia. The biodiversity losses related to the conversion of forest lands to oil palm or rubber plantations (RP) are well documented by recent studies. However, the impact of the conversion from intensively managed annual crops to perennial crops on soil biodiversity has not yet been addressed. This study aims at assessing the impact on soil biodiversity of a) the shortterm effect of land use conversion from cassava crop to RP, and b) the long-term effect of RP ageing. Soil biodiversity (bacterial, fungal and macrofaunal), microbial activities and pedoclimatic characteristics were measured over a chronosequence of 1–25 years old of RP compared to cassava fields, the former crop, in Thailand. The conversion from cassava to young RP (1–3 yr) had a significant effect on microbial biomass and activities and fungal composition, but did not impact the bacterial and macrofaunal diversity. This effect of land use conversion could be explained by the change in land management due to the cultivation of pineapple in the inter-row of the young RP. Canopy closure appeared to be the main driver of soil biota shifts, as most of the biotic parameters, composition, abundance and activities were significantly modified after 7 years of RP. The changes of composition in older rubber plantations originated from the dominance of Trichoderma (fungi), Firmicutes (bacteria), and earthworms. Old rubber plantations (23–25 yr) harboured the highest microbial and macrofaunal biomass; however, they were also characterised by a significant decrease in bacterial richness. The change in pedoclimatic conditions across the rubber chronosequence, i.e. increase in soil moisture, litter and organic carbon content, was a stronger driver of soil biota evolution than land use conversion. The macrofaunal composition was more resistant to land use conversion than the bacterial composition, whereas the microbial biomass was sensitive to land use conversion, but showed resilience after 20 years. However, bacterial, fungal and macrofaunal diversity, macrofaunal and microbial biomass and microbial activities were all sensitive to RP ageing

Diversity, adoption and performances of inter-row management practices in immature rubber plantations. A review

International audienc

Unravelling the diversity of technical operations in diversified perennial-based cropping systems: the case of smallholder immature rubber intercropped with pineapple in Rayong, Thailand

International audienceIntroductionDiversification practices in perennial-based cropping systems (e.g. agroforestry, intercropping, etc.) are promoted for their global positive effects on the agroecosystems’ performances at the plot scale (Beillouin et al., 2019). In Thailand, intercropping with various crops is often adopted in smallholder rubber plantations during the first four years, to cope with the challenges of the immature period. In the literature, these cropping systems are usually characterized by describing the crop choice in the inter-rows only, without considering the associated technical operations (Simon et al., 2024). This study aims at (1) characterizing thoroughly the diversity of technical operations applied to intercrops and rubber trees and; (2) understanding the relationships between the managements of intercrops and rubber trees.Materials and methodsWe conducted interviews in Rayong province, Thailand, with 24 farmers that had at least one rubber plantation between 1- and 4 years old, intercropped with pineapple. All the technical operations applied on pineapple and rubber trees respectively were recorded on a timeline. The "Typ-iti” method (Renaud-Gentié et al., 2014), combining multivariate analysis, clustering and association rules, was used to explore the diversity of technical management routes (TMRs) adopted on pineapple. The technical operations applied to rubber trees were compared with pineapple management clusters through mixed linear models to analyze possible relationships between managements in the inter-rows and rubber rows.ResultsRegarding pineapple management, three initial clusters were observed based on TMR from the soil preparation to the first harvest. Clusters 1 and 2 were constituted of 11 and 8 TMRs respectively, implemented by farmers producing pineapple for industries. They were both characterized by the use of fruit crowns as planting material and an intensive flower induction, but differing in terms of chemical fertilization and weeding. Cluster 3 was constituted of six TMRs, implemented by farmers producing pineapple for local markets, and was characterized by the use of plant suckers as planting material only, with less chemical products used compared to Clusters 1 and 2. A last cluster, named Cluster 4, consisted of TMRs implemented by all farmers, spanning from the first harvest to the second, and was distinguished by a decrease in chemical inputs. A diversity of technical operations was also observed on rubber trees, particularly in the frequency of chemical fertilizer applications, the frequency of weeding operations and the weeding methods used. However, the differences in technical operations applied to rubber trees were not linked to the pineapple management.DiscussionThis study highlights the large diversity of technical operations in rubber + pineapple immature plantations. Contrary to expectations and in contrast to what was observed in other perennial cropping systems (Koussihouèdé et al., 2020), pineapple and rubber trees are managed independently. More globally, our results underline the need to not only consider the crop choice but also the possible diversity of technical operations and the plot level strategies of farmers to better understand the variability of performances in a multicriteria assessment (Perrin et al., 2023).ReferencesBeillouin, D., Ben Ari, T., Makowski, D., 2019. Evidence map of crop diversification strategies at the global scale. Environmental Research Letters 14, 123001. https://doi.org/10.1088/1748-9326/ab4449Côte, F.X., Rapidel, B., Sourisseau, J.M., Affholder, F., Andrieu, N., Bessou, C., Caron, P., Deguine, J.-P., Faure, G., Hainzelin, E., Malezieux, E., Poirier-Magona, E., Roudier, P., Scopel, E., Tixier, P., Toillier, A., Perret, S., 2022. Levers for the agroecological transition of tropical agriculture. Agron. Sustain. Dev. 42, 67. https://doi.org/10.1007/s13593-022-00799-zKoussihouèdé, H., Clermont-Dauphin, C., Aholoukpè, H., Barthès, B., Chapuis-Lardy, L., Jassogne, L., Amadji, G., 2020. Diversity and socio-economic aspects of oil palm agroforestry systems on the Allada plateau, southern Benin. Agroforest Syst 94, 41–56. https://doi.org/10.1007/s10457-019-00360-0Perrin, A., Yannou-Le Bris, G., Angevin, F., Pénicaud, C., 2023. Sustainability assessment in innovation design processes: place, role, and conditions of use in agrifood systems. A review. Agron. Sustain. Dev. 43, 10. https://doi.org/10.1007/s13593-022-00860-xRenaud-Gentié, C., Burgos, S., Benoît, M., 2014. Choosing the most representative technical management routes within diverse management practices: Application to vineyards in the Loire Valley for environmental and quality assessment. European Journal of Agronomy 56, 19–36. https://doi.org/10.1016/j.eja.2014.03.002Simon, C., Thoumazeau, A., Chambon, B., Sajjaphan, K., Metay, A., 2024. Diversity, adoption and performances of inter-row management practices in immature rubber plantations. A review. Agron. Sustain. Dev. 44, 12. https://doi.org/10.1007/s13593-024-00944-