Unravelling the diversity and the temporal dynamics of inter-row management in smallholder immature rubber plantations in Thailand

Today, enhancing the sustainability of rubber-based cropping systems is crucial to ensure sufficient production to meet the growing demand for natural rubber while limiting negative impacts. Inter-row management during the immature period of rubber is particularly important to establish a viable and productive plantation in the long term while starting production as soon as possible. Two main inter-row management options exist in smallholder rubber plantations in Thailand, mono-cropping and intercropping systems. Inter-row management is usually characterized and assessed based on the choice of the crop while the associated technical operations remain poorly considered in the literature. We undertook the detailed characterization of inter-row management including the diversity of technical operations used during the immature period of rubber systems in three contrasted provinces in Thailand. Semi-directive interviews were conducted on 137 plantations intercropped with cassava in Buriram, pineapple in Rayong, upland rice in Trang or with rubber grown as a mono-crop in these three provinces. The 'Typ-iti' method, combining multivariate analysis, clustering and association rules was used to explore the diversity of technical management routes (TMRs). A wide range of inter-row TMRs was observed in each cropping system. The clusters were distinguished according to several management steps along the TMR, making them more complex to characterize than with a single management step or an overall gradient of intensification, especially in cassava and upland rice systems. In the mono-cropping systems, the diversity of inter-row management concerned the technical operations used to control weeds, and differences were identified both within and between provinces. No temporal changes in the TMRs were observed either in the same plot for cassava, upland rice, or in the mono-cropping systems in Rayong, whereas some adjustments over time were identified in pineapple systems in Rayong, i.e. a reduction in the use of chemical fertilizers and herbicides. In mono-cropping systems, the number of weeding operations was reduced in Buriram while in Trang, changes in weeding methods were observed from one year to the next. Among the technical operations identified, those used for pineapple cultivation were the most intense, although there was considerable variability among pineapple growers. This study highlights the wide range of technical operations currently used for managing the inter-rows during the immature period of rubber systems in different contexts in Thailand that may result in varying sustainability performances at plot level. Any evaluation of systems used during the immature period of rubber should thus include management diversity, with both the choice of the intercrop and associated technical operations, to better understand performance variability.