Implementation of a Tunnel System for Scaling-Out High-Quality Cassava Planting Material

Abstract

The production of high-quality cassava planting material is a key strategy for mitigating the spread of pests and diseases. To promote the adoption of such strategies by farmers, it is essential to strengthen local capacities through knowledge transfer and the incorporation of innovative technologies, such as tunnels for rapid propagation (TxRPs), which have been successfully implemented in various international contexts. This study appraised the performance of four industrial cassava (Manihot esculenta Crantz) varieties-Corpoica Tai, Corpoica Belloti, Corpoica Ropain, and Corpoica Sinuana-under tunnel conditions at two locations on the Caribbean coast of Colombia. Planting material consisted of mini-cuttings (7-9 months old) with three buds. Five successive harvest cycles were assessed by measuring key growth parameters, including plant height, leaf number, SPAD (Soil Plant Analysis Development) chlorophyll index, leaf area, and biomass (dry weight and nutrient content). Environmental conditions within the tunnels, such as temperature and humidity, were regulated to promote rapid sprouting and accelerated growth of the cuttings. However, sprouting, vigor, and overall growth performance varied by variety. All four cassava varieties produced high-quality cuttings (>20 mm in diameter and >6 leaves), suitable for further seedling propagation. Cutting vigor increased across cycles, with productivity rising from over 60 cuttings/m² in the first cycle to more than 180 cuttings/m² by the fifth. Substrate mixtures enhanced both physical and chemical soil properties, depending on the source (CRT or CBL). The addition of coco peat or sand effectively minimized environmental impacts by preventing substrate compaction. The findings demonstrate the potential of tunnel-based systems to accelerate the production of high-quality cassava planting material, supporting improved productivity and sustainability in cassava cultivation for both farmers and industry stakeholders.

Keywords: TxRP; cassava seed system; innovation; low-cost technology; scaling-up.

Figure 1

(a) External view of tunnels built in each location: 9 m in length, 3.5 m in width, and 2.4 m in height. (b) Internal distribution of each tunnel showing walking area between central beds (that receive mini-cuttings) and two lateral flat beds that receive seeds trays with harvested sprouts by each cycle. (c) Two-to-three-node cuttings planted on the central sand bed. The density/m² of mini-cuttings is variety-dependent. (d) Details of sprouting for each bud/mini-cutting under the tunnel system. (e,f) Diagrams of average temperature and relative humidity values comparing conditions inside and outside of the propagation tunnel. CRT: Cereté; CBL: Carmen de Bolívar. Error bars represent standard errors.

Figure 2

Principal component analysis of four cassava varieties (Belloti, Ropain, Sinuana, and Tai) grown in TxRPs in two localities (CBL and CRT) at different cut times (C1Cut–C5Cut). (a) Principal component plot. (b) Correlation plot and variable description.

Figure 3

Growth variables of cassava plants established in TxRPs in two locations (CRT and CBL) for four varieties (Belloti, Sinuana, Ropain, and Tai). (a) PCA of the overall results obtained from growth variables for the two locations. (b) Response of growth variables in the two locations. (c) PCA of the overall results obtained from growth variables for variety. (d) Response of growth variables of the varieties. Error bars represent standard errors. Different letters denote significant differences according to Tukey’s test (p < 0.01).

Figure 4

Visual record of cuttings harvested from TxRPs by variety and at two locations (CRT and CBL).

Figure 5

Principal component analysis of four cassava varieties (Belloti, Ropain, Sinuana, and Tai) grown in TxRPs at different cuts. Different colours represent different cuts.

Figure 6

Average growth parameter response of four cassava varieties (Belloti, Ropain, Sinuana, and Tai) grown in TxRPs at different cuts. (a) Cutting height. (b) Number of leaves. (c) Stem diameter. (d) SPAD units. Error bars represent standard errors. Different letters denote significant differences according to Tukey’s test (p < 0.01).

Figure 7

Cutting production/m² obtained in TxRPs in the different cuttings made to from established plant material in the localities Carmen de Bolivar (CBL) and Cereté (CRT). Error bars represent standard errors. Different letters denote significant differences according to Tukey’s test (p < 0.01).

Figure 8

Survival percentage of harvest sprout, 30 DAP on different substrates and locations: (a) Cereté location and (b) Carmen de Bolivar location. S1: soil/sand/vermicompost at 85:10:5%; S2: soil/vermicompost/sand at 60:30:10%; S3: soil/vermicompost/coco peat/sand at 20:20:20:40%; and S4: soil 100%.