Abstract

GARBANZO LEON, Juan Gabriel  and  NAVARRO FLORES, Juan Ramón. Multi-criteria analysis of chemical, physical and biological variables of 10 horticultural substrate mixtures in Guanacaste, Costa Rica. InterSedes [online]. 2015, vol.16, n.33, pp.72-81. ISSN 2215-2458.

The effect of ten substrate mixtures used to produce horticultural seedbeds in the region of Guanacaste was assessed. They were made from local materials such as bokashi, compost, and worm compost, sand, soil, coconut fiber and rice hulls. The objective of the study was to find a mixture that effectively replaces imported peat moss, which is the most frequently used substrate in the seedbed industry. Chemical, physical, microbiological and agronomical variables were measured to assess the mixtures. The tomato plant (Solanum lycopersicum) was chosen to assess the substrates. The test method used was a completely randomized design with four repetitions. The test units used were 72-cell trays. The total area was 48 cells and 24 comprised the useful area. A total of 36 variables (11 agronomical, 14 chemical, 8 physical and 3 microbiological) were assessed. Due to the complexity of choosing the substrate with the best characteristics, using a multi-criteria method was chosen to summarize the outcome of the 36 variables in a single value that weighted each of the characteristics tested by each of the variables. A weighted value (V_i) was assigned to each of the variables according to its importance in the context of the test. Each variable was submitted to a variance analysis and the mixtures were grouped by the least significant difference test. In each case, the difference between the means of the treatments created three groups, which received a number of points: 1, 2 or 3 (X_j) according to the assigned group for the test. The Weighted Index (I.P.) was obtained by adding the result of multiplying the V_i and X_j values. The obtained sum was divided by the maximum possible points and the result multiplied by 100 in order to obtain a value relative to the others. It was found that the mixtures of (50% worm compost + 25% bokashi + 25% rice hulls), (50% bokashi + 25% compost + 25% coconut fiber) and (50% compost + 25% bokashi + 25% coconut fiber) obtained weighted index values greater than those of peat moss. This opens up the possibility of reducing costs by replacing imported input in the production of seedbeds under the conditions of Liberia, Guanacaste.

Keywords : multi-criteria methods; seedbeds; substrate mixture; production costs.

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