Byproduct utilization of the tequila industry. Part 9. Monitoring of the evolution of composting from two different sources of agave for obtaining a substrate for tomato

The present paper reports on the results of an agave bagasse composting study using ammonium nitrate (NH4NO3) as nitrogen source to adjust the agave bagasse C:N ratio to 25:1. The bagasse was supplied by two tequila factories ("La Codradía" and "La Regional") where the principal difference was the fermentable sugars extraction system. Four piles were formed, two for each bagasse source. Temperature profiles were monitored to assess the progress of the composting process. Average readings were recorded for each day. The parent agave bagasse and composts were analyzed for pH, conductivity, field density, ash content, organic matter, organic total carbon (COT), total nitrogen Kjeldahl (NTK), hemicellulose and cellulose content. After 126 days of composting, the real dry matter lost, and the organic matter and volume theoretically lost were 62.2, 73.6 and 76.9 %, respectively, for compost with "La Codradía" bagasse, whereas for compost with "La Regional" bagasse the respective losses were 65.8, 71.5 and 76.9 %. The composts were also analyzed for particle size, easily available water (EAW), water buffer capacity (WFC), difficultly available water (DAW) and air capacity (AC). Machine refined composts featured some hydrological characteristics similar to those of peat moss. The field study, using the agave bagasse composts as substrates for tomato production, did not reveal statistically significant differences (p < 0.05) when compared to the commercial substrates normally employed to improve nutrient takeup (coconut bagasse and cocopeat) in the first four cuts after 55 days of seedling transplant.