The effects of fertirrigation and Azospirillum brasilense inoculation on photosynthetic compounds of Agave angustifolia

Abstract

Agave angustifolia is the most important species of the genus Agave in Oaxaca, Mexico for its use as raw material for the production of mescal. However, research is lacking on the best agricultural methods for growing this species, including on the most effective fertilizer rates and on the use on bacterial inoculation. Our objective was to evaluate the production of photosynthetic compounds in A. angustifolia plants originating from seeds when they were fertilized by irrigation and inoculated with Azospirillum brasilense. An experiment was carried out in a completely randomized design with a 3×2 factorial arrangement, with the type of irrigation factor at three levels: 1) water; 2) a Steiner nutrient solution composed of N, P, K and micronutrients at 50%; and 3) the nutrient solution at 100%. Subsequently, each irrigation group was separated into two subgroups to evaluate them under the effect of the second factor, inoculation with A. brasilense: 1) inoculated plants; 2) control plants not inoculated for a total of six treatments with 20 plants (replications) per treatment. In each treatment we quantified Chlorophyll a, b and total, Rubisco, and sugars content in foliar samples, as well as the acidity attributed to malic acid at 8:00 and 16:00 hours. We found that plants fertilized and inoculated had bigger leaves with higher amount of Chlorophyll a, b and total and higher amounts of sugars and Rubisco compared to both plants unfertilized and without inoculation and to plants with just fertilization or just inoculation alone. Furthermore, the highest acidity value attributed to malic acid occurred during the first hours of the morning, in the plants of all treatments, but more noticeable in those plants fertirrigated with more nutrient solution (100%) and inoculated with A. brasilense. We therefore advise using both fertilization and inoculation for greater growth and accumulation of photosynthetic compounds in A. angustifolia