Models for predicting broadleaf vegetable responses to green manures mixtures in semi-arid environment.

The broadleaf vegetables require large amounts of nutrients to provide a high productivity, and quality products, mainly due to their short period of development and growth. The green manuring has emerged as a viable alternative to provide these requirements for these vegetables, mainly from spontaneous species in the Caatinga biome. Thus, the aim of this study was to evaluate and estimate the maximum physical and economic efficiencies of lettuce and arugula agro-economic characteristics in monocropping as a function of equitable quantities of Merremia aegyptia and Calotropis procera biomass mixtures at different growing seasons, using polynomial and exponential models, based on the criteria of biological logic of growth and production of the cultures, of significance of the regression mean square, of high value of the coefficient of determination (R²), of significance of the regression parameters, and of maximization of productivity and profit. The types of polynomial and exponential models chosen estimated the lettuce and arugula agro-economic characteristics with good precision and high R² values. The maximum agronomic (physical) efficiency of the lettuce and arugula was made possible with the incorporation into the soil of 47.38 and 42.23 t ha-1 of M. aegyptia and C. procera, respectively, and the maximum economic efficiency of production for these leafy vegetables was reached with biomass amounts of 45.96 and 33.61 t ha-1, respectively. The rates of return obtained for lettuce and arugula cultivation for the optimized mixture amounts were 2.6 and 1.5 of those achieved in the control treatment (without fertilization), respectively. [ABSTRACT FROM AUTHOR]