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Reproduction by seed promotes genetic diversity in maguey (Agave salmiana), and if fertilization is adequate, it can increase growth. In pulque maguey, although reproduction by seed is not a common practice, its study is necessary. For this reason, the objectives of this study were 1) to evaluate the effect of organic and chemical fertilization on growth and 2) to determine the CO2 exchange rate (CER) in two conditions of soil moisture in three variants of A. salmiana (subsp. crassispina, var. salmiana and var. ferox) obtained from seed in San Bartolomé Actopan, municipality of Temascalapa, State of Mexico. The hypothesis was that plants treated with chemical fertilizer will have greater growth than those treated with organic fertilizer and the control, and plants fertilized with organic and chemical fertilizer will have a higher CER in two conditions of soil moisture. The experimental design was completely randomized with n=11 for growth variables, n=3 for nutrient content and CO2 exchange rate. Growth was measured every month in 2.9- to 3.6-yearold plants, and CO2 exchange rate was measured in 3.6-yearold plants with irrigation and in 3.75-year-old plants under water stress. Organic fertilizer from pig manure favored plant height and diameter and number of leaves. The subespecies crassispina had the highest values of the evaluated variables, and A. salmiana var. salmiana cultivated with chemical fertilization was outstanding for the number of shoots emitted. The highest CO2 exchange rate occurred between 22:00 and 02:00 h and was higher in plants with abundant soil moisture (irrigated) than in plants with moisture below permanent wilting point. In the latter condition, the plants grown with organic and chemical fertilizer assimilated 60% more CO2 than the control. [ABSTRACT FROM AUTHOR]