No abstract

The effects of pulsed light based-LEDs at eleven frequencies (0.1, 1, 10, 50, 100, 500 Hz, 1, 5, 10, 50 and 100 kHz) programmed at 50 % duty cycle were analyzed, obtaining important parameters of the fluorescence emission of chlorophyll such as: maximum fluorescence (Fm 0 ), minimum fluorescence, the fluorescence emission in steady state, maximum efficiency of PSII (Fv 0 /Fm 0 ), the fraction of PSII centers that are open, photochemical quenching, nonphotochemical quenching (NPQ), quantum efficiency of photosystem II (UPSII), electron transport rate (ETR) and quantum yield of CO 2 assimilation (/CO 2 ). For the study and validation of the results obtained in the experiments, the analysis of variance (ANOVA) was applied 0for each parameter with confidence intervals of 95 %. The results show that the frequencies of pulsed light had positive and negative effects on the fluorescence parameters with respect to the control treatment (continuous light). The frequencies that generated the best performance of Fv 0 /Fm 0 , NPQ, UPSII, ETR, /CO 2 in tomato plants were 0.1, 1, 100 Hz, and 1 kHz. The increase obtained in these parameters can represent an optimal growth and productivity conditions for optimal energy consumption.

The amount of water and fertilizers used in the production of vegetables, specifically tomatoes, is high. This study was carried out to determine water and fertilizers use efficiency in closed and open hydroponic systems for tomato production under greenhouse conditions. Two treatments with eight replications were assessed; each replication consisted of 67 pots with two plants each. One treatment was a closed hydroponic system (with nutrient solution recirculation), and the other was an open hydroponic system (with non-recirculating nutrient solution). We quantified the amounts of water and fertilizers applied, as well as the losses (drained nutrient solution), in the two treatments during the entire cycle of tomato. In the nutrient solution (NS) we also measured electric conductivity (EC), pH, volume applied, and volume drained, and total weight of fruits (25 pickings). There were no significant differences between the two treatments on fruit production. Water use efficiency was 59.53 kg/fruit/m3 for the closed system and 46.03 kg/fruit/m3 in the open system. In comparison to the open system, the closed system produced 13.50 kg more fruit per cubic meter of water, while 10.31 grams less fertilizers per kilogram of fruit produced were only applied. Water and fertilizers use efficiency were higher in the closed system, by 22.68% and 22.69%, respectively. More efficiency was obtained in the closed system, regarding the open system. We concluded that the closed system is a good alternative to produce tomato and preserve the resources involved in the process (like water and fertilizers), thus reducing pollution.

In Mexico, agriculture’s main environmental problems are related to water resources, deforestation and soil erosion. These problems are more acute in arid or semiarid regions such as in the state of Zacatecas. Environmental management systems (EMS) can be an alternate means for improving environmental conditions. In this study, factors that determine willingness to adopt an EMS in the vegetable production units of the state of Zacatecas were identified. We also analysed views on sustainability and production practices oriented toward environmental management and care of natural resources, as well as drivers and barriers to EMS adoption. Factors determining EMS adoption were level of education, awareness of the importance of caring for and protecting natural resources, application of agricultural practices oriented toward protecting the environment, and ignorance of environmental problems.

La limitada disponibilidad de agua que cada vez es más severa a nivel mundial, exige un uso más eficiente del agua en la producción agrícola. Los sistemas hidropónicos cerrados hacen un uso más eficiente del agua, donde la solución nutritiva excedente es recuperada, regenerada y reusada en el mismo cultivo. El objetivo de este trabajo de investigación fue conocer los efectos en producción y calidad de frutos con seis porcentajes de drenaje (%D): 25, 30, 40, 45, 55 y 60%D de la solución nutritiva en un cultivo de tomate. Se usaron macetas con sustrato perlita fina previamente utilizado. La investigación se realizó en el año 2016 en la Unidad Académica de Agronomía de la Universidad Autónoma de Zacatecas. Se midió el número, tamaño, peso y rendimiento de frutos, productividad del agua y la calidad de los frutos (conductividad eléctrica, potencial de Hidrógeno, sólidos solubles, acidez e índice de madurez en zumo) en dos etapas de la producción. Hubo diferencia significativa en rendimiento y calidad para los tratamientos 3 y 4 y 1 y 2 respectivamente. Con % D de 40% se obtuvo mayor rendimiento, pero con 25% de drenaje se aumentó el contenido de sales y azucares en fruto y se obtiene la mayor productividad con respecto a los demás porcentajes.