Efectos de la posición de plantación y la aplicación de Azospirillum brasilense en el crecimiento inicial de la yuca (Manihot esculenta crantz).

This work aimed to evaluate the effect of the strick planting position and Azospirillum brasilense application on the initial growth of cassava. The assay was carried out following a completely randomized experimental design, with factorial arrangement (planting positions [horizontal (HP) and vertical (PV)] and the A. brasilense [with (+Azos) and without (-Azos)]). The sprouting percentage (SP) was evaluated from 11 to 35 days after planting (DAP). After 30 DAP, the following variables were evaluated: sprouts number (SN), sprouts height (SH), number of leaflets (NL), length of leaflets (LL), and vegetative vigor (VV). Cassava plants positioning significantly influenced the initial growth. PV promotes a greater sprouting, 63% in 17 DAP, over the PH which was only 3% of the visible shoots during the same period. Here we show for the first time that PV promoted the highest values combined with -Azos in the variables SH (an increase of 17%) and VV (an increase of 61%). The PH, in combination with +Azos, stimulated the NL in 20%. The sub-division into three VV groups allowed identify the existence of differences among the treatments which were not seen in an independent ANOVA being VV an important variable for the initial growth evaluation in cassava.El trabajo tuvo como objetivo evaluar el efecto de la posición del propágulo de yuca y la aplicación de Azospirillum brasilense en el desarrollo inicial de la plántula. El experimento se realizó siguiendo un diseño completamente aleatorizado, con arreglo factorial (posición del propágulo [horizontal (PH) y vertical (PV)] y A. Brasilense [con (+Azos) y sin (-Azos)]. El porcentaje de brotación (PB) se evaluó de 11 a 35 días después de la siembra (DAP). Luego de 30 DAP, se evaluaron las siguientes variables: número de brotes (NB), altura de brotes (AB), número de folíolos (NF), longitud de folíolos (LF) y vigor vegetal (VV). La posición de las plantas de yuca influyó significativamente en el crecimiento inicial. La PV promueve una mayor brotación, 63% en 17 DAP, sobre la PH que fue del orden de 3% de los brotes visibles en el mismo período. En el trabajo se muestra que la PV promovió los valores más altos combinados con -Azos en las variables AB (aumento de 17%) y VV (aumento de 61%). La PH, en combinación con +Azos, estimuló el NF en 20%. La subdivisión en tres grupos de VV permitió identificar de forma visual diferencias entre tratamientos, que no se observaron en un ANOVA independiente. La VV es una variable importante para la evaluación del desarrollo inicial de la yuca

Physiological response of chickpea (Cicer arietinum L.) in symbiosis with arbuscular mycorrhizal fungi under salinity conditions

Objective: The effect of salinity by NaCl based on physiological variables of chickpea plants was evaluated with the use of native strains of arbuscular mycorrhizal fungi Glomus cubensis and Rizoglomus irregulare during the pre-flowering phenophase. Design/methodology/approach: The research was carried out under controlled environmental conditions, using as an experimental model the chickpea variety N-29, obtained at INIFAT, Cuba. The treatments consist of the combination of three salinity levels: 25, 50 and 75 mM of NaCl and the respective control (Source of variation A) and two strains of AMFs (source of variation B) for a total of 12 treatments with six repetitions. Treatments were distributed under a completely randomized experimental design. The variables evaluated were: number of green and dry leaves, biomass by organs (leaves, stem, root), net assimilation rate (TAN), relative growth rate (TCR) and leaf area ratio (RAF). Results: Green leaves, TAN and leaf and root biomass were the variables with the highest response in the 50 mM NaCl + R. irregulare treatment, with an average increase of 15% compared to the rest of the treatments. Limitations on study/implications: There is a decrease in the variables evaluated due to the salinity effect, however, chickpea plants subjected to 50 mM NaCl inoculated with R. irregulare were less affected by saline stress. Findings/conclusions: It was also found that the R. irregulare strain contributed more than G. cubense to mitigating the adverse effects of the salinity factor.Objective. Evaluate the effect of salinity due to NaCl on physiological variables of chickpea plants using native strains of arbuscular mycorrhizal fungi (AMF) Glomus cubensis and Rhizoglomus irregulare during the pre-flowering stage. Design/methodology/approach. The research was carried out under controlled weather conditions using the chickpea variety N-29 as an experimental model. The treatments consisted on the combination of four salinity levels: 0, 25, 50 and 75 mM NaCl (variation source A) and AMF (variation source B) in three levels. In total there were 12 treatments with six repetitions, which were distributed in a completely randomized experimental design. The evaluated variables were number of green and dry leaves, dry biomass per organ (leaves, root and stem), net assimilation rate (NAR), relative growth rate (RGR) and leaf area ratio (LAR). Results. The green leaves, the NAR and the dry biomass from roots and leaves, were the variables with the greatest response in the 50 mM NaCl + R. irregulare treatment, with an average increase of 15% with respect to the rest of the treatments. Limitations/implications. A decrease on the evaluated variables was observed due to the salinity effect; however, chickpea plants subjected to NaCl 50 mM inoculated with R. irregulare were less affected by salt stress. Findings/conclusions. The R. irregulare strain was found to contribute more than the G. cubensis to the mitigation of the adverse effects from the salinity factor

Satellite measurements of solar radiation in the Yaqui Valley, northern Mexico

Se realizaron estimaciones cada media hora de radiación solar a partir de datos de satélite para el Valle del Yaqui en Sonora, México, para el período de noviembre de 1998 a marzo de 1999. Las estimaciones se hicieron en una malla de 50 km usando el algoritmo de “Global Energy and Water-Cycle Experiment Surface Radiation Budget (GEWEX/SRB)” aplicado con datos de GOES-East y, en una malla de 4 km, usando una versión de alta resolución del mismo algoritmo con datos de GOES-West. Los resultados se compararon con mediciones de terreno en dos sitios. En promedio, usando la actual calibración de los radiómetros de los satélites, los valores derivados de GOES-East son 18% mayores que los medidos en terreno, mientras que los de GOES-West son 9% menores. Asumiendo que estas diferencias sistemáticas reflejan la pobre calibración de los sensores en los satélites, las estimaciones fueron recalibradas por separado para ajustarse a los datos de campo. Después de la recalibración, existen aún diferencias entre las estimaciones y las observaciones porque el satélite da una estimación instantánea promedio de un área, mientras que la observación de campo representa una medición puntual promedio para un cierto intervalo de tiempo. Estas discre- pancias se reducen cuando se comparan valores promedios diarios. El error entre el satélite y las mediciones es menor para la estimación de alta resolución, y existe mejoría en el detalle espacial con los datos de alta resolución, haciéndolos preferibles en aplicaciones hidrológicas. Investigaciones anteriores han demostrado la capacidad para estimar evaporación potencial a partir de radiación solar diaria usando una versión de la ecuación de Makkink calibrada localmente y los factores de cultivo relevantes han sido derivados para trigo y algodón. Finalmente, se demuestra la aplicación de las estimaciones de radiación solar de alta resolu- ción para derivar estimaciones diarias de evapotranspiración en campos de trigo y algodón. doi: https://doi.org/10.22201/igeof.00167169p.2001.40.3.32

Quantifying water stress on wheat using remote sensing in the Yaqui Valley, Sonora, Mexico

Remote sensing can allow a more efficient irrigation water management by applying the water when crops require it or when symptoms of water stress appear. In this study, the spatial and temporal distribution of the water deficit index (WDI) and crop evapotranspiration (ET) in wheat were determined through analysis of satellite-based remote sensing images in the Yaqui Valley, Sonora, México. We utilize an empirical model based on the canopy temperature-vegetation cover relationship methodology known as the Moran's trapezoid. We analyze and discuss the spatial and temporal distributions of WDI and ET at the regional and local scales. Results show a linear relationship (R2 = 0.96) between the values of WDI and the number of days elapsed since the last irrigation. The water deficit index could be utilized to estimate the quantity of available water in wheat and to know the degree of stress presented by the crop. Advantages offered by this methodology include obtaining WDI and evapotranspiration values in zones with partial or null vegetation cover and for large irrigation schemes lacking the necessary data for traditional water management.

Eutrophication and Sedimentation Patterns in Complete Exploitation of Water Resources Scenarios: An Example from Northwestern Semi-arid Mexico

17 páginas, 8 figuras, 2 tablas.Water requirements to supply human needs lead water stakeholders to store more water during surplus periods to fulfil the demand during – not only – scarcity periods. At the reservoirs, mostly those in semi-arid regions, water level then fluctuates extremely between rises and downward during one single year. Besides of water management implications, changes on physical, chemical and biological dynamics of these drawdown and refilling are little known yet. This paper shows the results, throughout a year, on solids, nutrients (N and P), chlorophyll-a, and sedimentation changes on the dynamics, when the former policy was applied in a reservoir from the semi-arid Northwestern Mexico. Water level sinusoidal trend impinged changes on thermal stratification and mixing, modifying nutrient cycling and primary producer responses. According to nitrogen and phosphorus concentration as well as chlorophyll-a, reservoir was mesotrophic, becoming hypertrophic during drawdown. Nutrient concentrations were high (1.22 ± 0.70 and 0.14 ± 0.12 mg P l−1), increasing phosphorus and lowering N:P significantly throughout the study period, although no intensive agricultural, no urban development, neither industrial activities take place in the watershed. This suggests nutrient recycling complex mechanisms, including nutrient release from the sediment–water interface as the main nutrient pathway when shallowness, at the same time as mineralization, increases. Outflows controlled nitrogen and phosphorus availability on the ecosystem while organic matter depended on river inflows. As on other subtropical aquatic ecosystems, nitrogen limited primary productivity (Spearman correlation R = 0.75) but chlorophyll-a seasonal pattern showed an irregular trend, prompting other no-nutrient related limitants. Shallowness induced a homogeneous temporal pattern on water quality. This observed temporal variability was mainly explained statistically by changes on solids (mineral and organic), chlorophyll-a and flows (62.3%). Annual sedimentation rates of total solids ranged from 11.73 to 16.29 kg m−2 year−1 with organic matter comprising around 30%. N:P ratio on sedimentation rates were as high as could be expected in a resuspension dominated ecosystem, and spatially inverse related with N:P ratio on bottom sediments. Distance from river inlet into the reservoir reveals a marked spatial heterogeneity on solid and nitrogen sedimentation, showing the system dependence on river inflows and supporting resuspension as the main phosphorus pathway. Accretion rates (2.19 ± 0.40 cm year−1) were not related to hydrological variability but decreased with the distance to the river input. Total sediment accumulation (9,895 tons km−2 year−1) denotes siltation as other serious environmental problem in reservoirs but possibly not related with operational procedures.This research was supported by CONACYT (contract R-35164-T).Peer reviewe

Evapotranspiration in semi-arid wetlands: relationships between inundation and the macrophyte-cover: open-water ratio

13 pages, and figures, and tables stadistics.Open water evaporation and macrophyte transpiration rates were analyzed in a semi-arid, freshwater wetland in Central Spain over two meteorological periods between 1993 and 1998. The aim was identifying the importance of these variables in the dynamics of evapotranspiration in different water level scenarios. Throughout the vegetation growth period, transpiration versus evaporation ratios were about 2 for cut-sedge, 1 for reed and 0.5 for cattail, but these values declined significantly when calculated on a yearly basis. Open water area to macrophyte cover ratios showed significant dependence on inundation. Increased vegetation cover did not result in a statistically significant reduction of evapotranspiration, but it did increase the transpiration to evaporation ratio. Increased open water area resulted in increased wetland evapotranspiration. The results indicate that Linacre’s theory needs to be modified to take into account emergent macrophyte strategies to flood tolerance and plant physiological traits. The authors provide a conceptual model to explain wetland evapotranspiration dynamics in relation to vegetation cover, physiological strategies and inundationPeer reviewe