RESUMEN
A 3-year experiment compared in an olive orchard the effect of different cover crops' composition on runoff, water erosion, diversity of annual plants, and arthropod communities which could provide an alternative to conventional management based on tillage (CT). The cover crops evaluated were a seeded homogeneous grass (GC), a seeded mix of ten different species (MCseeded), and a non-seeded cover by vegetation naturally present at the farm after 20 years of mowing (MCnatural). The results suggest that heterogeneous cover crops can provide a viable alternative to homogeneous ones in olives, providing similar benefits in reducing runoff and soil losses compared to management based on bare soil. The reduction in soil loss was particularly large: 46.7 in CT to 6.5 and 7.9 t ha-1 year-1 in GC and MCseeded, respectively. The heterogeneous cover crops resulted in greater diversity of plant species and a modification of the arthropod communities with an increased number of predators for pests. The reduction of the cost of implanting heterogeneous cover crops, improvement of the seeding techniques, and selection of species included in the mixes require additional research to promote the use of this practice which can deliver enhanced environmental benefits.
Asunto(s)
Biodiversidad , Productos Agrícolas/crecimiento & desarrollo , Olea/crecimiento & desarrollo , Suelo/química , Animales , Artrópodos , Ambiente , Plantas , Estaciones del Año , EspañaRESUMEN
Occurrences of surface water contamination by herbicides in areas where olive orchards are established reveal a need to understand soil processes affecting herbicide fate at field scale for this popular Mediterranean crop. A monitoring study with two herbicides (terbuthylazine and oxyfluorfen) in the first 2cm of soil, runoff waters, and sediments, was carried out after under natural rainfall conditions following winter herbicide application. At the end of the 107day field experiment, no residues of the soil applied terbuthylazine were recovered, whereas 42% of the oxyfluorfen applied remained in the top soil. Very low levels of both herbicides were measured in runoff waters; however, concentrations were slightly higher for terbuthylazine (0.53% of applied) than for oxyfluorfen (0.03% of applied), relating to their respective water solubilities. Congruent with soil residue data, 38.15% of the applied oxyfluorfen was found in runoff-sediment, compared to only 0.46% for terbuthylazine. Accordingly, the herbicide soil distribution coefficients measured within runoff field tanks was much greater for oxyfluorfen (Kd=3098) than for terbuthylazine (Kd=1.57). The herbicide oxyfluorfen is co-transported with sediment in runoff, remaining trapped and/or adsorbed to soil particle aggregates, due in part to its low water solubility. In contrast, terbuthylazine soil dissipation may be associated more so with leaching processes, favored by its high water solubility, low sorption, and slow degradation. By comparing these two herbicides, our results reaffirm the importance of herbicide physico-chemical properties in dictating their behavior in soil and also suggest that herbicides with low solubility, as seen in the case oxyfluorfen, remain susceptible to offsite transport associated with sediments.
Asunto(s)
Sedimentos Geológicos/análisis , Éteres Difenilos Halogenados/análisis , Herbicidas/análisis , Contaminantes del Suelo/análisis , Triazinas/análisis , Contaminantes Químicos del Agua/análisis , Agricultura , Olea/crecimiento & desarrollo , EspañaRESUMEN
Un estudio de faringitis en veintitrés pacientes asmáticos reveló que las principales bacterias involucradas fueron: Staphyulococcus aureus, Haemophilus influenzae y Streptococcus pneumoniae como posibles patógenos capaces de iniciar o complicar un proceso que primeramente puede ser viral, y así descencadenar una crisis de asma. También se comparó el hallazgo de esas bacterias en un grupo de ciento cinco sujetos no asmáticos con faringoamigdalitis, y los porcentajes de aislamiento de S. aureus y Haemophilus resultaron ser más altos en asmáticos: 71.4 por ciento y 57.1 por ciento respectivamente, del total de dichos microorganismos. S. pneumoniae se aisló sólo en tres casos de asma. Según la especie o especies de bacterias encontradas y sus pruebas de sensibilidad, se siguieron las pautas para un tratamiento con antibióticos, lográndose un 68 por ciento de mejoría clínica, con disminución de la magnitud y frecuencia de la crisis en los asmáticos y una reducción de la intensidad o violencia de las I.V.R.S. en los no asmáticos.