R ESU M ENEl objetivo de este trabajo fue analizar la producción de biomasa aérea, la eficiencia del uso de agua y el valor nutritivo de alfalfa cultivada aplicando riego con agua residual urbana, agua de perforación y un testigo (precipitaciones), en el Campus de la Universidad Nacional de Rio Cuarto (Córdoba-Argentina). Los tratamientos de riego tuvieron un efecto positivo sobre la producción de biomasa aérea obteniéndose un 24% más de producción de biomasa que en la situación de secano (precipitaciones). Entre los tratamientos con riego también se manifestaron diferencias estadísticamente significativas. La alfalfa regada con aguas residuales urbana supero en un 19% a la cultivada con agua de perforación. La eficiencia del uso del agua por parte del cultivo se incrementó cuando el riego se realizó con aguas residuales urbanas. Además, se determinó que la alfalfa regada con agua residual, supera los valores nutritivos del cultivo que crece en condiciones sin riego; encontrándose 39% más de proteínas, 14% más de digestibilidad e igual porcentaje de energía metabólica. Se puede concluir que el agua residual urbana representa otra posible fuente de agua, factible de ingresar al suelo y estar a disposición para el cultivo de alfalfa. Palabras-clave: Medicago sativa L, tratamiento de agua, filtros verdes, biomasa, calidad ambientalThe cultivation of alfalfa using artesian well water, urban wastewater and rainfall A B ST R A C T The objective of this study was to analyse the production of alfalfa biomass, the efficiency of water use and the nutritional value of forage, inside an irrigation structure of an experimental facility that uses treated urban wastewater, artesian well water and rainfall, at the campus of the Universidad National de Rio Cuarto (Córdoba-Argentina). The irrigation treatment had a positive effect on the production of biomass of alfalfa. On an average 24% increase in production was observed when compared to dry-land farming. Regarding the quality of the irrigation water, statistical differences in production were observed, the irrigation with urban wastewater produced 19% more than that of well water. The efficiency of the water use by the crop increased when the irrigation was done using urban wastewater. The alfalfa irrigated with wastewater surpasses the nutritional values of the crop in normal field conditions: 39% more proteins, 14% more digestibility and equal percentage of metabolic energy. It is concluded that the urban wastewater represents possible water source for the alfalfa crop.

El presente trabajo tuvo como objetivo evaluar el efecto de la protección de la manta térmica sobre el comportamiento de variables ambientales y el rendimiento de un cultivo de lechuga. Para ello, se sembró durante dos temporadas otoño-invernales un cultivar de lechuga tipo mantecosa (Lactuca sativa var. capitata) en bandejas de germinación de 128 celdas, con posterior trasplante en campo, realizado a los 37 días (ciclo 1) y 49 días (ciclo 2) después de la siembra. Los tratamientos fueron: 1) Cultivo protegido con manta térmica (MT); 2) Testigo no protegido (T) en un diseño experimental en parcelas divididas con tres repeticiones. El marco de plantación utilizado fue de 0,35 m entre hileras y 0,25 m entre plantas. El riego se efectuó mediante un sistema de goteo. Se evaluó el efecto de la manta térmica sobre la trasmisividad de la radiación fotosintéticamente activa (RFA), temperatura y humedad relativa del aire, rendimiento del cultivo, suma térmica en grados.día-1 desde el trasplante hasta la cosecha (ºC.ddt-1). Los resultados mostraron en el tratamiento MT una trasmisividad promedio de la RFA de 0,69 (ciclo 1) y 0,73 Mj.m-2.día-1 (ciclo 2), incremento de la temperatura del aire mínima, media y máxima en 1,1; 2,0 y 3,1 ºC, respectivamente, y de la humedad relativa. El rendimiento en peso fresco (t ha-1) presentó diferencias estadísticas significativas entre los tratamientos, siendo de: 37,7 (MT); 15,5 (T) para el ciclo 1 y 33,8 (MT) y 14,7 (T) para el ciclo 2. La suma térmica fue mayor en el tratamiento con manta térmica. La protección del cultivo permitió una mayor precocidad con mejoras significativas en el rendimiento.

Question: What effects do low-density afforestation with Pinus elliottii have on the site conditions and plant diversity of the mountains of central Argentina? Location: Sierra de Comechingones, central Argentina.Methods: We studied the species richness and diversity and the physical and chemical properties of soils, in both the non-afforested steppe (US) and the understorey of P. elliottii silvopastoral systems (SPS). Measurements were performed on three plots located in US and 18 experimental plots located in SPS, which differ in tree density (150, 250 and 450 trees/ha), pruning (with/without) and position (below -UC -, or outside -BC -, the vertical projection of the tree crown). In each plot, we measured soil variables organic matter (OM), pH, electrical conductivity (EC), moisture content (RH) and relative proportion of coarse fragments; as well as photosynthetically active radiation that reached the ground surface (PAR i ). At the same time, a floristic survey was performed, consisting of 117 sampling plots distributed equally between treatments. Richness, diversity and evenness indices were calculated for each treatment.Then, we carried out a PCA in order to identify the differences in life forms and environmental variables across the treatments.Results: PAR i and pH were statistically significantly higher in US, while EC and RH were statistically significantly higher in SPS. Diversity indices did not differ significantly among the non-afforested steppe (US) and the patches between crowns (BC), but were significantly higher in both these treatments than below the crown (UC).The higher richness in some of the life forms and light availability clearly separated US from UC in the PCA. All the species of interest (endemic, N-fixing, medicinal, fodder) were found in the SPS. Conclusions:Our study indicates that the changes in site variables produced by lowdensity afforestation generate niches for some species and, simultaneously, constitute a barrier to others. However, the fact that diversity indices and the presence of the species of interest showed no differences among the between-crowns patches and the non-afforested steppe, highlights the complex environment-vegetation relationships that take place in this kind of system. Additional supporting information may be found online in the Supporting Information section at the end of the article. APPENDIX S1 List of the vascular plant species surveyed in the study area and sorted by families APPENDIX S2 Photographs of the non-afforested steppe and the silvopastoral systems APPENDIX S3 Characteristics of the Poaceae species and medicinal species that appeared at a higher frequency How to cite this article: Fiandino SI, Plevich JO, Tarico JC, Nuñez C, Rusch V, Gyenge JE. Effects of low-density Pinus elliottii (Slash pine) afforestation on environmental conditions and native plant diversity, in the mountains of central Argentina. Appl Veg Sci. 2018;21:442-450.

This paper aims to identify the spatial and temporal distribution of net aerial primary production (NAPP) of oats and sorghum in silvopastoral systems (SPS) and in a treeless situation (TLS), in Southern Cordoba, Argentina. The silvopastoral systems are composed of three woody cultures (Pinus elliottii, Eucalyptus viminalis and Quercus robur), and two grass species (Avena sativa and Sorghum sudanense). NAPP of Avena sativa and Sorghum sudanense were lower in the silvopastoral systems than in the treeless situation. However, there were also differences in terms of NAPP according to the tree species, and these differences were related to the intensity of competition between trees and grasses. Pinus elliottii and Quercus robur were less competitive than Eucalyptus viminalis, which might be associated with their morphophysiological differences, their differential growth rate and their differences in terms of phenology. Finally, facilitation effects between trees and grasses were also identified under certain conditions.

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