Weed control is fundamental in plantations of valuable broadleaved species. The most common weeding techniques are repeatedly applied herbicides and removable plastic mulching, both raising environmental concerns. We studied the performance of these techniques on a hybrid walnut plantation, compared with three biodegradable mulch alternatives: a prototype bioplastic film, a layer of composted woodchips and a layer of ramial chips. The durability and effect of the treatments on tree performance (survival, growth, physiological traits) and soil features (moisture and temperature) were evaluated over 4 years. Herbicide yielded the best results, while all the mulching treatments provided better results than controls for nearly all the variables. The performance of plastic and bioplastic films was similar, suggesting that the latter could replace plastic mulching. The performance of the two chip mulches was similar and slightly below that of the films, probably because of the excessive thickness of the former (13–14 cm). In summary, biodegradable mulches showed high effectiveness in controlling weeds and so could offer an alternative to herbicide application and plastic mulching when these are contra-indicated technically (accessibility, repeatability), economically (labour cost), legally or environmentally.

Aim of study: To assess the effectiveness for improving early seedling performance of the individual and combined application of (i) various doses of an innovative soil conditioner including polyacrylamide-free super-absorbent polymers, fertilizers, root precursors and humic acids; and (ii) innovative mulches based on renewable-biodegradable or recycled raw materials. The assessment was carried out in comparison with reference (commercial) soil conditioners and mulches.Area of study: Upper montane afforestation site located at 1,430 m altitude in the southern Pyrenees (NE Spain).Material and methods: We studied the effect of 15 treatments (various combinations of soil conditioners and mulches) on mountain ash (Fraxinus excelsior L.), testing survival, diameter and height growth and water and nutrient status during two growing seasons (2014-2015). We also assessed mulch durability during 2014-2016.Main results: The innovative soil conditioner improved diameter and height seedling growth (92% and 72% respectively) and water and nutrient status. The 40 g/seedling dosage was more cost-effective than the 20 and 80 g/seedling doses. The new formulation performed better in general than the commercial formulation. Mulches led to slight gains compared to control seedlings, and there were no major differences between the mulch models. The combined application of soil conditioners and mulches was not of particular interest.Research highlights: Soil conditioners consisting of synergic mixtures of water super-absorbent polymers, fertilizers, root growth precursors and humic acids can improve early seedling performance in coarse-textured, stony soils in montane conditions. Small mulches may be only of limited interest as long as weed competitiveness is poor.Keywords: ecotechnology; groundcovers; reforestation; seedling performance; restoration; water super-absorbent polymer; weed.Abbreviations used: GSn, growing season number ‘n’; leaf water potential, LWP; water super-absorbent polymers, SAP; soil conditioner with water super-absorbent polymers, SCwSAP; Soil Plant Analysis Development, SPAD.

The presence of woody vegetation in the interior and on the margins of agricultural lands was relatively common in Spain until the development of the mechanization of agricultural tasks from the middle of the 20th century. The process of simplifying ecosystems in agricultural environments and the effective separation of forest areas and agricultural areas continued during the following decades, marked by a policy focused on maximizing the surface area of the cultivated areas. However, in recent years the productive and environmental interest (ecosystem services) of recovering the woody component in the environment of cultivated land has been confirmed, without compromising the mechanization of agricultural management and avoiding or mitigating a large part of the problems linked to monocultures. At European level, and particularly in France, there is a growing number of experiences that allow to know the conditions and advantages of the combined systems of forestry and agricultural production (compared to annual crops), known as silvoarables systems. In Spain, these systems have been used traditionally in the dehesa, but they are very scarce in other areas, due to ignorance and lack of specific support policies. The incipient silvoarables experiences installed in recent years have the hardwood producing quality wood as the most common forestry component. This paper presents a summary of the main silvoarables experiences made in our country, as well as some opportunities for its promotion. La presencia de vegetación leñosa en el interior y en los márgenes de terrenos agrícolas era relativamente común en España hasta el desarrollo de la mecanización de las tareas agrícolas a partir de mediados del siglo XX. El proceso de simplificación de los ecosistemas en entornos agrícolas y la separación efectiva de zonas forestales y zonas agrícolas continuó durante las siguientes décadas, marcadas por una política enfocada a maximizar la superficie de los terrenos de cultivo. Sin embargo, en los últimos años se está constatando el interés productivo y ambiental (servicios ecosistémicos) de recuperar el componente leñoso en el entorno de terrenos de cultivo, sin comprometer la mecanización de la gestión agrícola y evitando o mitigando gran parte de los problemas vinculados a los monocultivos. A nivel europeo, y particularmente en Francia, existe un creciente número de experiencias que permiten conocer los condicionantes y ventajas de los sistemas combinados de producción forestal y agrícola, conocidos como sistemas silvoarables. En España, estos sistemas se han empleado de forma tradicional en la dehesa, pero son muy escasos en otras zonas, debido al desconocimiento y a la falta de políticas específicas de apoyo. Las incipientes experiencias silvoarables instaladas en los últimos años tienen como componente forestal más habitual las frondosas productoras de madera de calidad. Se presenta en este trabajo un resumen de las principales experiencias silvoarables realizadas en nuestro país, así como algunas oportunidades para su fomento.

In light of the significant impact of climate change, it is imperative to identify effective solutions to promote afforestation and reforestation operations, which are often constrained by a low survival rate. To mitigate the impact of weed competition and enhance water availability, biodegradable groundcovers comprising xanthan gum and gelatine were developed and evaluated over the course of the growing season in a nursery setting on narrow-leaved ash (Fraxinus angustifolia) and alder (Alnus glutinosa) in 3.5 L pots. The results demonstrated a beneficial impact of all groundcovers, particularly the gelatine-based ones, on both the aboveground and belowground growth rates. The efficacy of weed competition was controlled using gelatine-based groundcovers in the case of ash trees. Furthermore, the gelatine-based groundcover altered the soil physiochemical characteristics and affected the bacterial community while maintaining its role in increasing the soil nitrogen pool. In contrast, the xanthan gum-based groundcover was demonstrated to enhance microbial richness and diversity, with an augmented contribution to the soil nitrogen pool. However, further trials with diverse tree species and soil conditions are necessary to gain a more comprehensive understanding of these effects.