M. R. Mosquera-Losada

Sewage sludge fertilisation of a silvopastoral system with pines in northwestern Spain

The use of municipal sewage sludge as a fertiliser could be a more adequate means of disposal of this residue than its transport to the dump. The objective of this experiment was to evaluate the effects of different doses of sludge and sowing a mixture of cocksfoot (Dactylis glomerata) and clover (Trifolium repens) on pasture production, botanical composition of the pasture, forage quality, and changes in soil chemical properties. Treatments applied were: (1) no fertilisation (L0), (2) fertilisation with 26 Mg ha−1 of sewage sludge with no sowing (L40), (3) fertilisation with 26 Mg ha−1 of sewage sludge and sowing with 25 kg of Dactylis glomerata L. cv Artabro (Dg) and 3 kg Trifolium repens cv Huia per hectare and (4) 52 Mg ha−1 of sewage sludge with no herbage sowing (L80). Plots were established in a silvopastoral system with Pinus radiata D. Don at a density of 1666 trees ha−1 (3 × 2 m). The improvement of soil fertility due to organic fertiliser application and the use of Dactylis glomerata increased the production and quality of pasture as well as reduced the risk of fire and erosion, as grasses dominated shrubs. Fertilisation with sewage sludge in soils of acid origin increased the concentration of copper in the pasture and, if cocksfoot was not sown, the levels of this element exceeded the maximum tolerable dietary levels for sheep. On the other hand, fertilisation also increased the levels of zinc in pasture, but values were not above toxic limits for sheep, horses and cattle.

Agronomic characterisation of different types of sewage sludge: Policy implications

Spain is one of the main municipal sewage sludge producers of Europe. This paper aims to agronomically characterise different types of sewage sludge stabilised by different methods (anaerobically digested, composted, and pelletised) and deliver policy recommendations from the results of this characterisation. Anaerobic sewage sludge quality is found to be better in plants with a lower volume of water processing. Composted sludge shows the best quality from a heavy metal point of view, but its low available nitrogen content increases the input of heavy metals when spread, as compared to digested or pelletised sludge. Pelletised sludge has higher heavy metal content than anaerobically digested sludge. Despite the good quality of the sludges, future regulations, especially with regard to Cd levels, will limit the use of this waste in agriculture.

Definitions and Components of Agroforestry Practices in Europe

Agroforestry systems are traditional land use systems that were and are used in Europe. They can be defined as those land use systems which involve two main components — trees/shrubs and an agricultural crop (which could also be pasture) and are artificially managed. Agroforestry systems can be implemented at a temporal and spatial scale for a land owner, who can use different agrofor-estry practices. Since human interaction with the environment in Europe is very important and has occurred for a long time there are different types of agroforestry practices in Europe that are described in this chapter and named, silvoarable, forest farming, riparian buffer strips, silvopasture, improved fallow and multipurpose trees. A brief description of the main agroforestry practice components, i.e. trees and agriculture (including pasture and livestock) in Europe will give an overview of the current and potential situation in Europe for the use of these systems.

Classifications and Functions of Agroforestry Systems in Europe

Agroforestry systems have often been neglected in Europe because administrative structures within many national governments have considered that only agriculture or forestry are legitimate within their remit. This has resulted in the loss of agroforestry systems in European countries and an impoverishment of the benefits that they provide. This paper argues that agroforestry systems are a complex interaction of agricultural and forestry elements which can be classified according to their components, spatial and temporal arrangement, agro-ecological zone, and socio-economic aspects. A further breakdown can be made on the basis of ecosystem functions, and their associated goods and services. The ecosystem functions of agroforestry systems can be grouped under production (the creation of biomass), habitat (the delivery of biodiversity), regulation (maintenance of essential processes and life support systems) and culture (cultural heritage, landscape enhancement and recreation). The importance of the multi-functionality of agroforestry systems in terms of their management input and the range of their outputs is stressed and it is proposed that land use decisions should be made within the broader ecosystems perspective so that greater social well-being can be derived from rural areas in Europe.

Tree regeneration and sapling damage of pedunculate oak Quercus robur in a grazed forest in Galicia, NW Spain : a comparison of continuous and rotational grazing systems

Forest grazing has been recognised as being a useful tool in fire-risk reduction, in addition to having the potential to preserve or enhance forest biodiversity if managed correctly. Concern for natural regeneration of forest trees in Europe has also prompted interest in the effects of large herbivores on seedling and sapling growth and mortality. An investigation was carried out into sapling damage and density of natural regeneration of oak (Quercus robur) in a mature, pony-grazed, Pinus radiata forest in Galicia, NW Spain under two different grazing regimes (continuous and rotational). In all treatments significantly more oak seedlings and saplings were recorded in areas of grass sward than areas dominated by taller ground flora species. Damage to oak saplings was assessed from the form (height and canopy) relative to stem diameter. The height and average canopy diameter of similar-aged saplings were found to be significantly greater in ungrazed (control) than both continuous and rotationally grazed treatments. Height and canopy diameters of similar-aged oak were not significantly different between the two grazing treatments. Significant differences were observed in tree form, with unbrowsed saplings having the greatest height to canopy width ratio and those in the continuously browsed plots having the smallest. An obvious decrease in the goodness of fit (R2) of regression analyses were found in continuously grazed areas compared to rotational and control plots for both height and canopy data. The differences in damage observed were not significantly different enough to suggest one method of grazing over the other as being better for minimising sapling damage. Management requirements are more likely to dictate grazing regime. Overall, stock density is likely to have a more significant effect on damage than stocking system.

Carbon Sequestration in European Agroforestry Systems

Agroforestry systems (AFS) are recommended for Europe through the European Rural Development Council regulation 1698/2005, in recognition of their role in reducing carbon (C) emissions and promoting C sequestration which would help to fulfil the Kyoto Protocol requirements. These systems have been found to be a good tool to reduce fire risk and C release in southern European countries. The implementation of AFS could also reduce C release to atmosphere because of the value given to non-timber products, thereby reducing chances for clear cutting of trees. Furthermore, the tree component in AFS will add C into the soil through litterfall and root decomposition, which takes place at deeper soil layers than under agronomic crops or pasture. Tree management practices such as regulating tree density and planting arrangement will influence the C sequestered in the system. Compared with the tree components, the understory components of AFS have less impact on the total C sequestration. The higher inputs of residues generated by the trees in AFS than in tree-less systems may cause high soil C sequestration potential, but soil C increase depends on the incorporation and mineralization of C in the soil, which are affected by understory crop management practices.

Past, Present and Future of Agroforestry Systems in Europe

Many traditional land-use systems in Europe involved agroforestry in the pre-industrial era, but, over the years, increased mechanization led to the development of increasingly specialized crop, animal and wood production systems. As a consequence, the area under agroforestry declined in many regions of Europe, and agroforestry systems became confined to situations where understorey primary production is restricted due to cold temperatures (Boreal and Alpine areas) or drought (Mediterranean areas) and to plots that are hard to reach or too small for cultivation with modern machinery, as in Spain, Italy and the lower altitude mountain regions in southern and central Germany. On the whole, agroforestry continued to be practised only where it enabled farmers to obtain economic returns from lands that were otherwise relatively unproductive and mostly limited to silvopastoral practices. Since the mid-1990s, however, European policies have encouraged land management systems that combine production, environmental services (biodiversity, carbon sequestration, nutrient cycling and water quality) and social benefits, and this has created a new interest in agroforestry systems. Today, the major agroforestry practices in Europe include silvopasture and silvoarable. However, the benefits and opportunities offered by agroforestry can only be realized with substantial investments and coordinated efforts in research, education, knowledge transfer and appropriate national policies across Europe.

Effects of dose and period of sewage sludge application on soil, tree and pasture components in a Pinus radiata D. Don silvopastoral system

The adequate use of sewage sludge in silvopastoral systems could enhance positive relationships between pasture and trees to increase farm incomes at medium, short and long term. The main aspects related to adequate sewage sludge use as a fertiliser are dose and timing of application, once heavy metal concentrations have been taken into account. This paper aims to evaluate the date and dose of sewage sludge applications on soil (KCl pH, soil organic matter), pasture production and tree growth after the establishment of a silvopastoral system with Pinus radiata D. Don developed on sandy soils with an initial pH of 5. It is concluded that the contribution of sewage sludge does not modify the soil conditions in a consistent manner, but cause detectable edaphic improvements depending on the climatic conditions, the results of which are manifested in enhancement of pasture and trees. The application of high doses of sewage sludge is the best option within those studied, as tree growth and pasture production tend to be increased. There are no clear effects with regard to the date of application, but if the desire is to increase pasture production during the spring season, the sewage sludge will be applied in the first of the application dates, whereas the greatest growth in the diameter of trees is produced in the plots fertilised in February, although the date of application does not appear to have a clear effect on their growth in height.

Fertilization with nitrogen and potassium on pastures in temperate areas

Abstract Fertilizer application enable producers to influence pasture production. The effect of N fertilization on grass production and leguminous plant content of pasture and strategic N application has received much attention. Changing agricultural policies suggest that chemical fertilizer inputs may be diminished and that alternative sources of nutrients are desired. The aim of this study was to evaluate the effect of N and K fertilization on production, botanical composition, and forage mineral composition to gain some insight into what influence changing fertilization practices would have on pasture productivity. Three K and 3 N application rates were applied in a factorial design on a white clover (Trifolium repens L.)—perennial ryegrass (Lolium perenne L.) sward. Potassium and nitrogen application increased herbage production and had differential influences on botanical composition. Nitrogen decreased clover content in the pasture, whereas K increased the proportion and production of white clover. The effects of K application appeared later in the experiment than those associated with N. We concluded that K is very important for development and maintenance of white clover in pasture, which increases herbage and protein production. Nitrogen was associated with lesser amounts of N, P, K, and Mg in pasture, because of lesser amounts of clover in the sward. Changing fertilization practices will have definite influences on sward composition and pasture productivity. Any interpretation of pasture mineral content should take botanical composition changes into account.

Horse grazing systems: understory biomass and plant biodiversity of a Pinus radiata stand

Horse grazing systems may affect productivity and biodiversity of understory developed under Pinus radiata D. Don silvopastoral systems, while acting as a tool to reduce the risk of fire. This study compared continuous and rotational grazing systems effect upon biomass, fractions of stem, sprouts, leaves and woody parts of Ulex europaeus L. and alpha (Species Richness, Shannon-Wiener) and beta (Jaccard and Magurran) biodiversity for a period of four years in a P. radiata silvopastoral system. The experiment consisted of a randomized block design of two treatments (continuous and rotational grazing). Biomass, and species abundances were measured - biodiversity metrics were calculated based on these results for a two years of grazing and two years of post-grazing periods. Both continuous and rotational grazing systems were useful tools for reducing biomass and, therefore, fire risk. The rotational grazing system caused damage to the U. europaeus shrub, limiting its recovery once grazing was stopped. However, the more intensive grazing of U. europaeus plants under rotational had a positive effect on both alpha and beta biodiversity indexes due to the low capacity of food selection in the whole plot rather than continuous grazing systems. Biomass was not affected by the grazing system; however the rotational grazing system is more appropriate to reduce U. europaeus biomass and therefore forest fire risk at a long term and to enhance pasture biodiversity than the continuous grazing system.