• Energy Research

AbstractAmendment of forest soils with dewatered dairy factory sludge (DDFS), characterized by low heavy metal contents and high amounts of degradable C, can prevent the depletion of soil nutrients that results from intensive harvesting in forest plantations. However, this practice involves environmental risks when N supplies exceed the demand of plants or when the strong acidity of the soil favors the mobility of trace metals. These aspects were assessed in a young radiata pine plantation growing in a sandy, acidic, and organic N‐rich soil for the 7 yr after application of a DDFS. The supply of limiting nutrients (mainly P, Mg, and Ca) provided by application of the DDFS, along with control of the ground vegetation, improved the nutritional status of the stand and led to increases in timber volume of more than 60 to 100%. Increases in soil inorganic N were observed during the first months after amendment. Data from soil incubation experiments revealed that some of the additional N was immobilized and, to a lesser extent, denitrified due to the readily available organic C content of the DDFS. Leaching and increased plant uptake of N were prevented by a combination of the latter processes and the low rate of nitrification. The strong acidity of the soil enhanced the availability of Mn and Zn to plants, although the maximum concentrations did not reach levels harmful to organisms. We conclude that although application of DDFS has positive effects on tree nutrition and growth and the environmental risks are low, repeated application may favor mobility of N and availability of heavy metals.

Agroforestry is considered a sustainable form of land management that optimizes the use of natural resources (nutrients, radiation, water). Agroforestry is defined as the deliberate integration of woody vegetation with agricultural activities in the lower story. It provides a higher biomass production per unit of land, while providing more ecosystem services than woody-less agricultural lands, such as the reduction of soil erosion and nitrogen leaching, and increase carbon sequestration and landscape biodiversity. The objective of this paper is to evaluate the past and current European Union Common Agricultural policies aiming at promoting the afforestation or reforestation of lands, as the introduction of trees can be seen as a first step to carry out agroforestry practices in former agricultural or forest lands. Agroforestry was a traditional land use system in Europe before modern times. However, before the sixties land intensification and consolidation destroyed millions of trees all over Europe. On the contrary, some good examples of agroforestry promotion are found in Eastern European countries in order to reduce the effect of extreme events such as winds, flooding at the beginning and mid of the last century. In Western European countries, the introduction of trees in the land has been promoted by agroforestry, afforestation and reforestation at the end of the last century. Afforestation of agricultural lands have been the most successful CAP measure (over 1 million hectares) while agroforestry measures were not extensively adopted which may be explained by the funds associated to afforestation measure which compensated the losses of income 15 or 20 years in afforested lands. Agroforestry was poorly adopted in the CAP 2007-2013, having a better success in the CAP 2014-2020 due to the recognition of woody vegetation and the compensation of 5 years given for maintenance once agroforestry is established. However, policy rules ensuring Pillar I payment when agroforestry measure is adopted such as a management plans ensuring that maximum tree density (100 trees per hectare) is not reached, should be pursued.