requires substantially more farmland than the con-
ventional one (Cederberg and Mattsson, 2000; Fos-
teret all., 2006).
On the other hand, organic agriculture has a signif-
icant ability to sequester large amounts of atmos-
pheric carbon into the soil (Hepperly et all., 2007),
thus contributing to counteracting greenhouse
gases. Therefore, carbon sequestration of organic
farming is crucial in assessing the environmental
impact (Niggli et all., 2008).
Leaching of nutrients, nitrogen in particular, is re-
sponsible for much of the environmental damage
caused to many ecosystems by intensive agriculture
(Hansen et all., 2001). In organic production only or-
ganic fertilizers can be used to supply the soil with
nitrogen. From the scientific literature, the nitrogen
leaching in organic farming results lower than that
occurring in conventional agriculture (Knudsenet
all., 2006; Hansenet all., 2001). However, nitrogen
leaching depends not only on the type of fertilizer
used, but also on the management practices (Knud-
senet all., 2006). In fact, the mineralization of or-
ganic fertilizers is slow and problems with the
supply of nitrogen can occur, particularly when the
demands of the plants are high (Kelderer et al.,
2008).
The lower yields generally observed in the organic
crop production are ascribed to the limited avail-
ability of nitrogen in the organic systems (Doltraet al.,
2011). By an efficient and careful management of
the nutrient supply to the plants, it is possible to
counterbalance the negative effects on the yields
(Doltraet all., 2011; Crews and Peoples, 2004;
Hansenet all., 2001; Pang and Letey, 2000). Mader
et all. (2002) reported a reduction of only 20 percent
of the yield of grain crops in organic systems, al-
though the fertilizer input was reduced by 34–53
percent. Pimentelet all. (2005) reported yields in
organic maize and soybean comparable to those of
conventional production, suggesting that organic
crop production can be competitive with conven-
tional faming.Organic farming and biodiversity
Agricultural biodiversity (agrobiodiversity) is funda-
mental to agricultural production, food security and
environment conservation. Agrobiodiversity, in fact, in-
cludes a wide variety of species and genetic resources
and also the ways in which the farmers can exploit
them to produce and manage crops, land, water, in-
sects and biota (Thrupp, 2000). Agricultural biodiver-
sity, moreover, provides ecosystem services on farm,
such as pollination, fertility enhancement, insect and
disease management. Over the last 40 years the
model and patterns of industrial agriculture have
caused serious degradation of natural resources and,
in particular, biodiversity: loss of plant genetic re-
sources, livestock, insect and soil organisms. The ero-
sion of biodiversity is manifested both within farming
systems and off farms, in natural habitats.
A principal objective of organic farming is to main-
tain, to enhance the natural fertility of the soil. Or-
ganic farming systems which involve the use of catch
crops, the recycling of crop residues, the use of or-
ganic fertilizers and perennial crops, are assumed to
promote higher levels of organic matter and biologi-
cal activity in the soil (number and variety of soil or-
ganisms). Microorganisms, like bacteria or fungi,
play a central role in maintaining the fertility of the
soil through the decomposition of organic matter.
Several studies have demonstrated an increase in the
biodiversity, biological activity and fertility in the soil
managed by organic systems (Bengtsson et all., 2005;
Pimentelet all., 2005; Mader et all., 2002). Moreover,
in organic farms it has been observed a higher diver-
sity and abundance of birds, pollinator, insect and
herbaceous plants (Holzschuh et all., 2008; Rundlöf
et all., 2008a; Rundlöf et all., 2008b; Holzschuh et al.,
2 007) than in conventional ones.
However, Gabrielet all. (2010) have demonstrated
that within a farm biodiversity is influenced by both
management within the farm and management of
surrounding farms, thus highlighting the crucial
role of the landscape. Belfrage et all. (2005) com-
pared diversity and abundance of birds, butterflies,256