Agriculture Reference
In-Depth Information
the farm production. Meeting crop demand for nutrients through organic matter
supply does not guarantee sufficient supply for crop yield, as the decomposition
of organic matter is a climate-dependent process. On the other hand, organic mat-
ter application in soil stimulates the biological activity, which makes the nutrients
cycle less predictable (Kirchmann et al.
2008
). Therefore, organic farming practices
include rotation with legumes, green manuring, returning uncomposted agricultural
wastes to soil, and crop residues incorporation in the fertilization schemes to pro-
vide, as well, soluble fractions of the essential nutrients. Incorporation of green
manure crops into soil provides considerable amount of soluble nutrients into the
soil system. Organic liquid fertilizers (bloods, extracts, algae and molasses), which
provide easily available nutrients, are largely used to sustain plant needs during the
growth. It is worth mentioning that synthetic mineral fertilizers are not fully water-
soluble (Kirchmann et al.
2008
).
1.4.1
Off Farm Input Reduction by Nutrient Recycling
Agricultural production systems loss nutrients through leaching, runoff, gaseous
emissions, export of plant and animal materials out of the production system. On
the long run, if these lost nutrients are not replaced or put back into the agricultural
system, the system will be depleted (Kirchmann et al.
2008
). Organic farming relies
on practices that enhance nutrient and energy use and minimize environmental pol-
lution, such as crop rotations and crop diversity, integration of livestock, symbiotic
N fixation with legumes, application of organic manure and biological pest control.
These practices aim to optimize the use of local on-farm resources; organic systems
are inherently adapted to site-specific conditions (Müller-Lindenlauf
2009
).
A balanced agroecosystem is able to minimize the use of off-farm inputs in-
creasing its self-sufficiency, improving both its resilience and sustainability, which
underline the importance of on-farm resources recycling (Altieri
2007
). Organic
agriculture claims in recycling principle: nutrients needed for plant growth should
be sustained through internal input recycling, biological process as N fixation and
functional crop rotations. Organic agriculture aims to minimize the use of off-farm
inputs and to establishing as possible a closed farm nutrients cycle (Lampkin
1990
).
Composting practice is fundamental to help the farmers in the nutrients recycling,
improving the resources use efficiency of the internal input matching both goals of
high yield and minimum adverse impact on the environment.
Microorganisms are the driving forces for the organic residues recycling pro-
cesses both during composting and decomposition in soil; they can speed up or slow
down the mineralization process in a response to raw materials characteristics and
controlled conditions, in the composting process. In soil, decomposing organism
are mainly bacteria, fungi and larger organisms such as worms, bugs, nematodes,
etc. In organic farming nutrients required to feed the crops are released through
soil biological activities during the growing season as a function of mineralization
process. Environment, climate and agricultural practices control the background
conditions that affect soil microbial activities. Under specific conditions, this com-
