Agriculture Reference
In-Depth Information
NO 3 !
NO 2
NO
!
N 2 O
!
N 2 :
ð
11
:
4
Þ
The production of these gases is an important factor, considering the effect that they
can have on atmospheric chemistry, effectively contributing to the greenhouse
effect and ozone depletion (Snyder et al. 2009 ; Serrano-Silva et al. 2011 ). The
atmospheric N 2 O concentration is substantially lower than that of CO 2 ; however,
the impact on the global warming on a mass base shall be 298 times higher than
CO 2 , prospecting for 100 years. The effective contribution of each substance to
global warming must be balanced by the molecular weight, the mean residence time
in the atmosphere, and the cumulative heating effect of each gas (USEPA 2011 ).
Moreover, it is expected that N 2 O emissions from agriculture, on a global basis,
could increase by 35-60 % by 2030 (FAO 2003 ; IPCC 2007 ), considering the need
for agricultural production to supply the growing global population demand. Thus,
it is necessary to control the presence of nutrients in soil in order to minimize the
environmental and economic damages caused by inappropriate use of fertilizers.
However, this is not a simple challenge because not only nitrogen but also losses of
other nutrients from agricultural sources mainly vary with the type of soil and
climate, parameters that are beyond the control of any farmer (Cavigelli 2005 ).
Many strategies can be developed to enhance the use of nutrients in fertilizer, as
well as to maximize their benefits to the soil-plant-atmosphere system. The
concept of efficient use of fertilizer is the one that reflects the increase in production
per unit of applied nutrient, whereas in contrast, the low efficiency means low
productivity and low profits (Lopes and Guilherme 2000 ). In general, some changes
in management can increase the efficiency in the use of nitrogen fertilizers, for
instance, proper incorporation into the soil; split fertilization; controlled irrigation;
adjustment of fertilizer based on tracking the nitrogen content in plant tissues;
removal of factors that limit plant growth, such as grass weeds, which cause
damage and competition, and pests; limitation of other nutrients; use of cover
crops to fix the residual nitrogen in soil during postharvest periods; use of improved
technologies in work with farmers; and finally optimization of application rate and
timing of fertilizer, using specific forms of nitrogen compounds in individual cases
to reduce losses (slow- or controlled-release fertilizers and nitrification inhibitors)
(Lopes and Guilherme 2000 ; Cavigelli 2005 ; Ni et al. 2011 ). In relation to the use of
materials for slow or controlled release, considerable scientific efforts have been
made to develop new materials capable of increasing the efficiency of nitrogen
fertilizers, especially for urea. This has been done through, for example, coating
urea granules with polymers (Gagnon et al. 2012 ) or sulfur (Costa do Nascimento
et al. 2013 ), use of urease inhibitors (Singh et al. 2013 ), etc. However, these
products have a limited use due to the additional costs incurred in the manufactur-
ing process, resulting in an increase of the final product cost and, consequently, the
cost of production.
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