Agriculture Reference
In-Depth Information
[48]. The average daily solar irradiation varies; depend on latitude, climate and season. When
on the equator, maximum solar irradiation is on a horizontal plane, but away from the
equator, for the maximum intercept of solar radiation by a fixed plane, the plane should have
angle corresponding latitude [49]. Average daily solar irradiation that may support feedstock
for biofuel production varies roughly between 7 and 25 MJ m
-2
. The daily worldwide average
irradiation is about 15.5 MJ m
-2
, or 180 Wm
-2
. Differences between days can be large [50].
The greatest annual input of solar radiation tends to occur in subtropical regions at latitudes
between 20° and 30° and little could cover. Humid tropical regions have somewhat lower
irradiation. When going pole-ward from latitude of about 30°, solar irradiation tends to
decrease. The relative importance of individual weather variables depends on the
development stage of the plant and is also site specific. The early growth of sugar beet in
Central Europe was found to be strongly influenced by temperature [51] and in England the
crop growth rate was proportional to absorbed solar radiation [52].
Temperature
Temperature is an important climatic factor which can have profound effects on the yield
of crops. Changes in seasonal temperature affect the grain yield, mainly though phonological
development processes. Winter crops are especially vulnerable to high temperature during
reproductive stages and differential response to temperature change to various crops has been
noticed under different production environments [53].
Water
Unlike temperature and radiation, the water supply to plants is not affected by weather
conditions alone, but is a function of rainfall and temperature together with evaporative
demand and the water holding capacity of the soil [54-56]. Of the four soil physical factors
that affect plant growth e.g., mechanical impedance, water, aeration, temperature, water is the
most significant. Soil moisture plays an important role in plant productivity by controlling
transpiration between soil, plant and atmosphere. Several studies in various geographical
regions [33, 57] have demonstrated that soil moisture is often one of the main stress factors
for vegetation and crop yield. In most parts of the world, crop production depends on rainfall.
However, not all rainfall is effectively used in crop growth, as some is lost by runoff,
infiltration and evaporation. Heavy and high intensity rainfalls are lost most from soils
because of losses from surface run off or to groundwater. Among other factors, the
effectiveness of rainfall is strongly influenced by topography, which determines the
redistribution of summer precipitation as runoff [58].
Water consumption for the production and processing of bioethanol is not negligible. The
amount of water used for agriculture depends on the aridity of the cultivated region and on the
water demand of the feedstock type. But also for the conversion process much water is
needed [19]. Bio energy crops optimized for rapid growth generally consume more water than
natural flora or many food crops. Certain practices, like harvesting residues, cultivating tree
crops without undergrowth, and planting species that do not generate adequate amounts or
types of litter, can reduce the ability of rainfall to infiltrate the soil and replenish groundwater
supplies, enhancing problems of water overconsumption [59].
Agricultural water use is a serious concern, especially in southern parts of Europe, where
water is scarce and highly variable from year to year and where agricultural use of total water
consumption exceeds 50 %.
