Integrated Models in Hydrology and Meteorology - Transport in the Atmosphere-Vegetation-Soil Continuum - page 320

defining factors

defining factors defining factors

• CO 2
• radiation
• temperature
• crop characteristics
� physiology, phenology
� canopy architecture

+ +

limiting factors limiting factors

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• water shortage
• oxygen shortage
• salinity excess
• nutrient shortage

reducing factors

• weeds
• pests
• diseases
• pollutants

Potential Actual

Figure 9.9 A hierarchy of growth factors, production situations and associated
production levels (Van Ittersum et al., 2003 ).

9.1.8 Crop Growth
Three groups of growth factors ( Figure 9.9 ) may be distinguished to obtain a hierar-
chy of production levels in crop production. Growth-deining factors determine the
potential production that can be achieved in a given physical environment for a spe-
ciic plant species. The main growth deining factors are radiation intensity, carbon
dioxide concentration, temperature and crop characteristics. Their management, at
least in open ields, is only possible through tactical decisions such as sowing date,
sowing density and breeding. To achieve the potential production the crop must be
optimally supplied with water and nutrients and fully protected against weeds, pests,
diseases and other factors that may reduce growth.
Growth-limiting factors comprise shortage of water, oxygen and nutrients and
excess of salts. Combined with the crop and climate characteristics, these factors
determine a theoretical production level for a plant species in a given physical envi-
ronment. Here, management can be used to control availability of water, oxygen,
nutrients and salts, and may increase production towards potential levels.
Growth-reducing factors hamper growth further and comprise biotic factors such
as weeds, pests and diseases, and abiotic factors such as pollutants and aluminium
toxicity. Crop protection aims to limit the inluence of these growth-reducing factors.