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Monitoring crops
Limiting factors for yield
Monitoring crops with a water balance calculation is possible as long as water is a limiting factor for the crop. In circumstances where water is not a limiting factor in any way, water balance output will not be strongly correlated to yields obtained. Limiting factors for crop growth can be grouped into four groups:
- Weather dependent, such temperature, solar raddiation, rainfall and CO2 content of the air.
- Crop dependent, such as genetic potential and crop canopy (LAI)
- Related to Pests and diseases (insects, weeds etc..)
- Related to cultivation techniques (irrigation, fertilizer etc..)
Basically, water balance calculations have predictive value for yield in arid and semi-arid areas. In areas where temperatures are high and water is not limited, solar radiation is loosely correlated to yields. In areas of abundant water and high solar radiation during the growing season, temperatures are often more limiting than other factors (e.g. Northern pats of Russia and Canada)
Development Stages
Clarence Sakamoto
At each stage of their development, from germination through to the formation of seeds, plants come under the influence of their environment and show external modifications (appearance of leaves, formation of inflorescence, etc.). These external modifications of the plants correspond to the different phases of their development. Each phase shows up in a different way. In the same cultivated field, plants do not reach the following stages of development simultaneously, it can take several days. On the other hand, certain stage of development are reached very quickly. Here again, in the same cultivated field, a particular stage of development will not be reached at the same time by the totality of the plants. In general, the start of a development stage will be the day when 10 % of the plants have reached that stage. The development stage will be reached when 50 % of the plants are showing the characteristics of the phase.