week 4 Flashcards
What is water holding capacity? (WHC)
= How much water soil is capable of holding;
also referred to as field capacity
By which soil caracteritics is influenced WHC?
Soil texture and organic matter
What is the critical point?
Point of minimum readily available water in soil; below this point plant suffers irreversible water stress and its yield is reduced
optimum range of soil moisture,
what is the goal?
Ensure that soil always maintains some degree of readily available
water within crop’s root zone
placez dans l’ordre : … < … < …
WHC, Critical point and soil water content
Critical point < Soil water content (SWC) < WHC
full irrigation
Applying water to field at regular intervals throughout
growing season to maintain desired level of available soil water
full irrigation pros and cons?
- If negative effects avoided (e.g., water logging, pests and disease) this
approach would provide good yield, but does not encourage sustainable
use of water - Excess water wasteful and could lead to damaging factors (Maladies fongiques)
what is supplemental irrigation?
Supplemental irrigation = Selective application of water to primarily rainfed
fields when rainfall is insufficient to protect plants against water stress
goals of supplemental irrigation:
- Restore soil moisture to adequate level of available water within
optimal range - Rather than seeking full irrigation amount, water application
planned to ensure critical point is maintained at least during critical
growth stages
What ir the critical level of a water crop that begings to exeprience stress when available water drops to 50%?
critical level of moisture=50%
true or false: scheduling of water applications is less important than irrigation amount?
false:Scheduling of water applications possibly even more important than
irrigation amount
irrigation scheduling depends on range of considerations:
- Growth stage
- Soil moisture conditions
- Climate and rainfall predictions
- Soil type and management
- Crop type
- Irrigation method
benefits of irrigation scheduling?
- Plant heath and yield
- Water productivity (e.g., limiting water lost)
- Energy and labour investment (only when necessary)
- Soil health (e.g., preventing impacts of water logging)
- Environment (e.g., runoff)
what are the 5 types of irrigation scheduling? -aller consulter les caracteristiques et pros and cons
1.simplified approach
2.technology approach
3. crop observation method
4. soil water balance method
5.critical stages method
Irrigation efficiency=?
Percentage of water extracted for use in irrigation
that will ultimately be delivered to the root zone of plants
issiues with irrigation depth method?
- Doesn’t take into account specific crop requirements (ETa or ETc)
- Based on full irrigation (achieving WHC)
- Requires daily knowledge of SWC
water budget:
what are the water inputs and uses?
-Water inputs = precipitation, irrigation, capillary rise
-Water uses = transpiration, evaporation, deep percolation, runoff
what is effective precipitation?
Effective precipitation (Pe) = Rainwater that is stored
in soil and accessible to plants
