2.Water use of crop Evaporation Transpiration Evapotranspiration (ET)=Water use of crop For rice: ET deep percolation=water use of field units:mm or m3/ha
2. Water use of crop • Evaporation + Transpiration = Evapotranspiration (ET)=Water use of crop For rice: ET + deep percolation= water use of field units： mm or m 3/ha
Conversion factors for evapotranspiration depth volume per unit area energy per unit area mm day-1 m3 ha-1 day- I s-1 ha-1 MJ m-2 day-1 1 1 mm day-1 7 10 0.116 2.45 1 m3 ha1 day- 0.1 1 0.012 0.245 1 1Is-1 ha-1 8.640 86.40 1 21.17 1 MJ m-2 day- 0.408 4.082 0.047 1 1
Conversion factors for evapotranspiration d e p t h v olu m e p e r u nit a r e a e n e r g y p e r u nit a r e a * m m d a y-1 m 3 h a-1 d a y- 1 l s-1 h a-1 M J m-2 d a y-1 1 m m d a y-1 1 1 0 0.116 2.45 1 m 3 h a-1 d a y- 1 0.1 1 0.0 1 2 0.2 4 5 1 l s-1 h a-1 8.6 4 0 8 6.4 0 1 2 1.1 7 1 M J m-2 d a y- 1 0.4 0 8 4.0 8 2 0.0 4 7 1
Example If ET=5mm/d,then how much water consumed by crop in 1 ha per day? ·ET=5/1000*10000=50m3/ha/d (1ha=10000m2) 。 If irrigation depth 50mm (500m3/ha),then irrigation interval=? Irrigation interval=50mm/5mm=10 days
Example • If ET=5mm/d, then how much water consumed by crop in 1 ha per day? • ET=5/1000*10000=50m3/ha/d (1ha=10000m2) • If irrigation depth 50mm (500m3/ha), then irrigation interval=? • Irrigation interval=50mm/5mm=10 days
3.Factors affecting evapotranspiration Factors affecting evapotranspiration with reference to related ET concepts ET weather ETo parameters crop characteristics management environmental factors ● c adj
3. Factors affecting evapotranspiration
3.Factors effected water use of crop Weather parameters:radiation,air temperature,humidity and wind speed. Crop characteristic:crop type,variety and development stage
3. Factors effected water use of crop • Weather parameters: radiation, air temperature, humidity and wind speed. • Crop characteristic: crop type, variety and development stage