WOW !! MUCH LOVE ! SO WORLD PEACE !
Fond bitcoin pour l'amélioration du site: 1memzGeKS7CB3ECNkzSn2qHwxU6NZoJ8o
  Dogecoin (tips/pourboires): DCLoo9Dd4qECqpMLurdgGnaoqbftj16Nvp


Home | Publier un mémoire | Une page au hasard

 > 

Design of a geographic information supported database for the management of pressurised irrigation systems at the plantation du Haut Penja, Cameroon

( Télécharger le fichier original )
par Chick Herman AZAH
University of Dschang - Agric engineer 2009
  

précédent sommaire suivant

Bitcoin is a swarm of cyber hornets serving the goddess of wisdom, feeding on the fire of truth, exponentially growing ever smarter, faster, and stronger behind a wall of encrypted energy

2.3 Evapotranspiration

One way to improve water use efficiency and optimize plant production is to provide crops only with the water they need based on the climate-plant-soil relationship. Therefore the concept of evapotranspiration (ET) is the base for the right amount of irrigation water that should be applied.

Water supplied to crops is lost from the soil through direct evaporation and transpiration into the atmosphere (Fonteh and Assoumou, 1996). It is difficult for us to isolate the two mechanisms on a field with growing crops. As such the two losses are usually combined to give evapotranspiration (ET). Knowledge of ET enables us to predict the soil moisture deficit (SMD) for irrigation. We express the ET as a rate of loss of water e.g. 5 mm/day. ET could also be referred to as the consumptive use i.e. the total amount of water a crop takes from the soil as it grows. Designs of irrigation systems are usually based on the period of the growing season with the maximum consumptive use. Systems are designed with capacities to supply water when demand is the highest. We can differentiate between two types of ET: reference crop ET and actual ET. Reference crop evapotranspiration (ETo) is the water use of a vigorously growing reference crop under full cover, when water is not limiting (Fonteh and Assoumou, 1996). The crop or actual evapotranspiration (ETa) is the actual amount of water lost from the soil during field growing conditions. The reference crop ET is related to the actual by the equation:

(2.7)

KC is a coefficient accounting for crop maturity and water stress under which the plant is growing. KC values vary with the crop, its stage of growth, growing season and prevailing weather conditions. From the equation (2.7) the actual ET is obtained from the reference. This is because depends only on climatic factors and hence, it is easier to obtain

and then apply the crop coefficient (KC). ETa can be obtained directly for example, by determining the moisture content (MC) of the soil between a given time interval. However, this approach is slow and tedious and is used only as a check on indirect methods.

Table 2.1: Length of crop growth developmental stages for various planting periods and Climatic regions

 

Stages of Development

Plant date

Region

 
 
 
 

Crop characteristic

Initial

Crop Development

Mid- season

Late

Total

 
 

Banana 1st year

 

Stage length, days

120

90

120

60

390

March

Mediterranean

Depletion Coefficient, p

0.35

>>

0.35

0.35

-

 
 

Root Depth, m

0.30

>>

>>

0.80

-

 
 

Crop Coefficient, C

0.5

>>

1.1

1.0

-

 
 

Yield Response Factor, Ky

 
 
 
 

1.2-
1.35

 
 

Banana 2nd year

 

Stage length, days

120

60

180

5

365

February

Mediterranian

Depletion Coefficient, p

0.35

>>

0.35

0.35

-

 
 

Root Depth, m

0.30

>>

>>

0.8

-

 
 

Crop Coefficient, C

1.0

>>

1.2

1.1

-

 
 

Yield Response Factor, Ky

 
 
 
 

1.2-
1.35

 
 
 

Source: Allen et al., 1998

Table 2.2: Monthly Kc values of Banana for tropical climate

Months after planting

KC

Crop Developmental Stage

 

2

3

4

5

6

7

8

9

10

11

12

13

14

15

 

0.4

0.45

0.5

0.6

.7

0.85

1.0

1.1

1.1

0.9

0.8

0.8

0.95

1.05

 

shooting

Harvesting

 

Source: Allen et al., 1998

précédent sommaire suivant






Bitcoin is a swarm of cyber hornets serving the goddess of wisdom, feeding on the fire of truth, exponentially growing ever smarter, faster, and stronger behind a wall of encrypted energy








"Piètre disciple, qui ne surpasse pas son maitre !"   Léonard de Vinci