Water use and Irrigation
Water use
The water use of a crop with a closed canopy is about 90% of the evaporation of an open water surface.
Open pan
The evaporation may be 3 mm - 8 mm per day,depending on climatical conditions.
The water used by a crop is replaced by rainfall or irrigation.
An estimate on the irrigation frequency can be made using good weather observations.
The need for irrigation can also be determined by estimating the soil water content by hand.
Rooting depth
For water supply of a crop it is important that the plants forms deep roots
ROOTING DEPTH
Irrigation methods
Irrigation methods surface-, sprinkler- and micro-irrigation.
IRRIGATION METHODS
Drought periods
A drought period at the early stages will stop the production of the crop for some time, but a late drought period towards the end of the season will lead to an early dying of the crop and results in low yield.
Drought period and production
Soil cracking
It is essential to continue with irrigation until harvest, since with dry soils harvest is difficult and soils begins to crack. Through these cracks the tuber moth can reach the tubers.
Water surplus
Too much water has negative effects: 1) wasting of water, 2) poor root development, 3) opening of lenticels, which allow micro-organisms to enter, 4) increased risks of tubers to be attacked by fungus and bacterial diseases.
Water quality
Irrigation water should not contain too much salt and be free from dangerous bacterial diseases (e.g. Bacterial wilt).
SALINITY AND IRRIGATION