Water Management in Horticultural Crops (1+1)

Required depth of irrigation application

• When the irrigation schedule has been determined it is known how much water (in mm) has to be given per irrigation application
  
• Field experience has shown that more water can be applied per irrigation application when using basin irrigation, less with border irrigation and least with furrow irrigation. In practice, in small-scale irrigation projects usually 40-70 mm of water are applied in basin irrigation, 30-60 mm in border irrigation and 20-50 mm in furrow irrigation.
  
• This means that if only little water is to be applied per application e.g. on sandy soils and a shallow rooting crops, furrow irrigation would be most appropriate.
  
• If, on the other hand, a large amount of irrigation water is to be applied per application, e.g. on a clay soil and with a deep rooting crop, border or basin irrigation would be more appropriate.
  
• The above considerations have been summarized in Table 1. The net irrigation application values used are only a rough guide. They result from a combination of soil type and rooting depth. For example, if the soil is sandy and the rooting depth of the crop is medium, it is estimated that the net depth of each irrigation application will be in the order of 35 mm. The last column indicates which irrigation method is most suitable. In this case medium furrows or short borders.
Table 1. Selection of an irrigation method based on the depth of the net irrigation application


Soil type	Rooting depth of the crop	Net irrigation depth per application (mm)	Irrigation method
Sand	Shallow	20-30	Short furrows
	Medium	30-40	Medium furrows, Short borders
	Deep	40-50	Long furrows, Medium borders
			Small basins
Loam	Shallow	30-40	Medium furrows, Short borders
	Medium	40-50	Long borders, Medium borders
	Deep	50-60	Long borders, Small basins Medium basins
Clay	Shallow	40-50	Long furrows, Medium borders
	Medium	50-60	Long borders, Small basins, Medium basins
	Deep	60-70	Large basins