(b) Which system of irrigation does the picture show? In which kind of soil is this system of irrigation very useful? (c) Which method of sowing seeds is shown here? List one disadvantage of this method.
Answers
Explanation:
according to the picture the above question can be answered
Previous Page Table of Contents Next Page
CHAPTER 7. CHOOSING AN IRRIGATION METHOD
7.1 Surface, Sprinkler or Drip Irrigation
7.2 Basin, Furrow or Border Irrigation
To choose an irrigation method, the farmer must know the advantages and disadvantages of the various methods. He or she must know which method suits the local conditions best. Unfortunately, in many cases there is no single best solution: all methods have their advantages and disadvantages. Testing of the various methods - under the prevailing local conditions - provides the best basis for a sound choice of irrigation method. This chapter gives some very broad guidance and indicates several important criteria in the selection of a suitable irrigation method.
7.1 Surface, Sprinkler or Drip Irrigation
The suitability of the various irrigation methods, i.e. surface, sprinkler or drip irrigation, depends mainly on the following factors:
- natural conditions
- type of crop
- type of technology
- previous experience with irrigation
- required labour inputs
- costs and benefits.
NATURAL CONDITIONS
method. In general, drip and sprinkler irrigation are technically more complicated methods. The purchase of equipment requires high capital investment per hectare. To maintain the equipment a high level of 'know-how' has to be available,. Also, a regular supply of fuel and spare parts must be maintained which - together with the purchase of equipment - may require foreign currency.
Surface irrigation systems - in particular small-scale schemes - usually require less sophisticated equipment for both construction and maintenance (unless pumps are used). The equipment needed is often easier to maintain and less dependent on the availability of foreign currency.
crops such as maize, vegetables and trees.
Border irrigation is particularly suitable for close growing crops such as alfalfa, but border irrigation can also be used for row crops and trees.
REQUIRED DEPTH OF IRRIGATION APPLICATION
When the irrigation schedule has been determined (see Volume 4) it is known how much water (in mm) has to be given per irrigation application. It must be checked that this amount can indeed be given, with the irrigation method under consideration.
Field experience has shown that most 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. (In large-scale irrigation projects, the amounts of water applied may be much higher.)
This means that if only little water is to be applied per application, e.g. on sandy soils and a shallow rooting crop, furrow irrigation would be most appropriate. (However, none of the surface irrigation methods can be used if the sand is very coarse, i.e. if the infiltration rate is more than 30 mm/hour.)
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.