As discussed in the previous lecture on surface irrigation methods, furrow irrigation is a class of surface irrigation methods in which water is field is divided into ridge and furrows. The crop is grown on the ridge whereas irrigation water is applied to the furrow.
General Adoptability
The adaptability of furrow irrigation to a specific site depends on climate, soils, topography, crops to be grown, and water supply.
Climatic Factors
- Precipitation and wind may affect suitability as well as the design criteria.
- Risk of surface runoff and excessive soil erosion due to excessive precipitation, concentrated runoff in the channels resulting in crop damage from flooding; these conditions must be considered in determining which furrow method is suitable for a given area.
Soil
- Medium to moderately fine-textured soils of relatively high available water holding capacity are desirable
- Intake characteristics should facilitate both lateral and vertical water penetration
- Furrow irrigation generally is not recommended on soils containing high concentrations of salts.
Fig. Lateral and vertical water movement during furrow irrigation.
Topography
- The rows can be laid out on a continuous grade.
- The topography must be such that levelling does not expose unproductive soil or that the cost of levelling is not excessive.
- The topography must not be so steep that it exceeds the allowable corrugation grade or prohibits installation of graded contour furrows that meet the design grade and cross-slope criteria.
Crops
- Adapted for nearly allirrigated crops except those grown in ponded water, such as rice.
- Suitable for irrigating crops subject toinjury if water covers the crown or stems of the plants.
Water Supply
The quantity and quality of the water supplydetermines its suitability for use in furrow irrigation.
Furrow Irrigation Design Consideration
Efficient irrigation by furrow method is obtained by selecting proper combination of spacing, length, slope of furrows, suitable size of the irrigation stream and duration of water application.
Furrow Spacing
Furrows should be spaced close enough to ensure that water spreads to the sides into the ridge and the root zone of the crop, to replenish the soil moisture uniformly.
Table -Recommended furrow spacing for different soil types, and depths of irrigation for complete wetting
|
Soil type |
Depths of irrigation (m) |
Furrow spacing (cm) |
|
Sandy soil |
1 to 1.5 |
50 to 60 |
|
Clay soil |
1 to 1.5 |
100 or more |
