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close this bookIrrigation Training Manual: Planning, Design, Operation and Management of Small-Scale Irrigation Systems (Peace Corps, 1994, 151 p.)
close this folderTraining session
close this folderSection 8: Waterlogging and salinity
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View the documentExam: Section 8 - Assessing field problems and solutions


* Basic Concepts of Waterlogging and Salinity
* Control of Drainage and Salinity Problems
* Exam: Section 8 (Assessing Field Problems and Solutions)

Session Topic: Basic Concepts of Waterlogging and Salinity

Session Goal: Trainees will be able to describe the causes and problems associated with waterlogging and salinity.

Session Objectives:

(1) Trainees will identify waterlogged or salt-affected soils in the field and the probable causes of the problem and will explain difficulties that these conditions will cause for crop production.

(2) Trainees will describe field methods used to identify problems with salinity and alkalinity in soils.

(3) Trainees will learn to use tables to evaluate the effect of soil and water salinity and sodic levels for various crops.

Overview: Waterlogging and salinity can be a serious problem in many irrigated areas. Trainees need to understand how to identify the severity of these problems in the field and work with practices that can improve soil conditions. This session introduces basic concepts and prepares Trainees to work with field practices in waterlogging and salinity control.

Session Activities:


45 Min.

Trainer will introduce basic concepts of waterlogging, salinity and alkalinity, and use slides or videos to review typical conditions, tolerant crops, effects on susceptible crops, field identification practices, and analysis procedures that are typically applied. (If video equipment is not available, trainer can use graphics to cover topics.)

60 Min.

Trainer leads Trainees into the field and has them dig shallow holes in waterlogged areas and in well-drained areas. Trainees should compare the soil conditions and the apparent effects on plants in the field. The trainer should discuss with the Trainees probable causes of, and potential solutions to, the problems.

60 Min.

Trainees move to a field site with salinity problems. Observations of effects on plant growth are recorded, and methods for identifying salinity problems in the field are defined. Trainees meet with a local farmer and discuss the farmer's experiences in trying to work with or improve salinity problems.

60 Min.

Trainees visit a sodium affected field and identify areas within the field that demonstrate dispersed soil that has lost its structure. Impacts on crop growth and irrigation water infiltration rates are observed and recorded. Trainees will discuss with the trainer the probable causes of the problem and potential solutions. Again, Trainees meet with a local farmer to discuss the farmer's concerns and experience.

60 Min.

Trainees move to a field where they can conduct some simple experiments. Trainer instructs Trainees to build three small basins. Trainees should prepare three solutions, as follows: (a) plain water, (b) water with a mixture of approximately 0.25 kilogram salt per every four liters of water, (c) water with a mixture of approximately 0.25 kilogram of any chemical fertilizer per every four liters of water. Each basin should be filled with one of these solutions, and allowed to drain. After the solution has completely drained, add a second, and then a third mix to the basin. Trainees should observe and discuss the differences in terms of water penetration and resulting soil structure and color in each basin. Trainees should discuss the long term effects of these conditions on crop growth.

60 Min.

In many countries laboratory facilities are available and tests for salinity and sodium problems can be performed. Trainees need to learn basic skills to enable them to collect samples and interpret lab results. Trainer should obtain soil or water lab results from in-country and use the data to prepare simple problems for the Trainees to analyze. Problems should require the Trainees to consult the following tables: (a) Crop Salt Tolerance Levels for Different Crops as Influenced by Irrigation Water or Soil Salinity, and (b) Effect of Irrigation Water Quality on Soil Salinity, Permeability, and Toxicity (see Chapter 7 of Irrigation Reference Manual). Trainees should classify the soils or water samples in terms of the degree of salinity or sodicity problems evident.

Trainer Notes: This is an important session for Trainees who will be working in arid and semi-arid areas with high water tables and poor drainage conditions. Waterlogging and salinity usually become a problem when water tables are 1 meter or less below the soil surface. Trainers should locate several potential field sites for Trainees to visit and inform farmers of the intent of the visit.

Materials Required:

* 3 buckets
* copies of tables 7.2 and 7.4 from Chapter 7 of Irrigation Reference Manual
* salt, fertilizer
* soil or water lab analysis results
* shovel, hoe


Chapter 7, Irrigation Reference Manual: Waterlogging and Salinity Problems

International Irrigation Center Modules #14 - #17

Session Topic: Control of Drainage and Salinity Problems

Session Goal: Trainees will identify control measures that can be used to eliminate or minimize problems with waterlogging and salinity.

Session Objectives:

(1) Trainees will identify the various soil amendments that can be used to neutralize the effects of sodium salts.

(2) Trainees will determine the timing and amount of leaching required to remove salts from the soil profile.

(3) Trainees will describe the use of artificial drainage to eliminate waterlogging and salinity problems.

(4) Trainees will describe the types of drains required to lower the water table to acceptable levels, including surface drains for evacuation of excess irrigation and rainwater.

(5) Trainees will identify cultural practices that can be used to minimize the effects of salts and waterlogging on yields.

Overview: Drainage design and construction can be a very complex endeavor. Trainees, however, should at least be familiar with the procedures used in this task. The use of soil amendments, leaching, and cultural practices is definitely within the realm of most Volunteers' work responsibilities, and Trainees will be provided with an opportunity to develop these skills in the field. This session expands on basic concepts developed in the earlier session in Waterlogging and Salinity.

Session Activities:


45 Min.

Trainer leads Trainees to the field and has Trainees demonstrate their ability to distinguish waterlogging, salinity, and sodicity problems. Trainer introduces simple techniques that can be used to begin to control these problems, including the use of soil amendments, leaching, surface and subsurface draining, and cultural practices.

90 Min.

Trainees are divided into groups of three and assigned the task of estimating and applying the correct amount of soil amendments and quantifying the amount of leaching required to improve conditions in the field they are visiting. Trainee groups describe and document cultural practices that can be employed to improve soil and water conditions. Groups reconvene and compare results and experiences.

60 Min.

Trainer brings Trainees to inspect a farm drainage system. Trainees, continuing to work in their groups of three, graphically delineate the system design, and identify the steps that were apparently followed in developing this drainage system.

45 Min.

Trainees interview a farmer working with the problems of high water table and salinity and conduct a quick visual review of the farmer's situation. Trainees offer general recommendations for the farmer on practices that can reduce or eliminate the problems, being certain to frame recommendations within the limitations of options available to the farmer.

Trainer Notes: Trainers will need to locate areas with waterlogging and salinity problems and identify one or more farmers willing to allow Trainees to visit and study their farms. Trainer should be certain to interview local farmers before this session to learn how they are typically dealing with these problems. The design of subsurface drains is beyond the scope of this training. Surface drains for the removal of excess irrigation and rainwater, however, should be discussed.

Materials Required:

* local information on soils
* soil auger
* transport
* shovel


Chapter 7, Irrigation Reference Manual: Waterlogging and Salinity Problems International Irrigation Center Modules #14, #15, #16, and #17

Ayers, R. S., and Westcot, D.W. 1985. Water Quality for Agriculture. FAO Irrigation and Drainage Paper No. 29. Rev. 1. Food and Agriculture Organization of the United Nations, Rome. 161 p.

Exam: Section 8 - Assessing field problems and solutions

1. Describe the soil characteristics of a saline soil that can be seen in the field.


White crusts on soil surface.
Plants stunted, appearing to be drought stressed even though soil is moist.
Uneven plant height and soil moisture in the field.

2. Define: (1) EC, (2) amendment, and (3) leaching.

Answer: See Glossary

3. Results of a soil sample analysis come back with an ECe of 2.2 and an ESP of 8. (1) How would this soil be classified? (2) What problems would a farmer expect to encounter when irrigating this soil?


(1) Saline-sodic
(2) Drainage and infiltration problems; runoff with heavy irrigations; uneven crops; problems with salt-sensitive crops

4. Using Table 7.2 on crop salt tolerance levels, what yields would you expect for beans? for barley? for carrots?


Beans - About 75% of normal harvest
Barley - Normal harvest
Carrots - 75% of normal harvest/d

5. How would you identify a waterlogged soil in the field?


Gray soils with black or red mottles
Water-saturated soil, standing water in holes 30- 80 cm deep

6. Draw bed shapes and plant locations that would control salinity problems with furrow irrigation.


If a farmer wanted to apply 1 ton/ha of pure gypsum to reclaim soils with sodium problems, and only lime sulfur was available, how much lime sulfur would he or she have to apply? How much sulfur would he or she apply in the process?

Answer: Given:


1 Ton of Pure Gypsum
1 Ton of Sulfur

Lime Sulfur 0.78 4.17

a. 78% x 1 ton gypsum = 1 ton lime sulfur
1 ton gypsum = 1.28 tons lime sulfur

b. Applying 1.28 tons lime sulfur x 4.17 = 5.35 tons sulfur