Template:Chapters 2.7

2.7 - Soil clump test to determine if root/tuber crops can be planted

Kirsty Yates, University of Guelph,Canada

Suggested citation for this chapter.

Yates,K. (2022) Grafting to improve tree propagation. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

An Introduction To Soil Types

When it comes to cultivating crops, it is important to know which type of soil one is working with. This is not only because different crops will simply grow differently in different soils, but also because it determines how crops are managed after being planted (e.g. fertilization strategy). There are three main types of soil: sandy, clay, and loam (FAO, 2022). When it comes to growing root and tuber vegetables, a sandy soil or a sandy-loam mixed soil is ideal (FAO, 1977). A simple test called the soil clump test can help a farmer, or someone working with a farmer, to distinguish these soil types.

Sandy soil: Groundnuts, peanuts, tubers and other root vegetables grow best in sandy soil (FAO, 1977). Examples of root/tuber crops include carrots, potatoes, sweet potatoes, yams and cassava. The sandy soil allows root vegetables to grow easier since its loose density lets the vegetables have space to expand (FAO, 1997, Jagdish, 2019). The loose soil also makes it easier to harvest them when they are ready. Sandy soils do not hold as much water as loam and clay soils. Crops that require a lot of water such as paddy rice, would not grow well in sandy soil as they require higher water retention (Jagdish, 2020).

Clay soil: Tuber and root vegetables will not grow well in clay soil and will be more difficult to harvest (FAO, 2022). The dense nature of clay soil does not allow root vegetables to expand or be pulled out easily. It also holds onto moisture as it has high-water retention, causing water logging which can rot root crops and prevent oxygen from flowing to the roots (FAO, 2022). Clay soil is ideal for crops such as paddy rice, which require a heavy soil to anchor their roots, and which can be flooded with water (Jagdish, 2020).

Loam soil: Loam soil is a mixture of sandy and clay soil. It is an ideal soil type for most common cereal and vegetable crops (Jagdish, 2020) such as wheat, maize, sugarcane, tomatoes, leafy green vegetables, etc. Because loam soil is mixed with sand, it still has good drainage (Jagdish, 2020), which also makes it a suitable medium for growing some root vegetables such as potatoes (FAO, 1977).

Determining Soil Type With A Squeeze Test (Soil Clump Test)

What is a squeeze test (also known as a soil clump test)?

A ‘squeeze test’ is the name of a very easy, fast, and free method to determine the type of soil on a farmer’s field. It is simple; all that is needed is one’s hands to squeeze soil from the farmer’s field. The ideal soil will be moist, but not wet. Whether the soil falls apart or holds its shape will let the farmer know what type of soil they are working with (Vanderlinden 2021).

Preparing for the squeeze test:

First, the farmer will need to find wet soil in the area they are considering planting crops in.(Washington State University, 2018) If the soil is dry, water can be used to moisten it. Next, the farmer will use their hand to pick up some of the moist soil and feel the soil by rubbing it between their fingers. Soil that is sandy will feel gritty (rough). Soil that is loamy (a mixture of sand and clay) will feel smooth. Soil that is heavy in clay will feel sticky (Washington State University, 2018). Now, the soil type can be confirmed by conducting a squeeze test.

How to conduct the squeeze test:

1. Take a handful of moist soil from the selected area. If the soil is not easy to grab, use a shovel and dig some out.

2. Give the handful of soil a firm squeeze inside a closed fist (Vanderlinden, 2021).

3. Open the hand and watch what the soil does:

-If the soil clump holds its shape and does not crumble when poked it, it is clay soil, which is good for growing water-intense crops like paddy rice.

-If the soil clump crumbles as soon as the hand is opened, or with a very light poke, it is sandy soil or sandy loam. Sandy soil is the ideal soil for growing root and tuber vegetables.

-If the soil clump holds its shape but crumbles apart with a poke, it is loam soil, which is good for growing most common vegetable and cereal crops including maize and wheat. Loam soil is also suitable to grow root vegetables (Vanderlinden, 2021).

For a visual step-by-step on squeeze tests in different geographic regions, please refer to the picture lessons for farmers below.

Implications Of Soil Type On Fertilizer Management

When applying fertilizer, it is extremely important to know what type of soil the fertilizer is being added to, which the squeeze test helps to determine. This is because sandy soil, which drains quickly, will leach fertilizer upon rainfall (FAO, 2022; Jagdish, 2019). Therefore, using too much fertilizer in a single dose is wasteful, as the fertilizer will leach away before it is absorbed by the plant, since sandy soil cannot bind it (FAO, 2022). Therefore, crops growing in sandy soil need to have their fertilizer dose split across multiple applications during the growing season. Adding organic matter to sandy soil, such as manure, can aid in binding water and fertilizers (FAO, 2022). These characteristics are opposite to soil heavy in clay. Clay soil has excellent water retention, meaning it drains slowly, and therefore needs to be fertilized less often. Not only can clay soil hold onto nutrients from fertilizers longer, allowing for less frequent fertilizations, it is typically naturally more fertile (Oregon State University, 2003).

Benefits Of The Squeeze Test To Smallholder Farmers, Especially Women Farmers

The simple soil squeeze test can significantly improve the livelihoods of small scale farmers, especially women farmers and their families for a multitude of reasons. Growing the correct crop suited to its soil type can dramatically increase yield; for example, growing yams in sandy/loam soil will produce greater results than in clay soil (Jagdish, 2019). Knowing the type of soil being farmed also determines how much water and fertilizer are added to the crops, a task often undertaken by women farmers (FAO, 2011). This may lead to a woman having to tend to her crops less or more often, which is important to know when time is budgeted. As well, knowing the correct amount of fertilizer to use and the appropriate times to use it saves money. Fertilizer can be extremely difficult to access in poorer nations and is expensive for small quantities when it is available (Foreign Agricultural Service, 2022). An increase in yield due to understanding soil types can also create an opportunity for women to generate more income (FAO, 2011). Women make up 60-90% of the agricultural labour force in developing countries (SOFA and Doss, 2011). If the crops are successful and there is excess food, they can be sold or traded for other necessities. With greater quantities of food and income, farmers and their children will receive more nutrients, therefore, energy, to pursue education, off-farm jobs and participate in leisure activities (SOFA and Doss, 2011). There will also be more time for women farmers to complete household tasks, such as taking care of children and elderly family members and rearing livestock. These benefits will have a multi-generational effect, as nutrition, education and income are keys to ending generational poverty and promoting development (SOFA and Doss, 2011). Root vegetables are extremely important sources of nutrients for many people around the world (FAO, 1998). Cassava is the 4th most important subsistence crop grown globally and the most important root crop grown in Africa (FAO, 1998). Therefore, knowing how to maximize yield of these crops will be very beneficial to farmers.

Critical Analysis

Conducting soil squeeze tests uses no additional resources other than a human hand and require no difficult logistics or background education. Therefore, this is a simple practice that easily could be adopted by every small scale farmer in the world, especially women farmers, who do much of the crop cultivation (FAO, 2011). When conducting soil squeeze tests, one must keep in mind that results are subjective and open to interpretation by those conducting the test. The squeeze test is a crude test, that does not tell a farmer the specific percentages of each soil type within a field. Furthermore, soil health is determined by numerous biophysical characteristics such as pH and mineral composition that cannot always be determined without diagnostic equipment (Washington State University, 2018). However, this simple innovation does not require special equipment or capital costs. There are no storage or transport issues, and no safety or sustainability issues. However, the squeeze test can result in improved yields and soil productivity by understanding the components of the soil being farmed. Soil squeeze tests also find optimal spots for crops, since a farmer’s fields can be variable. In conclusion, there are few negatives to conducting this simple, free and quick test, but considerable benefits. It is an appropriate technology for smallholder farmers.

Picture Based Lesson to Train Farmers

Click on the image to access a higher resolution image as well as lessons adapted for different geographic regions.

South Asia - Click http://www.sakbooks.com/uploads/8/1/5/7/81574912/3.7_nepoli_version_uncaption.pdf

- Click http://www.sakbooks.com/uploads/8/1/5/7/81574912/3.7_south_asian_eng.pdf

East Asia and Southeast Asia - Click http://www.sakbooks.com/uploads/8/1/5/7/81574912/3.7east_southeast_asia_englishversion.pdf

Sub-Saharan Africa and Caribbean - Click http://www.sakbooks.com/uploads/8/1/5/7/81574912/3.7subsaharan_africa_carribean_engversion.pdf

Latin America - Click http://www.sakbooks.com/uploads/8/1/5/7/81574912/3.7latin_america_eng_version.pdf

North Africa and Middle East - http://www.sakbooks.com/uploads/8/1/5/7/81574912/3.7n._africa_middleeast_eng_version.pdf

Interested in more picture lessons? View the full SAK book specified to your region for free http://www.sakbooks.com/.

Links To Useful Resources

YouTube Videos:

Click https://www.youtube.com/watch?v=a-P2b008TC0 of a soil squeeze test on sandy, loam and clay soil.

Click https://www.youtube.com/watch?v=x9jVFavCx4M to watch a video of 5 helpful tips for growing root/tuber crops.

Practical Training Manuals and Additional Information:

Click https://www.fao.org/3/bp059e/bp059e.pdf -for a manual on growing different root and tuber vegetables.

Click https://www.fao.org/3/x5415e/x5415e01.htm - to read about the nutritional values of different root and tuber vegetables.

Click https://www.fao.org/soils-portal/soil-management/management-of-some-problem-soils/sandy-soils/en/ - for a short guide on managing sandy soil.

Click https://www.fao.org/soils-portal/soil-management/management-of-some-problem-soils/heavy-cracking-clays/en/ - for a short guide on managing clay soil.

Click https://www.agrifarming.in/crops-suitable-for-loam-soil-a-full-guide#:~:text=Loamy%20soil%20is%20ideal%20for,cucumbers%2C%20onions%2C%20and%20lettuce -for more detailed nformation on loam soil, including recommended crop types.

Click https://www.agrifarming.in/crops-suitable-for-sandy-soil-a-full-guide -for more detailed information on sandy soil, including recommended crop types.

Click https://www.agrifarming.in/suitable-crops-for-clay-soil-clay-soil-properties -for more detailed information on clay soil, including recommended crop types.

References

1. FAO (1977) Better Farming Series. Roots and tubers. Food and Agricultural Organization of the United Nations, Rome. https://www.fao.org/3/bp059e/bp059e.pdf

2. FAO (1998). Storage and Processing of Roots and Tubers in the Tropics. Chapter 1. Food and Agricultural Organization of the United Nations, Rome. https://www.fao.org/3/x5415e/x5415e01.htm

3. FAO (2011). The role of women in agriculture. Food and Agricultural Organization of the United Nations, Rome. https://www.fao.org/3/am307e/am307e00.pdf

4. FAO (2022). FAO Soil Portal. Management of Heavy Cracking Clays. Food and Agricultural Organization of the United Nations, Rome. https://www.fao.org/soils-portal/soil-management/management-of-some-problem-soils/heavy-cracking-clays/en/

5. FAO (2022). FAO Soil Portal. Management of Sandy Soils. Food and Agricultural Organization of the United Nations, Rome. https://www.fao.org/soils-portal/soil-management/management-of-some-problem-soils/sandy-soils/en/

6. Foreign Agricultural Service (2022). Impacts and Repercussions of Price Increases on the Global Fertilizer Market. International Agricultural Trade Report. Foreign Agricultural Service, U.S. Department of Agriculture. https://www.fas.usda.gov/data/impacts-and-repercussions-price-increases-global-fertilizer-market

7. Jagdish (2019). Agriculture Farming. Crops Suitable for Sandy Soil- A Full Guide. AgriFarming. https://www.agrifarming.in/crops-suitable-for-sandy-soil-a-full-guide

8. Jagdish (2020a). Agriculture Farming. Crops Suitable for Loam Soil – A Full Guide. AgriFarming. https://www.agrifarming.in/crops-suitable-for-loam-soil-a-full-guide#:~:text=Loamy%20soil%20is%20ideal%20for,cucumbers%2C%20onions%2C%20and%20lettuce.

9. Jagdish (2020b). Agriculture Farming. Suitable Crops for Clay Soil, Clay Soil Properties. AgriFarming. https://www.agrifarming.in/suitable-crops-for-clay-soil-clay-soil-properties

10. Oregon State University (2003). There's no break for people who garden in clay. Oregon State University Extension. https://extension.oregonstate.edu/news/theres-no-break-people-who-garden-clay

11. SOFA team and Doss, C (2011). The Role of Women in Agriculture. ESA working paper number 11-02. Agricultural Development Economics Division of the The Food and Agriculture Organization of the United Nations. https://www.fao.org/3/am307e/am307e00.pdf

12. Vanderlinden, C. (2021). Four Easy Do-It-Yourself Soil Tests: These tests will help determine your soil´s properties. The Spruce. https://www.thespruce.com/easy-diy-soil-tests-2539856

13. Washington State University (2018). Easy do-it-yourself (DIY) soil tests. Washington State University Spokane County Extension Master Gardener Program. https://s3.wp.wsu.edu/uploads/sites/2076/2018/04/C221-DIY-Soil-Tests.pdf