Flood deposited sand is a major problem on the river basins in Nepal (Adhikari, 2003). Farming in sandy soil particularly in flood prone areas needs longer and greater efforts where land reclamation is issue in sand deposition. Sandy soils have a wide range of limiting factors for agricultural use (Zhao et. Al.,): these include nutrient deficiencies, acidity, low water storage and poor physical attributes.
As a result, farmers are challenged by low yield. In this regard, after several field experiences, we have identified a possible means to revitalize soil health so that farmers can repair newly deposited sandy soils and restore land to a productive state in such a situation.
We have identified some management strategy that holds potential for farming in sandy soil. However, before getting into it, it is better to consider some of the benefits of sandy soil. Sandy soil is advantageous in terms of loose texture and good drainage. Most of the root vegetables and some other crops that require loose soil and good drainage best thrive in sandy soil. And also problems like root rots and other soil borne diseases is almost nonexistent in sandy soils.
Choice of appropriate crops
Root crops—like carrots, beets, radishes, and other tap-rooted vegetables—perform much better in sandy soils than in clay soils. It takes a lot of work to bring clay soil up to the kind of tilt that favors root crops.
Other crops— like green leafy vegetables, water melon, pointed gourd, tomato (Imbrahim and Fadni, 2013), etc. also best thrive in light soil with good drainage.
Photo: Farming in Sand deposited Soil after flooding in Koshi region. In the year 2008, the river changed course and flooded areas which had not been flooded in many decades. More than 1000 ha of cultivable land in the affected region were transformed into virtual desert due to sand deposition.
Post flood soil management strategy
Before cropping in flood deposited sandy soil, one should follow some management strategy that lowers the negative impact of sandy soil. Management strategy should hold techniques to restore overall soil health including soil texture, water holding capacity, nutrient retention capacity necessary for crop growth and better productivity.
One or more of below activities to be carried out:
1. Removing constraints to crop production: Flood may deposit sand and unwanted debris on cultivable land. It may also sweep away top soil that is rich in plant nutrients and important soil dwelling microorganisms. Or, both situations may arise ultimately resulting in loss of productivity of land and require efforts to remove unwanted materials or treatment of soil to restore the productivity.So, at first it is necessary to create a suitable environment for raising crops by removing the physical (such as pebbles, wood, or other those cannot be incorporated into the soil) and biological (such as grasses, weed seeds, etc.,) barrier for crop production. And this can be achieved by removing debris and sedimentation in the field either by physical removal or by tilling it into the soil depending upon the volume of the materials.
2. Adding organic matter into the soil: If deposited volume of sand and debris is too thick to till and physical removal is impossible, farmers can add organic matter in (approx. 5-10kg/m2) larger volumes that can help restore soil health with time. In some cases a farmer tries adding silt or clay in sandy soil which is in practice but if that is not added with organic matters, most of it will just flush through the soil. Increasing soil organic matter is the key to cultivating in sandy soil. Soil needs certain portion of sand, silt and clay bound by organic matters to retain soil moisture and good aeration. The good soil is “sticky”, so water and nutrients don’t just flush through every time it rains.
3. Creating and stimulating soil microbial activity: Besides nutrient and water, soil microorganisms play an important role in healthy establishment for crops. Reintroducing microorganisms into the soil, together with the organic matter they feed upon, has the potential to be a key part of restoring soil health, development of sustainable agriculture and food security based on restored soil health. The soil microorganisms can be available/found in forest soil or can be introduced manually by using effective microorganism (EM). EM is usually available at agro-vets in the form of liquid and can be mixed with manure before applying to the soil or can be introduced into the soil through irrigation water. Once microorganism is introduced into the soil, it multiplies itself on getting good environment like sufficient amount of organic matter and moisture in the soil.
- Transform raw elements from one chemical form to another. Important nutrients in the soil that are released by microbial activity are Nitrogen, Phosphorus, Sulfur, Iron and others.
- Break down soil organic matter into a form useful to plants. This increases soil fertility by making nutrients available and raising cation-exchange capacity (CEC) levels.
- Degrade pesticides and other chemicals found in the soil.
- Suppress pathogenic microorganisms that cause diseases. The pathogens themselves are part of this group, but are highly outnumbered by beneficial microbes.
Soil microorganisms not only nourish and protect plants but also play crucial roles in providing many “ecosystem services” that are absolutely critical to human survival.
4. Mulching: Mulching is probably the most important but under-utilized tool in modern agriculture. However, it is one of the most important practices to restore soil health for both sandy soil and clay soil. A good layer of mulch reduces evaporation from the soil surface and is one of the best ways to retain soil moisture (Sinkevičienė et.al, 2009). It keeps the soil surface cool, brings the microbial life of the soil right up to the surface, and provides habitat for the surface shredders—micro arthropods like oribatid mites and springtails—that are so critical to the soil food web. Usually, ultraviolet (UV), heat, and dryness nearly sterilize the top inch of soil, but mulch makes this layer warm and moist in summer, so the soil food web releases more nutrients for the crops. Mulch especially organic mulch significantly decreases soil temperature and increases crop yield (Sinkeviciene et.al., 2009, Parmar et. al., 2013 and Bhardwaj, 2013)
Conclusion: Sandy soil has its good points. It is easy to dig and can be worked earlier in the spring than other soil types. It is not as susceptible to frost heave as clay soils. With the addition of some organic matter, microorganisms and mulching, the light textured sandy soil can be best utilized for growing many varieties of vegetables and flowers, and is well suited to annual root crops, especially potatoes (Solanum tuberosum).
Adhikari, Basista Raj. 2013. Flooding and Inundation in Nepal Terai: Issues and Concerns. Hydro Nepal, Issue no. 12
Bhardwaj, Raju Lal. 2013. EFFECT OF MULCHING ON CROP PRODUCTION UNDER RAINFED CONDITION – A REVIEW. Agri. Reviews, 34 (3): 188-197, 2013. DOI- 10.5958/j.0976-0741.34.3.003
Das, Kalyan. 2012. Farm Productivity Loss due to Flood-Induced Sand Deposition: A Study in Dhemaji, India (SANDEE Working Papers, ISSN 1893-1891; WP 73–12)
Ibrahim, Kh. H. M. and O.A.S. Fadni. 2013. Effect of Organic Fertilizers Application on Growth, Yield and Quality of Tomatoes in North Kordofan (sandy soil) western Sudan. Greener Journal of Agricultural Sciences ISSN: 2276-7770 Vol. 3 (4), pp. 299-304, April 2013.
Parmar H. N., N. D. Polara*, R. R. Viradiya. 2013. Effect of Mulching Material on Growth, Yield and Quality of Watermelon (Citrullus Lanatus Thunb) Cv. Kiran. Universal Journal of Agricultural Research 1(2): 30-37, 2013
Sinkevičienė, A., D. Jodaugienė, R. Pupalienė and M. Urbonienė. 2009. The influence of organic mulches on soil properties and crop yield. Agronomy Research 7(Special issue I), 485–491, 2009
Zhao, Y. G.1, G. L. Zhang, 1, Z. Wen-Jun1, and Z. T. Gong1. Soil characteristics and crop suitability of sandy soils in Hainan, China. Global extent of tropical sandy soils and their pedogenesis
Rakesh Khadka is currently working as Project Officer at Practical Answers, Practical Action, Kathmandu Nepal. You can contact him at email@example.com