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  <div class="title"><h1>4.20 - Leaf colour change to diagnose fertilizer needs</h1><br><h3 class="ch-owner">Mitchell van Schepen, University of Guelph, Canada</h3></div>
  <div class="title"><h3>4.20 - Leaf colour change to diagnose fertilizer needs</h3><br><h3 class="ch-owner">Justin Huber, University of Guelph, Canada</h3></div>
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<p>Suggested citation for this chapter.</p>
<p>Huber,J (2022) Leaf colour change to diagnose fertilizer needs. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org</p>
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       <h3 class="title-bg">Background</h3>
       <h1 class="title-bg">Introduction to Nutrient Deficiency Keys</h1>
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           <p>The world’s 1 billion women and girls participating in subsistence farming pull weeds by hand to improve their crops and also collect firewood for cooking, resulting in their hands becoming rough and sore (Figure 1). This can be caused by wood splinters being lodged into their skin (Schaffner, 2013). Pulling weeds for hours on end can peel away layers of skin (Food and Agriculture Organization, 2016). The hands of those farmers can also become dirty and smelly from planting seeds in the soil or spreading manure by hand. To avoid the common aforementioned problems as well as hand injuries, such as cuts and scrapes, they could wear gloves on their hands, see the second picture, (Schaffner, 2013). Gloves are very common in the modern world and can be used for construction, farming, and medical practices. Gloves provide a durable layer between the skin on your hands and whatever you are working with (Espasandín-Arias & Goossens, 2014). There are a few different materials used to make gloves, along with different sizes and grips. With over one billion women and girls working on farms around the world, this grueling work can be made safer and more efficient when wearing gloves.</p>
           <p>Nutrient deficiency keys use photos to show a leaf with various nutrient deficiencies plotted next to one another so a farmer can see the differences among nutrient deficiencies and compare the images to their own crops, helping diagnose fertilizer needs. For example, a woman who is growing maize can realize that the yellow discolouration in the margins of her maize leaves may mean that the soil is deficient in nitrogen (Tucker, 1984). Conversely, such photos can help smallholder farmers add only the fertilizers they need, preventing waste and improving incomes. Figure 1 is an example of a basic nutrient deficiency key.  </p>
<p>[[Image:NTRY.jpg |thumb|centre|Figure 1. Example of a nutrient deficiency key. Source: https://www.haifa-group.com/articles/main-functions-plant-nutrients]]</p>
<P>Access to fertilizer varies significantly between developed and developing nations. In 2018, Canadian farmers applied an average of 85 kg/ha and 144 kg/ha of nitrogen fertilizer for wheat and maize respectively, while Senegalese farmers in Africa only applied 18 kg/ha for wheat and 25 kg/ha for maize (Ludemann et al., 2022). In recent years, the average rate of nutrients applied to Sub-Sahara African crops has been about 16 kg/ha, which is only more than a quarter of the 2016 goal set at the 2006 Africa Fertilizer Summit of 50 kg/ha (Vanlauwe & Dobermann, 2020). Since the 2006 African Fertilizer Summit, fertilizer prices have increased by 130% due to heightened petroleum prices (Chianu et al., 2011). In 2022, fertilizer prices have increased even further (Crespi et al. 2022).</P>
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      <h1 class="title-bg">Advantages of Nutrient Deficiency Keys</h1>
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<p>Variation in soil types at the local and continental level makes diagnosing nutrient deficiencies difficult; furthermore soil testing is not available to many smallholder farmers, and there is a lack of access to government extension, resulting in inadequate farmer training which is amplified by low levels of literacy (Sinyolo & Mudhara, 2017). Nutrient deficiency keys offer a way for smallholders to identify nutrient deficiencies that do not require the help of an expensive soil testing kit or having to rely on a government extension agent. Nitrogen, potassium and phosphorus are the most common types of fertilizers (Chianu et al., 2012). However, as there are 15 fertilizers required by crops, a more comprehensive addition of fertilizers, especially in extensively degraded soils (very common in Africa) may be needed in order to increase yield, but micronutrient fertilizers (e.g. zinc, boron) can be more expensive and difficult to diagnose since they are less well-known (Chianu et al., 2012). The production of nutrient deficiency keys that are specifically for micronutrients could help smallholder farmers use a more comprehensive approach to nutrient deficiencies. Knowledge about the diagnosis of nutrient deficiencies, specifically in rural areas is significantly lacking (Chianu et al., 2012). The use of photo based nutrient deficiency keys can help educate smallholder farmers with minimal interference caused by a language barrier. </p>
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      <h1 class="title-bg">Cost vs Benefit Analysis </h1>
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<p>The most significant cause for decline of per capita food production in Sub-Sahara Africa is the decline in soil fertility (Sanchez et al., 1997), and therefore it is evident that improving fertilizer usage is vital for an increase in smallholder farmer income. Evidence of this was shown in Malawi, where farmers who used fertilizer experienced a 105% increase in yield and a 21-42% increase in profit. Smallholder farmers experience yields that are rarely above 0.5 T/ha, while commercial farms and research station trials with greater knowledge and access to fertilizer can have yields of 6-8 T/ha (Chianu et al., 2012), equivalent to a 1100-1500% increase in yield. The cost to produce the deficiency keys would be minimal. About $5 USD would be needed for language translation of a nutrient deficiency key. However, when significant numbers are being purchased, this cost would be negligible on a per farmer basis. Printing is relatively cheap, with the addition of colour adding costs at about 5 cents per key. Clear sheet covers in order to protect the nutrient deficiency keys from becoming weathered would also add about 10 cents to production. In total, the nutrient deficiency keys could easily be sold for less than 25 U.S. cents each, and with the use of fertilizer increasing yields by over 100% in some cases, the potential benefits of a nutrient deficiency key would help it pay for itself rapidly.</p>
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      <h1 class="title-bg">Distribution</h1>
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<P>Getting nutrient deficiency keys to smallholder farmers could be difficult, specifically in rural parts of Africa, as well as in politically unstable regions which may not be safe. However, there are existing methods used for other minimal cost products that help distribute to rural areas. Women’s cooperatives can be an effective method of distribution. Women’s cooperatives can have many members coming from many villages. For example, a women’s cooperative run by the United Nations in Ethiopia included about 2,000 direct beneficiaries, and almost 32,000 community members that benefited indirectly (UN Women, 2020). This extensive outreach would be an excellent way to both distribute as well as spread the word on nutrient deficiency keys.</p>
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      <h1 class="title-bg">Critical Analysis and Alternate Ways to Increase the Efficiency of Fertilizer for Subsistence Farmers</h1>
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<p>There are several factors that can render nutrient deficiency keys less useful. Some nutrient deficiencies can still decrease yields while still showing minimal to no symptoms. For example, manganese usually does not show any symptoms, unless the deficiency is severe (Schmidt et al., 2016). Some nutrient deficiencies have very similar symptoms. Molybdenum is used as a cofactor for nitrate reductase, meaning it is used to break down nitrate into nitrogen for a plant to use it (Zimmer & Mendel, 1999). So, even if there was excess nitrogen available to a crop in the form of nitrate, if there is insufficient molybdenum, the plant shows identical symptoms to a nitrogen deficiency (Cox, 1992). Similarly, cobalt and iron deficiencies can be very difficult to differentiate, as they both show chlorosis of younger leaves as their main symptom (Rathour, 2022; Anderson, 2008).</p>  


          <p>Rubber and cloth are the two main kinds of gloves produced (Melco, 2016). They both have their own benefits and drawbacks respectively. A benefit from rubber gloves is their ability to resist water from coming in contact with a farmer's skin, see part two, (Espasandín-Arias & Goossens, 2014). While cloth gloves can be beneficial because they can draw moisture away from their hands and can be easily washed to be cleaned. Because rubber gloves are usually meant to be disposed of after single use they tend to be cheaper to make and thus cheaper to buy. Yet some rubber gloves can be made thicker to reuse and are slightly more durable (Melco, 2016). Cloth gloves are designed to be washed after being used and last a long time under normal working conditions.</p>
<p>Nutrient deficiencies in trees can also be difficult to diagnose with a nutrient deficiency key. This is because, first, an important part of a nutrient deficiency key is whether newer or older leaves are affected, and second because the height of trees would make it difficult to use a nutrient deficiency key.</p>  


          <p>Along with the different materials gloves are made of, there are also different arm lengths. Some gloves are cut off just in front or around the wrist. While others can be up to and over the elbow and everywhere in between (Melco, 2016). The benefits of the shorter gloves is comfort, no bunching around wrist or elbow, and they can be quickly put on or removed. The benefits of the long gloves are more protection, the entire forearm will be covered. All the while there is less of a chance of getting debris in their gloves because the opening is farther away from what you are working with. Farmers can also work in deeper water or mud with the long rubber gloves without getting your hands wet.</p>
<p>Symptoms very similar to that of a nutrient deficiency can also be present for other reasons. For example, Verticillium dahliae is a pathogenic fungus that causes the yellowing of older leaves (Hanson, 2000). Nitrogen deficiency also has this same symptom (Tucker, 1984). If a farmer were to use nitrogen fertilizer on this crop, it would not help get rid of the fungus, therefore potentially wasting fertilizer.</p>


          <p>When working with smooth items such as hoes and some fruits and vegetables they can be slippery (Food and Agriculture Organization, 2016). A way to help farmer's hold on to the tools is to get gloves with grips (Melco, 2016). Both rubber and cloth gloves can have grips. Rubber gloves will have ridges in the molds to form grips and granular materials can be added to the outside before drying (Melco, 2016). Another option is to make the rubber gloves out of a non-slip rubber (Melco, 2016). Because cloth alone does not provide grip, cloth gloves must be dipped in liquid rubber to be able to grip smooth objects. The rubber used for grips on cloth gloves can either be non-slip smooth rubber or be rigid (Melco, 2016). </p>
<p>While nutrient deficiency keys will certainly help increase yields on subsistence farms, as well as educate smallholder farmers about the use of fertilizer, increased knowledge and access to fertilizer is ultimately critical for dealing with the decline in soil fertility in Africa. This issue is mainly due to minimal policy and institutional support concerning fertilizers (Chianu et al., 2012). Success of these programs and policies is not lacking evidence. Malawi has a specialized policy-led agricultural extension program concerning the use of fertilizer. This program caused more smallholder farmers to use more mineral fertilizers, resulting in a surplus of food in a county with previous food security problems (Chianu et al., 2012). The educational differences between women and men is another factor that contributes to the lack of access to fertilizer. Igbo women in Nigeria typically have little to no knowledge of fertilizer, compared to just 25% of men who do not have this knowledge (Chianu et al., 2012). Additionally, despite Africa having large deposits of raw materials, it produces only 13% of its own fertilizer, with the rest being imported, which is part of the reason that nutrients can be so expensive to African farmers (Chianu et al., 2012). Zimbabwe has provided evidence that domestic production of fertilizer can be very beneficial. Zimbabwe produces lots of its own fertilizer and as a result, uses the most fertilizer per hectare in Sub-Saharan Africa except for South Africa (Chianu et al., 2012).</p>
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       <h1 class="title-bg">Conclusion</h1>
       <h3 class="title-bg">Physical Protection</h3>
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          <p>Protection is the main benefit from using gloves. Repetitive motions, such as when pounding grain, can cause irritation to the skin. When collecting firewood the sticks and logs can scratch or cut the skin (Food and Agriculture Organization, 2016). Weeds can be rough and by scratching their hands many times they can become cut and sore (Espasandín-Arias & Goossens, 2014). By lifting and pulling heavy items the top layer of your skin will separate from the next, causing a blister, by wearing gloves they now will prevent blistering because the glove will act as the top layer of skin and prevent the actual skin from separating (Schaffner, 2013).  Manure has a lot of bacteria in it which are harmful if they are swallow, so keeping them away from the hands used to eat with is very beneficial (Furlong, et al., 2015). If farmers are working with firewood or in construction the cloth gloves will work better because they are more durable (Food and Agriculture Organization, 2016). The disposable rubber gloves would be the worst to use in this scenario because they are so thin, stick to jobs were the main goals are to keep hands dry and dirt free when using disposable rubber gloves.</p>
<p>In summary, nutrient deficiency keys can be very helpful in helping smallholder farmers to diagnose fertilizer needs for crops. However, there is no use for them if farmers have no access to fertilizers and the knowledge needed to apply them. An increase in government extension programs, women’s education and policy can all be vital to helping Africa cope with its degrading soils.</p>
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      <h1 class="title-bg">Picture Based Lesson to Train Farmers </h1>
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[[Image:5.20 page-0001.jpg|thumb|centre|Picture Based Lesson to Train Farmer|Click on the image to access a higher resolution image as well as lessons adapted for different geographic regions.]]</p>
<p>http://www.sakbooks.com/uploads/8/1/5/7/81574912/5.20subsaharan_africa_carribean_engversion.pdf
- Sub-Sahara Africa and Carribean</p>


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<p>http://www.sakbooks.com/uploads/8/1/5/7/81574912/5.20_south_asian_eng.pdf
      <h3 style="background: #FBB03B;padding: 15px;font-weight: 600;color: #000;font-size: 22px;margin:unset;text-align:center;">Defense Against Moisture and Chemicals</h3>
- South Asia</p>
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<p>http://www.sakbooks.com/uploads/8/1/5/7/81574912/5.20east_southeast_asia_englishversion.pdf
          <p>Moisture blocking is a way gloves can prevent your skin from drying out and from getting too wet and dehydrating farmer's hands. By keeping the moisture from the hands inside the gloves they will prevent the skin from cracking and becoming infected (Schaffner, 2013). As well when working in wet conditions your hands can shrivel and become dehydrated if they are constantly in contact with water.</p>
- East Asia</p>
          <p>Pesticides can be absorbed by your skin and become harmful to the body, gloves provide an extra barrier to block them from entering in a farmer's body (Furlong, et al., 2015). Fertilizers such as nitrogen can also be caustic, and these are usually spread through broadcasting by hand. Mud can get under your nails and into cracked or cut skin and can infect a farmer's hands. Gloves will keep the mud out and keep hands clean. Both liquid pesticides and dry fertilizers can irritate skin if they come into contact with it (Kim, et al., 2013). Wearing the proper gloves, rubber ones in this case, can save their hands from becoming itchy (Keeble et al., 1996). Human skin can also absorb the pesticides which are harmful to your body, wearing gloves would prevent the pesticides from ever touching your skin.</p>
<p>http://www.sakbooks.com/uploads/8/1/5/7/81574912/5.20latin_america_eng_version.pdf
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- Latin America</p>
<p>http://www.sakbooks.com/uploads/8/1/5/7/81574912/4.17n._africa_middleeast_eng_version.pdf
- North African and the Middle East</p>
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      <h1 class="title-bg">Links to Useful Resources</h1>
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<p>Video on Diagnosing Fertilizer Needs based on Leaf Colour
https://www.youtube.com/watch?v=BftiT1WANdo</p>
<p>Helpful examples of nutrient deficiency keys for different crops</p>
<p>Maize
https://cropnuts.com/plant-nutrient-deficiency-symptom-guide-for-crops/</p>
<p>Rice
https://www.researchgate.net/figure/The-different-characteristics-of-rice-leaves-under-NPK-deficiencies_fig10_268875719</p>
<p>Soybean
https://cropwatch.unl.edu/soils/soybean-nutrients</p>
<p>Wheat
https://www.yaracanada.ca/crop-nutrition/wheat/nutrient-deficiencies/
https://cropwatch.unl.edu/soils/nutrient-deficiency-wheat</p>
<p>Banana
https://www.yara.in/crop-nutrition/bananas/nutrient-deficiencies-banana/</p>


<p>Cassava
https://www.kalro.org/asal-aprp/sites/default/files/cassava_farmers_guide_wambua_final.pdf</p>
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       <h3 class="title-bg">Wearable</h3>
       <h1 class="title-bg">References</h1>
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           <p>Comfortable gloves help farmer's work longer because their hands will not hurt from completing your task. Sizing is very important when finding comfortable gloves (Melco, 2016). Make sure gloves are the proper length and width, as not to restrict movement. There will be less pain from pulling weeds and they will be able to pull more weeds because they would not have to wait a long for the pain to subside between pulling each weed, because there will be no pain if wearing gloves (Food and Agriculture Organization, 2016). If farmer's find they are working hard and their hands start to sweat the gloves should be removed , dry your hands, and put on a new pair. Cloth gloves are more breathable then rubber ones, using them is another way to prevent hands from getting sweaty. The cloth gloves can also be softer and easier to clean, but are more restricting to movement due to their durability and tougher material. Since children will also be farming, smaller glove sizes can be found. Gloves are designed to fit a farmer's hand snugly, so children should not wear adult sized gloves when working. </p>
           <p>1. Anderson, W.B. (2008). Diagnosis and correction of iron deficiency in field crops – an overview. Journal of Plant Nutrition. 5(4), 785-795. https://doi.org/10.1080/01904168209363008</p>
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<p>2. Chianu, J.N., Chianu, J.N., Mairura, F. (2012). Mineral fertilizers in the farming systems of sub-Saharan Africa. A review. Agronomy for Sustainable Development. 32, 545-566. https://doi.org/10.1007/s13593-011-0050-0</p>
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<p>3. Cox, D.A. (1992). Foliar-applied Molybdenum for Preventing or Correcting Molybdenum Deficiency of Poinsettia. HortScience. 27(8), 894-895. https://doi.org/10.21273/HORTSCI.27.8.894</p>
 
<p>4. Crespi, J.M., Hart, M., Pudenz, C., Schulz, L.L., Wongpiyabovorn, O., Zhange, W. (2022). An examination of recent fertilizer price changes. Center for Agricultural and Rural Development. https://www.card.iastate.edu/products/publications/pdf/22sr117.pdf</p>
 
<p>5. Hanson, L.E. (200). Reduction of verticillium wilt symptoms in cotton following seed treatment with Trichoderma virens. Journal of Cotton Science. 4(4), 224-231. https://pubag.nal.usda.gov/catalog/30124</p>
 
<p>6. Ludemann, C.I., Gruere, A., Heffer, P., Dobermann, A. (2022). Global data on fertilizer use by crop and by country. Data Descriptor. 1(9), 501. https://doi.org/10.1038/s41597-022-01592-z</p>


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<p>7. Rathour, S.K. (2022). Cobalt: 18th Essential Nutrient for Plant Growth? Just Agriculture. 2(7), 1-4  https://justagriculture.in/files/newsletter/2022/march/06.pdf</p>
      <h3 class="title-bg">Constraints To Adoption</h3>
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          <p>Gloves are very useful to farmers, but there can still be some drawbacks. Possible culturable taboos might vary from location to location. Gloves might seem feminine and not easily adopted by men in the community. Gloves act as a second, tougher skin, but they are not a farmer's skin and can slide around while working. This may feel odd and uncomfortable but farmers can get used to the new feeling over time. Gloves can come in many colours and thicknesses, which may make a farmer's hands look funny or larger. Human skin is very stretchy and flexible, while glove materials tend to be tougher than skin and will reduce movement, but not enough to hinder work. Rubber gloves can stretch well, but make hands sweat, while cloth gloves are breathable but reduce dexterity.</p>
          <p>Farmers can find gloves to use and get started from local vendors (European Commission For The Control Of Foot-And-Mouth Disease, 2016). Once you have completed your work for the day you can clean them are reuse them, or dispose of them if they were ripped or torn (Kim, et al., 2013). You can get gloves made of rubber and like materials as well as ones made of durable cloths. The thin rubber gloves tend to be made for a single use only. A trick that the European Commission For The Control Foot-And-Mouth Disease mentions that you can wear two pairs of rubber gloves at the same time for extra protection (European Commission For The Control Of Foot-And-Mouth Disease, 2016).</p>
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<p>8. Sanchez, P.A., Sheperd, K.D., Soule, M.J., Place, F.M., Buresh, R.J., Izac, A.N., Mokwunye, A.U., Kwesiga, F.R., Ndiritu, C.G., Woomer, P.L. (1997) Soil Fertility Replenishment in Africa: An Investment in Natural Resource Capital. In R.J. Buresh, P.A. Sanchez, F. Calhoun (Eds.), Replenishing Soil Fertility in Africa. pp. 1-46. https://doi.org/10.2136/sssaspecpub51.c1 </p>
      <h3 class="title-bg">Helpful Links To Get Started </h3>
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          <p>Here are websites to find more information about how to obtain gloves:</p>
          <p>[https://www.alibaba.com/ Alibaba]</p>
          <p>[https://www.indiamart.com/ Indiamart]</p>
          <p>[http://www.store.nzfarmsource.co.nz/ Store Nzfarmsource]</p>
          <p>[https://www.adenna.com Adenna]</p>
          <p>[https://www.farmcity.co.za/ Farmcity]</p>
          <p>[https://www.crazystore.co.za/ Crazystore]</p>
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<p>9. Schmidt, S.B., Jensen, P.E., Husted, S. (2016). Manganese Deficiency in Plants: The Impact on Photosystem II. Trends in Plant Science. 21(7), 622-632. https://doi.org/10.1016/j.tplants.2016.03.001</p>
      <h3 class="title-bg">Usefull Images</h3>
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<p>10. Sinyolo, S., Mudhara, M. (2018). Farmer groups and inorganic fertilizer use among smallholders in rural South Africa. South African Journal of Science. 114 (5/6), 60-69 https://doi.org/10.17159/sajs.2018/20170083</p>
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<p>11. Tucker, T.C. (1984). Diagnosis of Nitrogen Deficiency in Plants. In R.D. Hauck (Eds.), Nitrogen in Crop Production. pp. 247-262. https://doi.org/10.2134/1990.nitrogenincropproduction.c16</p>  
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<p>12. United Nations. (2018) Women’s cooperatives boost agriculture and saving in rural Ethiopia. UN Women. https://www.unwomen.org/en/news/stories/2018/7/feature-ethiopia-cooperatives-boost-agriculture-and-savings</p>
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<p>13. Vanlauwe, B. & Dobermann, A. (2020). Sustainable intensification of agriculture in sub-Saharan Africa: first things first. Frontiers of Agricultural Science and Engineering. 7(4), 376-382. https://doi.org/10.15302/J-FASE-2020351</p>
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<p>14. Zimmer, W. & Mendel, R. (2008). Molybdenum Metabolism in Plants. Plant Biology. 1(2), 160-168. https://doi.org/10.1111/j.1438-8677.1999.tb00239.x
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      <h3 class="title-bg">References</h3>
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          <p>Espasandín-Arias, M., & Goossens, A. (2014). Natural rubber gloves might not protect against skin penetration of methylisothiazolinone. Contact Dermatitis, 70(4), 249-251. doi:10.1111/cod.12221</p>
          <p>European Commission For The Control Of Foot-And-Mouth Disease. Suggested FMD PPE guidelines - Food and Agriculture, (2016)
          Food and Agriculture Organization. Rural women in household production: Increasing contributions and persisting drudgery. (2016).
          </p>
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Latest revision as of 10:34, 30 August 2024

4.20 - Leaf colour change to diagnose fertilizer needs


Justin Huber, University of Guelph, Canada

4.20.jpeg

Suggested citation for this chapter.

Huber,J (2022) Leaf colour change to diagnose fertilizer needs. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Introduction to Nutrient Deficiency Keys

Nutrient deficiency keys use photos to show a leaf with various nutrient deficiencies plotted next to one another so a farmer can see the differences among nutrient deficiencies and compare the images to their own crops, helping diagnose fertilizer needs. For example, a woman who is growing maize can realize that the yellow discolouration in the margins of her maize leaves may mean that the soil is deficient in nitrogen (Tucker, 1984). Conversely, such photos can help smallholder farmers add only the fertilizers they need, preventing waste and improving incomes. Figure 1 is an example of a basic nutrient deficiency key.

Figure 1. Example of a nutrient deficiency key. Source: https://www.haifa-group.com/articles/main-functions-plant-nutrients

Access to fertilizer varies significantly between developed and developing nations. In 2018, Canadian farmers applied an average of 85 kg/ha and 144 kg/ha of nitrogen fertilizer for wheat and maize respectively, while Senegalese farmers in Africa only applied 18 kg/ha for wheat and 25 kg/ha for maize (Ludemann et al., 2022). In recent years, the average rate of nutrients applied to Sub-Sahara African crops has been about 16 kg/ha, which is only more than a quarter of the 2016 goal set at the 2006 Africa Fertilizer Summit of 50 kg/ha (Vanlauwe & Dobermann, 2020). Since the 2006 African Fertilizer Summit, fertilizer prices have increased by 130% due to heightened petroleum prices (Chianu et al., 2011). In 2022, fertilizer prices have increased even further (Crespi et al. 2022).

Advantages of Nutrient Deficiency Keys

Variation in soil types at the local and continental level makes diagnosing nutrient deficiencies difficult; furthermore soil testing is not available to many smallholder farmers, and there is a lack of access to government extension, resulting in inadequate farmer training which is amplified by low levels of literacy (Sinyolo & Mudhara, 2017). Nutrient deficiency keys offer a way for smallholders to identify nutrient deficiencies that do not require the help of an expensive soil testing kit or having to rely on a government extension agent. Nitrogen, potassium and phosphorus are the most common types of fertilizers (Chianu et al., 2012). However, as there are 15 fertilizers required by crops, a more comprehensive addition of fertilizers, especially in extensively degraded soils (very common in Africa) may be needed in order to increase yield, but micronutrient fertilizers (e.g. zinc, boron) can be more expensive and difficult to diagnose since they are less well-known (Chianu et al., 2012). The production of nutrient deficiency keys that are specifically for micronutrients could help smallholder farmers use a more comprehensive approach to nutrient deficiencies. Knowledge about the diagnosis of nutrient deficiencies, specifically in rural areas is significantly lacking (Chianu et al., 2012). The use of photo based nutrient deficiency keys can help educate smallholder farmers with minimal interference caused by a language barrier.

Cost vs Benefit Analysis

The most significant cause for decline of per capita food production in Sub-Sahara Africa is the decline in soil fertility (Sanchez et al., 1997), and therefore it is evident that improving fertilizer usage is vital for an increase in smallholder farmer income. Evidence of this was shown in Malawi, where farmers who used fertilizer experienced a 105% increase in yield and a 21-42% increase in profit. Smallholder farmers experience yields that are rarely above 0.5 T/ha, while commercial farms and research station trials with greater knowledge and access to fertilizer can have yields of 6-8 T/ha (Chianu et al., 2012), equivalent to a 1100-1500% increase in yield. The cost to produce the deficiency keys would be minimal. About $5 USD would be needed for language translation of a nutrient deficiency key. However, when significant numbers are being purchased, this cost would be negligible on a per farmer basis. Printing is relatively cheap, with the addition of colour adding costs at about 5 cents per key. Clear sheet covers in order to protect the nutrient deficiency keys from becoming weathered would also add about 10 cents to production. In total, the nutrient deficiency keys could easily be sold for less than 25 U.S. cents each, and with the use of fertilizer increasing yields by over 100% in some cases, the potential benefits of a nutrient deficiency key would help it pay for itself rapidly.

Distribution

Getting nutrient deficiency keys to smallholder farmers could be difficult, specifically in rural parts of Africa, as well as in politically unstable regions which may not be safe. However, there are existing methods used for other minimal cost products that help distribute to rural areas. Women’s cooperatives can be an effective method of distribution. Women’s cooperatives can have many members coming from many villages. For example, a women’s cooperative run by the United Nations in Ethiopia included about 2,000 direct beneficiaries, and almost 32,000 community members that benefited indirectly (UN Women, 2020). This extensive outreach would be an excellent way to both distribute as well as spread the word on nutrient deficiency keys.

Critical Analysis and Alternate Ways to Increase the Efficiency of Fertilizer for Subsistence Farmers

There are several factors that can render nutrient deficiency keys less useful. Some nutrient deficiencies can still decrease yields while still showing minimal to no symptoms. For example, manganese usually does not show any symptoms, unless the deficiency is severe (Schmidt et al., 2016). Some nutrient deficiencies have very similar symptoms. Molybdenum is used as a cofactor for nitrate reductase, meaning it is used to break down nitrate into nitrogen for a plant to use it (Zimmer & Mendel, 1999). So, even if there was excess nitrogen available to a crop in the form of nitrate, if there is insufficient molybdenum, the plant shows identical symptoms to a nitrogen deficiency (Cox, 1992). Similarly, cobalt and iron deficiencies can be very difficult to differentiate, as they both show chlorosis of younger leaves as their main symptom (Rathour, 2022; Anderson, 2008).

Nutrient deficiencies in trees can also be difficult to diagnose with a nutrient deficiency key. This is because, first, an important part of a nutrient deficiency key is whether newer or older leaves are affected, and second because the height of trees would make it difficult to use a nutrient deficiency key.

Symptoms very similar to that of a nutrient deficiency can also be present for other reasons. For example, Verticillium dahliae is a pathogenic fungus that causes the yellowing of older leaves (Hanson, 2000). Nitrogen deficiency also has this same symptom (Tucker, 1984). If a farmer were to use nitrogen fertilizer on this crop, it would not help get rid of the fungus, therefore potentially wasting fertilizer.

While nutrient deficiency keys will certainly help increase yields on subsistence farms, as well as educate smallholder farmers about the use of fertilizer, increased knowledge and access to fertilizer is ultimately critical for dealing with the decline in soil fertility in Africa. This issue is mainly due to minimal policy and institutional support concerning fertilizers (Chianu et al., 2012). Success of these programs and policies is not lacking evidence. Malawi has a specialized policy-led agricultural extension program concerning the use of fertilizer. This program caused more smallholder farmers to use more mineral fertilizers, resulting in a surplus of food in a county with previous food security problems (Chianu et al., 2012). The educational differences between women and men is another factor that contributes to the lack of access to fertilizer. Igbo women in Nigeria typically have little to no knowledge of fertilizer, compared to just 25% of men who do not have this knowledge (Chianu et al., 2012). Additionally, despite Africa having large deposits of raw materials, it produces only 13% of its own fertilizer, with the rest being imported, which is part of the reason that nutrients can be so expensive to African farmers (Chianu et al., 2012). Zimbabwe has provided evidence that domestic production of fertilizer can be very beneficial. Zimbabwe produces lots of its own fertilizer and as a result, uses the most fertilizer per hectare in Sub-Saharan Africa except for South Africa (Chianu et al., 2012).

Conclusion

In summary, nutrient deficiency keys can be very helpful in helping smallholder farmers to diagnose fertilizer needs for crops. However, there is no use for them if farmers have no access to fertilizers and the knowledge needed to apply them. An increase in government extension programs, women’s education and policy can all be vital to helping Africa cope with its degrading soils.

References

1. Anderson, W.B. (2008). Diagnosis and correction of iron deficiency in field crops – an overview. Journal of Plant Nutrition. 5(4), 785-795. https://doi.org/10.1080/01904168209363008

2. Chianu, J.N., Chianu, J.N., Mairura, F. (2012). Mineral fertilizers in the farming systems of sub-Saharan Africa. A review. Agronomy for Sustainable Development. 32, 545-566. https://doi.org/10.1007/s13593-011-0050-0

3. Cox, D.A. (1992). Foliar-applied Molybdenum for Preventing or Correcting Molybdenum Deficiency of Poinsettia. HortScience. 27(8), 894-895. https://doi.org/10.21273/HORTSCI.27.8.894

4. Crespi, J.M., Hart, M., Pudenz, C., Schulz, L.L., Wongpiyabovorn, O., Zhange, W. (2022). An examination of recent fertilizer price changes. Center for Agricultural and Rural Development. https://www.card.iastate.edu/products/publications/pdf/22sr117.pdf

5. Hanson, L.E. (200). Reduction of verticillium wilt symptoms in cotton following seed treatment with Trichoderma virens. Journal of Cotton Science. 4(4), 224-231. https://pubag.nal.usda.gov/catalog/30124

6. Ludemann, C.I., Gruere, A., Heffer, P., Dobermann, A. (2022). Global data on fertilizer use by crop and by country. Data Descriptor. 1(9), 501. https://doi.org/10.1038/s41597-022-01592-z

7. Rathour, S.K. (2022). Cobalt: 18th Essential Nutrient for Plant Growth? Just Agriculture. 2(7), 1-4 https://justagriculture.in/files/newsletter/2022/march/06.pdf

8. Sanchez, P.A., Sheperd, K.D., Soule, M.J., Place, F.M., Buresh, R.J., Izac, A.N., Mokwunye, A.U., Kwesiga, F.R., Ndiritu, C.G., Woomer, P.L. (1997) Soil Fertility Replenishment in Africa: An Investment in Natural Resource Capital. In R.J. Buresh, P.A. Sanchez, F. Calhoun (Eds.), Replenishing Soil Fertility in Africa. pp. 1-46. https://doi.org/10.2136/sssaspecpub51.c1

9. Schmidt, S.B., Jensen, P.E., Husted, S. (2016). Manganese Deficiency in Plants: The Impact on Photosystem II. Trends in Plant Science. 21(7), 622-632. https://doi.org/10.1016/j.tplants.2016.03.001

10. Sinyolo, S., Mudhara, M. (2018). Farmer groups and inorganic fertilizer use among smallholders in rural South Africa. South African Journal of Science. 114 (5/6), 60-69 https://doi.org/10.17159/sajs.2018/20170083

11. Tucker, T.C. (1984). Diagnosis of Nitrogen Deficiency in Plants. In R.D. Hauck (Eds.), Nitrogen in Crop Production. pp. 247-262. https://doi.org/10.2134/1990.nitrogenincropproduction.c16

12. United Nations. (2018) Women’s cooperatives boost agriculture and saving in rural Ethiopia. UN Women. https://www.unwomen.org/en/news/stories/2018/7/feature-ethiopia-cooperatives-boost-agriculture-and-savings

13. Vanlauwe, B. & Dobermann, A. (2020). Sustainable intensification of agriculture in sub-Saharan Africa: first things first. Frontiers of Agricultural Science and Engineering. 7(4), 376-382. https://doi.org/10.15302/J-FASE-2020351

14. Zimmer, W. & Mendel, R. (2008). Molybdenum Metabolism in Plants. Plant Biology. 1(2), 160-168. https://doi.org/10.1111/j.1438-8677.1999.tb00239.x

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