View source for Leaf-colour-change-to-diagnose-fertilizer-needs

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 <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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       <h1 class="title-bg">Introduction to Nutrient Deficiency Keys</h1>
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          <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>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>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>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>
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<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>

<p>http://www.sakbooks.com/uploads/8/1/5/7/81574912/5.20_south_asian_eng.pdf
-	South Asia</p>
<p>http://www.sakbooks.com/uploads/8/1/5/7/81574912/5.20east_southeast_asia_englishversion.pdf
-	East Asia</p>
<p>http://www.sakbooks.com/uploads/8/1/5/7/81574912/5.20latin_america_eng_version.pdf
-	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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       <h1 class="title-bg">References</h1>
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          <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>
<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>

<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>

<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>

<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>

<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>

<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>

<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> 

<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>

<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>

<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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