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 <div class="title"><h3>7.4 - Water floatation to remove sick seeds before sowing</h3><br><h3 class="ch-owner">Nick Moroz, University of Guelph, Canada </h3></div>
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<p><b>Related video(s)</b>:  Seed sorting by flotation (Source: Access Agriculture)</p>
 <p><i> https://www.accessagriculture.org/seed-sorting-flotation?cat_id=1499</i></p>

<p>Suggested citation for this chapter.</p>
<p>Moroz,N. (2022) Water floatation to remove sick seeds before sowing. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org</p>
       <h3 class="title-bg">Introduction to Careful Seed Selection and Methods</h3>
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          <p>The importance of high seed quality for achieving a productive harvest cannot be overstated, especially over multiple harvest seasons. This paper will discuss what to look for in seed quality as well as describe methods on how to efficiently separate poor quality seeds from high quality seeds. In general, spotted or discoloured seeds mean diseased or unhealthy seeds (Rural Development Academy, 2006). In order to increase the yields of many grain crops globally, simple and low-cost solutions for seed quality control should be considered for farmers in developing countries (CSISA & IRRI, 2014; Mathur, Talukder, Veena, & Mortensen, 2004). The major method this paper will discuss is the Water Floatation Technique, a simple strategy that can be used to rid seed stocks or planting materials of infected or diseased seeds through separation. There are various techniques that can increase crop production by separating diseased seeds from healthy ones, including careful visual inspection of seeds or planting material and manual removal of discoloured or spotted seeds from the stock, hereby referred to as careful seed-selection (Rural Development Academy, 2006). One study in Bangladesh showed that careful seed-selection increased rice germination from 66% to 87%, increased seed quality and yields, and reduced disease and pest infestations in the local soils (Mathur et al., 2004). Similarly, the Water Floatation Technique can rapidly separate healthy, properly coloured seeds with those that are discoloured, malformed, and infected. Water floatation techniques assist in the rapid removal of sick or infected seeds, reducing the workload that is required in careful seed-selection by hand. Many farmers are currently employing water floatation techniques or careful seed inspection techniques but there are more who could benefit from these methods.</p>
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       <h3 class="title-bg">Why choosing the best seeds matters</h3>
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	<p>Farmers tend to select the best seeds over time and use them in the following seasons. Sometimes there are contaminated seeds that continue to be missed in the seed stock and unfortunately can be planted in following planting seasons, reducing yields and spreading infection (Mathur et al., 2004). This paper offers techniques to remove the contaminated seeds and maintain a fresh stockpile of healthy seeds for future planting, increasing seed germination and boosting yields over multiple years. In order to be confident in seed quality farmers must buy certified seeds or produce their own good seeds, and they should be constantly selecting for the healthy seeds, removing any infected seeds through water floatation or careful seed-selection (CSISA & IRRI, 2014). If a farmer is using their own seeds, the seeds should be clean and containing no weed seed, soil, or stones (CSISA & IRRI, 2014). Seeds must also be pure (only one variety), and healthy, meaning they are the same color with fully filled grains and free of cracks (CSISA & IRRI, 2014).</p>

<p>Supply of certified seeds is extremely limited in most developing countries, with more than 95% of the seeds used in these countries coming from the informal seed sector, mostly from farmers’ own saved grains (Mathur et al., 2004). Yields can be low due to diseased seeds that result in poor germination rates and ultimately sick, unproductive crops (Mathur et al., 2004). A crop management project that started in Bangladesh in 1998 showed that rice seed samples collected from local farmers were infected by bacteria, fungi, or disease and resulted in poor germination rates (Mathur et al., 2004). The seeds that were causing low germination rates were shown to be those seeds that visually looked discoloured or spotted (Mathur et al., 2004). After careful seed-selection and manual removal of these spotted seeds, germination rates of the rice seed increased to rates of 87% on average compared to 66% on average in the original (or unaltered) seed stock samples (Mathur et al., 2004). For a thorough explanation of the methods of this study see Mathur et al. (2004). Mathur et al. (2004) results show that rice seed samples that contained the discoloured or spotted seeds had low germination and poor looking seedlings compared to the carefully selected seeds (see Table 1.0). Discolouration and spots on rice seeds are coloured due to infectious fungi and bacterial infections (Mathur et al., 2004; Singh & Rao, 1977; Rural Development Academy, 2009), and the germination of such infected seeds is diminished. Thus, this paper proposes that simple manual removal of seeds through careful selection or by water flotation techniques will greatly benefit farmers by improving their seed stores and crop health and productivity</p>
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<p>The recommendations proposed by Mathur et al. (2004) would increase the healthy seedlings of rice per hectare over multiple years, but also resulting in lower contamination of disease organisms in planting soils (Mathur et al., 2004). Over the years there would be less seed and soil-borne infectious organisms in areas that practice careful seed-selection either manually or by water floatation (Mathur et al., 2004). Higher quality grains and increase yields will ultimately generate greater incomes for famers that can only access their own seedlings (Mathur et al., 2004; Rural Development Academy, 2009).</p>
<p>In order to assess and improve the quality of their own seed, farmers can employ the germination test and then employ the water flotation technique to select for the higher quality seeds from the original stock (CSISA & IRRI, 2014). These two methods are briefly outlined as follows:</p>
<p>1.	The Germination test (or Between Paper, BP, method): This test involves carefully placing seeds on a wet rag and rolling the rag around a stick laid across the rag for support, while leaving the seeds undisturbed and inside the wet rag (CSISA & IRRI, 2014). After five days, unroll the rags and count the number of seeds with roots (CSISA & IRRI, 2014). The number of sprouted seeds represents the germination rate, with a rate of 70% or less being very unfavorable (CSISA & IRRI, 2014). It is the unhealthy and diseased seeds that will not germinate, lowering the germination rate of a sample. See CSISA document in the Reference List or the paper by Mathur et al. (2004) for more details.</p>
<p>2.	Water Floatation Technique: ensure you have quality seeds for planting before soaking your seeds for germination or planting (CSISA & IRRI, 2014). Place seeds for planting into a bucket containing clean water and stir gently. Discard all grains that float to the surface (CSISA & IRRI, 2014). Carefully sort seeds and remove floating seeds, which are infected or deformed seeds, and extract all empty or partially filled grains (CSISA & IRRI, 2014). See the water floatation video in the Resources Moving Forward Section or Reference List for more details. More extensive credible water flotation information and research follows directly below.</p>
<p><b>The Water Floatation Technique</b></p>
<p>The water floatation technique involves separating hollow, diseased, or partially filled seeds from healthy seeds using water or salt water (Rural Development Academy, 2009). As seen in a video by the Rural Development Academy (2009) in collaboration with the International Rice Research Institute, after placing seeds into a bucket of clean water, unfilled or partially filled seeds will float to the surface because they are lighter. Following this separation, remove the floating seeds while keeping those that sunk to the bottom (Rural Development Academy, 2009). Washing with salt water can then refine this seed-selection, as infected partially filled seeds, which are harder to remove via unsalted water floatation, will float in salt water, when enough salt is added that a raw egg will float (Rural Development Academy, 2009). These seeds can then also be removed, resulting in only clean seeds that should be washed with freshwater and then dried before planting (Rural Development Academy, 2009). Rural Development Academy (2009) and CSISA & IRRI (2014) accredit this technique for increasing seed quality and maximizing the speed of selection.</p>
<p>Sivakumar et al. (2007) also showed that seed flotation techniques are not necessarily limited to water flotation, but that petroleum ether flotation techniques also were extremely advantageous in improving seeds germination percentages in certain seeds. They tested the viability of petroleum ether as a separation medium to increase the germination of Casuarina equisetifolia Forst seed lots. Petroleum flotation resulted in 90% germination in the sunken fraction and 4% in the floating fraction (Sivakumar et al., 2007). The percentage of seeds discarded as floaters that germinated was remarkably low in this study (Sivakumar et al., 2007). Thus, petroleum flotation appears to be able to increase the germination of C. equisetifolia seed lots through flotation and seed-separation, although its efficacy is influenced by variables such as wing surface area and seed density of filled and empty seeds. (Sivakumar et al., 2007). Sivakumar et al. (2007) showed that new techniques, such as the use of petroleum ether for flotation, could enhance seed floatation procedures, given the proper seeds and conditions.</P>
<p><b>Limitations of Floatation Method</b></p>
<p>There is a natural degree of seed variation that will be observed while farming, including within the seed morphology (colour, size, and weight), seed germination (viability, germination percent, etc.) and seedling growth parameters (survival percentage, seedling height, seedling biomass, etc.) (Ginwal, Phartyal, Rawat, & Srivastava, 2005). Farmers should understand this natural variability and select the seeds with the desired traits, looking for major discrepancies that indicate a diseased seed from a normal one. Furthermore, germination of seeds can be strongly influenced by genetic control and the heritability of genetic components, which can be exploited to increase germination rates of certain species (Ginwal et al., 2005). As such, farmers should not only look at careful seed-selection and water floatation as the only factor that can influence high germination or crop yields, especially across all grain crops and in all environments. Despite this variability, water floatation and seed-selection are proven techniques.</p>
<p>Another limitation of the water floatation technique is the potential for loss of viable seeds in the discarded fraction, reducing the genetic diversity of seed lots (Sivakumar et al., 2007). However, this can be addressed by carful seed-selection and following the procedures of these flotation techniques. However, floating seeds are proven to have a very low probability (sometime only 4%) to be capable of germination and are generally undesirable or diseased (Sivakumar et al., 2007; Mathur et al., 2004; Singh & Rao, 1977). The advantage of petroleum flotation techniques is the accuracy of the technique. The proportion of germinable seeds discarded as floaters is remarkably low, at 4% (Sivakumar et al., 2007). This is an important advantage, as a high loss of viable seeds in the discarded fraction as floaters may not be economical, and would reduce genetic diversity of the seed lot (Sivakumar et al., 2007).</p>
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       <h1 class="title-bg">Picture Based Lesson to Train Farmers</h1>
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[[Image:8.4.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><i>For the South Asian version (pictures only, text for you to insert), click this link for lesson 8.4:http://www.sakbooks.com/uploads/8/1/5/7/81574912/8.4_south_asian.pdf</i></p>
<p><i>For the East/South Asian version (pictures only, text for you to insert), click this link for lesson 8.4:http://www.sakbooks.com/uploads/8/1/5/7/81574912/8.4e.s.a.pdf</i></p>
<p><i>For the Sub-Saharan Africa/Caribbean version (pictures only, text for you to insert), click this link for lesson 8.4:http://www.sakbooks.com/uploads/8/1/5/7/81574912/8.4subsaharan_africa_carribean.pdf</i></p>
<p><i>For the Latin-America version (pictures only, text for you to insert), click this link for lesson 8.4:http://www.sakbooks.com/uploads/8/1/5/7/81574912/8.4latin_america.pdf</i></p>
<p><i>For North Africa And Middle East version (pictures only, text for you to insert), click this link for lesson Chapter 5. 7.4:http://www.sakbooks.com/uploads/8/1/5/7/81574912/7.4n._africa_middleeast.pdf</i></p> 
<p><i>Source: MN Raizada and LJ Smith (2016) A Picture Book of Best Practices for Subsistence Farmers:  eBook, University of Guelph Sustainable Agriculture Kit (SAK) Project, June 2016, Guelph, Canada. Available online at: www.SAKBooks.com</i></p>
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       <h3 class="title-bg">Resources Moving Forwards and Video Protocols for Removing Discoloured/Spotted Seeds: </h3>
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<p>Hand Picking and Water Floation Technique Videos:</p>

<p>1. Seed Flotation [TECAxFAO YouTube video]: https://www.youtube.com/watch?v=e6G8bU9OkqE</p>
<p>2. Spotted Seeds Means Diseased Seeds [IRRI YouTube video]: http://www.youtube.com/watch?v=0NKVCNyPwuI</p>
<p>IRRI is the International Rice Research Institute. Please see the YouTube Video description to get more information on how to get this video on multiple formats. Other useful videos for subsistence farmers are provided by TECAxFAO and IRRI on YouTube.</p>
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       <h3 class="title-bg">References </h3>
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<p>1.Cereal Systems Initiative for South Asia Phase II (CSISA) and International Rice Research Institute (IRRI). (2014). 8 tips for higher rice yields in Odisha (Oriya). Retrieved from http://pdf.usaid.gov/pdf_docs/PA00K83Q.pdf</p> 
<p>2.	Ginwal, H. S., Phartyal, S. S., Rawat, P. S., & Srivastava, R. L. (2005). Seed source variation in morphology, germination and seedling growth of Jatropha curcas Linn. in central India. Silvae genetica, 54(2), 76-79.</p> 
<p>3.Mathur, S. B., Talukder, M. H., Veena, M. S., & Mortensen, C. N. (2004). Effect of manual cleaning on health and germination of rice seeds. Seed Science and Technology, 32(2), 405-415.</p> 
<p>4.Rural Development Academy, Bogra, International Rice Research Institute, and CAB International (Producer), & unknown (Director). (2009). 2 Seed Flotation [YouTube video]. (Available from TECAxFAO on YouTube). Retrieved from https://www.youtube.com/watch?v=e6G8bU9OkqE</p> 
<p>5.Rural Development Academy, Bogra, International Rice Research Institute, and CAB International (Producer), & unknown (Director). (2006). Spotted Seeds Means Diseased Seeds [YouTube video]. (Available from International Rice Research Institute on YouTube). Retrieved from http://www.youtube.com/watch?v=0NKVCNyPwuI</p> 
<p>6.Singh, R. A., & Rao, M. H. S. (1977). A simple technique for detecting Xanthomonas oryzae in rice seeds. Seed Science and Technology, 5(1), 123-127.</p> 
<p>7.Sivakumar, V., Anandalakshmi, R., Warrier, R. R., Singh, B. G., Tigabu, M., & Oden, P. C. (2007). Petroleum flotation technique upgrades the germinability of Casuarina equisetifolia seed lots. New forests, 34(3), 281-291.</p>