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Message: <blockquote data-quote="nicjosh83" data-source="post: 26985304" data-attributes="member: 569114"><p>ඔය කාබනික ලබ්බට මම විරුද්ධයි. ප්‍රශ්නේ එක නෙමෙයි.</p><p></p><p>මෙතන මේ දන්නවා වගේ හිනා වෙන උන් මොකටද හිනා වෙන්නේ, තමන්ට මද?</p><p></p><p></p><p><a href="https://journals.ashs.org/horttech/view/journals/horttech/17/4/article-p455.xml" target="_blank">https://journals.ashs.org/horttech/view/journals/horttech/17/4/article-p455.xml</a></p><p></p><h4>Potassium sulfate (K2SO4).</h4><p>When K2SO4 is derived from natural sources, it is allowed for organic crop production. Much of the current production of organically approved K2SO4comes from the Great Salt Lake in Utah. It may not undergo further processing or purification after mining or evaporation other than crushing and sieving. This product is not allowed in some European countries without special permission from the certifying agency. It generally contains ≈40% K and 17% S.</p><h4>Rock powders.</h4><p>Mined rocks, including ballast, biotite, mica, feldspars, granite, and greensand, are allowed without restriction. Tremendous variability exists in the K release rate from these mineral sources. Some of them are wholly unsuitable as K sources for plant nutrition because of their limited solubility and their heavy and bulky nature, whereas others may have value over long periods of time. In general, a smaller particle size translates to a greater surface area, reactivity, and weathering rate.</p><h4>Seaweed.</h4><p>Because sea water contains an average of 0.4 g·kg−1 K, seaweed may accumulate up to several percent K. When harvested, seaweed biomass can be used directly as a K source or the soluble K may be extracted. These K sources are readily soluble and typically contain less than 2% K. Although seaweed-derived products are excellent K sources, their low K content and accompanying transportation costs can make it problematic for field-scale use, especially far from the harvesting area.</p><h4>Sylvinite [potassium chloride (KCL)].</h4><p>KCl is restricted in the USDA standards unless it is from a mined source (such as sylvinite) and undergoes no further processing to remove sodium salts. It must be applied in a manner that minimizes Cl accumulation in the soil. Generally, KCl should only be used after consultation with the certifying agency. The Canadian CGSB has included KCl on the “permitted substances list” for organic food production systems. Unprocessed sylvinite often contains ≈17% K.</p><h4>Wood ash.</h4><p>Ash from hardwood trees served as one of the earliest sources of K for building soil fertility. This highly variable material is composed of whatever elements were initially present in the wood and were not volatilized when it was burned. Wood ash is an alkaline material, with a pH ranging from 9 to 13, and has a liming effect of between 8% and 90% of the total neutralizing value of commercial limestone. In terms of commercial fertilizer, average wood ash would have an analysis of ≈0% N, 1% P, and 4% K. The use of ash derived from manures, biosolids, coal, and some substances is prohibited for organic production. Control with the certifying organization before applying ash to soil.</p><p>Growers using organic production practices, like all growers, have a need for an adequate supply of soil K to sustain healthy and high-yielding crops. There are many excellent sources of K that are available for replacing the nutrients removed from the soil in harvested crops. Materials used as a K source for organic production must release the nutrient at a rate sufficient to meet the demand of the crop, but there are no commonly available procedures to predict this release rate. Soil minerals and crushed rocks may provide a source of K, but their release rate can be quite variable and is often inadequate prevent crop deficiency. Failure to maintain adequate K in the root zone will result in poor water use efficiency, greater pest problems, decreased harvest quality, and reduced yields. Regular soil testing for K is the key for establishing the requirement for fertilization. If a need for supplemental K exists, organic producers generally should first consider locally available K resources and supplement with mineral sources. The expense of transporting and applying low nutrient content amendments must also be considered.</p></blockquote><p></p>

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