[:is]Microorganisms play an important role in processes that affect the transformation of phosphorus in the soil and its availability to plants.\u00a0<\/b>In particular, they can solubilize and mineralize organic and inorganic forms of phosphorus through mechanisms such as the release of organic acids and hydrolytic enzymes that increase the mobilization and availability of this element for plant nutrition.<\/p>\n
Most soils are deficient in phosphorus.<\/b><\/u>\u00a0In addition, the permanent use of chemical fertilizers represents a significant cost for agriculture in the world.<\/b><\/p>\n
The use of microorganisms as inoculants to mobilize poorly available phosphorus sources in the soil constitutes an alternative to reduce environmental contamination and improve crop productivity<\/a>.\u00a0<\/b> Some of these microorganisms can combine resulting in synergistic effects when applied together.<\/b><\/u>\u00a0<\/b><\/u>(hence the importance of having\u00a0SPECIALIZED ADVICE<\/a>\u00a0like the one we lend from\u00a0IDEAGRO<\/a>, providing solutions and protocols to improve performance and in favor of a more sustainable agriculture).<\/i><\/b>\u00a0The use of biofertilizers originates fast processes, consume little energy and do not pollute the environment.\u00a0Its use represents an important alternative for\u00a0<\/i>Limit the use of chemical fertilizers, which are less economically profitable, while reducing their negative environmental impact and improving crop productivity.<\/b>\u00a0In turn, biofertilizers can be very useful in the recovery of marginal land for agricultural and forestry use.<\/p>\n Most of the soils are deficient in phosphorus and the availability of this element for the plants is scarce, therefore the application of fertilizers is required to maintain high levels of productivity.<\/b><\/p>\n The need for alternative searches that help minimize their adverse effect on the environment and the increasing availability of phosphorus for plants is of great interest today for agriculture; thus,\u00a0the use of microorganisms that solubilize phosphorus through different mechanisms and their inoculation in high concentrations in relation to those normally found in the soil constitutes an advantage for their use as biofertilizers<\/b>\u00a0improving growth conditions in plants. Many of the soil microorganisms have the ability to stimulate plant growth.<\/b>\u00a0With the intention of reducing chemical fertilizers, microorganisms with a beneficial effect on plants have considerable potential as biofertilizers and biocontrol agents.\u00a0Three large groups can be distinguished: nitrogen fixers; mycorrhizal fungi and plant growth promoters, among which we find bacteria and fungi.<\/b>\u00a0The bacteria are known as plant growth promoting rhizobacteria (PGPR).<\/b><\/u>\u00a0This designation refers to free-living bacteria that are located very close to or inside the roots of plants and have a beneficial effect on plant growth. These bacteria have been found in association with the roots of numerous plant species, and have even been reported in marine environments (mangroves).<\/p>\n Among the most distinctive characteristics that define the PGPR are the following:<\/i><\/u><\/p>\n \u2022 do not require internal invasion of tissues in plants, as occurs in mycorrhizal fungi with the formation of arbuscules or nodules in the case of Rhizobium<\/p>\n \u2022 It is important that they have a high population density in the rhizosphere after their inoculation, since a rapidly declining population has a low competitive capacity with the native soil microflora.<\/p>\n \u2022 They must have an effective colonization capacity on the root surface and, as a consequence, positively influence the growth of the plant.<\/p>\n \u2022 that do not cause any harm to humans.<\/p>\n Plant growth may be, in part, a product of the ability of rhizobacteria to aid their continued development, through different mechanisms.<\/b>\u00a0Among the main mechanisms we can cite:\u00a0biological nitrogen fixation<\/b><\/a>, the\u00a0phosphorus solubilization<\/b>, the production of\u00a0iron chelators<\/b>, the production of\u00a0phytohormones<\/b>\u00a0that trigger responses and key reactions in plant growth, as well as the stimulation of this growth indirectly by the synthesis of the enzyme ACC deiaminase and the\u00a0inhibition of the growth of phytopathogenic microorganisms<\/b>\u00a0through substances that are exuded into the soil such as: antibiotics, siderophores and enzymes with lytic activity on the wall of many fungi and bacteria.<\/p>\n within the\u00a0microorganisms that promote plant growth<\/a>\u00a0we can find strains of different genera such as Pseudomonas, Azospirillum, Bacillus, Enterobacter, Rhizobium, Burkholderia and Erwinia among others.<\/b><\/p>\n Peculiarities of microbial inoculants<\/b><\/p>\n Growth-promoting bacteria constitute an interesting alternative to promote mineral nutrition in plants, increase crop productivity, and in turn are easier to modify by molecular biology techniques than a highly complex organism. In each case, a greater knowledge of the characteristics of the microorganisms is necessary to then design methods to introduce inoculants as persistent components of the soil microflora.\u00a0It is worth highlighting the great advantage offered by "multifunctional" microorganisms: microorganisms known for their beneficial qualities for plants, to which the capacity for new characters of interest can be transferred through genetic manipulation, with a view to bringing together in the same strain, various factors that promote plant growth.<\/b> Phosphorus is one of the chemical elements essential for life.<\/b>\u00a0It is part of nucleic acids (DNA and RNA), ATP and other molecules that have the phosphate ion and store chemical energy, it is also part of the phospholipids that integrate and give flexibility to cell membranes, and bones and animal teeth.\u00a0It is in small amounts in plants, in proportions of approximately 0.2 %, and in animals up to 1 % of its mass can be phosphorus.<\/b><\/p>\n Its fundamental reserve in nature is the earth's crust.\u00a0In general, agricultural soils contain good stores of phosphorus as a result of the regular application of fertilizers, but its availability to the plant is poor due to chemical processes that "fix" the soluble phosphorus in fertilizers in insoluble forms unsuitable for growth. vegetal Nutricion<\/b>, for example the formation of calcium phosphates in alkaline soils and iron and aluminum phosphates in acid soils.\u00a0Phosphorus is found in soils in both organic and inorganic forms. Between 50 and 80 % of organic phosphorus is made up of phytic acid.<\/b>\u00a0Phosphorus is absorbed by plants almost exclusively in the soluble form, represented by phosphate anions.\u00a0<\/b><\/u>The concentrations of these anions in solution are around 1 and 10 \u03bcM in equilibrium with the solid phase of the soil. This way,\u00a0dissolved inorganic phosphorus meets crop demand for a few hours during the growing period<\/b><\/u>, considering that these amounts are extremely small compared to those necessary for the biological processes associated with optimal plant growth.<\/p>\n Importance of phosphorus solubilization in biofertilizers<\/b><\/p>\n Phosphorus solubilizing microorganisms constitute up to 40 % of the soil bacteria population and a significant portion of them are isolated from the rhizosphere.<\/b><\/p>\n Numerous studies have shown that the response of plants to microbial inoculation in many cases has been attributed to improving the acquisition of phosphorus by them. This has generated a range of\u00a0microorganisms with broad potential to increase phosphorus availability<\/b><\/u>, which have been identified and characterized. Within these isolates we find fungi such as Aspergillus niger and bacteria such as Bacillus sp. and Pseudomonas sp.<\/p>\n An example in this sense is the\u00a0co-inoculation<\/b>\u00a0of Pseudomonas striada and Bacillus polymyxa, with\u00a0nitrogen-fixing microorganisms<\/a>\u00a0as is the case of Azospirillum brasilense; This experiment led to the\u00a0optimal accumulation of nitrogen and phosphorus necessary for the growth of the studied plants<\/b><\/u>, when the inoculation was carried out with the microorganisms separately, a completely different result was shown.<\/p>\n Microorganisms can also interact with each other, giving rise, in many cases to synergistic interactions that favor plant growth.<\/b><\/p>\n An example of this synergism is the interaction between mycorrhizae: a symbiosis formed by certain soil and root fungi and phosphorus solubilizing microorganisms.<\/b>\u00a0Mycorrhizae have typical nutritional exchange structures inside the root and an abundant network of mycelium outside it, which allows the root to explore the soil more extensively and make better use of low-mobility elements such as phosphorus.<\/p>\n Phosphorus solubilizing microorganisms play an important role in the acquisition of phosphorus by plants. This nutrient is considered one of the most limited in our agriculture and of great importance for the vegetal Nutricion<\/a>.<\/b><\/p>\n
\nThe\u00a0biofertilizers<\/a>\u00a0or biological fertilizers are based on microorganisms that promote and benefit the nutrition and growth of plants.<\/b>\u00a0These are soil microorganisms, generally fungi and bacteria, which are naturally associated with plant roots in a more or less intimate way. These microorganisms can directly or indirectly facilitate the availability of certain nutrients such as: nitrogen, phosphorus and water, in addition to producing substances called phytohormones that promote plant growth.<\/p>\n
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\n<\/b>Microbial inoculants. mechanisms<\/b><\/p>\n
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\nAlthough prospects for developing microbial inoculants that improve phosphorus mobilization from soil have been proposed for several decades, it is evident that the proposal is highly problematic. In fact, it is arguable that the chances of success can be improved with greater knowledge of the key processes and agencies involved. However,\u00a0the complexity of the interaction between microorganisms and plants in the soil seems to be the biggest obstacle\u00a0<\/b>(thus,\u00a0At IDEAGRO we have our own laboratory<\/a>\u00a0and facilities in which to develop and work with our bacterial strains that we then apply in the field to evaluate their adequate performance)<\/b>.<\/i>\u00a0In this sense, the genetic manipulation of microorganisms and plants could increase the capacity to mobilize poorly available phosphorus sources.<\/p>\n
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\n<\/b>Phosphorus: essential element for life<\/b><\/p>\n