Soil nutrients refer to the nutrients necessary for the growth of plants provided by the soil and can be absorbed by plants directly or after transformation. Soil nutrients can be broadly divided into a large number of elements, medium and trace elements, including nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe ), Boron (B), Mo, Zn, Mn, Cu, and Cl. In natural soils, soil nutrients are mainly derived from soil minerals and soil organic matter, followed by atmospheric precipitation, slope seepage, and groundwater. In farming soils, it also comes from fertilization and irrigation.
According to the chemical forms existing in the soil, the forms of soil nutrients are divided into (1) water-soluble nutrients: dissolved ions in the soil solution and a small amount of low molecular organic compounds. (2) Replacement of nutrients: It is one of the sources of water-soluble nutrients. (3) Mineral nutrients: Most are insoluble nutrients, and some are weak acid-soluble (effective for plants). (4) Organic nutrients: The intensity of the mineralization process is different. According to the degree of difficulty in the absorption and utilization of nutrients by plants, soil nutrients can be further divided into quick-acting nutrients and delayed nutrients. In general, the available nutrients only account for a small part, less than 1% of the total amount. It should be noted that the division of available nutrients and delayed nutrients is relative, and the two are always in a dynamic equilibrium.
Soil nutrients need to be continuously replenished as they undergo complex transformations within the soil, or are absorbed and utilized by plants, leaching loss, loss of gaseousization, erosion loss, and human activities, and are slowly consumed.
Soil nutrient content varies from soil to soil and varies greatly depending on the type of soil parent material, organic matter content, and human factors. The main nutrient contents of cultivated soil in China are: nitrogen 0.03-0.35%; phosphorus (P2O5) 0.04-0.25%; potassium (K2O) 0.1-3%; other nutrient contents are usually in parts per million or hundred thousand. A few or so.
A small part of the total soil nutrient storage capacity can be quickly absorbed as an assimilation nutrient for the current crop roots, and the available nutrients are called nutrients; the vast majority of the remaining soil must be biologically or chemically converted to weigh the nutrients absorbed by the plant. Delayed nutrients. In general, the soil available nutrient content accounts for about several to several thousandths or less of the total soil nutrient storage. Therefore, in agricultural production, crops often suffer from the phenomenon of deficiency of nutrients due to insufficient supply of some effective nutrients. According to statistics, China's arable land almost completely lacks available nitrogen, nearly two-thirds of the arable land lacks available phosphorus, and one-third of the arable land lacks effective potassium, and must rely on fertilizer to make up for its deficiencies.
Therefore, the measurement of soil nutrient content has a considerable effect on the understanding of soil indicators and the rational application of fertilizer. The level of soil nutrients directly affects the growth status and harvest of crops. Local farmers and research institutes also attach great importance to soil nutrient content. Of course, domestic instruments for measuring soil nutrient content are also quite complete. Recently, high-tech near-infrared soil nutrient analyzers will also be available. When measuring soil nutrient analyzers, they have the advantage over other similar types of products. More high performance and high quality have opened up new space for agricultural instruments and brought good news to relevant people.
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