Optimizing application of potash
The principles for optimizing plant nutrition with potassium and application of potash fertilizers are very similar to optimizing phosphorus fertilization. Several groups of soils were identified according to the availability of exchangeable potassium, determined by the method adopted for a particular soil.
Application of potash Extracts: according to Kirsanov – 0.2 N. НСl, according to Maslova – 1 n. CH3COONH4, according to Chirikov – 0.5 n. CH3COOH, according to Machigin – 1% CH (NH4) 2CO3, according to Peive – 1.0 N. NaCl, According to Egner-Riem – lactic acid calcium.
Generalization of the results of long-term stationary experiments of the Geographic Network showed that the content of 10-15 mg К2О / 100 g of soil and the introduction of 60-90 kg К2О / ha provides crop rotation productivity of 30-50 c / ha on soddy-podzolic, gray forest soils and leached chernozems. grain units. However, the significant reserves of potassium in soils and the dynamic balance between its various forms (water-soluble, exchangeable, non-exchangeable) make the indicator of exchangeable potassium content, which characterizes the soil’s ability to provide potassium nutrition to plants, less reliable than mobile phosphorus. All forms of soil potassium are involved in the process of plant nutrition. Therefore, when characterizing soil fertility in relation to potassium, it is necessary to take into account not only easily mobile forms (potassium of soil solution and exchangeable), but also non-exchangeable potassium of primary and clay minerals, which is a reserve for replenishing exchangeable potassium in the soil, as well as the degree of mobility of exchangeable potassium, the ability and the rate of recovery of exchangeable potassium from reserve forms.
The type of clay minerals, the genetic characteristics of soils and their particle size distribution are of great importance in the supply of non-exchangeable potassium to soils. The largest amount is associated with micaceous minerals (hydromica, illite, vermiculite), less – with montmorillonite, the least – with kaolinite. In the soil, the content of potassium available for plant nutrition is usually in some equilibrium with its total reserves. But, despite the ability of the soil to restore this balance, agricultural crops are not always provided with it and there is a need for potash fertilizers. With prolonged use of fertilizers, along with an increase in the amount of exchangeable potassium in the soil, other indicators also change: the mobility of exchangeable potassium (the concentration of potassium in the low-salt CaCl2 extract, the saturation of the absorbed complex with potassium) and the proportion of exchangeable potassium in the easily hydrolyzed and non-exchangeable fractions increase. With an increase in these indicators within each soil variety, i.e. In every experiment, there is a decrease in the efficiency of “freshly applied” potassium and an increase in the aftereffect of the “residual” accumulated during the application of potash. However, on the basis of these data, it is difficult to establish criteria for the supply of potassium that are common for all soils.
There are other methodological approaches for determining the degree of soil supply with mobile potassium. Application of potash For example, this indicator can be set by the saturation of the absorbing complex with exchangeable potassium (the active level is taken from 1.8 to 3.0%). However, the value of the saturation of the soil absorbing complex with exchangeable potassium, like other indicators of the supply of potassium in soils, corresponding to the lack, excess and optimal content of potassium in the soil, should be established for each type of soil, depending on the mineralogical composition of the clay fraction of the soil and the underlying parent rock, biological characteristics of plants , conditions of nitrogen-phosphorus nutrition and moisture supply of plants, etc. In each specific case, the lower the saturation of the absorbing complex with potassium, the higher the effect of the applied fertilizers.