There are marked differences in the pH values determined in water suspension under laboratory conditions and in soil solution under field conditions in hydromorphic soils (gleysols and stagnosols). The value δpH = pHsusp–pHsol can be either positive or negative. Among the main factors that affect the value of δpH are the laboratory preparation of soil samples and the suspension effect. The sign of the pH effect (value of δpH) depends on the participation of humus, carbonate, and exchange bases in the formation of aggregates destructed in the laboratory. The value of δpH is negative in noncalcareous soils with low content of exchangeable bases and fulvate composition of humus and positive in calcareous soils or soils enriched with exchangeable bases and humate composition of humus. In cases of a significant δpH effect, the value of pHsusp cannot be regarded as an adequate measure of soil acidity.

Nitrates from soil and nitrogen fertilizers unused by plants become hazardous pollutants and contaminate surface and ground waters. In the water-saturated layers, into which nitrates are leached, the content of organic matter (i.e., electron donors necessary for nitrification) can be insufficient. The deficiency of electrons in the groundwater can be eliminated by Fe(II) minerals that remained in the heavy rocks and are available to microorganisms due to dispersion. However, when the groundwater table is shallow (less than at 10 m), the natural denitrification develops poorly; therefore, remediation is needed to enrich the contaminated water with electron donors. Zerovalent iron is most frequently used for this purpose. The efficiency of the Fe-0 barriers for the purification of groundwater from nitrates increases due to the activation of anaerobic denitrifying bacteria. In addition, the geochemical conditions and the composition of the bacterial community change in the Fe-0 barrier zone, which favors the development of a wide range of anaerobic hydrogenotrophic bacteria (primarily Fe(III) reductants).

According to the data of a long-term stationary experiment, the application of an organo-mineral system of fertilizers in combination with periodic liming significantly improves physical and chemical properties, calcium state, cation exchange capacity, and buffer capacity of soil. In this case, each next application of liming prolongs the liming aftereffect. It is important to consider these results for the use of agrochemical methods in a crop rotation.

Various organochlorine compounds such as pesticides, insecticides, plant growth regulators, fumigants, and others are used in agriculture. Because of the presence of chlorine, these compounds are dangerous pollutants, which contaminate soils and surface and ground waters. For the degradation of organochlorine pollutants, zero-valent (metallic) iron Fe0, an inexpensive reducer, is used. The activity of Fe0 decreases with time; therefore, for its restoration, the surface layer of Fe(III) (hydr)oxides is removed necessary to. For this purpose, the surface of Fe0 nanoparticles is modified, and mineral activators of hydrogenation (e.g., Ni) are added. Under anaerobic conditions, the activity of metallic iron is reduced by Fe-reducing bacteria. The Fe0 barrier work period is extended by active corrosion products, primarily green rust: Fe(II)/Fe(III) layered double hydroxides with different interlayer anions. Positive results for the degradation of organochlorine compounds have been obtained.

It is shown that aerobic-anaerobic equilibrium in the structure of the microbial community of soils promotes preservation of organic carbon when organic fertilizers (vermicompost) are applied. Changes in the structure of the microbial community under legume crops occur as a result of an increase in numbers of aerobic and anaerobic species of the nitrogen cycle (free-living and associative) and carbon cycle.

The long-term application of physiologically acid nitrogen and potassium fertilizers without liming deteriorated the physicochemical properties of soddy-podzolic soil and increased the mobility of iron. The application of phosphoric fertilizers resulted in the formation of iron phosphates and other complex compounds, which decreases the mobility of iron. A specially significant decrease in iron mobility in the soil studied was observed at the application of mineral fertilizers together with liming or upon the application of mineral and organic fertilizers in combination with periodic liming. The crystallization of amorphous iron was slower in this case.

In 1883, the major work of Dokuchaev-Russian Chernozem-was published. This book brought Dokuchaev world fame as the founder of pedology. His book Our Steppes in the Past and at Present that appeared in 1892 contributed much to the theory and practice of Russian agronomy.

Высокопродуктивная агроэкосистема на слабоокультуренной дерново-подзолистой почве с оптимальными параметрами показателей ее плодородия была создана при длительном (40 лет) комплексном применении агрохимических средств с обязательным периодическим известкованием. Она устойчиво сохраняла положительные свойства на фоне 10-летнего последействия агрохимических средств. Длительное одностороннее применение минеральных удобрений в этом случае усиливало проявление негативных свойств данной почвы.