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The article gives a comparative assessment of the impact of various fertilizer systems and soil tillage methods on the productivity of crop rotation and the economic effectiveness of using fertilizer systems within the framework of the SSAU long-term station. Since 1976, in the field crop rotation of the permanent station, the influence of systematic annual complex application of fertilizers, soil treatment methods on the productivity of agricultural crops of 8 fields rotation and the fertility of leached chernozem have been studied. Held between 1978 and 2018, the research has shown that the studied fertilizer systems and methods of tillage give the crop rotation sustainable productivity, preserve and increase the soil fertility, and predetermine the increasing productivity trend. On leached chernozem, moldboard and nonmoldboard methods of tillage to a depth of 20-22 cm are recommended, as ensuring optimal agrochemical soil condition, maximum productivity of crop rotation and the highest economic effect. The saturation of crop rotation with organic fertilizers gave the soil significant moisture storage functions: lower limit of 5 t•ha-1 of manure, from which the moisture storage functions of leached chernozem began to be optimized, regardless of the methods of placing scraps in the soil; the upper limit (7.5 or more t•ha-1), the effectiveness of which was determined by the methods and the depth of placement of the scraps in the soil. In order to preserve the soil fertility to obtain the average annual productivity of grain cultivation crop rotation 3.5-4.4 t•ha-1 grain unit, a biologized fertilizer system with a saturation of 1 ha of the crop rotation area N43Р20К0 + 9.0 t•ha-1 of organic fertilizers is recommended, and for obtaining programmable crop yields and crop productivity of 4.5-5.3 t•ha-1 grain unit, a fertilizer design system with a saturation of 1 ha of the crop rotation area N86Р74К11 + 5.0 t•ha-1 of manure is preferred.

The influence of frequency dispersion of conductivity (induced polarization) of rocks on the results of electromagnetic (EM) sounding was studied on the basis of calculation of electric field of vertical magnetic dipole above horizontally layered polarizable sections. Frequency dispersion was approximated by the Debye formula. Polarizable homogeneous halfspace, two, three and multilayered sections were analyzed in frequency and time domains. The calculations for different values of chargeability and time constants of polarization were performed. In the far zone of a source, the IP of rocks led to quasi-wave phenomena. They produced rapid fluctuations of frequency and transient sounding curves (interference phenomena, multireflections in polarizable layers). In the case of transient sounding in the near zone of a source quasistatic distortions prevailed, caused by the counter electromotive force arising in polarizable layers which may lead to strong changes in transient curves. In some cases quasiwave and quasistatic phenomena made EM sounding curves non-interpretable in the class of quasistationary curves over non-dispersive sections. On the other hand, they could increase the resolution and depth of investigation of EM sounding. This was confirmed by an experience of "high-resolution" electroprospecting in Russia. The problem of interpretation of EM sounding data in polarizable sections is nonunique. To achieve uniqueness it is probably necessary to complement them by soundings of other type.

The possibilities and limitations of the induction sounding (TEM method) in the permafrost zone for solving hydrogeological problems are described. On the one hand the fresh water promising layer must have increased electrical resistivity (sand layer in the clay section). On the other hand, it should be a talik zone and should have a lower electrical resistivity in comparison with the surrounding frozen rocks. In the context of such ambiguity, it is important to use additional independent information to take informed decisions in the data interpretation. Such information capabilities are provided by fast-decaying induced polarization associated only with the frozen state of rocks. A number of examples show the effectiveness of the TEM method taking into account fast-decaying induced polarization for complex geocryological conditions of the polar part of Western Siberia.