Significance of soil moisture content and mineral nutrition in intensifying assimilation and production processes in cucumber crops under drip irrigation

The level of mineral nutrition in the soil and climate conditions of the Volgograd oblast against the background of maintaining various preirrigation moisture thresholds under drip irrigation had a substantial effect (more than 50%) on the formation of leaf area during almost the entire growth period, on the photosynthetic potential of the cucumber agrocenose, net photosynthetic productivity, and average daily gain of dry biomass. It is established that differentiation of preirrigation thresholds and soil wetting horizons initiates an increase of leaf surface area depending on the level of mineral nutrition up to 20% compared to the 80-80% FC threshold and increases the photosynthetic potential up to 14%, but it has an insignificant share of effect (13.4%) in the formation and accumulation of dry matter.     

Changes in the soils of solonetzic associations in 30 years after their reclamation with the use of moldboard plowing,deep tillage with a three-tier plow,and deep rotary tillage

Changes in the properties of solonetzic soil associations (chestnut solonetzic soils and chestnut solonetzes) in the dry steppe after their reclamation have been studied for 30 years. The reclamation included the deep three-tier plowing and the approach of rotary tillage. A single rotary tillage operation resulted in the formation of fine aggregates of equal sizes in the plow layer; any morphological features of the restoration of solonetzic pedogenesis are absent. The atmospheric moisture easily penetrates into the soil, and soluble salts are leached off to a great depth. In 30 years since the soil amelioration with the use of a PMS-70 rotary tiller, the humus content has increased up to 3.3% in the upper 20-cm-thick layer and up to 2.4% in the layer of 20–40 cm. The content of adsorbed Na⁺ in the 20- to 30-cm-thick layer has decreased to 10.6% of the cation exchange capacity (in comparison with 19.8% in the nonreclaimed soil). The spatial heterogeneity of the soil cover has decreased in comparison with that prior to the reclamation. During the entire observation period, crop yields gained from the fields reclaimed with the use of the rotary tiller have been by 25–60% higher in comparison with those on the fields with traditional treatments.     

Role of external factors in increasing the efficiency of using water resources in cucumber crops with drip irrigation

The results of experimental investigations of outdoor cucumber yield formation cultivated with drip irrigation are given. It is found that, under conditions of the Lower Volga region, the maximum water-saving effect in the experimental variants is observed with maintaining the preirrigation moisture content at the level of 80% FC in the 0.3-m layer before the start of flowering, 90% FC in the 0.5-m layer during fruiting, as well as 90% FC in the 0.5-m layer during the entire period of cucumber growth with the application of mineral fertilizers in a dose of N₁₆₅P₆₅K₆₅. The investigations indicate the need for a daily irrigation dose of 30–60 m³/ha for the purpose of maintaining the soil water-air regime and providing the minimum water consumption coefficient regardless of the level of mineral nutrition.     

Impact of soil organic matter on calcium carbonate equilibrium and forms of Pb in water extracts from Kastanozem complex

Purpose

Accounting for ionic strength and ion association, the degree of calculated supersaturation with CaCO₃ of gleyic solonetz and molic solonetz soil solution is high. The purpose of the research was to reveal the effect of the water-dissolved organic matter (DOM) on the calcium carbonate equilibrium (CCE) in soil solution, to create a thermodynamic model of carbonate association and complexation with DOM and heavy metals (HMs), and to correct the principal of soil management.

Materials and methods

Object of research—Kastanozem complex of the dry steppe, Rostov Oblast, Russia. The water extraction of soluble salts was made at the water-to soil-ratio 5:1 and analyzed using standard methods. DOM content was determined by Strosser (J Agrobiol 27:49–60, 2010). The soil solution macro-ion equilibrium composition was calculated using ION-2 program (Endovitsky et al. 2009). DOM role in soil solution supersaturation with СаСО₃ was assessed, comparing C content in real solution and in identical artificial solution prepared without organic matter. Taking into account the ion association, the molar fractions of free and bound HM ion were calculated using microelement association coefficient, k_as(ME). The soil liquid-phase saturation with CaCO₃ was characterized by the ratio of the real solubility product (S) to the thermodynamic solubility product (S⁰): К?=?S/S⁰.

Results and discussion

The soil solution supersaturation with CaCO₃ was characterized by the product of analytical concentrations (S), equilibrium concentrations [accounting ion activity (S^I), ion association (S^II), ion association and complexation (S^III)], and the thermodynamic solubility product (S⁰). To evaluate the role of DOM in soil solution supersaturation with CaCO₃, the initial pure Ca (HCO₃)₂ solution series was prepared. The humic and fulvic acids from the illuvial horizon of gleyic solonetz with concentrations of 20 mg C L^?1 and 120 mg C L^?1 decreased the CaCO₃ precipitation compared with initial soil solution. The release of CaCO₃ from soil water extracts containing water-soluble organic matter was 1.2–1.9 times less compared with identical artificial solution not containing organic matter. The HM binding by carbonates is proportional to the DOM content.

Conclusions

In molic solonetz and gleyic solonetz, the neutralization of the soda should be assessed by the soil solution supersaturation with CaCO₃. To calculate the degree of HM passivation in soil solution containing DOM, the coefficient of soil solution oversaturation with CaCO₃ is proposed. For reducing soil organic matter and DOM mobility and loss from soil, as well as for Pb passivation, intra-soil mechanical processing, intra-soil waste management, and intra-soil watering are proposed.

     

Dynamics of agrophysical properties and humus content in chernozem under the moldboard, chisel and surface systems of basic soil tillage

Standard and ecologically correct agronomy system of corn based of modern soil processing devices studied. The influence of different soil processing on agrophysical properties and humus content of chernozem common revealed.     

Coefficients of association and activity of cadmium and lead ions in soil solutions

The thermodynamic calculations were made for the contents of Pb and Cd compounds in soil solutions and water extracts of the meadow-steppe and meadow solonetzes (Rostov oblast) based on their prescribed analytic concentrations of 3 and 5 μg/l, respectively. The solonetzes studied are characterized by their high carbonate content and high alkalinity. The activity of Pb²⁺ and Cd²⁺ was shown to be many times lower than their total concentration in the solution due to the association of these metals with carbonate and other anions and the formation of hydroxocomplexes CdOH⁺ and PbOH⁺. This fact is one of the reasons for the low input of Pb²⁺ and Cd²⁺ to plants growing on calcareous soils.     

Dynamics of the weed component and productivity of a grain corn agrophytocenose on ordinary chernozem under various primary tillage systems

Standard and ecologically corrected agricultural practices for a grain corn monoculture on ordinary, calcareous, moderately deep, moderately eroded chernozem with the use of the latest tilling implements are studied. The effect of primary tillage and herbicides Banvel and Milagro on the composition of the agrophytocenose and bioenergy efficiency of agricultural practice is established.     

Long-term effect of ameliorative rototilling of solonetz

An effective technology of growing crops with tilling solonetz by a PMS-70 rototiller was developed. On the basis of a long-term field experiment, a 30-year period of influence of cyclic soil ameliorative farming practices of chestnut-solonetz complex soils of the Rostov oblast is substantiated.