Assessment of the Agroecological State of Long-Term Irrigated Meadow-Chernozem Soil

Abstract

We examined the effect of long-term irrigation on the fertility of meadow-chernozem soil and evaluated its current agroecological state. The humus content stabilized at the average level and varied over the years of the research in the range from 4.95-5.18% in the 0-20 cm layer to 4.88-5.21% in the 20-40 cm layer. The humification degree of organic matter in irrigated soil was high, the ratio of humic and fulvic acids did not change and amounted to 1.5-1.7, the type of humus remained stably fulvate-humate. Humic acids occupy more than 50.0% of the humus and their amount did not change under the influence of irrigation. Soils are characterized by a very low content of the free fraction of humic acids, a medium content of acids linked to calcium and a high content of acids, bound to the mineral part of the soil. A redistribution of fractions was observed within the groups of humic acids. The amount of humic and fulvic acids bound to the mineral part of the soil increased by 1.2-2.0% with simultaneous reduction of humic acids linked to calcium. The content of the fraction of free fulvic acids increased. The energy potential of organic matter is at the critical level. The part of the most accessible energy is accumulated in mobile humic acids. They concentrate from 79 to 192 GJ/ha of potentially active energy. Under the influence of irrigation in the soil, a tendency for the development of secondary alkalinization was noted, as evidenced by an increase in the composition of exchange magnesium cations and an increased sodium content reaching 7%. The structural aggregation testified to the development of physical degradation. The content of aggregates with agronomic value did not exceed 45.2-59.9% and was below the optimal level. Soil aggregates were not resistant to the destructive effects of water.

Influence of organic fertilizers on the water and food regime of meadow-chernozem soil

“…Moisture reserves in the soil, their distribution is determined by many factors: the amount of atmospheric precipitation, agrohydrological and physical properties of the soil, the content of organic matter and basic nutrients, biological characteristics of plants, agrotechnical measures, including the use of mineral and organic fertilizers, various soil treatments, the placement of crops in crop rotation [6][7][8][9].…”