Climate sensitivity of soil water regime of different Hungarian Chernozem soil subtypes

In this study the possible effects of two predicted climate change scenarios on soil water regime of Hungarian Calcic Chernozem soils has been investigated. Soil profiles classified as Calcic Chernozem — in total 49 — were selected from the MARTHA soil physical database that incorporates soil data at national scale. These profiles were subdivided into three groups (sandy loam, loam and clayey loam) in accordance with their mechanical composition. Soil water retention curves were scaled separately for each of the three textural groups, using similar media scaling in order to represent the variability of soil hydrophysical data with one parameter, the scaling factor (SF). Reference soil profiles were chosen according to the cumulative distribution function of the scaling factor, six for each textural group. Daily downscaled meteorological data from A2 and B2 climate scenarios of the Hadley Centre (2070–2100) and data from a reference period (RF, 1961–1990) were used in this study to characterize different climatic situations. Nine representative years were selected in case of all the three scenarios, using the cumulative probability function of the annual precipitation sum. Scenario analyses were performed, validating the SWAP soil water balance simulation model for the 18 reference soil profiles and 27 representative years in order to evaluate the expected changes in soil water regime under different from the present (RF) climatic conditions (A2 and B2 scenarios). Our results show that the scaling factor could be used as a climate sensitivity indicator of soil water regime. The large climate sensitivity of the majority of Chernozem soil subtypes water regime has been proven.     

Fractionnement et analyse des complexes organo-mineraux de sols bruns et de chernozems

Résumé Les auteurs définissent plusieurs formes de matières organiques et procèdent à leur inventaire dans des sols bruns et des chernozems. Ils effectuent un premier fractionnement par tamisage destiné à quantifier la matière végétale figurée et à séparer les complexes organo-minéraux. Ils procèdent ensuite sur ces derniers, à des extractions chimiques en vue de déterminer les complexes organométalliques et les complexes organo-argilliques. Les résultats démontrent que les sols bruns étudiés sont formés d'agrégats de consistance très lâche, caractérisés par un fort taux de complexes organométalliques à base d'acides fulviques à turn-over très rapide. Ces propriétés contrastent beaucoup avec celles des chernozems qui sont constitués d'agrégats très compacts renfermant un fort taux d'acides humiques très polycondensés, liés à un taux élevé de complexes organo-argilliques, ces deux types de produits apparaissant très résistants aux dégradations microbiennes.     

Ponded infiltration into soil with biopores — field experiment and modeling

Preferential movement of water in macropores plays an important role when the process of ponded infiltration in natural porous systems is studied. For example, the detailed knowledge of water flow through macropores is of a major importance when predicting runoff responses to rainfall events. The main objectives of this study are to detect preferential movement of water in Chernozem soil and to employ numerical modeling to describe the variably saturated flow during a field ponded infiltration experiment. The infiltration experiment was performed at the Macov experimental station (Calcari-Haplic Chernozem in Danubian Lowland, Slovakia). The experiment involved single ring ponded infiltration. At the quasi steady state phase of the experiment dye tracer was added to the infiltrating water. Then the soil profile was excavated and the penetration pattern of the applied tracer was recorded. The abundance of biopores as a product of fauna and flora was found. To quantify the preferential flow effects during the infiltration experiment, three-dimensional axisymmetric simulations were carried out by a two-dimensional dual-continuum numerical model. The water flow simulations based on measured hydraulic characteristics without consideration of preferential flow effects failed to describe the infiltration experiment adequately. The 3D axisymmetric simulation based on dual-permeability approach provided relatively realistic space-time distribution of soil water pressure below the infiltration ring.     

Soil tillage systems to reduce the harmful effect of extreme weather and hydrological situations

Soil as the largest potential natural water reservoir in the Carpathian Basin has increasing importance under conditions of predicted climate change resulting in increase of probability of extreme hydrological events. Soil management changes soil structure and has a major effect on soil water, heat and nutrition regimes. In this study the effect of four tillage treatments in combination with catch crop management was studied on soil hydraulic properties and water regime under semi-arid conditions. Investigations were carried out in a long-term soil tillage experiment established on Calcic Chernozem soil in Hungary. Tillage variants comprised mouldboard ploughing, disking, loosening combined with disking and direct drilling. The crop sequence between September 2003 and September 2004 comprised maize (main crop), rye (catch crop) and pea (forage). In May 2004, disturbed samples and undisturbed soil cores were collected from each tillage treatment/catch crop combination. The main soil physical and hydrophysical properties were determined in laboratory. In each treatment, capacitive soil moisture probes were installed up to 80 cm depth to ensure continuous measurement of soil water content. Total soil water amounts of chosen soil layers and soil water content dynamics as a function of depth were evaluated for selected periods in order to quantify the effect of the studied management systems on soil water regime. The main conclusion from the experiment is that under such (or similar) ecological conditions, the uniform, „over-standardized“ adaptation of tillage methods for soil moisture conservation is rather risky, their application needs special care and the future is for site-specific precision technologies. These are, in combination with catch crop application can be efficient measures of environmental protection and soil structure and water conservation.     

Movement and chemical distribution of isotopic nitrogen down the soil profile

Summary The downward movement and accumulation of added fertilizerin situ was studied for fine-textured, loess-terrace derived soils of Rimski Sanchevi, Navisad, Yugoslavia. Three N-treated, fallowed plots from a nitrate movement experiment were selected for this study. Soil samples were obtained upto 200 cm depth at 20 cm interval and the isotope ratio analyses were done for different forms of residual N.Fertilizer moved down the profile upto 140 cm depths and the accumulated residual N in the profile was about 55 percent of total added¹⁵N. The maximum accumulation of added fertilizer was at 0–20 cm depth (98 kg/ha) followed by 60–80 cm (32 kg/ha) depth. The fertilizer¹⁵N converted to alkali-stable (amino acid) and alkali-labile (amino sugar)-N forms were about 17 and 12 percent respectively. Only 0.41 percent of added fertilizer was converted to fixed NH₄–N. It is hoped that these findings will help the proper management of nitrogen fertilization to reduce the risk of ground water pollution.