Soil compaction causes important physical modifications at the subsurface soil, especially from 10 to 30 cm depths. Compaction leads to a decrease in infiltration rates, in saturated hydraulic conductivity, and in porosity, as well as causes an increase in soil bulk density. However, compaction is considered to be a frequent negative consequence of applied agricultural management practices in Slovakia.
Detailed determination of soil compaction and the investigation of a compaction impact on water content, water penetration depth and potential change in water storage in sandy loam soil under sunflower (Helianthus annuus L.) was carried out at 3 plots (K1, K2 and K3) within an experimental site (field) K near Kalinkovo village (southwest Slovakia). Plot K1 was situated on the edge of the field, where heavy agricultural equipment was turning. Plot K2 represented the ridge (the crop row), and plot K3 the furrow (the inter–row area of the field). Soil penetration resistance and bulk density of undisturbed soil samples was determined together with the infiltration experiments taken at all defined plots.
The vertical bulk density distribution was similar to the vertical soil penetration resistance distribution, i.e., the highest values of bulk density and soil penetration resistance were estimated at the plot K1 in 15–20 cm depths, and the lowest values at the plot K2. Application of 50 mm of water resulted in the penetration depth of 30 cm only at all 3 plots. Soil water storage measured at the plot K2 (in the ridge) was higher than the soil water storage measured at the plot K3 (in the furrow), and 4.2 times higher than the soil water storage measured at the most compacted plot K1 on the edge of the field. Results of the experiments indicate the sequence in the thickness of compacted soil layers at studied plots in order (from the least to highest compacted ones): K2–K3–K1.
This study tested the hypothesis that the changes in hydrophysical parameters and heterogeneity of water flow in an aeolian sandy soil have the same trend as the process of succession. Three sub-sites were demarcated at the area of about 50 m x 50 m. The first sub-site was located at the pine-forest glade covered with a biological soil crust and represented the initial stage of succession. The second sub-site was located at the grassland and represented more advanced stage of succession. The third sub-site was located at the pine forest with 30-year old Scots pines and represented advanced stage (close to climax) of succession. The sandy soil at the surface was compared to the soil at the pine-forest glade at 50 cm depth, which served as a control because it had a similar texture but limited impact of vegetation or organic matter. It was found that any type of vegetation cover studied had a strong influence on hydrophysical parameters and heterogeneity of water flow in an aeolian sandy soil during hot and dry spells. The changes in some hydrophysical parameters (WDPT, R, k(-2 cm), Sw(-2 cm), ECS and DPF) and heterogeneity of water flow in an aeolian sandy soil had the same trend as the process of succession, but it was not so in the case of Ks and Se(-2 cm), probably due to the higher content of smaller soil particles in grassland soil in comparison with that content at other sub-sites. Both the persistence and index of water repellency of pure sand differed significantly from those of grassland, glade and forest soils. The highest repellency parameter values in forest soil resulted in the lowest value of both the water sorptivity and hydraulic conductivity in this soil in comparison with other soils studied. The highest value of ethanol sorptivity and the lowest value of saturated hydraulic conductivity in the grassland soil in comparison with other soils studied were due to the higher content of fine-grained (silt and clay) particles in the grassland soil. The effective cross section and the degree of preferential flow of pure sand differed significantly from those of grassland, glade and forest soils. The change in soil hydrophysical parameters due to soil water repellency resulted in preferential flow in the grassland, glade and forest soils, while the wetting front in pure sand area exhibited a form typical of that for stable flow. The latter shape of the wetting front can be expected in the studied soils in spring, when soil water repellency is alleviated substantially., The columnar shape of the wetting front, which can be met during heavy rains following long dry and hot spells, was attributed to redistribution of applied water on the surface to a series of micro-catchments, which acted as runon and runoff zones., V príspevku sa testovala hypotéza, že zmeny hydrofyzikálnych parametrov a heterogenita prúdenia vody v piesočnatej pôde majú rovnaký trend ako proces sukcesie. Na ploche asi 50 m x 50 m sa vytýčili tri parcely. Prvá parcela sa nachádzala na čistine pokrytej biologickým pôdnym pokryvom a reprezentovala počiatočné štádium sukcesie. Druhá parcela sa nachádzala na zatrávnenej ploche a reprezentovala rozvinutejšie štádium sukcesie. Tretia parcela sa nachádzala v borovicovom lese a reprezentovala rozvinuté štádium sukcesie (blízke ku klimaxovej vegetácii). Piesočnatá pôda na povrchu parciel sa porovnávala s pôdou z čistiny v hĺbke 50 cm, ktorá slúžila ako kontrola, pretože mala skoro rovnakú textúru, avšak veľmi malý vplyv vegetácie alebo organickej hmoty. Zistili sme, že akýkoľvek typ študovaného vegetačného pokryvu mal veľký vplyv na hydrofyzikálne parametre a heterogenitu prúdenia vody v piesočnatej pôde počas horúcich a suchých období. Zmeny niektorých hydrofyzikálnych parametrov (WDPT, R, k(-2 cm), Sw(-2 cm), ECS a DPF) a heterogenity prúdenia vody v piesočnatej pôde mali rovnaký trend ako proces sukcesie, neplatilo to však v prípade Ks a Se(-2 cm), pravdepodobne v dôsledku vyššieho obsahu malých pôdnych častíc v pôde s trávnatým pokryvom v porovnaní s inými parcelami. Stálosť aj index vodoodpudivosti čistého piesku sa štatisticky významne líšili od hodnôt týchto parametrov v pôde pod trávou, biologickým pôdnym pokryvom a borovicami. Najvyššie hodnoty parametrov vodoodpudivosti v tráve pod borovicami mali za následok najnižšie hodnoty sorptivity pre vodu a hydraulickej vodivosti v tejto pôde v porovnaní s ostatnými študovanými pôdami. Najvyššie hodnoty sorptivity pre etanol a najnižšie hodnoty nasýtenej hydraulickej vodivosti v pôde pod trávou v porovnaní s inými pôdami boli pravdepodobne spôsobené vyšším obsahom malých pôdnych častíc v tejto pôde. Efektívny prierez (ECS) a stupeň preferovaného prúdenia (DPF) čistého piesku sa štatisticky významne líšili od hodnôt týchto parametrov v pôde pod trávou, biologickým pôdnym pokryvom a borovicami. Zmeny hydrofyzikálnych parametrov pôdy v dôsledku jej vodoodpudivosti mala za následok preferované prúdenie v pôde pod trávou, biologickým pôdnym pokryvom a borovicami, zatiaľ čo čelo omáčania v čistom piesku malo tvar typický pre stabilné prúdenie. Takýto tvar čela omáčania možno vo všetkých študovaných pôdach očakávať na jar, keď je vodoodpudivosť pôdy podstatne znížená v dôsledku jej zvýšenej vlhkosti., and Čelo omáčania v tvare prstov, ktoré možno očakávať počas prívalových dažďov nasledujúcich po dlhých suchých a horúcich obdobiach, možno pričítať redistribúcii vody na povrchu pôdy do viacerých mikropovodí, ktoré sa správali ako vtokové a odtokové oblasti