| Abstract [eng] |
The work analyzes the archival data of erosion stationaries and the experiments, which were carried out in two soil erosion stationaries of the Vėžaičiai Branch of the Lithuanian Center of Agrarian and Forest Sciences (LRCAF) on the slopes of 7–9 ° and 9–11 ° hills, conducted in the summer of 2019. Soil was poorly and moderately eroded Albeluvisol. Two different types of crop rotation were tested in each stationary –crop rotation with black fallow and not fertilized and not used (not mown) grassland. During the investigation period, the winter barley, winter wheat and mixture of perennial grasses were grown in stationaries. An analysis of the three-year archival data of erosion stationaries showed that the loss of phosphorus compounds from the soil depended on the steepness of the slope of the hill and the plants growing on it. It was determined that the runoff of phosphate (PO4) from a 9–11° slope hill is approximately 3 times higher (0,40 mg l-1) than from a shallower 7–9 ° slope hill (0,15 mg l-1). Losses of phosphates (0,37 mg l-1) with slope leaked water is ~2 times higher on the slope hill, covered with crop rotation plants where annual tillage is performed, compared with the slope-covered perennial grasses (0,18 mg l-1). Studies conducted in 2019 showed that during the periods of heavy rainfall (15,70 mm), the lowest (3,00 l) runoff was on a 7–9 ° hillside with perennial grasses and the highest (230,00 l) runoff on a 9–11 ° on the hillside where the crop rotation plants were grown. Loss of phosphates (PO4) on a 9–11 ° slope hill covered with crop rotation plants was 0,32 mg l-1 and it was by 28 % higher compared to a slope hill of the same steepness, where the perennial grasses were grown. The highest runoff of washed away soil (242,00 kg) and mobile phosphorus (P2O5) (207,00 mg kg-1) was determined on the 9–11 ° hillside with light granulometric composition (cohesive sand- moderate loam soil) covered with crop rotation plants. Losses of soil and phosphorus compounds were not observed on the 7–9 ° hillside, where perennial grasses were grown. A very weak dependence was determined between the amount of phosphates (PO4) and the amount of leaked water (R2–0.16), but very strong dependence was determined between the soil loss and water runoff on the slope (R2–0.99). Amount of organic, inorganic and mobile phosphorus in the crop rotation with black fallow varied in the different slopes and in different part of the slopes. The highest amount of organic phosphorus was determined in the lower steep (7–9°) slope of the hill, where the clay fraction predominates in the soil. In contrast, the highest amount of mobile phosphorus (P2O5) (189,00 and 195,00 mg kg-1) were determined in the upper and middle parts of the hillside (9–11%), which granulometric composition was a cohesive sand. This could be related due to the low moisture sorption of this soil, poor plant development and the weak usage of mobile phosphorus for plant biomass growth. Organic and mineral phosphorus tended to accumulate in mesoaggregates of 2,0–1,0 mm (respectively 14,28 % and 4,72 %) in the more eroded upper slope hill. The increase of the quantity and persistence of these aggregates in water is one of the most effective way seeking to reduce phosphorus losses in hilly terrain soil. In this point of view, mixture of perennial grass is superior to crop rotation plants. |
