No abstract

On the summit of a hill with a lack of humidity, and in usually stronger eroded midslope parts, crops thin out. Changing ecological conditions change the soil seed bank as well. The aim of this study was to examine changes in the seed bank size and number of species and the influence of seed surface characteristics on their spread in different-intensity agrophytocenoses under hilly relief conditions. This study included different parts of the hill (summit, midslope and footslope) in Lithuania. The southern exposition slope’s soil was slightly eroded Eutric Retisol (loamic). In spring and autumn, the seed bank was investigated at depths of 0–5 and 5–15 cm. Irrespective of the season, in the soil of permanent grassland, the seed number was 6.8 and 3.4 times smaller compared to those of cereal–grass crop rotation and crop rotation with black fallow. The highest number of seed species was determined in the footslope of the hill. Seeds with rough surfaces dominated on all parts of the hill, but the highest amount (on the average 69.6%) was determined on the summit of the hill. In autumn, a strong correlation was found between the total seed number and soil microbial carbon biomass (r = 0.841–0.922).

To maintain the potential productivity of Retisol and produce stable yields of agricultural crops, one has to regularly lime and replenish soil reserves with organic matter. If the necessary amount of manure cannot be accumulated on farms, it is relevant to use other organic fertilisers. The current paper presents the results of long-term manuring experiment that was carried out at the Vėžaičiai Branch of Lithuanian Research Centre for Agriculture and Forestry under humid littoral climatic conditions during the 2015-2019 period. The objective of this study was to determine the influence of liming and organic fertilisation on the changes in weed incidence in the crops of the sustainable crop rotation. The experiment was carried out in the soils differing in acidity: unlimed soil with pH 4.13 and limed soil with pH 5.87. The organic fertilisation treatments were: 1) without organic fertilisers (control); 2) green manure; 3) farmyard manure 40 t ha-1 ; 4) green manure, on the background of 40 t ha-1 farmyard manure; 5) farmyard manure 60 t ha-1 ; 6) green manure, on the background of 60 t ha-1 farmyard manure. The study found that at the beginning of crop growing season, i.e. during weed germination, soil acidity had significant influence on the total number of weeds, number of weed species as well as percentage of the annual dicotyledonous weeds and acidophilic weeds. The significant impact of interaction of soil acidity and organic fertilisation on weed incidence indices showed up at the maturity stage of crops of the rotation.

Soil erosion by water is a serious environmental problem. It is very important to form agrophytocenosis, which is productive on hilly terrain and could effectively protect the soil from erosion. The aim of the study was to examine the impact of a hilly relief on the changes of seeds in a soil of pre-erosion cereal-grass crop rotation. The study included different parts of the hill (summit, midslope, and footslope). The southern exposition slope’s soil was slightly eroded Eutric Retisol (loamic) (RT-eu.lo), and the steepness of the slope was 9–11°. The seed bank was investigated at the depths of 0–5 and 5–15 cm. The number of seeds in the soil seed bank during autumn was 20.4% higher than in the spring. The highest number of seeds in the autumn was determined on the summit (40.6 thousand seeds m–2). The highest count during the spring was determined on the midslope of the hill (36.4 thousand seeds m–2). In general, in the soil seed bank of the midslope of the hill, the number of seeds was by 7.8% and 42.4% higher compared to the summit and footslope parts. The highest seed reserve was found in the soil at a 0–5 cm depth (59.4% of the total seed number).