Zur Anreicherung von Schwermetallen in Böden und Kulturpflanzen durch praktische Klärschlammdüngung

The accumulation of heavy metals in soils and crops by practical sewage sludge application An accumulation of cadmium, lead, zinc and copper was found in some soils and crops after sewage sludge application as compared with same soils and plants not fertilized with sewage sludge. In the soils the heavy metals mainly were accumulated in the Ap-horizons. The displacement into subsoils was small, in spite of the good permeability of the sandy soils investigated. Relatively the mobility of zinc and cadmium in soils was most distinct. Within the plants the accumulation of the heavy metals was strongest in the roots, however also evident in the shoots of rye, barley and oats. Zinc and copper was concentrated in the grains, too. On the meadow-land an accumulation of the elements investigated was found in the blades of rye grass (Lolium perenne L.).     

Regional assessment of the temporal trends in soil acidification in Southern Sweden,using the safe model

The dynamic soil acidification model SAFE was applied to 44 forested sites in Skåne, southern Sweden, using available Swedish databases on present soil status, vegetation and deposition. Time series of deposition were derived for each site from present deposition in a generalized fashion by dividing deposition into different classes and scaling with deposition trends from the literature. This study connects the current status of the soil and the soil development with critical load maps calculated with the steady-state model PROFILE.The model was calibrated against measurements of present base saturation from the Swedish Forest Inventory. Model output was compared with available measurements of soil water chemistry.     

Humus balances of different farm production systems in main production areas in Austria

The importance of the soil humus content is indisputable. Soil humus plays an important role in preserving soil fertility and exerts great influence on plant production and yield potential. However, proofing that management‐related changes in the stock of soil organic matter (SOM) have taken place against the background of spatial and temporal variation is a difficult task. In most cases, sampling over a long period of time is needed to verify these changes. Alternatively, potential changes in the SOM stock can be estimated using humus balancing models, which help to identify the need for humus reproduction on a farm. In general, a humus balance is the difference between the humus demand of cultivated crops and humus supply through crops and organic fertilizers. In this study, the ‘Dynamic Humus Unit Method' within the modelling program REPRO was applied to calculate the humus balance for 29 model‐farms that are representative of most of the agricultural production in Austria. Each model‐farm represents a specific production type (PT) and farming system in a defined region or main production area (MPA). This approach gives an overview of the humus balances at a large scale and allows a general trend in Austria to be estimated. Besides differing between conventional and organic farming systems, specific site conditions can also be selected in the model. The constructed model‐farms belong to different PTs such as “forage production”, “cash crops”, “refinement”, and “permanent crops”. The PT “permanent crops” refers to the cultivation of wine. The cropping system of each PT was analyzed in detail, while livestock keeping was considered only when applicable. Positive humus balances were found for all PTs except for permanent crops. The results ranged from –122 to 890 kg C ha^?1 y^?1. Regions and farm structure, e.g., forage production compared to cash crop, were found to have a greater influence than the kind of farming system (i.e., organic vs. conventional farming). Comparing the different PTs, forage production had the highest positive humus balances (219 to 890 kg C ha^?1 y^?1), followed by cash crop (24 to 239 kg C ha^?1 y^?1), refinement (–64 to 402 kg C ha^?1 y^?1) and permanent crops (–122 to –38 kg C ha^?1 y^?1). Regarding the farming system, organic farming led to more humus accumulation than conventional farming due to a higher share of fodder legumes and catch crops and more diverse crop rotations. The results were within the range of available empirical data on SOM change, and it was therefore concluded that the results are reasonable. In general, humus reproduction can be regarded as sufficient for agricultural production.     

Hydrological pathway and source area of nutrient losses identified by a multi-scale monitoring in an agricultural catchment

The objectives of the study were to identify principal hydrological pathways and source areas of N and P losses by multi-scale monitoring and to estimate total nutrient losses from the catchment. An agricultural catchment with rain-fed agriculture and irrigated paddy fields in subtropical China was monitored with regularly sampling, together with intensive sampling during and after rain storms. Regular weekly sampling showed that the N concentrations in the overland flows from the upland and paddy fields were higher than those from the streams, but lower than those in the subsurface waters. The N concentration, on average, was 10.0 mg L^− 1 in the well and 1.7 mg L^− 1 in the spring water, the former was 10.2 times as high as that in the stream waters (1.0–1.5 mg L^− 1). Nitrogen and P in the overland flows originated dominantly in particulate forms from the uplands (over 70%) and in dissolved forms from the paddy fields. Inorganic N and P dominated in the streams and subsurface waters. The intensive sampling allowed us to establish flow-nutrient concentration relationships and to extrapolate nutrient losses during rainstorms without regular sampling. The extrapolation increased the estimated nutrient losses by about 30% to 50%. The average total nutrient losses within three water years were estimated as 21 kg N ha^− 1 yr^− 1 and 1 kg P ha^− 1 yr^− 1, accounting for 9.5% and 1.4% of chemical N and P fertilizers applied to the catchment after subtracting the nutrient inputs with irrigation and rainfall. The estimation showed that paddy fields were as important as the uplands in terms of nutrient losses. These results suggest that control of soil erosion and excessive irrigation could be effective to reduce nutrient export through overland flow and subsurface flow.     

Photoperiod in recirculation aquaculture systems and timing of seawater transfer affect seawater growth performance of Atlantic salmon (Salmo salar)

Production of Atlantic salmon smolts in recirculation aquaculture systems (RAS) is growing, and novel production protocols using continuous light in RAS are being implemented in the industry. In the present study, Atlantic Salmon parr were exposed to either a traditional protocol (short-day winter signal [12:12 L:D] for 6 weeks) or to continuous light. Both photoperiods were applied in freshwater (FW) and brackish water RAS. Salmon from all treatments were transferred to seawater pens at 200 and 600 g and grown until slaughter size. A control group was smoltified with a 6-week short-day winter signal and kept in FW until sea transfer at 100 g. Continuous light gave a higher growth rate in RAS but reduced feed intake and growth and increased feed conversion ratio during the first 8 weeks in seawater. However, at slaughter, fish exposed to continuous light was bigger than fish given a winter signal because of the higher growth rate in RAS. Slaughter weight was lowest in fish transferred to sea at 600 g, despite having the highest day-degree sum during their life span. The best performing group was the control group transferred at 100 g. All treatments handled transfer to seawater and survival and maturation were not affected by the treatments in RAS. The immune status was examined with a multigene expression assay on BioMark HD platform from parr stage to 5–7 months after seawater transfer. Overall, there was no significant effect of photoperiod or salinity on the expression of the selected immune genes. In sum, the results from this study indicate that using continuous light in RAS may have negative effects on performance shortly after transfer in fish transferred to sea at 200 g, whereas at 600 g, all treatments had reduced growth after transfer irrespective of treatment in RAS.     

Bodennutzung und Nitrat-Stickstoff in der Dränzone von Lößdecken der südlichen Niederrheinischen Bucht

Land use and nitrate-nitrogen in the vadose zone of loess deposits in the southern part of the Lower Rhenish Embayment Mean annual nitrogen-leaching was studied at seven experimental sites with grain-sugar beet crop rotation. Soil water simulation models and determination of the nitrogen content in the vadose zone below the rooting zone were combined to quantify the annual leaching rates. Leaching amounts to 11–18 kg NO₃^? N/ha · a at sites where only mineral fertilizer was applied, whereas sites with additional organic fertilizers show higher leaching rates of 30–36 kg NO₃^? N/ha · a.     

Detection of expressed fungal Type I polyketide synthase genes in a forest soil

Secondary metabolites synthesized via the polyketide pathway are thought to mediate interference competition between soil microorganisms as well as cell-to-cell signaling. Although their synthesis has been documented in laboratory culture, it remains uncertain whether these compounds are actually produced under field conditions. Here, we report the presence and expression of fungal Type I polyketide synthase (PKS) genes in the organic horizon of a forest soil. If these expressed PKS genes produce compounds that elicit antagonistic interactions among soil microorganisms, then it could be a factor structuring microbial communities in soil.     

Soil organic carbon in the rocky desert of northern Negev (Israel)

Purpose

So far, the soil organic carbon (SOC) literature is dominated by studies in the humid environments with huge stocks of vulnerable carbon. Limited attention has been given to dryland ecosystems despite being often considered to be highly sensitive to environmental change. Thus, there is insufficient research about the spatial patterns of SOC stocks and the interaction between soil depth, ecohydrology, geomorphic processes, and SOC stocks. This study aimed at identifying the relationship between surface characteristics, vegetation coverage, SOC, and SOC stocks in the arid northern Negev in Israel.

Materials and methods

The study site Sede Boker is ideally suited because of well-researched but variable ecohydrology. For this purpose, we sampled five slope sections with different ecohydrologic characteristics (e.g., soil and vegetation) and calculate SOC stocks. To identify controlling factors of SOC stocks on rocky desert slopes, we compared soil properties, vegetation coverage, SOC concentration, and stocks between the five ecohydrologic units.

Results and discussion

The results show that in Sede Boker, rocky desert slopes represent a significant SOC pool with a mean SOC stock of 0.58?kg?C?m^?2 averaged over the entire study area. The spatial variability of the soil coverage represents a strong control on SOC stocks, which varies between zero in uncovered areas and 1.54?kg?C?m^?2 on average in the soil-covered areas. Aspect-driven changes of solar radiation and thus of water availability are the dominant control of vegetation coverage and SOC stock in the study area.

Conclusions

The data indicate that dryland soils contain a significant amount of SOC. The SOC varies between the ecohydrologic units, which reflect (1) aspect-driven differences, (2) microscale topography, (3) soil formation, and (4) vegetation coverage, which are of greatest importance for estimating SOC stocks in drylands.