Ewald Schnug

Effect of long-term grazing on soil organic carbon content in semiarid steppes in Inner Mongolia

To clarify the response of soil organic carbon (SOC) content to season-long grazing in the semiarid typical steppes of Inner Mongolia, we examined the aboveground biomass and SOC in both grazing (G-site) and no grazing (NG-site) sites in two typical steppes dominated by Leymus chinensis and Stipa grandis, as well as one seriously degraded L. chinensis grassland dominated by Artemisia frigida. The NG-sites had been fenced for 20xa0years in L. chinensis and S. grandis grasslands and for 10xa0years in A. frigida grassland. Aboveground biomass at G-sites was 21–35% of that at NG-sites in L. chinensis and S. grandis grasslands. The SOC, however, showed no significant difference between G-site and NG-site in both grasslands. In the NG-sites, aboveground biomass was significantly lower in A. frigida grassland than in the other two grasslands. The SOC in A. frigida grassland was about 70% of that in L. chinensis grassland. In A. frigida grassland, aboveground biomass in the G-site was 68–82% of that in the NG-site, whereas SOC was significantly lower in the G-site than in the NG-site. Grazing elevated the surface soil pH in L. chinensis and A. frigida communities. A spatial heterogeneity in SOC and pH in the topsoil was not detected the G-site within the minimal sampling distance of 10xa0m. The results suggested that compensatory growth may account for the relative stability of SOC in G-sites in typical steppes. The SOC was sensitive to heavy grazing and difficult to recover after a significant decline caused by overgrazing in semiarid steppes.

Coca Cola® is it ! The ubiquitous extractant for micronutrients in soil

Abstract Coca Cola® has been found to be an excellent extractant for micronutrients in soils, particular for manganese (Mn). The main ingredients of Coca Cola®, phosphoric acid, reducing sugar and carbon dioxide are well proven in common extraction recipes. The overall extraction force of Coca Cola® was similar to that of commonly used phosphoric acid methods. Compared to DTP A, Coca Cola® extracted only 27% of iron (Fe), 38 % of copper (Cu), and 86% of zinc (Zn), but 165% of Mn. Correlation coefficients for the relationship between Coca Cola®‐extractable Fe, Zn, and Cu in soils and element concentrations in plants were the same as by means of the DTPA method. For Mn 49% of the variability in Mn concentrations observed in field grown winter wheat plants could be explained by Coca Cola®‐extractable soil Mn, but only 39% when employing DTPA. The critical value for available Mn and Zn on the investigated inceptisols was 17.8 mg/kg Mn and 1.3 mg/kg Zn for Coca Cola® and 9.4 mg/kg Mn and 1.8 mg/kg Zn for DTPA....

Langzeiteffekte ackerbaulicher massnahmen auf die bodenfruchtbarkeit

An Hand von Dauerversuchen in Braunschweig und Müncheberg wird in einer Fallstudie der Einfluß landbaulichen Managements auf Erträge und Bodenfruchtbarkeit dargestellt. Langfristig werden hohe Erträge sowie optimale Humusgehalte nur durch kombinierte organisch ‐ mineralische Düngung erreicht. In den Varianten hoher Erträge finden sich vergleichsweise höhere Bodengehalte an Corg, P(CAL) sowie höhere pH‐Werte. Ohne organische Düngung (Variante NPK) kann der Corg‐Gehalt des Bodens nicht aufrechterhalten werden. Doch auch alleinige organische Düngung (Variante Stm2) reicht auf sandigen Ackerstandorten nicht aus, optimale Humusgehalte einzustellen. Langfristig erhöht konservierende Bodenbearbeitung die Erträge und verringert die N‐Austräge in die Atmosphäre und ins Grundwasser.

Status of Iron, Manganese, Copper, and Zinc of Soils and Plants and Their Requirement for Ruminants in Inner Mongolia Steppes of China

The availability of heavy metal micronutrients and their distribution in soils and plants as well as their requirements for grazing animals are important when assessing the environmental quality and nutritive status for ruminants of a given area. The mean available copper (Cu), zinc (Zn), and manganese (Mn) contents of all soils were respectively 1.20, 1.60, and 3.38 g kg−1 of calcareous soils in the Inner Mongolia steppe of China. The heavy metals content of the chernozem soil were usually greater than those of other soils, whereas their contents in plants, however, were usually smaller than those in plants from other soils. It means that the heavy metal bioavailability in the chernozem soil is relative low. Positive significant correlations between available Cu, Zn, and Mn and organic carbon, total nitrogen and clay contents, and between available Cu and Zn and between available Zn and Mn in soils were observed. On the other hand, negative significant correlations between heavy metals and pH were found. The results of stepwise regression analysis showed that the parameter organic carbon and clay are the most important variables. Available Cu, Zn, and Mn contents increased with increasing organic carbon and clay. Means and ranges of iron (Fe), Mn, Cu, and Zn in plants of the five soils were 14.6–91.5, 3.1–5.4, 0.8–2.3, and 1.5–2.2, respectively. Therefore, all plant samples were considered severely deficient in Fe, Mn, Cu and Zn for all ruminants. The availability of micronutrient heavy metals in soils to plants and to grazing animals in plants deserves further studies in this region. The Fe, Mn, Cu and Zn contents in feces of grazing sheep averaged 125.3, 16.4, 4.8 and 6.2 mg kg−1. In the natural grassland, animal manures, therefore, may be an important heavy metals source.

Suitability of extractants for predicting available sulfur in natural grassland in the Inner Mongolia steppe of China

Abstract It was the objective of this study to compare the suitability of different extractants for predicting the availability of sulfur (S) in natural grassland in a sulfur response trial on three different soil types in the Inner Mongolia steppe of China. For soil analysis, seven different extractants have been employed. The inorganic SO4–S concentration was determined by ion chromatography. Additionally, in the Ca(H2PO4)2 extract the total soluble S was determined employing turbidimetry. Weak salt solutions (0.15% CaCl2, Ca(H2PO4)2, and KH2PO4) extracted similar amounts of SO4–S. Extraction with 0.025 M KCl provided the lowest SO4–S values. Deionized water dissolved significantly more SO4–S in the control plots than most weak salt extractants. The concentration of soluble organic S decreased in the control plots after 100 days of plant growth, indicating that the organic S pool contributed significantly to the S nutrition of the forage crops. Significant relationships among the SO4–S in the soil determined in different extracts and crop yield, sulfur content in the forage, and total sulfur uptake were only found for the Ca(H2PO4)2 extract. In general, the correlation coefficients proved to be unsatisfactory for field experimentation.

SPATIAL SPECIATION—A NEW APPROACH TO ASSESS SOIL ANALYSIS METHODS

Geostatistical methods were used to examine the “spatial speciation” of phosphorus (P) in an agricultural cambisol, whereby in this study speciation was defined functionally, considering the strength of the bonding between phosphorus and soil particles as an indication of its plant availability as well as its mobility in the soil. P species were analyzed employing a range of methods which differed in their extraction force. Extractants used were aqua regia, nitric acid, calcium lactate, ammonium acetate and calcium chloride. Soil texture, pH, Fe, CaCO3 and total carbon concentrations were determined in air-dried soil samples. Three different P pools could be identified by geostatistical methods, whereby the P concentration of each pool displayed a different continuity depending on distance and direction. The distribution pattern of the soluble P pool appeared to be governed by the adsorption capacity of the soil and subsequently by the spatial variability of soil texture. The influence of topography on soil erosion processes was reflected in the variation of total P, whereas the labile P fraction was apparently related to recent fertilizer practices. Results of this study indicate that an evaluation of the spatial speciation of a nutrient may provide essential information about its behavior in the environment and as such should be considered when choosing soil analysis methods.

Landbau und treibhauseffekt‐quellen und senken für CO2 bei unterschiedlicher landbewirtschaftung

Die Ergebnisse der Müncheberger Dauerversuche sind eine geeignete Datenbasis zur Bewertung der CO2‐Senke im Landbau (produzierter Gesamtertrag und Akkumulation von organischer Bodensubstanz) sowie der CO2‐Quelle (Verlust an organischer Bodensubstanz und Einsatz fossiler Energie). Durch diese Parameter sind wesentliche Größen für die Quantifizierung des C‐ bzw. CO2‐Haushaltes gegeben. Sie sind Indikatoren für den Vergleich unterschiedlicher Bewirtschaftungsintensitäten und charakterisieren die Umweltverträglichkeit der Pflanzenproduktion. Ein reduzierter Faktoreinsatz kann die CO2‐Emission im Vorleistungsbereich der Landwirtschaft nur dann mindern, wenn dieser geringere Faktoreinsatz nicht mit deutlich geringerem Energiegewinn (CO2‐Bindung im Ernteertrag) verbunden ist. Ziel landwirtschaftlicher Bodennutzung ist es u.a., die Erhaltung standorttypischer C‐Gehalte im Boden zu gewährleisten. Langfristig kann durch kombinierte organischmineralische Düngung sowie konservierende Bodenbearbeitungsverfahren auf sandigen Böden eine Erhöhung des C‐Pools im Boden um ca. 10% erreicht werden. Die CO2‐Emissionen im Vorleistungsbereich der Landwirtschaft sollten auf sandigen Ackerstandorten 9 bis 10% der in der Biomasse gespeicherten CO2‐Menge nicht übersteigen.