Wilfried Werner

Effect of organic manure on organic phosphorus fractions in two paddy soils

We investigated the transformation of the organic P fractions from organic manure in two paddy soils (Ultisol, Entisol) and the influence of organic manure or cellulose on organic P under anaerobic conditions. The results obtained from the P fractionation experiment indicated that during the incubation labile and moderately labile organic P fractions increased in the Ultisol and decreased in the Entisol, which might be related to the difference in the organic matter content of both soils. Immediately after the application of organic manure, a large part of labile and moderately labile organic P supplied with the manure was transformed into moderately resistant organic P, possibly Ca- or Mg-inositol P were transformed into Fe-inositol P. During anaerobic incubation, the labile forms of organic P in the soils treated with organic manure were increased along with the incubation period in the first 4 weeks. The change in the moderately labile fraction was dramatic. It increased sharply in the first 2 weeks, then decreased, which was more pronounced in the soils treated with pig faeces. The moderately resistant fraction decreased during the whole incubation period. This indicated that under anaerobic conditions, the moderately resistant fraction can be transformed into labile and moderately labile organic P fractions, perhaps as Fe3+-inositol P is reduced to Fe+2-inositol P. Cellulose as an organic substrate had an increasing effect on organic P, especially when it was combined with inorganic P. Therefore, it is suggested that the application of inorganic P fertilizer combined with organic manure may be an effective way of protecting inorganic P against intensive sorption in soils.

Significance of soil microorganisms for the mobilization of nonexchangeable ammonium

To estimate the availability of nonexchangeable NHinf4sup+−N for soil microorganisms four incubation experiments were conducted under controlled conditions. The following results were obtained: Incorporating glucose as a source of readily oxidizable organic material favored the release of nonexchangeable NHinf4sup+−N. Mobilization of NHinf4sup+from the interlayers of the clay minerals was decreased by the application of K++, while Ca2+, which is supposed to expand the lattice of the clay minerals, had no influence on the release of NHinf4sup+. Soil temperature had no effect on microbiological mobilization of NHinf4sup+. It is assumed that, generally, the influence of nitrifying bacteria on the mobilization of nonexchangeable NHinf4sup+−N is negligible. However, in soils with abundant amounts of available carbon promoting the activity of heterotrophic soil microorganisms, the release of NHinf4sup+from clay minerals is favored under fallow conditions.

Effects of organic manure on solubility and mobility of different phosphate fertilizers in two paddy soils

The solubility and mobility of three phosphate fertilizers [superphosphate (SP), Ca-Mg phosphate (Ca-Mg-P) and diammonium phosphate (DAP)] with or without combination of farmyard manure (FYM) and/or farmyard manure juice (FYMJ) in two paddy soils (Ultisol and Entisol) from the Zhejiang Province of China were determined. Incubation experiments were conducted under controlled greenhouse conditions in the Institute of Agricultural Chemistry, Bonn University, Germany. The results showed that water soluble P and Olsen P in both the application band and the adjacent zones (10 and 20 mm from the application band) was highest with DAP, and lowest with Ca-Mg-P. Both FYM and FYMJ increased water soluble P (100–300%) and Olsen P (80–300%) for the application band in both soils. Moreover, the combination of FYM significantly increased water soluble P and Olsen P for the adjacent zones (20 mm for the Ultisol and 10 mm for the Entisol), but such effects were not significant in combination with FYMJ. Consequently, the main effect of FYM is due to organic substances from decomposition rather than organic compounds in the FYMJ. Also, the combination of FYMJ with SP and DAP significantly increased the pH value in the application band. The pH in the adjacent zone (10 mm) was slightly increased by the combination of FYM with each of three P fertilizers. The solubility and mobility of phosphate in soils differed greatly among phosphate fertilizers. The combinations of organic manure with mineral phosphate fertilizers increased solubility and mobility of phosphate in both paddy soils, especially in the Ultisol.

Characterization of soil nitrogen and nitrogen uptake by grass following a two-year fallow of potted soils receiving mineral and organic sources of nitrogen

Abstract Nitrogen turnover in fertilized soils with or without a supply of decomposable organic matter and the time-dependent remineralization of immobilized nitrogen were studied in a 3-year pot experiment. In three treatments, 15 N-labelled fertilizer was used. After 2yr of fallow the soils were planted with ryegrass and N uptake was measured. Soil samples were taken during the fallow and the following period of plant growth and contents of mineral nitrogen (N min ) and readily extractable organic N compounds (N org ) were determined. Changes in the Nn min content during the 2-yr fallow became differentiated according to (1) the amount of applied mineral N and (2) the C-to-N ratio that was established. Even 2 yr after C incorporation N was immobilized in some treatments. Changes of N org values during the first 4 weeks of the fallow depended primarily on the amount of added carbon. In the 3rd experimental yr differentiation of N contents were smaller and the amount of added nitrogen had a pronounced effect. Increase or decrease of the N org contents were not related to a reverse change in the N min content. Total N uptake was significantly related to N min content in the soil at the end of the fallow, i.e. prior to sowing ( r 2 = 0.98 ∗∗ ). The relationship was less close between N org and N uptake during the following growth period ( r 2 = 0.48 ∗ –0.56 ∗ ). The results of the 15 N treatments proved that application of fertilizer N enhanced N uptake from the native soil pool. Production of stabilized N compounds seemed to depend on the amount of microbial usable carbon, the C-to-N ratio of the added substrate and the number of turnover cycles.

Germany: the Baltic Sea and its agricultural environmental status

Abstract The contribution of diffuse (mainly agricultural) nutrient inputs into surface waters and then into the Northern and Baltic Seas has been estimated for nitrogen as approximately 60% and for phosphorus as approximately 47% of the total inputs for Germany (reference year 1989). The most important diffuse pathways are the input via groundwater and drainwater for nitrogen and via soil erosion for phosphorus. In both cases, about two-thirds of the total diffuse inputs are caused by these single sources. Only 8% of the total area of the former Federal Republic of Germany is within the catchment of the Baltic Sea. In using an area-proportional calculation, the absolute nutrient input into the Baltic Sea from agriculture could be estimated as 52.6 kt of nitrogen and 4 kt of phosphorus for 1989. The present situation in Germany indicates some improvements in the environmental status of agriculture as far as the potential for nutrient pollution of surface waters is concerned. The changes of the agricultural structure in the former German Democratic Republic after the reunification resulted particularly in a large scale reduction in livestock density, as well as a large amount of arable land being taken out of production. Therefore, the present situation is characterized by a significant reduction in the supply of farmyard and liquid manure, by reduced application rates of mineral fertilizers and, for land no longer in production, by a lower susceptibility for soil erosion. This reduced pollution potential should also result, with an unknown time-lag, in a lower nutrient input into the surface waters. Furthermore, the dramatic decrease of livestock density by more than 60% within the last 3 years will have a positive impact on the direct nutrient inputs by a careless or even illegal discharge of liquid manure, animal slurries and effluents from stored farmyard manure. It is an important demand that agriculture should increase their efforts to reduce the diffuse nutrient inputs into groundwater and surface water. Consequently, the activity of the official agricultural advisory service is especially focused on water-protection measures. ‘Fertilizer application prescriptions’ within the framework of the German ‘fertilizer regulation’ will limit the fertilizer application and, in particular, the application rates of animal slurry. Furthermore, the future selection of arable land for temporary or permanent removal from production will reinforce the water-protection potential of those measures.

Ökologische Aspekte des Phosphor-Kreislaufs

ZusammenfassungIm Gegensatz zu dem durch eine Vielzahl reaktiver Verbindungen gekennzeichneten N-Kreislauf ist der globale P-Kreislauf weniger komplex, da nur eine einzige reaktive Verbindung (PO43−) involviert und zudem die Atmosphäre nicht beteiligt ist. Ungeachtet dessen können anthropogene Störungen des natürlichen Kreislaufs auch bei P die Ausbildung ökologischer Ungleichgewichte auslösen. Betroffen hiervon sind die aquatischen Ökosysteme der Seen, Fließgewässer, Ästuare und des marinen Bereichs. Es wird eine Übersicht zu den wichtigsten Komponenten des globalen P-Kreislaufs (Speicher, Flüsse zwischen den Speichern, Verweilzeiten) gegeben. Die ökologische Dimension erhöhter Phosphoreinträge in Oberflächengewässer wird detailliert erörtert. In diesem Kontext wird am Beispiel des P-Kreislaufs in der Bundesrepublik Deutschland die besondere Rolle der Land-wirtschaft aufgezeigt.Von hoher ökologischer und ökonomischer Relevanz ist die prinzipielle Endlichkeit der Rohphosphat-Ressourcen. Der derzeitige Kenntnisstand über die nach verschiedenen Szenarien der Vorrats-und Verbrauchsschätzung (noch) zu erwartende Lebensdauer dieser Ressourcen wird dargelegt. Maßnahmen zum Abbau von P-Überschüssen in der Landwirtschaft, zu einer Effizienz-steigerung der P-Düngung und zu einem konsequenteren Recycling haben daher große Dringlichkeit.AbstractIn contrast to the complex N-cycle with its high number of reactive compounds, the global P-cycle is uncomplicated. There is only one reactive compound (PO43−), and the atmosphere is practically not involved. Nevertheless, severe ecological imbalances may be induced by anthropogenic perturbations of the P-cycle, especially in aquatic ecosystems. The present knowledge on the global P-cycle (reservoirs, fluxes, residence times) is summarized and the ecological dimension of increased phosphorus inputs into surface waters is discussed in detail. Exemplary for Germany, the role of agriculture is described in this context. The fact that the rock phosphate resources are principally limited and not renewable is of a high ecological and economical relevance. The expected lifetime of the P-reserves is calculated for different estimate-scenarios concerning the magnitude of reserves and consumption. Measures to reduce the P-surplus in agriculture, to increase the efficiency of P-fertilization, and to recycle P more consequently are therefore highly required.

Prediction of the P-leaching potential of arable soils in areas with high livestock densities.

Due to long-term positive P-balances many surface soils in areas with high livestock density in Germany are over-supplied with available P, creating a potential for vertical Plosses by leaching. In extensive studies to characterize the endangering of ground water to P pollution by chemical soil parameters it is shown that the available P content and the P concentration of the soil solution in the deeper soil layers, as indicators of the P-leaching potential, cannot be satisfactorily predicted from the available P content of the topsoils. The P equilibrium concentration in the soil solution directly above ground water table or the pipe drainage system highly depends on the relative saturation of the P-sorption capacity in this layer. A saturation index of <20% normally corresponds with P equilibrium concentrations of <0.2 mg P/L. Phytoremediation may reduce the P leaching potential of P-enriched soils only over a very long period.