Effects of conventional and organic land use types on water protection criteria in Germany

The mean values and ranges of several water protection criteria were calculated for arable land, grassland and forests in Germany on the basis of research work and the literature. By additional evaluation steps, relationships and efficiency coefficients were calculated for the different types of land use. Methods of balance calculations are proposed as preventive strategies for efficient water protection

Grain legume nitrogen fixation and balance model for use in practical (organic) agriculture

In extensive agricultural systems, i.g. organic farming, nutrient balance calculations are of high importance. Common calculation models for nitrogen fixation of grain legumes are either of far too much complexity especially for use in agricultural practice or of too low accuracy. Measurements in the literature of grain yield, harvest index, N2 fixation, N content, N surplus, Nmin content of the soil, etc., were compiled. Correlation analyses were then carried out with Vicia faba L. and Pisum sativum L. data sets from conventional and organic field trials per-formed in Central European. Grain yield or N output, Nmin content before sowing, and the N harvest index proved to be the most effective driving variables for developing a calculation model for plant nitrogen fixation and the surplus amount. All the variables mentioned are listed in farmers’ plot card indices, with the exception of the N harvest index, an essential variable which is not detectible by the farmer. Therefore, the N harvest index was indirectly determined through the effects of grain yield and Nmin content using non-linear multiple re-gression analyses. Comparing calculations between common and the improved forms of mod-els showed significantly better conformity between measured and calculated datasets of grain legumes

Designing crop rotations in organic and low-input agriculture: Evaluation of pre-crop effects

In this overview, the preceding effects of crop pairs are classified by establishing schematic diagrams for use in crop rotation planning in low external input or organic agricultural systems. Results from previous crop rotation trials and earlier diagrams cited in the literature were evaluated in order to classify the succession effects for more than 25 main crop species. Additional information about several cultivation remarks were annotated in small letters for every crop sequence. In a tabular overview, the crop species were arranged into three main categories according to the different duration of their pre-crop effects: I. N fixing, soil fertility increasing legumes and legume-grass mixtures; II. N depleting, intense soil fertility reducing non-legumes; III. modest soil fertility reducing non-legumes

Effects of increasing fertilization in organic farming fodder cultivation and market crop systems

In 1992, on experimental stations of the Saxony State Institute of Agriculture, two organic field trials were set up on loamy sand and a loess loam in western Saxony, eastern Germany. In these long-term field trials questions of fodder cultivation and market crop systems, crop rotations with legume-grass, wheat and maize, different organic fertilizer regimes and nutrient cycling were analyzed regarding their effects on soil fertility, yield and quality of the plant products. The main results and conclusions of the first nine years of these organic field trials are introduced and summarized here

Site adjusted organic matter balance method for use in arable farming systems

Common humus balance methods give distinct inexact results and do not meet nowadays requirements in Germany. Outgoing from the method of KOERSCHENS et al. (2004) an improved, site adjusted, semi-quantitative method was developed for manual use in agricultural practice and consultation. In the validation and optimization process over 300 variants from 39 long-term field trials were used, which represent the most important site conditions of Central Europe (Germany). The optimization work was done in four steps. Identification of site specific groups with homogenous humification levels. Distinct different humification characteristics were recognized for the organic matter of different German site conditions (soil, climate). Six site specific groups could be identified when comparing the results of the humus balancing with the field trial organic matter content changes of the soils. Humification coefficients of the crop species. The effects of the crop species cultivation, and the climate and soil conditions on the humification process were combined and expressed in the crop species humification coefficients. Optimal values were obtained when the results of the humus balancing were in accordance with the organic matter content chance of the trials (objective function: 0 kg Corg ha-1 ≈ 0 % Corg content change). Equal assessments of the site specific groups were reached by systematic adjustments of the humification coefficients of the crop species until the objective function was observed. Humification coefficients of the organic materials. Additional analyses of multiple long-term field trial results have shown, that the organic material coefficients of the common balance method were fixed at somewhat too high values. Over this, the humification values were negatively related to increasing supply of organic materials. Therefore, these coefficients were corrected according to the field trial results. Classification system for the humus balance results. The nitrogen surface balance of the field trials was suitable for to evaluate the soil fertility and environmental tolerance of the humus balance results. Under a specific N surplus constraint (e.g. 50 kg N ha-1), arable cultivation systems without mineral nitrogen fertilization (e.g. organic farming) can tolerate much higher humus surplus values than systems with increasing nitrogen fertilization. For use in different arable farming systems, therefore, the common classification scheme (A to E system of VDLUFA) was corrected. Through installation of humification coefficients in site-specific groups adjusted to the Corg content change in the soil, and adaptation of the humification coefficients of the organic materials, the optimization process resulted in a large improvement of the method accuracy (s2=0,034 to s2=0,011). For practical use, only a little information about site specific characteristics, the crop species in the crop rotation and the amounts of added organic materials are necessary in the calculations

Laser-controlled adaptive optic for beam quality enhancement in a multipass thin disk amplifier

We devise a laser-controlled adaptive optical element which operates intracavity under high intensity radiation. This element substitutes a conventional mechanically deformable mirror and is free of critical heat-sensitive components and electronics. The deformation mechanism is based on the projection of a CW control laser onto a specially designed mirror. Mounted to a water-cooled heat sink, the mirror can handle laser radiation beyond 3 MW/cm^2. The properties of the adaptive optical element including the maximum correctable wavefront pitch of 800 nm are discussed. The successful implementation in a multipass thin disk amplifier is presented. An improvement of the beam quality by a factor of three is achieved. We identify measures to enhance the performance of the adaptive optic towards efficient operation in a high-power laser system

Empirical Study of Intraday Option Price Changes using extended Count Regression Models

In this paper we model absolute price changes of an option on the XETRA DAX index based on quote-by-quote data from the EUREX exchange. In contrast to other authors, we focus on a parameter-driven model for this purpose and use a Poisson Generalized Linear Model (GLM) with a latent AR(1) process in the mean, which accounts for autocorrelation and overdispersion in the data. Parameter estimation is carried out by Markov Chain Monte Carlo methods using the WinBUGS software. In a Bayesian context, we prove the superiority of this modelling approach compared to an ordinary Poisson-GLM and to a complex Poisson-GLM with heterogeneous variance structure (but without taking into account any autocorrelations) by using the deviance information criterion (DIC) as proposed by Spiegelhalter et al. (2002). We include a broad range of explanatory variables into our regression modelling for which we also consider interaction effects: While, according to our modelling results, the price development of the underlying, the intrinsic value of the option at the time of the trade, the number of new quotations between two price changes, the time between two price changes and the Bid-Ask spread have significant effects on the size of the price changes, this is not the case for the remaining time to maturity of the option. By giving possible interpretations of our modelling results we also provide an empirical contribution to the understanding of the microstructure of option markets

Isotopic tiling theory for hyperbolic surfaces

In this paper, we develop the mathematical tools needed to explore isotopy classes of tilings on hyperbolic surfaces of finite genus, possibly nonorientable, with boundary, and punctured. More specifically, we generalize results on Delaney-Dress combinatorial tiling theory using an extension of mapping class groups to orbifolds, in turn using this to study tilings of covering spaces of orbifolds. Moreover, we study finite subgroups of these mapping class groups. Our results can be used to extend the Delaney-Dress combinatorial encoding of a tiling to yield a finite symbol encoding the complexity of an isotopy class of tilings. The results of this paper provide the basis for a complete and unambiguous enumeration of isotopically distinct tilings of hyperbolic surfaces