Das Verbundprojekt StaPlaRes: N-Stabilisierung und wurzelnahe Platzierung als innovative Technologien zur Optimierung der Ressourceneffizienz bei der Harnstoff-Düngung

Das F&E-Verbundvorhaben StaPlaRes entwickelt, untersucht und bewertet neuartige Technologien im Rahmen der Harnstoff (HS)-Düngung mit dem Ziel größtmöglicher Ressourceneffizienz und Umweltschonung

Modeling biomass growth, N-uptake and phenological development of potato crop.

Using the modeling tool Expert-N, daily fluxes of water, carbon and nitrogen in potato fields were simulated in this study. The crop growth model Soil-Plant-Atmosphere System Simulation (SPASS) was integrated in Expert-N and adapted for the simulation of potato growth. The aim of the study was to investigate the extent to which the SPASS model, tested thus far only for winter wheat, is suitable for the simulation of potato crops. In addition to re-parameterization of the model, minor modifications, such as description of phenological development, assimilate partitioning, nitrogen uptake and leaf senescence were carried out without changing the overall structure of the model. The SPASS model was calibrated using data from a potato field experiment carried out in 1996 at the Research Station Scheyern, which examined the effects of various fertilization applications on the growth and yield of two potato varieties, Christa" and "Agria", representing early and late maturity classes, respectively. Distinctions between "Christa" and "Agria" were realized by variable parameter values concerning phenological development, assimilate partitioning and nitrogen concentration in tubers. The model's ability to predict potato yields and nitrogen uptake was compared with actual values obtained in different years at other fields of the Research Station (only "Agria"). Simulation results show that the SPASS model was able to describe the effect of different N fertilizer applications on potato growth and nitrogen uptake. Differences between the two potato varieties could be adequately predicted, and tuber yields and nitrogen uptake well predicted. However, estimated modeling efficiencies suggest that further improvements are due. Crucial components of the model are the control of root nitrogen uptake and the regulation of the distribution of assimilates to different plant organs. To obtain a broader basis for the verification of the corresponding simulation modules, further experiments addressing optimal nitrogen concentrations in plant organs are necessary. Efforts to refine the SPASS model should be concentrated on a dynamical description of the partitioning pattern of assimilates, including a direct response of the partitioning pattern to changing environmental conditions

Lacer-induced Chlorophyll Fluorescence - a Tool for Online Detecting Nitrogen Status in Crop Stands

The on-line monitoring of crop stands is essential in a system of site specific N application. The chlorophyll fluorescence ratio F685/F730 is correlated with chlorophyll content and nitrogen content. Therefore monitoring the laser-induced chlorophyll fluorescence might be used to assess the N status of plants. During the 2000 growing period field campaigns were done with a hand held device to measure the fluorescence ratio F685/F730. Fluorescence ratio was negative correlated with N content and in late growth stages with N uptake as well. The coefficient of correlation was between r=0.976 (N content in dry matter in EC 30 against fluorescence ratio) and r=0.737 (N uptake in EC 37 against fluorescence ratio). The experiences of the 2000 measuring campaign will be applied for the further improvement of the technical design

Laser-Induced Chlorophyll Fluorescence Measurements for Detecting the Nitrogen Status of Wheat (Triticum aestivum L.) Canopies

The objective of this study was to assess the suitability of laser-induced chlorophyll fluorescence measurements to detect the nitrogen (N) supply of wheat (Triticum aestivum L.) at canopy level under ambient conditions. In 2002, a plot trial was carried out as a randomised block design. Increasing amounts of N fertiliser were applied to induce variations in the N uptake of the canopies. Different cultivars with varying growth habit and leaf colour were chosen to cover a wide range of canopy characteristics. Biomass was harvested at characteristic growth stages to determine aboveground dry matter yield, N concentration in dry matter and N uptake. Measurements with a hand-held chlorophyll sensor showed a strong correlation between the sensor signal and the N uptake thus indicating that the system is suitable for assessing the nutritional status of the plants. A clear differentiation between the N treatments was evident even at the beginning of stem elongation. The cultivar and the growth stage significantly influenced the sensor signal. Both factors need to be considered when predicting the N uptake of the canopy using laser-induced chlorophyll fluorescence measurements