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3.  Objective

The objective of this work is to fill a gap of the need for non-destructive, site-specific, machine-based, on-line sensing of still standing crop biomass by optimizing the mechanical sensor developed by the Institute of Agricultural Engineering ATB (EHLERT & SCHMIDT 1996, EHLERT & JÜRSCHIK 1997, EHLERT 1998), as a tool for site-specific management in heterogeneous fields.

The focus of this work is the optimisation of the swinging pendulum biomass sensor for the cereal crops winter rye (Secale cereale L.), winter wheat (Triticum aestivum ssp. Vulgare) and irrigated rice (Oriza sativa L.) at the usual application timings for plant protection. These application dates are the timings at which management decisions such as fungicide treatments or spraying with growth-regulators will have to be decided for the site-specifically optimised plant protection. At these timings, different pendulum parameter settings of the mechanical sensor can be proved on the same strip of cereal crops with a high heterogeneity in crop biomass.

Accuracy and repeatability of the replicates have to be determined for the different possible parameter settings of the sensor. Therefore, the measurements will be repeated with the necessary number of replicates of the same setting and then validated.

The limits of the parameter settings, at which the measurements prove non-destructive, will be examined.

The accuracy of the site-specific biomass determination for the different sensor parameters will be clarified. Consequently, it will be examined to which degree the sensor measures dry mass and fresh mass of the crops. The ability of the sensor measurements to determine additional plant parameters such as crop height or crop density will also be clarified in several trials.

It is necessary to identify the factors, associated with a biasing effect on the biomass measurements or the regression equations of the measurements and the cut and weighed biomass. Several factors such as cultivar, season, management methods, and growth of the crop may bias the measurements, and therefore, will be detected and proved wrong or true.

The use of the sensor for site-specific differentiated plant protection will be shown in primary field trials, therefore, the potentials of site-specific plant protection according to crop biomass will be shown in one trial with a plant growth-regulator, and another trial with a fungicide treatment. The utilization of crop biomass as a decision base for plant protection will be discussed.

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