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Report, 2006

Variations of yield and protein content of malting barley

Pettersson, C. G.


Malting barley has to fulfil several quality demands to be fully accepted, and paid, by the malting industry. The cultivar has to be selected by the industry, the vitality of the lot has to be high, the husk has to be uninjured and the grain protein content has to be at the proper level and as even as possible. Flat protein levels are hard to achieve, as the grain protein over malting barley fields often vary 3% around the field mean. The urge for even protein makes this crop a natural object for precision agriculture research, but surprisingly little has been reported. In the present project, precision agriculture methods have been used to monitor grain yield and grain protein of Swedish malting barley. The goal of the project has been, for spring sown Swedish malting barley, to understand the reasons for and patterns of the variability in grain protein, and design a method for fertilisation with a potential to produce more even protein with the proper mean level. It seems possible to design such a fertiliser system, provided that a restrained amount of compound NPKS fertiliser is combi-drilled at sowing and that the second fertiliser application as calcium nitrate is distributed, at the latest, at the two node stage of the barley. The second application needs the control from a remote sensor using an appropriate vegetation index. The most commonly used vegetation indices did not correlate well with the grain yield, or with the grain protein level at such an early stage, possibly because of disturbing reflections from the soil. However, a set of recently developed indices for maize did correlate with the patterns of both grain yield and grain protein. To get the mean values between years and places right, the regression algorithms also needed a measure of thermal stress during grain filling. A thermal stress index was designed as a temperature sum during three weeks, and a threshold for the temperature sum was optimised to 20 °C.

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ISBN: 91-576-6896-5
Publisher: Dept. of Crop Production Ecology, Swedish University of Agricultural Sciences

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