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Optimising the malting barley value chain
The protein content of malting barley for optimal processing in the brewery is in the narrow range between 9.5 and 11.5 percent. However, high yields of the new malting barley varieties are often associated with a reduction of the protein content to below 9.5 percent. Some batches could therefore not be sold at the malting barley price in the past years.
In a four-year project funded by the Science Promotion of the German Brewing Industry, institutions from Baden-Württemberg, Bavaria, Lower Saxony and Thuringia have joined forces to gain insight into the behaviour of malting barley under different fertiliser variations in a total of 32 trials.
Brewing barley varieties
A range of regionally important varieties was tested, and the four varieties Quench, Marthe, RGT Planet and Avalon were included in the trials across locations and could thus be included in the joint calculation. Marthe represents a somewhat older variety type with good quality, meanwhile comparatively low yield level and genetically determined higher protein content. Quench, which is only one year younger, is still cultivated in Germany and shows a low protein content with good malt quality. RGT Planet was the variety with the highest yield in Germany at the start of the project, and Avalon embodies the character of modern varieties with good yield and excellent malt quality.
The full barley percentage of four spring barley varieties under the three nitrogen fertilisation levels, years 2015-16, mean values from six trialsFertilisation options
The N quantity determined according to the official fertilisation recommendation DSN (Fertilisation System Nitrogen) was selected as the nitrogen fertilisation variant level one. The amount of N to be fertilised per hectare is calculated from various parameters such as the N requirement of the barley, the nitrogen available in the soil (Nmin content) and soil type. On average, the amount of N fertilised in stage one in the trials was between 90 and 120 kg/ha.
In stage two, the recommended amount of N was increased by 30 kg N/ha (DSN + 30), the timing of fertiliser application remained the same, for sowing spring barley.
For stage three, the fertiliser application was split into two applications (DSN + 30/2), with the recommended amount of N again applied at sowing and 30 kg N/ha at the time of barley shelling.
The increased N quantities are also still within the range of the maximum quantity specified by the Fertiliser Ordinance and represent the range used in practice.
Nitrogen uptake and translocation (kg N/ha) of the malting barley variety Quench (results of a fertilisation experiment in Braunschweig, 2015)Nitrogen dynamics in the plant
Investigations into the nitrogen content in the straw of the plants show very clearly that from the time of flowering onwards, very little nitrogen was taken up from the soil. Instead, the nitrogen was shifted from the stem and the leaves into the ears. It follows that in the trial, late N fertilisation had virtually no effect on yield or protein content in the grain.
What are the effects of increased N fertilisation?
The additional nitrogen increased the stand density and plant length of the spring barley, but also had a great influence on the stability of the varieties and led to increased storage before harvest and increased disease pressure in all varieties tested here. Malting barley managed more intensively with more nitrogen must therefore also be treated more intensively with regard to the use of growth regulators. The proportion of full barley in the varieties also decreases somewhat as a result of the higher stand density with increased N fertilisation
Yield (top) and protein content of the variety Avalon in the supra-regional evaluation 2016 to 2019. The orange lines mark the range of 9.5 to 11.5 percent desired by processorsResults of the supraregional evaluation
In the evaluation across all 32 environments (location x year), an increase in yield and protein content was observed due to the increase in fertilisation. The distribution of the N application had no further influence in the trials. From the results on yield and crude protein content it can be deduced that the increased N application was not completely absorbed by the plants, thus the N uptake efficiency decreased with increasing N fertilisation.
More important than these expected trends, however, are the effects of varying N management at the individual sites, as the example of the modern variety Avalon shows. It can be seen that the variations in yield and crude protein content between the environments were significantly greater than between the N fertilisation variants. A similar picture emerged for all the varieties investigated.
Risk of exceeding the acceptance threshold
In order to make it clear how great the danger is of achieving too high a protein content through higher N fertilisation, the proportion of environmental worlds was counted for each fertilisation level that still fell below the desired limit of 11.5 percent crude protein for processing in the brewery.
This type of evaluation makes it very clear that the risk of exceeding the 11.5 percent limit increases with increased N application. At least a reduction of this risk can be seen through the breeding progress of the last years. In the case of the variety Marthe, the frequency of exceedance increases significantly compared to Quench, Avalon and RGT Planet, but the trend could not be overlooked for all varieties.
Proportion of environments (location x year) with a protein content below the desired 11.5 percent and three different fertiliser variants, results from 24 trials, BY, BW, TH, 2016 to 2018Consequences for farmers and processors?
The trials have made it clear that the influence of the environment on yield performance and especially protein content is greater than the influence of variety or N fertilisation. Spring barley is one of the crops where environmental influences are most difficult to compensate for by crop management and technical measures. This makes it extremely difficult to hit the narrow window for the range between 9.5 percent and 11.5 percent desired by the brewing industry.
A general recommendation to increase the N-fertilisation or a division can in no way be derived from the extensive trials. If the official guidelines for determining the N fertiliser requirement are followed, the chances of achieving the optimum quality are best. Nevertheless, poorer qualities can occur depending on site or weather conditions.
For processors in the value chain, this means that depending on the year and location, fluctuations in quality are to be expected even when growing modern varieties. However, over a larger growing region, the quality is usually acceptable on average.
The malting barley producers can do little against these environmental influences, but bear the risk entirely on their own due to the previous regulations for price reductions.
It would therefore be desirable if the risk could be shared between farmers and processors. This would make the cultivation of malting barley in Germany more attractive again and thus improve the availability of domestic raw material for beer production.
Team of authors
Dr. Markus Herz, Bayerische Landesanstalt für Landwirtschaft, Freising; Thomas Würfel, Landwirtschaftliches Technologiezentrum Augustenberg, Karlsruhe; Hubert Heß, Thüringer Landesamt für Landwirtschaft und Ländlichen Raum, Jena; Dr. Martin Kücke, Dr. Burkhard Stever-Schoo, Julius Kühn-Institut, Braunschweig.
Acknowledgement
The authors would like to thank Ms Ulrike Nickl, Ms Lucia Huber, Mr Thomas Eckl (LfL) Mr Heinrich Maubach (Syngenta Seeds), Mr Carsten Rieckmann (LWK Lower Saxony) and Mr Hans-Jürgen Seele (Braugerstenverein Lower Saxony) for their helpful support.
