How to influence barley grain quality

Achieving the required quality targets for barley can greatly affect the value of the harvested crop, depending on the intended market e.g. livestock feed or malt for the brewing industry. The main quality targets to consider are grain nitrogen percentage, specific weight, moisture and grain weight.

Research has also shown that the malting quality of barley is determined by a number of other grain properties, such as the composition of proteins and carbohydrates, endosperm structure, cell wall composition and the activities of various enzymes during malting. 

Crop nutrition programmes have an impact on the quality of the harvested barley grain and should be planned according to the targeted quality parameters. To achieve the highest value for barley grain, the grower often has to meet a combination of these specifications.

The most important macronutrients to consider are nitrogen, sulphur and potassium. A well-balanced nutrient program should therefore be the aim. Too much or too little of any of these nutrients can have a negative effect. Excess nitrogen will lead to high grain protein which may or may not be desirable. It could also cause the crop to lodge with the eventual consequence being a delayed harvest and grains that begin to grow in the ear. Sulphur can influence grain nitrogen and protein composition. 

Nitrogen greatly influences grain protein content

A high nitrogen content in barley grain tends to arise from a large uptake or redistribution of nitrogen late in the season, or poor starch deposition. Nitrogen applications will highly influence barley grain protein concentration.

Higher rates of direct application increase barley grain nitrogen/protein. This may be desirable where the crop is being used for animal feed. Where the market is for low nitrogen malting barley, however, reduced rates will be required. It is therefore important to match the nitrogen rate with the desired yield and quality targets.

During the grain-filling phase, nitrogen is redistributed from the stems, leaves and chaff to the developing grain. The root system will remain active during this phase which gives the potential high soil nitrogen uptake, late leading to high grain protein content.

Delaying nitrogen applications will give higher levels of grain nitrogen. If the barley is autumn sown then nitrogen applications should be made around Zadoks G.S. 25-31. In spring-sown barley at least 60% of the nitrogen should be applied into the seedbed at planting, with the remaining going on at Zadoks G.S. 13. Where high nitrogen (protein) is required to improve the livestock feeding quality, nitrogen rates can be higher, and sometimes delayed to give increased protein concentration.

Potassium indirectly affects grain quality

Excess potassium can indirectly affect grain quality. Sufficient potassium gives good stem strength, reducing the potential for ‘lodging’ and ‘brackling’, (straw stems breaking), causing ears/spikes to fall to the ground. Very often the grains in the ear begin to germinate, thereby reducing barley grain quality.

Sulphur is an important protein component

Sulphur deficiency leads to limited barley yield, giving a concentration effect from the nitrogen applied and leading to higher grain nitrogen levels. Where sulphur is applied, higher yields are obtained by diluting the nitrogen, which gives lower nitrogen values in barley grain. Where sulphur is deficient, it has been shown to impair the activity of the germinating enzymes. They are important during the malting process (F.J. Zhao et al, 2005).

Manganese and Zinc influence nitrogen metabolism

Manganese and Zinc play an important role in many plant processes, including the metabolism of nitrogen. Improving nitrogen metabolism increases the amount of nitrogen incorporated into developing proteins.