Nitrogen – finishing for yield and quality

Within a short growing period, timing and rate of nitrogen topdressing are most crucial for the final yield and quality.

Which application strategy is most efficient?

Malting or feeding?

Quality

Spring barley is mainly grown for malting. Grains that do not meet malting specifications are used for feeding. Spring barley is also grown for feeding on purpose in regions with a short growing season or where winter barley is likely to be damaged by frost.

Maltsters have specific requirements that need to be met by adequate crop management:

  • plump, bright, clean and sound kernels with minimal skinned and broken kernels, 90% of grains > 2.5 mm
  • purity of contacted variety > 93% with less than 2% other cereals
  • moisture content < 14.5%
  • a protein content of 9.5% to 11.5%

Yield

The yield potential of malting barley is often underestimated and is mainly determined by water supply. While rainfed spring barley yields about 4 – 6 t/ha, more than 8 t/ha can be achieved with an irrigated crop and newly bred varieties. Malting barley has a lower protein target compared to feeding barley and many farmers are afraid to exceed the upper limit of 11.5% protein content.

With higher yield targets offered by new varieties, additional nitrogen application rates may result in protein contents below 9.5%. To avoid penalties, nitrogen supply needs to match the estimated yield objective as shown in table 2.

Nutrient removal

The following tables provides standard nutrient uptake of malting barley for main nutrients.

Table 2: Nutrient removal (grain and straw) for different yields.

Nitrogen application strategy

Short uptake period

Nitrogen application strategies need to match strong uptake during fast growth. Between late tillering and ear emergence, 65% of all nitrogen needs to be taken up in just 3-5 weeks (figure 2). Only about 20% of nitrogen is taken up before stem elongation and about 15% after flowering. It is therefore recommended to apply at least 60% of total nitrogen needs directly at sowing to ensure fast establishment, rapid leaf growth and intensive tillering as well as optimum nitrogen availability during stem elongation.

To exploit the yield potential while controlling the protein content, nitrogen topdressing is recommended between late tillering and early stem elongation. 20 - 40% of totally required nitrogen can be applied at this growth stage to control the final density of productive tillers. Furthermore, a good yield estimate, based on expected water availability and crop status, helps to derive the optimum rate for the nitrogen topdressing.

Figure 2: Most of nitrogen (~65 %) is accumulated already before flowering within 3 to 5 weeks during stem elongation and booting. Less than 15% of nitrogen in the grain is still taken up after flowering while 85 % of protein is built from nitrogen translocated from leaves and stems into the grain.

Which nitrogen form?

Nitrogen is best applied as ammonium nitrate since it ensures fast uptake, low ammonia losses compared to urea or UAN and even spreadability. It is the only nitrogen form that can sufficiently support high nitrogen uptake rates during stem elongation and booting. This is why higher yield and more protein are harvested with use of ammonium nitrate compared to urea (figure 4).

Figure 4: Grain yield and protein content of spring barley with a nitrogen topdressing of 45 kg/ha, applied as CAN or urea, respectively.

Manure is not a sufficiently reliable as a nitrogen source for malting barley since mineralization of contained nitrogen takes place too late in the growing season and imposes the risk of excessive protein contents.

Precision farming

Precision farming tools such as the Yara N-Tester and N-Sensor can be used to match the optimum N-rate and thus increase yield, adjust protein content and reduce the environmental impact of nitrogen fertilizers.

N-Tester measurements give an indication of the nitrogen content of the crop. Therefore, high levels suggest to use lower than standard nitrogen rates and vice versa.

The Yara N-Sensor can detect areas with different nitrogen status within fields on the go and can address those with variable nitrogen spreading. Results show higher yields and better quality with the same or even lower amount of nitrogen applied (figure 3).

Figure 3: Trial results with malting barley with and without N-Sensor. Use of the N-Sensor provides higher yields with lower fertilizer input.

Micronutrients

Spring barley responds to complementary micronutrient applications. Grain size, number and yield were improved after treatments with copper, manganese and zinc. Foliar application during late tillering to early stem elongation are most effective to prevent deficiencies and to help the crop to better cope with abiotic stresses like drought, heat and high irradiation.