Reduction in nitrogen fertilization rate sustains malt barley yield and quality in the malt barley-pea rotation.

Authors: Sainju, Upendra

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2024
Publication Date: 10/20/2024
Citation: Sainju, U.M. 2024. Reduction in nitrogen fertilization rate sustains malt barley yield and quality in the malt barley-pea rotation.. Agronomy Journal. https://doi.org/10.1002/agj2.21717.
DOI: https://doi.org/10.1002/agj2.21717

Interpretive Summary: Nitrogen fertilizer is the largest direct input cost in malt barley production, ranging from 25% to 50% of total input costs. Reducing the amount of synthetic nitrogen fertilizer applied to crops decreases farmers costs and improves soil health and environmental quality but crop yield and quality must remain at economically sustainable levels. An ARS researcher in Sidney, MT evaluated dryland malt barley yield and quality response over a range of nitrogen fertilizer application rates for malt barley grown in rotation with dry pea in a semi-arid northern Great Plains environment with or without a fall seeded cover crop. The objective was to determine how much the amount of fertilizer applied can be reduced as a result of the biologically-fixed nitrogen supplied by residue from the preceding pea crop. The researcher found that the amount of nitrogen fertilizer applied for semi-arid dryland malt barley production can be reduced by 18 pounds per acre from the typically recommended N fertilization rate of 72 pounds of nitrogen per acre without affecting malt barley yield and quality, regardless of cover cropping. Nitrogen fertilization is required to enhance malt barley yield, but excessive amounts can reduce malting quality by causing higher grain protein concentration and a lower proportion of plump kernels. Unacceptable levels of these quality indicators can lead to the crop being rejected by brewers resulting in an average profit loss of 33%. Malt barley growers can use the reduced nitrogen fertilization rate of 54 pounds per acre to sustain malt barley yield and quality by employing malt barley-pea rotation in dryland cropping systems of the semi-arid northern Great Plains. The information is useful not only for growers, but also for malting industry personnel, environmentalists, students, scientists, and policy makers.

Technical Abstract: Rotational benefit of pea (Pisum sativum L.) may reduce N fertilization rate and sustain malt barley (Hordeum vulgare L.) yield and quality in the malt barley-pea rotation. This study examined the effect of cover crop (oat [Avena sativa L.] cover crop vs. none) and N fertilization rate (0, 40, 50, 60, 70, and 80 kg N ha-1) on malt barley growth, yield, and quality in the malt barley-pea rotation from 2013 to 2019 in the northern Great Plains. Cover crop biomass yield and N accumulation were greater in 2016 than other years. Compared to fallow, malt barley plant density with cover crop was 9-13% lower from 2013 to 2015, but 10% greater in 2017. Malt barley straw yield was 38% greater in 2017 and grain yield 15-39% greater in 2017 and 2018, but grain plumpness was 5-10% lower in 2014 and 2017 with than without cover crop. Increasing N fertilization rate linearly increased grain yield and N uptake, but reduced grain test weight and plumpness in most years. Straw N concentration and uptake and grain protein concentration varied by year. Because of the similar grain yield, protein concentration, plumpness, and test weight between 60 and 80 kg N ha-1, 60 kg N ha-1 can be recommended to sustain malt barley yield and quality in the malt barley-pea rotation, regardless of cover crops. This helps to reduce N fertilization rate from the recommended N rate of 80 kg N ha-1 in dryland cropping systems of the northern Great Plains.