Improving highbush blueberry nitrogen management with nitrification inhibitors
Introduction
The objective of this study was to assess the effects of nitrification inhibitors, applied with two nitrogen fertilizer rates (60 vs. 120 kg N/ha) and two fertigation systems (suspended vs. buried), on blueberry yield and soil nitrate and ammonium levels.
In British Columbia (BC), ammonium sulfate is widely used for blueberry nitrogen fertilization. This fertilizer has two major advantages: first, it breaks down rapidly to ammonium, the preferred form of nitrogen for blueberries; second, sulfate maintains low soil pH favourable for blueberry growth (pH 4.5- 5.5). However, recent studies have shown that fertilizer application above recommended rates increases soil salinity and reduces pH below suitable thresholds. Additionally, ammonium is not stable in the soil and is quickly converted to nitrate by soil microorganisms. Once converted, the efficiency in which blueberries take up nitrogen is very low and the nitrate ends up leaching out of the soil profile with irrigation and rain.
To slow the conversion of ammonium to nitrate, nitrification inhibitors, such as dicyandiamide (DCD) and Nitra-pyrin, can be used. However, for blueberry crops with sawdust mulch, it remains unclear whether applying a mix of fertilizer and nitrification inhibitors through drip-fertigation can successfully delay the conversion and improve plant nitrogen uptake.
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About this Brief
This brief was prepared by the BC Food Web team with the help of Aimé J. Messiga and is based on the following scientific journal article:
Messiga, A. J., Nyamaizi, S., Yu, S., & Dorais, M. (2021). Blueberry yield and soil mineral nitrogen response to nitrogen fertilizer and nitrification inhibitors under drip-fertigation systems. Agronomy, 2144(11). https://doi.org/10.3390/agronomy11112144
Key Findings
- Nitrification inhibitors, applied through drip-fertigation, can delay the conversion of ammonium (preferred form of nitrogen for blueberries) to nitrate.
- The effect of nitrification inhibitors on blueberry yield and soil ammonium and nitrate concentrations was inconsistent in this three-year study.
- Further studies are needed to determine the best timing for nitrification inhibitor application that aligns with the timing of blueberry nitrogen uptake, such as early in the growing season and post-harvest.