Blueberry Yield and Soil Mineral Nitrogen Response to Nitrogen Fertilizer and Nitrification Inhibitors under Drip-Fertigation Systems
In blueberry plantings, nitrification can result in losses of mineral nitrogen (N) through leaching because blueberries prefer ammonium (NH<sub>4</sub><sup>+</sup>) over nitrate (NO<sub>3</sub><sup>−</sup>). The objective of this study was to assess th...
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| Autores principales: | , , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/13ee70a1bf044e538787e65296577670 |
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| Sumario: | In blueberry plantings, nitrification can result in losses of mineral nitrogen (N) through leaching because blueberries prefer ammonium (NH<sub>4</sub><sup>+</sup>) over nitrate (NO<sub>3</sub><sup>−</sup>). The objective of this study was to assess the effects of two rates of N fertilizer, mixed or not with nitrification inhibitors (NI) and applied through two fertigation systems, on berry yield and the concentrations of NH<sub>4</sub><sup>+</sup>-N and NO<sub>3</sub><sup>−</sup>-N along the soil profile. Thus, nine combinations of treatments including two N fertilizer rates (60 and 120 kg N ha<sup>−1</sup>), two NI (with DCD + Nitra-pyrin or without) and two fertigation application methods (buried and suspended drip lines) and a control (0 kg N ha<sup>−1</sup>) were tested over three years (2016–2018) in a long-term blueberry planting. Berry yield was on average 47.32 Mg ha<sup>−1</sup> in 2016 and 26.86 Mg ha<sup>−1</sup> in 2018. In 2017, berry yield varied between 8.60 Mg ha<sup>−1</sup> under the control and 11.66 Mg ha<sup>−1</sup> with 120 kg N ha<sup>−1</sup> applied through suspended drip lines. Low berry yield in 2017 was due to a heavy pruning to rejuvenate the plants. In 2016, the concentration of NH<sub>4</sub><sup>+</sup>-N in the sawdust mulch layer varied between 13.1 and 27.1 mg kg<sup>−1</sup> in the spring, 11.4 and 32.1 mg kg<sup>−1</sup> in the summer, and 7.9 and 72.9 mg kg<sup>−1</sup> in the fall; the concentration of high NH<sub>4</sub><sup>+</sup>-N along the soil profile did not exceed 5 mg kg<sup>−1</sup>. High concentrations of NH<sub>4</sub><sup>+</sup>-N in the sawdust mulch layer were associated with NI, but did not translate to high berry yields. The concentration of NO<sub>3</sub><sup>−</sup>-N in the soil profile reached 42.6 mg kg<sup>−1</sup> in the summer and 39.0 mg kg<sup>−1</sup> in the fall and these high concentrations were associated with NI. In 2017 and 2018, there was no effect of NI on NH<sub>4</sub><sup>+</sup>-N concentrations even in the layer of sawdust mulch which was not consistent with the results obtained in 2016. High concentrations of NO<sub>3</sub><sup>−</sup>-N were measured beneath the sawdust mulch layer with treatments including N fertilizer alone or mixed with NI. It is possible that NH<sub>4</sub><sup>+</sup> retained in the layer of sawdust mulch and not taken up by plant roots was subsequently oxidized to NO<sub>3</sub><sup>−</sup> at the end of the residence time of NI in the soil. Our results showed that high concentrations of NO<sub>3</sub><sup>−</sup>-N along the soil profile occurred mainly during the summer which could be explained by irrigation water driving NO<sub>3</sub><sup>−</sup> leaching. |
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