|MACHADO, RUI M A|
Submitted to: Frontiers in Crops Science and Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2011
Publication Date: 9/19/2011
Citation: Bryla, D.R., Machado, R. 2011. Comparative effects of nitrogen fertigation and granular fertilizer application on growth and availability of soil nitrogen during establishment of highbush blueberry. Frontiers in Crops Science and Horticulture. 2:1-8.
Interpretive Summary: In many regions, blueberry is irrigated by drip. One major advantage of drip over traditional sprinkler systems is the capability to apply water-soluble fertilizers during irrigation, a procedure known as fertigation. The objective of the present study was to compare the relative effectiveness of fertigation with the standard application of granular fertilizer on plant growth and nitrogen uptake during establishment of highbush blueberry. Overall, applying nitrogen fertilizer through the drip irrigation system enhanced early growth of blueberry when compared to equal quantities of fertilizer applied as a surface application. Fertigation more likely increased plant growth over granular fertilizer by reducing salt stress and maintaining safe and optimum levels of ammonium nitrogen (the source of nitrogen preferred by blueberries) within the root zone throughout the season. This study will continue for at least three more years to determine the effects of each treatment on fruit production.
Technical Abstract: A 2-year study was done to compare the effects of nitrogen (N) fertigation and granular fertilizer application on growth and availability of soil N during establishment of highbush blueberry (Vaccinium corymbosum L. ‘Bluecrop’). Treatments included four methods of N application (split fertigation, continuous fertigation, and two non-fertigated controls) and four levels of N fertilizer (0, 50, 100, and 150 kg/ha N). Fertigation treatments were irrigated by drip and injected with a liquid ammonium fertilizer solution; split fertigation was applied as a triple split from April to June while continuous fertigation was applied weekly from leaf emergence to 60 d prior to the end of the season. Non-fertigated controls were fertilized with granular ammonium sulfate, also applied as a triple split, and irrigated by drip or microsprays. Continuous fertigation produced the smallest plants among treatments at 50 kg/ha N in year 1 but the highest canopy cover at 150 kg/ha N in both years 1 and 2. The other application methods required less N to maximize growth but were less responsive than continuous fertigation to additional N fertilizer applications. In fact, 44-50% of the plants died when granular fertilizer was applied at 150 kg/ha N. By comparison, none of the plants died with continuous fertigation. Plant death with granular fertilizer was associated with high ammonium ion concentrations (up to 650 ppm) and electrical conductivity (>3 mS/cm) in the soil solution. Early results indicate that fertigation may be less efficient (i.e., less plant growth per unit of N applied) at lower N rates than granular fertilizer application but is also safer (i.e., less plant death) and promotes more growth when high amounts of fertilizer is applied.