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United States Department of Agriculture

Agricultural Research Service

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James Spiers
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Dr. James (Jim) Spiers

  • developed a blueberry foliar bud rating scale, discovered that temperatures required to damage floral buds were inversely related to the stage of bud development, determined floral buds exposed to (but undamaged by) cold developed as rapidly as buds with no cold exposure, and documented varietal tolerance to freeze damage.  His floral bud rating scale is nationally and internationally used by the blueberry industry in flowering/ freeze damage research, timing of pesticide and plant growth regulator applications, regional varietal recommendations and during blueberry bloom, guiding extension scientists/growers in the timing/implementation of frost protection practices.  This resulted in $40-million value to industry and has aided greatly in expansion of blueberry production in United States and several nations such as Japan and Chile. 
  • determined rabbiteye blueberry plant growth and uptake of most required macronutrients (N, P, K, Ca, Mg, K) and 2 micronutrients (Mn, Fe) was optimized when a reduced source (NH4+) of N fertilizer was used.  Determined growth was reduced by the oxidized form of N fertilizer (NO3) regardless of the associated basic cations.  These findings resulted in rabbiteye blueberry fertilization recommendations for the use of NH4+ as a nitrogen source.  These recommendations have been followed globally wherever blueberries are produced. 
  • determined that the addition of sulfur to lower pH of soils and micronutrients to correct visual chlorosis symptoms using levels not detrimental to plant growth were not sufficient to overcome the adverse effects of Na and Ca in irrigation water.  These findings determined the importance of using irrigation water with very low levels of electrical conductivity (Na, Ca, and other cations).  Extension agents now recommend altering existing irrigation schemes in production fields and testing water quality specifically for its acceptability for blueberries.  This has been responsible for a $3 to 5-million savings to producers and has allowed expansion only in areas with good water quality. 
  • determined the relative importance of various cultural practices on the growth and production of southern highbush blueberries (mulch>incorporated peatmoss>irrigation) and the importance of using a mulching material that was effective in reducing soil temperatures when growing southern highbush blueberries.  Extension scientists now recommend to growers proper mulching in the establishment of southern blueberries and the benefits of continued mulching in southern highbush blueberry production.  These are now standard cultural recommendations.

Last Modified: 8/11/2016
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