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Title: USING A MINERAL AGGREGATE TO SUPPLY PHOSPHORUS AND POTASSIUM FOR CONTAINERIZED CROP PRODUCTION

Author
item OWEN, JAMES - Oregon State University
item WARREN, STUART - Kansas State University
item BILDERBACK, TED - North Carolina State University
item Albano, Joseph

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2008
Publication Date: 3/1/2009
Citation: Owen, J., Warren, S., Bilderback, T., Albano, J.P. 2009. USING A MINERAL AGGREGATE TO SUPPLY PHOSPHORUS AND POTASSIUM FOR CONTAINERIZED CROP PRODUCTION. Acta Horticulturae (ISHS).819:311-316.

Interpretive Summary: Amending nursery crop substrates with clay effectively reduces the amount of potassium and phosphorous that leaches from the container, subsequently contaminating surface waters with these nutrients. The objective of this study was to determine if clay aggregates bound with potassium and phosphorous could then be reused as a fertilizer, supplying potassium and phosphorous for plant production. To study this, we grew a commercially important woody nursery plant (Cotoneaster dammeri) in substrate that contained 9 percent by volume clay and applied the following treatments: nitrogen only, nitrogen and potassium only, and nitrogen, potassium and phosphorous. We found that clay would supply sufficient phosphorous but not potassium to maintain normal plant growth.

Technical Abstract: There is a rising need for increased water and nutrient use efficiency in ornamental container production to maximize profits while minimizing environmental impact. Substrates containing industrial mineral aggregates (clay) can increase water use efficiency and reduce phosphate leaching while retaining maximum crop growth. In addition, these clays may be able to provide a labile source of plant available phosphorus (P) and potassium (K). A study was performed to determine if 9 percent (by volume) palygorskite-bentonite industrial clay aggregate amended pine bark substrate could supply adequate P and K to maximize growth of Cotoneaster dammeri C.K. Schneid. ‘Skogholm’. Plants were top-dressed with single [nitrogen (N) only], incomplete (N and K only), or complete controlled release fertilizer (N, P, and K) and microirrigated cyclically to maintain a 0.25 leaching fraction. Dry mass of Skogholm cotoneaster was greatest when receiving the incomplete fertilizer (N and K) and least when only N was applied (P and K were absent). Foliar P concentration was not limiting in all treatments and greatest in plants receiving N only. In contrast, foliar K was limiting in Skogholm cotoneaster when receiving a fertilizer containing only N. Foliar K increased 46 percent when grown with a complete (N, P, and K) or incomplete fertilizer (N and K). Water extractable substrate K was unaffected by fertilizer treatment, however substrate extractable P decreased 55 percent when using single or incomplete fertilizer that contained no P. The clay amendment was able to supply adequate P to maximize growth when using an incomplete fertilizer (N and K).