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Title: REDUCING WATER AND NUTRIENT INPUTS TO CLAY AMENDES SUBSTRATES: HOW LONG CAN WE GO?

Author
item OWEN, JAMES - NCSU
item WARREN, STUART - NCSU
item BILDERBACK, TED - NCSU
item Albano, Joseph

Submitted to: Southern Nursery Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/1/2005
Publication Date: 12/1/2005
Citation: Owen, J., Warren, S., Bilderback, T., Albano, J.P. 2005. Reducing water and nutrient inputs to clay amendes substrates: how long can we go?. Southern Nursery Association Research Conference. 50:99-102.

Interpretive Summary: Production strategies for reducing phosphorous runoff include minimizing both phosphorous application (i.e., phosphorous enetering the production system) and limiting the amount of runoff from the container (i.e., what transports phosphorous away from the production area). In the study, sand-amended pine bark growing substrate, what is commonly used in the Southeast, was compared to clay-amended pine bark. The results were that 'Stogholm' contoneaster grown in the clay-amended substrate required less water and less phosphorous, while improving growth, compared to the sand-amended substrate.

Technical Abstract: The objective of this study was to determine the affect of 50% reduction in phosphorous application and leaching fraction on plant growth with a clay- or sand-amended pine bark substrate. Reduction of water volume to maintain a leaching fraction of 0.10 versus 0.20 did not significantly affect 'Skogholm' contoneaster growth, but reduced daily and cummulative water use by approximately 30% across both clay- and sand-amended pine bark substrates. At the 0.5X phosphorous rate, however, dry weight of 'Skogholm' cotoneaster grown in clay-amended substrate increased 45% compared to sand-amended pine bark. The clay-amended substrate also increased growth 15% at the 0.1X phosphorous rate compared to the sand-amended substrate. Dry weight of 'Skogholm' contoneaster when grown in clay amended pine bark was similar with the 1.0X or 0.5X rate of phosphorous. Therefore, clay-amended pine bark can maintain plant growth with only half of the currently recommended leaching fraction and phosphorous rate compared to traditional sand-amended pine bark. With the clay-amended substrate this research demonstrated that environmental impact of containerized nursery crops can be reduced without affecting plant growth by decreasing water and phosphorous inputs.