Phosphorus Rate, Leaching Fraction, and Substrate Influence on Influent Quantity, Effluent Nutrient Content, and Response of a Containerized Woody Ornamental Crop.

Authors: OWEN, JR., JAMES - OREGON STATE U,AURORA,OR; WARREN, STUART - NORTH CAROLINA STATE UNIV; BILDERBACK, TED - NORTH CAROLINA STATE UNIV; Albano, Joseph

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2008
Publication Date: 6/1/2008
Citation: Owen, Jr., J., Warren, S., Bilderback, T., Albano, J.P. 2008. Phosphorus Rate, Leaching Fraction, and Substrate Influence on Influent Quantity, Effluent Nutrient Content, and Response of a Containerized Woody Ornamental Crop.. HortScience. 43(3):906-912.

Interpretive Summary: There is a rising need for increased water and nutrient use efficiency in ornamental container production to maximize profits while minimizing environmental impact. In the current study, the interactions of mineral aggregate amendment (sand or clay), leaching fraction [10% or 20% (defined as the amount of water that leached out of the container divided by the amount of water applied to the container)], and phosphorous application rate (1.0 grams or 0.5 grams per container). The use of calcined clay resulted in containers that held more plant-available water. Decreasing leaching fraction resulted in signifcant reductions in the amount of water applied to and leached from containers. Reducing the amount of phosphorous applied improved plant phosphorous-use-efficiency which is defined by the amount of plant growth (weight) divided by the concentration of phosphorous per unit weight.

Technical Abstract: Production of containerized nursery crops requires high inputs of water and mineral nutrients to maximize plant growth to produce a salable plant quickly. However input efficiencies remain below 50% resulting in major quantities of water and nutrients leached. This study was conducted to determine if production factors could be altered to increase water and phosphorus uptake efficiency (PUE) without sacrificing plant growth. The effects of a pine bark substrate amendment (clay or sand), a 50% reduction in both phosphorus (P) application rate (1.0 g or 0.5 g) and leaching fraction (LF = effluent ÷ influent) (0.1 or 0.2) were investigated. Containerized Skogholm cotoneaster (Cotoneaster dammeri Schnied. 'Skogholm') was grown on gravel floor effluent collection plots that allowed for calculation of water and nutrient budgets. Pine bark amended with 11% (by vol.) Georgiana 0.25 to 0.85 mm calcined palygorksite-bentonite mineral aggregate (clay) increased available water 4% when compared to pine bark amended with 11% (by vol.) coarse sand. Decreasing LF from 0.2 to 0.1 reduced cumulative container influent 25% and effluent volume 64%, whereas total plant dry mass was unaffected by LF. Reduction of target LF from 0.2 to 0.1 reduced dissolved reactive P concentration and content by 8% and 64%, respectively. In a sand-amended substrate, total plant dry mass decreased 16% when 1.0x P rate was reduced to 0.5x P, whereas total plant dry mass was unaffected by rate of P when pine bark was amended with clay. Plant content of all macronutrients, with the exception of N, increased when pine bark was amended with clay versus sand. Reducing P rate from 1.0x to 0.5x increased PUE 54% or 11% in a clay or sand-amended substrate, respectively. Amending pine bark with 11% (by vol.) 0.25 to 0.85 mm calcined palygorksite-bentonite mineral aggregate produced an equivalent plant with half the P inputs and a 0.1 LF which reduced water use 25% and P effluent losses 42% when compared to an industry representative substrate [8 pine bark : 1 sand (11% by vol.)].