UNDERSTANDING SALINITY AND NITROGEN INTERACTIONS TO IMPROVE FLORICULTURE EFFICIENCIES

Authors: Poss, James; CARTER, CHRISTY - U.C. RIVERSIDE, CA; Grieve, Catherine; Shouse, Peter

Submitted to: Proceedings of the International Salinity Forum
Publication Type: Proceedings
Publication Acceptance Date: 4/11/2005
Publication Date: 4/25/2005
Citation: Poss, J.A., Carter, C.T., Grieve, C.M., Shouse, P.J. 2005. Understanding salinity and nitrogen interactions to improve floriculture efficiencies. In: Proceedings of the International Salinity Forum, Managing Saline Soils and Water: Science, Technology, and Soil Issues. April 25-27, 2005. Riverside, CA pp:121-124.

Interpretive Summary: Historically, the floriculture industry has been a significant user of water resources. This is especially true where many economically important crops are salt sensitive and require quality water for irrigation. As competition for quality water continues, the use of wastewaters for irrigation may be a desirable option for many salt tolerant floriculture crops. The greenhouse and nursery industries are also facing increasing real and potential restrictions on the release of drainage waters (primarily nitrogen compounds) aimed at improving the quality of local water resources. Specifically, the discharge of effluents from greenhouse and nursery operations has become a critical issue with regard to contamination of rivers, streams, aquifers, and tidal pools since effluents typically contain high concentrations of nitrate salts. This research demonstrated production of Matthiola incana flowers can be achieved while minimizing nitrogen inputs and maximizing the salinity of the irrigation water. The use of a three-phase growth curve analysis was successful in characterizing the effect of altering the nitrogen concentrations and salinity of irrigation waters used in closed-loop irrigation systems. This type of model is suitable for use in simulations where inputs (light, heat, day-night temperature differentials) differ from one environment to the next when expressed in thermal units. Significant reductions in N input can be realized with no loss of crop quality in the closed system. The closed system of production can significantly reduce off-site nitrogen loading and maximize the use of otherwise regarded poor quality waters. These are environmentally desirable features that can improve the water resource-use efficiencies of floriculture production.

Technical Abstract: Greenhouse nursery operations are historically important producers of floriculture products. Greenhouse and nursery industries are also facing increasing real and potential restrictions on the release of effluents (primarily nitrogen compounds) aimed at improving the quality of local water resources. Specifically, the discharge of excess nutrients from greenhouse and nursery operations has become a critical issue related to contamination of rivers, streams, aquifers, and tidal pools with nitrate salts. One strategy that can be implemented to reduce the concentrations of unused nutrients that are ultimately discharged is to re-circulate in a closed irrigation system (capturing and re-use of drainage water) until most of the nutrients are depleted. This management option increases the potential of salinity effects on plant growth since many important floral crops are salinity sensitive. The objective of this study was to examine the effects of varying levels of nitrogen and irrigation water salinities on common stock flowers (Matthiola incana) with a plant growth model and make recommendations as to the minimum nitrogen levels and maximum salinities that can be tolerated while maintaining quality flower production. While increased salinity modified the plant growth rates, higher than previously thought salinities can be tolerated in stock production. The reduction of applied nitrogen to 35 ppm from the normally applied rate of 100 ppm resulted in no differences in quality but potentially reduces nitrogen discharge potential off-site.