Description
In agriculture, improper, excessive or poorly timed irrigation and fertilizer applications can result in increased pollutants in runoff and degraded water quality. Specifically, the cultivation of potted plants requires significant irrigation and fertilizer that leads to high nutrient leaching. In southern California, a large producer of nursery plants, waterways are often subjected to elevated nutrient concentrations, which stress the aquatic ecosystem. In this research, the specific objectives are to determine optimal irrigation and fertilizer application rates for minimizing nutrient concentration from nurseries. Altered irrigation and fertilizer application experiments were implemented and monitored at the San Diego State University's Santa Margarita Ecological Reserve, which contains a newly constructed 0.1 ha nursery. The study was conducted over a ten months period (November, 2007 to August, 2008). The nursery site was divided into eight plots (each 6-m wide by 18-m long), with each plot containing 540 plants consisting of four commonly used landscaping varieties (Box-Leaf Euonymus, New Zealand Flax, Lantana, French Lavender) in southern California. The experimental plots represented combinations of irrigation and fertilization practices with different methods and rates. In all cases, irrigation was fully automated based on soil moisture sensors. Irrigation induced runoff was sampled and analyzed for nutrient concentrations on a monthly basis. The growth rate, leaf nutrient content and plant yield were monitored monthly. To assess the effectiveness of the altered irrigation and fertilizer strategies, runoff water quality and plant yield were compared to control treatments. Drip irrigation system achieved more plant production (9%) against overhead irrigation while saving water by 23-64%. The plant quality was maintained under drip reduced fertilized plots. Nutrient export from drip system was lowered down by 5-35%. Considering installation and maintenance cost of emitters and pipes, the overhead system is found preferable. In overhead system, plant quality was maintained in reduce fertilized plots and saved water usage by 37-48%. If the treatments are accepted in market, southern California nursery growers will be economically benefited and nearby waterways quality and aquatic life will be improved.
