Investigation of Drainage and Plant Growth from Nursery Container Substrate

Abstract

The amount of water and major nutrients lost through drainage from a nursery container substrate treated with different amounts of nitrogen (N), phosphate (P), and potassium (K), and potted with butterfly bush plants were investigated. The substrate was mainly composed of aged pine bark and steamed composted nursery trimmings as well as leftover potting mix from a commercial nursery. Plastic containers with nominal capacity of 3.8 L were equally divided into 10 groups containing the substrate with or without plants, and treated with different amounts of N, P, and K applied to the surface of the substrate. A total of 4.8 L of water was applied to the substrate in each container during a 28-day period of the test. There was 48.4% of NO3-N and 6.3% of P leached away when 0.8 g of NO3-N and 0.4 g of P were applied to the substrate in the container with plants during the test. The amount of nutrients in the substrate with the greatest plant growth and the lowest nutrient loss through drainage was 0.44 g for N and 0.18 g for P. Substrate with plants had less water drainage and nutrient loss than the substrate with no plants. When the substrate moisture content was below 25%, the maximum amount of water that could be added into the substrate with plants before drainage was 257 mL of water/L of the substrate. Excess fertilizers applied to the container plants resulted in high nutrient loss and low plant growth rate. Current fertilizer use rates should be reduced to improve nursery production efficiency.