Effects of Fertilizer Source and Rate on Zinnia Cut Flower Production in a High Tunnel

Sustainable nutrient management in high tunnel production is critical for optimizing crop yield and quality and improving soil health. In this study, we investigated the influence of different pre-plant composts (composted broiler litter, vemicompost, and cotton gin compost) in combination with different rates of organic or conventional fertilizer on zinnia plant growth, marketable yield of cut flower stems (>30 cm), and soil nutrients in a high tunnel over two years. Results showed that in general, pre-plant compost influenced plant growth, and plants that received composted broiler litter had the highest plant growth index. However, pre-plant compost did not affect the number of marketable cut stems. Fertigation during the growing season influenced the number of marketable cut stems. Comparable rates of nitrogen, from either organic or conventional fertilizer, produced similar numbers of marketable stems, suggesting that the organic fertilizer used in this study can be used as a fertilizer source for the production of zinnia cut flowers. After two years of production under the high tunnel, soil-extractable phosphorus, sodium, zinc, and pH significantly increased, suggesting that salt accumulation should be closely monitored in response to different compost or fertilizer sources with long-term production under high tunnels.