Effect of different levels of nitrogen, phosphorus, and potassium on root activity and chlorophyll content in leaves of Brassica oleracea seedlings grown in vegetable nursery substrate

Nutrients in the substrate are important for plant growth, particularly during the development of vegetable seedlings. The continued development of intensive methods to produce seedlings has made growing healthy and high-grade seedlings a requirement for nurseries. This study evaluated the effect of nitrogen (N), phosphorus (P), and potassium (K) on the root activity, dry weight, and chlorophyll content in leaves of Brassica oleracea seedlings. D-optimal design was used in this study because of its accuracy. A total of 10 treatments (T1-T10) were designed, and different concentrations were chosen in the following ranges: N (0.6-5.0 g center dot kg(-1)), P (0.2-6.0 g center dot kg(-1)), and K (0.7-7.0 g center dot kg(-1)). Our study shows that the application of N, P, and K to the substrate significantly influenced the growth of B. oleracea seedlings. T6 significantly increased root activity, root dry weight, chlorophyll content in leaves when compared with the control T1, which had added nutrient concentrations at normal levels. However, the addition of high levels of N (5.0 g center dot kg(-1)) with high (7.0 g center dot kg(-1)) or low (0.7 g center dot kg(-1)) levels of K (T2 and T9) not only significantly decreased the root dry weight but also decreased leaf area. Our results suggest that N, P, and K can be added to the substrate at an appropriate ratio to grow vigorous B. oleracea seedlings under intensive seedling production conditions. The present results give insight into the nutrient requirements during early growth of B. oleracea seedlings in growth substrate.