Effects of Reduced Phosphorus on Plant Growth and Flowering of Lantana

The application of phosphorous (P) fertilizer is an integral part of greenhouse and nursery crop production, however, over-application of P above the crop needs is a common practice, leading to higher production costs and higher risk for P runoff and leaching to the environment. This study was conducted to determine optimum concentration of P which helps maximize crop quality and minimize environmental impact. Rooted cuttings of Lantana camara ‘New Gold’ were grown with complete nutrient solutions containing  1, 3, 5, 10, 20, or 30 mg·L^-1 P, and plant growth and flowering characteristics were recorded for 8 weeks. Plants were harvested at 3 weeks and 8 weeks for shoot and root analysis. P contents were determined from different parts of plants and phosphorus use efficiency (PUE) was calculated as the amount of biomass produced per gram of P taken up by the plant. P promoted plant growth from the first week after transplanting. In general, plant size and the numbers of branches and leaves increased with higher P. However, plants grown with lower P were more compact, and flowered at the same time as the ones grown with higher P and produced the same number of flowers per unit area. Flower size was not significantly different when the P level was higher than 10 mg·L^-1. Similarly, root length, surface area, and volume increased as P level increased, however, the root-to-shoot ratio significantly decreased with higher P. Although higher P application increased P content is plant tissues, particularly in flowers, plant had greater PUE when grown with lower P ranging from 3 to 10 mg·L^-1. Our results demonstrate that reduced P application does not cause major negative impacts on the growth and flowering of Lantana and, in fact, it may be useful to sustainably control the size of plants with stronger roots.