Monopotassium phosphate is a widely used phosphorus and potassium fertilizer for ornamental plants, but it is not known what concentration will result in optimal flower production, root growth, and nutrient uptake of rose plants. This study compared potted rose plants fertilized with six different concentrations (0.0 as a water-only control, 1.0, 2.0, 3.0, 4.0, and 5.0 g·L−1) of an aqueous monopotassium phosphate solution as a combination of foliar and soil applications over two consecutive flowering cycles.
Rose growth, flower production, and nutrient accumulation responded differently to fertilization with different concentrations of monopotassium phosphate. During the first flowering cycle, shoot and root dry weight, leaf chlorophyll content, flower diameter, total root length, surface area, and total fine root length significantly increased in response to increased monopotassium phosphate concentrations from 0.0 to 3.0 g·L−1 but decreased in response to fertilization with 4.0 or 5.0 g·L−1 monopotassium phosphate. Similar trends were observed in shoot dry weight, leaf chlorophyll content, flower diameter and number, phosphorus, and potassium accumulation during the second flowering cycle.
According to quadratic equations derived from both flowering cycles, the optimal concentration of monopotassium phosphate, based on flower diameter and dry weight, as well as total phosphorus and potassium accumulation, was 2.6–3.0 g·L−1. Furthermore, total root length was significantly correlated with flower diameter, flower dry weight, and total phosphorus and potassium accumulation (p < 0.05). These results indicated that fertilization with optimal concentrations of monopotassium phosphate can increase rose growth, flower productivity, and nutrient uptake through enhanced root growth.
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Ma, Qinghua & Wang, Xinghong & Yuan, Weijie & Tang, Hongliang & Luan, Mingbao. (2021). The Optimal Concentration of KH2PO4 Enhances Nutrient Uptake and Flower Production in Rose Plants via Enhanced Root Growth. Agriculture. 11. 1210. 10.3390/agriculture11121210.