Release characteristics and planting effects of promoted-release mixed phosphate and magnesium substrates

Four promoted-release materials (W, Y, QW, and FS) were chosen to activate the mixture of phosphate rock and calcined magnesium oxide. Type Ⅰ and type Ⅱ mixtures of promoted-release phosphate rock and calcined magnesium oxide were added to 3% and 5% promoted-release materials, respectively. Next, promoted-release mixed phosphate and magnesium substrates for herbaceous flowers were prepared, whereas a leaching experiment and a pot experiment were conducted to study the release characteristics of water-soluble P and Mg and their effects on growth and flowering of Torenia fournieri and Catharanthus roseus. The results were summarized as follows: 1) As compared with the substrate without adding any promoted-release materials, the water-soluble P contents of promoted-release P-Mg substrates added with W, Y, QW, and FS were significantly increased by 15.42%~27.10% (P<0.05), whereas the water-soluble Mg content in treatments added with W, Y, QW, and FS showed no significant differences (P>0.05). 2) Promoted-release P-Mg substrates added with W I increased the number of flowers of T. fournieri and the crown diameter, branch number, and above-ground biomass of C. roseus; substrates added with FS-Ⅱ promoted the accumulation of above-ground biomass of T. fournieri, but adding Y-Ⅰ showed no positive effects on the growth of T. fournieri or C. roseus. Generally, promoted-release W-Ⅰ and FS-Ⅱ showed positive effects on substrates of herbaceous flowers and the appropriate addition ratios were 3.09 and 3.16 kg·m-3, respectively.