Study About Lime Application In PH Adjustment For Growing Media

pH is an important property of growing media. It affects the validity of nutrition, and that seedlings take in and utilize nutrition. Peat-based media whose pH value is lower are oftenused in seedling. Low rhizosphere pH is not beneficial to take in mineral nutrition for plants. Therefor, peat-based media is not used directly to cultivate seedlings before pH is adjusted. Research reports about adjusting pH of growth media are seen in broad, but the constituents and properties of media are different between in broad and at home. Too low pH value of peat-based media results in nutrient obstacle of plug seedling. Therefore, the experiments were conducted to know pH change over time after applying different rate and particle size lime, and the influence of initial water content of media on lime adjusting pH and on seedlings of Salvia splendens and Petunia hybrida. The results would put forward basic thoughts for adjustment of pH of seedling media. In this paper, all media were incubated at 25C+2C in a controlled environment chamberto analyze systematically lime-adjusting pH of peat-based seedling media. Lime was added to media, mixed thoroughly, wetted with distilled water, and mixed again to assure even distribution of constituents and thorough wetting of media. Sampling and determining pH were carried out in prescribed date. The research results are as follows:1. The rate of pH change following incorporation of lime varied with lime rate, lime particle size. The most rapid increase in pH occurred during the first five days of incubation, especially the first two days. In general, pH reached near-equilibrium values within eight to sixteen days, although pH continued to increase slightly thereafter. Finely ground lime tended to equilibrate more rapidly than coarse lime.2. Lime rate influenced pH change of media. The pH increment of media was reduced with the increase of lime rate. Lime at 2kg/m3-4.0kg/m3 or 4.0kg/m3 to 6.0kg/m3 was added to media whose initial pH was 4. 5 or so if lime particle size was smaller than 0.25mm or E. It is apparent that liming response of mixes cannot be predicted solely from the pH responses of the media constituents.3. Lime particle size affected pH change of media. Particle size influenced not only the final increment of pH but also the rate of pH change and time needed to reach near-equilibrium values. The higher of pH increment, the faster of change rate and the shorter time needed to reach near-equilibrium values, thesmaller lime particle size was. The pH increment of treatment with lime particle size <0. 25mm was the highest, whereas that of treatment particle size within 1.0-3. Omm was the lowest.4. Initial water content of media influenced the time needed to reach near-equilibrium values and the increment and rate of pH change. However, its influence was not significant. The difference of pH change was little when the initial water content was more than 140%. Little particle size lime would be added to seedling media at the eight to sixteen days before cultivating seedlings at 110% of initial water content in peat.5. There was significant in difference of influence of treatments on the agronomy properties of Salvia splendens and Petunia hybrida. The plant height, stem thickness and biomass of treatment Y1, Y2, Y7, Y11 and Y19 were better than others, for the pH value of these treatments can meet the need of plants to pH. Otherwise, those of treatment Y4, Y5 and CK were the worst.