Study On Effects Of Dolomitic Lime On Peat PH

Growing medium is the key of greenhouse crop production. The chemical and physical properties of medium directly affect the plant growth. The pH is an important chemical property of growing medium. Peat is the main component of growing medium. The peat pH is commonly low around 4.0. Lime is the best adjusting material to low peat pH. Several researches on pH adjustment of growing medium were conducted in broad. M. J. Maher,M. Prasad( 1998) reported the effect of peat type and lime on growing medium pH and growth of Heber Pinguifolia 'Southerlandii'. D. J. Eakes, C. H. Gilliam, G. J. Keever, and J.W.Olive have studied that dolomitic lime and micronutrients affected on the growth and quality of container-grown ornamentals. The testing methods of greenhouse growing media were development from Soil and Plant Testing Laboratory, University of Missouri. Because of the constituents and properties of peat materials from China are different from broad. The research results on peat moss pH adjustment from other country can not be used directly in greenhouse production in China. The experiments were conducted to study the effects of lime on peat pH by using incubate method at 25℃±2℃ in a controlled environment chamber and the influence of initial water content of medium on lime adjusting pH. The research results are as follows:1. The ratio of peat pH change following incorporation of lime varied with lime rates, lime particle sizes. 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 at 12th day.2. Lime rates influenced pH_H2O change of media. The pH increment of media was reduced with the increase of lime rates. The effects of different lime rate on vermiculite pH_H2Owas not obvious, pH_H2O of mixed media with peat was mainly dirercted by the property of peat.3. Lime particle sizes affected pH change of peat. Particle sizes influenced not only on the final increment of pH, but also on the rates of pH...