Chemical Properties of Some Organic Materials Available in Kenya as Components of Potting Substrate

Abstract

Production of quality nursery potted seedlings requires a proliferous root system that enables adequate acquisition of water, air and soil nutrients and this depends on the quality of substrate used. Soil has always been used as nursery and pot substrate but it has problems which include: aeration; drainage; non uniformity and chemical suitability. Therefore, development of alternative potting substrates with optimal chemical properties is necessary. The main objective of this study was to identify, formulate and characterize chemical suitability of forest soil, compost, pine bark and rice husks as alternative components of potting substrates. The experiment was conducted at Maseno University, Kenya between February and December 2004. Materials including pine bark (PB), rice husks (RH), forest soil (FS) and compost (CS) were collected and formulated into ten substrates; (100% FS), (75% CS: 25% PB), (50% CS: 50% PB), (25% CS: 75% PB), (75% CS: 25% RH), (50% CS: 50% RH), (25% CS: 75% RH), (100% CS), (100% PB) and (100% RH). These were potted and arranged in a CRD with four replications. The chemical properties; macronutrients, micronutrients, CEC, pH and EC were evaluated. The data was subjected to analysis of variance and separation of means done by Duncan Multiple Range Test. The levels of macronutrients and micronutrients were significantly (P 0.05) higher in substrate formulations of 75% CS and 50% CS formulated with either PB or RH than the control. The pH was significantly (P 0.05) different and generally acidic in all the substrates. Substrate formulations of 75% CS and 50% CS formulated with either PB or RH had CEC and EC within the optimal ranges of 6- 15meq/100cc and 1.5-2mS/cm respectively. The substrate formulations of; 75% CS: 25% PB, 50% CS: 50% PB, 75% CS: 25% RH and 50% CS: 50% RH had chemical properties within the recommended ranges and are therefore suggested as potting substrates. These results provide alternative potting substrate formulations to soil and give means of better utilization of agricultural and industrial waste materials.