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.
