Characterization of the physico-chemical properties of environmentally friendly organic substrates in relation to rockwool

Abstract

SummaryTrials over two years aimed to characterize the physico-chemical properties and high-temperature responses of ecologically sound untreated organic substrates coconut (Cocos nucifera L.) coir and carbonated rice husk in relation to that of rockwool using tomatoes (Lycopersicon esculentum Mill.) as a test crop. In all substrates, water-filled pore space and water holding capacities were larger and air filled pore space was smaller. Bulk densities, water holding capacity and water-filled, air-filled and total pore spaces were lower in carbonated rice husk than coconut coir and rock wool. These values in coconut coir and carbonated rice husk were much increased with use. Most of the chemical properties, namely cation exchange capacity, electrical conductivity, pH, nitrate-N, P, K, Ca and Mg of these substrates were within recommended levels as growing media. There were no significant differences in plant height, stem diameter, individual fruit weight, percent fruit set, harvest index, ascorbic acid, total soluble solid, fruit pH, leaf chlorophyll contents, root dry matter percentage, fruit dry matter percentage and shoot/root ratio. There was less fluctuation in absolute growth rate, relative growth rate, net assimilate rate and leaf area ratio among the treatments. It also appeared that carbonated rice husk and coconut coir gave better crop performance and yield of tomatoes than rock wool under high temperature stress conditions namely 30°C and 35°C as compared with 25°C. Furthermore, crop productivity from the organic substrate coconut coir gave more profit than the popular rock wool. Thus, carbonated rice husk and coconut coir can be used successfully as a growing media amendment for producing fruit vegetables. .