Abstract

A by-product of the rice industry, burnt rice husk (BRH) is the main substrate in carnation crops in Colombia due to its low cost and high availability. This paper Characterizes the physical properties of BRH over a 100-week cycle in three farms on the Bogota plateau. Particle density, bulk density, particle size distribution, total pore space, container capacity, air space, available water, easily available water and water buffering capacity were determined. The data show that there are no significant differences between farms regarding the physical properties of the initial analysis. Therefore, the substrate used in all farms and greenhouses was reasonably uniform. Bulk density and particle density increased their initial values by 66% (0.12-0.19 g cm(-3)) and 2% (1.68-1.72 g cm(-3)), respectively but these values are within the optimal range. Low values of bulk density indicate that BRH is a very light material and the increase in bulk density suggests the compaction of the substrate with crop time. Over the whole crop cycle, total pore space (TPS) fell on average by 13% and air space (AS) by 40%, while container capacity (CC) increased by 30%. These values are within the range suggested as suitable for substrates. The decrease observed in TPS and AS over time corresponds to the break-up of coarse particles and the increase in bulk density. This may be the result of settlement by of the particles and may be strongly influenced by the mass of roots. Temporal variations in particle size distribution and their spatial reorganization affect all the hydro-physical properties of BRH. Substrate moisture retention capacity is increased, which alters the water/air relationship in the root environment. Based on the results obtained, fertigation criteria were proposed to improve fertigation strategies throughout the carnation crop cycle. (c) 2013 Elsevier B.V. All rights reserved.