Abstract
Coconut coir has received much attention as an alternative medium for rockwool in soilless culture. In the present study, the application of used coir medium to soil as a reuse model of organic media was evaluated. Four kinds of organic materials were applied separately at a rate of 20 t ha-1 as follows: new coconut coir (NCC), coir media used in an energy-saving hydroponic system with half the concentration of the standard solution (UHS) and with the full concentration of the standard solution (USS), and compost (COM) made from horse manure and rice straw. Chemical analysis of the organic materials revealed that USS had accumulated two times more Mg, four times more Ca, and forty times more NO3-N than COM. The application of USS increased the soil porosity, cucumber growth and the contents of Mg, Ca and N in cucumber plants. After the 40-day cultivation of cucumber, the residual nutrient contents in the soil with USS application were similar to those with COM application, except for K and NO3-N. The content of NO3-N remaining in the soil with USS application was three times higher (170 kg ha-1) than that with COM. The prolonged retention of NO3-N in the soil with USS may be attributed to the high C/N ratio of coconut coir that led to the immobilization of excess N accumulated in the media, and then gradual release over time. The results suggest that used coir media could be reused as a soil amendment for enhancing porosity as well as a fertilizer providing accumulated nutrients from previous soilless culture.
