Response of Vetiver Grass to Extreme Nitrogen and Phosphorus Supply

摘要

Due to its unique morphological and physiological characteristics, vetiver grass is tolerant to many adverse climatic and edaphic conditions, and recently it has been found to show a large capacity for recovering N and P from wastewater and polluted water. As a part of a project conducted to calibrate vetiver for use in a computer model-MEDLI (Model for Effluent Disposal Using Land Irrigation), a pot experiment was carried out to determine the maximum capacity of vetiver for N and P uptake in soil supplied with N and P at rates of 10 000 kg/ha/year and 1 000 kg/ ha/year respectively. Results show that vetiver grass has a very high capacity of absorbing N at elevated levels of N supply. Vetiver growth will respond positively to N supplied at rates of up to 6 000 kg/ha/year, with no adverse growth effects apparent up to 10 000 kg N/ha/year. These features make vetiver highly suitable for treating wastewater and other waste materials high in N. Vetiver requirement for P was lower than that for N, and no growth response was observed at rates exceeding 250 kg/ha/year. Its growth was not adversely affected at P application rates up to 1 000 kg/ha/ year. However, in combination with a high growth rate and high yield, the total amount of P uptake by vetiver was found to exceed those of other tropical and subtropical grasses.