Influence of steam-treated grass clippings on grass growth, drainage water quality and soil microbial properties in a simulated golf course

Abstract

The effects of steam-treated (hydrolytic process using high temperature 207°C and high pressure steam 1.6 MPaG for 30 min) grass clippings and their liquid residue on growth, drainage water quality and soil microbial properties were evaluated. Soils were placed in plastic containers (47 cm length × 40 cm width × 22.5 cm depth) so that the surface (0–10 cm depth) was a mixture of Andisol and sand (3:2 volume) and the subsurface soil (10–20 cm depth) was Andisol only. A basal dose of chemical fertilizer (25 g m⁻² NPK 8–8–8) and poultry manure (20 g m⁻²) was applied. The treatments were: CF (without incorporation of plant residues and 25 g m⁻² NPK 8–8–8 top dressing 1 month after transplanting), LL (1 kg m⁻² commercial leaf litter), GT (1 kg m⁻² steam-treated grass clippings), GT + BL (1 kg m⁻² steam-treated grass clippings plus 6 L m⁻² liquid residue in a single application as basal fertilizer), GT + FL (1 kg m⁻² steam-treated grass clippings plus 3.2 L m⁻² liquid residue diluted 10-fold and applied six times as fertigation), and GT10 (10 kg m⁻² steam-treated grass clippings). In all treatments, Manila grass (Zoysia matrella) was transplanted. The total dry matter yield of clippings was highest in GT10 (752 kg m⁻²), followed by GT (503 kg m⁻²), LL (491 kg m⁻²) and lowest in CF (378 kg m⁻²). Liquid residues did not show a positive effect on grass growth, probably because of low pH (4.5). Incorporation of high amounts of steam-treated grass clippings (GT10) can result in more nitrate leaching. The trends in microbiological properties in response to the different treatments were the same as the grass growth (GT10 > GT > LL > CF). Steam-treated grass clippings can enhance microbial activities and can partially replace chemical fertilizer. However, the incorporation of an adequate amount is necessary to minimize the environmental load by nitrate leaching. Liquid residue requires another form to be used.

Key words:

• grass growth
• leaching
• plant residues
• soil microbial properties
• waste recycling

ACKNOWLEDGMENTS

The authors thank Mr N. Shimoda of Ishikawajima-Shibaura Machinery for providing technical support to conduct this experiment. We also thank Dr Agnes T. Padre (International Rice Research Institute, Philippines) for valuable suggestions.