Creeping bentgrass growth in sand-based root zones with or without biochar

- Organic amendments are typically added to sand-based golf greens.
- Biochar has excellent water and nutrient retention and decays very slowly.
- Several of the biochar-sand mixtures had greater bentgrass growth than the control.

Organic amendments such as peat moss and various composts are typically added to sand-based root zones to increase water and nutrient retention. However, these attributes are typically lost within a few years as these amendments decompose. Biochar is a high carbon, porous coproduct produced from the pyrolysis of phytobiomass. Its unique porosity gives it excellent water and nutrient retention properties. Additionally, unlike other organic amendments, biochar is extremely resistant to microbial decomposition. Pure calcareous sand (control) or mixtures of three different biochars and sand at 1, 5 and 10% volume biochar/total volume were tested. Bulk densities decreased while percent pore space increased with the addition of all three biochars at all of the addition rates. Water retention was greater than the control in all but one of the biochar treatments, and several of the biochar mixtures had values for compaction resistance similar to pure sand. Creeping bentgrass (Agrostis stolonifera L. 'Pure Distinction') plant heights, root lengths, and fresh and dry weights were evaluated in mixtures grown hydroponically in polyvinyl chloride tubes (112 mm outside diameter × 99 mm inside diameter) filled 30 cm deep with 1 cm diameter pea gravel, over which 30 cm of either pure sand or sand/biochar mixtures were added to mimic a United States Golf Association root zone. Five weeks after seeding, plants grown in several of the biochar mixtures had significantly greater fresh and dry weights, shoot heights and root lengths than the control. Based on these results it appears that the addition of certain biochars would improve water retention and increase overall plant growth in sand-based root zones.