Miscanthus sinensis in Marginal Soils: Impact of Low Input Management on Soil Quality.

Miscanthus sinensis is a perennial grass often used for biofuel production that may have remedial effects on degraded sites. This study was conducted to measure the effect of M. sinensis on soil quality indicators in a marginal soil with minimum inputs. The hypothesis states that over time, M. sinensis adaptability to soil limiting conditions improves soil quality. In 2010, M. sinensis was established in 40 randomized plots placed on a marginal soil (low fertility, low pH) previously used in a manure rate trial from 2000-2005. For this study, the five manure rates (0, 2.2, 4.5, 9.0, and 18.0Mg/ha) of the previous experiment represented different degrees of marginality (lower or no manure rates represented lowest quality/marginal soils).  The monitored soil quality indicators were available nutrients, organic matter, aggregation (mean weight diameter, MWD), bulk density (BD), and moisture retention; crop height (July-2014) was measured as an indicator of plant adaptability. In 2014, marginal soils showed lower moisture retention (0.32cm3/cm3), and higher BD (1.34Mg/m3), than better quality soils (moisture retention=0.35, BD=1.26Mg/m3). Although there were significant differences in soil indicators among varying quality soils, since M. sinensis establishment in 2010, these differences have been reduced. In 2011 and 2013, dry MWD and yield showed significant difference between marginal soils (2011MWD=23.8mm, 2011yield=4.2 Mg/ha and 2013MWD=13.9mm, 2013yield=19.5 Mg/ha) and better quality soils (2011MWD=10.3mm, 2011yield=8.7Mg/kg, and 2013MWD=16.4mm, 2013yield=28.6Mg/ha). However, in 2014 dry MWD and plant height became more similar among treatments, and showed no significant difference between the marginal (MWD=25.8mm, height=2.2m) and better quality soils (MWD=25.6mm, height=2.3 m); these observations may indicate that M. sinensis adaptability has helped to overcome soil marginality by improving soil environment and its productivity. Data suggests that the beneficial effect of M. sinensis on soil quality under soil limiting conditions with low input management may result in sustained biofuel crop production.