Impact of Soil Properties on NDVI As a Predictor of Miscanthus Sinesis Biomass.

Miscanthus sinensis is a perennial grass that is poised to be a dominant plant for commercial biofuel production. Normalized Difference Vegetative Index (NDVI) is a canopy vegetative index that is useful for predicting biomass yield production.  The objective of this research was to observe the effect of different soil conditions on the performance of NDVI readings to estimate Miscanthus sinensisbiomass. The study hypothesis was that changes in plant growth patterns, due to changes in soil physical properties, will affect NDVI readings.

Five different residual fertility levels were established by applying 0, 2.2, 4.5, 9.0, and 18.0 Mg/ha manure annually from 2000-2005 in 40 completely randomized plots (8 reps/level).  Miscanthus sinensis plugs were planted in July 2010.  In 2014, soil organic matter (SOM), bulk density (BD), aggregation were measured for each plot. NDVI measurements were taken daily with a handheld Greenseeker (NTech Industries).  Plant height (biomass proxy) and relative chlorophyll content (SPAD) were recorded daily.

Soil quality was improved with increase manure rate: increase in SOM and decrease in BD was observed as manure rate was augmented. Results indicate that there is an overall positive correlation between plant height and NDVI (r=0.80); NDVI and chlorophyll readings showed a correlation of r=0.99.  Plant height/biomass differences between residual fertility treatments increased in time. The trends in time of plant height and NDVI were similar between treatments. Using NDVI as a growth pattern indicator for M. sinensis between May-July 2014, it was observed that the correlation NDVI vs time did not show changes in plant growth patterns due to soil productivity levels.  Therefore, the alternative hypothesis was rejected, and it can be concluded that soil properties do not have a noticable effect on NDVI as a predictor of Miscanthus sinensis biomass. This observation may reveal the resiliency of the M. sinensis to environmental factors such as soil limiting conditions (e.g. low fertility).