Soil and Water Quality with Miscanthus on a Louisiana Coastal Plain Hillside L. Gaston and W. Felicien LSU AgCenter School of Plant, Environmental and Soil Sciences

Rationale Marginally productive land used for pasture and timber may be more productive with non-pasture, biomass grasses Good for the landowner / producer and local community Positive direction with respect to energy dependency and climate change Depends on sustainable production without negative environmental effect Objectives Yield Nutrient dynamics Soil quality Water quality

Overview of the Experiment Location, Field Plot Design, Study Components and Methods Location LSU AgCenter Calhoun Research Station, Calhoun, LA Western Coastal PlainMLRA 133B Ruston-Lucy Association, Hilly – a sandy loam, acidic soil Specific site had not be used for years

Field Plot Design Miscanthus giganteus transplanted spring 1 plant m -2 Treatments applied 2010 RCB design 3 replications with blocks perpendicular to slope (high, middle and low) Plots 5 m x 5 m with 2 m border between plots and 5 m buffer between blocks Treatments include Inorganic 80 and 160 kg ha -1 N-based poultry 80 and 160 kg ha -1 No fertilization control No miscanthus, no fertilization = native vegetation control Harvest fall to winter for biomass productivity and tissue composition

Runoff Water Quality Sub-plots (3/4 m x 2 m stainless steel, 10 cm walls, 5 cm deep trough with drain) In all poultry litter, no fertilizer control and native vegetation plots (12 sub-plots) Parameters include volume, TS, DS, SS, COD, DOC, NH 4 +, NO 3 -, TP, DRP and pH All runoff > ~ 200 mL analyzed Begun after treatments applied 2010 Soil Quality Extractable nutrients, OC and FDA hydrolysis Sampling in late winter before re-growth

Results Yields Treatment Mg ha N5.79 a6.81 a 80 N inorganic4.49 a4.99 a 160 N inorganic7.36 a7.82 a 80 N poultry litter7.30 a7.98 a 160 N poultry litter7.81 a8.69 a Low yields and no effect of fertilizer rate or source

Nutrient Removal in Harvest 2011 TreatmentCaMgPKS kg ha N N inorganic N inorganic N poultry litter N poultry litter Negligible depletion of soil nutrients 2010 similar

Soil Quality Parameters OC Treatment % N0.80 a b c0.80 a 80 N inorganic0.67 b c0.78 a 160 N inorganic0.65 c0.74 a 80 N poultry litter0.88 a 0.94 a 160 N poultry0.88 a0.84 a Native vegetation0.83 a b 0.82 a Average

FDA Hydrolysis Treatment micromoles g -1 h N0.17 a0.13 a 80 N inorganic0.17 a0.16 a 160 N inorganic0.16 a0.12 a 80 N poultry litter0.16 a 0.14 a 160 N poultry0.12 b0.13 a Native vegetation0.16 a 0.15 a

Runoff Water Quality 2010 TreatmentTSDOCNH 4 + NO 3 - TPDRP kg ha N32 a b 9 b0.3 a0.1 a0.3 a0.2 a 80 N poultry litter42 a b 7 b0.2 a0.2 a0.3 a0.3 a 160 N poultry25 a b 8 b0.3 a0.1 a0.5 a0.4 a Native vegetation64 a 20 a0.5 a0.2 a0.3 a0.2 a N34 a 4 a0.2 a0.1 a0.1 a0.1 a 80 N poultry litter13 a 2 a0.1 a0.1 a0.1 a0.1 a 160 N poultry19 a 5 a0.2 a0.1 a0.3 a0.3 a Native vegetation35 a 11 a0.2 a0.5 a0.1 a0.1 a

Discussion Some indication that miscanthus performs better at lower landscape position, or performs worst at higher position Block2010 Yield2011 Yield Mg ha High4.82 a4.78 b Middle7.38 a9.31 a Low7.79 a7.69 a b Runoff depth follows this trend but differences are not significant Little runoff from high position at this site is consistent with measured K SAT K SAT = 12.3 ± 6.0 cm h -1 (single ring method)

Fast topsoil drainage may reduce available water in absence of less permeable subsoil Yield data are inversely related to depth to Bt Negative relationship between miscanthus yield and depth to the Bt horizon. Data exclude plots from which sample to 1 m could not taken due to wetness (lowest block). Three plots from the highest block had no Bt within 1 m. Depth to these in this figure and the regression was taken as 100 cm.

Negative relationship between relative yields of miscanthus within treatments and relative depths to Bt within plots of the same treatment –normalized yields and depths to Bt within treatments.

Subsoil fertility may contribute, however, there is no significant relationship between topsoil chemical fertility and yields Seep areas below lowest block indicates fairly shallow saturation Further Planned Work Depth to saturation unknown –install wells to determine behavior Fertility level at site is low to very low for common pasture grasses Raise baseline fertility and continue

Summary Yields of miscanthus are low, e.g., 7.3 ± 3.5 Mg ha -1 in 2011, third year Water may be limiting miscanthus and soil heterogeneity obscuring treatment effects In contrast, second year (2011) yields of switchgrass at this site were 23.5 ± 3.8 Mg ha -1 Miscanthus appears to be neutral in effect on measures of soil and water quality, i.e., the same as diverse, open-land vegetation Loss of nutrients in runoff is negligible from miscanthus, even where poultry litter is applied at ~ 3 and 6 Mg ha -1 Presumably due to low high infiltration and low soil fertility