1a. Objectives (from AD-416):
To determine plant growth, water use, and carbon footprint of sugarcane and/or other energy plants in the HC&S croplands in Maui, Hawaii.
1b. Approach (from AD-416):
Eddy covariance systems will be installed to measured crop ET and net CO2 exchange. On-site sensor maintenance including sensor replacement if needed, repositioning sensor height as plant grows, switching batteries as system power reserve will be performed. Measurements of fraction of ground canopy cover and canopy height will also be carried out on satellite overpass days. A plot study will be carried out to develop and validate algorithms for detecting and determining water stress and water use efficiency using thermal remote sensing. Periodic ground measurements will include canopy temperature, leaf stomatal conductance, fraction of ground canopy cover, canopy height, leaf area index, and final yield. Soil core samples for carbon stock assessment will be taken from multiple depths and locations near planting and after harvest. Soluble organic carbon and total soil carbon and nitrogen will be analyzed. Plant parameters needed for ALMANAC model simulation will include documentation of green-up, faction of intercepted PAR, leaf area index, within season try weight and nutrient concentrations, and final dry weight.
3. Progress Report:
The goal of this project is to determine plant growth, water use, and carbon footprint of sugarcane and/or other energy plants in the HC&S croplands in Maui, Hawaii; this research directly contributes to objective 1 of the in-house project 5320-21610-001-00D which this project was originally established under (expired in FY2011). Primary field sites were installed at four locations on Maui, three “variety trial” sites that occur along a gradient representative of various climates in Hawaii where feedstock production is likely to occur and one “deficit irrigation trial” where four species are grown at 100%, 75%, and 50% of current field practice. The baseline soil samples, collected from 10 coring sites at each study site were processed for total profile bulk density, carbon (C) concentration, and C stock. Extractable soil nitrogen (NH4+, NO3-), phosphate, CEC and base saturation will be determined for the top 1.6 m. The Maui project field team was hired to provide project management and field support for the Parlier and Temple USDA-ARS teams as well as UH Manoa collaborators. The field team regularly collected data on soil moisture (Diviner & ECH2O), light interception, biomass/yield, and leaf area for the primary field locations and different crops to monitor datasets for a series of plant and soil parameters as necessary for ALMANAC model simulation. Scheduled harvests for all crops occurred regularly with the field team’s participation. Tetracam images and crop scan of field sites were collected biweekly in concert with the remote sensed satellite data for calibration and routine maintenance and troubleshooting were conducted. The two Eddy flux towers were maintained and cleaned, adjusted, and troubleshot as needed. The field team also provided support for visiting ARS researchers, primarily collected soil and plant samples, and sensor calibration, and provided other services as requested. A variety of data were routinely collected from the deficit irrigation trial, led primarily by a graduate assistant in the NREM Department. For many of the datasets, both monthly monitoring and event-based data were collected for both sugar cane and napier grass. Minirhizotron images were scanned monthly to detect long-term changes in root structure and turnover as a result of deficit irrigation. Greenhouse gas (CO¬2, CH4, and N2O) fluxes were measured using the static chamber method monthly and more frequently before-during-after events such as harvest (for napier grass) and fertilization. At the end of this fiscal year, the one-year anniversaries of planting began to arrive and 1-m soil cores were collected to be analyzed for nutrients and change in C stock as a result of planting and sustainable ratoon harvest (for napier grass).