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United States Department of Agriculture

Agricultural Research Service

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Location: Water Management Research

2012 Annual Report

1a. Objectives (from AD-416):
1) Improve current decision making capabilities on HC&S land by building robust data on current practices (Temple, Parlier); 2) Create management plans to maximize yield and stability of feedstock production (Temple, Hilo); 3) Maximize bioenergy biomass stability and yield while minimizing environmental impacts at watershed scale (Temple, Parlier, Hilo); and 4) Improve water resource anagement and optimize biomass production for other production areas in the Hawaiian Islands and Pacific Basin (Temple, Hilo).

1b. Approach (from AD-416):
Objective 1:Develop spatial and temporal data sets form historic data for baseline analyses. Objective 2: Simulate current management impacts on feedstock yields and resource inputs. Objective 3: Demonstrate applicability of simulation approaches with validated present practices and explore watershed scale impacts of changes. Objective 4: Improve decision support for assessment of resource conditions, and utilize parallel computing and deep hydrology water balance.

3. Progress Report:
This project supports objective 1 of the parent project. There has been a recent, renewed interest in Hawaiian sugarcane as a biofuel feedstock. This research will contribute to the development of a decision support system to determine the feasibility of biofuel feedstock production and environmental sustainability on the HC&S sugar cane lands in Maui, Hawaii and assessments of other potential biofuel feedstock sources across the Hawaiian Islands and other areas of the Pacific Basin. During this reporting period, we operated and maintained two Eddy Covariance towers in contrasting climatic and soil conditions at the HC&S plantation, which directly measure net carbon balance, evapotranspiration (ET), and meteorological conditions through non-invasive atmospheric and soil observations. Data from the towers confirmed the extremely high productivity and radiation use efficiency of Hawaiian sugarcane. One surprising finding has been the lower than expected measured ET compared to predicted-ET from standard methods (FAO-56/ASCE). Research into this discrepancy is ongoing, and has important implications for scaling up biofuel production elsewhere in the Pacific Basin. Ground-based remotely-sensed data, spectral reflectance and crop cover, has also been measured. A series of Landsat-7 normalized difference vegetation index (NDVI) maps were developed to depict sugarcane canopy development over time. Crop cover was highly correlated with NDVI values calculated from image and ground data. The NDVI based canopy cover was used to estimate crop coefficient (Kc) curves for sugarcane plants. A series of satellite-based evapotranspiration (ETc) maps were developed to indicate crop water use information for sugarcane lands in Maui, Hawaii. Because of lack of quantitative and qualitative information on soil C and N with respect of Hawaiian sugarcane varieties, we collected soil samples from fields with different soil texture, management practices (i.e. burning before harvest vs. green harvest), four sugarcane varieties and sugarcane growing stages. Collected soil and plant samples were dried, ground and analyzed for total carbon (TC) and total nitrogen (TN). First year data for the tower fields showed heavier textured soils had higher TC than relatively lighter soils. There was no consistent response for TN and dissolved organic carbon. Also, there was no consistent sugarcane variety response with respect to soil type and growing stages. The research is ongoing and additional results will elucidate the soil C and N status for this growth environment.

4. Accomplishments

Last Modified: 05/26/2017
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