Location: Water Management Research
2013 Annual Report
Ground-based crop cover and spectral reflectance data were collected from two sugarcane tower fields from July 2011 until now. We also collected a series of satellite imagery to develop NDVI (normalized difference vegetation index) maps of HC&S farm. The model developed from crop cover measurements and NDVI values can be used to indicate crop growing status. Crop coefficient model was developed using satellite imagery, crop cover, and eddy covariance tower measurements. A series of satellite-based crop water use maps was developed. METRIC (Mapping evapotranspiration at high resolution using internalized calibration) model was also used to develop crop water use maps. Results of these two approaches need to be validated using the data from the second crop growing cycle.
We also collected soil samples from fields with different soil textures, sugarcane varieties, and sugarcane growing stages. Collected soil samples were dried, ground and analyzed for dissolved organic carbon (DOC), total carbon (TC), total nitrogen (TN) and nitrate nitrogen (NO3-N). Eighteen months data for the tower fields showed heavier soil texture had double amount of TC than lighter soils. In addition, higher DOC was found under heavier soils compared to lighter soils. For NO3-N we observed similar trend for both fields. Higher NO3-N was obtained for grand growth sampling, especially in heavier soil texture. At 18 month sampling (i.e., maturity stage), NO3-N concentrations in both fields decrease drastically. While lower TN was found on 18 mo. sampling compared to initial sampling results. Twelve months data for the variety trial showed no consistent sugarcane variety response with respect to soil type and growing stages. Eighteen and 24 mo. results will be necessary to clarify the soil C and N status.
As part of the evaluation to grow Brassica as feedstock crops for the Dept. of Navy biofuel project, three separate field trials were established in the westside of central California to grow two 20 acre and one acre of mustard and other Brassica varieties (pre-evaluated for salt and boron tolerance), respectively, on severe to extremely severe poor quality soils. Soil salinity ranged from 15 to over 50 dS/m and soluble boron (B) and selenium (Se) ranged from 15 to 30 mg B/L and 1 to 2.5 mg Se/L, respectively. Due to later planting and excessive salinity and soil B, toxicity symptoms were widespread on those varieties that survived under a salinity of less than 20 dS/m. All other plants from all varieties did not survive to produce seed in soil with salinity greater than 20 dS/m. Seed from surviving plants will be processed for their oil with on-site oil press at a later date. Collected soil and plant samples showed excessive accumulation of sodium, chloride and boron were toxic to the plants. Our results clearly show that plantings must take place during the winter utilizing rains and preferably in moderately saline soils of less than 10 dS/m and 10mg B/L. Winter plantings will be taking place in 2013 in moderate saline and B –laden soils to more accurately attempt to produce feedstock crops under these poor growing conditions. We are also in the process of analyzing the benefits and costs of growing biofuels at the farm-level, and evaluating accurate crop-water production functions for the biofuel crop and non-biofuel crops for both good and marginal land.