Ameliioration and Conversion of Excessive Se to New Resources from a Plant-based System

Authors: Banuelos, Gary

Submitted to: Selenium Deficiency, Toxicity and Biofortification for Human Health
Publication Type: Book / Chapter
Publication Acceptance Date: 10/20/2009
Publication Date: 12/31/2009
Citation: Banuelos, G.S. 2009. Ameliioration and Conversion of Excessive Se to New Resources from a Plant-based System. Selenium Deficiency, Toxicity and Biofortification for Human Health. 21-23.

Interpretive Summary: The use of green plants and associated microbes for environmental remediation has been called "phytoremediation". This green technology is being developed for the management of metal(loid)-contaminated soils and waters via the processes of phytoextraction, phytovolatilization, and phytostabilization. The objective of these long-tern studies was to report on the derivation and novel utilization of potential bio-based products that were produced from different plants grown for the management of soluble Se in central California soils. Long term multi-year field studies were conducted with canola, mustard, broccoli, and cactus on field sites in central California. Water used for irrigation contained selenium and other salts. Canola and mustard plants were harvested for leaves and seeds, broccoli for florets, and cactus for prickly pear fruit. Seed was mechanically processed onsite for oil, and residual seed meal were collected, while cactus fruit were hand-harvested. Oil was processed into biofuel. Residual mustard seed meal was applied to Se-deficient soils, and its herbicidal effects and micronutrient uptake was evaluated in strawberry production, while canola seed meal was used as Se supplement in dairy feed trials. The multi-year field studies showed that these crops were moderately more effective for managing soluble Se than irrigated unvegetative sites. These on-going field studies show that the phyto-management of Se-contaminated soils by canola, mustard, broccoli, and cactus not only removes soluble Se that has accumulated on the soils after irrigation with Se-laden drainage water, but harvesting the crops produces cash value bio-based products.

Technical Abstract: The green technology of phytoremediation has being developed for the management of metal(loid)-contaminated soils and waters via the processes of phytoextraction, phytovolatilization, and phytostabilization. Based upon these processes a plant management remediation strategy for selenium (Se) has been developed for the Westside of central California. The objective of these long-tern studies was to report on the derivation and novel utilization of potential bio-based products that were produced from different plants grown for the management of soluble Se in central California soils. Long term multi-year field studies were conducted with Brassica napus var. Hyola (canola), B. juncea (mustard), B. oleracea var. Marathon (broccoli), and Opuntia ficas indica (cactus) on field sites in central California. Water used for irrigation had a range of Se from 0.100-0.150 mg L-1, B from 4-7 mg L-1, and a sodium sulfate-dominated salinity (EC) of 5-8 dS m-1. The multi-year field studies showed that these crops were moderately more effective for managing soluble Se than irrigated unvegetative sites. Losses of Se occurred via accumulation, volatilization and leaching from the upper soil profile. Mustard and canola seed yields were between 3 to 3.5 metric tons ha-1. Preliminary oil yields extracted from both seed types ranged from 570-600 liters ha-1 , which were available to be used for producing a B20 biofuels (20% oil blended with 80% diesel) after transesterification. The residual Se-enriched canola seed meal (~1.85 mg Se kg-1 ) added daily to animal feed rations increased milk Se concentrations to 65 ug/L from 37 ug/L in Holstein cows. Mustard seed meal incorporated into strawberry production prevented the emergence of at least 12 different types of weeds and increased concentrations of Se to 0.2 mg Se kg-1 DM and other nutrients, e.g., Ca, P, Zn, and Cu, in strawberry fruits. Moreover, Se concentrations were as high as 3.5 and 10.2 mg Se kg-1 DM in broccoli florets and in cactus fruit grown under field conditions with Se-enriched irrigation waters. Coupling phytomanagement of Se with the creation of new biofortified and byproducts, e.g., Se-enriched vegetables, animal feed, fertilizers, biofumigants, and even a byproduct like biofuel, may provide California growers unique opportunities to increase the environmental and economic sustainability of a plant Se-management system, while supporting the agriculture community in central California.