The Seed Augmentation and Planting Method Trial, and its "sister study", the Herbicide and Charcoal Treatment Trial, represent a collaborative effort among the US Bureau of Reclamation (BOR; Dr. Ken Lair, Technical Service Center, Denver; and Land Retirement Program, Fresno), the Endangered Species Recovery Program, Dr. Joe DiTomaso (University of California, Davis; UCD), and the Lockeford Plant Materials Center (Dr. Dave Dyer; USDA-NRCS; Lockeford) to conduct research addressing native plant community establishment on cropland dewatered through acquisition of water rights ("land retirement") by BOR and/or Westlands Water District (WWD). The two studies have been implemented as part of the research thrust of the Land Retirement Demonstration Project (LRDP), implemented under the authority of the California Central Valley Project Improvement Act (CVPIA).

The research involves evaluations of species suitability (with implications for mixture formulation), species propagation and seed increase, seed conditioning, seed harvest and planting methods, soil amendments, and weed control. Study objectives emphasize subsequent development of revegetation prescriptions for land owners throughout WWD, with emphasis on restoration of native shrub/forb and salt desert scrub plant communities that a) enhance habitat values for endangered species (e.g., kit fox, giant kangaroo rat); b) provide livestock grazing resources compatible with habitat goals; and c) result in site stabilization and weed suppression.


The Seed Augmentation and Planting Method Trial (5.6 ha; installed November 19-25, 2003) is a replicated, [3x4x4] factorial study evaluating effects of three factors on establishment success of eight native grass, forb and shrub species (Table 1). Treatment factors were: a) mechanical soil surface (seedbed) manipulation; b) cover crop use; and c) chemical rhizosphere augmentation.

Mechanical surface treatments addressed drilled seeding across variable depths and row spacing of "deep-furrow" seed placement (furrow depth: 1 cm [control standard], 10 cm, and 20 cm; row spacing: 30 cm [control standard] and 45 cm). Deep-furrow seed placement is designed to increase precipitation capture and retention, creating seed germination micro-sites exhibiting lower salinity and increased protection from environmental extremes. Second-level treatment involved use of a dryland barley "nurse crop" seeded at typical agronomic rates (68 kg ha-1) in alternate rows (60 cm and 90 cm spacing) with seeded natives to evaluate effects on weed suppression and further buffering of climatic extremes. Third-level rhizosphere augmentation involved combinations of treatments for sodium reduction using banded application of HydraHume® at 112 kg ha-1; banded phosphorous fertilizer (0-45-0 super treble PO4 at 45 kg ha-1); and polymerized, clay-based seed coating (2:1 seed weight ratio). Influence of pre-treatment soil parameters will also be analyzed, including surface and subsurface texture, pH, sodium adsorption ratio (SAR), electrical conductivity (ECe), and major nutrients.

Plant counts for native and weed species, utilizing ten 1,500 cm2 (30 cm row spacing) or 2,300 cm2 (45 cm row spacing) within-row quadrats per row, were conducted during the first growing season (April 26-30, 2004) for cool-season species to provide estimates of species germination, emergence and survival (stand success). Because of extreme drought conditions after this date, emergence of warm-season species was insufficient to warrant data collection in 2004. April monitoring data is currently being analyzed. Eventually, results from this trial will be posted here.

Table 1. Species planted in the Seed Augmentation and Planting Method Trial, Tranquillity site 2003-04.

TaxonFamilyCommon NameLife-form
Atriplex polycarpa Chenopodiaceae allscale saltbush shrub
Hemizonia pungens Asteraceae common spikeweed annual herb
Isocoma acradenia Asteraceae goldenbush shrub
Lasthenia chrysantha Asteraceae alkali goldfields annual herb
Phacelia ciliata Hydrophyllaceae Great Valley phacelia annual herb
Sporobolus airoides Poaceae alkali sacaton perennial herb
Suaeda moquinii Chenopodiaceae bush seepweed sub-woody perennial
Trichostema ovatum Lamiaceae San Joaquin bluecurls annual herb

Page created: March 1, 2005; Last updated: Dec. 20, 2005