Land Retirement Demonstration Project

The Growth-form and Herbicide Trial

Overview

The Growth-form and Herbicide Trial (Figure 1)was developed to examine how specific seed mixtures, in combination with specific herbicides could produce good ground cover, lower competition from weeds, and ultimately affect long-term planting success. Three seed and herbicide "treatments" were applied: 1) the "Grasses Treatment", a mixture of native grasses with an application of broadleaf herbicide {Weedar 64®} the "Broad-leaf Treatment", a mixture of native forbs with an application of a grass-specific herbicide {Sethoxydim}; and, 3) the, "Late-Season Treatment", a mixture of late-germinating perennial species with an early application of a broad-range herbicide {Glyphosate}.

Plots were ca. 0.2 ha (0.5 ac) in size; a complete randomized block design was applied, with each treatment and a control (i.e., no treatment) replicated four times. The species mixture for each treatment is given in Table 1. The plots were seeded on 20 November, 2002. The Forb and Late-season treatments were imprinted. Originally, it was intended that the Grass treatment would also be imprinted; however, the long awns on some of the seeds did not feed properly through the imprinter hopper. Therefore, for this treatment the seed was first broadcast over the plot, and was then worked into the soil by a pass with an empty imprinter. Herbicide for the Grass treatment was applied on the last week of February; herbicides for the other two treatments were applied in the middle of March.

Vegetation monitoring of the Grass and Forb treatments and the control plots was conducted during May, 2003. Monitoring of the Late-Season plots was timed to coincide with the plants having attained their maximum growth for the season. Monitoring of these plots occurred on 8 November, 2003. Data were collected from twelve quadrats (35 x 70 cm) per plot, for the Grass, Forb and Control plots. The Late-Season plots received a higher-density of sampling, with 24 quadrats (100 cm x 150 cm) per plot.

Figure 1. Experimental design of the Growth-form and Herbicide Trial.

Table 1. Species planted in the Growth-form and Herbicide Trial. Seeding rates are expressed as pure live seeds per square foot (PLS/ft²). Key to treatments: G, Grass Treatment; B, Broad-leafed Treatment; LS, Late-season Treatment.

Taxon	Family	Common Name	Life-form	G	BL	LS
Allenrolfea occidentalis	Chenopodiaceae	iodinebush	shrub	-	-	14.03
Aristida ternipes	Poaceae	spreading three-awn	perennial herb	10.17	-	-
Atriplex polycarpa	Chenopodiaceae	allscale saltbush	shrub	-	-	4.88
Bromus carinatus	Poaceae	California brome	perennial herb	9.92	-	-
Eschscholzia californica	Papaveraceae	California poppy	annual herb	-	7.20	-
Frankenia salina	Frankeniaceae	alkali heath	perennial herb	-	-	14.52
Gilia tricolor	Polemoniaceae	bird's-eye gilia	annual herb	-	12.63	-
Grindelia camporum	Asteraceae	gumplant	perennial herb	-	-	10.04
Heliotropium curassavicum	Boraginaceae	seaside heliotrope	perennial herb	-	-	10.27
Hemizonia pungens	Asteraceae	common spikeweed	annual herb	-	9.79	-
Lasthenia californica	Asteraceae	California goldfields	annual herb	-	15.62	-
Lupinus bicolor	Fabaceae	bicolored lupine	annual or perennial herb	-	12.76	-
Nassella cernua	Poaceae	nodding needlegrass	perennial herb	7.40	-	-
Nassella pulchra	Poaceae	purple needlegrass	perennial herb	17.05	-	-
Phacelia ciliata	Hydrophyllaceae	Great Valley phacelia	annual herb	-	9.43	-
Sporobolus airoides	Poaceae	alkali sacaton	perennial herb	16.07	-	-
Suaeda moquinii	Chenopodiaceae	bush seepweed	sub-woody perennial	-	-	4.96
Vulpia microstachys	Poaceae	small fescue	annual herb	8.78	-	-

Page created: March 1, 2005; Last updated: January 17, 2006