The Growth-form and Herbicide Trial


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 showing the layout of the plots in this trial

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.

TaxonFamilyCommon NameLife-formGBLLS
Allenrolfea occidentalisChenopodiaceaeiodinebushshrub--14.03
Aristida ternipesPoaceaespreading three-awnperennial herb10.17--
Atriplex polycarpaChenopodiaceaeallscale saltbushshrub--4.88
Bromus carinatusPoaceaeCalifornia bromeperennial herb9.92--
Eschscholzia californicaPapaveraceaeCalifornia poppyannual herb-7.20-
Frankenia salinaFrankeniaceaealkali heathperennial herb--14.52
Gilia tricolorPolemoniaceaebird's-eye giliaannual herb-12.63-
Grindelia camporumAsteraceaegumplantperennial herb--10.04
Heliotropium curassavicumBoraginaceaeseaside heliotropeperennial herb--10.27
Hemizonia pungensAsteraceaecommon spikeweedannual herb-9.79-
Lasthenia californicaAsteraceaeCalifornia goldfieldsannual herb-15.62-
Lupinus bicolorFabaceaebicolored lupineannual or perennial herb-12.76-
Nassella cernuaPoaceaenodding needlegrassperennial herb7.40--
Nassella pulchraPoaceaepurple needlegrassperennial herb17.05--
Phacelia ciliataHydrophyllaceaeGreat Valley phaceliaannual herb-9.43-
Sporobolus airoidesPoaceaealkali sacatonperennial herb16.07--
Suaeda moquiniiChenopodiaceaebush seepweedsub-woody perennial--4.96
Vulpia microstachysPoaceaesmall fescueannual herb8.78--

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