Prairie Restoration: Increasing Warm-Season Native Grasses with Fire, Herbicide, and Nitrogen Application

Shauna Waughtel, S.A. Clay, A. Smart, D.E. Clay, and L. C. SchleicherSouth Dakota State University, Brookings, SD 57007

AcknowledgmentsPartial funding provided by SDSU Ag Experiment Station and USDA/CSREES Grassland #2008-38415-19596

Thank you to Millborn Seeds.Thank you to fellow grads, student workers and volunteers.

Figure 7: NDVI distribution for Artesian 6/28/2010. Pr>F <0.0001Mean canopy differences between herbicide treated plots compared to fire or nitrogen treatments. Glyphosate treatment resulted in less overall biomass at this time.

Figure 8: NDVI distribution for Artesian 8/24/2010. Pr>F 0.6151August crop scan shows no difference in photosynthetic capacities of canopies indicating chemical treatment plots recovered from herbicide stress.

Figure 6: NDVI distribution for Volga 6/30/2010. Pr>F 0.7892Photosynthetic capacity of plant canopy was not different by treatments.

Summary Comparison of baseline data collected in 2009

and treatment data collected in 2010 suggest warm-season cover increased as a result of May fire treatments.

Combining early fertilizer and mid-spring herbicide resulted in greater warm-season grass biomass .

Although initial cool-season biomass collections from N treated plots at Artesian in June 2010 resulted in greater cool-season grass biomass, warm-season biomass was stimulated when combined with N treatments by August.

The 2010 season had record setting rainfall, which may have helped to stimulate warm-season recovery.

Results

October 2009 herbicide application.Prescribed burning of Volga site by SDSU crew. Research plot immediately post burn. Re-growth six weeks post burn against untreated vegetation.

Introduction Tallgrass prairie currently covers ~3% of the

original expanse. South Dakota retains 470,000 ha of remnant prairie.

Loss of large herbivores, increased farming activities, and introduction of exotic, invasive species continue to threaten these prairie remnants.

Non-native grasses [smooth brome (Bromus inermis) and Kentucky bluegrass (Poa pratensis)], introduced post European settlement, are highly aggressive and outcompete native grasses [big bluestem (Andropogon gerardii) and blue grama (Bouteloua gracilis)] for resources.

Sensible, inexpensive management practices and producer education are needed in order to restore native species productivity to degraded areas.

Objective

The objective of this study is to determine if fire, herbicide, and nitrogen treatments can be used to suppress invasive species with concomitant reinvigoration of native species in eastern South Dakota.

Methods and MaterialsTwo sites: Volga , S. D. and Artesian, S. D.

Three blocks split into four subplots, randomized, and replicated four times. Subplots measures 3m by 6m.

 Treatments:Herbicide: Glyphosate - 2.27 kg/ha in October (after warm season grass senescence) or 0.57 kg/ha in May (post cool season grass emergence but prior to warm season emergence).Fire: Controlled prescribed burns completed just prior to early warm season species growth.Nitrogen: Ammonium nitrate applied at 72.4 kg/ha in April, June, or October/April.

Sampling (baseline Sept 2009; June and August, 2010):Vegetative biomass: Three 0.25 m2 quadrats/plot with vegetation separated into native and non-native grasses.Crop scan: Data of spectral reflectance collected in tandem with vegetation harvest. Normalized difference vegetation index (NDVI, ) was calculated using (NIR-Red)/(NIR+Red). NDVI is an index for photosynthetic capacity of the canopy.

Figure 1. Artesian baseline data collected September 2009.

Figure 2. Artesian biomass collected June 2010.

Figure 3. Artesian biomass collected by subplot August 2010.

Figure 4. Volga baseline data collected August 2009.

Figure 5. Volga biomass collected June 2010. Nitrogen plots had greater biomass at harvest time.

B B A

Baseline grass biomass was similar across plots in Artesian (Fig. 1) with greater cool than warm-season grass biomass.

Nitrogen treatment plots had greater cool-season biomass for June 2010 harvest , fire and herbicide treatments had slightly greater warm-season grass biomass (Fig. 2).

In August, fire treatments with or without N plots had double the warm-season and 50% less cool-season biomass than baseline amounts (Fig.3).

Glyphosate applied after an April N treatment had the greatest release of warm-season grasses (double baseline) and least amount of cool season grass biomass (50% less than baseline) (Fig.3).

April applied N without chemical or fire increased cool-season growth compared to other applications. (Fig.3)

Nitrogen significant at 0.05 level.

April

N

June

N

NoN

Oct

N

May

April

N

May

June

N

May

NoN

Oct

NoN

April

N

June

N

NoN

Oct

/Apr

il

Fire Herbicide Nitrogen

0100200300400500

Warm-Season Mean Biomass(g/m2) Cool-Season Mean Biomass(g/m2)

Fire Herbicide Nitrogen0

100200300400500600

Warm-Season Mean Biomass (g/m2) Cool-Season Mean Biomass (g/m2)

AB B A

Fire Herbicide Nitrogen0

50100150200250300350

Warm-Season Mean Biomass (g/m2) Cool-Season Mean Biomass (g/m2)

Nitrogen significant at 0.05 level.

B B A