Presentation on theme: "Establishing Native Grass from Containers in Southern California"— Presentation transcript:
1Establishing Native Grass from Containers in Southern California David Bainbridge, Associate ProfessorAlliant International University10455 Pomerado RoadSan Diego, CA 92131andLaurie Lippitt, Project ManagerSoil Ecology and Restoration GroupSan Diego State UniversitySan Diego, CA 92182
2As Fr. Juan Crespi noted as he traveled north from San Diego in July 1769, We ascended a large grassy hill…and found ourselves on some broad mesas …all covered with grass… except here and there some very small oaks and chaparral.The conversion from perennial native grasses to weedy annuals was driven by overgrazing and fire suppression
3These native bunch grasses may live for hundreds of years, providing food and cover and reducing soil erosion. They remain green much longer than exotic annual grasses, reducing fire risk.Tests over 8 years with Nassella pulchra (purple needlegrass) have explored techniques for restoring grassland communities by container planting.
42. Study sitesFour sites were included; degraded canyon bottom land, degraded dry lands that had once been grassland, coastal sage scrub or chaparral with native grasses,and oak savannah.All had been overgrazed, several had been farmed and/or used for other activities that had eliminated native plants and damaged soils.
5Site: CSS/grassland: now abandoned lawn/eucalyptus Test 1. Plant ProtectionSite: CSS/grassland: now abandoned lawn/eucalyptusNasella pulchra (purple needlegrass) seedlings from 2 x 2 x 6 inch plant bands were planted in spring 1997 in a completely randomized design, twenty with and twenty without TreePee™ plant protectors. They were watered occasionally but equally during the first season, twice in 1998.After two years survival was 100%Protected plants were more than ten times as tall, mean 46.8 inches, and covered with seeds (600+ seeds were on a representative plant); while the unsheltered plants were only 4.4 inches tall with no seedsDifferences are attributed to grazing by cottontail rabbits, competition with exotic grasses and weeds, and environmental stress
6Site: Degraded oak savannah Test 2. Weed Control, Planting Density, Soil Amendments and Mechanically-assisted PlantingSite: Degraded oak savannahSixteen 4' x 4' plots and 6' x 6' plots were scraped 2-4 inches deep in December 1999 in an exotic grassland. 792 Nassella pulchra seedlings were planted with density and soil amendment/fertilizer treatments. Another 208 grass seedlings were planted in ripped slotsAfter five months an ANOVA was used to test dependent variables: percent cover Nassella pulchra, other species (including both native and non-natives), gopher tailings, and height of leaf blades (inches), percent grass producing seeds, and survivalAfter nineteen months the plots were monitored againIn June 2003, after 5.5 years, a quick survey was done
7After five months survival averaged 82% Plot size had no significant effect on dependent variables.Soil amendment had a significant effect on weeds (highest in the fertilizer +mulch plots at 36% cover, lowest in the control plots at 14%)63% of grass produced seed in mulch plots, only 14% in the control plotsMean height was inches with mulch v/s 8.7 inches controlSeedlings in ripped slots were not significantly different than the control plots in height, percent producing seeds, or survival.
8After nineteen months of drought survival had dropped to 41% Virtually all surviving plants had produced seedsNative grass cover in high density plots was 24%, low density plots, 7%.Grass seedlings were significantly taller in low density plots.61% survival in control plots and just 23% in the fertilizer + mulch plotsGopher activity highest in fertilizer + mulch plots at 29% cover, and the lowest in control plots at 3%.After five and a half years, weed regrowth and removal of pins and markers limited data collection, but survival averaged 22-29% in relocated plots.Ripped slots could not be relocated, so survival is probably very low.
9CSS/Grassland: now abandoned lawn/eucalyptus Test 3. FertilizerCSS/Grassland: now abandoned lawn/eucalyptusIn spring x 2 x 6 inch plant band grass seedlings were planted in a degraded area, scattered Eucalyptus, and no ground cover on the eastern side of the AIU campus.Fertilizer treatments included: a balanced fertilizer applied as a granular powder, 1 teaspoon Scott's (15:13:15), ; a Jobe fertilizer spike (10:10:04) selected for ease of installation; organic matter (a cup of rose mix, 0:0:0.1), to offset low soil organic material; and a control.Seedlings received intermittent drip irrigation in the summer, about a liter per month for the first year.Height was initially measured, but subsequent growth was monitored by measuring basal clump area. Survival and plant condition was rated: dead, 1 - poor, 2 - fair, 3 - good, 4 - excellent.Seed set was evaluated in Spring 2003.
10Survival was 100% for the first year Three plants set seed within three months of planting, all in the 15:13:15 fertilizer treatment.No grasses set seed in 2000 as a result of severe stress following a very dry winterBy midsummer 2000, most plants had died back, but mean basal area of the grasses with the 15:13:15 treatment was 6.24 inches2, followed by the control 4.37 inches2, the 12:10:4 at 2.88 inches2 and the rose mix 2.1 inches2.Plants were watered once in 2001 and 2002.In April 2003 the control plants were healthier and larger than the other treatments, with survival and basal area shown in Table 1.
12Table 2. Fertilizer effects on purple needlegrass, basal area Table 2. Fertilizer effects on purple needlegrass, basal area Mean basal area, sq. inches Treatment monthsControlOrganic matter 0:0.1:Scott's 15:13:Jobe's spike 12:10:
13Test 4. Fertilizer/tree shelter CSS/Grassland: now abandoned lawn/eucalyptusIn June 1999 ten grasses per treatment from 2 x 2 x 6 inch plant bands were planted to explore fertilizer effects. Treatments included: 1 teaspoon zinc fertilizer, testing zinc deficiency; 1/4 cup cottonseed meal (6:2:2), an inexpensive amendment to add organic matter, nitrogen and potassium; and 1/4 cup of a complex organic fertilizer, higher in P than N but with a mix of macro and micronutrients, approximately (3.5:6:1); and control.Half of each treatment received a Treepee plant protector.Plants were irrigated intermittently each summer, about 1 liter per month. Tree shelters were vandalized in winter 2002 and removed in March 2003.Height was initially measured, but monitored shifted to basal clump area. Survival and plant condition was also rated on the same scale as before.Seed set was monitored in Spring 2003.
14All seedlings survived the first year After 9 months, the tree sheltered grasses were 7.7 inches tall and the unsheltered grasses were only 5.8 inches tall.There was no statistically significant difference in health between fertilizer treatments.Results changed as irrigation was discontinued and the drought deepened. A number of grasses died during the drought (compounded by competition with eucalyptus roots).Following winter rains in the survivors grew quickly and many plants set seed, Table 2,3.
15Table 2. Fertilizer effects on Nassella pulchra survival at 45 months Treatment Plant protector No plant protectorControlCottonseed mealZincOrganic fertilizer mix
16Table 3. Fertilizer and plant protector effects on seed set after 45 months Treatment Plant protector No plant protectorControl Cottonseed meal Zinc Organic fertilizer mix This demonstrates the importance of long term tests. Initial results suggest fertilizer is helpful, but as drought stress developed the larger plants suffered more. Over the long term, at least at this site and with this rainfall pattern, no fertilizer may be the best strategy.
17Test 5. Soil amendment, fertilizer, surface configuration Abandoned farmland, overgrazed canyon bottomlandSite-collected Nasella pulchra seed was grown in 2 x 2 x 6 inch plant bands and planted in two blocks, an Erodium dominated site (drier and more infertile) and a wild oats (Avena fatua) and bermuda grass dominated site, moister and more fertileSites were cleared by mowing and raking and received treatment combinations of fertilizer (organic 8:5:1, synthetic 5:3:1, or control), mulch (3-4 inches of sawdust, compost or control), tillage (no-till or rototilled before or after amendment) and pitting.In winter 2002, 712 grasses were hand planted, with each getting a plastic plant protector. They were hand watered several times during the spring and summer of 2002.Survival was monitored and seed set was observed in spring Weed weights from a subset of plots were measured in spring 2003.
18Overall survival was over 70 percent and almost all set seed, with an average of 14 tillers and 25 seeds per tiller from a small random subsample. This added almost 200,000 seeds to the site.Sawdust appeared to improve survival slightly, with the best survival in sawdust treated plots, worst in mulch.Soil pitting/no pitting and tillage/no tillage had no significant effect on survival, perhaps due to the unusual rainfall pattern.The three best treatments were: control/no till, sawdust/no till, and sawdust/till before amendment.Survival was better on the eastern, less fertile plot.Rainfall in stimulated weed growth and they completely dominated the more fertile western plot. Weed weights early in the season were significantly different for the subset of treatments sampled. These were chosen to represent the most likely treatment combinations, and the visually biggest differences.
19Table 4. Weed weight by treatment Tons/acresawdust/no tillage 1.2sawdust/tillage after 1.6sawdust/tillage before 3.1control/no tillage 3.3mulch/tillage before 8.1mulch/tillage after 22.5
20Test 6. Mechanical Transplanting Trial Former farmland, overgrazed, used for military activitiesCompare hand planting with 3 mechanical transplanting methods in terms of survival, efficiency and cost.5 acre trial as part of a 28 acre project on Camp Pendleton Marine Corps Base. Gradual slopes, good access, soil from sandy loam-clay loam, very high initial level of exotics, gophers and herbivores.Site burned summer 2002, sprayed to reduce resprouting rhizomatous exotics.Site preparation in fall double deep ripping to 24” and mulch incorporation at rate of 269 cu yds/acre ( equivalent to 2” layer).Nassella pulchra seedlings from local seed source grown in 5 cu. inch plastic containers and planted at a planned rate of 3000 per acre in spring Each seedling received a seedling protector.Survival data - 100% survey in Sept 2003
21Treatments Hand Planting Mechanically-assisted Planting Use equipment to open a channel and hand plant into channelSingle Row Basic TransplanterTowed by tractor with treads; person rides the transplanter unitOpens a channelSeedling dropped by hand into the channelPacks soil back around seedling to close channelDouble Row Commercial TransplanterDouble row Holland transplanter units with deep channel opener, planting fingers, watering attachment, channel closer and firmer.Towed by 4-wheel drive tractor; a person rides each transplanter unit, setting plants in finger units
23Results after 6 monthsMethod Avg. Survival Planting Rate/Hr* Comp. Cost**Hand Planting % %Mechanically % %Assisted PlantingSingle Row % %TransplanterDouble Row % %* Includes moving ofplants and supplies, extracting grass plugs,any correction of planting depth, watering, installation of plant protectors.** Transplanters were owned, no rental cost.
24Lessons LearnedMechanical transplanting was faster and cost less than hand planting with comparable survival thus far.Modification of the transplanter hitch/mount may be needed for proper function.Transplanting success is soil moisture dependent; too moist or too dry and the channels are either not opened or are too shallow and don’t close properly.If the soil surface is too rough, the transplanters don’t operate well. The channel won’t stay at the correct depth, and on the double row transplanter the mechanism that delivers the seedlings and waters them will not function properly.
25Transplanter performance was best on flat or gentle slopes Transplanter performance was best on flat or gentle slopes. Success on sidehill and steeper slopes was poorTransplanters operated faster than the field crew could keep up for planting depth fixes, watering, and installation of plant protectors.
26Recommendations Future Trials Best on flat or gentle rolling sites with good access, soil without rocksPlanting laid out to minimize side-hill slopePrior soil cultivation to prepare and smooth surfaceTransplant when soil moisture is appropriate (not to dry or moist)Sufficient acreage to use tractor and operator in full day incrementsLarge enough field crew for timely correction of planting depth, watering and installation of seedling protectors.Future TrialsCultivation prior to transplantingWeed reduction before planting, pre-emergents, solarization, repeated tillage/irrigation/tillageSub-irrigation with drip to reduce weed problems
273. Discussion and conclusions A. Container planting works wellThese experiments confirmed the value of transplanting grass seedlings.Survival was usually 90%+ for the first year and many plants produced seed the first year.Transplanting can be done by hand, with cut slots (mechanically assisted), or on flat or gentle rolling sites by mechanical transplanters.Mechanical transplanting can dramatically increase planting rates and reduce planting costs.
28B. Plant protectors are desirable It appears that herbivory by rabbits was limiting growth and seed set. Perhaps one of the benefits of fire is reduced herbivory.Benefits may also reflect the improved microenvironment in the solid wall plant protectors, giving the grass a competitive edge against the exotic annuals. By increasing temperatures earlier in the season, the needlegrass may start growing much earlier, allowing its more vigorous roots to outcompete Bromus, Avena, Erodium and other weedsWithout plant protectors root growth in purple needlegrass usually begins weeks or months after the exotics.Plant protectors also make it easier to weed, spray, monitor and protect plants.
29C. Fertilizer is problematic The addition of nutrients and/or organic matter entails risk of increased herbivory, weeds, and increased drought vulnerability.The addition of nutrients and/or organic matter significantly increased early seed production, but the higher fertility appears to have increased mortality during the serious drought. It is a tradeoff of risks, more seed versus vulnerability to drought.Initial growth and condition were better with fertilizer, but during these dry years control plants gradually became healthier, larger, and survived better.If fertilizers are added to increase growth and seed set then long term irrigation may be needed on dry sites.
30How fertile is too fertile? The experiments provided some insight into fertility requirements.Grasses grew well at the east canyon plot with mean nitrate N of only 1.3 ppm, NaCO3 extractable phosphorus 5.7 ppm, and organic matter 1.6%.The added sawdust would be expected to tie up additional N, yet these low fertility soils posed no apparent problems for the native grasses.This explains why little effect from added fertilizer was shown on early sites with 5 ppm nitrate nitrogen, 6 ppm NaCO3 extractable phosphorus, and 1.8% organic matter,The wild oat dominated site with high fertility, (N 19.3 ppm, NaCO3 P 11.7 ppm, and 4.7% organic matter) was plagued with weeds
31D. Clearing plots and limiting competition helps but is not sufficient Nassella pulchra in scraped low density plots grow larger than grasses in high density plots. Increased planting density increased percent cover; but cover averaged only 35% in the high density plots after nine months, leaving considerable soil area open for weed invasion.In the canyon site the three best treatment combinations were: control/no till, sawdust/no till, and sawdust/till before. Sawdust appeared to improve survival, with the best survival in sawdust treated plots, worst in mulch.Improvement with sawdust may reflect improved moisture capture and storage, reduced fertility (limiting weed competition), improved temperatures, and reduced soil strength, facilitating root extension.
32Weed control strategies Weed problems were severe on three sites. Effective weed control is desirable but difficultEarly in the season the sawdust/no till plots in the canyon had only 5% of the weeds of the mulch/till after plots. The higher fertility western site was inundated with weeds, primarily Avena (wild oats) which were chest high.Scraping to bare soil was helpful, but open soil was quickly colonized.Weed control mat or heavy kraft paper might helpBurning before planting was helpful but not sufficientMore effective weed suppression might involve soil solarization, repeated chemical treatment, or repeated irrigation and mowing with minimal herbicide useWeed control would be most effective if started the year before planting.Weed management after planting is desirable
335. Conclusions and recommendations Planting native grasses from containers is very effective. A rate of 3,000/acre gives acceptable cover at reasonable costMechanical transplanters provided much faster planting and reduced cost compared to hand planting, with comparable survival. If transplanters are not available, planting into a ripped slot (mechanically-assisted planting) improved speed and reduced cost.
34Weed management before planting is very desirable. Survival can be improved by using solid wall plant protectors. Plant protectors may also be used to improve seed production, especially if only a small group of surviving grasses will be the seed source for restoration.Supplemental irrigation will be needed in most years. Perhaps buried drip irrigation (not tested here) could be successful for maintaining grasses without stimulating weeds.Nutrient management to reduce site fertility appears to offer some possibility of improving long term survival.