Revegetation Research Effort at Fort Hood, Texas

Compost Effects on Emergence and Seedling Survival of Prairie Species

Ft Hood, TX troop training activities causes severe land disturbance, loss of vegetative cover and soil erosion (Figures 1 and 2). Studies have been initiated to identify best management practices (BMP) to reduce the impacts of training exercises. Some of these include sediment traps (modified stock ponds), dedicated roadways (for track vehicle use), and revegetation.

   Figure 1.                                                            Figure 2. 

 Revegetation efforts include reseeding with native and introduced grasses and forbs, and identification of species which can be used as vegetative hedges for erosion and runoff control. The Fort Hood area is located on the northern edge of the Edwards Plateau and west of the Balcones Escarpment. Plant communities there are characterized as midgrass prairie, riparian and canyon systems. Successful revegetation is heavily dependent on soil conditions, especially soil moisture during germination, emergence and the seedling stage. 

Composted organic soil amendments have been shown to improve soil properties and plant growth in horticultural, agronomic and wildlands studies.  Because organic amendments typically improve the soil water holding capacity, and increase the available water, they potentially could improve the success of seeding efforts.

Most studies have quantified plant response to compost amendments with measurement of mature plant characteristics.  This study examines the effect of compost amendment on seedling emergence and survival through the seedling stage, which is critical to the success of revegetation efforts.  Although recommended for use in revegetation efforts, the effects of compost application rate on seedling emergence and survival is unknown, for Central Texas. 

Objectives:

1) Quantify and compare the effects of low application rates of compost on emergence and seedling survival of 6 native prairie species on Fort Hood soil types. 

2) Quantify and compare the effects of low compost application rates on establishment of tallgrass prairie species.

3) Quantify and compare the short-term effects of low compost application rates on soil properties. 

Materials:                                                                                                                       

Study Site:

The research site is located on the reservation about 10 km northwest of the cantonment area (31W10; 97N50).  The soil (BtC2) – Brackett Topsey Association consists of deep, loamy soils on undulating uplands, 3-8% slope.  Erosion has removed much of the surface layer (Figure 3).  Brackett soils make up 40-60% of the association and are on the tops of knolls and low hills.  Topsey soils make up 30-45% of the association and are found lower down in the landscape.  Both soils are well drained, permeability is moderately slow, and available water capacity is medium. This site was installed on soils that had been removed and stored during construction of a sediment trap (Figure 4) and then spread on the disturbed upslope area. Blocks were laid out parallel to the slope contour and rototilled to smooth the surface. Large rocks (>10 cm diameter) were removed.

                        Figure 3.                                                    Figure 4.

Species:

Native prairie species commonly used in reseeding efforts and readily available through commercial outlets were selected.  Six plant species, 5 grasses and 1 forb, were seeded in the subplots. 

Composted organic waste:

Compost produced by the waste facility on Ft Hood TX was used.  This compost is derived primarily from wood wastes.  It was shredded, windrowed and turned weekly.  No additional nitrogen was added to facilitate the composting process.  Once the internal temperature cooled, the composting process was deemed complete and the pile was stored on site.  Composting via this process typically takes 6 months to 1 year.  The compost used in this study was more than 1 year old.

Methods:                                                                                                                           

Experimental Design: 

The plots were arranged in a split block design with 5 levels of compost, and a surface application of compost, assigned to the main plots. Each block was replicated 3 times at each site and contained 6 plots. Each plot was 3mX3m.  Compost was applied at 5 rates (0, 1.25, 5, 10, and 20 tons/ac) and incorporated to 10 cm.  One plot had a surface application of compost at 10 tons/ac. 

Seeding:

The plots were seeded by hand to a depth of 3 to 5 mm in rows that were 0.3 m apart.  The Fort hood site was seeded between 28 May and 1 June, 1999.  Rainfall events  rendered  irrigation unnecessary.

Data Collection:

Plots were visually observed for emergence 7 days following seeding and at 7-day intervals thereafter until emergence was noted. The week following the first emergence, a 1-m, linear quadrat in all the rows of that species in all plots at that site were counted and mapped.  Within each plot, a benchmark was located 0.3 m from one end and the total number of emerged seedlings within 1 m of the benchmark were counted.  Up to 35 seedlings were mapped along the 1-m quadrat.  Each seedling’s position along the linear 1-m quadrat, and height was noted.  The total number of live and dead seedlings within the 1-m quadrat was counted weekly.  Each mapped seedling was tracked at weekly intervals for 3 total counts at which point they were at least 21 days old (see figures 5 and 6).  The seedlings were then assumed to have survived the seedling stage and to have entered the next developmental stage. Newly emerged seedlings were noted at each weekly count and tracked for 3 counts, also.  These counts and mappings were continued on a weekly basis until mid-July.  At this point, few emerging seedlings were noted and the experiment was terminated.  A final count for survival and establishment over the summer was conducted between 1 September and 10 September 1999.  Results will be statistically compared.

                           Figure 5.                                            Figure 6.

Soil samples were obtained prior to compost additions.  Gravimetric soil moisture was determined for each plot at each weekly count.   Soil properties that will be quantified were initial nutrient level, chemical characteristics, organic matter content, moisture content, and bulk density.  These properties will be quantified again at the final emergence count.  Soil moisture content and bulk density, measured gravimetrically, will be quantified at each emergence count. Nutrient and organic matter content will be measured with standard soil sampling techniques.

Expected Results:

-         Comparison of seedling emergence on soils without compost and with several rates of compost amendment

-         Comparison of seedling survival on soils without compost and with several rates of compost amendment.

-         Recommendation for compost amendment rate for optimum seedling emergence and survival.

-        Comparison of compost amendment rates based on compost nutrient level and crop requirements vs requirement for seedling emergence and survival and soil physico-chemical properties.

Note: This study reflects an effort by Mr. Ralph Hicks, a Research Associate with the TAES/BRC Water Science Laboratory - Fort Hood Project.  The results will be utilized to generate recommendations for the Fort Hood land management staffs revegetation program.  Mr. Hicks will also use the data to complete part of a Ph.D. dissertation from Texas A&M University.