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Patuxent Wildlife Research Center

11410 American Holly Drive

Laurel, MD 20708, USA

301-497-5622 (Tel)

301-497-5624 (Fax) 

LEAFGRO and COMPRO Piles before speading




Increased interest in wildlife biodiversity and the restoration of wildlife habitats and populations, makes it appropriate to study habitat enhancement techniques at Patuxent Research Refuge (Patuxent). Several areas of Patuxent have been degraded by human activities and provide excellent study sites. The primary objective of this study is to compare two compost materials (COMPRO and LEAFGRO) to enhance wildlife habitats. COMPRO is a composted mixture of sewage sludge and wood chips and LEAFGRO is a composted mixture of leaves and grass clippings. A secondary objective is to determine optimal techniques to apply compost materials to large wildlife habitat areas (e.g., powerline rights-of-way) to improve soil quality that will result in improved plant and invertebrate biodiversity.

This study is being conducted at two sites (Range 20 and Shaefer Farm) that were degraded by previous military and farming operations. Two 50 x 100 meter sections of each site were plowed and disked in April and again in May 1996. The blocks were gridded into 8, 25 x 25 meter square plots (0.06 hectares) using PVC stakes in each corner. The two soil treatments and two types of controls were randomly assigned to the 8 plots and replicated two times. The COMPRO and LEAFGRO were applied with a modified manure spreader and disked into the soil to a depth of 3 inches. Control plots received no amendments and were of two types: one that was planted with a warm season grass mixture and one that was not planted. Plots receiving compost were also planted with a warm season grass mixture. Five separate tests conducted to determine if weed seeds existed in the compost material revealed no germination of plants.


Three randomly selected meter-square quadrats were established in each treatment and control plot and permanently marked with a PVC stake. Sampling of the quadrats was conducted in October when most grasses and other open-field plants had reached their maximum growth for the year. All plants were identified by species and percent cover was estimated for each quadrat.

Sampling for invertebrates was conducted four days each month with the use of a five-gallon bucket (pitfall trap) placed in the soil in the middle of each plot level with ground surface. Invertebrates were also sampled by sweeping the vegetation with capture nets during August 1997. In addition, earthworms were sampled from each plot in August 1997. All invertebrates were identified and counted.

Pitfall traps also were used to capture small mammals, amphibians, and reptiles that use the areas. Trapping for small mammals with Sherman live traps placed in each plot was conducted during the four-day period that pitfall trapping was conducted.


 LEAFGRO and COMPRO Piles before speading

Photo 1: LEAFGRO (foreground) and COMPRO before spreading. 


Farm Equipment for Spreading

Photo 2: Farm equipment for spreading compost.

Plots being disked and seeded      

Photo 3: Plots being disked and then seeded.     


Study Site showing plant response to treatments

Photo 4: Study site showing plant response to treatments. 

Conducting vegetation survey     

Photo 5: Conducting vegetation survey. 

Sampling invertebrates in pitfall trap

Photo 6: Sampling invertebrates in pitfall trap.


In late October of 1996-99 vegetation sampling was conducted in three randomly selected meter-square quadrats in each plot. Initially, the greatest vegetation cover occurred in plots treated with LEAFGRO. Plots treated with COMPRO had less vegetation cover than both types of control plots. The reduced vegetation cover in plots treated with COMPRO could be related to the much higher pH of these plots on both sites. After four years, however, the percent cover in the compost plots were not different from each other or from the planted controls.

Table 1
Ground Cover by Planted and Volunteer Species 
at Study Sites


  COMPRO LEAFGRO Control Planted Control Unplanted
Range 20        
Planted Species  16 12
Volunteer Species  81 89  73 98 
No Cover  3 15 
Shaefer Farm        
Planted Species 19 18 20 0
Volunteer Species 61 77 54 88
No Cover 20 5 26 12

Initial invertebrate sampling in 1996 indicated that there were more invertebrates in the LEAFGRO plots. Increased invertebrates appeared to be directly related to the increased vegetative cover in the LEAFGRO plots. However, when data from 1996 and 1997 were combined (Table 2), there were no major differences in invertebrate abundance among the plots. A total of 4775 invertebrates were recorded from 1996 and 1997 (1288 in COMPRO, 1197 in LEAFGRO, 1122 in Control / Planted, and 1168 in Control / Unplanted).

Table 2

Macroinvertebrates Trapped at Study Sites                                                   
SPECIES COMPRO LEAFGRO Control Planted Control Unplanted
Ant 46 18 20 32
Beetle 449 380 489 410
Caterpillar 20 29 11 20
Cricket 357 344 198 273
Grasshopper 47 26 33 33
Millipede 28 30 20 11
Slug 17 88 63 61
Spider 246 219 254 267
Others 78 63 34 61
TOTAL 1288 1197 1122 1168

Although no mammals were captured in Sherman Live Traps in 1996, a total of 60 small mammals of five species was captured in 1997. A total of 21 mammals was caught in the COMPRO plots, 27 in the LEAFGRO plots, 11 in the Control Planted plots and 1 in the Control Unplanted plots. The meadow vole (Microtus pennsylvanicus) was the most commonly caught species with 12 in the COMPRO plots, 10 in the LEAFGRO plots, 3 in the Control Planted plots and 0 in the Control Unplanted plots. Amphibians, reptiles, and birds using the sites were surveyed but no differences due to treatment could be detected in their species or numbers.


Numerous areas in the United States have been degraded by human activities and possibly could benefit initially from soil enhancement with compost amendments. Results from this study, however, indicate that plants and invertebrates did not benefit from compost, and only small mammals appeared to respond positively to the soil amendments. Larger quantities of compost may be necessary to show more significant changes in the flora and fauna of these habitats.

Partners on this study include the Environmental Protection Agency, Quail Unlimited, Maryland Department of Natural Resources and Patuxent Research Refuge (USFWS).

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