Final Report for GNC04-028
Project Information
The use of integrated cropping systems to promote a more profitable and ecological agriculture is of interest to many farmers today. To test the hypothesis that the restoration of ecosystem functions to crop lands will allow farms to maintain productivity while improving land health, plots integrating pastured poultry and vegetable production were constructed. Vegetables were produced in raised beds built in the middle of pasture plots of differing diversity and grazing intensity. Chickens housed in bottomless shelters were rotationally grazed around the vegetable beds in each pasture. A control with vegetables surrounded by a clean cultivated, ungrazed ‘pasture’ area was included in the treatments. The effects of pasture composition and poultry grazing on pasture, vegetable, and poultry productivity and profitability, invertebrate populations, and soil nutrients were examined.
Dressed weight of poultry was not affected by pasture type (p=0.60). Vegetable yields were affected by pasture type and grazing, but varied by crop. Pasture productivity, quality, and composition were affected by the grazing as well as the initial species composition. Diverse pastures were more resistant to weed invasion (< 2% of biomass), and the grazed mix yielded more forage biomass during peak production seasons than the ungrazed mix or monoculture pastures (p<0.05). Fall harvested forage from the grazed mix had highest levels of crude protein (23%), phosphorus (0.4%) and potassium (3.2%). Squash bug egg abundance was reduced in gardens surrounded by grazed compared to ungrazed pastures (p=0.038). Abundances of spiders, carabid beetles, and collembolans were higher in grazed pastures throughout most of the field season, and parasitic hymenopterans were most abundant within the garden areas surrounded by the grazed diverse pastures. The diverse pasture soil surface showed greatest abundance of worm casts (~1000/m2), indicating greater numbers or activity of these soil builders. Soil microbial biomass and N and C mineralization potentials were not influenced by the treatments. Pasture soil content of P, K, and total N, were increased by grazing and all pasture-based systems showed higher levels of total C than the tilled system. Additionally, the grazed systems improved overall profitability by offering an additional income stream and reducing production costs compared to the tilled system. These results indicate that a system integrating rotational poultry grazing and annual vegetable production offers farmers a viable and flexible method for addressing both agronomic and environmental concerns.
Introduction:
Contemporary thinking in alternative agriculture is bringing into question the very nature of farming itself. The problems within agriculture such as pests, yield fluctuations, and diseases are considered secondary to the problem of agriculture; the thesis being that we are sustained by a fundamentally flawed model of food production (Jackson, 1980). The industrial model of agricultural production is problematic in that it displaces farmers on a massive scale, erodes the very materials which sustain it, consumes material input en masse, is wholly dependent upon finite resources and, lastly, engenders a treadmill of problems, solutions, and then problems with the solutions such as pesticide resistance or the inverse relationship between yield and commodity profitability.
In considering an alternative approach, this study aims to develop and examine an agricultural system that is: 1) productive and economical, and 2) possesses ecologically restorative properties. Such a system could enhance the momentum of new agrarianism, revitalize dilapidated farmsteads, and mitigate perceived profit losses on farm property being devoted to conservation initiatives. The goal is to understand how people may “assemble synthetic communities of plants, animals, and microorganisms that are stable, productive, and close enough in form to the native community that the essential functions of pest resistance, soil stability, and nutrient cycling are preserved (Anonymous, 2005).” To do so, this project assembled communities consisting of vegetable crops planted in raised beds surrounded by a border area that were then grazed by broiler chickens (Gallus gallus) in a rotational system.
- To test the hypothesis that ecologically functional agricultural systems can enhance land health while sustaining agricultural productivity, this research addressed the following objectives:
To evaluate how pasture diversity and grazing affects forage, poultry, and vegetable productivity.To determine whether increased pasture diversity combined with poultry grazing helps reduce insect pest populations and weed invasion.
To measure how this integrated system influenced soil nutrient content.
To quantify the economic capacity of these systems.
Cooperators
Research
Experimental Design
The experimental design is a 2 x 2 factorial arrangement of a randomized complete block, plus a control. The experimental unit was replicated three times and the treatments were randomized within each replicate (Figure 2). The treatments were:
GRZ-ALF Vegetable production and poultry pastured on an alfalfa monoculture.
GRZ-MIX Vegetable production and poultry pastured on a diverse forage mix.
UGR-ALF Vegetable production and an ungrazed monoculture pasture.
UGR-MIX Vegetable production and an ungrazed diverse pasture.
CTRL Vegetable production and an ungrazed, clean cultivated border.
The plots were established at the University of Illinois Cruse Vegetable Crop Research Farm in Champaign, Illinois. The research area was on Flanagan silt loam (fine, montimorrillontic, mesic, Aquic Argiudoll) and had been under cover of organically managed 18-month-old alfalfa. Each plot was 5.16 m x 9.8 m. The entire research area encompassed approximately 0.13 hectares. The research area was surrounded by an electrified net type fence supplied by Premier 1 Fencing Co. (Washington, Iowa) to deter predators. The fence was charged by a 9-volt fencer also supplied by Premier 1. The pathways between the plots were maintained by regular mowing. The fence line was maintained by first tilling in the existing vegetation along the projected fence line and then maintaining its margins with regular mowing and the use of a hoe to keep the fence line weed free. This maintenance was necessary to keep plant material from shorting out the fence.
Statistical analyses were done with SAS statistical software. ANOVA analyses were done using Proc GLM and Fishers LSD, α=0.05. In addition, tests for the significance of the main effects or interactions were done with linear contrasts. In the event of significant interactions within the treatment term, the difference of least squares mean (p<0.05) was used to separate treatment means. Repeated measures analyses were done with Proc Mixed in SAS. Significant results were further analyzed with linear contrasts. An autoregressive heterogeneous variance/covariance matrix (ARH1) was used as the variance/covariance matrix for all repeated measures analyses. This matrix produced the lowest Bayesian fit statistic for almost all analyses and best matched the heterogenous variances found over time within the data. This type of variation is typical of biological data, particularly of sampling taken within a growing season as both sample sizes (e.g. plant biomass) and sample variances will be small at the beginning of the season, increase as growth peaks, and then reduce again towards fall. Poultry Production The chickens selected for this experiment were Kosher Kings bred by Noll’s Hatchery (Kleinfeltersville, Pennsylvania). Two cycles of brooding, grazing, and processing were completed in 2003 and three cycles were completed in 2004. Each cycle had 60 chickens. In 2003 chicks were hatched and shipped to Urbana on May 12 and June 23. Processing dates in 2003 were on July 15 and August 25 respectively. In 2004 chicks were hatched and shipped on March 30, May 18, and July 27 and were processed on June 2, July 29, and October 9. The birds arrived via airmail as three-day-old chicks. They were placed in a 1.3 m x 3.3 m x 0.6 m brooder unit constructed from plywood. The bedding within the brooder was commercially available kiln dried wood shavings or straw. Bedding was added regularly to ensure cleanliness. The brooder was housed in a draft-free and predator-proof outbuilding and was heated by an electric air heater and suspended brooder lamps. The electric heater was removed after the chicks were ten days old. Water was supplied by multiple, 4 liter gravity waterers. Water was monitored several times daily to ensure that it did not run out and that it remained clean. Feed was a custom ration mixed by a local feed mill according to the recommendations of Pastured Poultry Profits by Joel Salatin (1993). Feed was offered free choice to the chicks, and then on a twice daily basis from three weeks of age until processing. The chickens were brooded indoors for approximately four weeks and then pastured for approximately six weeks before processing. In the field, the chickens were housed in 1.3 m x 1.6 m x 0.6 m portable, bottomless pens with ten chickens per pen. Every morning the pens were moved to the adjacent paddock within their pastures. There were 22 grazing paddocks in each pasture and each paddock received 21 days of rest between grazing. While on pasture the chickens were fed their grain ration, and their water was checked daily. Processing was done by hand according to the process outlined by Salatin (1993). They were then bagged and sealed and frozen. Market value was calculated by multiplying dressed weight by a market rate established through consultation with project’s farmer advisory committee and was based on their prices for retail sales of pastured poultry. Grain efficiency for each year was computed by dividing total grain consumption by total dressed weight. This value is expressed as a ratio of grain to dressed yield. Proc GLM in SAS was used to determine the significance of the differences in dressed weight due to treatment. Additionally, regular sub-samples of chicken live weights were taken during the pasturing stage of the second cycle of 2004 to determine the development rate of the chickens. On June 18, June 28, July 2, July 8, July 13, July 19, and July 29, 2004, five chickens per pen were randomly selected and weighed as a group in the field, and then returned to their pen. The birds were weighed with a Pelouze plate scale and were contained in a plastic crate, the tare of which had been accounted for on the scale before the chickens were added. Weights were taken in ¼ lb increments and then converted to metric units. Total weight for each treatment/replicate combination was recorded and mean weight per bird was calculated by dividing total live weight at each date by the number of birds weighed on that date (n=30). Growth rate was calculated using linear regression in Proc GLM. Vegetable Production Production of vegetables was carried out in raised beds located in the pastures. These beds were built in mid May of 2003. The beds were made by tilling in the existing pasture cover and then subsoiling the bed area with spading forks. The spading but not the tilling was repeated in 2004. In 2003 crops were Roma paste tomato (Lycopersicum esculentum) from Seeds of Change (Santa Fe, New Mexico), Yellow Crookneck squash (Cucurbita pepo) from Seed Savers Exchange (Decora, Iowa), and Jacobs Cattle dry bean (Phaseolus vulgaris) from Johnny’s Selected Seeds (Albion, Maine). In 2004, Cal Wonder bell pepper (Capsicum annum) from Seeds of Change, organic shallot (Allium cepa) sets from supermarket stock, and Bollero carrot (Dacus carrota) from Johnny’s Selected Seeds replaced the tomatoes and dry beans as crop rotations to maintain organic production relevance, and to test for variation by crop type. The yellow crookneck squash was planted in both years to test for yield consistency within one crop over both years and to investigate the response of squash pests to the treatments. Squash were started from seed in a greenhouse in 6 cm x 6 cm peat pots with a sterile peat and perlite potting media. Tomatoes and peppers were started from seed in a greenhouse in 4cm x 4 cm cell plastic flats using sterile peat and perlite potting mix. Seedlings were watered regularly and fertilized once using liquid fish emulsion at the rate of 5 ml per liter. Seedlings were hardened off and transplanted at approximately 4 weeks after germination. Transplanting was done manually date in late May 2003 and in the first week of June 2004. Beans were direct-seeded in mid May 2003. Shallots were planted from sets in 2004 in early June. Carrots were seeded directly in early September 2004. Squash, tomatoes, and peppers were all planted with 36 cm spacing and off-set centers. Each bed held six plants of each species. Beans were seeded at 4 cm in row and between row spacing. Approximately 420 beans were planted in each bed. Shallots were planted with 10 cm in row and 8 cm between row offset center spacing. Approximately 25 shallot sets were planted in each bed in 2004. Carrots were seeded thickly in short rows that spanned the width of the bed. Rows were spaced 8 cm apart, each bed had 5 short rows of carrot seed totaling 6.6 m of seed row. Carrot seedlings were thinned to stand 3 cm apart in rows when plants were approximately 6 cm tall. Transplants were watered only after transplanting to ensure establishment. Beds were weeded manually approximately once per week. Vegetables were harvested when subjectively determined to be of marketable size and condition. Squash were harvested approximately every three days between July 31 and September 12, 2003 and between July 23 and September 6, 2004. Tomatoes were harvested between August 26 and September 20, 2003. Peppers were harvested on August 5, 2004. Dry beans plants were allowed to senesce and pods fully dry in the field. Seed was then manually harvested, threshed, and sorted for quality. Bean pods were harvested on October 15, 2003 and processed on December 22, 2003. Only edible beans were considered in calculating yield for the crop. Shallots were harvested on August 23, 2004 and allowed to cure for two weeks in a greenhouse. After their tops were trimmed, they were weighed on September 7, 2004. Carrots were harvested on November 8, 2004 washed, trimmed and weighed fresh. Weights were taken using a digital scale and recorded in grams. Proc GLM and Fisher’s LSD were used to test for and separate significant differences in vegetable yield due to treatment. Forage Production The diverse pastures were established on April 4, 2003. The monoculture pasture was the preexisting 18 month old alfalfa. The diverse pasture was a mix of white clover (Trifolium repens), perennial ryegrass (Lolium perenne), tall fescue (Festuca arundinacea), birdsfoot trefoil (Lotus corniculatus), forage turnip (Brassica rapa) and forage rape (Brassica napus) and forage chicory (Chicorium intybus). Seed was obtained from Byron Seeds (Marshall, IN.) This pasture was established by tilling in the existing cover and then broadcast seeding and raking in the mix and firming the soil with a roller. Forage productivity was measured from biomass samples taken June 12 through September 20, 2003, and from May 6 to September 22, 2004. Samples were taken approximately every two weeks in 2003 from the paddock scheduled to be grazed the following day. This initial method of sampling bi-weekly was replaced in 2004 by repeatedly sampling two specific paddocks in order to better assess biomass production in terms of regrowth. Samples were taken consistently from paddocks # 7 and # 19 in 2004 after they had received a full rotation of rest and were about to be grazed or mowed. Samples were cut 5 cm from the soil surface from within a round quadrat placed just off center and against the southern edge of the sample paddock. Only plants rooted within the quadrat area were cut. Quadrat size was 0.10 m2. Samples were sorted by species, dried for 48 hours at 60◦ C and weighed. Primary productivity was calculated in g/m2 and represented total plant biomass regrowth between grazing dates. Percent importance values for each species were calculated by dividing species weight by total weight at each sample date. Biomass data were analyzed with repeated measures analysis. Additionally, samples were analyzed for forage quality to test for crude protein, relative feed value, % P, and % K. Biomass samples from the sampling dates of June 6 and September 6, 2003, and May 18, July 8, and September 22, 2004, were recombined after drying and weighing and used for the forage quality analyses. Forage quality analyses were done by NIRS at Alvey Lab in Belleville, Illinois. Data were analyzed with Proc GLM and Fisher’s LSD. In 2003, the ungrazed pastures grew unchecked throughout the growing season. This does not reflect an accurate agronomic use of a pasture. In 2004, these pastures were mowed and their biomass removed three times throughout the season to reflect a hay harvest. Forage quality and biomass results from 2004 only are presented. Invertebrate Surveys Arthropod surveys used pitfall traps in both 2003 and 2004. Collection occurred on June 26, July11, July 21, August 8, and August 22, 2003; and May 26, June15, July 7, July 22 and August 4, 2004. Each plot had five, 15 cm diameter traps. Traps were made from plastic bowls with a 600 ml capacity and lids were cut from linoleum tile. The lids were mounted on galvanized nails sunk into the soil outside of the trap. The lids were mounted 2.5 cm above the soil surface. Traps were set in paddocks #1, #7, and #19 (Figure 3) so as to trap from each region of the plot. Two traps were set within the vegetable beds, each one meter in from either end of the bed. Traps were loaded with a soap and water solution. The trapping period was 24 hours. At the end of the trapping period samples were collected, drained, rinsed and preserved with 70% ethyl alcohol in 120 ml plastic jars. Spiders (Aranae) were identified to order. Coleopterans in pitfall traps were identified at least to family and included carabid beetles (Carabidea) and tiger beetles (Cincidelidae). Striped cucumber beetle (Acalymma vittatum.), and corn rootworm beetle (Diabrotica sp.) were identified to species and genus respectively. Collembolans (Collembola) were identified to order. In addition, centipedes (Chilopoda) simple flies (Diptera: Mycetophilodea), grasshoppers (Orthoptera: Acrididae), squash bugs (Anasa tristis) lygus bugs (Lygus sp.) and Hymenoptera were counted from pitfall samples. Pitfall data from only the spiders, carabids, and collembolans is presented because counts of the other subject invertebrates were too low or erratic for analysis or were considered to be of secondary interest. Data from spiders, carabids, and Collembola were analyzed with repeated measures analysis. Pitfall trap data of spider abundance from 2003 were log transformed, and data from 2004 were square root transformed. Pitfall trap data of Collembola abundance from 2003 were log transformed. Collembola abundance data from 2004 and carabid beetle data from both years was normally distributed. Normality was established by analyzing and plotting the residuals. The unsorted portion of each sample was returned to its original storage vial. Vacuum samples of the plots were taken in 2003 using a gas powered yard blower operating in reverse with a very fine mesh bag mounted over the intake to allow for collection of specimens. Three vacuum samples were taken from each plot. Two samples were collected from randomly selected paddocks within the pastures, and one sample was taken from each vegetable bed. The pasture vacuum sample was a 1.3 m x 1.6 m area (one paddock) vacuumed for one minute. The garden sample was a 0.6 x 3.3 m area vacuumed for 1 minute. At the end of the sampling duration the mesh catch bag was inverted, and its contents emptied into a gallon size plastic bag. Samples were then labeled in the field and after sampling, stored in a freezer. Sampling was done between 9 am and noon on July 11, July 24, August 5 and August 22, 2003. Vacuum sample data presented are from the garden beds only. Samples taken from the pasture areas contained too much fine plant debris to allow for efficient processing and sorting. Samples from the garden beds were used to examine the populations of parasitic Hymenoptera, as well as cucumber beetle, and corn rootworm beetle. Hymenoptera were identified to family (Braconidae, Ichneumonidae, or Chalcidae) in order to group them as parasitic hymenoptera. Identification was based upon body size and shape, wing shape and appearance, and ovipositor appearance (Borror and DeLong, 1971). Target samples were counted and preserved with 70% ethyl alcohol in labeled glass scintillation vials. Data were analyzed with repeated measures analysis. Hymenoptera data were normally distributed. Corn rootworm beetle data was square root transformed. Cucumber beetle data was not analyzed because abundance was so low. Normality was established by analyzing and plotting the residuals. Visual counts of squash bug (Anasa tristis) eggs on the crookneck squash plants were conducted on July 22 and August 3, 2004. Counts were taken by examining the upper and lower surface and the petiole of each leaf on every squash plant in each bed. When eggmasses were found on the squash plants, the number of eggs in that mass were counted and recorded. These data were square root transformed and analyzed with repeated measure analysis. Visual counts of earthworm (Lumbricidae) casts were made on August 5, 2004. Counts were made within 48 hours of a rain event with the assumption that the rain washed away all previous casts, and that the count was a measure of activity within the previous 48 hours. All casts within a round, 0.1 m2 quadrat, placed in the center of a randomly selected paddock were counted. Mean count was calculated for each treatment, and density of casts was calculated as a mean per m2. Proc GLM and Fisher’s LSD were used to test for and separate significant differences due to treatment. Soil Fertility and Nutrients Soil samples were collected in November 21, 2003 and October 15, 2004. Samples were collected to a depth of 10 cm using a 2 cm diameter soil probe. Pasture soil samples were taken from three randomly selected paddocks, and two samples were taken from each garden bed. Garden bed samples were taken from the center of the bed, approximately 1 m in from each end. Samples were bulked by location within the plot (pasture or garden), crumbled by hand and oven dried for 48 hours at 50◦ C, and then hand ground to a fine consistency in 2003 and to approximately 2mm (No. 10 mesh sieve) in 2004. Samples from 2003 were used to index soil organic matter quality by measuring soil microbial biomass using a modification of the chloroform fumigation incubation method (Jenkinson and Powlson 1976, Tracy and Frank 1998). Extraction of microbial biomass N from the fumigated soils was processed with a Lachat analyzer. Analyses were done on soil from the gardens (n=15) and soils from the pastures (n=15). In 2004, soil nutrient analyses were performed by Iowa State University Soil and Plant Analysis Laboratory. Combustion analysis was done for organic C and total N. P and K were analyzed with Melich-3 extractions, and 1:1 pH analysis was done. Economic Analysis To calculate a net return per plot, the costs of all inputs such as seed, feed, and fuel were accounted. All expenses for materials having an expected life exceeding one year were amortized over the expected lifetime of use. Projected maintenance costs were not accounted for. Economic yield data are presented in English units to preserve relevance to US production. Vegetable and poultry yields were recorded and then converted to a yield rate by dividing the treatment mean yield by the square area devoted to the production of that crop (crop area). Market values are based on retail product value as determined from consultation with the project’s farmer advisory committee and by surveying prices at the Urbana Farmer’s Market. Gross income was calculated by multiplying yield rate by market value by crop area. Net income per plot was determined by subtracting expenses from the gross. Economic analyses were done using 2003 yield data only.
Poultry Productivity
There were no differences in chicken dressed weights due to pasture type (p=0.6082). Linear regression showed a positive linear growth rate of 57.4 grams per day for the period between 35 and 75 days of age. Feed conversion efficiency averaged 3.62:1 of feed to dressed yield over the two years of the study. No mortality occurred in either year.
The lack of significant differences in chicken dressed weight due to pasture type most likely arises because the bulk of the chicken’s diet was their grain ration and the pasture acted more as a supplement. It is believed that chickens on pasture will forage for no more than 30% of their intake, and probably less (Salatin, 1993). Unlike ruminants which can extract substantial quantities of protein and carbohydrate from plant tissues, poultry are probably more constrained to extracting minerals and roughage from forages and are dependent upon grain and animal protein for proper nutrition. However, the literature is devoid of studies that explicitly evaluate the digestive performance of poultry raised on pasture. The growing popularity of pastured poultry should underscore the need for research to evaluate the contribution that forages can make to the diet and economy of pastured poultry production. Nonetheless, the report from Gorski (1999) and the work of Lopez-Bote et al. (1998) suggests that poultry are capable of assimilating the supplementary nutrition offered by fresh pasture and implies that pasturing chickens confers nutritive value to the final product that confinement birds lack.
Vegetable Productivity
Squash yield, averaged over two years, differed significantly by treatment (p< 0.05). Greatest two year mean yields came from the control. Lowest two year mean yields came from the diverse pasture mix treatments (GRZ-MIX and UGR-MIX) and the ungrazed alfalfa. Main effects of both pasture type and grazing significantly affected yields. Squash plants surrounded by alfalfa pastures yielded higher than those in the diverse pastures (p=0.0002). Squash yield was also higher in beds surrounded by grazed pastures compared to ungrazed ones (p=0.0005). Tomato yields were significantly effected by treatment (p<0.05). Again highest yields were from the control. The main effect of pasture type did significantly effect tomato yield (p=0.0042) and the tomato yield from beds surrounded by alfalfa pastures had higher yields than the beds surrounded by the mix pastures. Grazing of the pasture area surrounding the vegetable beds did not significantly effect the yields of tomatoes (p=0.10). Similar to the squash and tomatoes, dry bean yields were highest from the control. Significant main effects indicate that grazing the pastures surrounding the bean plantings increased yields of dry beans within those plantings (p=0.039) and that dry bean yield was more productive when surrounded by alfalfa pastures than diverse pastures (p=0.041). GRZ-ALF, GRZ-MIX, UGR-ALF and CTRL all showed similar yields of shallots, but the main effect of pasture type did have significant influence on yield (p=0.005). Shallot yield was increased in plots surrounded by alfalfa. Grazing the pasture surrounding the bed did not influence shallot yield (p=0.153). Carrot yield was similar among the treatments GRZ-ALF, UGR-ALF, and CTRL. Carrot yields from GRZ-MIX were equivalent to the yields from GRZ-ALF and UGR-ALF, but not the control. Lowest carrot yields came from UGR-MIX. Carrot yield was significantly higher in beds surrounded by alfalfa (p= 0.001) and by grazed pastures compared to ungrazed pastures
(p=0.039). No significant differences were observed in pepper yields (p=0.0595). There was a large degree of variability (CV = 52.7) observed in the pepper production of this experiment.
Despite variation in yield there were few clear differences in garden soil fertility among the treatments. Treatment had no effect on garden soil microbial biomass, and net N and C mineralization potentials. With the exception of the elevated potassium levels in the control, the highest yielding treatment (CTRL) and the lowest yielding (UGR-MIX) were identical in bed pH, total N, total C and P. It seems unlikely therefore that soil fertility was the influential factor on yield.
Within the treatments, the main effects of both grazing and pasture type influenced yields, depending upon the crop. In general, yields were higher when the crop was surrounded by grazed rather than ungrazed pasture, and when the pasture composition was alfalfa rather than the diverse mix. The influence of these main effects may be operating through several mechanisms. While it is possible that the alfalfa N fixation might have influenced vegetable productivity, the control’s outstanding productivity, and the higher yields of vegetables surrounded by grazed pastures compared to the vegetables surrounded by ungrazed pastures of the same composition remains unexplained.
The significant main effects on vegetable yields, and the absence of differences in garden soil fertility suggest that pasture composition and grazing may have had a strong influence on the physical conditions of the garden environment. The taller, denser vegetation of the ungrazed and diverse pastures may have created cooler soils that subsequently impeded warm season crop development (Olasantan, et al., 1996, Stone, et al., 1999, Hoyt, 1999). Furthermore, yields of the cool season crops responded less to treatment, again suggesting that growing conditions and not soil fertility within the beds could be constraining productivity within these systems.
Work by Biazzo and Masiunas (2000) on pepper and okra (Abelmoschus esculentus) strip planted into living mulches implicated competition for N as being yield limiting when compared to conventionally tilled plantings. Additionally, they cited differences in N demand between perennial legumes and grasses after a time of establishment as an influence on N competition between the crop and its living mulch. The disparity in the establishment times in this experiment between the newly established mix and the preexisting, 18 month old alfalfa used as pasture, could have exacerbated any N competition effects. The 18 month old alfalfa would have been less demanding of N than newly established alfalfa, and less demanding again than a grass/composite/brassica mix (Scarsbrook, 1965). This reduced competition would account for the high yields of the control, and for the significant main effect of pasture type on the yield of all crops. The significant main effect of grazing on the yields of squash, dry beans, and carrots may have been due to the alleviation of some of this competition through manure deposition upon the pasture. These results suggest that in an applied integrated production system the bed area should be allowed a significant clean cultivated border between it and the pasture area and a pasture containing a substantial community of legumes would be favorable so as to limit the interference due to N competition of the pasture area on the vegetable production area.
Pasture Productivity and Quality
Pasture productivity from 2004 showed a significant time x treatment interaction (p=0.0295. However, while production of biomass may have been similar between treatments at times, the yield of actual forage from this biomass was very different. The component of the biomass contributed by forage species showed no differences in May of 2004. In June, the GRZ-ALF had the lowest proportion of forage in its biomass. During August and September, the MIX treatments maintained the highest percentage of their biomass as forage while the forage content of UGR-ALF and GRZ-ALF declined. Data of species composition averaged from three sampling dates in September of 2004 reveals that approximately 75% of the biomass of GRZ-ALF was from weed species. In contrast, GRZ-MIX was approximately 98% forage with 75% of the total biomass coming from perennial rye grass alone. UGR-MIX had <1% weed biomass and an even distribution (~25% each) of perennial rye, chicory, tall fescue, and alfalfa.
Grazed pastures regularly received manurial inputs and productivity could have been boosted by these nutrient additions. Also, the removal of plant biomass by the chicken’s foraging activities could have influenced productivity by preventing plant senescence, relieving inter and intra plant competition, and conserving plant available moisture (McNaughton, 1985).
Additionally, the influence of a sampling effect, described by Tracy and Sanderson, (2004), where, by chance, a few of the mix species were optimally adapted to the grazing regime may also have been a factor influencing forage yield. This is implied by the species composition data mentioned above. The effect of grazing on pasture composition suggests that the observed yield differences between treatments may also be explained by the success of perennial ryegrass in the MIX grazing system rather than to diversity per se. A grazed monoculture of perennial ryegrass might not have yielded differently from the grazed mix. However, high weed biomass in both grazed and ungrazed alfalfa does imply that it is unsuitable as a monoculture in this application. Alfalfa in combination with an appropriate grass however, might optimize the benefits of pasture protection from the grass with the quality and palatability benefits of alfalfa.
Poultry grazing appears to have influenced forage quality both directly and indirectly. The May 2004 crude protein content was highest for the alfalfa treatments. This trend repeats in July. However, by September, GRZ-ALF had the lowest crude protein, contrasting with UGR-ALF and GRZ-MIX, which maintained the highest values. Grazing and mowing likely maintained the vegetative state of forages and directly affected crude protein and relative feed values when compared to over-matured, ungrazed or unmowed forages. Also, the high levels of nutrients in the September 2004 GRZ-MIX forages can in part be attributed to the effect of manure deposition on those pastures.
There were no differences in phosphorus content of forages throughout the 2004 field season until September. The two ungrazed treatments were then lower in P content than GRZ-MIX but not different from each other. GRZ-ALF had the lowest P content in September. Potassium mirrored the trend of phosphorus with no significant difference in forage quality until September, when GRZ-MIX had the highest content.
Weed invasion the significant, indirect factor influencing the decrease in forage quality of the grazed alfalfa. Alfalfa is a tap rooted, generally upright plant with a significant amount of bare space between individual plants. The availability of space, coupled with the regular canopy removal, soil disturbance, and nutrient input from poultry grazing appears to have favored invasion of these pastures by weedy annual species. The MIX treatments, in contrast, contained grasses whose dense bunches reduced bare spots and were resistant to disturbance by poultry grazing. Additionally, the seed mixture of the MIX treatments contained forage turnip (Brassica rapa), an annual plant that establishes and grows quickly, but does not overwinter. Forage turnip has been shown to inhibit weed invasion in pastures (Tracy and Sanderson, 2004), and may have acted as a nurse crop suppressing weeds, supporting the bulk of the early grazing pressure, and maintaining a microclimate favorable to the establishment of the perennial, cool season forages.
Invertebrate Surveys
The main effect of pasture type significantly influenced the abundance of worm casts (p=0.004) observed on the soil surface of pasture areas in August of 2004. Highest numbers of worm casts were found on the surface of the soil in diverse pastures compared to alfalfa pastures. Casts were entirely absent from the tilled treatment. The probable cooling effect resulting from the dense pasture sward of the MIX treatments may also have been responsible for encouraging worm activity in these plots (Olasantan et al., 1996). This dense sward may also have shaded the soils of the MIX treatments making them moister than those of the alfalfa treatments and furthering their appeal to earthworm species (Ikeorgu et al, 1989). Studies have shown increased earthworm biomass in response to increased grassland diversity, but it is likely the presence of greater aboveground biomass and the resultant increase in detrital input that is either attracting more worms or encouraging greater activity (Spehn et al., 2000). The presence more worm casts in the MIX pastures, and the capability of worms to ameliorate damaged soils and enhance the fertility and nutrient cycling processes of functioning ones indicates a strong potential for diverse pasture systems to restore a variety of soil functions to farmscapes (Ross and Cairns, 1982).
Repeated measures analysis of squash bug egg counts showed no significance of the main effect of treatment (p=0.31). However, a specific comparison of squash bug egg abundance between grazed and ungrazed treatments using a linear contrast revealed that grazed treatments had fewer squash bug eggs than ungrazed treatments (p=0.038). It is unclear whether poultry grazing had a direct or indirect effect upon the abundance of eggs laid in the vegetable beds of the grazed treatments. Whether predation by the chickens, enhanced predation by other arthropods in the systems, or an inhibiting effect of the habitat, it appears that squash bugs were not able to successfully lay eggs within the vegetable beds of grazed pastures after overwintering in the area. The harboring, and encouragement of overwintering pests such as the squash bug is often used as an argument against the maintenance of shelterbelts and filter strips within cropping systems (Adam, 2004). These results, however, indicate that through an integrated approach some pest species may be reduced within these systems while preserving the perennial plant communities valuable to the health of farmland habitat (Ryzskowski 2002a, Ryzskowski 2002b, Duelli,1999).
Repeated measures analysis of the Hymenoptera parasitoids from the vacuum samples taken from the garden beds in 2003 showed a significant main effect of treatment (p= 0.0014) and the interaction within the main effect of treatment was also significant (p=0.003). Parasitic Hymenoptera were most abundant in GRZ-MIX and UGR-ALF. UGR-MIX and GRZ-ALF had similar abundances as UGR-ALF, but not GRZ-MIX. GRZ-ALF and UGR-MIX had similar mean abundance of hymenopterans as CTRL, which had the lowest mean.
Furthermore it appears however that GRZ-MIX sustained hymenopteran abundances at a higher level for a longer period of time than the other treatments.
This effect likely results from the interaction of pasture type and grazing. The high abundance of parasitoids in UGR-ALF can likely be attributed to the presence of alfalfa blooms present in those pastures. GRZ-ALF was not mowed in 2003, and the alfalfa flowers would have offered a nectar source to the adult hymenoptera, thus attracting them to those plots (Baggen and Gurr, 1998), particularly in July. Grazing of the alfalfa limited the degree of flowering occurring in GRZ-ALF, perhaps enough to account for the observed reduction in parasitoid abundance. The abundances observed in GRZ-MIX may be attributed to the creation of favorable habitat conditions within this treatment. It has been shown that many hymenopterans favor cooler, more shaded, and moister habitat conditions and will migrate to and stay within them preferentially (Desouhant, 2003, Coll and Bottrell, 1996). Additionally, it is possible that the bottom loading of nutrients in these systems from detritus and chicken manure could be encouraging increased populations at higher levels either through increased reproductive success or greater availability of host insects (Joshi et al., 2004).
Spider in 2003 and 2004 both years showed significant time x treatment interactions (p<0.01) and were thus analyzed using linear contrasts within each sample date of each year. On the June 26, 2003 sample date, spider abundance within the plots was significantly higher in grazed pastures (p=0.009) and in the diverse pastures (p=0.04). Spider abundance on July 24, 2003 was significantly higher in grazed pastures (p=0.039) but the effect of pasture type was not significant. On August 22, 2003 the treatment interaction was significant (p=0.003). On this date, greatest abundances of spiders were in GRZ-MIX and UGR-ALF. Spider abundance within GRZ-ALF was similar to UGR-ALF, but not GRZ-MIX. Lowest abundances were in UGR-MIX and CTRL. In 2004, the main effect of grazing was significant on July 22 and August 4 of that year, and spider abundance was higher in grazed plots on those dates (p=0.025, and 0.023 respectively). On June 18, 2004 the main effect of pasture type was significant (p=0.015). The abundance of spiders within the plots was significantly higher in the plots containing alfalfa pastures.
Pitfall counts of carabid beetles showed very different responses between years. There was a significant time x treatment interaction in 2003. There were no differences in carabid abundance among treatments on June 26. On July 24 and August 22 there was a significant effect of the treatment interaction on carabid abundance in the plots (p=0.003 and <0.0001, respectively). On July 24 the highest abundance of carabid beetles came from CTRL and GRZ-MIX. Lowest abundances were observed in GRZ-ALF, UGR-MIX, and UGR-ALF. UGR-ALF however, had similar abundance as GRZ-MIX. On August 22 greatest carabid abundances were observed in GRZ-ALF and UGR-MIX. UGR-MIX, GRX-MIX, and CTRL all had similar abundances, and CTRL and UGR-ALF had the lowest abundances. In 2004, however, the main effect of treatment on carabid abundance was significant (p=0.0016). Within the treatment effects, the main effect of grazing was significant (p<0.0001). Greatest abundances were observed in grazed pastures compared to ungrazed pastures.
The increase in abundance of both spiders and carabids within grazed systems at certain times is, on the surface, counter-intuitive. Clark and Gage (1996) observed that chickens were significant predators of spiders and carabid beetles. The containment of the chickens in portable shelters may have limited their capacity to graze out these organisms and allowed the majority of the pasture to function as a refuge. This method of managing the grazing rotation may have created a type temporal diversity that Altieri (1999) cited as being an important to restoring ecosystem functions to farmland and McNaughton (1985) noted as being of preeminent importance to natural grazing lands. But this would not necessarily explain the enhancement of spider and carabid beetle populations that was observed in grazed pastures. An abundance of food sources resulting from increased trophic complexity was possibly the significant factor influencing predator arthropod abundance in grazed pastures. The regular deposition of manure, and a high degree of plant detritus from chicken foraging activity would have been the base inputs supporting a community of decomposers and detritivores. This community could have, in turn, served as the basis of a food web that included carabids and spiders as well as hymenopterans (Joshi et al., 2004).
The suggestion that poultry grazing increased trophic complexity and resulted in greater predator arthropod abundance is supported by the data demonstrating a significant main effect of grazing on collembolan abundances. Abundances of collembolans in both 2003 and 2004 had a significant main effect of treatment (p<0.0005). In 2003 the main effect of grazing within treatment was significant (p=0.0089). In 2004 the abundance of collembolans collected from pitfall traps in the plots was significantly affected by pasture type (p=0.023) and grazing (p<0.0001). Collembolans are decomposer detritivores and their abundances have been shown to be responsive to bottom-up control (Ferguson and Joly, 2002). They are significant indicators of nutrient cycling processes (Meyer, 2005), and are a significant source of prey for other arthropods (Ferguson, 2001). Collembolan population response to grazing, taken in conjunction with data from three groups of invertebrate predators suggests that the populations of all four groups of arthropods was enhanced by the trophic complexity resulting from the foraging activities of chickens rotationally grazed within the pastures.
However, it should be noted that all spider and carabid samples were relatively low in species richness, seldom containing more than four morpho-species of each order. It has been demonstrated that grazing will exert a selection pressure on arthropods limiting diversity to those species best suited for the agriculturally-induced conditions (Dennis et al., 1998). This response is similar to the sampling effect in the pasture species composition data. For example, the difficulty for orb weaver spiders to establish themselves in grazed compared to ungrazed or unmowed grasslands is easy to imagine – they would suffer from a lack of structural diversity (McNett and Rypstra, 2000). This suggests that undisturbed areas still have a strong role to play in maintaining a healthy diversity of organisms on farms.
Soil Fertility and Nutrients
Microbial biomass, measured in 2003 only, showed no significant differences among treatments in both the pastures and the garden areas. Additionally, mineralization potentials for N and C were unaffected by treatment in 2003. While analyses from 2003 showed no significant effect of the treatments on microbial biomass or nutrient mineralization potentials, the results from soil samples taken in 2004 suggest that grazing did affect soil fertility levels. In 2004, soil nutrient content analyses were done on both pasture and garden bed soils. Soil pH in the pastures was significantly affected by the main effect of grazing (p=0.001) and was lower in the grazed treatments and the control than the ungrazed treatments. Pasture soil phosphorus was also significantly affected by the main effect of grazing (p<0.0001). Highest mean soil phosphorus was in the grazed treatments. The main effect of grazing significantly affected soil potassium content also (p<0.001). Pasture soil potassium content was highest in GRZ-MIX and then GRZ-ALF treatments. Total nitrogen in the pasture soil was significantly affected by the main effect of grazing (p=0.03). Some of the highest total N amounts were found in the GRZ-MIX and GRZ-ALF treatments. The elevated levels of P, K, and total N, and the reduction in soil pH in the grazed pastures is most likely due to the addition of manure from the poultry as well as the incorporation of torn, scratched and matted forage litter. Reduced soil pH in the grazed treatments was likely due to the acidifying release of H+ during the nitrification of NH4+ from the poultry manure (Franzlubbers et al., 2004) while the pH reduction observed in the soils of CTRL were likely due to the stimulatory effect that tilling has on decompositional processes through the incorporation of oxygen and organic matter into the soil (Calderon, 2002).
Total carbon of the pasture soil was significantly affected by the treatment interaction (p=0.044). Carbon content was lowest in the CTRL, although this mean was not significantly different from the means of GRZ-ALF and UGR-MIX. The potential for a pastured poultry system to add nutrients while maintaining or building total carbon in the soil implies that integrating pastured poultry into a farming system could be an effective way meet crop fertility demands organically. However the data on soil levels of P and K, as well as the forage quality data on P and K in GRZ-MIX forages suggest that the potential for nutrient loading should be a serious consideration in maintaining this system(Sharpley et al. 1998).
Soil pH in the garden beds was significantly affected by the main effect of grazing (p=0.016). Soil pH in GRZ-MIX was lower than CTRL. GRZ-ALF and UGR-ALF were not different from CTRL. Highest garden soil pH was in CTRL, UGR-ALF, and UGR-MIX. Garden soil potassium content was highest in CTRL, all other treatments were similar to each other. There was no significant effect due to treatment on soil P, total N or total N of the garden soils.
Economic Analysis
While highest yields in some crops came from the control, greatest net profits came from the grazed alfalfa. The CTRL and GRZ-ALF treatments netted $16.19/ plot and $91.43/ plot respectively. The high productivity of the control was offset by the expense of the tiller necessary for the production method. The grazed alfalfa system replaced the depreciating machinery with profitable poultry, and converted tilled ground into productive space.
While these data pertain to the specific trials observed, there is legitimacy to the critique that the ratio of tilled ground to vegetable production area within the control did not necessarily represent a realistic production model. A production system where the entire plot space was optimally occupied by pathways and several vegetable beds, as opposed to one bed surrounded by a large tilled area would certainly be more profitable than the control used and could have stood as a more practical control for an economic comparison, but would have complicated analysis of the agronomic and ecological data. Additionally, given that three or even four poultry cycles can be carried out in a growing season, and that the 22 day rotation was too long for proper pasture maintenance, and that these extra paddocks could be employed as vegetable beds, it appears that the grazed system could be speculatively optimized as well. As these speculations would go well beyond the collected data and create a slippery slope of hypothetical accounting I choose to only address the real data collected, accept its limitations, and address the three main principles that they illustrate. Primarily, the tilled system achieved its management goals through dependence on expensive and finite or depreciating inputs while the pasture based system used a low cost profit generating method. Secondly, there is an important distinction to be made between productivity and profitability. The success of the grazed alfalfa at producing profit without necessarily being the most productive treatment in terms of vegetable yield raises the question of how to assess the value of a production system. The use of increased yield as the yard stick of success within agricultural research may no longer be universally appropriate or at least not as a stand alone measure, especially when assessing sustainability. Finally, while an optimized version of the control would likely increase net return compared to the actual control employed, it would likely still be comparable to an optimized grazed system and would do nothing, in and of itself, to address the demands for pest and weed control, fertility maintenance, and land health.
REFERENCES
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Dennis, P., Young, M.R., Gordon, I.J. 1998. Distribution and abundance of small insects and arachnids in relation to structural heterogeneity of grazed, indigenous grasslands. Ecological Entomology. 23: 253-264.
Desouhant, E., Driessen, G., Lapchin, L., Wielaard, S. 2003. Dispersal between host populations in field conditions: Navigation rules in the parasitoid Venturia canescens. Ecological Entomology. 28: 257-267.
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Ferguson, S.H. 2001. Changes in trophic abundance of soil arthropods along a grass-shrub-forest gradient. Canadian Journal of Zoology. 79: 457-464.
Ferguson, S.H., Joly, D.O. 2002. Dynamics of springtail and mite populations: The role of density dependence, predation, and weather. Ecological Entomology. 27: 565-573.
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Educational & Outreach Activities
Participation Summary:
Thesis
Deposited “The Agricultural and Ecological Functioning of a System Integrating Raised-Bed Vegetable Production and Pastured Poultry” at the University of Illinois in July of 2005.
APPPA Grit
Published findings in this organizations Winter 2006 newsletter.
Backyard Chicken Effort 2004 - Present
Organized a neighborhood cooperative to raise poultry in our urban community.
Conducted coop building workshops and organized bulk feed and chick ordering.
Featured in local paper and New York Times, plus local television newscasts.
Pastured Poultry Conference, Bourbonnais, Ill. February 2005
Presented results and fielded questions from farmers at this practical workshop meeting.
CSSA-SSSA-ASA 2005 meeting
Poster presentation of results to the scientific community.
MOSES Upper Midwest Organic Farming Conference 2004
Presented project in poster format and distributed information about pastured poultry and land health.
Project Field Day 2004, 2005
Hosted outreach field day and conducted a pastured poultry workshop focusing on the ecological and agricultural aspects of the project.
Horticulture 101
Hosted a field trip and planned a lesson for this university class during the summer of 2004.
Agro-Ecology Newsletter, U of I.
Project initiation and preliminary results reported in Vol. 13, # 4.
Food Festivals
Catered a gala dinner for Urbana Park Districts ‘Thought for Food Festival’ (2004) featuring locally produced meats, vegetables, and fish.
Catered ‘Chicken Fest’ barbeque dinners (2004, 2005) featuring our pastured poultry to raise community awareness of the project and its implications.
Farmer Advisory Committee
Worked with local farmers to steer the project and to assist with their on-farm pastured poultry operations so as to gain relevant experience.
Project Outcomes
The integration of pastured poultry in a farming system can help to maintain productivity, improve profitability, and restore land health. When paired with the diverse pasture composition, forage yield and quality was enhanced and invasion by weedy annuals was suppressed within the grazed systems. The potential to control a pest species was enhanced while the perennial plant habitat within the system was preserved. Additionally, the population levels of three significant groups of arthropod predators were elevated within the grazed treatments. These organisms, considered in conjunction with greater abundance of decomposer organisms such as collembolans and earthworms suggest that these grazed systems are more trophically complex and nutrient cycles more tightly integrated. Finally, the grazed systems exhibited a capacity to build fertility and stimulate nutrient cycling while protecting soils from erosion or depletion.
The potential to fulfill the qualifications of the land health, as defined by Aldo Leopold, and to ensure the renewal of the farm and the farmland by securing the economic and environmental assets needed for a successful, sustained agriculture, appear to be present in this integrated system. The mechanics of this system, and its principle of restoring ecosystem functions are, more so than the explicit details of the system, likely the key to creating agricultural systems with land health restoring capacities. The particular combination of broilers and raised beds are merely one manifestation of the myriad combinations that could prove to be successful on the farm. It will be the choices of independent farmers, who hopefully employ some of the principles illustrated here, that create the unique combinations of crops and systems that best suit and define their own individual perspective and farm.
Moreover, it will be a public that is aware of the contributions to land-health that such conscientious farmers are making, and who are more directly connected with their food sources, which will help create the markets necessary to support this kind of agriculture.
Economic Analysis
Please refer to the 'Economic Analysis' section of the results, as this information was included as data within the study.
Farmer Adoption
Pastured poultry has grown in popularity among producers as well as consumers. But the options for integrating poultry are hardly exhausted. The specific integrations are as diverse as the farms on which they take place, but a few examples include: greenhouses, composting systems, following cattle, in urban settings, as crop rotation, and in conjunction with aquaculture.
While the potentials are vast, those looking to invest in these operations should carefully consider their production, processing, and marketing methods and costs before committing significant finances to the endeavor. The margin of return can be slim, especially if processing and marketing are done off farm. Additionally, while some systems designs have become complex, and on a large scale, expensive, start simple and make those adjustments that suit your specific, individual scenario.
Areas needing additional study
Additional study needs to be done on the nutritional impact of pasture on poultry. This should be done for broilers, layers, and turkey, ducks, and geese. The economic, and environmental impact of supplementing grain with pasture needs to be assessed, in order to have a bottom line statement on the contribution of grass to the production of poultry on pasture. Furthermore, research, and the mainstreaming of the results of that research, needs to be done on the impact of pasture on product quality (eggs and meat) and human health.
In terms of pasture, more knowledge of poultry impacts on pastures, and in conjunction with other grazing animals needs to be investigated. Also, work into developing ideal poultry pasture mixes would be helpful. Finally the use of poultry on cover crops and other annual pastures should be investigated as a means of conserving resources, developing fertility, and expanding farm marketing opportunities.
Finally, a concerted effort of investigating Leopold’s defining terms of land health, and the potential for farmlands to restore and maintain it is desperately needed if we are to progress with our efforts to manage our lands effectively.