The Agua Fria - New River Natural Resource Conservation District (NRCD) partnered with Sunfresh Farms And Sycamore Farms to develop the program to collect anecdotal and scientific data on an on-farm compost system. The program was funded by Arizona Department of Environmental Quality through the Clean Water Act.

Manure spreading is a common method of adding organic matter to agricultural land. However, there are problems associated with it, including increased weeds and pathogens, high moisture content requiring many loads to be spread, and quickly released nutrients which lead to possible contamination of surface and ground water. Manure, combined with carbonaceous material and allowed to decompose to a stable humus product, is called compost. The compost process kills weed seeds and pathogens, stabilizes nutrients, reduces the amount of trips needed for field application, and increases the benefits to soil structure.

This five year project is designed to meet the following objectives:

OBJECTIVE #1 Develop a cost effective compost method.

High population growth in the Phoenix metropolitan area and the desire of many people to maintain non-desert landscape has led to the increase disposal of organic matter into landfills. This material can be processed into a product, called compost, which can benefit the soil.

 

Organic material before (top) and after (bottom) the compost process.

 

In compost, nitrogen-rich material (manures, green grass, vegetables) is combined with carbon rich material (paper, straw, sawdust.)  Composters should be aware of the ratio between carbon and nitrogen.  This C:N ratio effects the type and amount of microorganisms present in the compost and will therefore effect the rate in which the compost proceeds.  In addition, compost too high in nitrogen will result in odors.

Also important in the compost process is the turning frequency, salinity, pH and moisture level.  These factors will also effect the types and numbers of microorganisms.

To develop a compost method, various parameters of the compost windrows will be tested and compared against existing standards:

1. Carbon to Nitrogen Ratio (C/N)
2. pH
3. Turning rates
4. Microorganism Populations
5. Salinity

OBJECTIVE #2 Monitor the effects of different compost application rates on nutrient content of soil and plant tissues and water retention rates of soil. 

Arid soils are naturally low in organic matter. When land is cultivated, soil organic matter content approaches zero. Organic matter, especially the more stable component called humus, is largely responsible for many soil properties affecting soil quality, including soil structure and Cation Exchange Capacity (CEC). Soil structure is important because it affects the flow of air and water into and throughout the soil column. CEC affects water and nutrient holding capacities of the soil.

Soil Testing Includes:

1. Nutrient Content
2. Organic Matter Content
3. Moisture Content
4. Water Infiltration Rates

Plant Tissue Testing Includes: Nitrogen Content

At harvest, yield is to be tested.

One reason Arnott Duncan became involved in the program was because of a phosphorus (P) problem. many of his crops were showing signs of P deficiency, however soil tests showed an abundance of P. Chemical fertilizers were not solving the problem, which was fixed P. This is a problem common in many western soils. These soils have high pH, due to high calcium content. The calcium compounds result in P being trapped in the soil matrix and therefore unavailable to plants.

Arnott applied 40 tons per acre (t/a) for the first application. The crops were not showing signs of P deficiency, where before they had. Following the harvest, the follow-up applications were 20 t/a and 40 t/a. In the field where 20 t/a was applied, germination rates were high, plant vigor was high, and no signs of P deficiencies were seen. In the field where 40 t/a was applied, germination rates were low. However, those that survived were vigorous and showed no signs of P deficiency. From this information, it can be inferred that an initial high application of compost with smaller follow-up applications is appropriate.

The application of compost addressed the problem of fixed P. Compost increases microorganism populations in the soil. There are two types of microorganisms that lead to increased available P. There are P-releasing microorganisms which release plant useable P during decomposition. In addition there are microorganisms, such as pseudomonads, that produce acids to solubilize the fixed compounds.

Beginning in spring 1997 a field trial was established at Sycamore Farms. The field trial had three treatments (no compost or control, 10 t/a, and 20 t/a). These three treatments were replicated three times on a 22 acre cotton field. In year one, the following measurements were taken:

1. soil organic matter (prior to compost application)
2. soil nutrient content (prior to compost application)
3. soil cation exchange capacity (prior to compost application)
4. germination rates
5. nitrogen content of plants (5/28/97 and 7/23/97)
6. plant growth and development, specifically height to node ratio, number of     fruiting sites and number of aborted fruits (5/28/97 and 7/23/97)
7. Yield (at harvest)

The soil organic matter content, soil nutrient content, and soil cation exchange capacity will also be sampled at the end of the field trial.

OBJECTIVE #3 Educate the community on compost methods and benefits. 

Materials are developed for educational purposes.

Sycamore Farms:
         

One plot of the garden is being used as a demonstration of compost.  Four rows have been treated with compost, four rows have not.  The children have planted radishes, lettuce, cabbage, broccoli and cauliflower.  Throughout the growing season, the children will observe differences between the composted rows.  Observations will include germination rates, size, taste, etc.

The Loyola Project, sponsored by Brophy College Prep, teaches urban children about gardening.

Sunfresh Farms:

Children, from preschool to high school, and adults, from Arizona to Slovakia, come to Sunfresh Farms to learn about environmentally sound agriculture. One stop on the educational tour is the compost windrows. Here the guests are informed of the importance of organic matter to soil and the process of composting.

To publicize the efforts of Sunfresh Farms, the local media have highlighted the achievements of the farm in environmentally sound agriculture and education with special references to the compost project. Wild Side, on Channel 12, Copper State Chronicles and What’s Up, both on Channel 3, have each dedicated one segment of their show to Sunfresh Farms. In addition, several articles in local publications have focused on Sunfresh Farms with special mention of the composting project; including, September '96 issue of California / Arizona Farmer. In February '97, Successful Farming, published in Iowa, wrote a cover story on the educational programs at Sunfresh Farms with an emphasis on the compost project. Sunfresh Farms has won two awards, the Valley Forward Association Environmental Excellence Award and the Governor’s Pride in Arizona Award for Environmental Technology, for their environmental and educational programs, including the compost project.

              

Arnott Duncan speaks to a group about the compost process.

The AF-NR NRCD shares the results with local growers and other interested parties through tours and bulletins. Anyone interested in the project will find updated data available on this website. Information is also be shared with the USDA Natural Resources Conservation Service for use in the nutrient management program.

Other venues in which information has been disseminated include:

1. Presentation at a composting conference, 1997 (Mike Moore)
2. Presentation at Arizona Association of Conservation Districts conference,  
    1997 (Kathy Killian, NRCD)
3. Presentation at Southwest Composting Conference, 1998 (Arnott Duncan)
4. Presentation at Southwest Composting Conference, 1998 (Kathy Killian)
5. Description in Agua Fria - New River NRCD annual report, 1997, and
    mailed to over 300 people (NRCD)
6. Discussions with other agricultural producers interested in developing
    on-farm composting programs (NRCD, Mike Moore, Arnott Duncan.)