To the many benefits of composting, add another: water conservation. When compost is added to bare soils as a thin layer, it is an effective barrier against evaporation of soil moisture, a practice called top- or side-dressing. Compost also reduces plants' needs for water by increasing how much water can be held by the soil - only a 5% increase in organic material quadruples the soil's water holding capacity.¹

[A] 2000 study … found that increasing the water holding capacity of the soil by adding compost helped all crops during summer droughts by reducing periods of water stress. The amount of water in … 8 inches … of the compost amended soil increased to 1.9 inches compared with 1.3 inches in un-amended soil. Since vegetables require 1 inch of water a week, at field capacity, the compost amended soil held a 2-week supply of water.²

Compost is the result of a process whereby a large volume of organic matter is rapidly decomposed into a smaller volume that is then used to amend the soil. Soil particles occur in aggregates or clumps, unless they have a high amount of sand particles that do not hold together well. Soil structure refers to the arrangement of sand, silt and clay particles into larger aggregates.³ One can assess the soil structure for their home or community garden by doing the soil-ribbon test and the soils-sedimentation test. This video from Kansas State University tells you how to assess your soil texture by feel. The bottom line is that amending the soil with compost improves its structure, which significantly affects how well it holds water.

Compost is decomposed organic matter that has stabilized, yet, still continues decomposing, though, at a slower rate. The organisms that break down organic matter release glue-like substances that bind soil particles into crumbly aggregates. These irregularly shaped aggregates have air-spaces between them and can be penetrated and occupied by water, nutrients, and plants' roots. Soils rich in organic material have a sponge-like quality that holds water and, thus, plants growing in them have lower water needs.⁴ In sandy soils with poor water retention, compost improves the soil's water holding capacity by improving soil structure ie., aggregate stability.

Unlike sandy soils, clay soils are characterized by small spaces between the small clay particles. Clay soils have good water retention capacity, however, the spaces in between the particles can fill with water quickly, excluding oxygen and nutrients, and, essentially, drowning the plants. Water saturation in clay soils may also cause soil runoff because those soils cannot hold more water, but, adding compost aerates clay soils and increases its capacity to hold water, oxygen, and nutrients needed for healthy plant growth.

Ultimately, regularly amending with compost lightens clay soils, thus, reducing run-off, and increases the water holding capacity of sandy soils, hence, reducing the need for water. Adding compost as a thin mulch layer over bare soils reduces water evaporation, while also reducing the need for water by garden and farm raised plants. Top-dressing with compost in combination with a thin top-layer of straw mulch in food-growing areas, or a thin woodchip mulch in ornamental garden areas, can reduce plants' water needs around their roots even more, where water is needed the most.

¹ Compost Fundamentals, Compost Benefits and Uses. Washington State University, Whatcom County Extension. Accessed on 28 January 2015.

² M. Charles Gould. Compost increases the water holding capacity of droughty soils. Michigan State University Extension. Accessed on 28 January 2015.

³ Dennis R. Pittenger, ed., California Master Gardener Handbook (University of California Agriculture and Natural Resources, 2002), 36.

⁴ For the Gardener: Building Fertile Soil. Center for Agroecology and Sustainable Food Systems, University of California, Santa Cruz (Santa Cruz, CA: University of California, no date provided).

A University of California-Davis research team is enrolling organic and conventional farms to participate in a research opportunity for small to medium size farms. The researchers are looking for volunteers to participate in the study to identify on-farm food safety practices that are specific to the unique conditions and needs of small to medium size farms, including operations that integrate livestock and fresh produce production systems. The long-term goal of the study is to develop innovative, cost-effective, scale-size appropriate food safety metrics and recommendations for risk reduction for farms producing fresh produce and animal products. Fecal-borne pathogens can be spread to fresh fruits, nuts, and vegetables through animal intrusions, or indirectly through contaminated water, or soil.

Project leaders, Dr. Michele Jay-Russell, Program Manager at the Western Center for Food Safety and liaison to WIFSS, and Dr. Alda Pires, Urban Agriculture and Food Safety Extension Specialist in the School of Veterinary Medicine, encourage farms with livestock and fresh produce production to volunteer. Dr. Pires (530-754-9855 or apires@ucdavis.edu), primary contact for the study, welcomes inquiries.

Marin County's waitlists for community gardens can be up to four years long. Exacerbating that problem is the fact that it can take up to seven years to launch a new garden. Clearly, the demand for community gardening is not being met in the county.* The problem is complicated by the fact that there are eleven separate municipalities in Marin, in addition to the unincorporated county lands and 19 school districts.

Of the approximately 75 public schools in the county, 50 have school gardens, most of which have problems sustaining their school garden programs, particularly in the summer time, and particularly in the lower-income communities of the county. A well-supported comprehensive school garden program is an uphill battle considering this fragmentation, but steps are being made.

Despite the individual wealth in many of our cities, our low-income communities suffer from a significant health and income disparity. This disparity shows up in longevity rates: in the Marin municipality of Ross, the average longevity is 88 years, and in the Canal area of San Rafael, the average longevity is 77.4 years – a 10.6 year difference. In one area of Novato, the difference is even greater at 75.2, or 12.8 years.** A big part of the solution to this health disparity is access to better nutrition. For educational reasons, as well as actual produce production, community and school gardens are a part of the solution and can be an integral part of a healthy and active lifestyle.

The Canal Community Garden in San Rafael took nearly eight years to launch, getting approvals, raising money, and finally building. The process was like pulling teeth in large part because policies are not in place to streamline approvals, and little funding has been dedicated to the issue. Additionally, public awareness of the important benefits of community gardens is still low. Potential benefits include community resilience, improved health, environmental benefits, community building, outdoor education, reduction in crime rates, and savings on food bills.

Individual residents' objections are often ill founded, or gardens are misunderstood. Most community gardens now adhere to strict performance standards which prevent many of the problems that residents imagine. Both broader public awareness of the benefits, and streamlining city ordinances would help facilitate approvals. This is true despite the fact that many city officials try to champion these projects.

Mill Valley's, original community garden, for example, has a waitlist of more than 70 people; a several year wait. Although many city officials supported the idea of a second community garden, it has taken seven years to launch the second 38-bed garden. It is the exceptional case when a community garden is launched is less time. Often the shorter time period is because the land and/or water is privately owned by faith-based institutions or individuals, and in one case, a golf course!

Efforts coordinated by The Marin Food Policy Council (MFPC) and UCCE Marin took on this problem on a couple years ago. Their focus is on food security in lower-income communities. The county has 32 low-income schools, defined by 30% or more of their student body on the government program Free and Reduced Meal Program (FRMP). They developed templates for planners, commissioners, and city council members to list community gardens in zoning codes as a “permitted use”, and charged a UCCE Marin Community Garden Program Coordinator to identify and develop a map of potential sites for community gardens in the county, and “encourage garden management support through meet-ups, garden tours, and a conference.” The meet-ups and tours provide a place for the exchange of ideas and best practices. The Coordinator position also allows for a centralization of some of the school and community garden material and resource needs such as seeds, starts, tools, compost, mulch, via seed/tool libraries, banks, material yards, or simple donations. Countywide garden volunteer coordination is part of this effort as well.

The fragmentation in the county makes these efforts very challenging, but it is exciting to push forward Marin County Urban Ag in this way!

*Marin County Community Garden Needs Assessment, University of California Cooperative Extension, Marin. December 2010 

**A Portrait of Marin: Marin County Human Development Report, 2012. (MeasureOfAmerica.org)

If you were to start an urban farm in a neighborhood, what would be your first step? Obtaining a lease for the land? Testing for soil contamination? Clearing out the accumulated trash? These are important steps. But an additional step should be considered first—that is, gaining the support of the local community.

Considering the multifaceted benefits of urban agriculture, it may seem counterintuitive that city residents would not welcome an urban farm with open arms. However, the idea of farming in a city (which differs from urban gardening in its emphasis on income-generating agricultural activity) can seem strange—and potentially deleterious—to local residents. We interviewed city residents, neighborhood leaders, and urban farmers to discover the strategies urban farmers use to obtain community support for their projects. Here are some highlights:

If you found this useful, check out this report to see additional recommendations for gaining local support for urban farming (a summary is also available).