Organic vegetable production in Monterey County has evolved over the past 25 years. It was once the domain of small- to medium-sized growers that produced for local direct market outlets or direct sales to local retail outlets. The community of smaller growers is still quite active, however, in the mid-1990’s larger scale producers began to produce organic vegetables for distant mass markets.
The value of organic production has increased over the years. For instance, organic production comprised 0.6% of the total value of agricultural production in Monterey County in 1995 and by 2015 it comprised 6.9% ($335 million). Spring mix salads and spinach are dominant crops, but romaine, romaine hearts, broccoli, and other cool-season vegetables are also produced. Organic products are now essential items that all major shippers supply to their buyers. As a result, the importance of organic production has increased and research organizations such as the California Leafy Greens Research Board have organic producers on their boards and fund research to help address specific issues that face organic growers.
Here are some of the main challenges I see for larger organic production:
1. Downy Mildew of Spinach
Plant diseases is a key issue among the myriad of issues that affect organic vegetable production. Downy mildew of spinach is an example of a particularly troublesome disease. In spite of the efforts by seed companies to develop resistant varieties to this pathogen, the disease continually overcomes this resistance, leaving organic growers vulnerable. In a recent cost study of organic spinach, it was necessary to discount the average yields of organic production due to this disease to accurately depict the reality of organic production.
Organically acceptable fungicides provide little effective control of this disease, and the main technique that organic growers employ to cope with this pathogen is early harvest to avoid infestations, thereby reducing yields.
2. Bagrada Bug
Other pest management issues that affect organic growers include the recent invasion of Bagrada bug. This insect had the potential to develop very high populations, especially on crops in the mustard family. Available organic insecticides have limited effectiveness, which — again — leaves organic producers vulnerable.
Weeds can be a serious issue for organic producers. Interestingly, larger organic producers that have ranches dedicated to spring mix and spinach production, crops that mature before weeds set seed, can eventually drive weed populations to low levels. However, growers that are producing long-season crops can have serious weed issues and careful, creative approaches to weed control (e.g., pre-irrigation, close cultivation, alternative cultivators, etc.) are all needed by organic growers to cope with weeds and to keep hand weeding costs at reasonable levels.
For instance, in the organic spinach cost study mentioned above, we assigned a cost of $440 per acre to hand weed the crop. This amount is a “typical” costs, but the reality is that this cost can be substantially higher if there is high weed pressure in the field.
Looking at the cost study for organic spinach, the other cost that jumps out just behind seed costs is fertilizer. Organic sources of nitrogen fertilizer cost substantially more than conventional nitrogen. The most common materials used are chicken manure pellets that contain 4% N, 4% P2O5 and 2% K2O (4-4-2). Although it is commonly referred to as “chicken” pellets, they are a combination of chicken manure blended with bone and meat meal. The blending is done to assure a consistent analysis of 4-4-2. Monterey County is fortunate to be relatively close to a large poultry industry in the Central Valley of California, which is the source of this material; organic fertilizer companies process the material into pellets and deliver it in a timely fashion to the growers.
I should point out that, for the most part, the organic vegetable producers in Monterey County rely almost exclusively on organic fertilizers to supply nitrogen for their crops. There is little use of cover crops in this area because of high land rents; in addition, there is little to no use of leguminous cover crops, because legumes are hosts to key diseases of lettuce, such as lettuce head drop (Sclerotinia minor). Growers are also limited in their use of fresh manures due to food safety concerns. These constraints explain why organic vegetable producers in this area are so dependent on fertilizer inputs.
Nitrogen in a material like 4-4-2 is in a form that cannot be immediately absorbed by the plant and must be broken down (mineralized) to plant available forms such as nitrate. The rate of releases of nitrate varies depending on soil temperature and moisture, and whether it is injected into the soil or is applied as a topdress application. Given that the soil in vegetable production fields is moist, temperature is the biggest factor affecting the release of nitrate from organic fertilizers. This issue crops up during cool spring conditions when a crop like lettuce can have trouble sizing up due to low nitrogen availability.
The placement of fertilizer also affects the release of nitrogen. In studies that we conducted last summer, we observed that about 50% of the nitrogen contained in 4-4-2 was mineralized to nitrate in seven weeks if applied as a top dress application verses 70% if it was shanked into the soil. The subtleties of nitrogen availability from organic fertilizers is a complicated matter in organic vegetable production and is one that organic growers struggle to overcome at times.
Organic vegetable production is a complicated enterprise. The good news is that the demand for organic vegetables is strong and there is a need to supply this market. However, it has many challenges that organic growers face to be successful.