Central Coast vineyard team

Wines & Vines, August, 2002

(Article taken from CCVT's "Update for Winegrape Growers" newsletter, Issue: May, 2002.)

As part of a larger sustainability program, the Diageo Chateau & Estate Wines company is developing a sustainable method of managing the 1,700 to 2,000 tons of pomace it produces each harvest at the Diageo Paicines Winery, also known affectionately as Blossom Hill, in Paicines, Calif. The company has also committed to sustainable practices in both the vineyard and winery operations at the San Benito Vineyards, which Diageo purchased in 1989.

Managers reviewed the economics of each practice in all of the operations. In one example, management realized that they were paying approximately $20,000 to remove 700 tons of pomace from the site.

After crunching a few numbers, managers decided to begin a composting project on site that would accommodate the pomace, produce organic material and return it to the vineyard to improve soil quality Stasi Seay, Central Coast wine-growing representative for Diageo, explains that once the decision was made, the company invested in the equipment and expertise necessary to produce quality compost.

"The company was already spending $20,000 per year to have someone haul away the pomace. That person was eventually composting the pomace and selling the compost. To save transportation costs and return organic matter to the vineyard, we decided to create an in-house composting operation," Seay explains.

During the 2000 crush, the pomace was piled into manageable rows and composted alone. However, the resulting compost was not complete in nutrients. In 2001, Diageo decided to hire experts to help them with their project. The company contracted with Don Cranford Composting, Inc. of Spreckles, Calif., to provide technical expertise, training and direction.

"This site has very good potential to create a quality compost," Cranford explains. Cranford also helped his clients purchase equipment to facilitate the composting process. First, Diageo purchased a used turner, which allows the compost material to be turned periodically. They also purchased a used shredder, which shreds the straw before it is added to the compost pile. Managers also wanted to address nitrogen buildup in the winery's settling ponds, so this season they planted sudan grass in and around the ponds to take up excess nitrogen. Eventually, the harvested sudan grass will be blended with the pomace to produce compost. The company hopes eventually to produce all the organic matter needed to blend with the pomace without having to leave the vineyard.

In the first year of operation, Cranford recommended that straw and steer manure amendments be added to the aging pomace in order to stimulate microbial activity. This raises the temperature of the compost pile. In the future, as fresher pomace is used, there will be less need for the straw medium as a carbon source, because the sugars remaining in the pomace will be an excellent food source for the microbes and bacteria. Straw was purchased from local growers in the spring when it was plentiful and affordable, and manure was purchased from local dairies and feedlots. The ratio of straw/manure/pomace depends on many factors and is determined by the age of the pomace and the quality of compost desired. Cranford also explains the importance of maintaining the internal compost temperature in the range of 135[degrees]-159[degrees] F. The minimum temperature limit ensures that all pathogens and weed seeds are sterilized. The maximum temperature limit prevents denitrification (i.e., losing the nitrogen to the atmos phere as a gas).

Equipment used for the compost operation includes a large tub grinder to grind up the straw and distribute it on the windrows of pomace. Steer manure is added to this mixture and is then combined by a compost turning machine, which also adds water while it is pulled along by a tractor at a very slow speed. It is critical to monitor the composting material's temperature throughout the process. By adding water and turning the compost rows, the temperature can be adjusted to keep it within the appropriate range (135[degrees] - 159[degrees]F).

Lupe Reyes, Diageo's vineyard manager for San Benito Vineyards, is a novice to composting who enthusiastically oversees many details of this project. Through site training and advice from Cranford, Reyes is learning how to monitor the compost pile, check temperatures, add water or turn as needed. Adding water and oxygen (by turning the material) is how he maintains the recommended temperatures within the compost pile. He currently monitors temperature and moisture on a daily basis. On average, he spends about five to eight hours per week monitoring and adjusting the compost pile. From start to finish, it takes about eight weeks to produce the finished compost. This can change from year to year, based on temperature, sunlight and rainfall conditions. It is difficult to predict the volume of compost produced from the process. Cranford estimates that about 60% of the original weight will remain as compost. Seay and Reyes estimate that from this batch they will apply approximately 4 tons per acre to a little more than one half of the vineyard. Specific application rates will vary depending on soil conditions. They'll use a side spreader to apply the compost, which they purchased specifically for this project. The compost amendment is used primarily to improve the soil humus, biological diversity and soil structure. While the compost won't completely fulfill the fertilizer requirement of the 700-acre vineyard, it will reduce the overall fertilizer needed for the site. They believe that improving the soil's quality will help its ability to cycle nutrients more efficiently in the long run.