Lens into the vineyard: Compost Spreading
We use compost as an essential building block for achieving balanced soil health at Ibarra-Young. We make our own biodynamic compost using the vineyard prunings, the post harvest pomace, organic hay, duck egg shells, organic dairy cow manure from our friends at Motley Crew Ranch, basalt dust, and biodynamic preps 502-507 (video on compost making coming soon). But this year our farm compost isn't ready, so we brought in 50 tons of organic certified dairy compost to help our vines and soil through the year.
Compost acts as a booster to natural soil processes. Compost adds nutrients, organic matter, and organic acid anions which increase soil microbiological activity, helps sequester carbon, and improves water infiltration and retention. Compost is a long term solution to giving our vines the proper soil microbial balance in order to make nutrients more available to our vine roots. We prefer to apply compost rather than commercial fertilizers because compost is a long term solution to achieving happy and healthy vines. As an analogy, I like to relate commercial fertilizers to cookies. Cookies are instant gratification, but you never get full and you always want another one! Fertilizers are a bandaid to keep plants producing, but they aren't a long term solution to achieving healthy soil and vineyard ecology.
Why dairy compost? Dairy compost is thought to be the most powerful compost source for one main reason without getting into the mystical examples that coincide with biodynamics. Primarily, cows have a robust digestive tract and their food is very well digested through their 4 stomachs. Considering this, there are rarely any viable weed seeds and their food has already been thoroughly digested.
Compost application rates in vineyards vary significantly. I've heard that the French rule of thumb is, "whatever tonnage you harvest from your vineyard is the amount of compost you should apply at the beginning of the next season." I like this rule. It makes sense that you'll need to replenish the same amount in order to receive the same bounty the following season. That being said, this rule only makes sense for generally healthy and well producing vineyards. Low yielding vineyards, or vineyards that may have some soil health imbalances should receive much more compost. This year, I chose to apply at a rate of 5 tons/acre (2 tons/hectare). The vineyard hasn't received compost in 8 years, and I know it needs a little boost. In general, I think adding 2-7 tons of compost annually is pretty good rule of thumb.
Compost can be applied in vineyards a few different ways too. According to a recent study at UC Davis, there doesn't seem to be any long term vine health/yield differences to surface broadcasting under-vine, surface broadcasting in the middle of the row, or tilling in. Because we are practicing no-till, we decided to surface broadcast a big hefty scoop under each emitter, and surface broadcast the center of every-other row in most blocks. This should give the vineyard's soil a solid boost for the next growing season.
It is important to get compost down before the rainy season to give all the microbes and nutrients the best shot at digesting and making their way down into the root zone. Applying compost is our second to last step to putting the vineyard to rest for the winter.
Renee, Toph, and I took turns shoveling our compost off of the back of our flatbed over the course of 2 days. It was a serious job, but we had a good time, drank a few beers, and built a little muscle along the way. Lady Blue mostly got in the way, but she had a great time rolling in the pile of compost all weekend and earned the coveted title of "Poo Girl."