#Soil Carbon in Saticoy

I’ve been doing some reading recently on the topic of soil organic matter, most notably in the book The Soil Will Save Us, by Kristin Ohlson. There’s a lot of discussion about sequestration of carbon in the soil, and what agriculture has done in the past and may do in the future to affect that amount. But much of the discussion relates to large-scale Midwestern farming – rangeland grazing and grain production. It doesn’t speak to Ventura County agriculture. How are we faring?

At our farm, we have had a covercrop program going in our orchard for 10 years, and it made me wonder… was there a good way to see a measurable difference for our efforts? Subjectively, we’ve been very happy with our results. Our program has prioritized erosion control and soil structure. We’ve never worried our soil carbon content. But a big part of a soil’s structure is determined by the organic material within, and organic material is a pretty good proxy for carbon. (Direct measurements soil carbon are apparently expensive and not that reliable.) Since we’ve been trying to add biomass, we must be adding carbon, right?

Out of curiosity, I decided to take a look at some numbers.

We haven’t regularly tracked our soil organic matter, but a fairly recent lab test shows us ranging between 5.5% and nearly 7%. (6.94% to be precise.) Unfortunately, we took no baseline measurement before starting the covercrop experiment, but I was able to find a figure to represent our soil in a “natural” state. According to the Web Soil Survey of the Natural Resource Conservation District, the Pico and Mocho series soils such as those at our Saticoy farm typically have only 2.5 – 3% organic matter.

5.5 to 7% sure beats 2.5 to 3%!

It would seem that we are holding twice the organic matter (and presumably twice the carbon) in our soil that existed in nature. I’m actually not that surprised to see an improvement, although double was unexpected. Orchards, even without covercrop, have much heavier vegetation than would exist here naturally, thanks to irrigation. That plant material that my family has been producing over 130 years is reflected in the organic content of our soil.

I’d love to have figures for other orchards in our area, and better data on our soil circa 2005, prior to the reintroduction of covercrops on our farm. If I were writing a PhD thesis, I’d need more data. But for a farmer looking for validation of his practices, this looks pretty good to me.

Worms

“I’ve been getting a lot more into earthworms lately.”

Odds are very good that only a few short years ago, this was a phrase I would never have thought to utter.  Possibly I would have thought it a sign of impending mental illness. But these days, it is the truth. These are pretty remarkable little organisms, and I find that I am having some success rearing them.

Why would I do that, you ask? Well, for starters, they are great consumers of our kitchen wastes. They break down our waste, turn it into soil, and them are released with their castings into the vegetable or rose garden. Of course, many get snatched up by our ever vigilant flock of hens, meaning some made their way (indirectly of course) to my plate this morning. When prepared in this fashion, I can heartily recommend worms for breakfast.

The other reason I’m raising them is for my “vermidrainage” project. At our Saticoy ranch, we have a compacted clay soil in our Block A, familiar by now to my handful of regular readers. We have been maintaining a cover crop to help break up the soils, and in the next couple of weeks, when we replant, we will attempt to create some natural drains in the clay pan. Basic concept is simple: Use the PTO auger to bore through the pan, then refill it with a mixture of active vermicompost, mulch, and a little of the original soil. A cap of mustard cover on top should add some deep roots, and make it easy to spot the sites. The hope is that this column of active soil will  allow water to drain, and serve as a colony for earthworms to spread through the covercrop rootsystems that surround them. Three 30 gallon barrels are serving as my hatchery. Of course a little vermicompost will go into each new tree’s hole as well.

I’m not alone in this new found interest. Friend and pathfinder Rose H-S alerted me to a blog piece from a young farmer named Devin Foote. If I was concerned for my sanity, then I am now doubly worried for Devin, since his thoughtful and detailed article suggests that he has given this much more thought than I.

Read it here.

Summer Covercrops

In earlier pieces I have alluded to a soil problem in “Block A”, 5 acres of 15 year old lemon trees. These trees should be in the prime of their lives right now but this block has always struggled. In the past 2 years, nearly 160 (one fifth of the acreage) have crashed. Soil analysis has shown no pathogens.  Our prime suspect is a clay pan which has developed only about a foot down. For the past two winters we have used covercrops  to get more organic material into the soils. Barley and rye for biomass, crimson clover for nitrogen, and a blend of mustards for both their biomass and deep taproots.

The clover has been a disappointment. Hard to start, it has not shown signs of nitrogen fixing as we had hoped, and has been a minimal contributor to biomass, either above or below ground. On the otherhand, the mustard has performed quite well. Almost complete germination, resitant to brief heat, the blossoms  helped support a humongous bee population while our trees were in bloom. Where there are bees, I expect there are other beneficial insects as well, so this should be helping with our integrated pest management efforts. Root penetration isn’t quite what we expected, but with water trapped in or above the clay, they haven’t needed to.

This coming month we will take our first stab at summer covercrops. We will alternate between rows with buckwheat, red cowpeas, and black-eyed peas. Since we have some crimson clover left over, we will also try a little as a warm season cover. Buckwheat is pretty much solely a biomass generator, but the others, being legumes, should give us some N. We may even harvest some of the black-eyed peas. Not sure if we can find a market for them though… This corner of rural/suburban Southern California isn’t a big soul-food kind of place. Anybody looking for some locally grown comfort food?

This summer cover program will go hand in hand with a high density replant of Meyer Lemons in the effected areas. The soils will further get a boost from tilling in the winter’s cover crop, a little organic sulfur, and a few shovels of our homebrew vermicompost for each tree. My philosophy is to “exercise” the soil, instead of “working” it.

Wish me luck!

For Marty…

A very good non-farming friend of mine has significant concerns with respect to global climate change, and more specifically how it may impact Ventura County agriculture. It has usually come up in the context of other related issues, but I’ve never been able to deliver a more complete accounting of the steps that our family farm has taken. So Marty (and anyone else interested in hearing about it)… this one’s for you.

Quick background: The “home ranch” is a piece of ground in Ventura County that has been in the family since the 1870s. Today it is primarily planted to lemons, but has seen oranges, walnuts, apricots, lima beans and sugar beets during our stewardship. The “Santa Paula ranch” is the baby of the family: my wife and I purchased it in 2001. It is primarily planted with avocados. Mostly I’ll be refering to the home ranch in this piece.

“Sustainability” is a recent term, but in the context of 130 years on the same piece of dirt, I think we have a few ideas on the concept. Sustainability Rule Number One for a farmer: stay in business. You can’t make a difference if you are not in the game. For us, regular changes in crop mixture has been one key. The other has been that in our family we have traditionally left the farm for higher education and pursued an outside career before returning. This has allowed us to bring fresh ideas, energy, and (yes) capital into the business on a regular basis. But once back on the farm, we have tried to remain pretty focussed on the day to day. I echo my Dad’s sentiment that the most valuable soil amendment is the owner’s footprints.

When we first moved into citrus in the 1930’s, we automatically became members of Associates Insectary. At that time the Insectary worked for the citrus co-ops, using benefical insects to manage pest levels in members orchards. Later membership became  farm by farm; we elected to remain with the Insectary. Eventually what they did would come to be called Integrated Pest Management, but back then it was just considered common sense.

Grinding pruning wastes to improve the soil has been done here at least since the 1960’s, probably earlier. But in the 1980’s we began to work with local tree trimmers to take some of their prunings. This extra organic matter has been a great addition to the soil… I only wish we had distributed it more evenly around the property. Some areas have really fantastic tilth, others are lagging.

We got after water conservation relatively early, converting the home ranch to microsprinkler from furrow in the early ’90’s. This not only reduces water usage by one-third or more but also allows for more precise and safer application of fertilizer, reducing total chemical load as part of the deal. And of course in California, water is energy, so energy expended to pump water goes down as well. When I converted the Santa Paula ranch from furrow to microsprinkler my energy usage dropped by 20,000 kwh per year. The figure for the home ranch is probably twice that, but we no longer have energy use data from before the conversion. They say that no good deed goes unpunished, and our early conversion to water saving technology was no exception. In 1996 water pumping from our groundwater basin was adjudicated. Because of our lower historical use, we recieved a smaller allocation of groundwater than some smaller neighbors, some of whom still use furrow irrigation to this day. So it goes…

In the last few years we have adopted covercrops primarily as a way to build our soil and get out in front of new regulations on run-off from agricultural land. Added benefits seem to take the form of improved weed supression and water infiltration. On the downside, we have more difficulty controlling snails and gophers. It also means that we are producing several extra tons of green biomass per acre, which has to be a plus in the  carbon equation, but I admit that I have not figured out how much. We should eventually see some improvement in soil nitrogen, but have not yet. If realized that would also reduce the need for commercial N fertilizer.

We have never really stopped looking at possible alternative crops. We didn’t jump on the Kiwi and Chermoya wagon in the ’80’s (thankfully), but a few years ago we planted a few acres of specialty citrus. At the home ranch that took the form of an acre of Meyer Lemons. These are now in production. Many have gone to the Sidecar in Ventura, but we are now able to ship small commercial quantities through Oxnard Lemon. Although this is a commercial channel, I understand most are staying in the region. We expect to plant more in the future (5 acres in 2010?)

Changing weather patterns shaped my decision to plant an acre of mixed citrus varietals in Santa Paula. Citrus is a little more tolerant of extreme temperatures than avocados, and I reason that they would fair better in a shifting climate. Additionally some varieties flower more than once a year, so a single weather event might not wipe out a full year’s income. Given the small volume of fruit that I will produce in this test block (9 varieties in one acre) it will all be distributed locally. Too ealry to see much result yet, although my first few Cara Cara navels and Star Ruby grapefruit have been delicious.

How about land reclamation?  The Santa Paula ranch has an acre of rocky spoils left over from some serious ripping they did on the ranch in the 1950’s. I have been covering this area with mulch and cover crop (OK, mostly weeds), and grazing goats on it. It will probably take five years, but I’ll get a new acre to plant for my troubles.

Thoughts that have not evolved to actions include solarizing the barn at the home ranch (enough roof space to run our irrgation well as part of a grid tied system) and a fig, pomegranate, and olive oil operation on leased land near Piru (very low water use crops which could be very compatible with the neighboring Santa Clara Riverbed.)

Covercrop Retrospective

We are coming up on the end of our first year of systematic cover-cropping at the home ranch. Overall, I’m pretty pleased with the results and expect to expand the acreage cover-cropped for the coming rainy season. What did we find?

 

Water-retention and infiltration: Despite fairly healthy rainfall this past winter, we had much less standing water and runoff than has been typical. Some of this result may be from the light disking that we did to incorporate a top dressing of manure and prep the ground for seeding. Still, we are happy with the result. Grade: A.

 

Erosion control: This typically isn’t much of an issue at the home ranch, since it is pretty flat. But a ditch that runs from our wellsite to the main drainage had suffered erosion in the past, so we covercropped it, paying particular attention to the area around the well’s discharge pipe. Results were fantastic. Not only was there no erosion, but all discharge water was captured with a 100 feet or so of the outlet. No well discharge water leaves the property anymore. Grade: A+

 

Soil Improvement: Too early to tell. The crimson clover that was part of the mix failed to take off, so we lost the benefit of nitrogen fixing and clover’s deep taproot. Possibly it just lost out to the very vigorous barley. We’ll try clover alone in these areas next year. Grade: Incomplete (But looking like a C)

 

Weed Suppression: We didn’t expect much benefit here, but were pleasantly surprised by the outcome. Mowing the covercrop has pretty much taken care of the weeds. No empirical data, but it seems that the amount of manhours and herbicide used in the covercropped area is down. Grade: A

 

Pest Control: While we hope that the covercrop is providing some beneficial insect habitat, we can’t say with any certainty that this is the case. But gophers and snails are abundant. Control of these two pests has been an issue. Grade: D