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Paul Underhill  |  Terra Firma Farm  |  Winters, CA

Subject: Cover crops -- decision time

So we're back in drought mode here in California with just a few inches of rain so far this winter in the Sacto area (about 40% of normal). We already had to irrigate our cover crops once back in December, and now they are running out of water again with zero rain on the horizon.

We've worked under a few fields that are going into early plantings, but I'm hesitant to do much more as the cover crops have not grown as much as I would like. But the soil is drying out quick! We're having quite a bit of wind, and that pulls moisture out the soil through the plants.

I'm wondering what others are doing about their cover crops. Are you irrigating again, or have you decided to plow everything under? Or a mix?

In Topics Soil Fertility Management

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Comments 6
02/13/18
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  |  High Ground Organics  |  Watsonville, CA commented

I think that gets at the question of whether or not we should be watering our cover crops in the middle of a drought. We are fortunate here on the coast in that we have gotten just enough rain to keep our cover crops going this year. But in the past four years we have certainly had to irrigate them and I always have major reservations doing so. Not only is it expensive--our wells are metered here and we pay an assessment--but I wonder if it is the responsible thing to do. We have a sizable overdraft here and the brutal part of these dry winters is that not only is the aquifer not being recharged, but all of the growers around here are pumping way more water than they normally would at this time of year.

02/14/18 10:42 AM
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  |  Terra Firma Farm  |  Winters, CA commented

Really interesting range of responses. And now we're expecting a widespread freeze next week, which means that anyone with cover crop under almonds or stone fruit should definitely mow AND irrigate.

Since we do straight vetch, I expect my cover crops to provide most of my nitrogen for the cash crop that follows -- i.e. we do not apply compost in addition to the cover crops. And most of the cover cropped fields aren't going into crops until mid-April, so I have plenty of time to do an irrigation and let them grow more. That would make this the 2nd or 3rd irrigation this year for the cover crop.

02/14/18 7:56 AM
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  |  Sikes Road  |  Dixon, CA commented

I am glad you brought up the topic of cover crop management. I am deciding if I should mow the cover crop in my orchard, and then irrigate – not deep, but enough for the cover. If I wait too long, the carbon-nitrogen ratio of the grass will go up too much, and deplete nitrogen instead of supply it. I hesitate because I like the cool season cover of grass and vetch to out compete the weedier summer grasses and forbs, and hate to start the summer vegetation cycle so soon. In the past I have flattened the cover with a ring-roller to attempt to crimp it and smother any growth. The crimping technique works fairly well, but I end up with a lot of residue at the end of the season and hopefully I will be harvesting my trees this year. Or should I just mow and let things dry for a couple of weeks until I need to give the trees an irrigation.

02/13/18 10:04 PM
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  |  verdi land  |  pacifca, CA commented

Failed to mention that the Favas I have planted were intended for seed for a future date.

I also should mention that I initiated an fall watering to attempt to irradiate the early weed bank...after which, the fava maintenance was less the hassle. With that, the early rains took care of things up until now. Could have gone another week but I also am on a slight dip to the south and get more sun than usual flat grounders. They are pushing 18-2ft tall at the moment but with this deep drink just given...gonna see some bursting ....and unfortunately the aphids are starting to make a statement. Bring on the lady bugs.

02/13/18 9:27 PM
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  |  Paul's Produce  |  Sonoma, CA commented

This is an interesting conversation and underscores the multitude of factors that influence these sort of decisions. If I were planting cover crop primarily for soil building and nutrient enhancement I can’t imagine not wanting to irrigate another time or two because it seems like a small cost for the return. I typically irrigate in the fall to get cover crops started as soon as I can unless rain is expected.

But on our small farm we compost (currently) before every crop (some exceptions). Our OM levels are typically 5%+ so I take out cover crops as soon as I can use the ground in the springtime. Some years it has been as late as early May, but we’re taking out cover crops now because we can use the ground for crops to sell. That’s the point right? We cover crop only the fields that I feel have been over-worked or prone to problems with winter growing. About 1/2 of my farm is unusable in the

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02/13/18 8:07 PM
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  |  verdi land  |  pacifca, CA commented

Hi Paul; don't know which cover crop/s you planted. Me.....I am in Favas. Planted them in manageable rows and am doing a very shallow cultivating to keep the earth from cracking(letting more moisture out) and yet bring 'up' the moisture for the plants by doing so. And so it goes for our geoengineered weather. The problem gets deeper though with the onset of early aphids. The lady bugs should have already been delivered to the post office for the first application. After this week, it will definitely have to get watered though. Been forcing a deep tap root thus far but don't want to push my luck for another round of hot dry wind, even though I am coastal.

02/13/18 10:49 AM

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