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Heavy Rain Means New Challenges for California Farmers

The drought may be easing, but that doesn’t mean hardships are over for California’s farmers. Instead, flooding caused by weeks of wet weather creates a different set of risks for growers, explains agronomist Karen Lowell.

Written by Matt Weiser Published on Read time Approx. 6 minutes
A field worker digs a trench to drain flooding from recent rains in a field of young seedlings in rural Salinas, Calif., on Feb. 24, 2017. This is part of the hard work of dealing with winter conditions that can be too wet for farming.David Royal, Monterey Herald via AP

After five years of drought, Californians are elated by the return to wet weather across the state. But it isn’t all good news for the state’s farmers.

Rains have been so heavy that many farm fields are deeply saturated, if not flooded entirely. This creates a variety of problems. Mud may be so thick that tractors built for mud might get stuck. Even if they can move, they might damage the ground or the roots of permanent crops underneath. This spirals into planting delays, which can have economic repercussions later.

Persistent wet conditions also create fungus problems and may prove inviting for insect pests.

To help understand this latest set of challenges facing California farmers, Water Deeply spoke with Karen Lowell, an agronomist with the U.S. Department of Agriculture’s Natural Resources Conservation Service, based in Salinas.

Water Deeply: What kinds of unique challenges are farmers facing this year because of all the rain?

Karen Lowell: I would say one of the first things they’re going to need to do is sort of assess where they are in terms of maintenance. In some cases, there’s been some damage to farm roads or small bridges, things like that. That’s universal.

A lot of operations have ditches and drainage structures, and sediment basins to capture anything that does come off the ground. And that’s all going to require some maintenance – in some cases, significant maintenance.

Water Deeply: Will we see delays in planting because of wet conditions?

Lowell: A huge issue is scheduling operations. For example, we often talk about the benefits of cover crops as a way to protect the soil from erosion and also to capture any nutrients left in the ground at the end of the season, in the fall. Also to benefit soil health. By keeping a living root in the soil, it will help water infiltrate and not pond on the soil.

But in a year like this, the problem that often makes people hesitant to plant cover crops is very apparent. They’re planted in the fall, and then you want to terminate that cover crop. Typically it’s mowed and incorporated in the ground. You want to kill that cover crop at a particular stage of growth.

When we have a super wet year like this, in which the rains don’t really give us a chance to let the ground dry out, what can happen is the farmer can’t get on the field to terminate that crop because it’s too wet. So the cover crop gets more mature and woodier than is ideal. And it continues to generate more biomass. If you can’t get on the ground to terminate that crop, that’s going to be a problem. They can’t plant their seed or seedlings until that ground is worked up and ready for it.


In this view looking north on Feb. 18, 2017, storm runoff has flooded Interstate 5 near Williams, Calif., as well as hundreds of acres of farmland on either side of the highway. Saturated ground can delay a variety of field preparation steps that are necessary before crops can be planted. (Randy Pench, Sacramento Bee, via AP)

Water Deeply: What else happens when the ground is too wet?

Lowell: For the same reasons the ground’s too wet, sometimes there are many disease issues – often fungal issues – that are more problematic in a wet year. It’s typical, for example in almonds, to get in and spray for those fungal problems. But if the ground is too wet, you can’t get on the ground to spray your control agents as you would like to. So again, your planting date may get pushed around.

One of the major issues that can arise is disease and pest pressure may shift. For example, in almonds there are some diseases that really take off when there’s moisture during the bloom season. One of them is called shot hole fungus. Crop advisers have noted that one is also quite a bit more prevalent in a wet year.

Then over here on the coast we have a lot of leafy greens and berry crops. There are some soil-borne diseases and rot diseases that may be more problematic in a wet year. I haven’t yet seen data specifically on that. But it shouldn’t be surprising if there is an increase in problems with wet soils and some of these rot diseases that occur.

Water Deeply: What about scheduling on the other end? Does it create problems harvesting a crop?

Lowell: It depends on the crop. For some crops it could. For some it just means you plant late and you harvest late.

It’s not just that the soil is wet and you can’t take your equipment out. It also changes the ability to create the soil conditions you need for optimum early growth of that crop.

Water Deeply: What do you mean about managing soil conditions?

Lowell: In a wet year, it’s kind of a double-edged sword. After a wet winter, you have to assume your soluble nutrients have likely leached to a far greater extent than in a drier year.

You’re going to want to check your plant nutrition status – things like nitrogen – pretty routinely and regularly in the growing season to make sure you’ve got the nutrition that you think you’ve got.

If there’s a heavy rainfall, those nutrients will move down in the soil profile. Deeper-rooted crops like orchards and vineyards may be able to catch those nutrients. But even the deeper-rooted crops have the majority of their feeder roots close to the surface.

The flip side is that for areas that have had some accumulation of salts, a good leaching year can be helpful, provided you have good drainage and you’re able to flush those salts out. You may actually see some benefit in soils that had started to accumulate some salt. If you don’t have decent drainage, then those salts are just going to be pushed deeper in the profile, which is not as beneficial.

Obviously, the good news is that when you’re pushing water down, you’re pushing water down to the groundwater storage and also in the soil profile. The soil has the capacity to store a tremendous amount of water. So those crops may not need as early a supplemental irrigation if they’re able to find moisture in that soil profile. That may be a benefit in terms of water management this year.

Water Deeply: Are there any challenges with fields that may have been fallowed because of the drought?

Lowell: If they’ve managed weeds on it, that may be a different scenario than if it’s been allowed to just grow out with whatever volunteers go to seed. If those are weed species, that may present some management challenges. For example, if you’ve left a field for two years and it’s been proliferating with weed species, there’s a good likelihood you’ve got a heck of a weed seed bank built up. So you’re going to have to control those more aggressively than you would have.

Giving the ground a rest is a good plan in general. You just want to think about what happens during that rest. Cover crops still protect the ground even if you let it dry and die in the field. There’s data to show amazing benefits of even a small amount of cover crop in terms of protecting the structure of the surface and allowing whatever rain comes to infiltrate. If you compare orchards with and without a cover crop, you’ll see some pretty amazing differences. The same amount of rain has fallen, but generally where there’s a cover crop that rain gets into the soil better.

Water Deeply: So, are we likely to see farming bounce back from the drought this year, or are these new challenges too great?

Lowell: One of the things our agency has tried to help people think about is that this isn’t going to be the only bounceback that’s necessary. Farmers are amazingly resilient. And the reality is, they’ve dealt with these changes before.

In the big picture, we all know that drought isn’t good. But from an operational standpoint, these guys operate on incredibly tight market demands. They know they have to get a crop in the ground and to market in a specific window in order to get the cropping cycle they need to make that ground profitable for them in a given year.

Managing agricultural production is kind of like a giant puzzle. Everything they do, they’ve got to be thinking it’s going to cost them something, and is it worth that cost? I wish people had a greater respect for what these folks do getting all these incredibly good-looking crops to market, because I don’t think in general people understand how hard it is.

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