114 Benefits of Crop Rotation. Working with Clay Soil.

Show Transcript

GB114 TRANSCRIPT Crop Rotation. Clay Soils.

28:48

SPEAKERS

Debbie Flower, Steve Zien, Farmer Fred

Farmer Fred  00:00

Garden Basics with Farmer Fred is brought to you by Smart Pots, the original lightweight, long lasting fabric plant container. it's made in the USA. Visit SmartPots.com slash Fred for more information and a special discount, that's SmartPots.com/Fred. 

Farmer Fred  00:20

Welcome to the Garden Basics with Farmer Fred podcast. If you're just a beginning gardener or you want good gardening information, you've come to the right spot. 

Farmer Fred  00:32

Crop rotation it's not just for farmers .Backyard gardeners can improve their food and flower production while improving their soil at the same time, simply by moving plant families from bed to bed each season. College horticulture Professor (retired) Debbie Flower has the lowdown on the advantages of crop rotation. If your clay soil has you worried that it's not very good for a garden, well, worry no more. Soil specialist Steve Zien says there's a lot of benefits to gardening with clay soil, and he has tips for improving it as well. It's all on Episode 114 of the Garden Basics with Farmer Fred podcast, brought to you today by Smart Pots. And we'll do it all in under 30 minutes. Let's go. 

Farmer Fred  01:20

Sometimes when it comes to garden problems, one thing that helps a lot to keep them from spreading is crop rotation. We've talked about this a lot on the program. What exactly is crop rotation? For the answer to that, we bring in retired college horticultural Professor Debbie Flower, who has probably discussed this with one or two classes in her time. 

Debbie Flower  01:39

Yeah, yeah. 

Farmer Fred  01:41

And I think I recall you saying that, when the crop rotation lecture starts, their eyes glaze over.

Debbie Flower  01:49

Boy, I hope not. I hope that it's used. We talked about it, not just in the vegetable garden, but also in the landscape when planning a landscape. So what it is, is for the vegetable garden, is planting something different in each spot each year. So one year you plant tomatoes there, and then the next year, you're going to plant something different maybe cabbage, or that would not be a summer crop, but mustards that spring. Or maybe you leave it blank, but you don't plant tomato or a tomato relative in that same spot the next year. So crop rotation is done at the family level. Plants in the same family share insect and disease problems. So if you get a tomato one year, and you plant a tomato the next year in the same location, or a pepper, or an eggplant, because they are all in the same family, or a potato or a potato, yes, if you plant them in the same location the next year, maybe you'll do okay. But then maybe the third year, the disease pressure has built up enough or your tomato hornworm population has built up and they spend their winters in the soil. And so you plant a plant in the same family, they'll come out and start eating the plant. Whereas if you rotate it to something outside (the family), let's say a melon, outside the it's called the Solanaceae family so the Solanaceae family has tomatoes, potatoes, peppers and eggplant as well as tobacco, which is a fun crop to grow as well. It's pretty, I think. If you plant any of those things, you want to not plant them the next year, they're  all in one family, so you want to move them somewhere else. So maybe we're gonna move to the family that the cucurbits which includes cucumbers and melons, and squash and plant one of those in that spot instead, with when the tomato hornworm comes out in spring, and there's a squash there, it's not going to do anything, it does not attack the cucurbits, it only attacks the Solanaceae family. So we're moving our plants around the garden so that the insects and diseases that may be present at that one location, don't attack the plants from a different family.

Farmer Fred  04:13

Probably ideally, it's nice to have six distinct garden planting areas. Because this makes the garden rotation plan, the crop rotation plan, a lot easier. We'll have a link to today's show at the Farmer Fred Rant and it'll be called the "Crop rotation plan for the home garden." So basically, let's say you have six beds in this perfect world you live in. One bed is going to be blank, but actually blank isn't blank, because you could put a cover crop in there. You could put oak leaves on there. You could just put compost on there. You're basically giving that plant the season off to feed the soil.

Debbie Flower  04:49

That bed.

Farmer Fred  04:50

Yeah that bed (not plant). One bed  would be the sleeping bed, if you will, then the next bed over would have your Solanaceae: the tomatoes, the peppers, the eggplants, the potatoes. Bed three has onions, garlic, beets, carrots, which family is that?

Debbie Flower  05:12

I think that's what the alliums would be. That's their genus, not their family.

Farmer Fred  05:17

Right? Yeah, the Amyrllidaceae, I think, is the term for that. For the chives, garlic, leeks and onions. The fourth bed are for the legume fixing crops like peas and beans.

Debbie Flower  05:29

Legume fixing meaning that they're able to collect nitrogen from the atmosphere and put it into their nodules on their roots, if you leave those roots, they will release that nitrogen for the next crop.

Farmer Fred  05:41

There's a little trick to that when you talk about nitrogen fixing crops. You cannot allow those plants to flower. It's taking that nitrogen that it just stored and using it to produce flowers and seed, right. So  that's sad but...

Debbie Flower  05:57

Well, some of those  we don't want them to flower. Some of them we do, if we want to get the crop. Yeah to get the beans or peas we've got to let them flower Yeah.

Farmer Fred  06:08

But then again in that bed for you could plant something that works both as a cover crop and as something you could eat like fava beans, for example. If you want to do a cover crop so yeah, in bed five, you've got the Cucurbits. Yes, the cucumber is muskmelons, pumpkin, squash, watermelons, which are, I would think heavy nitrogen feeders.

Debbie Flower  06:36

Yes, they are heavy nitrogen feeders.

Farmer Fred  06:38

And then you've got a lot of the winter crops, the cool season crops, in bed six. You've got the cabbage, the lettuce, the spinach, the radishes, the turnips, the broccoli, brussel sprouts, kale, cauliflower, mustard. And when that's done, that would become, I would think, the squash, pumpkin bed (in the summer) because  they're (the cool season crops) not heavy nitrogen feeders, those cool season crops.

Debbie Flower  06:59

Right. So that all sounds confusing, maybe. So go to Fred's crop rotation rant, and you'll see an image of a pie garden, a round garden. It's cut into six parts and it suggests what crop to put in each of the six parts. Then the following year, you rotate that circle. What was bed one becomes bed six, what was bed two becomes bed one, etc. and the year after that you rotated again, we aren't all so blessed. I am not to have that much garden space, six places. But I will say I do pay attention to where my tomatoes are, in particular, my Solanaceae crops and where my squashes were, and I will move things around. Again, Fred has often talked about keeping records and writing it down is a good thing to do. So this year, I planted the tomatoes in this bed and I planted the squash over here and I planted the beans over here. And then I just can look at that next year and do a rotation. If I can avoid planting the same thing in the same spot for the next year. That's great. If I can do it a third year that's even better. But sometimes I actually revert to pots. If I don't, I've run out of space I grew a lot of one thing let's say tomatoes one year, or I had tomatoes, eggplants and peppers all over the place. Then I will revert to pots and put some stuff in pots, the tomatoes, eggplants, peppers, large pots, nice container media. You regularly irrigate and they'll do well and but that gets them out of the ground for one year and allows any of those pests that are in the ground there to to die off because they don't have their food supply.

Farmer Fred  08:41

I would think being thrifty with potting soil might work against you if you're planting tomatoes over and over in pots. So I would imagine you want to use fresh soil every time.

Debbie Flower  08:53

either fresh soil or soil that came out of a pot and sat for a while a pot of something else and sat for a while.

Farmer Fred  09:01

Would that kill off those disease causing organisms like verticillium?

Debbie Flower  09:07

Well, fungus and bacteria are difficult to kill off. You'd have to solarize them or steam treat the media.

Farmer Fred  09:15

Can you do that in the oven?

Debbie Flower  09:16

You can but it stinks. And it's a slow process.

Farmer Fred  09:20

What I noticed one thing about the crop rotation garden if you will, that if you imagine your garden as a pizza pie, that directly opposite in the six slices of garden pizza, the 12 o'clock and six o'clock positions  are both heavy nitrogen feeders, the tomato pepper, okra, potato eggplant at 12 o'clock and then squash pumpkins melons, cucumbers corn at six o'clock and if you're rotating it clockwise, replacing the tomatoes, peppers, etc would be the cover crop or the composted slice. Replacing the corn, cucumbers, squash and melons are peas and beans, which is a nitrogen fixing crop.

Debbie Flower  10:02

Yes. And even though they do need to flower and they do use some of that nitrogen they fixed, there typically is some nitrogen in their roots leftover at the end of the crop. And so if you leave their roots, then you've you've got nitrogen for the other plants to feed off of.

Farmer Fred  10:16

Yeah, so you're basically surrounding the heavy feeders with lighter feeders or replenishers. So, if you go to the crop rotation plan for the home garden at the Farmer Fred Rant blog page, it makes it much easier to understand than trying to figure this out in a podcast.

Debbie Flower  10:30

But there are reasons why each triangle on that has a certain plant in it.

Farmer Fred  10:36

Right? Exactly. You can't unfortunately mix up your plants without spreading the disease to every bed. By the way, that brings up another good point, too. When you go out to the garden, you've got your trowel and you're digging in every bed. Well, if you happen to be digging in a bed where you know you have a disease issue like verticillium or Fusarium,  don't forget to clean off that tool before you go to the next bed.

Debbie Flower  11:02

Yeah, they exist in the soil. And hopefully you don't have them. If you do, then you have to pay attention and use verticillium or fusarium resistant plants, or grow them so that that disease doesn't take over. But you can move it from place to place if you use a dirty tool in a new place.

Farmer Fred  11:23

So know your families.

Debbie Flower  11:25

Know your family or your plant families.

Farmer Fred  11:26

Yes, exactly. And at the Farmer Fred rant blog page, that crop rotation plan delineates that so you know, who's related to whom, and who you want to move together. There are some other families too, that are heavy feeders that are more permanent, and you don't really have to worry about those like asparagus, or artichokes, if you can grow artichokes where you live. And those are going to get their own bed for 15-20 years.

Debbie Flower  11:53

And you're going to attend to them differently. Exactly.

Farmer Fred  11:57

Yeah, and like you say, it's always a good idea to have some big pots on hand, too. Yes. And get your three bags of media. Yep, yep. And clean your tools. Crop rotation. It's done to avoid buildup of pests, both diseases and insects. So get in the habit of rotating your crops. Debbie Flower, Thanks for your help on this.

Debbie Flower  12:17

Always a pleasure. You're welcome.

Farmer Fred  12:23

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Farmer Fred  13:22

No matter where you live, you might be dealing with clay soil. Many gardeners don't like clay soil because it's too hard to dig or maybe it's always wet. Well actually clay soil does have some advantages and clay soil can be modified. We're talking with Steve Zien, a soil pathologist for over four decades. And Steve, you've heard it, I've heard it over the years, people think they have a poor garden because they have clay soil. When in reality, it could be just poor drainage.

Steve Zien  13:55

I love clay soils, clay soils have have numerous beneficial features to them. The problem is they have not been managed properly. Clay soils don't need to be irrigated as frequently so they don't need as much water. They will hold water for a much longer time so that your plants will be less likely to have problems with drought. You need to irrigate less frequently, although when you're irrigate, you do have to apply it much more slowly than you do, say, a loam soil or a sandy soil. The water will will move down and actually spread out farther if you're using, for example, a drip irrigation system. You don't need to have as many lines and you can have more space between your emitters in a clay soil than a sandier soil or a loam soil.

Farmer Fred  14:47

Yeah, exactly. Let's talk a little bit about that water footprint if you will, and let's use for an example a drip irrigation system with drippers, and as that water drips into the soil if you have clay soil, that footprint could be 12 to 18 inches wide. Whereas with sandier soils, it could be 10 inches or less. 

Steve Zien  15:10

Probably less. The issue is that when you're applying it in a sandy soil, it'll move straight down pretty much, very, very rapidly. And so you can apply the water fairly rapidly, and it won't run off. And it'll get down to that depth, but it won't spread out. So you need to put your drip lines closer together than in a clay soil. The water, the pore space, the size of the pores is much smaller. Water does not move through clay soils, via gravity. It moves through by what's called capillary action, the water actually has to be sucked into and through the soil. And so it moves much more slowly. But it will also, because it's moving, you know, by suction, if you will, it's going to be stuck to the sides. And so it's going to spread out much, much farther.

Farmer Fred  16:02

But don't you want water to go deeper. So how can you make clay soils absorb the water, so it goes deeper,

Steve Zien  16:09

Just apply for a longer period of time, it's very easy. I've heard numerous people say you can't use drip irrigation systems because you can't get the water down deep enough. And that simply is not true. You just have to leave them on for a longer period of time. And really the best way to to test how far that water is, is going down. And how far out it's going for that matter is to use what's called a soil probe. It's basically like a hollow tube that has a tee on the top, and you push it on the ground and you pull it out. And there's one side that's open that you can see the soil that you pull out, and you'll be able to see whether that soil is moist or dry. And so what I tell people to do is irrigate half the amount of time they normally do, wait an hour, so that gravity is going to pull that in the water as far as it's gonna go. And gravity does have a little bit of a factor can have a little bit of effect in a clay soil, especially if it's a healthy clay soil. And then after an hour, you put the the soil probe back into the soil, pull it out, and you'll see how far down that water's gone. And if it's gone down six inches and you want it to go down a foot, you've got to water twice as long, it's just a matter of realizing with a drip system to get water down deep, you have to let it run for a much longer period of time.

Farmer Fred   17:34

One of the problems of drainage and clay soil is underneath that clay soil which may only be 8-10-12 inches thick, is underneath that there could be some layers of hard pan, which are going to inhibit the flow of water. And I think that may be a case that a lot of people are encountering when they're trying to work with clay soil.

Steve Zien  17:57

Yeah, that can be a real problem. If the clay hardpan is relatively shallow, where you can get a drill basically, and drill through it. A lot of times you can go to your Cooperative Extension office or your agricultural commissioner's office and ask for a soil map. There's also websites that give you soil maps, but but some of the newer ones, if you live in an urban area, are not quite as accurate, because they can't get in there to sample the areas because it's somebody's backyard. But they will, in many cases, give you an indication of the depth of the hard pan, if you have one, and how thick it is. And if you can get a drill bit to go down and if it's not very thick, in many cases, it's not you can just basically drill through it. And then you want to take a mixture of sand and organic matter, compost, and fill that hole with the sand and good quality compost or earthworm castings that will help to get that stuff to drain better. And then you're also going to get biology down there as well because a good quality compost as a lot of soil biology that well more rapidly caused the hard pan to break up if you will. Another thing you can do is there are some cover crops or green manures that are very, very deep rooted and capable, in many cases, breaking through clay hard pan.

Farmer Fred  19:36

and if you live out in the country, always keep the phone number handy of the guy that's got a tractor mounted or Jeep mounted soil auger that can easily get down 36 inches with with no problem. When I lived in the country. That guy was very important in my life to drilling those holes to get through those layers of hard pan So if you want to improve clay soil, Steve, what would be a good way to make sure to help that water go even deeper?

Steve Zien  20:08

Well, if you've got clay hardpan, that's your issue. One technique is to basically drill a hole of roughly an inch, inch and a half in diameter through that hard pan. And then you insert into that hard pan quality compost and sand, roughly 70%, compost, and 30% sand into that hole. And that will allow water to move down through that hard pan. And you've got to take that mix of compost and sand all the way to the soil surface. Because you need to get that water into that mix of compost and sand. At the soil surface, if you put it below the soil surface, it's not going to get into that column very well, the soil will have to be saturated in order for the water to move into that column. So and so we're only talking about an inch an inch and a half in diameter. And you know, do them a couple feet apart. And you will be then getting this soil biology threw that hard pan and in that area of that hard pan and they can start breaking up in our path and then you can also start growing crops that will have deep tap roots that will go through those holes. And then as they grow they will fracture the hard pan. And this is,  we're talking about amending. We're really talking about breaking up the hard pan, we are not talking about improving drainage if you will, to your clay soil in order to do that, what you want to do is surface apply good quality compost and earthworm castings. And with rain and irrigation and some soil biology that might be native to the to the soil to your clay soil and certainly the soil biology that is in the compost and the earthworm castings will start penetrating into that clay soil and creating soil structure creating different sized pore spaces, which will then improve the drainage, improve the ability of you to dig in your soil, to plant and transplant and fertilize and all of those good things just apply to the soil surface. Realize that every time you cultivate the soil you dig in the soil you rototill  the soil, you're destroying not only soil biology that helps your plants obtain nutrients, water and fight off pests, but it destroys the soil structure, the different sized pore spaces that you have, which is so critical. In a clay soil, your typical clay soil only has small pore spaces. And that's why the water and roots have a hard time moving through it. You need those large pore spaces created by the soil biology.

Farmer Fred  23:09

You have heard and I have heard over the years some interesting ways that people have dealt with clay soil, especially when it comes to irrigating trees or shrubs. And I once visited a gardener who had all these PVC pipes sticking out of his soil and he explained to me that it was too deep water his trees and these one inch PVC pipes would surround the tree. There are probably eight or 12 of them around each tree that went down three feet. And he was basically going out there every day putting his garden hose in each of those pipes and filling those pipes with water. Is that gonna work? 

Steve Zien  23:46

No. The issue is what if he's doing it every day. He's basically saturating that soil in the vicinity of those  PVC pipes,  our plant roots, and all the soil biology, need oxygen as much as they need water. And so if he's doing that every day he is eliminating the oxygen. The only kind of critters that are going to live in that area are the kinds of critters that rot plant roots. The other issue is if he doesn't have enough of those pipes, the soil probably between those pipes is bone dry. And so then you get a very poorly spread root system. And so it makes it much more difficult for that tree to obtain nutrients and water because the entire area where the roots should be growing is limited by half or maybe even more.

Farmer Fred  24:43

The other story we hear from a lot of gardeners dealing with clay soil is they think they can improve the drainage by rototilling in lots of sand. What does sand do in a clay soil?

Steve Zien  24:56

Well why do building contractors use sand and clay? They may become concrete or cement. And so I always tell gardeners if you want to garden in concrete or cement, go ahead and add sand to your clay soil. I had one person who said, Well, I  added sand to my clay soil and it works. It worked great. And I said, Well, what did you actually add? And he then admitted, he added sand and a little bit of sand to a lot of compost. And so it wasn't the sand it was  the amount of compost that he added, and the soil biology like I said before, when you cultivate your soil when you do anything that digs into the soil, whether it be rototilling, or spading, or double digging, or however you cultivate the soil, you're destroying the soil structure, you're destroying the the large pore spaces that are there that are so critical for water movement, root movement biology movement, you're also destroying roughly half, if not more, of the soil biology. A lot of the soil biology, fungi and michoraezal fungi have long roots. And so you're chopping those things up and you're killing them. And so you're ending up with a soil that is dominated by these little tiny one celled organisms called bacteria. And when you get a soil dominated by bacteria, instead of having a roughly 50-50 ratio of bacteria to fungi. If you've got a bacterial dominated soil, the kinds of plants that like to grow, there are weeds. Weeds love bacterial dominated soils. So if you want to grow a lot of weeds in your garden, till it up. If you want to destroy the soil structure, end up compacting your soi,l making it that much harder, till the soil. If you want to improve the quality of your clay soil, start adding compost and worm castings to the soil surface.

Farmer Fred  27:02

Clay soil. It it can be your friend if you learn to work with it right. Steve Zien has provided us with a lot of tips to do that. I'll throw in one of my own tips. If you have clay soil, get a spading fork. It's much easier to dig with a spading fork than it is with a shovel into clay soil. Thank you. 

Steve Zien  27:20

Or a broad fork? 

Farmer Fred  27:21

A broad fork. Yeah, how broad is a broad fork?

Steve Zien  27:26

My guess is about three feet long and about an inch wide and it has tines just along that one row. And the tines are fairly long. And you basically just shove it into the ground and it has long handles. And you just basically you put your foot on the crossbar and you grab those long handles and you move forward and back, forward and back. And you're just basically fracturing, trying to fracture that clay soil. And then you can put your  compost on the soil surface, your earthworm castings.

Farmer Fred  28:02

There you go. Lots of advice from Steve Zien, soil pathologist, also unofficially Sacramento's organic advocate, as you might be able to tell. And we've got some good advice there on working with clay soil. Steve, thanks so much for your help.

Steve Zien  28:17

It's been fun as always, Fred.

Farmer Fred  28:21

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