Soil Management Practices for Your Farm or Garden
What does a sustainable and resilient farm look like? Farms with a Future (Chelsea Green, 2012), by Rebecca Thistlethwaite, introduces readers to some of the country’s most innovative farmers who are embracing the entrepreneurialism of farming. This excerpt, which provides some information on maintaining the best soil for farming and gardening, is from Chapter 7, “Soil and Water Management.”
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The bank account that supports your entire farming operation is your soil bank. Despite the foundational importance of the soil, you would be surprised by how little it is attended to by farmers and ranchers around the globe. The way we treat our soil is akin to the way we abuse credit cards. We overspend beyond our means, the debt grows larger, and we can barely afford to make the interest payments, let alone make a dent in the principal. With our soil we continue to take, take, take away the principal nutrients, and our meager supplements of fertilizers do almost nothing to stem that loss. Even though organic farms are supposed to write up and enact a soil management plan, I have seen many of them imitate the same poor practices as nonorganic farmers who aren’t required to write a plan. Too many of us act as though topsoil is a renewable resource—it is not.
What are some of the inferior soil management practices that persist to make farms unsustainable, and how do we restore soil health? Much of this section is drawn from the fabulous and thorough publication Sustainable Soil Management Guide, published by Appropriate Technology Transfer for Rural Areas (ATTRA), also known as the National Sustainable Agriculture Information Service. Here are what too many of us farmers and ranchers are doing wrong:
1. Compaction is rampant. In the quest to get crops in when the soil is too moist, we cause tremendous compaction. In our quest to mechanize everything, we cause compaction. When we use the same implement that reaches to the same depth or flips the soil in the same way, we cause compaction. Unless you are farming or ranching on “virgin” soil, you might as well assume that you have soil compaction. Now what?
• Rotate your crops, especially between shallow-, medium-, and deep-rooting crops. For example, lettuce and strawberries are shallow rooted, while grains are deep rooted.
• Plant mixed pastures with grasses, legumes, and broad-leaved plants. Their diverse rooting structures will help open up the soil. Also throw in some perennials that develop really deep-rooting structures. This works great in strips between tree crops, too.
• Rent or borrow a deep ripper every few years. You don’t have to own it, nor should you come to rely on deep ripping. Yet it can redress serious compaction, particularly deep hardpans.
• Don’t plow to the same depth every time, and use different implements when you do plow. For example, relying on only a rototiller that plows to a similar depth every time is a sure cause of compacted hardpan.
• Rotate annuals with perennials, such as vegetable crops with pasture or hay crops. A nice rotation I have seen is two years of vegetable crops followed by three years of pasture. The rooting structure of the pasture plants not only opens up the soil but can also pull up deep nutrients and add significant organic matter.
• Test your soil’s moisture content before you bring equipment into the field. Dig up some soil, and squeeze it in your hand. If the soil drips water or holds together like a lump of clay, it is too wet to cultivate.
• Think about how you might be able to extend your season without resorting to working your fields when they are wet. For example, could you start crops as transplants in a greenhouse for a month or two before you set them out in the field? This holds true for livestock as well. Could you have dry shelter for your animals during the rainy seasons so that they aren’t trampling all over your fields when the soils are wet and saturated?
• Watch your irrigation so you aren’t oversaturating your soils, which could lead to compaction.
• Building soil microbiology and organic matter, correcting pH, and achieving a proper calcium-to-magnesium ratio will all contribute to better-aerated, better-draining soils that are more resistant to compaction.
• Even incessant foot traffic during the rainy season can cause compaction. Enter the fields as infrequently as possible when it is wet.
2. Very few farmers seem to be adding enough organic matter. Are you feeding the soil, or just the current crop growing in the ground? As an organic or sustainable farmer, you should set your focus on feeding the soil. Otherwise, all you are doing is following the conventional model of applying externally produced, simple plant nutrients, just enough (or sometimes way more than you need) to get a salable crop. But how can you actually improve soil organic matter over time?
• Leave behind crop residues, flail-mow them if possible, then reincorporate back into the soil. Or let your livestock out to consume the residues in situ and deposit their rich manure in its place.
• Rotate with cover crops or green manures. Try to get in at least one season of cover crops every other year, if not every year.
• Spread biologically active, high-quality compost on your fields once every one to two years. It does not pay to buy cheap, mostly carbonaceous municipal composts. Shop around; ask for the company’s most recent compost tests and references of other farmers who have used their compost. Call a reference or two and ask for honest feedback on the compost quality. Applying a good load of compost can be expensive—make sure it is worth your money.
• Use plant-based mulches, such as leaves, straw, wheat hulls, or wood chips, on the beds or in the walkways. Find out what locally available mulch materials may exist in your region: In some places that might be nut hulls, while other places might have oat or barley hulls. Ask around—you may be surprised what organic waste materials you can find. This organic matter will break down slowly over time and feed your soil microorganisms. However, be careful not to add too much carbonaceous material right near the growing plant, as it can tie up nitrogen and stunt the plant’s growth.
• Rotate livestock into your system, but be careful not to overgraze. Remember that root growth mimics aboveground plant growth. If you want a lot of root growth and decay (and hence organic matter), don’t graze the plants below a healthy level and let them periodically grow much taller.
• Get your soil tested every one to two years. Strive to make your organic matter percentage go up incrementally over time. Make a goal of attaining something like 70 percent of the native soil organic matter (SOM) level for your region. For example, if the native grasslands where you farm have a SOM level of 8 percent, your goal level should be 5.6 percent, which would represent 70 percent of native levels.
• Organic matter will be useless if your soil is biologically inactive. By adding organic matter and biologically active composts, you will be feeding the microorganisms that live in your soil and helping them proliferate. There may be bacterial and fungal inoculants out there that can help, too, although many have not really been proven to do much other than cost you money. Your money will be better spent on making or buying good compost if you want to simultaneously bring in more beneficial microorganisms and feed your existing populations in the soil. No soil is completely devoid of microbial life, but some may need some outside assistance.
3. Soil testing happens too infrequently, or is done improperly, or is not conducted at all. What is $80 or $100 a year in the grand scheme of your farm budget? Why don’t you make soil testing a regular thing you do each year? There are so many fascinating parts to a soil test that I can’t go into them all. A great book that lays it all out is Neal Kinsey’s Hands-On Agronomy, which draws heavily from the Albrecht/Reams method. Here are some tricks to making the most of your soil test:
• Use a reputable testing lab (not a fertilizer company), then stick with them over time. If you bounce around using different labs each time, you will get very different results, making it hard to compare your soil’s chemical properties over time. If you are an organic farmer, try to find a lab that has expertise in organics.
• Don’t take soil samples when your soil is too wet, frozen, or parched dry. Take a sample each year at around the same time, ideally two to three months before you plant your crop so you have time to review the results and add some of the recommended amendments.
• When taking your soil samples, follow the protocol described by the testing lab. Usually, this involves randomly selecting 10 spots around your field (I like to throw a bright yellow tennis ball around so I can see where it lands), peel off the top grassy/weedy layer, then dig your clean trowel 7 inches down and pull up a slice. Thoroughly mix those 10 samples together, and send 1 cup of that mixture in a paper sack to the lab immediately. Don’t keep the soil in your truck, baking in the sun, for several days before you send it. That will change the results! If you are planting deeper-rooting crops such as trees, you might want to take a separate soil sample at a much greater depth. Above all, follow the sampling directions that the lab gives you.
• Read the lab results thoroughly, especially their recommendations, then have another farmer mentor/friend of yours have a look, too, as a sort of second opinion. Early on in your farming career, this might be where you could bring in a soils consultant to help interpret your results and make recommendations. This is money well spent.
4. Not addressing major mineral imbalances (such as calcium-to-magnesium ratios) or pH problems. It always amazes me how commercial farmers, both big and small, neglect the mineral content of their soils. Sure, they probably give some sort of nitrogen-phosphorus-potash (NPK) shot to their crops, but much of that is taken up in the crop. What about the other major and minor minerals that are necessary not only for plant growth but also to support diverse microbial populations and organic matter decomposition? Likewise, I see farmers killing themselves to get a crop out of dense, sticky, saturated soils that probably don’t have the right cal:mag ratio or the right pH (which affects hydrogen and oxygen exchange and hence aeration). How can you address the chemical properties of your soil in a way that doesn’t break the bank or your back?
• Start off, before you do anything else, with a soil test.
• Observe the soils: how they drain or pool water; whether they crack or swell.
• Feel the soil, and squeeze it through your fingers. Notice the soil texture and color. Dr. Ray Weil, a soil scientist at the University of Maryland, describes how he would make a quick evaluation of a soil’s health in just five minutes: “Look at the surface and see if it is crusted, which tells something about tillage practices used, organic matter, and structure. Pushing a soil probe down to 12 inches, lift out some soil and feel its texture. If a plowpan (hardpan) were present, it would have been felt with the probe. Turn over a shovelful of soil to look for earthworms, and smell for actinomycetes (white fungal ‘roots’), which are microorganisms that help compost and stabilize decaying organic matter. Their activity leaves a fresh earthy smell in the soil.”
• Add major minerals via compost, cover crops, aged manures, even livestock in rotation. If your livestock are fed the minerals that your soil is missing through their feed or a mineral block, they will help spread those minerals out onto your fields. Other decent sources (especially if locally available and renewable) are kelp/seaweed, fish emulsion, compost or manure teas, and blood, bone, or feather meals. In my opinion, formulated fertilizers (even organically approved ones) are my least favorite source of nutrients: they are expensive, energy intensive, and often too soluble and “fast-acting” as sources of nutrients, and do little or nothing to address soil mineral imbalances. They feed the plant and not the soil, don’t provide soil organic matter, don’t increase soil microbiology, and can sometimes lead to nutrient pollution via leaching.
• Learn how to do a basic nutrient budget for the three major nutrients of nitrogen, phosphorus, and potassium to calculate your fertility needs. Here is an example of nutrient budgeting for nitrogen:
Lettuce needs 100 to 120 pounds of nitrogen per acre to produce a decent crop according to UC–Davis Extension bulletins. Let’s pick 110 pounds per acre as the target average. Your soil test indicates that 25 pounds of nitrate nitrogen (NO3) is available in the soil (although nitrate nitrogen is very dynamic and can leach out before you even plant your crop, so this number may not be that accurate). Your water test indicates that 50 pounds of nitrate nitrogen (NO3) will be available over the course of irrigating the lettuce to harvest.
So if 110 pounds of nitrogen is desired:
25 pounds nitrogen present in soil, plus
50 pounds nitrogen present in water
equals 75 pounds of nitrogen that is available
Which means you will need to add 35 pounds of nitrogen per acre.
If you hadn’t done this budget, you might have added 110 pounds of nitrogen per acre when you only needed to add 35 pounds. Knowing this is important for nutrient management and cost containment and is also a water-quality issue that I will discuss further along in this chapter.
5. Soil erosion beyond what our soils can naturally regenerate. To me this is truly the most egregious thing we could be doing to our soils. Soil erosion created the downfall of many important ancient civilizations, and it will be the same for our current society. Sometimes, soil erosion is subtle and hard to see; even flat fields experience erosion. It can happen from wind or water. Erosion is not only an enormous problem for our agricultural productivity but also for the health of our waterways and oceans, as they are impaired with excessive sediments. If you do anything to improve your soils, priority No. 1 should be stopping soil erosion. Keeping your soil where it belongs is the best investment you can make. How can we do this?
• Minimize bare time. Plant a cover crop during those fallow periods or at least leave all the crop residues on site to protect the soil.
• Minimize soil disturbance during windy times. If the afternoons are always gusty, can you cultivate in the mornings instead?
• Don’t overirrigate, and quickly fix irrigation leaks. Use drip or micro-sprinklers whenever possible. Irrigation runoff causes a lot of soil erosion.
• If your land has curves, minimize tillage on the steepest parts. Maybe they are best left for pasture or perennial crops. Align your rows along the contours of the land, which also helps you improve irrigation efficiency. Your local National Resources Conservation Service (NRCS) or Soil and Water Conservation District should be able to help you do row arrangement/contour planting.
• Plant grass on your field roads and around field edges, especially where runoff may occur.
• Stand out in the rain. Observe where the rain pools and runs off. What color is the water? Does it run clear, or is it cloudy with sediment?
• Don’t get caught with your soil uncovered when you know the big rains are coming. Pay attention to the weather. Don’t pull your crop out or plow the week before the rainy season begins.
• Compaction can cause rainfall and irrigation to sheet off instead of penetrating the soil and soaking in. This sheet runoff can cause tremendous erosion of topsoil, so address your compaction issues.
• Overseed cover crops into your cash crops so they can cover the soil once you are done harvesting the cash crop. White clovers or vetches work really well in this type of system in some climates. Experiment to find out what works best where you live.
• Improve soil organic matter and microbial activity, which create the humic acids that “glue” soil particles together to help soil resist erosion.
• Plant windbreaks and hedgerows to minimize soil erosion.
• Last resort: Build a sediment pond to capture runoff and sediments. Once every one to two years, excavate the sediment from this pond and spread it back over your fields, where it came from.
Soil has physical characteristics, chemical characteristics, and biological characteristics. I have tried to cover a bit about all three dimensions of your soil. You must attend to all three to become a successful, sustainable farmer. As a farmer, you can’t get away with not modifying the soil properties in some way (unless you are doing soilless plasticulture such as hydroponics or aeroponics). Your job as a sustainable farmer, however, is to improve those soil characteristics over time in a way that is also economically viable. You may not be able to redress all the past soil abuses in a short period of time. You must be patient yet diligent. Don’t let soil health slip to the bottom of your meager budget or your overwhelming to-do list.
Keep thinking of your soil as like the bank account that I described at the beginning of this chapter. Are your withdrawals, in the form of crops or livestock sent off the farm, greater than your deposits of fertility? You need to replace those nutrients exported from the farm. Nitrogen-fixing crops are one of the best ways to add nutrients. On the other hand, if your deposits are much greater than your withdrawals, you could be causing excess nutrient buildup and likely pollution.
If you are just stockpiling crops or animals and not selling much, this could happen. It doesn’t seem like something a commercial farmer would do, but believe me, I have seen it. For example, I have witnessed many farms with unproductive animals that are allowed to continue to reside on the farm. The animals continue to urinate and defecate, of course, and this can lead to manure buildup and a host of other problems (such as disease) if they are not culled.
Although many of the farms we visited employed a myriad of excellent soil conservation and management strategies, the Crown S Ranch in Washington is not only practicing sustainable soil management, they are also monitoring it over time. For example, it used to take them 1.5 acres of pasture to finish a steer; now it takes only half that, or 0.75 acre. This is a direct result of their farm’s improved soil, which is now able to support more lush, diverse pasture plants that in turn support the animals on less land.
The family has also excelled at using animal impact and crop rotations to improve the soil and farm productivity at the same time. Read on for how they got started and what changes they have seen over time with their farm management practices, how they are relying less and less on off-farm inputs, and integrating preindustrial farming know-how into their modern-day farm.
Want to learn more about turning your farm into a farm with a future? Read Finding Farmland or Gardening Space for innovative ideas you can use while beginning or expanding your farming operation.
This excerpt has been reprinted with permission from Farms with a Future by Rebecca Thistlethwaite and published by Chelsea Green Publishing, 2012. Buy this book from our store: Farms with a Future.
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