Better Farming - short takes

February 2001

How much is your manure really worth?

Some simple calculations, plus a manure analysis, can help you see manure as something more valuable than just a disposal problem

by KEITH REID

With all of the talk about Nutrient Management Plans and manure by-laws, it is easy to look on manure as a disposal problem. This attitude, however, ignores the very real value of manure as a fertilizer and soil amendment. Unfortunately, by ignoring its value, we are more likely to handle manure in a way that does make it just a disposal problem.

The simplest way to calculate the value of manure is simply to multiply the amount of available nitrogen, phosphorus and potassium in the manure by the current prices for those nutrients. This approach both over- and under-estimates the true value, but it does give a first approximation. The calculated value of some common manures, using projected fertilizer prices for spring 2001, are given in Table 1.

It is important to remember that these values are based on average manure analyses. The actual nutrient content of the manure can vary widely from the average, and a manure analysis is the best way to predict what credit you actually give your manure.

One key factor is how well you retain the nitrogen portion of the manure. This is especially critical with liquid manure, where a large part of the nitrogen is in the ammonium form and subject to loss to the air if not incorporated quickly. The value of liquid hog or poultry manure is reduced by almost a half if the manure is left on the surface of the soil. Put another way, at an average application of 4000 gallons per acre of swine manure, a quick incorporation is worth $30 per acre.

These calculated values also assume that all of the nutrients being applied are actually needed. If you are applying manure to forage legumes or soybeans, there is no value to the nitrogen portion of the manure, but only for the phosphorus and potassium. Similarly, if the soil test in your fields is built up to the point where you don't need any additional P or K, then these nutrients don't represent any added value to the crop. With any nutrient management plan, it makes sense to move the manure around to the fields which can make the best use of the manure nutrients.

Micronutrients
While the value of manure is usually calculated using the NPK only, manure also provides a healthy dose of most micronutrients. This is one of the reasons why deficiencies show up much more frequently on cash-crop farms than on livestock farms. Table 2 shows the micronutrient and secondary nutrient content of a typical liquid swine manure.

Other benefits
Much harder to quantify are the benefits of manure to soil structure and soil health. I have had farmers tell me that they could see the line in the field where manure applications stopped, even though adequate mineral fertilizers were applied to make up the difference in crop nutrition. Despite this, I have not seen any research that focuses on the non-nutrient value of manure. One of the confounding factors in this type of research is that the effect does not show up every year -- it will be much more visible in stress years than in years with adequate heat and moisture. Another complication is that improper manure application can damage soil structure to the point that any positive effects are hidden.

Even with these difficulties in measurement, there is no doubt that the non-fertilizer benefits to manure do exist. When I am pushed to give a value to these benefits, my best guess is that the value of the organic matter added to the soil is at least as large as the fertilizer value of the manure and, in the case of many solid beef or dairy manures, may be larger.

All in all, it makes manure a resource worth managing!BF
Keith Reid is Soil Fertility Specialist for the Ontario agriculture ministry, based in Stratford. Email: keith.reid@omafra.gov.on.ca

What will soil management look like in 2051?

by KEITH REID

In this column, Soil Fertility Specialist Keith Reid usually presents information to help you manage better in the next couple of growing seasons. This month, however, in line with the theme of "Future of Farming," he looks ahead to how soil management might change in the next 50 years. His projections are based on the assumption that there will be no major new crop introductions, but that the existing economic and social pressures will continue in the same general direction as today.

Better Farming, Dateline January 1, 2051

Tillage
We still see the occasional moldboard plow at an antique display, but when bio-diesel hit $3 a litre, most farmers realized they could no longer afford intensive tillage. Fall strip tillage is common on the heavier soils before planting corn, but most crops are planted no-till.

Fortunately, the widespread adoption of seed coatings means that most of the soybeans are planted in the early spring, but don't germinate until the weather conditions are warm enough. The latest twist is a new coating that is stable until the field is sprayed with one of the common burndown herbicides. One of the adjuvants with the herbicide dissolves the seed coating, so the beginning of germination can be timed precisely.

Soil Testing
Grid sampling has proved a flash in the pan, farmers realizing it was not giving back enough information to justify the extra cost. It did, however, open farmers' eyes to how much variation existed in their fields, and to the opportunities for fine tuning management.

Advances in instrumentation have meant that on-the-go sampling for some nutrients is finally practical. On-the-go testing for nitrogen is particularly popular, allowing variable rate application of UAN (Urea-Ammonium Nitrate) solution at planting. (Anhydrous fell out of favour after that tractor-trailer accident on Highway 402, just upwind of London). The farmer still needs to take a sample ahead of time for a more complete analysis, to calibrate the meter, but it is a small inconvenience for the savings and for avoiding the fines for excess soil nitrate at the end of the season.

Phosphorus testing has become more accurate, but still has to be done in the lab. Very little P testing is done for production recommendations, anyway, but some is done to monitor for excessive levels.

Fertilizer Use
Despite 50 years of effort, scientists have still not succeeded in breeding a grass crop that fixes its own nitrogen out of the air. Progress has been made in increasing the amount of nitrogen fixation by soybeans, but the tradeoff has been in lower soybean yields. With the high cost of protein, it is more economical to buy the nitrogen fertilizer than to sacrifice the soybean yields. This doesn't mean that nitrogen is used carelessly -- the average nitrogen application is 20 per cent less than it was 50 years ago, while yields have continued to rise. Broadcast applications of fertilizer are almost unknown, except for potash on forages. Phosphorus is generally banded at planting, while nitrogen is placed in a band either at planting or side-dress time. The biggest hold-up, however, is waiting for fertilizer deliveries at planting time. Consolidation in the fertilizer industry has closed most of the local blenders, so very few farmers are close enough to a fertilizer outlet to pick up what they need.

Manure Application
Economics has finally achieved what the environmentalist could not, and made surface application of manure unpopular. Manure injection has become the norm, even for solid manure, to retain as much of the nitrogen as possible for crop production. The usual practice now is to digest the manure in the storage tank to release methane gas, and then to separate out some of the water from the slurry. The water is recycled as wash water in the barn, while the solid material, which has a consistency like toothpaste, is injected just below the soil surface.

The concentration of nutrients in this material means that it is in high demand for crop production, and an industry has sprung up to transport this material from livestock farms to cash crop areas. BF
Stratford-based Keith Reid is Soil Fertility Specialist with the Ontario Ministry of Agriculture Food and Rural Affairs. Email: keith.reid@omafra.gov.on.ca

The pros and cons of tillage

By Keith Reid

There has been much debate over the years about the impact of tillage on crop yields, and not everyone gets the same answer. So, as the harvest comes off the fields, it may be worth going back to look at what tillage is actually doing, and whether we need to keep tilling for the same reasons that our fathers and grandfathers did. If you go back to the original development of the self-scouring, steel mouldboard plow, it was built to break up the virgin sod on the prairies. It did an admirable job of incorporating the sod into the soil, and leaving a clean surface that could be worked down into a seedbed. Of course, during the 1930s, we discovered that it also left a soil surface vulnerable to erosion by wind and water.

Managing residue
There are still a few fields where the mouldboard plow remains, undeniably, the most appropriate tillage implement. I was called to a field last fall where the farmer was trying to use an offset disc to work up an old pasture field. The sod was so tough that the offset could do no more than cut it into chunks that would be almost impossible to work down in the spring. The plow was clearly the best choice for this field. Most other fields, however, have the stubble from an annual crop left on the field. Plowing is one option for incorporating some of this residue, but many other implements will work just as well.

The other factor is that secondary tillage and planting equipment has evolved. An old single disc drill or shoe-type planter could not handle much residue without plugging up. New equipment, however, has been designed to cut through surface residue, so it doesn't need the perfectly clean fields that the old equipment did.

Smoothing and leveling
The fields the pioneers worked were not smooth and had all the hummocks and hollows left from when the bush was removed. Tillage was necessary to level these fields out so both the planting and harvesting equipment could operate. Generally, we try to leave fields today smooth after harvest, so we shouldn't need as much tillage to get ready for the next crop. There are certainly exceptions, and there will be lots this year where wet fields are rutted up at harvest, but it is not normally the whole field that is affected.

Weed Control
Along with the sod, plowing buried a lot of weeds. Secondary tillage did the same for any seedlings, and chopped up perennial weeds that were trying to grow again. In the absence of herbicides, clean tillage was the best weed control available. The trouble is that weed populations soon shifted to include species not particularly bothered by tillage. Annual weed species that grew quickly and set lots of seed could thrive in the times between tillage. Perennial weeds that could regrow from rhizomes or corms were actually spread by tillage into new parts of the field. By mixing the soil, tillage was also actually planting a fresh crop of weed seeds into the ideal depth for germination with each tillage pass.

Aeration
Soils that are too tight, or that are poorly drained, contain too much water and not enough air. Tillage can create large pore spaces that bring more air into the soil. The downside is that these pore spaces are not very stable, and can collapse again relatively quickly. This is especially evident in soils that are low in organic matter. Unfortunately, adding air into the soil also accelerates the breakdown of organic matter, so the more intensively the soil is tilled, the shorter the time period the benefit from tillage lasts.

Loosening compacted soil
Tillage is actually more necessary today than in the past. As the equipment used in farming grows larger and heavier, the incidence of soil compaction is increasing and the most troublesome compaction is below the normal depth of tillage. Simply plowing deeper can break up some compaction, but it also brings subsoil to the surface, and dilutes the nutrients and organic matter in the topsoil with poorer soil from below. The amount of horsepower and fuel required also increases exponentially as the tillage depth increases. It is far better to avoid compaction in the first place, and to break it up with deep rooted crops, than to depend on deep tillage. BF
Stratford-based Keith Reid is Crop Fertility Specialist with the Ontario Ministry of Agriculture Food and Rural Affairs. Email: keith.reid@omafra.gov.on.ca

Watch out! That wet spring may lead to drought conditions later on

by KEITH REID

As I write this, very few people are considering the possibility of drought, since it has been raining every few days. But, paradoxically, the amount of rain we got this spring has actually increased the chance that some of you will suffer from drought before you read this.

You may wonder why there is such a stark contrast between this year and last, when dry weather produced high yields. The answer lies beneath the surface of the soil, in the conditions that your crops' roots are facing. Many of this year's crops were "mudded in", with soil conditions ranging from damp to downright wet. Tillage on these wet soils caused much of the soil structure to be broken down as the soil particles were squeezed together.

This is most evident in the heavier soils, but the same thing happens on all soil types. The net effect is that many of the pores and cracks that the root system normally expands through have been blocked. In the worst case, the roots are restricted to a narrow strip along the seed slot. But even with less severe compaction, the root system will not be able to expand to a normal volume.

The second effect of continued wet weather is that some soils have a high water table. Roots will not grow into saturated soil, so the depth of the root system is effectively limited to the shallow unsaturated layer. If the weather turns dry and the water table drops quickly, the roots will not be able to grow fast enough to keep up, particularly if the high water table was combined with compacted soil.

A third effect is that the number of root rots and other root diseases increase, since they thrive in wet conditions. This further reduces the rooting volume available to provide water and nutrients to the crop.

The end result is that this year's crop will suffer from shortages of both water and nutrients much sooner than crops grown in the last couple of years. As your father might have put it, the more rain you get, the more you need.

There is not much hope of managing this year's crop so as to reduce the impact of dry weather, since the damage has already been done. You should, however, be able to easily see the impact of past management. Fields with low organic matter and poor rotations will suffer far more than fields with a history of forages or cover crops. Any past compaction from heavy equipment traffic will also show up.

The long-term consequences for this planting season will depend on how much damage was done at planting time, and on what you do in the field from now until next spring. The first principle in dealing with any soil degradation is to avoid further damage, so take extra care to avoid compaction at harvest time this fall. This means taking advantage of dry soil conditions whenever possible, and limiting the weight of equipment on the field.

Waiting for dry soil conditions for fall tillage will also help. Primary tillage with either a moldboard or chisel plow in dry soils will shatter the layer below the plow soil, while the same implements in wet soils will smear and pack this layer even tighter.

Even more important for maintaining the long-term productivity of your soil is planning a sound rotation. Including forages is the ideal, and even cash croppers should look for opportunities to get forages into the rotation. This may mean investigating the cash hay markets, or trading land with a neighbour who has livestock. If this isn't possible, make sure you are including winter wheat or spring cereals in your rotation, and use a red clover cover crop. Some farmers consider this a nuisance, but it is in years like this that the practice pays off. Finally, include cover crops as frequently as possible to increase soil organic matter -- especially if you are growing crops that don't return a lot of crop residue to the soil. BF
Stratford-based Keith Reid is Crop Fertility Specialist with the Ontario Ministry of Agriculture Food and Rural Affairs. Email: keith.reid@omafra.gov.on.ca

Crops: Seedbed
by Keith Reid

Crops: The Lynch File
by Pat Lynch

May 2003

Controlling the losses in your soil's organic matter

Combining both increased inputs and greater retention of organic matter will result in a slow but sure increase in humus levels

by KEITH REID

Soil organic matter is a key part of sustainable crop production, adding to moisture and nutrient-holding capacity, contributing to nutrient cycling and playing a key role in soil structure and tilth. The behaviour of organic matter in the soil, however, is complex.

The amount of organic matter in any soil is a result of the net effect of both additions and losses. This means that simply adding more organic material to the soil may not have the desired effect of increasing humus levels. Additions of organic matter come from plant materials, including both the roots and any unharvested portion of the above-ground parts of the plants, as well as from free living algae and bacteria in the soil, and from direct additions of organic materials, like manure. Losses from the soil include consumption by soil organisms, respiration as carbon dioxide, and loss through erosion.

Once any organic material is added to the soil, it is immediately set upon by a myriad of organisms. Earthworms and soil insects break down large pieces of residue into smaller bits on which bacteria and fungi can go to work. At each stage, some of the organic matter is used to provide energy for the animals that have eaten it and lost to the air as carbon dioxide. Some is converted into simple organic compounds that are excreted, some is incorporated into the animal's bodies, and some is converted into complex organic compounds.

The residue from each stage of the cycle becomes food for the next stage. The simple compounds are most easily utilized, while the complex compounds are more resistant. Somewhere between 90 and 99 percent of the organic materials added to the soil end up back in the air as carbon dioxide. What's left behind is a mixture of complex molecules, resistant to breakdown, that we know as humus.

Even with this mixture, there is a huge amount of variation in how easily it can be broken down, and how long it will reside in the soil before wandering bacteria use it for food. Some of this humus will be in discrete particles, but most will be in films over soil particles or in complex mixtures of clay and organic matter.

The rate of organic matter breakdown depends on temperature, moisture and aeration. Cold conditions slow the activity of soil fauna, so organic matter breakdown is very slow. Soils in the Arctic are high in organic matter, even though the addition of new organic matter each year is small, because the rate of decomposition is so slow. At the other extreme, tropical soils, even in a lush jungle, are very low in organic matter because it decomposes so rapidly and completely.

Lack of oxygen also slows microbial activity, so poorly drained soils have higher levels of organic matter than neighbouring well-drained soils. We can see this in most fields in Ontario, which have dark soil in the hollows and lighter colours on the knolls according to the amount of organic matter in the soil.

Soil management can have a large impact on organic matter levels. Tillage for crop production loosens and aerates the soil, increasing the rate of microbial activity and the rate of organic matter decomposition. At the same time, the surface of the soil is more open to erosion, which selectively removes particles that are higher in organic matter than the bulk of the soil. Over time, the level of organic matter in our cropped soils has declined since the forests were cleared, with the resulting loss in soil structure and moisture-holding capacity.

Building soil organic matter is a much slower process than losing it, but it can be done with concentrated effort. It is not enough simply to reduce the rate of loss; we must also increase inputs of organic materials. Increasing inputs can be achieved by adding cover crops or forage crops to the rotation, so increasing the amount of crop residue left in the field, and by adding organic materials from outside the field like manure, compost, or biosolids.

Dealing with the loss part of the equation means reducing the frequency and intensity of tillage, and controlling soil erosion. Combining both increased inputs and greater retention of organic matter will result in a slow but sure increase in humus levels. BF

Keith Reid is a Soil Fertility Specialist with OMAFRA, based at Stratford. Email keith.reid@omafra.gov.on.ca

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May 2003

A "crib sheet" to help you pass your planting exam

Some handy hints to help you get through spring planting with flying colours

by PAT LYNCH

When I was at university, we had "crib notes" that we reviewed before writing exams. These notes were the main points taught over the course. Planting is like a final exam. You get to do everything learned through your years of experience and can implement new techniques picked up over the winter.

My "crib notes" on planting follow.

When working soils, the general rule is the shallower the better. Have your secondary tillage tool level side-to-side and front-to-back. When incorporating herbicides, especially keep it shallow. Diluting ppi herbicides is the number one reason for their failure.

Sun and wind dry out soils. If you are trying to dry soils, work when it is sunny and dry and plant at other times. If soils are becoming too dry, work at night.

Getting the most from your custom applicator. The six to eight weeks in the spring are the busiest for custom applicators. To get the most from yours, give them sufficient lead-time. Call 24 to 48 hours before you need custom application done. If for some reason you are not ready, then call and reschedule. You will help them and get better service than by calling at the last minute and expecting instant service.

Seed depth must be checked in every field. Depth changes with soil type and conditions. Generally, your settings at the end of the previous year will be deeper than where you want use to start plant this year. And depth will change through the season, so you can't check too often.

Populations. Check that all rows are planting and that seed sown matches with monitored seed. Most monitors do not distinguish between singles and doubles. Doubles cost money in seed and uneven emergence. Record all seed lots. Check the germ on the tag. Number 1 corn seed has a minimum germ of 90 per cent and Number 1 beans has 85 per cent. Never plant beans by weight, but always by seed count.

Manure applications. If it is too wet to plant, then hauling manure with spreaders or tankers will cause compaction and result in yield loss. Within guidelines, it may be better to apply a higher rate on fewer acres than try to cover all the acres. Plant what is fit and then spread manure when remaining fields are ready and plant them later.

Small weeds kill easy. Often, growers wait too long to control weeds. It is better to spray too early than too late. Small weeds are easier to kill and, generally, younger crops are more tolerant to post-herbicides. I have never been involved in a weed rescue case because the grower sprayed too early. This is especially important with Roundup Ready crops. Better to spray early when crops and weeds are small and come back with a reduced rate of spray to get late-emerging weeds. Also, weeds are easier to kill on good growing days.

Watch temperature swings. This is important when applying post-herbicides. Often, it is not the heat or the cold that is as important as the amount of temperature change. Crops become tolerant to hot or cold conditions with time. But if there is a sudden swing, the tissue can be sensitive. This is especially important when adding surfactants. If there is a chance of cold weather the next day, be careful about adding surfactants.

Work safely and take breaks. Planting is probably the most exciting but also the most stressful time for crop producers. Be sure to take frequent breaks and get as much rest as possible. Bank sleep on rainy days. While we have been fortunate in having few serious accidents at planting compared with harvesting, long hours in the field, lack of sleep and too much hurry lead to mental mistakes that can cost you money. BF

Pat Lynch CCA (ON) is head agronomist for Cargill in Ontario.