A sampling of cover crops for your farm

by KEITH REID

For any cover crop to be workable, it must fit in with your cropping system. This means that planting the cover crop must be integrated with some other field activities, or be done at a time when it does not interfere with them.

Once planted, it should grow consistently, and not increase the risk of diseases or pests in succeeding crops. And because the benefits of cover crops are not immediate, the cost must be relatively low. Many cover crops have limited popularity because they fall down in one or more of these categories.

Red clover is still one of the most popular cover crops. Seed is easy to obtain and economical, and the value of the nitrogen fixed by the clover is generally enough to cover the cost of the seed. It has grown quite consistently under spring cereals or when frost is seeded into winter wheat.

As wheat yields have increased, however, there have been complaints that the dense stands of wheat compete too vigorously with the clover seedlings, resulting in poor growth. One way around this is to seed the clover after wheat harvest. Vigorous growth will depend on getting adequate moisture for germination and establishment, but clover seeded in July has time to produce lots of top growth before freeze-up.

The impact of red clover on corn yields is significant, particularly in no-till. The drawback in no-till can be the difficulty in killing the clover. A combination of herbicides and tillage may provide the greatest net benefit from clover in reduced tillage systems.

An alternative to red clover would be to plant cereals after harvest. They do not fix any nitrogen, but they are able to tie up nitrogen already in the soil and protect it from loss over winter. In addition, the fine, fibrous root system is even better than clover for soil structure.
Spring cereals have the advantage that they die over winter, so no chemical control is necessary. Bin-run seed is fine and keeps the cost down, as long is it is free of weed seeds. Growth may not be too quick during the heat of the summer, but should take off once the cooler weather arrives. If planting is late in the fall, spring cereals will actually produce more top growth than a winter cereal, because they keep growing rather than being programmed to go dormant as the weather cools down.

Fall cereals, like rye, are also inexpensive and consistent. The only trouble with rye is that it grows very quickly in the spring. You have to be prepared to control this crop quickly once it starts to shoot ahead, since it can go from knee-high to over your head within a few days. This crop is well used in tobacco and some horticultural crops, but it deserves more attention in some of the field crops.

Oilseed radish is popular as a "catch crop" to catch the nitrogen from fall-applied manure. It will grow vigorously where there is lots of soil nitrogen, but may be disappointing if you grow this crop where no manure was applied. The large taproot does not provide as much benefit for soil structure as a fibrous rooted crop. Field peas have been tried in some fields with good success. The chief drawback is the cost of the seed, and the relatively large volume that needs to be applied. Field peas grow quickly in cool fall conditions, and fix large quantities of nitrogen. The peas winterkill, and the residue breaks down quickly so it is easy to plant through. Hairy vetch is a perennial legume crop that is easier to kill with herbicides than clover, which makes it attractive for no-till systems. Seed cost is the main reason it is not used more often.

This is only a small sampling of potential cover crops for your farm. Any field crop you grow could potentially be used as a cover crop in the right circumstances. Don't be afraid to try something new. You might find something that works well for your farm that you would otherwise never have thought of. BF
Keith Reid is a Soil Fertility Specialist with OMAFRA, based in Stratford. Email: keith.reid@omafra.gov.on.ca

So you want to do a test plot?

by KEITH REID

To make the best use of the effort you put into planting test plots, it is important to follow a few simple rules:

1. Plan appropriate comparisons.
The most common mistake in plots is trying to compare too many different things, either inadvertently or on purpose. If three or four different factors are varying at once, it is impossible to tell afterwards which one caused the yield difference. It is sometimes appropriate to compare two different systems, but be aware that this is what you are doing, and limit any conclusions to the whole systems rather than the factors that make up the systems.

In most cases, the easiest way to avoid too many comparisons is to take extra care that the whole trial is treated identically, except for the input being tested. This means, for example, that if part of the plot has weed escapes and needs a rescue herbicide treatment, the entire plot gets sprayed.

2. Account for variability.
It is impossible to eliminate variability in any field trial. There will be variation in soil type, soil fertility, weather, and a host of other factors. The key to successful trials is to remove as much of this variability as possible from the comparison, so that as much difference in results as possible comes from the treatment being tested, rather than from variability between plots. You should also measure and record any factors, such as soil test, rainfall, and temperature, which could affect the outcome of the trial. This can be extremely useful when the time comes to interpret the final results.

The first step in maximizing the difference from the treatments, and minimizing the effect of in-field variation, is to lay out the plots as long, narrow strips rather than square blocks. This increases the chance that the different treatments are being imposed on similar soil conditions.

Variation may be random or systematic. Most statistics are designed to deal with random variation, which doesn't have any underlying pattern. Assigning treatments to sub-plots in a random fashion is critical if you are to keep from favouring one treatment over another, and introducing a bias into the results.

Minimizing the effect of systematic variation requires a different approach. An example of systematic variation is a change in soil type within the field. If the plot is planted so some of the treatments are on one soil type, while the rest are on a different type, any differences measured could be due to soil type rather than the treatments. To avoid this, always plant across the major variation in the field. You should also try to keep the areas of different soil types or slope classes constant between plots. If this is not possible, it might be better to sub-divide the plots further into paired sections on each different soil type or slope class.

3. Replicate.
At their most basic level, statistics try to sort out whether most of the variation measured between plots is from the treatments applied or from the underlying variation in the plots. If there is too much underlying variation, then there is no way to know for sure whether the differences between treatments are real or not. The only way to measure this variation is to repeat the treatments more than once. Ideally, this should be within the same plot area, but it could also involve replications over plots on several different farms. The danger in this is that the variation from farm to farm is probably greater than the variation within a field, so the trial won't be as sensitive to differences between treatments.

In general, the more times a test is repeated, the more accurate the results, but the amount of effort required also increases. Most farmers would like to do as few replications as possible. To give any idea of the variance between plots, the comparisons must be repeated at least three times. It also simplifies the analysis of the numbers greatly if all the treatments are repeated the same number of times.

4. Measure carefully.
The best laid out plots won't give accurate results if the yield (or other factor) isn't measured properly. Be sure the scales or weigh wagon are properly calibrated, and that the moisture meter is also working properly. Keep accurate records of where each plot is, and any differences between plots that might affect the measured results.

If you are depending on a yield monitor to measure the differences between plots, decide first if the yield monitor can even measure the type of difference you want it to. Yield monitors have difficulty measuring yield differences between different hybrids or varieties, because differences in moisture or bushel weight affect the way the sensors respond. Weigh wagons are much more consistent for these types of comparison.

To measure the impact of a management change on a single variety, yield monitors can work quite well. To be accurate, however, it is essential that the area measured is large enough to provide a consistent flow over the sensor. A plot length of 700-1000 feet is normally adequate. Since the flow through the combine is also affected by whether it is travelling uphill or downhill, you should try to harvest all of the plot strips in the same direction.

5. Share your results with others.
The best designed and managed test plot still only gives the results from one environment, and the results could be quite different with different weather or soil conditions. By combining your results with other plots, you will have more confidence in the results and increase your chance of making profitable decisions. BF
Keith Reid is Soil Fertility Specialist for the Ontario agriculture ministry, based in Stratford. Email: keith.reid@omafra.gov.on.ca

The pros and cons of crop rotations - in good years and bad

by KEITH REID

The benefits of sound crop rotations are most evident in tough years. This was clear in the 2000 growing season, when both soys and edible beans suffered much less yield loss where the soil had a good structure. It is also evident in dry years, where corn following row crops shows drought stress much sooner than corn grown after a sod crop.

Advantages
The impact of crop rotation can be divided into three general areas: soil quality factors, disease and pest factors, and cropping system factors.

Improvements in soil quality have the greatest impact on the long-term sustainability of crop production, and also in the productivity of individual crops, but they also require the greatest commitment to crop rotation. Simply switching from continuous corn to a corn-soy rotation is not going to produce measurable increases in soil organic matter or structural stability, although there will likely be an increase in corn yields even with this short rotation. The largest gains in soil quality come from including fibrous rooted crops in the rotation, and preferably for multiple years. These soil-improving crops include winter cereals (especially underseeded to red clover), and mixed hay crops. If it is impractical to include forages in the rotation, seeding cover crops will help to fill the gap.

The principal advantage from crop rotation is a general improvement in soil structure, although it is possible to find rotations where this advantage is debatable, particularly where a large number of low-residue producing crops is included. In a long-term rotation experiment at Elora, former University of Guelph professor Dr. Tony Vyn who is now at Purdue university, found the highest aggregate stability (a measure of soil structure) in first year corn following two years of barley (although it was not significantly higher than corn following wheat or alfalfa).

The lowest aggregate stability was in first-year corn following soybeans. Continuous corn was in between these extremes. In a different study at Harrow, Dr. Craig Drury research scientist at Agriculture and Agri-food Canada found an increase in soil organic carbon of over 14 tonnes per hectare in the top 60 cm after 34 years of rotational corn, compared to continuous corn.

Improved soil structure and increased organic matter also lead to increased water infiltration, which can result in more available water for crops. There is also an increase in root growth, which allows the plant to extract water and nutrients from a greater volume of soil.

Crop rotation has a huge effect on the amount of insect and disease pressure in our crops, which can not only increase yields but reduce the amount of pesticides we need to use. Most of this effect comes from breaking the life cycle of the disease or pest. The classic example is the corn rootworm, whose larvae only attack corn roots. Since eggs are laid in cornfields, if the eggs hatch into a different crop the next year they will starve to death without doing any damage. This has provided an effective way of controlling this pest for decades. Unfortunately, in areas where a short corn/soy rotation is practiced almost exclusively, the rootworms are starting to adapt by laying eggs in soybeans. The longer and more complex the rotation, the less likely it is that this type of adaptation will occur.

There are many other examples of crop rotation breaking the life cycle of pests, but for many insects or diseases it means designing a rotation that avoids crops of similar types following one another, rather than just the same crop. Take-all a fungal disease of wheat roots is a good example. It will build up under barley or quack-grass without hurting those crops, but winter wheat planted after barley or grassy sod can suffer as much as take-all if it followed wheat.

White mould is another disease that affects a wide range of broadleaf crops, so sunflowers following canola or soybeans is an invitation to disaster, even though the crops are not similar at all.

Crop rotation is also very valuable in spreading both risk and workload. Farmers with only one commodity to sell are vulnerable to downturns in the market affecting that commodity. Having a wide range of commodities provides some protection from market risk. It also reduces the chance that all of the crops will be affected by adverse weather, since each crop has slightly different preferences for growing conditions. Corn and soybeans do well in the warm years, while cereals and canola shine in cooler weather like that of 2000.

A variety of crops also spreads out the planting and harvest seasons. The ground that is planted to winter wheat does not need to be planted the next spring, and the wheat harvest takes place before any other crops are ready. This makes better use of available manpower and equipment, and also reduces the risk of adverse weather at planting or harvest affected the entire crop. It can also help to even out cash flow over the year.

Disadvantages
No practice is completely without drawbacks, and so it is with crop rotation. One drawback not often considered is that rotations will likely require a wider range of equipment than a mono-culture, and will certainly require more bins to keep the various crops segregated.

The most obvious disadvantage is that not all crops provide the same opportunity for net income. This is particularly true of forages on non-livestock farms. The value of hay as a cash crop is generally less than the value as an on-farm feed source, and is also much more sensitive to quality problems from less-than-perfect harvest weather. A complete accounting, however, will include the net income over the entire rotation, where the benefit of higher yields and lower input costs can be put in perspective. BF
Keith Reid is Soil Fertility Specialist for the Ontario agriculture ministry, based in Stratford. Email: keith.reid@omafra.gov.on.ca

Take good care of yourself and your soil when planting

by KEITH REID

Is your clover planted yet? In most of the province, it is actually too late for planting clover this spring, but that doesn't mean you should give up on including cover crops in your plans for this year. Clover, or another cover crop choice, can be planted after wheat harvest. Whenever it is planted, including a cover crop will add to the pool of soil organic matter and improve soil tilth.

How well is your soil drying out? Is your soil drying out on top, while still wet a couple of inches below the surface? This could be an indication of poor internal drainage, a symptom of low organic matter or of tillage when the soil was too wet. Heading into the field before the soil has dried out to the depth of tillage will make the problem even worse for future years.

Have you left crop residue on top of your soil? It's hard to break the habit of associating a perfectly clean, smooth surface after planting with good farming. Unfortunately, this type of farming also provides the greatest risk of erosion by wind and water, without adding anything to the yield potential of the field. You can argue about whether no-till is sustainable or not, but this doesn't mean that the alternative is burying all the residue. Keeping at least 20 per cent of the soil surface covered with residue can stop most erosion without compromising crop yields at all.

How can you get the most benefit from manure? There has been much talk this spring about making the best use of the nitrogen in manure, but the benefits of manure go far beyond the fertilizer replacement value. Your plans should include ways to maximize the benefits from the organic portion of the manure. These could include ensuring soil conditions are dry enough to avoid compaction before spreading manure; using multiple small applications instead of one large one; and combining manure with cover crops.

Have you stopped to admire the wildflowers yet? As farmers, we are focused on the renewal of life in the fields every spring. But, at the end of planting season, have you ever realized that you never even noticed the wildflowers in the bush? Stopping for a few minutes at the end of the field for a walk into the bush not only breaks the monotony of tractor driving, but also helps to keep the inevitable setbacks in perspective. Even better, meet your family for a picnic in the bush, so you can renew your family connections at the same time.

Are all the shields back in place on your equipment? There is never enough time to do everything that needs doing during planting time, so it is tempting to head back to the field after a rush repair without replacing all the shields. After all, you know that sprocket or shaft is exposed, and you will keep clear of it.

Unfortunately, this detail can easily slip your mind after hours spent in the field, leading to a painful entanglement. If you don't have time to put the shield back on, where will you find the time to recover from a serious injury? Time spent on safety is an investment in your future.

So take care of yourselves, and your soil, this planting season. BF
Keith Reid is Soil Fertility Specialist for the Ontario agriculture ministry, based in Stratford. Email: keith.reid@omafra.gov.on.ca