Friday, October 12, 2012

Demonstration/Strip Trials - What should you learn from them?

The drought experienced this year has been unique. Drought occurs somewhere in Wisconsin nearly every production season. What has been unique this year is how widespread the drought is and the variability seen even between fields within a farm. In one field, corn might be barren and across the road good yields are measured. In many ways I was surprised to see corn hang-on as long as it did given the length of time no rain was received. In some of the fields yield-checked, we are finding ears with 16-18 kernel rows and 30-40 kernels per row.

Evaluating last year’s 'experiments' and using the lessons learned will help with next year's crop. Some new practices work and fit into your management style, others don't.

Every fall many farmers visit and evaluate hybrid demonstration plots planted by seed companies and county Extension personnel, among others. When checking out these plots, it's important to keep in mind their relative value and limitations. Demonstration plots may be useful in providing information on certain hybrid traits, especially those that are usually not reported in state corn performance summaries.

Use field days to make careful observations and ask questions, but reserve any decisions until you have seen the "numbers." Appearances can be deceiving.

In general, there are two major categories of on-farm research trials. The first is replicated trials that try to account for field variability with repeated randomized comparisons. Examples include trials conducted by universities and by public and private plant breeders. The other type is non-replicated demonstrations such as yield contests, on-farm yield claims, demonstration/strip trials and farmer observation and experience.

Field variability alone can easily account for differences of 10 to 50 bushels per acre. Don't put much stock in results from ONE LOCATION AND ONE YEAR, even if the trial is well run and reliable. This is especially important in years with tremendous variability in growing conditions. Years differ and the results from other locations may more closely match your conditions next year. Use data and observations from university trials, local demonstration plots, and then your own on-farm trials to look for consistent trends.

A few suggestions on how to evaluate research test plots:
  1. Walk into plots and check plant populations. Hybrids with large ears or two ears per plant may have thin stands.
  2. Scout for pest problems. Hybrid differences for pest resistance and tolerance should be monitored and noted all season, but will be most apparent in the fall. Counting dropped ears is a good way to measure hybrid ear retention and tolerance to European corn borers.
  3. Check for goose-necked stalks. This is often root pruning caused by corn rootworms. Hybrids differ in their ability to regrow pruned roots.
  4. Find out if the seed treatments (seed applied fungicides and insecticides) applied varied among hybrids planted, e.g. were the hybrids treated with the same seed applied insecticide at the same rate? Differences in treatments may affect final stand and injury caused by insects and diseases.
  5. Differences in standability will not show up until later in the season and/or until after a wind storm. Pinch or split the lower stalk to see whether the stalk pith is beginning to rot.
  6. Break ears in two to check relative kernel development of different hybrids. Hybrids that look most healthy and green may be more immature than others. Don't confuse good late season plant health ("stay green") with late maturity.
  7. Visual observation of ear-tip fill, ear length, number of kernel rows, and kernel depth, etc. don't tell you much about actual yield potential. Hybrid differences are common for tip kernel abortion (“tip dieback” or “tip-back”) and “zipper ears” (missing kernel rows). Even if corn ear tips are not filled completely, due to poor pollination or kernel abortion, yield potential may not be affected significantly, if at all, because the numbers of kernels per row may still be above normal.
  8. Be careful with test plots consisting predominately of one company's hybrids. Odds are stacked in their favor!
  9. Other observations that should be made:
    • Dry down rate
    • Test weight
    • Disease damage
    • Grain quality
    • Ease of combine-shelling or picking
Further Reading

Saturday, October 6, 2012

To Rotate, or Not to Rotate - What Are You Going to Do in 2013?

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Crop rotation is a universal management practice that has been recognized and exploited for centuries and is a proven process that increases crop yields. In the Midwestern U.S., a biennial rotation of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] produces significant increases in the yields of both crops.

There are clear indications that the current corn-soybean rotation is unstable, easily disrupted by weather, disease, and insects, and rely heavily on foreign trade and biofuel production. Midwest cropping systems although productive, are highly specialized, standardized and simplified to meet increasing demands (Brummer, 1998; Kirschenmann, 2002).

Many of these cropping systems are approaching monoculture systems that need to incorporate technological advances, high fossil fuel based inputs, and genetic engineering to remain sustainable. Cropping systems specializing in one or two crops with little attention to crop diversity could lead to biological and physical soil degradation and ultimately soil chemical degradation (Kirschenmann, 2002). Nature’s plant and animal diversity is currently replaced with a small number of cultivated plants and domestic animals (Altieri, 1999).

The mechanism for the rotation effect is unknown. One hypothesis is that one factor causes the effect. Another hypothesis is that multiple factors cause the effect and risk of expression depends upon the environment. Research evidence began mounting in the 1970’s, which indicated that in spite of all the management inputs a farmer might impose, there was still a yield advantage to be obtained from rotations. These studies showed that corn yields are usually higher when the crop is rotated with some other crop rather than grown continuously. Yield advantages to corn from rotating with some other crop are at least 10%. In addition, soybean yields also improved by 10% when the crop is rotated out of a continuous pattern.

More research that is recent has shown this increase to be even greater than expected with responses up to 19% (Figure 1). The rotation effect lasts two years increasing corn grain yield 10 to 19% for 1C and 0 to 7% for 2C.

Figure 1. Corn yield response to rotation following five years of soybean during 1987 to 2006 at Arlington, WI. Letters indicate statistical differences at P < 0.05. Percentage values indicate relative differences compared to continuous corn.

Adding a third crop like wheat (Triticum aestivum L.) does not increase corn grain yield, but does improve soybean grain yield (Figure 2).

Figure 2. Corn and soybean yield response in a corn-soybean-wheat rotation during 2004 to 2006 at Arlington, WI. Letters indicate statistical differences at P < 0.05. Percentage values indicate relative differences compared to continuous corn or soybean.

If there is only a one-year break in the rotation then the second corn phase is equivalent to continuous corn (Figure 3).

Figure 3. Corn yield response in various corn-soybean rotations during 1998 to 2000 at Arlington, WI. Letters indicate statistical differences at P < 0.05. Percentage values indicate relative differences compared to continuous corn.

At least two break years are needed to measure a response in the second corn phase compared to continuous corn (Figure 4).

Figure 4. Corn yield response in various rotations during 1990 to 2004 at Lancaster, WI. Letters indicate statistical differences at P < 0.05. Percentage values indicate relative differences compared to continuous corn.

Although scientists cannot yet satisfactorily explain the rotation effect, farmers can exploit it every year. In 2013, more acres will likely be planted to a third year of corn. These acres will be at continuous corn yield levels regardless of the number of break years. It will be important for growers to consider getting back to rotating crops. The age-old practice of rotating crops, which for a while was considered unnecessary, has returned to today's agriculture with proven benefits.

Literature Cited

Altieri, M.A. 1999. The ecological role of biodiversity in agroecosystems. Agric. Ecosyst. Envron. 74:19-31.

Brummer, E.C. 1998. Diversity, Stability, and Sustainable American Agriculture. Agron. J. 90:1-2.

Kirschenmann, F. 2002. Why American agriculture is not sustainable. Renewable Resour. 20:6-11.

Further Reading

Cropping systems and rotations. See