Northcentral

With so much attention being given to soybean rust, many people will be watching their soybean crop more closely than ever. If you plan on scouting your fields for diseases, you may also want to keep a watchful eye on visible signs of nutrient deficiencies. Yellowed, or chlorotic, leaves can be caused by deficiencies in K, Fe, Mn, S, and Mg. For pictures of these and other nutrient deficiencies on soybean, visit http://www.back-to-basics.net/nds/index.htm.

Not all nutrient-deficient plants will show visual symptoms of their malnutrition. This fact, coupled with some symptoms being common to more than one nutrient, bolster the need for in-season tissue testing. Nutrient levels of plant tissue will confirm suspected deficiencies and guide decisions for future nutrient and soil pH management.

Cool weather affects availability of N from the soil, from manures, and from previous crop residues. Cool weather slows down mineralization of N from organic matter. A soil nitrate test this month will be very helpful—but make sure the corn is at least 6 in. tall before taking it.

Nitrogen recommendations pose a major challenge for improvement. Agri-retailers, producers and extension staff in Ontario are conducting collaborative on-farm trials in a venture called Partners Validating Nitrogen for Corn.

Coming Events:

• July 10-13 — A Certified Crop Adviser session features topics on weeds, N for hay, and soil quality at the Northeast Branch Meeting of the American Society of Agronomy and the Soil Science Society of America, at the University of Connecticut, Storrs, CT - http://www.canr.uconn.edu/plsci/Morris/
• July 19-21 — InfoAg 2005, Springfield, Illinois, U.S.A. - http://www.infoag.org

a) it is so dry at seeding you apply only 50% of the target yield N to avoid economic loss if it stays dry, and add more when it rains, or

b) you apply all your N at seeding for the target yield, but conditions promote improved yield potential, so more is required.

While these two approaches differ considerably, there are some basic principles of annual crop growth on the northern Great Plains that need to be considered when using post-emergence N.

• Use a factor of 2.5 lb N/bu for high protein wheat, 1.25 lb N/bu for malt barley, and 3.0 lb N/bu for canola.
• You then have approximately 3 to 4 weeks between seeding and the start of stem elongation to make further additions to the crop N supply. If it remains dry, then you could elect to add no further N and take what you get from the growing season. If moisture conditions improve, you could add more N (using the N guide above) knowing that your early season plant development has not been restricted by N supply. It is important to remember that if a seedling develops under N deficient conditions, it will set limits on the yield potential – a means of responding to the available resources.
• The concept could also be applied when growing season conditions continue to improve after seeding, and you know that the yield potential will likely out-strip the N applied. For example, using a soil test of 20 lb N/A, you applied 55 lb fertilizer N for a total of 75 lb N/A, with a yield goal of 30 bu/A. However, at the beginning of stem extension, your previous experience and stored soil water measurements indicate that there is solid potential of 45 bu/A – you could add an additional 35 to 40 lb N/A to account for the increased yield estimate and maintain your grain protein potential.
• It is important to remember that post-emergence N application is not a suitable means of deferring your entire N application decision to some date of advanced crop development. If you are planning to do this you had better have confirmed sufficient levels of residual soil N to avoid early season crop N requirements for the establishment of high yield potential.
• Post-emergence N is standard practice on most of the area seeded to winter crops (winter wheat and fall rye), and most forages have all their nutrient requirements applied onto established stands. For both winter crops and forages, it has been long established that application as early as possible in the spring is critical to capturing the full yield response of these early growing crops.

Nitrogen price continues to be a concern among producers. In this environment it is useful to remember that yield is a major factor affecting profitability. This is because higher yield spreads production costs over more units (e.g., bushel, pound, bale), thus reducing the cost per unit of production and increasing efficiency of production. Many studies across the U.S. have shown that while fertilizer price affects optimum rate of application, the impact is not as great as one might think. As we approach the side-dress season this summer, cotton producers will be eying N fertilizer price and asking whether and how much reduction is appropriate. PPI Regional Directors Dr. Cliff Snyder and Dr. Mike Stewart have recently updated a piece entitled Using the Most Profitable Nitrogen Rate in Your Cotton Production System (click on the title to link to the article) that discusses in detail the impact of N price on cotton fertilization. Another useful piece entitled Nitrogen Fertilization of Irrigated Cotton as Fertilizer Prices Climb was recently released by Texas A&M scientists at Lubbock (click on the title to link to the article). Consider the basic MEY principles and the more detailed information in the articles as cotton side-dress decisions are made this summer, and be careful not to sacrifice profit by overreaction to input price.

According to the USDA on June 20: “ Jefferson County, Florida, reported a new find of soybean rust on kudzu. This is the fifth county in Florida that has reported soybean rust, though all are on kudzu. Seminole County in Georgia remains the only county with rust on soybean—and it was found on volunteer soybean plants in two locations. Numerous fields have been scouted from Kansas to Delaware and Florida to North Dakota, and Canada. Potential new infections could occur on non-soybean or soybean plants in the Southeast. The impact of Hurricane Arlene will not be known for 7 to 14 days. Additional spore monitoring through spore traps and ground observations of soybean and other hosts will indicate whether Arlene played a role in movement of rust spores.”

As farmers and crop advisers scout their soybeans this year, they should strongly consider plant tissue nutrient analyses. Recently published work by Dr. Tony Vyn at Purdue University has shown that plant tissue K levels in no-till soybeans should be higher than what was often considered optimum for conventional tilled soybeans in the past. Detection of nutrition problems this year can enable timely correction of problems this season, and advanced planning of preventative action for next year’s crop.

A wet spring followed by an abrupt dry period when many states got less than an inch of rainfall in the entire month of May, resulted in slow planting progress and crop development being later than normal. Pegging of peanuts by this time of year in most states is normally about 20%, but this year it is less than 5% in several states. Recent rains have delayed the vegetable harvest and slowed hay harvest in parts of Florida. Citrus harvest has been delayed in some areas because of heavy rains and some processing plants were temporarily shut down,as a consequence.

According to the Georgia Agricultural Statistics Service, “In south central Georgia, rains and wet soils have drowned cotton and peanuts in low land areas.” Pecan nut set appears good, peach harvest is about 20% complete, and onion harvest is nearing completion. Pasture condition is mostly good to excellent.

In Mississippi, like other parts of the Midsouth, corn silking is behind normal and so is cotton squaring. It is proving to be a different and challenging year in managing insects. Rainfall to date is about normal to slightly above normal in much of Mississippi.

In Missouri, corn condition is mostly fair to good with recent rains helping to improve the crop despite early season cold injury. Soybean planting and emergence are ahead of normal. Wheat harvest is behind normal by about 5 to 7 days. Pastures in the south central district still need rain. Pastures in other areas of the state are in mostly fair to good condition.

The North Carolina Agricultural Statistics Service has reported: “Overall precipitation remains below normal for the state. However, typical summer thunderstorms have brought heavy rain to some areas, while missing neighboring areas. Crops are progressing well as a result of two weeks of warm, sunny days.” About 50% of the state’s soybean acreage is planted and has emerged. Soil moisture is adequate to surplus in most areas.

Wheat ripening and harvest is slower than normal in Tennessee, cotton squaring is on par, and soybean emergence is ahead of normal. The battle against weeds and insects has become more difficult the last 2 weeks because of rainfall. Corn was being sidedressed with N. Hay harvest has been delayed because of the wet weather.

Rainfall in much of Arkansas is behind normal. Soybean emergence is a bit ahead of normal, while other crops are progressing at normal rates. Louisiana crop progress is similar to that of Arkansas, and rainfall is behind normal there too, with the exception of the south central area of Louisiana.

There are several BMP for plant nutrients that should be considered this summer:

1. Match the nutrient supply with the crop requirement.
Use soil testing to predict crop needs and tissue testing to monitor crop performance. Establishing realistic production goals is also important for matching nutrients and crops needs.

2. Appropriate fertilizer application.
The right fertilizer needs to be applied in the right balance, right placement, and right time to meet plant needs.

3. Nutrients should remain in the rootzone for plant uptake.
Irrigation water should be managed to help keep nutrients where they belong. Field buffers and run-off basins can help clean, collect, and recycle water leaving the field. Using only the minimum amount of tillage also conserves energy, soil moisture, and minimizes dust problems.

Natural resources are irreplaceable and must be protected. Soil is the medium that supports plant growth and is the source of most plant nutrients. Soil water and the soil atmosphere bathe the roots and keep the above-ground plant healthy and growing. A healthy soil, water, and air environment is in everyone’s interest.