Ag Connection
Your link to the Universities for ag extension and research information

Volume 5, Number 3
March 1999


This Month in Ag Connection

On-Farm Starter Fertilizer Response in No-till Corn
Sunflower Joins 'Tough Weeds' List; Farmers Urged to Vary Controls
1999 — Corn Flea Beetles Again?
FarmFIRST Program

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On-Farm Starter Fertilizer Response in No-till Corn

Early research on starter fertilizer showed that it usually increased early season crop growth, but in Missouri and adjacent states this only occasionally translated into a yield advantage. Recent trials from other states are showing that starter fertilizer looks like an economically sound practice in no-till systems. Dave Mengel at Purdue University found a yield response to starter in 8 of 11 no-till site-years, but only in 1 of 11 moldboard-plowed site-years. This yield response was primarily to the N component of the starter. Indiana is now recommending starter in no-till situations, but not when tillage is used. Illinois research showed similar results.

No-till corn and sorghum in Kansas frequently responded to starter fertilizer in experiments conducted by Barney Gordon and David Whitney. One of their experiments tried N-only, P-only, and combinations, and found clear responses to both the N and the P. In addition, 30 lb. N/acre out-yielded 10 lb. N/acre in starter. Their research also established that some hybrids of both corn and sorghum consistently respond to starter fertilizer, while other hybrids do not. They have found a trend for more response with later-maturing hybrids.

Missouri Experiments
These favorable results in adjacent states prompted the Missouri research reported here. Based on the Illinois and Kansas experiments, it was possible to focus in on a few specific treatments of interest and evaluate them in on-farm replicated strip trials. The core treatments are:

  1. No starter
  2. Typical low-N, high-P2O5 starter
  3. Medium-N, medium-P2O5 starter
  4. N-only starter

Experiments were planted in cooperation with producers in Lafayette, Morgan, Saline and Cooper counties who currently use starter fertilizer for no-till corn production.

In-field observations and measurements consistently found increased growth and earlier tasseling due to applications of starter fertilizer. This was also visible in aerial photos. In general, differences between plots with and without starter fertilizer were clear. However, differences between plots with various types of starter were small or undetectable.

Significant yield increases to starter fertilizer were found in six of the seven experiments, generally with no difference in yield between the different starters (see table).

A yield increase of at least 9 and up to 26 Bu/acre was seen in each of these six experiments. Yield increases were smaller in 1998 than in 1996 or 1997. Research has not determined why response to starter fertilizer is more in some years than others.

The only experiments in which N + P starter appeared to out-yield N-only starter were the Borgman 1996 and 1998 locations. These experiments were on rented ground that tested low in P. Using starter P may be worthwhile in this situation, but when soil test P was medium or higher there was no benefit to adding P. Overall, the N-only starter appears to be the most cost-effective alternative.

Averaged over six experiments, the N-only starter increased yield by 13 Bu/acre. An average value for this yield increase might be 13 Bu/acre x $2.50/Bu = $32/acre. By comparison, the material cost for the N averaged about $9/acre at the rates used, and equipment cost for the starter attachments is about $3/acre if used at least 5 years over at least 300 acres. This gives an average net return to material and equipment of $32 - 9 - 3 = $20/acre for these six experiments. Slower planting is another cost of using starter fertilizer. On average, using starter slows the planting operation by about ten to fifteen percent. The value of this lost time depends on the individual farming operation.

There did not appear to be any yield benefit to using in-furrow starter in addition to placed starter, nor to the addition of starch, S, Zn, or B in the experiments where those materials were used. The starch treatment was tried because researchers in Idaho have reported yield gains from using row-placed starch for wheat.

Results from small plot research studies at MU research centers show a yield response of 8 bushels/acre for starter fertilizer (see table below). This helps confirm that substantial yield responses to starter are often observed in Missouri conditions.

Yield response of no-till corn to starter fertilizer in other small-plot experiments in Missouri.
Year Researcher Location Yield Response
1996 Wiebold Columbia -2            
1996 Blevins Columbia 17            
1996 Stecker Columbia 4            
1996 Stecker Novelty 12            
1996 Stecker Corning 5            
1997 Wiebold Columbia 10            
1997 Blevins Columbia 0            
1998 Wiebold Columbia 15            
Average 8            

In Summary

  • The N-only starter had the best economic response due to lower material cost. Average return to fertilizer and equipment for this treatment was $20/acre.
  • The cost of slower planting when starter fertilizer is used is difficult to put a number on, but should be subtracted from the $20/acre figure above to figure true return to starter.
  • Eight small-plot experiments in Missouri over the last three years have shown an average yield response to starter of 8 Bu/acre for no-till corn.
  • Starter fertilizer for no-till corn in Missouri appears to be a profitable practice on average.

Author: Peter Scharf, MU Agronomy Extension


SunflowerWeed Link
For weed science information on the Internet, check out the MU Weed Science Page

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Sunflower Joins 'Tough Weeds' List; Farmers Urged to Vary Control

Add common sunflowers to the list of weeds that can't always be controlled with recommended herbicides.

For those and other tough-to-control weeds, it's time to change control strategies.

We have confirmed reports of sunflowers resistant to ALS herbicides in Atchison, Ray, and Carroll counties and have found suspected resistance in most counties along the Missouri River. ALS resistance has also been identified in Iowa and Kansas. ALS herbicides, like Scepter and Classic, control weeds by inhibiting a growth enzyme.

The herbicide-resistant common sunflower can be a major threat to crop yields. MU studies show that just seven plants in a three-foot row can reduce yields 65%.

In a recent MU survey, 30% of the respondents wrongly said there have been no strategies developed to control ALS resistant common sunflower. These results are disturbing. There are several ways to at least slow the spread of this weed. Rotating herbicide mode of action is the best strategy.

A field study near Miami showed that one application of Classic killed 36% of the weeds, and a second application at twice the rate increased the kill to 60%. One application of Scepter controlled 78% of the sunflower weeds but a second application at twice the rate did not kill any of the surviving weeds.

This indicates the sunflowers on this site are resistant to Classic and Scepter herbicides. The sunflowers at the site were also resistant to Python, Raptor, Expert, and First Rate.

Remember — we've always had herbicide-resistant weeds and you have to change herbicides or 'mode of action' to keep from getting too many of those weeds.

Growers can't keep using the same herbicides year after year without eventually seeing a buildup of pesticide-resistant weeds or a shift to weeds naturally tolerant to those herbicides.

We are concerned with the number of farmers who may start depending exclusively on glyphosate — Roundup — for weed control in transgenic soybeans.

Glyphosate is an effective strategy to control weeds, but over time, the use of multiple herbicides with different modes of action is the best approach.

And, don't give up on alternative approaches — cultural techniques, competitive crops, and cultivation. Remember, no weed has developed resistance to steel.

Author: Bill Johnson, Commercial Agriculture Weed Scientist; Jayla Allen, MU Graduate Student in Weed Science; and Reid Smeda, MU Weed Scientist

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1999 Corn Flea Beetles Again?

Flea beetle predictions are made by adding the average daily temperatures for December, January and February. If the sum of these average monthly temperatures totals less than 90 F, then it is likely few flea beetles have survived. A total between 90 F and 100 F suggests flea beetle damage is possible. When the sum of these monthly temperatures is above 100 F, flea beetle survival will be good and damage is likely. The projected sum of average temperatures for December 1998, January 1999, and February 1999 is barely above 100 F for central Missouri.

The corn flea beetle overwinters as an adult in grassy areas. When winter temperatures are low, poor survival results and few early season problems occur in seedling corn. A warm winter allows increased flea beetle survival and a cool, wet spring slows corn growth during the two to three leaf stage. Corn flea beetles then have a chance to feed on the young field corn leaves for as long as the weather remains cool.

Typical damage causes silvering and withering of the seedling leaves. Flea beetle's economic threshold on seedling corn is 5 or more per plant, there is significant feeding injury, and the plants are under stress. Stewart's wilt, a bacterial disease of corn, can also be transmitted during the flea beetles feeding. Most current field corn hybrids are resistant to Stewart's wilt, but popcorn and sweet corn can still be infected.

Flea beetle numbers on corn will likely be high over Central Missouri during emergence and the seedling stage. The important factor missing from this prediction is the temperature during and just after emergence. If it is cool enough to slow or stop early growth, scout corn for flea beetle damage immediately. Under most situations, the return of warm weather stimulates seedling growth and the corn plants will recover. The early leaves on seedling corn are rapidly shed during plant growth anyway.

Author: Jim Jarman, Agronomy Specialist


FarmFIRST is a University of Missouri Extension and College of Agriculture, Food and Natural Resources program to assist Missouri farmers and agribusinesses as they deal with the current period of low commodity farm prices and market fluctuations.

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Several financial realities are combining to make farmers anxious about their financial future. Among the factors that farmers are coping with are: low and highly variable market prices, poor or erratic yields, poor quality of grain, harvest and storage problems, high financial commitments due to investments made when prices were good, family communication, uncertainty of government program guidelines, and the increased pace of technological change.

Specialist teams in each region have been designated as first responders — either for financial analysis and counseling or counseling related to stress. They, in turn, can call on any co-workers throughout the state.

First responders for Central Missouri are Bill Buehler (573-378-5358), Melvin Brees (660-248-2272), Parman Green (660-542-1792), Brocke Laws (573-634-2824), Mary Sobba (573-581-3231) and Don Utlaut (660-827-0591).

For more information, contact one of these specialists, your local extension Ag specialist or look on the Internet at .

The statewide tollfree direct access number for FarmFIRST is 1-877-363-3659. This hotline is open 8 a.m. to 5 p.m., Monday through Friday.

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University of Missouri ExtensionAg Connection - March 1999 -- Revised: April 20, 2004