No-till receives mixed reviews under the stress of drought, but all agree 1988 was not a year on which to base tillage choices.

REPORTS from around the country indicate that many no-till fields showed more drought related stress in 1988 than conventional-tilled fields; of course there were exceptions.

In Kansas, where the drought conditions were less severe, production in no-till fields was as successful as acreage under conventional tillage. ÏIn studies comparing no-till and conventional-till fields this summer we had similar yields," says Dr. Ray Lamond, Kansas State University extension soil specialist.

The dryness in the row crop producing areas of the Great Plains was not as severe as in the corn belt allowing all tillage systems a better chance.

No-till production is common in many of the fields west of Missouri, particularly in grain sorghum on dryland. Dr. Larry Murphy, Potash and Phosphate Institute (PPI) agronomist in Manhattan, KS, agrees that in his area of the Great Plains no-till responded as well as conventional fields under the prevailing stressful conditions.

In North Dakota, Al Black of the USDA-ARS Great Plains Research Center, Mandan, saw the drought as an opportunity to compare conservation tillage systems to conventional systems. He was pleased with early season results.

"The stubble on no-till fields allowed soils to gain 2 inches of soil water over winter," he says. Conventionally-tilled fields in the same area lost 1 inch of soil moisture over winter.

The residue really helped keep,, the moisture in the seed zone, says Black. "Our yield responses to it weren't large, in the neighborhood of 2 to 4 bushels. But when your yields are in the 8 to 12 bushel range, it is a measurable response."

ALL TILLAGE METHODS SUFFERED

Despite the early favorable response, Black says all cropping systems fell prey to the drought.

The dry weather was the downfall of no-till, minimum-till. and conventional-till fields across the country. It hardened already severely compacted soils and stymied surface applied fertilizers and herbicides.

Joe Touchton, agronomist at Auburn University, says that response to tillage Systems can not be related strictly to the dry weather. Other variables affect response. such as timing of planting and applications."Even though your absolute yields are greatly different. generally the response to tillage is not that different." he says. "What yields best in dry weajher generally yields best in better rainfall years.

In the Corn Belt, the drought was more severe and problems in no-till and minimum-till fields more pervasive. Trash and later planting dates put the fields at a disadvantage.

By planting a few weeks later, soil had dried out and relieving rains never came. With little moisture, germination slowed and seedlings had difficulty anchoring and finding nutrients.

ROOT GROWTH RESTRICTED BY HARD SOILS

Dr. Jay Johnson, agronomist at Ohio State University, says several acts of nature combined to affect crdps: in his area corn was hardest hit. "We didn't have a 16t offreezing and thawing during the winter of 1987-88, so our soils were somewhat compacted. It restricted root growth, especially in no-till."

Corn in Ohio faced additional obstacles, including searing temperatures. Many nutrients were surface applied and never moved into the soil profile. Rain would have moved some of the surface applied nutrients and pesticides, but the soil compaction aggravated the ineffectiveness of pesticides and fertilizers.

"The roots went deeper in the soil profile in search of water." Johnson says. "They got below the nutrient rich zone and ran out of fertilizer and nutrients - in other words, they strangled themselves to death."

In fields where soils had been inverted, roots were able to take in adequate nutrients. Compaction and dry weather contributed to poor corn performance in Illinois, according to Dr. Robert Hoeft, Illinois Cooperative Extension Service. Cooler soil in no-till fields during germination was also a factor that held back some varieties of Illinois corn.

Soil temperatures in no-till fields take longer to warm to a favorable planting temperature. Because farmers waited later to plant, the no-till fields were drier than conventional-till fields planted a few weeks earlier. "It was also a disastrous year for seeding into cover crops," says Dr. Walt Wallinglord. east central director of the PPI. Cover crops often used in no-till practices took what little moisture that would have been available to seeds.

INCREDIBLE WEED CROP

Another aspect of reduced tillage observed in Ohio fields was severe weed problems. "Where we had reduce tillage systems the weed seed population was concentrated at the soil surface," Johnson says. Weed problems erupted in fields because dryness halted surface applied herbicide action. Touchton of Alabama doesn't see a difference in weed pressures between tillage systems. "In a dry year you get a late season weed problem because when the rain comes the crop canopy is not closed. If you have an open canopy, you're going to have weeds."

To deal with weed problems in no-till fields, farmers in Kansas often cultivate after the crop is up, Lamond says. "It's no-tillage prior to planting but then use a row cultivator for weed control."

Johnson says that at local agricultural meetings farmers have voiced disillusionment with no-till and he expects no-till to receive a slight setback in Ohio. But as Johnson and researchers across the country point out 1988 was an exceptionally bad year and not a year on which to base choices of production systems on.

"Any of the tillage systems that farmers feel comfortable with will work if properly managed." Johnson emphasizes.

Touchton of Alabama suggest growers always go with the average. 'Research recommendations are not based on 1 year's response but on long-term responses. FC

HOW TO IDENTIFY HERBICIDE RESISTANCE

Herbicide-resistant weeds don't look like monsters. They don't have thorns or giant leaves. They simply survive chemical applications that kill their susceptible cousins.

Because it takes a greenhouse test to tell them apart it rnay be difficult to distinguish between weed escapes and a resistant outbreak.

"Every weed control failure you may have in the future isn't going to be due to resistant weeds," says Leon Wrage, South Dakota State University extension weed specialist.

According to a list prepared by Du Pont, poor herbicide performance sull

can be caused by many factors, including:

Poor application coverage.

Improper timing. Weeds may be too big when sprayed to be controlled.

Lack of rain. It takes moisture to activate some herbicides.

Plant stress. When under stress, weeds may not absorb herbicide.

Failure to use a needed additive.

Some herbicides give top performance only when tank mixed with surfactants or additives.

Herbicide resistance may be involved if the following conditions exist:

The same herbicide has been used on the same field for several years.

Past weed control has been very good.

Other reasons for poor performance have been eliminated.

Control is poor on only one or two weed species, but good on othe~

For example, let's say lambs-quarters, mustard and kochia had been controlled very well in the past, but now only lambsquarters and mustard are being controlled. Herbicide resistance may be involved.

Weed experts say the following four steps can help you head off development of herbicide-resistant weeds:

1) Rotate crops. Crop rotation usually means using a diverse herbicide program, making it difficult for resistant weeds to increase.

2) Rotate and tank mix herbicides. Using herbicides with different chemistry and modes of action keeps resistant weeds in check - with little opportunity to grow and go to seed.

3) Use short-residual rather than long-residual herbicides. Herbicides that last for a long time in the soil increase the selective pressure on resistant weeds. The longer susceptible types are suppressed and resistant ones allowed to grow, the more likely resistant weeds will increase enough to dominate the species.

4) Where practical, use tillage in conjunction with herbicides. The best weed management program uses a balanced variety of control methods,. including herbicides with different modes of action and tillage.

Through the years we have let plant populations creep up to dangerous levels, as can be seen by the effects of this year's drought. We need to reevaluate our strategy on the basis or the total tillage program utilized on a farm.

I will make production decisions late, depending on the rainfall this fall. We need a big charge of precipitation then to bring moisture balance back to normal next year. There's a lot of herbicide and fertilizer on top of the soil this year. The top layer needs to be cleansed.

We will be doing plenty of soil testing next year to locate fertility and dryness problems.

Despite the bad press no-till has received this year, the practice has worked well for us on corn following beans in sandy soil, perhaps because we had a very good weed-control program going into planting season. The bean stubble protected plants in the mids of dry, blowing dust tbat eroded conventionally tilled soil. We plan to use no-till more extensively next year. by. Bob Andersan

Norwest Bank

Des Moines, Iowa

MINNESOTA SCIENCE

MINNESOTA HAS UNIQUE "SUSTAINABLE AG"; SITE

"Sustainable agriculture" is a term loaded with positive meaning, like "organic farming" and "health food." The University of Minnesota Agricultural Experiment Station is expanding its sustainable agriculture research, especially on a unique site at the Southwest Experiment Station, Lamberton.

Sustainable agriculture is a term claimed by many philosophies of farming. For the University, Kent Crookston, experiment station agronomist and director of the university working group on sustainable agriculture, says it represents approaches and techniques ranging from totally organic to modified safe chemical use. The goal is agriculture that will be acceptable now and into the future, allowing long-term profitability.

Crookston notes that anything not profitable for farmers in the long term will not be accepted, and farming practices that can't sustain the farming environment will, by definition, eventually put the farmer out of business.

Experiment station researchers and outside consultants representing organizations involved in sustainable agriculture have been working on a preliminary model to direct research on the "Koch farm" being leased by the University. The consultants include representatives from the land Stewardship Project, which helps farmers change to a more diversified agriculture sys:em; the Rodale Research Center, a leading national advocj'te for organic farming; and Winrock International, sponsor of international agricultural projects in nine countries.

Crookston says there is wide national interest about the Koch farm property. Nowhere else in the nation is there as large a property with such nearly natural levels of soil nutrients, and as convenient a location for research.

The Koch farm is directly across the road from the well established Minnesota Agricultural Experiment Station at Lamberton. It has had very few chemical inputs over the past quarter century. For instance, phosphorous levels closely approximate what's found on patches of native prairie, Crookston says. It's a unique opportunity to pursue agricultural questions in natural, unenhanced soil.

The Koch farm has other unique aspects as a research site. There is no drainage tiling, and it has never been deeply tilled. The near natural levels of phosphorous and potassium are not duplicated at any experiment station in the nation.

With the operational framework for Koch farm research now laid out, detailed planning has begun. Staggered crop rotations are likely so every crop will be available for study in any given year, Crookston says. Some of the acreage will also be held for future experiment opportunities.

Richard Harwood, of Winrock International, Arkansas, said there is a need to recognize agriculture as being a biologically structured system. "We obviously need to know more about nutrient flow and nutrient and chemical interactions," he said. We need to recognize that there's often a greater availability of nutrients than soil tests indicate, and we need to study much more closely the rotation effect of cool season and warm season crops as an approach to biological weed control, he said.

-Larry A. EtkinThis weed infestation at the Southern Experiment Station, Waseca, is part of a series of experiments testing biological controls. Rye, the tan stand, is being tested because it inhibits weed seed germination.

8 WAYS TO SAFEGUARD GROUNDWATER

Where the presence of agricultural chemicals has been detected in groundwater. the culprit has more often than not. been mishandled chemicals on the farmstead which resulted in entry near or through the well. Experts interviewed in compiling this report agree that following these 8 steps drasticallv reduce the chances that farm chemicals would ever show up in ylour groundwater:

1. Mix nd store chemicals at least 50 ft. from vour a well. Some states recommend as much as 200 ft. as a buffer zone between your mixing/storage area and your well. "It's not always obvious where things will flow after a spill." says Mike Hirsehi, agricultural engineer at University of Illinois. Subsequent rains can wash chemicals further than you might think. Maintain the same buffer zone between your mixing area and any surface water such as ditches. ponds. or slues.
2. Prevent back-siphoning by installing backflow devices such as check valves on the fill pipe between your water source and your sprayer. Pumps don't prevent backsiphoning. A drop in voltage or uneven water supply can cause many pumps to "cough" and allow chemicals down the well.
3. Store chemicals in a well-ventilated. cool location. preferabjy with a concrete floor slanting inward. A 12-inch-high retaining wall around the outside will contain spills. Always store chemicals in the original. labeled container. Make sure they're tightly sealed.
4. Triple rinse or pressure-rinse containers to prepare them for disposal. and sprav the rinse later back on the field. Rinse containers as soon as they're emptied so the residue doesn't have a chance to dry out
5. Make sure your sprayer is attended throughout period during which it is being filled. and keep the filling hose above the water level in the tank at all times. Mount a clamp on top ofthe tank to hold the hose if necessarv.
6. Study the labels for each material you apply. only do they contain information on rates of application, but they list recommendations for safe disposal. Labels are frequently revised and expanded.
7. Plan carefully your purchases and required inventory ofchemicals fora given crop year. Calculate needs carefully and buy just what you need. Avoid overwintering chemicals wherever possible. Keep records of total amount, rates and dates and type of chemical applied on each field.
8. Inspect your well periodically. Pollutants can enter directly from the surface, through openings in or beneath the pump base, or through soil next to the well. You need to have tight seals between the pump and pump base as well as between the casing and the wall of the bore hole. The pump itself needs to be checked for leaks. Know the locations of old wells, and make sure they are capped.

WEEDS BECOME RESISTANT TO HERBICIDES: SPECIALIST

FARGO - Weeds resistant to herbicide used to control them are a potential new problem for North Dakota farmers, according to Dallas Peterson, extension weed control specialist at North Dakota State University.

Herbicide resistance, Peterson said, occurs when a weed becomes tolerant to a chemical to which it was previously susceptible. While this has previously been a problem in other parts of the country, he said now kochia populations resistant to Glean have been confirmed in the state, while resistant Russia thistle and prickly lettuce populations have developed elsewhere.

Peterson said resistance to a herbicide can develop Iwben weeds that contain a low frequency of genetically resistant plants are continuously exposed to the chemical; while the herbicide controls the susceptible plants, the frequency of resistant plants gradually increases. Poor weed control doesn't necessarily indicate development of a resistant weed population for other factors influence weed control, such as amount of herbicide applied, stage of growth of the weeds and environmental conditions at applicauon, Peterson said, but ineffective control with a herbicide that has done a good lob in the past may indicate resistance.

Factors which can contribute to development of herbicide resistant weeds include repeated use of a herbicide or use of chemicals that have the same mode of action, using highly effective herbicides that give nearly complete control of susceptible plants by affecting a single metabolic process, a high turnover rate, limited lseed dormancy in a species and a diverse weed populations with plants that have the genetic trait of resistance.

Resistance of kochia and Russian thistle to Glean confirms to this scenario, said Peterson. Glean, a very persistent herbicide often remaining in the soil for two to three years, is the most cost effective treatment for broad-leaved weed control in continuous wheat and wheat-fallow-wheat production systems.

Glean, he said, controls weeds by acting on a specific enzyme site and is very effective against kochia and Russian thistle, but both weeds are highly variable with many different biotypes.

Kochia resistant to Glean developed in fields where Glean was used continuously for four to five years, according to Peterson. He said native kochia populations are estimated to contain about one resistant plant per million susceptible plants and resistance gradually becomes more predominant.

Weeds which are resistant to Glean also have increased tolerance other other chemicals with the same mode of action, including the suuonylurea herbicides, Ally, Harmony, Express, classic, Amber and Oust, and the imidazloinone herbicides, Assert, Scepter, Pursuit and Arsenal, and several new experimental herbicides.

Development of weeds resistant to herbicides with this mode of action could have a profound effeclt on development of new herbicides, Peterson said.

Buildup of resistant weed populations he said, can be minimized or prevented by using alternative methods of weed control to reduce the selective pressure for resistant types, including crop rotations, integrated pest management, avoiding repeated herbicides that have the same mode of action, using combinations of herbicides that have different modes of action and preventmg the spread of resistant weeds to new area.

Glean, Ally and Harmony labels are heing modified to use these techniques for avoiding buildup of herbicide resistant weeds, said Peterson, and the revised labels will limit the frequency of applications and emphasize tank mixtures with other herbicides.

Failure to follow the label guidelines where resistance has occurred, he said, may eventually lead to loss of the effectiveness of otherwise useful herbicides.

Dallas Peterson

Extension Weed Control Specialist

North Dakota State University

Fargo, N.D.

December 1988