ISSUE 6   June 8, 2000

    Number of calls in recent days have been on the question of applying liquid sulfur with herbicides for grass control in canola. John Lukach, agronomist at the Langdon R/E Center stated emphatically that ammonium thiosulfate should not be used with Poast or any herbicide product requiring oil additive. The combination will burn the crop severely. Even products using extra surfactant that might thin the cuticle should be avoided.

    The larger the canola is prior to bolting the less damage although it still may be very severe and can reduce yields. Best option is to apply the ammonium thiosulfate first with water and then to apply the grass herbicide plus oil several days later. This would reduce the chance of cuticle damage or removal resulting in less fertilizer burn. Usually 3-5 gallons of liquid sulfur is applied per acre mixed with 15-17 gallons of water to bring the total to 20 gallons per acre to reduce the risk of fertilizer burn.

ANALYZING AND EVALUATING CROP PROBLEMS

    Persons working in crop production are often called upon to trouble-shoot in situations involving suspected crop injury from herbicides. These situations require careful analysis and scouting before judgements are formulated. For purposes of this discussion, I would like to define "injury" as stunting, delayed development or malformation of plant tissues which may or may not affect yields. Herbicide injury may result from applications to the crop, from residues in the soil or from drift.

    When evaluating crops involved in suspected herbicide injury, keep in mind that some other factors may have caused the observed effects or the herbicide may be only one of a combination of several casual factors. Look for other possible causes. Are there holes in the leaves or stems or pruned roots from insect damage? Has there been severe weather - wind, drought, hail, flooding, frost, high temperatures, etc. - that could have caused damage, Flooding damage in crops which recently
occurred, greatly compounds the diagnosis. Could a disease be involved? Could it be excessive or misplaced row fertilizer or a nutrient deficiency? Or is the effect resulting from a combination of causes?

    Look for patterns of injury in the field. Herbicide injury is often in a pattern associated with soil types or movement of application or incorporation equipment. Observe other susceptible crops or weeds in the area for herbicide effects. For comparison, try to find a check area where no herbicide was applied in the same field.

    If you conclude that herbicides are the probable cause of crop injury, try to determine why the injury occurred. Limited crop tolerance to certain herbicides is sometimes a problem especially under heavy rainfall or sandy soils or on dry, loose soil. Misue - high rates, wrong chemical, improper method of application, nonuniform application, overlaps, improper applicator adjustments and tillage operations that concentrate the chemical - are some reasons for herbicide injury. Some varieties/hybrids are more susceptible than others. Weather and soil conditions that cause plant stress may make the crop more susceptible to herbicide injury.

    Don’t be too hasty to evaluate the effects of herbicide injury. Give the plants a chance to recover. Check growing points to see if the plants have potential for recover. Compare injury effects and weed control benefits. Stand counts and injured plant counts are important considerations. Unbiased yield checks in affected and unaffected similar areas of the same field are the best estimates.

    Determining the growth stages of canola is relatively simple using a scale developed in Canada. This scale uses five principal stage designations and subdivides these into secondary stages. These stages are described below:

    With the new herbicide tolerant canola’s one has to pay special attention to plant stage for last application. For the Roundup Ready canola, application can be made from seedling emergence to start of bolting (3.1 to 3.2). For Liberty Resistant canola, the application can be made from seedling stage up until early bolting stage (3.2). For Clearfield canola varieties, Raptor application can be made up to just prior to bloom.

    Canola in the 5.3 to early 5.4 stage should be near or at swathing stage. These stages change very rapidly during the ripening period if temperatures are warm and under dry conditions.

Duane Berglund, PhD
Extension Agronomist
dberglun@ndsuext.nodak.edu

BYDV IN WINTER WHEAT

    I observed symptoms of barley yellow dwarf virus (BYDV) on winter wheat south of Lisbon last week. The virus was confirmed by the plant diagnostic lab this week.

    In this case there were two large patches of stunted wheat. Yellowing was not as severe as typically observed.

    A close inspection of the field revealed aphids were not present. This leads me to believe that the infection occurred last fall.

    Considering the multiple cases of BYDV that have been reported locally and the severe infections in the southern plains there is increased potential of a problem developing here. Marcia McMullen and Phil Glogoza have both suggested vigilant scouting for aphids, I belabor the point because the potential of a widespread problem is real.

Michael D. Peel
Extension Small Grains Agronomist
mpeel@ndsuext.nodak.edu

CORN PLANT ADAPTS TO PHOSPHORUS LIMITATIONS AT THE EXPENSE OF YIELD

    Phosphorus deficiency can show up on corn plants mildly as when cool temperatures limit uptake by the plant causing purpling or reddening of leaves or the deficiency can be a major problem in cornfields where supply is limiting. In the true deficiency case, the lack of phosphorus can decrease plant biomass accumulation thus limiting interception of light that then limits energy to the plant that can then ultimately limit yield. Phosphorus deficiency has been shown in recently reported research to slow the rate of leaf appearance and to reduce the final area of leaves, especially leaves located below the main ear by 18 to 27%. It also slowed the senescence rates (affecting reallocation of assimilates or storage compounds from the leaves to the ear) of these lower leaves by 29%. Plant senescence rate during most of the grain filling for the plant was reduced by 15 to 33% under the phosphorus-stressed conditions. And, leaf area duration from emergence of the corn plant to complete senescence was reduced by 13.5%. The effects of early, severe deficiency of phosphorus in the corn plant were very detrimental to yield. Early limitations on leaf area accounted for most of the 7 to 10% reduction in light absorption on the plant that was observed as soon as canopy development allowed maximum light interception. The senescence dynamics of the upper
leaves above the ear, however, were not greatly affected by changes in phosphorus availability. Despite a wide range of soil phosphorus concentrations tested over three years in the research, leaf growth and decline of the corn plant was still less responsive to phosphorus than to nitrogen deficiencies. Early sensitivity of maize growth to phosphorus limitation has been previously reported and these results along with those of this new research suggest that phosphorus plays a key role in leaf size and expansion processes that occur in early corn development.

RECORD YOUR ROTATION AND CHEMICAL COSTS TO MAXIMIZE PROFITABILITY

    A six year study at Cornell University was run to determine profitability of cropping systems in four crop rotations with cash economics used to determine the best system. The four rotations tested were continuous corn, soybean-corn, soybean-corn-corn, and soybean-wheat/red clover-corn. The rotations were tested in three tillage systems: moldboard, chisel and ridge. Also, two management input systems were used: a high and a low chemical use. Under low chemical management, the soybean-corn rotation resulted in the greatest net returns under chisel ($40) and moldboard plow tillage ($60) due to reduced production costs (about $45) from less fertilizer and pesticides used in corn and less herbicides used in soybeans. The gross returns on the tillage systems were at $29 in chisel and $15 in moldboard plow. Similar returns on three of the systems were seen in the ridge-till operations. Continuous corn under high chemical, and soybean-corn-corn as well as soybean-corn under low chemical management netted $13, $11, and $7 respectfully. Growers who used moldboard plowing realized their maximum profits by adopting the soybean-wheat/red clover-corn rotation under a low chemical management practice, if they marketed the wheat straw also. Reducing chemical costs for fertilizer, herbicide and insecticide use under the low chemical management greatly reduced costs in the systems. Corn in the study gained more in total returns due to the demand for corn by the dairy industry in the northeastern states such as New York. However, these studies showed that growers could increase corn yields while reducing input costs by adopting the soybean-wheat/red clover-corn and the soybean-corn rotations in either moldboard plow or in a soybean-corn rotation in chisel tillage. In ridge-tillage, corn yields could be increased in either the
soybean-corn or the soybean-corn-corn systems but this would not reduce input costs when compared with continuous corn in the lucrative corn market for the region. Read more on the rotation, tillage and input comparisons for this research in the latest "Agronomy Journal," volume 92, number 3 on pages 485-493 and on pages 493-500.

Denise McWilliams
Extension Crop Production Specialist
dmcwilli@ndsuext.nodak.edu