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Results of Funded Research

Yield Potential and Long Term Effects of No-Tillage on Wheat Production

Lloyd Murdock
James Herbek
Jim Martin
John James
Dottie Call
University of Kentucky

1999-2000 Report

INTRODUCTION
The objectives of this experiment are to see if high yields can be produced by no-till wheat and to see if no-till wheat is an economical alternative compared to conventionally planted wheat. The second objective is to watch the effects of the wheat tillage treatments on succeeding crops and on the long-term soil effects.

This year's wheat yields were excellent with almost no problems during the growing season.


TILLAGE
There were no differences between the yields of no-tillage and conventional planted wheat this year. The yields were very high in both cases.

The eight-year average is 4.3 bu/ac greater with conventional tillage planting

NITROGEN RATE
Nitrogen was managed for intensive production with 1/3 of the N applied at Feekes 3 and the remainder at Feekes 5. The rate of nitrogen had no effect on the yields with either of the two tillage systems. The 90 lb/ac rate was good as the 120 rate.

The rain during the winter was below average, so we probably did not lose as much nitrogen and had more available than years with above average rainfall. The 90 lb/ac nitrogen has been as good as the 120 lb/ac nitrogen rate 5 of the 8 years.

NITROGEN TIMING ON NO-TILL WHEAT
In 1996, a split N application of 60-60 in February and March was a better combination than the 40-80 split. To look at this nitrogen timing in more detail, several treatments with different timings were added.

The 0-60-60 (Fall-Feb.-March) treatment has been similar to all the other treatments in 2000. The 30-45-45 treatment was lower than the 0-40-80 treatment. The fall N treatments were not helpful this year.

The four-year average show that the fall N application treatments tended to yield a little less than the ones with only the spring split.

WEED CONTROL
On April 20, 2000 weed control was evaluated based on the percent ground cover occupied by weeds in the row middles. Henbit (Lamium amplexicaule), and common chickweed (Stellaria media) were the dominant weeds observed. Other species noted in the spring included catchweed bedstraw (Galium aparine), field pansey (viola rafinesquii), field pepperweed (Lepidium campestre), hairy bittercress (Cardamine hirsuta), sibra (Sibra virginicus), star-of-Bethlehem (Ornithogalum umbellatum), yellow woodsorrel (Oxalis stricta).

The overall weed control observed in conventional till wheat with spring Harmony Extra was essentially equal to that found in no-till wheat with fall applied Gramoxone Extra followed by spring applied Harmony Extra. The infestation levels of hen bit and common chickweed tended to be less when Harmony Extra was applied in the fall compared to when it was applied in the spring. Plots treated in the fall with Sencor at 4 oz/A had very little henbit or chickweed but did not have other weeds, particularly catchweed bedstraw.

Wheat yields for all weed management practices exceeded 90 bushels per acre in 2000. The yields of plots receiving a herbicide treatment were similar and were at least 4 bu/A greater than the yields of no-till wheat where no herbicide treatment was used. The eight-year averages for wheat yield tended to be less with Harmony Extra applied in the spring compared to other weed management practices, however, this trend was not observed in 2000.

FUNGICIDES AND DISEASES
Fungicide applications were managed for intensive production on all treatments and there were no differences observed in disease among the treatments.

INSECTS
Insect pests were not a significant factor on this test this year. Plots were monitored weekly for the presence of insect pests including aphids, cereal leaf beetle and armyworm. However, no populations of any importance developed. To prevent Barley Yellow Dwarf, Warrior was sprayed 30 and 60 days after planting.

WHEAT STANDS
The fall stand counts over a seven-year average show about 10% less plants in the no-till plots as compared to the conventional plots when planted at the same rate. This year, stand counts were high in both tillage methods, but no-till was 15% less than the tilled method of planting.

WHEAT HEAD DENSITY
Head counts made at maturity were significantly higher for the no-till planting. The numbers of heads/ft2 were in the range where high yields might be expected for both tillage treatments. It appears that the wheat plant with no-tillage tillered more than the conventional wheat since fall stands were lower with no-tillage.

LONG-TERM SOIL EFFECTS
The plots have been in the same treatments long enough that differences in the soil physical and chemical characteristics may begin to separate according to tillage treatment.

Soil Physical Factors:
There appears to be little difference in the soil physical factors between the two tillage systems as determined by the measurements that were made (Tables below). The soil densities for both systems were very similar and were in excellent condition for crop growth. The soil strength measurements were all low enough and were in the range for excellent crop growth. The 0-3 and 3-6 inch depths showed higher soil strength in the no-tillage treatments, but the measured values should not affect crop growth. The higher soil strengths reflect a stronger and well established soil structure in no-tillage that allows trafficking of the plots when it is possible in the tilled plots under wetter conditions.

* Soil strength was significantly higher than conventional at this depth.

Soil Chemical Factors:
Organic matter is higher with no-till wheat in the 0-3 inch depth, but lower at the 3-6 inch depth. Overall, the no-till wheat treatment had significantly more organic matter.

There was a small, but significantly lower pH in the top 3 inches of the no-till system. This is to be expected since all the nitrogen is placed on the soil surface and the nitrogen acidifies the soil. The tilled plots mixed and diluted this effect. There were no differences in the phosphorus and potassium soil tests between the two systems.

Yields of Succeeding Crops (Soybeans and Corn):
Both soybeans and corn are no-tilled after the two tillage systems in which wheat is grown. The soybeans are double-cropped after the wheat and the corn is planted the next spring before the wheat is planted in the fall. These crops are harvested for yield to determine if the wheat tillage systems have an effect.

At this time, it appears that both corn and soybeans tend to yield more where the wheat was planted no-till. The soybeans averaged 1.1 bu/ac (3.3%) more after the no-till wheat. The differences are consistent but not significantly different. The corn averaged 16.5 bu/ac (8.9%) more after the no-till wheat. The differences are consistent but not significantly different.

Although the cause for the differences in yields between the two systems is not known, it is probably related to soil water availability.

SOIL MOISTURE

The reason for higher yields of no-till soybeans and corn grown after no-till wheat is not known at this time. There are a number of changes which take place in the soil with a true no-tillage system. It is felt that these changes would alter the amount of water available to the plant. To better understand this, the amount of water in the top 12 inches of soil was monitored in the no-till corn during the late vegetative and early reproductive stages of growth. The results are found in the following table. Significantly more water was found at each date of sampling with the true no-tillage treatment. The moisture on June 24 was similar due to a heavy rain. However, the moisture declined in the true no-till treatment at a slower rate indicating that the moisture was more efficiently used in the true no-till treatment.

Research is expanding to better understand the reasons for the difference in yield.

TEMPERATURE AND WHEAT GROWTH
Temperature loggers were placed at different heights and depths within the soil and wheat canopy to develop a temperature profile that might help answer questions concerning the differences between tilled and no-tilled wheat on growth vigor and winterkill.
In 1998-99, there was no difference in the vegetative growth between the 2 tillage systems and there was also little difference in temperatures most of the time.
The temperatures in both tillage systems declined in December at the same rate and began rising in late January at the same rate.