Joseph F. Giles, Allan W. Cattanach and Norman R. Cattanach
Associate Professor, Department of Soil Science, North Dakota State University
Extension Sugarbeet Specialist, North Dakota State University-University of
Minnesota and Research Specialist, Department of Soil Science, North Dakota
State University
Changes in farming methods, which include field equipment such as large four-wheel tractors with increased horsepower and dual tires for better traction, have caused increased concern over soil compaction.
In the North Central states, both current and past research results evaluating the effects of subsoiling have shown few positive yield responses. However, these studies to present have been from a limited number of soil and climatic conditions and their results are considered indicative rather than conclusive.
One strong possibility for the lack of response to subsoiling is the detrimental effects caused by compaction may no longer be limiting crop yield.This may occur either because differences in crop or climatic conditions, such as rainfall, alleviate the effects of compaction or because the detrimental effects do not persist and may decrease with time, as often occurs. In such a case it is difficult to determine whether subsoiling improves the situation.
In any subsoiling operation the effectiveness and permanency depends in large part upon the moisture conditions in the soil. Unfortunately, in soil which needs subsiding, there is frequently a variation of moisture at different depths because of dense layers. If the soil is sufficiently moist,it will flow plastically around the tool compacting instead of shattering.In general this plastic reaction is considered to be detrimental to the soil and experience indicates that in this case the subsoiling operations likely will not give beneficial results.
In recent years, the amount of subsiding by producers has increased in eastern North Dakota and western Minnesota. The crop response reported has been varied and in may cases not quantified. Considering the disadvantages of deep tillage: the use of high power and time requirements;the possibility of short-lived effects, particularly on highly compactible soil; and in some instances, the undesirable mixing of soil horizons,sugarbeet producers have requested a scientific evaluation of the potential benefits.
A subsoiling study initiated in the fall of 1991 was continued during the fall of 1992 and growing season of 1993. Deep tillage was performed following 1992 small grain harvest on Fargo silty clay (Fine,montmorillonitic, frigid, Vertic Haplaquoll) and on Glyndon silt loam (Coarse silty, frigid Aeric Calciaquoll) with a Blue Jet straight shank ripper and Tye Paratill implements. Depth of tillage was 17 inches. Soil conditions were dry at the time of tillage. A conventional tillage, fall chisel plow treatment was included as a check.
Hard red spring wheat ('Gus') and sugarbeets (KW 1119) at both locations) were planted perpendicular to the direction of deep tillage following seedbed preparation with a field cultivator in the spring. The two crops were rotated on the deep tillage treatments of 1992;, in. sugarbeets were grown on the previously deep tilled spring wheat treatments and wheat on the old sugarbeet treatments. Wheat plots were planted in the first week of May and harvested during the third week of August. Planting of sugarbeets occurred during the first week of May and harvesting in the second week of September. Sugarbeet quality analysis was performed at American Crystal Sugar Quality Tare Lab, East Grand Forks, MN.
Soil bulk density measurements were taken in the conventional tillage treatments in the fall of 1992 and during the growing season in all treatments for both deep tillage years in 1993. A three inch core was extracted to a depth of 21 inches and partitioned in to three inch depth increments.
The effect of deep tillage on the production of sugarbeets and spring wheat the year of deep tillage and the year following deep tillage for the Glyndon silt loam and Fargo silty clay soil types is shown in Table 1 and Table 2, respectively. Although a large amount of fracturing of the soil profile occurred during deep tillage operations both years, the soil loosening did not significantly change crop production on either soil type during either treatment year. Soil moisture conditions throughout the growing season each year did not cause moisture stress in either crop in any of the treatments. In fact, the excess moisture conditions in 1993 were not relieved to any extend by the deep tillage treatments. These results are in agreement with those from other tillage studies conducted in the Red River Valley: soil compaction with four wheel drive tractors and loaded trucks, deep tillage under potato, corn,soybean and sunflower prior to and following planting.
The second year of the rotation for the 1993 crop will be completed during the 1994 growing season.
Appreciation is expressed to the Sugarbeet Research and Education Board of Minnesota and North Dakota for grant funds, American Crystal Sugar for sugarbeet quality analysis, and Grand Forks Equipment and Horvick Manufacturing Company for providing the deep tillage equipment.
1993 Sugarbeet Research and Extension Reports. Volume 24, pages 256-258.
