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Research Report  2.4

Determining the Factors Responsible for, and Methods
to Overcome the Limitations of Conservation Cropping Systems on Clay Soils

T.J. Vyn and C.J. Swanton,
Department of Plant Agriculture University of Guelph,
Guelph, ONT, N1G 2W1
COESA Report No.:  RES/FARM-004/97

Objectives & Expected Outputs
Executive Summary  

View / Download Report   [637 KB pdf]


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Objectives and Expected Outputs
Objectives: To establish essential seed-bed criteria for good crop emergence and growth on clay soils and to define tillage strategies which will enable these criteria to be met under conservation cropping systems where the rotations are corn-soybeans and wheat-soybeans or wheat-corn. The test crop will be corn or soybeans in each case.
Expected Outputs: The combinations of tillage will include the moldboard plow, chisel plow, mulch-disc and zone tillage. The major soil measurements will be residue cover at planting, soil temperature, soil moisture in the seedbed, penetrometer resistance of the seed bed, soil aggregate size, soil bulk density, soil macroporosity, rainfall simulation (time to ponding), crop emergence, early crop biomass and grain yield. In-sights into the problems inherent in clay soils, and strategies for overcoming them by more efficient conservation tillage is anticipated.
Type: Contribution Agreement, University
Spending Profile: 93-94: $67.8 K,  94-95: $85.6 K,   95-96: $84.9 K,    96-97: $83.2 K,    Total: $321.5 K
Status: Available March 1998


Executive Summary

Thirty field experiments were conducted in South Western Ontario on clay textured soils to examine the effects of up to eight tillage systems on:

  1. rates of spring seedbed dry-down,
  2. in-row seedbed physical properties,
  3. corn and soybean yield following wheat or in a corn-soybean rotation, and
  4. weed seedbanks.

The effect of selected weed management strategies on no-till soybeans planted on clay textured soils was also examined. Each experiment was conducted from 1994 to 1996 at two farm locations; conclusions below are based on six site-years of data.

**No-till corn yields following soybeans were not significantly different from yields after moldboard plowing at five of six sites when the corn planter was equipped with a 5-cm fluted coulter in addition to one fertilizer coulter and one residue removal attachment per row.

**Slot no-till (tined row cleaner and fertilizer coulter only) corn yields following soybeans were as much as 10% lower than those obtained in the moldboard system at three out of six sites. At those sites, less intensive tillage systems such as fall zone-till or field cultivation just prior to planting resulted in corn yields that were greater than no-till (slot or coulter) and similar to those obtained in the moldboard system.

**Chisel plowing soybean stubble was a poor conservation tillage choice on clay soils since it resulted in low residue cover, relatively coarse seedbeds and corn yields no better than those with the no-till (coulter) system.

**Narrow-row (38 cm) soybean yields were only marginally affected by tillage systems following corn in rotation. On silty clay loam soil, average yields for no-till were virtually identical to those obtained with either moldboard or chisel plowing. On a less productive clay soil, no-till yields were slightly less (0.17t ha-1) than with moldboard plowing, but similar to yields obtained with the other alternative tillage systems evaluated.

**No-till planting into winter wheat stubble (after baling) lowered corn yields by 0.66 t ha-1 (7%), relative to those with fall moldboard plowing. Fall discing or fall zone-tilling resulted in corn yields that were essentially similar to those obtained with either moldboard or chisel plowing and at least 0.49tha-1 (5%) greater than no-till.

**No-till planting soybeans in wide rows (76 cm) into baled wheat stubble resulted in average yields 0.31t ha-1 (9%) lower than with moldboard plowing. Fall discing resulted in average yields that were greater than no-till, but not consistently equivalent to those obtained with moldboard plowing.

**No-till yield potential was affected by the amount of wheat straw present. Totally removing all wheat straw increased no-till yields, relative to where straw had not been baled, by 0.88 t ha-1 (10%) for corn (average of 1994-96) and 0.46 t ha-1 (17%) for wide-row soybeans (average of 1994-95). Baling wheat straw (i.e. leaving stubble of 20 to 30 cm) also increased no-till corn and soybean yields in most site-years. When all straw was removed, no-till corn and soybean yields were usually similar to most of the fall tillage systems evaluated.

**Regardless of the preceding crop (i.e. corn, soybeans or wheat), shallow fall tillage using zone tillage or tandem disc usually resulted in spring soil dry down rates (at least for the intended row area) that were faster than no-till and often similar to fall moldboard plowing. Fall zone tillage also resulted in finer aggregates and higher soil temperatures after planting than no-till systems.

**Spring-killed rye cover crops did not enhance weed control in no-till soybean production systems.

**A combination of preplant glyphosate followed by broadcast preemergence applied imazethapyr plus metribuzin was the most profitable weed control treatment when no-till soybeans were grown in narrow rows (18 cm). However, use of the glyphosate burn-down treatment alone provided 83% of the weed control, 85% of the maximum potential yield and 98% of the maximum potential profit for no-till narrow-row soybeans.

**An integrated weed control strategy using banded preemergence herbicide plus inter-row cultivation reduced herbicide use by 60% and was the most profitable treatment for no-till wide-row (76 cm) soybean production. However, substantial reduction in yield potential associated with wide-row soybean production made this practice considerably less profitable ($98ha-1 ) than the most profitable treatment in narrow rows.


Technology Transfer

Both preliminary and - after 1996 - final conclusions from this research were presented:

  1. at over 15 extension events (ranging from field days to symposiums to agricultural conferences in Ontario),

  2. in over 10 articles in the farm press,

  3. in five peer-reviewed papers in scientific journals and

  4. in two Ph.D. theses (1 completed and 1 in progress).


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