무경운 농법의 생산성 실험

A tillage study was established in 1981 at the University of Nebraska Rogers Memorial Farm (RMF), 10 miles east of Lincoln, to gain experience with various tillage systems. These dryland research and demonstration plots are showing that long-term continuous no-till builds soil structure, usually has the highest yield, and is the most profitable.  Located on a sloping, upland silty clay loam soil, they were started as a soybean/grain sorghum rotation common to southeast Nebraska at the time.

In 2005, one set of plots was switched to a corn/soybean rotation. The other set was switched to corn/soybeans in 2007.  Since 2007, a cover crop has been drilled after harvest on both a tilled (single disk in the past) and no-till treatment (no-till with cultivation in the past).  The yields shown below are combine harvest, weighed, and corrected to standard moisture content for each crop.

 

Rogers Memorial Farm - Soybean Yields, bu/A

Tillage System	2000	2001	2002*	2003	2004	2005	2006	2007#
Plow, disk, disk	23.2	44.6	10.9	38.2	65.3	48.3	43.2	48.4
Chisel, disk	36.2	44.7	15.5	38.3	65.1	51.2	55.7	51.6
Disk, disk	36.1	44.8	15.6	37.0	66.6	50.0	56.2	51.8
Disk	41.8	44.2	17.1	38.6	67.6	49.5	58.9	49.7
No-till w/cultivation	43.8	42.5	16.8	41.4	65.1	55.4	61.5	51.9
No-till	47.7	50.0	17.8	44.1	68.3	59.2	62.0	54.2

* Severe hail on August 28, 2002 reduced yields greatly.

# None of the plots were cultivated in 2007.  It is interesting to note the yield reduction on the no-till plot that was cultivated in the past (1981-2006).

 

Rogers Memorial Farm - Grain Sorghum Yields, bu/A

Tillage System	2000	2001	2002*	2003	2004		2006
Plow, disk, disk	61.2	120.0	34.8	123.0	152.8		92.1
Chisel, disk	76.2	115.8	41.8	119.6	143.6		90.2
Disk, disk	78.4	120.1	42.9	110.3	144.7		90.1
Disk	74.0	116.2	42.0	121.5	150.5		91.3
No-till w/cultivation	107.7	121.2	48.8	124.2	148.4		93.7
No-till	121.4	124.1	64.6	128.3	129.9#		99.6

 * Severe hail on August 28, 2002 reduced yields greatly.

# Sandburs invaded the plots in 2004, tracked in from borders.  The row crop cultivation in the other treatments reduced the resulting weed competition.  The no-till yield was 146.1 bu/A for the rep without the sandbur control problems (away from the borders).

 

Rogers Memorial Farm - Corn Yields, bu/A

Tillage System	2005		2007*
Plow, disk, disk	183.6		132.4
Chisel, disk	185.7		132.5
Disk, disk	187.6		134.8
Disk	194.3		134.8
No-till w/cultivation	181.1		133.7
No-till	190.6		142.1

* None of the plots were cultivated in 2007.  It is interesting to note the yield reduction on the no-till plot that was cultivated in the past (1981-2006).

 

Cover Crop Added to Existing Study

Since 2007, a cover crop has been no-till drilled after the harvest of both the corn and the soybeans.  Cereal rye was used as a single species cover crop in the falls of 2007 to 2009.  Cereal rye and winter peas have been used in a 50/50 blend since the fall of 2010 as the cover crop. 

In the spring, the growing cover crop in the no-till with cover crop treatment for corn is sprayed with glyphosate or Lumax about two weeks before planting.  About the same time, a single pass of a tandem disk is used on the growing cover crop in the disk with cover crop treatment for both the corn and the soybeans.  A second pass with the disk is made a couple of days before planting to finish seedbed preparation and kill any remaining cover crop. 

The growing cover crop in the no-till with cover crop treatment for soybeans is sprayed with glyphosate either before planting or after the beans emerge, but before the rye heads.  Above is a photo taken shortly before planting the soybeans into the corn residue showing the cereal rye cover crop.  For both crops, a residual herbicide with 2,4-D for winter annual broadleaf weed control (no glyphosate burndown) is applied to all the tillage treatments several weeks before planting.  Row crop cultivation is no longer used on any of the treatments.

 

Rogers Memorial Farm - Corn Yields, bu/A

Tillage System	2008	2009	2010	2011	2012#
Plow, disk, disk	214.1	214.4	198.2	190.1	81.6
Chisel, disk	222.8	205.5	197.1	187.8	87.5
Disk, disk	218.6	209.7	200.6	188.9	86.3
Disk w/cover crop	211.1	214.0	202.9	188.9	81.6
No-till w/cover crop*	214.3	209.8	205.2	190.1	85.1
No-till	227.8	234.8	207.6	197.1	92.1

* Row crop cultivation was performed on this treatment from 1981 to 2006.  This may explain some of the yield difference compared to the continuous no-till treatment without a cover crop.  (See the 2007 yield results above.)

# Severe drought

 

Rogers Memorial Farm - Soybean Yields, bu/A

Tillage System	2008	2009	2010	2011	2012#
Plow, disk, disk	49.0	48.2	57.5	44.6	32.7
Chisel, disk	50.5	50.8	55.4	46.2	33.7
Disk, disk	49.1	51.8	56.5	40.0	38.0
Disk w/cover crop	50.2	49.0	55.2	41.8	34.9
No-till w/cover crop*	54.4	54.0	51.4	47.9	42.2
No-till	53.8	54.3	51.4	48.5	41.2

* Row crop cultivation was performed on this treatment from 1981 to 2006.

# Severe drought

Table 1. Advantages and Disadvantages of Selected Tillage Systems
System	Major advantages	Major disadvantages
Plow	Suited for poorly drained soils. Excellent incorporation. Well-tilled seedbed.	Major soil erosion. High soil moisture loss. Timeliness considerations. Highest fuel and labor costs.
Chisel	Less winter wind erosion from roughened surface. Well adapted to poorly drained soils. Good incorporation.	Little erosion control. High soil moisture loss. Shredding may be needed for residue flow. Medium fuel and labor requirements.
Disk	Less erosion with more residue. Well adapted for well-drained soils. Good incorporation.	Little erosion control with more operations. High soil moisture loss. Destroys soil structure. Compacts wet soil.
Ridge Plant	Excellent for furrow irrigation or poorly drained soils. Ridges warm up and dry out quickly. Well suited for organic production.	No incorporation. Must be annual row crops. Wheel spacing and other machinery modifications may be needed. Creating and maintaining ridges.
Strip-till	Tilled residue-free strip warms quickly. Injection of nutrients into row area. Well suited for poorly drained soils.	Cost of preplant operation. Strips may dry too much, crust, or erode without residue. Not suited for drilled crops. Timeliness in wet falls. Possible RTK guidance costs
No-till	Excellent erosion control. Soil moisture conservation. Minimum fuel and labor costs. Builds soil structure and health.	No incorporation. Increased dependance on herbicides. Slow soil warming on poorly drained soils.

Soil & Water Management: Soil Structure

Soil is much more than the individual particles of sand, silt, and clay. Ideally, the soil should be one-half solid materials (sand, silt, clay, nutrients, minerals, organic materials, and biological life) and one-half pore space (half of that containing water and the other half being air space). Biological life and organic matter provide the "glues" to create soil aggregates, forming soil structure.

A healthy soil is one with good aggregation, where stable pores extend from the soil surface to deep into the profile. These pores allow water infiltration, root penetration, and air exchange to occur.  The sample on the left was taken from a field no-tilled for more than 10 years.  The one on the right is from a continuously tilled field with the same soil type.

While tillage has been used for crop production, it does destroy soil structure, breaks up the soil pores, and reduces the amount of residue on the soil surface. If the soil structure was bad, e.g., compaction, this may be desirable as tillage can break up the compacted soil and create some new pores. However, if the soil structure was already favorable for crop growth, the tillage operation will break up the existing soil structure and make it more susceptible to compaction by reducing the soil’s strength. Without soil structure, future operations may compact the soil by squeezing out the pore spaces between the soil aggregates.

Soil Biological Life

While tillage has been used to prepare a seedbed, it also destroys the existing root structures in the soil and some of the soil’s biological life. Without this biological life, soil structure suffers and many of the nutrients are not as available for crop uptake.

• The roots themselves are like rebar in concrete, giving the soil structural stability.
• The decaying roots provide channels for water penetration and new roots to grow in.
• The many fungi, bacteria and other microorganisms are the glues that hold individual soil particles together. They also process the roots and residue of the previous crops, cycling nutrients and carbon through the soil system.
• Larger organisms such as larva, bugs and worms feed on the microorganisms further cycling materials in the soil and provide additional channels through the soil profile.

Soil biological life improves under diverse no-till systems, building soil aggregation and stability. Tillage destroys this aggregation and the desirable habitat for soil organisms which break down crop residue and roots, cycling the nutrients and carbon contained in them back into the soil system.

Visible in the photo is a healthy soil showing good aggregation, abundant roots, and even a night crawler in the lower right portion of this soil sample.

Residue Management

The tilled plots in the foreground had considerable soil loss and runoff during intense spring rains. The tilled soil surface was susceptible to raindrop impact, causing erosion and surface crusting. The crop residue on the no-till plots in the background absorbed raindrop impact and allowed more water to infiltrate into the soil. With the improved soil structure, the crop is healthier in the no-till.

Crop residue absorbs raindrop impact and keeps the wind off the soil surface.

• This reduces soil particle detachment, reducing erosion from the forces of water and wind.
• By protecting the soil surface, surface crusting is also reduced, improving infiltration and decreasing runoff.
• This effect conserves soil and water and reduces risks to the environment.
• The residue mulch further conserves water by reducing evaporation from the soil surface.
• The decaying residue feeds soil microbes and earthworms, cycling the nutrients and building soil structure.

Crop residue must be properly managed year-round to provide the benefits without interfering with crop production.

Water Conservation

Improved water infiltration, less runoff and reduced evaporative losses in no-till systems can save from 5 to 12 inches per year, making more water available for crop production. The tilled grain sorghum on the right yielded only 61 bu/A in a dry year while the no-till on the left yielded about 121 bu/A.

• With improved soil structure and residue management, more water is available for crop production.
• Better infiltration and less crusting allows more water to be stored in the soil profile rather than lost to runoff.
• Minimizing exposure of the soil surface to wind and sunlight reduces evaporation and keeps the soil surface cooler, often resulting in better rooting, especially near the soil surface.
• Better rooting makes the plant more efficient in using light rainfall events that don’t soak far into the soil profile.

However, depending on the soil moisture holding capacity of the soil, this improved infiltration may lead to leaching nutrients below the active crop rooting zone. Producers must manage their crop selection to make efficient use of the water when it is available and, in some cases, intensify their cropping system to use the water that may be lost.

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