- Email: [email protected]
Air Seeders for Conservation Tillage Crop Production
C H A P T E R
6 Air Seeders for Conservation Tillage Crop Production John Nowatzki North Dakota State University, Fargo, ND, United States O U T L I N E 6.1 Opener Design Options
133
6.6 Varying Conditions
145
6.2 Managing Crop Residue
136
6.7 Precision Agriculture
146
6.3 Soil Disturbance and Environmental Impacts 139
6.8 Energy Requirements
146
6.9 Commercial Options
147
Reference
148
Further Reading
148
6.4 Seed/Fertilizer Placement, Row Spacing
140
6.5 Depth Control and Packing
142
6.1 OPENER DESIGN OPTIONS The performance of the openers on air seeders determines the effectiveness of the planting operation. The basic type of openers affects seed and fertilizer placement in the soil, seedling development, and crop yields. Various opener designs can impact short-term and long-term soil conditions and the field and surrounding environment. The two basic opener designs used on air seeders are disc and hoe openers. “Hybrids” of these two opener designs incorporate some of the features of both. Disc openers can be single or double disc, with gauge wheels mounted beside and in contact with the disc opener, or with a trailing packer wheel functioning as a gauge wheel. Fig. 6.1 illustrates a typical disc opener mounted on an air seeder. Disc openers cut a narrow channel in the soil and insert seeds and fertilizer.
Handbook of Farm, Dairy and Food Machinery Engineering DOI: https://doi.org/10.1016/B978-0-12-814803-7.00006-3
133
© 2019 Elsevier Inc. All rights reserved.
134
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE 6.1 Disc opener.
FIGURE 6.2 Hoe opener.
Hoe openers are available in various widths from less than 1-in-wide spikes to sweeps several inches wide. Hoe openers can be mounted on flexible, rigid, or jointed shanks. Fig. 6.2 shows an example of an air seeder equipped with narrow hoe openers that cut narrow trenches in the soil. Seeds are dropped into the trenches directly behind the openers before the soil can fall back to cover the trenches. Fig. 6.3 shows an example of a narrow hoe opener mounted behind a fluted coulter that cuts through residue remaining from the previous year’s crop. The discs mounted on each side of the hoe opener push soil to cover the seeds and close the trench made by the opener. Crop producers choose opener types based on specific management goals and local cropping conditions. In choosing an opener, producers need to consider the amount and type of crop residue, the crop being planted, fertilizer placement, and soil type and conditions. Air seeder opener designs also influence the amount of residue maintained on the soil surface and the position of the residue after planting.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
135
6.1 OPENER DESIGN OPTIONS
FIGURE 6.3 Hoe opener with cutting coulter and closing discs.
FIGURE 6.4 Hair pinning.
Disc openers leave most of the existing residue on the soil surface or standing after planting, which impacts soil temperature and moisture. Planting with disc openers in fields with thick residue lying on the soil surface can result in seed placed in residue rather than placed directly in soil. Crop producers refer to this as hair-pinning. Fig. 6.4 illustrates pieces of residue pressed into the seed channel. This is a common problem occurring while using disc openers when the surface reside is wet or damp. Disc openers generally disturb soil less than hoe openers, maintaining moisture in the seed zone. However, this may slow soil warming after planting. Hoe openers cause more
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
136
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
soil disturbance resulting in more of the residue mixed into the soil. Hoe openers push residue aside to place seed into tilled soil, which can promote both soil warming and drying.
6.2 MANAGING CROP RESIDUE Crop residue is a resource to conserve and use. Crop residue is a food source for beneficial fungi, bacteria, and insects; limits evaporation from the soil surface; and maintains water vapor in the soil. Crop producers manage crop residue based on several factors including the crop being planted, soil type, annual precipitation, crop rotations, the amount of residue present in fields, and their overall tillage system. Generally, seedlings of larger seeds can emerge through more residue than smaller seeds. Areas with greater annual precipitation generally produce higher yielding crops resulting in more crop residue. Some crops such as canola, soybeans, and dry beans produce much less crop residue than corn and small grain crops. No-till systems result in more crop residue left standing or on the soil surface compared with more intensive tillage systems. No-till cropping systems also affect annual crop nutrient availability. North Dakota State University extension service wheat nitrogen fertilizer recommendations include a 20lb/acre negative credit for fields that have been no-tilled for less than 5 years, and a 50lb/acre positive credit for fields that have been no tillno-tilled for more than 5 years (Franzen, 2009). Soil scientists suggest that this increase in nitrogen efficiency in long-term no-till may occur because organic compounds are formed by soil organisms shortly after fertilizer application, creating, in effect, a slow release fertilizer. Air seeder openers that preclude a no-till system impact the nitrogen fertilizer recommendations, although single, annual passes with hoe openers that are operated 30 or less in the ground would not negate the no-till nitrogen credit. Fig. 6.5 shows wheat stubble after harvest grown. Corn stalks on the soil surface with the wheat stubble are from the previous year’s corn crop, indicating successful no-till crop production after a high residue crop. Strip till used with no-till in years when row crops are rotated with solid-seeded crops does not negate the increased nitrogen efficiency because areas between the tilled strips continue the organic matter buildup over time. Fig. 6.6 shows 8-in. wide strips tilled in wheat stubble. The soil in the tilled strips warms faster than the untilled stubble between the strips during the spring season. Warmer soil allows crop producers to plant earlier in the season. Managing crop residue at harvest time impacts the planting operation during the next crop season. Crop residue should be spread uniformly during the harvest operation. Uniform distribution of crop straw and chaff facilitates uniform seed placement during seeding. Spreading straw and chaff after harvest is difficult and ineffective. Straw chopper/spreaders and chaff spreaders work best spreading crop residue over the width of the combine header. During harvesting, combines should continue to move until all crop residue is cleared from the machines. Stopping combines before all of the straw and chaff has been cleared results in residue piles in the field that can interfere with seeders. Disc openers function better in standing residue rather than where the residue is cut off and lying on the soil surface; hoe openers generally function better in these conditions.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
137
6.2 MANAGING CROP RESIDUE
FIGURE 6.5 Wheat stubble with corn stalks.
However, hoe openers may cause bunching if the residue is wet or unevenly spread. Wider distances between seed rows and more vertical clearance of the seeder help prevent bunching. Combines can be equipped with stripper headers that remove only the grain heads, leaving all the grain stalk standing. Disc openers function best in this very tall stubble. Fig. 6.7 is an image of wheat stubble following harvesting by a combine equipped with a stripper header. The tall stubble can be advantageous for crop production in drier
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
138
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE 6.6 Strip till.
FIGURE 6.7 Tall stubble, harvested with stripper header.
climates because the tall stubble prevents the wind from blowing snow off fields, increasing soil moisture. The height of standing stubble from the previous crop has little impact on soil temperature but does affect soil moisture the following spring. The NDSU Residue Management Project monitored soil moisture and temperature under various residue management conditions in western, central, and eastern North Dakota. Data from this project show that winter and spring soil temperatures are not influenced by stubble height; however, the shorter stubble does dry faster in the spring of the year prior to planting, and holds less moisture in the fall after harvest.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
6.3 SOIL DISTURBANCE AND ENVIRONMENTAL IMPACTS
139
FIGURE 6.8 Row cleaner.
Row cleaners, usually spoked wheels mounted in front of disc openers, can be used to facilitate planting fields with high residue. Row cleaners push some residue to the side, allowing the opener to penetrate the soil. Spoke-type row cleaners can become plugged in corn or sunflower residue, with the spokes acting like a trash collector. One solution to this problem is to use smooth discs for row cleaners to push residue aside. Another solution is to plant between the previous year’s crop rows without using any row cleaner. One spoked wheel operated at 1520 degrees from the disc opener operating plane, rather than two spoked wheels, may function better on equipment used to plant in narrow rows with higher crop residue. Fig. 6.8 shows spiked disc wheels mounted in front of soil opening coulters. The row cleaners function to move thick residue aside allowing the opener to operate more efficiently. Hitch guidance technology assists operators with planting between the previous year’s crop rows. Fig. 6.9 is an image of two metal discs that operate on either side of the opener furrow. If one disc drops lower than the other, then an electric signal triggers two hydraulic rams to push or pull the air seeder hitch, keeping the disc openers between the stubble rows of the previous crop. Crop rotations can be used to effectively manage crop residue. Low residue-producing crops, such as peas, soybeans, lentils, flax, safflowers, and sunflowers, can be alternated with high residue-producing crops, such as wheat, barley, and corn.
6.3 SOIL DISTURBANCE AND ENVIRONMENTAL IMPACTS The Natural Resource Conservation Service has developed a tillage rating system that can be used for openers called the Soil Tillage Intensity Rating (STIR). This system assigns a numerical value to openers based on operating speed of the seeder, opener type, depth of operation, and the percent of soil surface area disturbed. Lower numbers indicate less overall disturbance to the soil. Values can range from 0 to 200, with lower numbers
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
140
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE 6.9 Row sensor.
indicating a preferable rating. STIR values reflect the type and severity of soil disturbance caused by openers. Reduced tillage over time increases soil organic matter. Soil organic matter impacts the biological, physical, and chemical properties of the soil. The cation exchange capacity of soil increases with increased organic matter, resulting in an increased ability to hold positively charged plant nutrients, and a decreased leaching potential. Soil organic matter affects soil structure, resulting in larger and more stable aggregates and reducing the potential for soil compaction. Higher amounts of soil organic matter increase the pore space in soil, which increases the water infiltration rate and the water holding capacity of soil. Tillage contributes to loss of carbon from the soil. Maintaining carbon in the soil provides a source of microbial nutrients and reduces the amount of carbon dioxide released into the atmosphere. Soil organic matter increases over time in agricultural soils when crop residue is left on the soil surface. Air seeder opener construction affects soil disturbance, which impacts soil properties and the environment. Research conducted in Minnesota showed that intensive tillage reduced soil organic matter significantly more than minimum or no-till. Wide sweep hoe openers cause significant soil tillage resulting in carbon loss from the soil.
6.4 SEED/FERTILIZER PLACEMENT, ROW SPACING Minimum till, one-pass, and no-till seeding with fertilizer application, including injecting anhydrous ammonia at planting time, are common in the northern Great Plains. However, most grain crops require more nitrogen fertilizer than can be placed safely in a narrow seed row.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
6.4 SEED/FERTILIZER PLACEMENT, ROW SPACING
141
There is variation in the primary factors affecting the amount of nitrogen fertilizer that can be applied with the seed, depending on the distance between rows and the distribution of both the seed and fertilizer within the row. More fertilizer can be applied with the seed when the seeds and fertilizer are spread over a wider area. Hoe openers generally have greater seedbed utilization than disc openers. Other factors influencing the amount of nitrogen fertilizer that can be placed close to crop seeds include soil texture, soil pH, soil water, precipitation, fertilizer placement, fertilizer form, fertilizer material, and the type of crop. Fig. 6.10 illustrates an example of an opener that spreads seeds and fertilizer over an 8-in. strip, which allows for high amounts of nitrogen fertilizer to be placed directly with the crop seeds. More nitrogen fertilizer can be applied with the crop seeds when a greater amount of soil is disturbed during the planting operation. This means that, in general, more nitrogen can be applied with the seed when planting with hoe openers than with disc openers unless the disc opener design places the seed and fertilizer in separate rows. The separation of fertilizer from the seeds needs to be greater in some soil conditions, such as in dry, cloddy soils. The risk of stand reduction is greater from nitrogen toxicity in sandier soils than in clayey soils. More than 2030 lb/ac of nitrogen fertilizer placed with seeds can result in reduced germination, low seedling emergence, and poor stands, with subsequent yield loss. Separate fertilizer delivery systems can be used to place fertilizer in a band to the side and below the seed. With disc openers, a separate disc can be mounted between two seed rows to place fertilizer in a band shared by two seed rows. This is called mid-row banding. Mid-row bands deliver nitrogen products safely if there is sufficient space between the seed and fertilizer rows. Fig. 6.11 shows a mid-row bander, which is a separate soil opener used only to inject fertilizer into the soil. Mid-row banders are mounted on air seeders between the seed openers.
FIGURE 6.10 Wide disc opener.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
142
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE
6.11 Mid-row
bander.
However, mid-row banding places phosphorus materials too far away from the plants to deliver a “starter” effect to young plants. A separate system to deliver phosphorus in or near the seed row is required to achieve “starter” phosphorus effects. Some hoe seeders are designed with a fertilizer tube next to the seed tube that places fertilizer below and to the side of the seed row. This is referred to as double-shooting. Low-draft, doubleshooting openers place seeds and fertilizer at the same depth, which is designed to reduce the power required to pull the seeder. Paired-row opener designs on air seeders plant the seeds in two closely placed rows separated by a wider space between the next two paired rows. Separate fertilizer openers place the fertilizer in the wider space between the sets of paired rows. The fertilizer band is placed below seed depth allowing the downward growth angle of the seminal roots on cereal plants to contact the fertilizer. The air seed delivery system must deliver enough air to move the correct amount of seed to the farthest ends of the seeder but not blow seeds out of the seed slot or cause damage to the seeds. This is accomplished by incorporating an air dissipation system into the air delivery system prior to the seed discharge into the opener. Fig. 6.12 shows the pipes and hoses used to move seeds from the air seeder grain tanks to the soil openers. Air seeders are equipped with air blowers to move seeds through the hoses.
6.5 DEPTH CONTROL AND PACKING Uniform depth placement of both seed and fertilizer influences seedling emergence and, ultimately, crop yield. Seedsoil contact may not be as important for transfer of
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
143
6.5 DEPTH CONTROL AND PACKING
FIGURE 6.12 Air delivery system.
water from soil to seed as commonly thought. Recent research demonstrated that seeds are capable of germinating without contact with moist soil, because water absorbed by seeds can be directly attributed to vapor. Placing seed at the desirable depth near moist soil is important, but pressing seed firmly into soil is required only to maintain high relative humidity near the seed. Seed germinates just as quickly in loose moist soil as in firm moist soil if it is covered to protect it from the drying effects of wind and sun. Factors influencing uniformity of seeding depth include independent pressure on each opener assembly, gauge wheels, shank linkage, and caster wheels. Depth control wheels and packer wheels on seeders improve uniform seed depth placement. Packer/gauge wheels mounted close to the point of seed release will place seed more consistently at the proper depth, compared with wheels mounted farther behind or in front of the release point. Fig. 6.13 shows air seeder packer wheels mounted behind each soil opener. Gauge wheels either behind or beside the disc opener allow significant down pressure on the opener to penetrate firm soil and cut residue while maintaining the proper uniform seeding depth. Fig. 6.14 shows a wheel mounted adjacent to an opener disc that can be adjusted to regulate the depth at which seeds are placed in the soil. Some degree of packing almost always results in better crop emergence. Trailing press wheels are available in various widths. Narrow press wheels (1.52 in. wide) may produce a narrow furrow in loose soil conditions. This can create a problem if rainfall occurs before the seedling emerges because rain can wash the soil between the furrows into the seed row, causing the plant to be covered too deeply. Wider press wheels reduce this problem. An advantage to the use of narrow press wheels is that the furrow offers protection to the emerging seedling from strong winds. Seeding into a previous crop residue and maintaining residue on the soil surface also provides protection for the emerging seedling.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
144
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE
6.13 Packer
wheels.
FIGURE
6.14 Gauge
wheel.
Usually, the press wheel should be about as wide as the seed strip. Wide press wheels can flatten the crop residue, exposing emerging seedlings to wind damage. Seeders with the ability to monitor and alter pressure independently on openers and packer wheels function better to both place seed at uniform depth and accomplish even
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
6.6 VARYING CONDITIONS
145
packing on seed rows. These systems detect contact of the opener assembly with the soil surface and automatically adjust hydraulic pressure applied to the openers to maintain the desired constant degree of contact with the soil, as soil conditions vary throughout the field.
6.6 VARYING CONDITIONS Soil type and soil conditions influence how well openers operate. Neither hoe nor disc openers work as well in wet soils as in drier soils. Seeding or tilling wet soils packs the soil, damaging the rooting environment, which results in reduced crop growth and yield. Clay soils pack well but can become hard when they dry. Clay can build up on packer wheels, changing the seeding depth. Openers can create a “glazed” furrow sidewall in wet conditions, which slows germination. Seeders need to be flexible to function properly on irregular soil surfaces and sloping fields. Seeders with rigid frame sections larger than 1214 ft. generally do not follow the soil contour on sloping fields and when crossing drainage ditches, resulting in seed being placed too shallowly or unevenly on the soil surface. Parallel linkage has been used on row-crop planters for a number of years, and only recently has this innovation been applied to drills. Parallel linkage on individual openers operating independently of each other allows the opener to track soil surface more accurately, giving a more uniform placement of seed at the desired depth. Fig. 6.15 is an example of an opener assembly that ensures both the seed and fertilizer are placed at the same depth in the soil. The linkage functions to raise and lower the seed and fertilizer openers simultaneously and by the same amount.
FIGURE 6.15 Parallel linkage.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
146
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
6.7 PRECISION AGRICULTURE Air seeders can be used to implement various precision agriculture management practices. Air seeder carts can be constructed with more than one compartment. These compartments can be used for both seed and fertilizers. Clutches automatically vary the seed and fertilizer output regulated by GPS-equipped controllers in the tractor. Variable rate technology allows crop producers to manage fields by productivity zones, applying specific rates of both fertilizer and seed in each zone. Fig. 6.16 shows an air cart that includes grain and fertilizer storage tanks, regulators, rate adjustment technology, and the seed air delivery system equipment. Section control technology can provide significant seed savings on wide air seeders, particularly on irregularly shaped fields. This technology uses GPS-equipped controllers to stop seed and fertilizer application when the equipment travels over areas that have already been planted. Air seeders can be manufactured to control various widths of sections. Fig. 6.17 shows a computer controller display used in tractors to interact with the air seeder control technology. The computer controller can also be used to record a planting map.
6.8 ENERGY REQUIREMENTS Fuel consumption is an operation expense that also should be considered in opener selection. Various research studies indicate that the energy requirements to operate air
FIGURE 6.16
Air cart.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
147
6.9 COMMERCIAL OPTIONS
FIGURE
6.17 Computer
controller.
seeders with disc openers are nearly half the energy requirements of similar seeders with hoe openers. The width of the hoe opener, depth of operation, and the unique soil and field conditions affect the energy requirements of each planting operation.
6.9 COMMERCIAL OPTIONS The main categories of seed openers include single-disc, double-disc, offset double-disc, disc-shoe, hoe and sweep, and wide shovel, which progressively disturb more soil at the time of seeding. Several air seeder manufacturers provide seeders with various opener options. The list of manufacturers included here is not complete, but includes many of the companies that market air seeders in the Great Plains region of the United States. Amity Technology (http://www.amitytech.com) Bourgault Industries (http://www.bourgault.com) Case IH (http://www.caseih.com) Cross Slot (http://www.crossslot.com) Great Plains (http://www.greatplainsmfg.com) Horsch (http://www.horschanderson.com) John Deere (http://www.deere.com) K-Hart Industries (http://www.khartindustries.com) Morris Industries (http://www.morris-industries.com) Salford Machinery (https://salfordgroup.com/) Seed Hawk (http://www.seedhawk.com) SeedMaster (http://www.seedmaster.ca) Sunflower (http://www.sunflowermfg.com)
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
148
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
Reference Franzen, D.W., 2009. Fertilizing Hard Red Spring Wheat and Durum. NDSU Ext. Pub. SF-712 (Revised), Fargo, N.D.
Further Reading ASABE D497. 7, 2011. Agricultural Machinery Management Data. ASABE Standards. ASABE, 2950 Niles Road, St. Joseph, MI. Awale, R., Chatterjee, A., Franzen, D., 2013. Tillage and N-fertilizer influences on selected organic carbon fractions in a North Dakota silty clay soil. Soil Tillage Res. 134, 213222. Deibert, E.J., 1994. Fertilizer Application with Small Grain Seed at Planting. NDSU Ext. Pub. EB-62. NDSU Extension Serv, Fargo, N.D. Franzen, D.W., Endres, G., Ashley, R., Staricka, J., Lukach, J., McKay, K., 2011. Revising nitrogen recommendations for wheat in response to the need for support of variable-rate nitrogen application. J. Agric. Sci. Technol. A1, 8995. Lazarus, W.L., 2009. Machinery Cost Estimates. University of Minnesota Extension, St. Paul, MN. Overstreet, L.F., DeJong-Huges, J., 2009. The Importance of Soil Organic Matter in Cropping Systems of the Northern Great Plains. University of Minnesota Extension, St. Paul, MN.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
6 Air Seeders for Conservation Tillage Crop Production John Nowatzki North Dakota State University, Fargo, ND, United States O U T L I N E 6.1 Opener Design Options
133
6.6 Varying Conditions
145
6.2 Managing Crop Residue
136
6.7 Precision Agriculture
146
6.3 Soil Disturbance and Environmental Impacts 139
6.8 Energy Requirements
146
6.9 Commercial Options
147
Reference
148
Further Reading
148
6.4 Seed/Fertilizer Placement, Row Spacing
140
6.5 Depth Control and Packing
142
6.1 OPENER DESIGN OPTIONS The performance of the openers on air seeders determines the effectiveness of the planting operation. The basic type of openers affects seed and fertilizer placement in the soil, seedling development, and crop yields. Various opener designs can impact short-term and long-term soil conditions and the field and surrounding environment. The two basic opener designs used on air seeders are disc and hoe openers. “Hybrids” of these two opener designs incorporate some of the features of both. Disc openers can be single or double disc, with gauge wheels mounted beside and in contact with the disc opener, or with a trailing packer wheel functioning as a gauge wheel. Fig. 6.1 illustrates a typical disc opener mounted on an air seeder. Disc openers cut a narrow channel in the soil and insert seeds and fertilizer.
Handbook of Farm, Dairy and Food Machinery Engineering DOI: https://doi.org/10.1016/B978-0-12-814803-7.00006-3
133
© 2019 Elsevier Inc. All rights reserved.
134
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE 6.1 Disc opener.
FIGURE 6.2 Hoe opener.
Hoe openers are available in various widths from less than 1-in-wide spikes to sweeps several inches wide. Hoe openers can be mounted on flexible, rigid, or jointed shanks. Fig. 6.2 shows an example of an air seeder equipped with narrow hoe openers that cut narrow trenches in the soil. Seeds are dropped into the trenches directly behind the openers before the soil can fall back to cover the trenches. Fig. 6.3 shows an example of a narrow hoe opener mounted behind a fluted coulter that cuts through residue remaining from the previous year’s crop. The discs mounted on each side of the hoe opener push soil to cover the seeds and close the trench made by the opener. Crop producers choose opener types based on specific management goals and local cropping conditions. In choosing an opener, producers need to consider the amount and type of crop residue, the crop being planted, fertilizer placement, and soil type and conditions. Air seeder opener designs also influence the amount of residue maintained on the soil surface and the position of the residue after planting.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
135
6.1 OPENER DESIGN OPTIONS
FIGURE 6.3 Hoe opener with cutting coulter and closing discs.
FIGURE 6.4 Hair pinning.
Disc openers leave most of the existing residue on the soil surface or standing after planting, which impacts soil temperature and moisture. Planting with disc openers in fields with thick residue lying on the soil surface can result in seed placed in residue rather than placed directly in soil. Crop producers refer to this as hair-pinning. Fig. 6.4 illustrates pieces of residue pressed into the seed channel. This is a common problem occurring while using disc openers when the surface reside is wet or damp. Disc openers generally disturb soil less than hoe openers, maintaining moisture in the seed zone. However, this may slow soil warming after planting. Hoe openers cause more
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
136
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
soil disturbance resulting in more of the residue mixed into the soil. Hoe openers push residue aside to place seed into tilled soil, which can promote both soil warming and drying.
6.2 MANAGING CROP RESIDUE Crop residue is a resource to conserve and use. Crop residue is a food source for beneficial fungi, bacteria, and insects; limits evaporation from the soil surface; and maintains water vapor in the soil. Crop producers manage crop residue based on several factors including the crop being planted, soil type, annual precipitation, crop rotations, the amount of residue present in fields, and their overall tillage system. Generally, seedlings of larger seeds can emerge through more residue than smaller seeds. Areas with greater annual precipitation generally produce higher yielding crops resulting in more crop residue. Some crops such as canola, soybeans, and dry beans produce much less crop residue than corn and small grain crops. No-till systems result in more crop residue left standing or on the soil surface compared with more intensive tillage systems. No-till cropping systems also affect annual crop nutrient availability. North Dakota State University extension service wheat nitrogen fertilizer recommendations include a 20lb/acre negative credit for fields that have been no-tilled for less than 5 years, and a 50lb/acre positive credit for fields that have been no tillno-tilled for more than 5 years (Franzen, 2009). Soil scientists suggest that this increase in nitrogen efficiency in long-term no-till may occur because organic compounds are formed by soil organisms shortly after fertilizer application, creating, in effect, a slow release fertilizer. Air seeder openers that preclude a no-till system impact the nitrogen fertilizer recommendations, although single, annual passes with hoe openers that are operated 30 or less in the ground would not negate the no-till nitrogen credit. Fig. 6.5 shows wheat stubble after harvest grown. Corn stalks on the soil surface with the wheat stubble are from the previous year’s corn crop, indicating successful no-till crop production after a high residue crop. Strip till used with no-till in years when row crops are rotated with solid-seeded crops does not negate the increased nitrogen efficiency because areas between the tilled strips continue the organic matter buildup over time. Fig. 6.6 shows 8-in. wide strips tilled in wheat stubble. The soil in the tilled strips warms faster than the untilled stubble between the strips during the spring season. Warmer soil allows crop producers to plant earlier in the season. Managing crop residue at harvest time impacts the planting operation during the next crop season. Crop residue should be spread uniformly during the harvest operation. Uniform distribution of crop straw and chaff facilitates uniform seed placement during seeding. Spreading straw and chaff after harvest is difficult and ineffective. Straw chopper/spreaders and chaff spreaders work best spreading crop residue over the width of the combine header. During harvesting, combines should continue to move until all crop residue is cleared from the machines. Stopping combines before all of the straw and chaff has been cleared results in residue piles in the field that can interfere with seeders. Disc openers function better in standing residue rather than where the residue is cut off and lying on the soil surface; hoe openers generally function better in these conditions.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
137
6.2 MANAGING CROP RESIDUE
FIGURE 6.5 Wheat stubble with corn stalks.
However, hoe openers may cause bunching if the residue is wet or unevenly spread. Wider distances between seed rows and more vertical clearance of the seeder help prevent bunching. Combines can be equipped with stripper headers that remove only the grain heads, leaving all the grain stalk standing. Disc openers function best in this very tall stubble. Fig. 6.7 is an image of wheat stubble following harvesting by a combine equipped with a stripper header. The tall stubble can be advantageous for crop production in drier
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
138
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE 6.6 Strip till.
FIGURE 6.7 Tall stubble, harvested with stripper header.
climates because the tall stubble prevents the wind from blowing snow off fields, increasing soil moisture. The height of standing stubble from the previous crop has little impact on soil temperature but does affect soil moisture the following spring. The NDSU Residue Management Project monitored soil moisture and temperature under various residue management conditions in western, central, and eastern North Dakota. Data from this project show that winter and spring soil temperatures are not influenced by stubble height; however, the shorter stubble does dry faster in the spring of the year prior to planting, and holds less moisture in the fall after harvest.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
6.3 SOIL DISTURBANCE AND ENVIRONMENTAL IMPACTS
139
FIGURE 6.8 Row cleaner.
Row cleaners, usually spoked wheels mounted in front of disc openers, can be used to facilitate planting fields with high residue. Row cleaners push some residue to the side, allowing the opener to penetrate the soil. Spoke-type row cleaners can become plugged in corn or sunflower residue, with the spokes acting like a trash collector. One solution to this problem is to use smooth discs for row cleaners to push residue aside. Another solution is to plant between the previous year’s crop rows without using any row cleaner. One spoked wheel operated at 1520 degrees from the disc opener operating plane, rather than two spoked wheels, may function better on equipment used to plant in narrow rows with higher crop residue. Fig. 6.8 shows spiked disc wheels mounted in front of soil opening coulters. The row cleaners function to move thick residue aside allowing the opener to operate more efficiently. Hitch guidance technology assists operators with planting between the previous year’s crop rows. Fig. 6.9 is an image of two metal discs that operate on either side of the opener furrow. If one disc drops lower than the other, then an electric signal triggers two hydraulic rams to push or pull the air seeder hitch, keeping the disc openers between the stubble rows of the previous crop. Crop rotations can be used to effectively manage crop residue. Low residue-producing crops, such as peas, soybeans, lentils, flax, safflowers, and sunflowers, can be alternated with high residue-producing crops, such as wheat, barley, and corn.
6.3 SOIL DISTURBANCE AND ENVIRONMENTAL IMPACTS The Natural Resource Conservation Service has developed a tillage rating system that can be used for openers called the Soil Tillage Intensity Rating (STIR). This system assigns a numerical value to openers based on operating speed of the seeder, opener type, depth of operation, and the percent of soil surface area disturbed. Lower numbers indicate less overall disturbance to the soil. Values can range from 0 to 200, with lower numbers
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
140
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE 6.9 Row sensor.
indicating a preferable rating. STIR values reflect the type and severity of soil disturbance caused by openers. Reduced tillage over time increases soil organic matter. Soil organic matter impacts the biological, physical, and chemical properties of the soil. The cation exchange capacity of soil increases with increased organic matter, resulting in an increased ability to hold positively charged plant nutrients, and a decreased leaching potential. Soil organic matter affects soil structure, resulting in larger and more stable aggregates and reducing the potential for soil compaction. Higher amounts of soil organic matter increase the pore space in soil, which increases the water infiltration rate and the water holding capacity of soil. Tillage contributes to loss of carbon from the soil. Maintaining carbon in the soil provides a source of microbial nutrients and reduces the amount of carbon dioxide released into the atmosphere. Soil organic matter increases over time in agricultural soils when crop residue is left on the soil surface. Air seeder opener construction affects soil disturbance, which impacts soil properties and the environment. Research conducted in Minnesota showed that intensive tillage reduced soil organic matter significantly more than minimum or no-till. Wide sweep hoe openers cause significant soil tillage resulting in carbon loss from the soil.
6.4 SEED/FERTILIZER PLACEMENT, ROW SPACING Minimum till, one-pass, and no-till seeding with fertilizer application, including injecting anhydrous ammonia at planting time, are common in the northern Great Plains. However, most grain crops require more nitrogen fertilizer than can be placed safely in a narrow seed row.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
6.4 SEED/FERTILIZER PLACEMENT, ROW SPACING
141
There is variation in the primary factors affecting the amount of nitrogen fertilizer that can be applied with the seed, depending on the distance between rows and the distribution of both the seed and fertilizer within the row. More fertilizer can be applied with the seed when the seeds and fertilizer are spread over a wider area. Hoe openers generally have greater seedbed utilization than disc openers. Other factors influencing the amount of nitrogen fertilizer that can be placed close to crop seeds include soil texture, soil pH, soil water, precipitation, fertilizer placement, fertilizer form, fertilizer material, and the type of crop. Fig. 6.10 illustrates an example of an opener that spreads seeds and fertilizer over an 8-in. strip, which allows for high amounts of nitrogen fertilizer to be placed directly with the crop seeds. More nitrogen fertilizer can be applied with the crop seeds when a greater amount of soil is disturbed during the planting operation. This means that, in general, more nitrogen can be applied with the seed when planting with hoe openers than with disc openers unless the disc opener design places the seed and fertilizer in separate rows. The separation of fertilizer from the seeds needs to be greater in some soil conditions, such as in dry, cloddy soils. The risk of stand reduction is greater from nitrogen toxicity in sandier soils than in clayey soils. More than 2030 lb/ac of nitrogen fertilizer placed with seeds can result in reduced germination, low seedling emergence, and poor stands, with subsequent yield loss. Separate fertilizer delivery systems can be used to place fertilizer in a band to the side and below the seed. With disc openers, a separate disc can be mounted between two seed rows to place fertilizer in a band shared by two seed rows. This is called mid-row banding. Mid-row bands deliver nitrogen products safely if there is sufficient space between the seed and fertilizer rows. Fig. 6.11 shows a mid-row bander, which is a separate soil opener used only to inject fertilizer into the soil. Mid-row banders are mounted on air seeders between the seed openers.
FIGURE 6.10 Wide disc opener.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
142
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE
6.11 Mid-row
bander.
However, mid-row banding places phosphorus materials too far away from the plants to deliver a “starter” effect to young plants. A separate system to deliver phosphorus in or near the seed row is required to achieve “starter” phosphorus effects. Some hoe seeders are designed with a fertilizer tube next to the seed tube that places fertilizer below and to the side of the seed row. This is referred to as double-shooting. Low-draft, doubleshooting openers place seeds and fertilizer at the same depth, which is designed to reduce the power required to pull the seeder. Paired-row opener designs on air seeders plant the seeds in two closely placed rows separated by a wider space between the next two paired rows. Separate fertilizer openers place the fertilizer in the wider space between the sets of paired rows. The fertilizer band is placed below seed depth allowing the downward growth angle of the seminal roots on cereal plants to contact the fertilizer. The air seed delivery system must deliver enough air to move the correct amount of seed to the farthest ends of the seeder but not blow seeds out of the seed slot or cause damage to the seeds. This is accomplished by incorporating an air dissipation system into the air delivery system prior to the seed discharge into the opener. Fig. 6.12 shows the pipes and hoses used to move seeds from the air seeder grain tanks to the soil openers. Air seeders are equipped with air blowers to move seeds through the hoses.
6.5 DEPTH CONTROL AND PACKING Uniform depth placement of both seed and fertilizer influences seedling emergence and, ultimately, crop yield. Seedsoil contact may not be as important for transfer of
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
143
6.5 DEPTH CONTROL AND PACKING
FIGURE 6.12 Air delivery system.
water from soil to seed as commonly thought. Recent research demonstrated that seeds are capable of germinating without contact with moist soil, because water absorbed by seeds can be directly attributed to vapor. Placing seed at the desirable depth near moist soil is important, but pressing seed firmly into soil is required only to maintain high relative humidity near the seed. Seed germinates just as quickly in loose moist soil as in firm moist soil if it is covered to protect it from the drying effects of wind and sun. Factors influencing uniformity of seeding depth include independent pressure on each opener assembly, gauge wheels, shank linkage, and caster wheels. Depth control wheels and packer wheels on seeders improve uniform seed depth placement. Packer/gauge wheels mounted close to the point of seed release will place seed more consistently at the proper depth, compared with wheels mounted farther behind or in front of the release point. Fig. 6.13 shows air seeder packer wheels mounted behind each soil opener. Gauge wheels either behind or beside the disc opener allow significant down pressure on the opener to penetrate firm soil and cut residue while maintaining the proper uniform seeding depth. Fig. 6.14 shows a wheel mounted adjacent to an opener disc that can be adjusted to regulate the depth at which seeds are placed in the soil. Some degree of packing almost always results in better crop emergence. Trailing press wheels are available in various widths. Narrow press wheels (1.52 in. wide) may produce a narrow furrow in loose soil conditions. This can create a problem if rainfall occurs before the seedling emerges because rain can wash the soil between the furrows into the seed row, causing the plant to be covered too deeply. Wider press wheels reduce this problem. An advantage to the use of narrow press wheels is that the furrow offers protection to the emerging seedling from strong winds. Seeding into a previous crop residue and maintaining residue on the soil surface also provides protection for the emerging seedling.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
144
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
FIGURE
6.13 Packer
wheels.
FIGURE
6.14 Gauge
wheel.
Usually, the press wheel should be about as wide as the seed strip. Wide press wheels can flatten the crop residue, exposing emerging seedlings to wind damage. Seeders with the ability to monitor and alter pressure independently on openers and packer wheels function better to both place seed at uniform depth and accomplish even
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
6.6 VARYING CONDITIONS
145
packing on seed rows. These systems detect contact of the opener assembly with the soil surface and automatically adjust hydraulic pressure applied to the openers to maintain the desired constant degree of contact with the soil, as soil conditions vary throughout the field.
6.6 VARYING CONDITIONS Soil type and soil conditions influence how well openers operate. Neither hoe nor disc openers work as well in wet soils as in drier soils. Seeding or tilling wet soils packs the soil, damaging the rooting environment, which results in reduced crop growth and yield. Clay soils pack well but can become hard when they dry. Clay can build up on packer wheels, changing the seeding depth. Openers can create a “glazed” furrow sidewall in wet conditions, which slows germination. Seeders need to be flexible to function properly on irregular soil surfaces and sloping fields. Seeders with rigid frame sections larger than 1214 ft. generally do not follow the soil contour on sloping fields and when crossing drainage ditches, resulting in seed being placed too shallowly or unevenly on the soil surface. Parallel linkage has been used on row-crop planters for a number of years, and only recently has this innovation been applied to drills. Parallel linkage on individual openers operating independently of each other allows the opener to track soil surface more accurately, giving a more uniform placement of seed at the desired depth. Fig. 6.15 is an example of an opener assembly that ensures both the seed and fertilizer are placed at the same depth in the soil. The linkage functions to raise and lower the seed and fertilizer openers simultaneously and by the same amount.
FIGURE 6.15 Parallel linkage.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
146
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
6.7 PRECISION AGRICULTURE Air seeders can be used to implement various precision agriculture management practices. Air seeder carts can be constructed with more than one compartment. These compartments can be used for both seed and fertilizers. Clutches automatically vary the seed and fertilizer output regulated by GPS-equipped controllers in the tractor. Variable rate technology allows crop producers to manage fields by productivity zones, applying specific rates of both fertilizer and seed in each zone. Fig. 6.16 shows an air cart that includes grain and fertilizer storage tanks, regulators, rate adjustment technology, and the seed air delivery system equipment. Section control technology can provide significant seed savings on wide air seeders, particularly on irregularly shaped fields. This technology uses GPS-equipped controllers to stop seed and fertilizer application when the equipment travels over areas that have already been planted. Air seeders can be manufactured to control various widths of sections. Fig. 6.17 shows a computer controller display used in tractors to interact with the air seeder control technology. The computer controller can also be used to record a planting map.
6.8 ENERGY REQUIREMENTS Fuel consumption is an operation expense that also should be considered in opener selection. Various research studies indicate that the energy requirements to operate air
FIGURE 6.16
Air cart.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
147
6.9 COMMERCIAL OPTIONS
FIGURE
6.17 Computer
controller.
seeders with disc openers are nearly half the energy requirements of similar seeders with hoe openers. The width of the hoe opener, depth of operation, and the unique soil and field conditions affect the energy requirements of each planting operation.
6.9 COMMERCIAL OPTIONS The main categories of seed openers include single-disc, double-disc, offset double-disc, disc-shoe, hoe and sweep, and wide shovel, which progressively disturb more soil at the time of seeding. Several air seeder manufacturers provide seeders with various opener options. The list of manufacturers included here is not complete, but includes many of the companies that market air seeders in the Great Plains region of the United States. Amity Technology (http://www.amitytech.com) Bourgault Industries (http://www.bourgault.com) Case IH (http://www.caseih.com) Cross Slot (http://www.crossslot.com) Great Plains (http://www.greatplainsmfg.com) Horsch (http://www.horschanderson.com) John Deere (http://www.deere.com) K-Hart Industries (http://www.khartindustries.com) Morris Industries (http://www.morris-industries.com) Salford Machinery (https://salfordgroup.com/) Seed Hawk (http://www.seedhawk.com) SeedMaster (http://www.seedmaster.ca) Sunflower (http://www.sunflowermfg.com)
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING
148
6. AIR SEEDERS FOR CONSERVATION TILLAGE CROP PRODUCTION
Reference Franzen, D.W., 2009. Fertilizing Hard Red Spring Wheat and Durum. NDSU Ext. Pub. SF-712 (Revised), Fargo, N.D.
Further Reading ASABE D497. 7, 2011. Agricultural Machinery Management Data. ASABE Standards. ASABE, 2950 Niles Road, St. Joseph, MI. Awale, R., Chatterjee, A., Franzen, D., 2013. Tillage and N-fertilizer influences on selected organic carbon fractions in a North Dakota silty clay soil. Soil Tillage Res. 134, 213222. Deibert, E.J., 1994. Fertilizer Application with Small Grain Seed at Planting. NDSU Ext. Pub. EB-62. NDSU Extension Serv, Fargo, N.D. Franzen, D.W., Endres, G., Ashley, R., Staricka, J., Lukach, J., McKay, K., 2011. Revising nitrogen recommendations for wheat in response to the need for support of variable-rate nitrogen application. J. Agric. Sci. Technol. A1, 8995. Lazarus, W.L., 2009. Machinery Cost Estimates. University of Minnesota Extension, St. Paul, MN. Overstreet, L.F., DeJong-Huges, J., 2009. The Importance of Soil Organic Matter in Cropping Systems of the Northern Great Plains. University of Minnesota Extension, St. Paul, MN.
HANDBOOK OF FARM, DAIRY AND FOOD MACHINERY ENGINEERING