Chapter 13: Tillage and crop establishment.
* Establishing crops is a multi-step process that begins with preparing the land for planting through tillage.
* Conventional and conservation tillage are the two main tillage approaches. Conventional tillage usually leaves less than 15% residue on the soil surface, whereas conservation tillage leaves 30% or more residue on the soil surface.
* Tillage can incorporate residues as well as fertilizers, manures, and lime. Tilling can control crop pests and provide a seedbed to accommodate seeding equipment.
* Most crops are grown from seed bought from private, commercial companies that own the genetic traits of the seed.
* Federal seed laws require commercial seed labels to inform the farmer and consumer about the seed's characteristics.
* The seed certification process insures the genetic uniqueness and quality of a seed and allows for orderly production of high quality seed for consumers.
* For successful crop establishment, planting depth, seeding rates, and seeding dates need to be optimized.
* Crops are established by either broadcasting or drilling the seed.
federal seed laws
no-till grassland drill
pure live seed (PLS)
row crop planter
Crop production is a multi-step process that begins with crop establishment. Before planting, the land must be prepared with tillage. The earliest farmers often had to drastically alter the vegetation on the land to plant a crop. Today farmers usually contend only with residue from the previous crop. Successful establishment depends on use of viable seed as well as equipment that incorporates the seed to the proper depth.
Tillage has historically been a critical step in land preparation before planting of crops. However, tillage approaches have changed over time, especially with the greater emphasis today on soil conservation and the development of improved planting equipment and chemicals for pest control. The range of tillage approaches varies from moldboard plowing to no-till. Producers' goals influence their choice of tillage methods, and these goals may include the following:
1. Incorporation of residues. Herbage and roots from native vegetation and previous crops are incorporated into the soil to increase their rate of decay. When perennial crop fields are converted to annual crops, tillage buries the plant residue.
2. Control of crop pests such as diseases, insects, and weeds. Diseases and insects that live or survive in crop residues can often be destroyed when the residue is incorporated. Tillage can also be used to control annual and perennial weeds prior to planting.
3. Incorporation of manures, fertilizers, and lime into the root zone of the plant.
4. Preparation of a seedbed to accommodate seeding equipment.
5. Alteration of physical conditions and temperature of the soil. Tillage can reduce soil compaction and mix soils.
Conventional tillage, also called traditional tillage, is at least a two-step process that involves a primary tillage that uses plows to disrupt and turn the soil, followed by secondary tillage that smoothes the soil surface. Conventional tillage is used on about 100 million acres (40.5 million hectares) across all crops in the United States (Table 13-1).
The moldboard plow is an important primary tillage tool used by farmers (Figure 13-1). Some primitive versions of the moldboard plow date back to Roman times. Moldboard plows with iron and steel plowshares were responsible for the westward expansion of agriculture in the United States. Moldboard plowing was essential for breaking the soils of the grass prairies on the Great Plains. It creates significant soil disturbance by shearing off a section of the grass sod and flipping it over (Figure 13-2). Usually, moldboard plowing cultivates the soil to a 6-inch (15.2-centimeter) depth, but on some soils, larger plows can be used to mix soils to greater depths. Moldboard plowing incorporates most of the crop residue that was left on the soil surface, but it also leaves the soil surface vulnerable to erosion. Residue is measured as the percentage of the actual soil surface that is covered with remains of the previous crop (Figure 13-3). Typically in moldboard plowing, less than 15% of the previous crop residue remains. Excessive plowing can lead to the loss of soil organic matter. Modern moldboard plows are typically pulled in gangs of three or more (Figure 13-2).
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Secondary tillage is usually done by harrows. Harrowing smoothes and levels the field and reduces soil particle size. Several types of equipment including field cultivators, spring tooth harrows and disks can be used for harrowing (Figures 13-4 and 13-5). Disks are common secondary tillage equipment and, if large enough, can also be used for primary tillage. A disk is a large concave plate with a sharp edge for slicing and mixing the soil. Most disks incorporate materials from 3 to 6 inches (8 to 15 centimeters) into the soil.
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Conservation tillage is an approach that disturbs the soil but leaves 30% or more of the crop residue on the soil surface. Conservation tillage is used on about 40% of the crop acres in the United States. Mulch tillage, ridge-till, and no-till are three conservation tillage approaches. The conservation tillage approach is possible because of developments in equipment that can plant seed directly into residues and the development of herbicides for post-emergence control of weeds (see Chapter 14). Conservation tillage is an important practice for reducing soil and water erosion. Crop residues protect the soil from the impact of rainfall. They enhance soil organic matter levels and water infiltration, and they decrease soil and nutrient movement. Crop residues decrease moisture loss from the soil surface. Conservation tillage also requires less time and energy than conventional tillage.
Crops vary greatly in residue contribution. When harvested for grain, there are from 3-5 tons/acre (7-11 tonnes/hectare) of corn stover (stalk, leaves, cobs, and husks) remaining. Soybean stems (1 ton/acre; 2.2 tonnes/hectare) and small grains (2 tons straw/acre; 2.5 tonnes/hectare) contribute fewer residues.
Mulch tillage is a tillage system that involves one to three tillage operations. The chisel plow is a primary conservation tillage implement used in mulch tillage. It consists of a small blade or tool attached to a shank (Figure 13-6). The blades attached to the shanks can vary depending on the soil type and goal of the producer. In contrast to the moldboard plow, the chisel plow does not turn the soil over, and it provides minimal incorporation of residues (Figures 13-7 and 13-8). Typically, chisel plows penetrate to a 10-inch (25-centimeter) soil depth. Following chisel plowing, secondary tillage with a disk is often used.
No-till is an approach in which specialized planters with disk openers slice through crop residues and precisely deposit the seed at a desired depth (Figure 13-9.) The seed is covered, and the soil is firmed around the seed. No-till, which involves minimal crop residue disturbance, also minimizes soil erosion and maximizes soil organic matter and soil water conservation. No-till approaches are used less in wet soils in northern latitudes because surface residues insulate the soil, causing it to warm up too slowly in the spring and thus delaying planting.
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Ridge tillage of row crops, such as corn and soybeans, involves specialized tillage and planting equipment. In ridge tillage, ridges of soil about 6 inches (15 centimeters) high are created during the final cultivation of a row crop and, in the subsequent year, the following crop is planted directly into the ridge (Figure 13-10). The ridges are maintained in succeeding years through cultivation. In the spring, the ridges become warmer and dry faster than the surrounding soils. Ridge tillage is very effective in reducing water movement and soil loss.
Timing of Plowing
Farmers plow their soil in the fall following crop removal or in the spring before planting. Fall plowing is advantageous because it allows for breakdown of crop residues during the winter and faster warm-up of the soil in the spring. Fall plowing also facilitates earlier spring planting because in the following spring, only secondary surface tillage is required prior to planting. Spring plowing leaves more crop stubble on the soil surface in the field during the winter, which will reduce wind and water erosion. On some wetter soils, timely spring plowing is not possible without delaying crop planting.
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Establishing the Crop
Most crops are established from seed. In the early days of agriculture, harvested seed was saved and replanted the following year. During this process, crop improvement occurred because agriculturalists selected for specific crop traits such as seed size, color, and time of maturity. Today, some farmers still save their own seed and replant it, but for most of the important crops grown on large acreage, farmers annually purchase seed from private, commercial companies. These companies employ plant breeders and seed production specialists to develop and provide high quality seed of varieties adapted to specific environments. Most private companies and plant breeders legally protect the genetic traits of their modern varieties and, in these situations, it is illegal for growers to save and plant or market the seed they grow.
Federal Seed Laws
Federal seed laws have established that farmers and consumers have a right to know essential information about the seed they purchase. Marketed seed must be labeled and contain specific information (Table 13-2).
During development of modern plant breeding and the commercial seed industry, a seed certification process was established. This process insures the genetic uniqueness and quality of a seed and allows for the orderly production of seed for consumers. The certification process is regulated by State Crop Improvement Associations. Growers who buy "certified seed" are assured that they are purchasing a high quality seed.
Calculation of Pure Live Seeding Rate
To precisely define the quantity of seed needed to establish a crop, the percentage of pure live seed (PLS) in a container of seed must be determined. PLS refers to the viability of the seed and its lack of weed seeds and inert matter. The percentage of pure live seed can be determined from information provided on the seed tag. See Table 13-3 for how to calculate this.
In natural systems, plant seeds are deposited on the soil surface and penetrate the soil by the action of precipitation, freezing and thawing, or rodents. This is an effective reproductive strategy for plants that produce a large number of small seeds, but often will not be profitable in modern crop production systems. In modern systems, seed is expensive, and specific planting strategies are required for profitable crop production.
Depth of Planting
Planting depth in the soil is a critical factor in successful crop establishment. Seed that is planted too deep will exhaust its energy reserves before it reaches the soil surface and will be unable to make new energy through photosynthesis. In contrast, seed planted on the soil surface or very shallowly may initially absorb water but then dry out and die because the roots are not able to reach soil moisture. Crop seed is planted at a prescribed depth to insure stand establishment and uniform plant emergence (Tables 13-4 and 13-5). Determining the correct seeding depth depends on the following factors:
* Seed size. A general rule of thumb for the depth is no deeper than 10 times the diameter of the seed. Larger seeds generally have more vigor than small seeds because of their greater energy reserves. Small-seeded crops such as alfalfa and orchardgrass are especially vulnerable to seedling mortality if planted too deep (Figure 13-11).
* Seedling morphology. A seed's morphological characteristics and type of emergence affect planting depth. Seeds with epigeal emergence, such as soybeans, where the cotyledons emerge aboveground, are more subject to crusting of the soil surface than seeds of plants such as grasses that have hypogeal emergence. Also, corn has a unique ability to emerge from deeper soil depths than other crops because it has a specialized stem structure (the mesocotyl) that, combined with the coleoptile, pushes the seedling above the soil surface.
* Soil moisture. Within the recommended planting range, seeds are planted as deep as possible to maximize contact with soil moisture.
* Soil texture. Soil texture influences seeding depth. In sandy soils, crops are sown deeper than in clay soils. A sandy soil has lower moisture-holding capacity and more pore space than clay soils and is less subject to crusting following rain.
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Environmental Factors Affecting Seed Germination
For germination of viable seeds to occur, certain environmental conditions must be met. Moisture, temperature, oxygen, and sometimes light are important factors. In addition, seeds often have dormancy.
During dormancy, most seeds contain less than 15% moisture. For germination to occur, seeds need to absorb a significant amount of their weight in moisture. Most seeds will not initiate germination until a critical level of seed moisture is reached. Sugar beet seed requires adsorption of nearly 100% of their dry weight; soybean and corn typically absorb 75% and 40% of their dry weight respectively. Once the germination process is initiated and the seed coat is broken, deprivation of water often causes the germinating seed to die. This explains why surface sowing of seed without incorporation often results in failure. Seed can germinate when rainfall occurs, but because the roots have not penetrated the soil, they will be unable to obtain enough water to sustain the new plant.
In contrast, drilling the seed into soil increases the chances that the root will grow down into soil moisture and protect the seed from drying out. Use of moderate pressure supplied by press wheels is a practice that also increases moisture availability to the seed by increasing soil-seed contact.
Temperature affects the rate of metabolic reactions within a plant. Plants originating in tropical or subtropic regions--for example, soybean, corn, and rice--have a higher minimum, optimum, and maximum temperature for germination than plants such as wheat, alfalfa, and flax that originated in temperate regions. Minimum temperatures for germination of cool-season temperate species ranges from 40-50[degrees]F (4-10[degrees]C). For warm season tropical species, minimum temperatures range from 50-60[degrees]F (10-16[degrees]C).
Many plant metabolic processes such as respiration require oxygen. Air diffuses into the soil, and therefore oxygen is usually not a limiting factor. However, if soils are flooded or compacted, anaerobic conditions can lead to seed death. Wild and cultivated rice are exceptional species in that their seeds can germinate under anaerobic underwater conditions.
Many species can germinate in either the light or darkness. However, certain small-seeded species such as lettuce and Kentucky bluegrass that germinate near the soil surface require light for germination.
Some seeds undergo a period of dormancy before germination. Dormancy is the failure of a seed to germinate when all required environmental conditions are met. Some level of seed dormancy is desirable to prevent seed germination while the seed is mature and still on the plant but is an undesirable trait for seed destined for planting. Seed dormancy is a natural mechanism that extends the germination time of a species--sometimes over years--and insures that some plants will become established under favorable growing conditions. Seed dormancy is induced by physical barriers, internal, chemical, and physiological factors called after-ripening.
The seed coat is a physical barrier to seed germination. Seeds of many legumes such as alfalfa and clovers contain specialized layers in the seed coat that make them impervious to water and air. This seed will not germinate and is called hard seed. These seed coatings must be abraded or scratched (scarified) to enable germination. In a soil environment, fungi or insects can disrupt these seed coats. For commercial purposes, seeds are scarified by mechanical or chemical means to disrupt the seed coat before sale.
Other plant seeds can contain chemical compounds that inhibit their germination. These chemical compounds must be leached from the seed prior to germination. Chemical inhibitors have been found in sugar beet, oat, rice, and barley.
Though seed of corn can germinate soon after maturity, seed of some cereal varieties of wheat, barley, and oat undergo a dormancy period for several months. This is called after-ripening and involves further development of the seed embryo.
The Germination Process
Germination occurs in several stages as the seed changes from a resting state to active growth.
* The first step in the germination of a seed is the absorption of water by the seed through the seed coat. The water then diffuses throughout the seed.
* The second stage is the initiation of metabolic processes within the seed. These include the activation of enzymes for the breakdown of stored foods into simpler compounds (i.e., starch to glucose; proteins to amino acids; oils to fatty acids), the development of respiration, and cell division within the embryo.
* The third stage is the growth of the embryo, the living plant. Initially, the radicle (the root) emerges from the seed, followed by the shoot.
For economic production of most crops, agronomists have identified optimal seeding rates that are specific for climatic regions (Table 13-6). These are based on an assumption of a certain level of seedling mortality. The general response of an annual crop yield to increasing populations is shown in Figure 13-12. At low seeding rates, plant populations are inadequate to use all the light, moisture, and nutrient resources. As populations increase, a point is reached when populations are optimum to use all resources. After this point, there is diminishing response to increased populations. Agriculture research continually evaluates the optimum seeding rates for crops (Table 13-7).
Seed of many crops are treated before they are packaged for purchase. The most common seed coatings are used to control soil pathogens. For example, alfalfa and corn seeds are treated with a fungicide to control soil fungi that may damage the seed before and during germination. In addition, the seeds of legumes, such as soybeans and alfalfa, are treated with a specific Rhizobium species (bacteria) that nodulates the roots of the legumes. Nodulation is the first step in the biological nitrogen fixation process (see Chapter 7).
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Broadcasting and drilling are two approaches to seeding crops. Broadcasting consists of even spreading of seed on top of the seedbed across a field randomly (not in rows) (Figure 13-13). Manual broadcasting of seeds was used for centuries to sow seeds, but the practice has been replaced by mechanization. Broadcasting is now routinely used for sowing small seeded forage legumes and grasses such as alfalfa and smooth bromegrass. Examples of broadcast equipment include the cultipacker seeder that drops seed from a hopper and then covers the seed with corrugated rollers, and air seeders that disperse seed on the soil surface. With surface broadcasting on prepared seedbeds, it is important to follow the seeding with soil-packing equipment to insure seed coverage. Some farmers practice frost seeding during winter months. Frost seeding is the broadcast seeding of desirable forage grasses and legumes while the ground is frozen. The seed is then covered as the soil freezes and thaws.
Drilling consists of depositing seed in a row at a uniform depth in a seedbed. Drills provide for greater seeding precision than broadcast seeding. Most drills have hoppers for carrying seed and fertilizers, a metering device for a specific-sized seed, and openers (the drills) for placing the seed into the soil. Many drills are equipped with instruments to control the planting depth and press wheels to insure good soil-seed contact. There are various types of drills.
* Grain drills. These drills plant grains in narrow rows that are often only 6 inches (15.2 centimeters) apart (Figure 13-14). This is the most traditional approach for seeding crops like wheat, barley, and oats, but drills are now also used for soybeans.
* No-till grassland drills. No-till grassland drills are used to improve the species composition of grasslands and pastures. Legumes such as alfalfa and clovers are interseeded into permanent cool-season grass pastures to improve productivity and forage quality. Native perennial grasses and forbs are seeded into killed sods to restore prairies. These drills are similar to grain drills, except that they must meter very small and, sometimes, fluffy seed. Because the seedbeds are usually not prepared, no-till grassland drills are heavy and often contain specialized disk openers for slicing and throwing existing vegetation (Figure 13-15).
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* Row crop planters. These types of drills are often used for corn and soybeans (Figure 13-16). Seed is deposited in rows that are usually 20-30 inches (51-76 centimeters) apart. Seed metering is very precise and drops seeds at specific spacing within a row. No-till variations of row crop planters are equipped with coulters and disks for removing the residues of previous crops (Figure 13-17).
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Crop planting dates are selected to optimize crop establishment and to maximize capture of solar energy during favorable growing temperatures. Planting dates vary considerably with crops and across environmental regions of the United States. The following general guidelines apply:
* Summer-temperate, cool-season, annual plants--such as small grains--are planted as early as possible in the spring so as to take advantage of favorable environmental conditions for germination and growth. They mature during the warm summer months.
* Summer-tropical, warm-season, annual plants--such as corn, soybeans, and cotton--are planted at later dates than cool-season small grains because of their requirements for higher temperatures for germination and their frost sensitivity (Table 13-8). Warm-season annual plants need to be large enough by early summer to capture solar energy during the warm summer months.
* Winter-annual, temperate, cool-season crops--such as small grains, clovers, and canola--are planted in the late summer to early fall as air and soil temperatures start to decrease, and soil moisture levels are generally higher. Some winter annuals such as rye grain can tolerate low temperatures and begin growing again in the spring. Most winter annuals are grown in regions of mild winter conditions, and they have significant growth during the winter.
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1. What are the two most widely used tillage approaches, and what tillage equipment is used?
2. What are the benefits of tilling the soil?
3. What is harrowing the soil, and what equipment is typically used?
4. What is the advantage of having crop residue on the soil surface?
5. What is no-till seeding?
6. Where does most of the seed that farmers use come from?
7. Identify important information provided on the seed label.
8. What does the term pure live seed mean?
9. What factors must be taken into account to achieve optimal seed establishment?
10. Identify crops that are established using broadcast seeding and those that are drilled in rows.
1. Go to a home and garden store that sells grass seed for lawns and examine the label. What is the germination rate of the seed? Does the seed contain weed seeds?
2. Visit your local extension Web site. Look up the recommended seeding rates for crops grown in your area. How do they compare to those in Table 13-7?
3. Go to the Natural Resources Conservation Service Web site. Look up the predominant tillage practices for your area. How do they compare to the rest of the country?
Acquaah, G. (2005). Principles of crop production (2nd ed.). Upper Saddle River, NJ: Prentice-Hall, Inc.
Coyne, M. S., & Thompson, J. A. (2006). Fundamental soil science. Clifton Park, NY: Thomson Delmar Learning.
Dickey, E. C., Shelton, D. P., Jasa, P. J., & Hirschi, M. C. (2001). Residue management to control soil erosion by water. Conservation Tillage Factsheet CTNC-14, West Lafayette, IN: University of Nebraska Conservation Technology Information Center.
Harpstead, M. I., Sauer, T. J., & Bennett, W. F. (2001). Soil science simplified (4th ed.). Ames, IA: Iowa State Press.
Hicks, D. R., Naeve, S. L., & Bennet, J. M. (1999). The corn growers field guide for evaluating crop damage and replant options. St. Paul, MN: University of Minnesota Extension Service.
Martin, J. H., Leonard, W. H., & Stamp, D. L. (1976). Principles of field crop production (3rd ed.). New York: Macmillan Publishing Company, Inc.
Naeve, S. L., & Hicks, D. R. (2006). The soybean growers field guide for evaluating crop damage and replant options. St. Paul, MN: University of Minnesota Extension Service.
Plaster, E. J. (2003). Soil science and management (4th ed.). Clifton Park, NY: Thomson Delmar Learning.
Sandretto, C., & Payne, J. (2006). AREI chapter 4.2. Soil management and conservation. Washington, DC:USDA-Economic Research Service.
Sund, J. M., Barrington, G. P., & Scholl, J. M. (1966). Depths of sowing forage grasses and legumes. Proceedings 10th International Grassland Congress, Helsinki, Finland. Sec1:319-322.
United States Department of Agriculture--Economic Research Service (2006). Agricultural resources and environmental indicators. Keith Wiebe and Noel Gollehon, (Eds.) Economic Information Bulletin Number 16 (EIB-16), July 2006. <http://www.ers.usda.gov/> Accessed 25 October 2007.
University of Minnesota Agricultural Experiment Station (2007). Minnesota varietal trials results, January 2007. St. Paul, MN: University of Minnesota Agricultural Experiment Station. <www.maes.umn.edu/> Accessed 9 November 2007.
University of Minnesota (1999). Minnesota soybean field book. St. Paul, MN: University of Minnesota Extension Service.
Table 13-1 Conservation and other tillage types by millions of hectares and percentage of all planted area for the United States in 2004. Reduced- till is a hybrid system that leaves 15-30% cover. USDA-ERS (2006). Millions % of planted of hectares hectares Conservation tillage: more than 30% residue cover after planting No-till 25.3 22.6 Ridge-till 0.9 0.8 Mulch-till 19.4 17.4 Reduced-till: 15-30% residue 24.1 21.5 cover after planting Conventional-till: 0-15% residue 42.3 37.7 cover after planting Table 13-2 Essential information for the commercial seed tag. Information Description Crop type and variety Identifies the plant species and its variety name Lot A specific quantity of seed that is produced in a specific location and that has a uniform level of quality Pure seed % (weight basis) of the crop's seed that is of the designated species and variety Other crop seed % (weight basis) of contaminating other crop seed Weed seed % (weight basis) of weed seed (commercial seed cannot contain noxious weed seed) Inert matter % (weight basis) of nonliving material such as soil, rocks, and cracked seed Germination % of the total seed that germinates to produce normal seedlings Date of test Year and month that the seed test was conducted (old test results may not be reliable) Origin Production site for the seed Name/address Name of the seed company or seed vendor Table 13-3 Calculation of the percentage of pure live seed and seeding rates. % PLS = 100 x [(% germination) x (% purity)] Example: 1. Given on the seed tag: % germination 92% (0.92) % inert matter 1.5% % other crop seed 0.6% % weed seed 0.1% 2. Calculate % purity (pure seed): 100% pure seed -1.5% inert matter -0.6% other crop seed -0.1% weed seed 97.8% pure seed in this seed lot (0.978) 3. Calculate % pure live seed (%PLS): % PLS = 100 x [(% germination) x (% purity)] = 100 x [(0.92) x (0.978)] = 100 x 0.90 = 90% Once you have determined the % PLS, you can use this information to determine the amount of seed necessary to seed a crop at the recommended rate. Example: 1. Given information: 55 pounds/acre = seeding rate of soybeans/acre 90% (0.90) = % PLS 2. Calculate pounds of this seed lot required: a. Seed required x 0.90 = 55 pounds/acre b. Seed required = 55 pounds/acre/0.90 = 61.1 pounds/ acre of seed from this seed lot Table 13-4 Seeding depth and seed size. Depth of seeding Seed size (number (centimeters) /kilogram) Representative crops 0.6-1.3 135,000-2,250,000 Redtop, timothy, bluegrass, fescue, white clover, alsike clover, and tobacco 1.3-1.9 67,500-135,000 Alfalfa, red clover, sweetclover, crimson clover, ryegrass, foxtail millet, and turnip 1.9-3.8 22,500-67,500 Flax, sudangrass, proso, and bromegrass 3.8-5.1 4500-22,500 Wheat, oats, barley, rye, rice, sorghum, buckwheat, vetch, and mung bean 5.1-7.6 180-4500 Corn, pea, cotton, and soybean Table 13-5 Plant populations produced from 100 seeds at various depths on two soils. 1 inch = 2.54 cm. Adapted from Sund et al. (1966). Number of Plants in Sand Depth (inches) 1/2 1 1 1/2 2 Alfalfa 71.4 72.6 54.8 40.1 Red clover 67.3 65.9 53.1 27.1 Bromegrass 70.5 64.2 48.0 29.1 Orchardgrass 61.2 56.4 30.1 12.6 Number of Plants in Clay Depth (inches) 1/2 1 1 1/2 2 Alfalfa 51.9 48.4 28.1 13.1 Red clover 40.1 35.1 14.2 7.2 Bromegrass 56.1 37.4 17.2 5.5 Orchardgrass 60.1 25.9 6.3 1.2 Table 13-6 Recommended planting rates for a diversity of crops in Minnesota. Adapted from University of Minnesota Agricultural Experiment Station, (2007). No. of No. of Pounds/ Kilograms/ seeds/ seeds/ Crop acre hectare acre hectare Barley 85 95 1,219,700 3,012,600 Corn 17 19 24,000 59,300 Kidney 115 129 105,000 259,400 Navy 42 47 105,000 259,400 Flax 42 47 3,702,600 9,145,400 Bromegrass 16 18 2,178,000 5,379,700 Alfalfa 11 12 2,178,000 5,379,700 Red clover 9 10 2,178,000 5,379,700 Oat 80 90 1,219,700 3,012,600 Rye 60 67 1,089,000 2,689,800 Sorghum 10 11 150,000 370,500 Soybean 56 63 140,000 345,800 Sunflower, non-oilseed 4 4 17,000 42,000 Sunflower, oilseed 3 3 23,000 56,800 Wheat, durham 90 101 1,089,000 2,689,800 Wheat, hard red spring 80 90 1,219,700 3,012,600 Wheat, winter 75 84 1,089,000 2,689,800 Buckwheat 50 56 740,500 1,829,100 Canola 8 9 1,089,000 2,689,800 Fieldpea 180 202 392,000 968,300 Foxtail millet 15 17 3,267,000 8,069,500 Proso millet 20 22 1,306,800 3,227,800 Wild rice 33 37 261,400 645,600 Table 13-7 Relationship between corn plant population and grain yield for corn planted prior to May 1. Adapted from Hicks et al. (1999). Plant population Grain yield (plants/hectare) population (%) 12,000 100 11,200 98 11,700 94 10,800 92 9900 88 9000 84 8100 79 7200 74 6300 67 Table 13-8 Yield loss by planting date for corn and soybean in Minnesota. There is an optimum date when it is best to plant. Planting too late will negatively affect yield. Adapted from University of Minnesota Extension Service (1999) and Hicks et al. (1999). Yield loss % Planting date Soybean Corn April 25 -- 0 April 30 -- 1 May 1 0 -- May 5 1 3 May 10 2 6 May 15 3 9 May 20 6 12 May 25 9 14 May 30 13 17 June 4 18 23 June 9 24 29 June 14 30 35 June 19 36 41 June 24 43 --
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|Publication:||Introduction to Agronomy, Food, Crops, and Environment|
|Date:||Jan 1, 2009|
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