By Dr. Jim Beuerlein
Multiple cropping is the establishment and harvest of a second crop in the same season that a first crop is harvested. A number of multiple cropping systems using winter cereals (wheat, barley, rye, and spelt) as a first crop and soybean, sunflower, forage seedings and rapeseed (canola) as a second crop are either commonly used or are feasible. Corn grown for silage following a first cutting of hay and soybean after winter wheat are the most widely used double crop systems in Ohio. There are two forms of multiple cropping: 1) double cropping and 2) relay cropping. With double cropping the second crop is planted following the harvest of the first. Relay cropping consists of interseeding the second crop into the first crop before it is harvested. Both systems are employed in Ohio, with double cropping being the preferred system south of I-40 and relay cropping to the north of I-40. The relay technique enables the production of a second crop in the northern part of Ohio where time for a second crop following wheat harvest is usually inadequate.
Multiple cropping drastically reduces the elapsed time between successive crops and therefore can greatly increase the disease pressure for both crops. Where intense multiple cropping is practiced, the beneficial effects of crop rotation (weed, insect, and disease control) are totally negated.
There are two primary requirements for profitable multiple cropping:
Because the soybean crop is photoperiod sensitive and matures in response to day length, it is ideally suited for multiple cropping systems where planting dates for the second crop are later in the season and can be variable due to weather.
Currently, most multiple cropping systems depend solely on a combination of rainfall and stored soil moisture to supply adequate water for two crops. Irrigation can be used as a supplement for soils with a less than adequate water supplying capacity and/or inadequate rainfall. While irrigation can greatly increase the consistency of crop yields, it also increases the cost of production. In the eastern Corn Belt, the small grain crop generally removes water from only the top foot of soil and rainfall is typically greater than 3 inches per month. If the top 3 inches of soil is dry when the second crop is planted, germination is greatly slowed until the receipt of adequate rainfall. There also must be adequate surface soil moisture to enable the root system to grow into moist soil where water availability is more consistent. Because the water requirement is so large for multiple cropping, it is generally most successful on soils with large water supplying capacities that are sometimes referred to as “good corn soils.” These soils are typically deep (54” to 72”) with loamy textures throughout the soil profile, and have high water supplying capacities in the range of 0.15 to 0.25 inches of available water per inch of soil. They also have good internal drainage, either natural or artificial, and little restriction to root development and water movement such as zones where the soil bulk density is greater than 1.6. Depending on the weather during the growing season, a soybean crop can produce about 2.5 bushels of soybean for each inch of rainfall and water removed from the soil. A wheat crop will usually use 6 to 8 inches of rainfall and/or soil water. The receipt of 18 inches of rain distributed somewhat evenly during May through September will usually allow the production of a 70-bushel wheat crop followed by a 30 to 40 bushel soybean crop. Soil pH throughout the rooting zone should be in the range of 5.8 to 7.2 (plow layer 6.5 to 7.0) to allow for maximum root growth and water uptake. Soil permeability should be greater than 0.6 inches per hour to allow rainfall to move into and through the soil. The soil shrink-swell potential should be low to moderate to reduce damage to the root system as the soil dries and cracks.
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| Figure 8-1. Relay crop soybeans between rows of wheat, ready to harvest. |
Legumes and grasses (alfalfa, clovers, brome, tall fescue, orchard, timothy) in mixtures or in pure stands are sometimes broadcast seeded into small grains in late winter when the ground is still frozen. In these instances the primary purpose of the small grain is weed control, although some grain or forage is sometimes harvested. These forage seedings are usually intended for either livestock pasture, hay production or for soil improvement. Requirements for all methods of forage establishment are discussed in Chapter 7, Forage Production. Seeding a forage crop without a cereal companion crop is the preferred method.
A legume cover crop, such as red clover or vetch, is sometimes interseeded into winter grains to provide a source of nitrogen (N) for a corn crop the following year. Red clover is easily established, and the amount of N produced by one year of growth is sometimes adequate to support a normal corn crop. Herbicides that could injure the clover must be avoided if weeds are a problem in the small grain. Legume cover crops are also used intermittently for hay or grazing, but this would reduce their N value for a subsequent corn crop. In most situations, a legume cover crop is used to benefit the following crop, but its value as a nitrogen source varies, and the following crop may need additional N fertilizer. With emphasis on no-till crop production, the N value of various legume cover crops is reduced by 40 to 70 percent, because the legume residue is not incorporated into the soil.
Early planting of the second crop is essential for success, which requires harvest of the wheat as early as possible. Potential double crop soybean yield decreases by one bushel for each day that planting is delayed after June 20. Early wheat harvest can be accomplished by planting an early to mid-maturity wheat variety soon after the fly-free date in the fall and harvesting when the grain moisture decreases to 18% to 20% and then using air with or without supplemental heat to dry the grain. These actions combined can save several days that would normally be used to field-dry wheat to 10 to 14 percent moisture. If a grower wishes to maximize wheat production because of the high value of wheat relative to a following crop, early harvest may be less important. Using later maturing varieties and optimum levels of N fertilizer generally increases wheat yields, but delays harvest.
Below-normal temperatures in June delay wheat maturation, which may require growers to reconsider planting the second crop. For someone considering double cropping, it may be necessary to have two wheat varieties differing in maturity available in the event that wheat maturation is delayed. In southern Ohio, soybean varieties with maturity ratings of 3.4 to 3.9 will usually mature before the first freezing temperature if planted in June. Other than selecting a variety that matures before the first freeze, variety selection is not as important for double cropping as it is for a full season crop. Ohio studies have shown that early planting and July-August rainfall have a much greater impact on double crop soybean yield than does variety.
Straw remaining after grain harvest must be managed so as not to interfere with planting the second crop. Some stubble may be left to provide mulch cover. Leaving an 8 to 12-inch stubble with the combine and baling the cut straw is an efficient practice and marketing the straw adds income from winter wheat. Alternatively, the straw can be chopped and spread evenly on the field. Usually, a no-till planter or no-till drill can plant through chopped straw, if the soil is not excessively wet or dry and hard.
Soil moisture at the time of planting the second crop is critical for its success, because average rainfall in July and August often does not replace the moisture used by the second crop. Table 8-1 shows that the probable soil moisture deficit is less than the potential maximum deficit, because a crop does not usually transpire moisture at a maximum rate as the soil dries. In most years, moisture used by wheat in May and June is replaced by rainfall, but in dry seasons some subsoil moisture may be used, leaving an inadequate amount of water for the second crop. Soils with low available water holding capacity are not suitable for double cropping soybeans. Generally, such soils are poorly drained, somewhat poorly drained without tile, eroded, or sandy. Growers should also be aware of the water holding capacity of their soil, and rainfall in May and June when planning to double crop soybeans after wheat. An important rule of thumb to consider is: “if June is dry, don’t try to double crop.” Increased nitrogen application for the small grain produces more vegetation, which increases soil moisture use. Because wheat uses moisture from the upper 8 to 12 inches of soil, growers should be aware of the moisture remaining below that depth.
| Table 8-1: Estimated Moisture Balance (Inches) in North Central Ohio Soils for Double Crop Winter Wheat and Soybeans.* | ||||
| Month | Average Precipitation | Average Open Pan Evaporation | Cumulative Soil Moisture Deficit | |
|---|---|---|---|---|
| Potential | Probable | |||
| May | 4.0 | 5.2 | 1.2 | 1.0 |
| June | 4.0 | 6.2 | 3.4 | 2.8 |
| July | 4.2 | 6.6 | 5.8 | 4.2 |
| August | 3.7 | 5.8 | 7.9 | 5.9 |
| September | 3.1 | 4.2 | 9.0 | 6.5 |
| * Poorly drained soils with fragipans may hold as little as 5 inches available water at field capacity, whereas well-drained deep soils may hold more than 10 inches in the rooting zone. | ||||
Because of the short growing season remaining after wheat harvest and other time constraints, double crop soybeans should be planted no-till. The surface residue associated with no-tillage planting helps reduce moisture lost by evaporation and increases rainfall infiltration. In dry years, no-tillage planting can make a difference between satisfactory and unsatisfactory seed germination resulting from the moisture saved. A goal should be to plant the second crop on the same day the first is harvested. Narrow row, no-tillage planters equipped with residue cutting coulters and double disk openers have performed well for double cropping, but modern no-till drills are excellent implements also. Because double crop soybeans do not grow very tall, they should be planted in narrow rows (7.5”) and planted at high seeding rates (minimum of 250,000 seeds per acre) to obtain maximum leaf canopy and yield.
Weed control is not especially difficult with ordinary double cropping. The break between crops allows the use of a nonselective herbicide, such as Gramoxone Extra or Glyphosate, to remove established weeds and the use of Glyphosate and glyphosate tolerant soybeans can be used to control weeds that develop following soybean planting. Occasionally, broadleaf weeds, such as Canada thistle or ragweed, become established in winter wheat fields and interfere with grain harvest or with the following soybean crop. These weeds can be controlled in the wheat crop with application of 2,4-D amine; 2,4-D ester; MCPA; dicamba; or Buctril. At the wheat hard-dough stage, 2,4-D amine can be used to control some weeds that might be a problem for the following soybeans. Always read the herbicide label to ensure compliance with requirements for use.
Central and northern Ohio are near the limit where ordinary double cropping of soybeans is practical because of late harvesting of wheat and early autumn frosts. For these areas, relay intercropping offers increased yield potential because the second crop is already established at the time the first crop is harvested. Improvements in winter wheat and soybean varieties, as well as equipment and crop management, make these two species especially well-suited for relay intercropping.
For the relay intercropping system, soybeans are planted into standing wheat with a no-till planter or drill beginning in early May and can continue as long as damage to the wheat can be minimized. Early June should be the latest interplanting time because of a significant decrease in soybean yield potential after that period and increased potential to damage the wheat crop. The optimum time for interplanting soybeans into the 10-15 inch space between wheat rows is late May to very early June. Growing wheat in wide rows facilitates the interplanting of soybeans. The spacing between wheat rows may vary as needed to accommodate implement wheels. When planting wheat, plugging various seeding units allows the placement of disk openers in a pattern to accommodate tractor and planter wheels. Both wheat and soybeans can be planted with the same equipment or different planting tools may be used for the two crops. Any planting tool is satisfactory, provided that 18 to 24 wheat seeds are planted per foot of row and are evenly spaced. Row arrangement depends on available equipment and whether or not the grower emphasizes production of wheat or soybeans. Wheat row spacing has little effect on wheat yield and good yields can be obtained using wheat rows spaced 15 inches apart. Table 8-2 shows the effect of variety and row spacing on wheat yield in 2001.
| Table 8-2: Effect of Variety and Row Spacing on Grain Yield and Agronomic Characteristics of Wheat at Two Locations (Bucyrus and Wooster) in Ohio in 2001. | ||||||||||
| Height* | Erect** | Lodging | Test Wt. | Yield | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Company | Entry | 7” | 15” | 7” | 15” | 7” | 15” | 7” | 15” | |
| —in.— | —%— | —lb/bu— | —bu/ac— | |||||||
| Wellman | W101 | 35 | 34 | 1 | 0 | 0 | 55.8 | 56.3 | 77.8 | 77.4 |
| Stine | 455 | 40 | 39 | 1 | 23 | 1 | 53.9 | 55.2 | 74.3 | 77.6 |
| Beck’s | 104 | 41 | 40 | 1 | 0 | 0 | 55.7 | 55.7 | 72.1 | 67.2 |
| AgriPro | Gibson | 35 | 34 | 2 | 0 | 0 | 57.5 | 57.0 | 73.6 | 70.1 |
| Peterson Genetics | 980329 | 37 | 36 | 2 | 0 | 0 | 52.9 | 52.2 | 72.3 | 69.4 |
| J.G. Limited | 144J | 36 | 35 | 1 | 15 | 4 | 54.3 | 55.5 | 69.3 | 67.7 |
| Ag Alumni | INW 9811 | 32 | 31 | 2 | 0 | 0 | 56.2 | 55.9 | 74.4 | 70.9 |
| AGRA | Zorro | 37 | 35 | 2 | 10 | 0 | 57.5 | 56.7 | 71.6 | 67.2 |
| ShurGro | 1530 | 36 | 35 | 1 | 6 | 0 | 53.4 | 55.2 | 76.7 | 73.4 |
| Croplan | 527W | 41 | 39 | 1 | 12 | 0 | 53.5 | 54.4 | 63.5 | 62.0 |
| Pioneer | 25R37 | 37 | 36 | 2 | 14 | 0 | 59.1 | 57.4 | 88.8 | 80.9 |
| Bio Plant Res. | BW 244 | 41 | 40 | 1 | 1 | 0 | 54.8 | 53.9 | 67.1 | 63.2 |
| PSL Genetics, Inc. | PSL 9903 | 40 | 39 | 1 | 14 | 0 | 56.0 | 56.0 | 62.2 | 61.7 |
| J.G. Limited | SR 01488J | 39 | 38 | 1 | 24 | 3 | 54.5 | 55.8 | 73.3 | 72.2 |
| AGRA | Vicar | 35 | 34 | 2 | 0 | 14 | 52.7 | 50.6 | 69.1 | 64.0 |
| AGRA | Lisbo | 39 | 38 | 2 | 0 | 0 | 59.3 | 57.8 | 86.8 | 81.4 |
| AGI | 540 | 41 | 39 | 2 | 0 | 5 | 59.0 | 58.2 | 67.1 | 66.8 |
| NK | Coker 9474 | 38 | 36 | 2 | 5 | 0 | 59.6 | 59.4 | 72.8 | 69.8 |
| AgriPro | D952883 | 39 | 38 | 3 | 2 | 0 | 53.4 | 53.3 | 68.9 | 62.9 |
| Peterson Genetics | W301 | 36 | 35 | 2 | 17 | 0 | 55.5 | 55.7 | 72.3 | 71.1 |
| Direct Ent. Inc. | DEI 685 | 42 | 40 | 1 | 15 | 10 | 54.5 | 56.8 | 70.7 | 74.2 |
| Hubner’s | H201 | 40 | 39 | 1 | 24 | 0 | 55.9 | 56.0 | 74.3 | 78.1 |
| AGRA | Honey | 37 | 36 | 1 | 4 | 3 | 54.3 | 54.3 | 78.8 | 75.1 |
| HIGH | 42 | 40 | 1 | 25 | 14 | 59.8 | 59.0 | 90.4 | 82.3 | |
| MEAN | 38 | 37 | 1.5 | 8 | 2 | 55.6 | 55.6 | 72.9 | 70.7 | |
| LOW | 32 | 31 | 3 | 0 | 0 | 51.7 | 50.5 | 60.4 | 59.3 | |
| LSD (0.3) | 0.9 | 0.80 | 0.3 | 11 | 5 | 1.3 | 0.9 | 4.6 | 4.1 | |
| * Height in inches. | ||||||||||
| ** Growth Habit: 1 = bushy or closed canopy; 2 = intermediate; 3 = erect or open canopy (good for relay cropping). | ||||||||||
Wheat and soybean yields produced using modern relay cropping techniques and systems are typically about 90 percent and 50 percent respectively of full season yields when adequate moisture is available for the relay soybean crop. Economics have generally favored using wider or fewer wheat rows, sacrificing some wheat yield in favor of increased soybean yield. The example budget in Table 8-3 shows that returns are highest with intercropping, next highest with monoculture soybeans, and lowest with monoculture wheat. These returns reflect the relatively high yield and high unit price of soybeans. In this case, intercropping profitability is increased by sacrificing wheat yields to increase soybean yields. Changing grain prices and input costs may shift the emphasis to either crop.
| Table 8-3: Comparison of the Production Budgets of Monocrop Wheat and Soybeans with a Relay Crop System. | ||||||
| Typical Budgets for Wheat, Soybeans, and Intercrop Using Six-Year MRI Replicated Plot Average Yields and Loan Rates for Grain Prices | ||||||
|---|---|---|---|---|---|---|
| Monoculture | Intercrop | |||||
| Unit Price | Wheat | Soybean | Wheat | Soybean | ||
| Item | 77 bu | 54 bu | 73 bu | 30 bu | ||
| Receipts | Wheat | $ 2.50 | $ 193.00 | $ 183.00 | ||
| Soybean | $ 5.40 | $ 292.00 | $ 162.00 | |||
| Variable Costs | ||||||
| Seed | Wheat | $ 7.00 | $ 14.00 | $ 14.00 | ||
| Soybean (RR)4 | $ 18.00 | $ 25.00 | $ 10.00 | |||
| Fertilizer1 | N | $ 0.20 | $ 16.00 | $ 15.00 | ||
| P2O5 | $ 0.24 | $ 12.00 | $ 10.00 | $ 11.00 | $ 6.00 | |
| K2O | $ 0.12 | $ 4.00 | $ 9.00 | $ 3.50 | $ 5.00 | |
| Herbicide | ||||||
| 2,4-D Ester | 1 pt | $ 16.00 | $ 2.00 | $ 2.00 | ||
| Roundup | 26 oz | $ 8.00 | ||||
| Select (grass spot spray)2 | $ 5.00 | |||||
| Fuel, lubricants, trucking | $ 6.00 | $ 6.00 | $ 6.00 | $ 4.00 | ||
| Repairs | $ 7.00 | $ 12.00 | $ 7.00 | $ 7.00 | ||
| Miscellaneous | $ 12.00 | $ 12.00 | $ 6.00 | $ 6.00 | ||
| Interest on operating capital (10% for 6 mos) | $ 5.00 | $ 5.00 | $ 5.00 | $ 2.00 | ||
| Fixed Costs (less land and management) | ||||||
| Labor 2 hrs @ $8/hr | $ 16.00 | $ 16.00 | $ 16.00 | $ 16.00 | ||
| Machinery and equipment3 | $ 45.00 | $ 45.00 | $ 23.00 | $ 22.00 | ||
| Land charge | $ 90.00 | $ 90.00 | $ 45.00 | $ 45.00 | ||
| Total Costs per Acre | $ 229.00 | $ 238.00 | $ 153.50 | $ 128.00 | ||
| Per Acre Returns to Management | $ (36.00) | $ 54.00 | $ 63.505 | |||
| 1 Crop removal applications of phosphorus and potassium applied. | ||||||
| 2 Assumes spot spraying ¼ acreage; tank mix would cost about $20 per acre. | ||||||
| 3 Assumes splitting machinery and land charge between the soybean and wheat crop. | ||||||
| 4 Roundup Ready soybeans planted in conventional systems, now RR in MRI system. | ||||||
| 5 Represents return per acre for both wheat and soybeans. | ||||||
| Original budget from Profitable Wheat Management, Revised by Dr. S. Prochaska. | ||||||
Use of early-maturing wheat varieties is not as important for relay intercropping as for double cropping, but harvesting wheat at high moisture (18 to 20 percent) allows for early release of the soybeans and decreases interference of soybeans with wheat harvesting. Test weight and quality of wheat is improved by early harvest (higher grain moisture), but the wheat must be dried for storage. It is important to understand that somewhat vigorous wheat is required in this cropping system to suppress soybean growth until the wheat is mature. Otherwise, soybeans grow too tall and are damaged during wheat harvest. If soybeans get too tall and wide row spacings are being used, shields may be added to the combine cutter bar to cover the cycle and push the beans down to prevent cutting the tops off excessively tall soybeans while harvesting wheat.
If the wheat stand and its vigor are poor in the spring, either refrain from interplanting soybeans or wait until wheat is headed before interplanting. In several research trials, the height of early May interplanted soybeans was about two-thirds that of wheat at harvest in early July, and were damaged during wheat harvest. Best results with intercropping in Ohio to date have been with soybeans planted in late May to early June when wheat heads are emerging. Traffic associated with plantings after this time tends to damage wheat and reduce its yield.
Improvements in machinery design, wider equipment, and modifications to confine traffic to the barren strips in skip-row wheat plantings eliminates some crop damage. Shields to protect wheat from tires and planter units are useful additions to the equipment when wheat rows are spaced 10 to 12 inches apart. Narrow rows should be carefully managed with respect to making wheel width and equipment adjustments to avoid damage to the wheat from soybean interplanting or to soybeans from wheat harvesting. In some cases, using narrow dual wheels on combines will reduce damage to the soybean crop during wheat harvest. Damage to soybeans increases progressively with decreasing wheat row spacing. During wheat harvests straw should be chopped and evenly spread to avoid smothering the soybeans.
It is very important that the wheat not lodge prior to harvest so that it can be harvested without excessive damage to the soybeans. To prevent lodging, use stiff straw, lodging resistant varieties and limit applications of nitrogen fertilizer. Ohio results have shown that the spring application of 75 pounds of nitrogen per acre (following soybeans) maximizes wheat yield without causing excessive lodging. Seeding rates for soybeans should be 6 to 7 seeds per foot in 15-inch rows and 4 to 5 seeds per foot of 10-inch wide rows. Seed treatment with Apron XL or Allegiance FL is encouraged to help control root-rot diseases, and the chosen varieties should have an Rps gene and good partial resistance to Phytophthora root and stem rot. The recommended seeding and nitrogen application rates for the wheat should not be exceeded to ensure that lodging of the wheat does not occur. The least amount of wheat lodging slows harvest, reduces grain quality and increases the potential of damaging the soybean plants during wheat harvest.
In northern Ohio, full season soybean varieties (relative maturity 3.5 to 3.8) have performed best in this cropping system when planted at the end of May. Later maturing varieties can be used in central Ohio. Early June plantings require slightly earlier maturing varieties than late May plantings. Short season varieties, (relative maturity 2.8-3.1), flower too soon after planting and do not produce enough vegetative growth to provide a complete leaf canopy for maximum sunlight interception and therefore produce poor yields.
Soil phosphorous and potassium levels should be greater than 15 and 150 ppm, respectively. Twenty to 30 pounds of nitrogen should be applied at wheat planting to encourage increased fall growth, and earlier jointing and heading in the spring. Spring nitrogen applications should be made between March 1st and April 15th at the rate of one pound per bushel of yield goal.
Weed control for the soybean crop in a relay intercropping system can by accomplished by the use of Glyphosate and Glyphosate-tolerant varieties. Weed control recommendations for non-Glyphosate tolerant varieties can be found in Weed Control Guide for Ohio Field Crops, Extension Bulletin 789, available at all county offices of Ohio State University Extension and on the Internet at: agcrops.osu.edu/weeds/documents/2005WeedControlforOHandIN.pdf
This system uses rows spaced 15-inches apart for both the wheat and the soybeans and can be accomplished with equipment already available on the farm. With this system the soybeans are planted in early May rather than at the end of May as a means of eliminating damage to the wheat plants while planting the soybean. A full-season soybean variety is used in this system, and the seed coated with the new, patented IntelliCoat® polymer seed coating, RELAY™ CROP, is designed to delay germination until wheat head emergence in late May/early June. The IntelliCoat polymer seed coating is a new product available from Fielders Choice in Monticello, Indiana. For more information on this product look on the Internet at: www.intellicoat.com.
In early May, wheat plants are relatively small, and there is little chance of plant damage while planting the soybeans. The tractor should have narrow tires (10” to 13”) so as not to run over rows of wheat plants. Both grain drills and planters are satisfactory for this system as long as the soybean row is placed midway between the wheat rows. The major difference in this system and the normal relay intercrop system is the earlier planting of seed with a special coating to delay germination. As with the normal wheat/soybean relay intercrop system, the wheat variety must not lodge.
The varieties selected for use in this system should have an erect growth habit and medium plant height. The yield potential of wheat grown using this system is 85% to 90% of non-intercropped wheat grown in 7.5-inch wide rows. The seeding rate for 15-inch-wide wheat rows should be 18 to 24 seeds per foot of row, which cuts the seed cost per acre in half and partially compensates for the reduced wheat yield. The agronomic characteristics of wheat varieties are presented in Ohio Wheat Performance Trials results, available from any county Extension office and on the Internet at: www.agcrops.osu.edu.
Aerial seeding is primarily an emergency seeding method for fall-seeded small grains, but can be used to save time when other crops are being harvested. The time saved can sometimes offset the increased seed and seeding costs by permitting the timely harvest of other crops.
Planned aerial seeding of small grains is sometimes made into soybeans just before leaf drop so that the soybean leaves will provide some mulch cover for the seed. Sometimes, this occurs some weeks before the fly-free date. If the seed germinates before the fly-free date, there is an increased risk of infestation of Hessian fly and viral and foliar diseases. However, there is often insufficient soil moisture and/or rainfall for germination of seed due to greatly reduced seed-to-soil contact. This usually results in delayed germination and an extended germination and emergence period. Seeding rates should be increased by at least 50% to compensate for these adverse seeding conditions. If the seed has not germinated by the time of soybean harvest, shallow tillage to cover the seed will improve germination.