Soybeans: No-Till And Minimum Till Guidelines

Many terms are used to describe production systems that deviate from conventional tillage. If you practice conventional tillage, you are probably using several tillage operations to prepare a clean seedbed for planting and then cultivating during the growing season. Theoretically, anything done to reduce tillage operations from a conventional program is a form of reduced tillage. You may try many different approaches, but they generally fall into the broad categories of no-till or minimum till.

Definitions

No-till means you do not prepare a seedbed or cultivate during the crop season. A common no-till practice is to plant in last year's crop stubble or small grain stubble.

Minimum till can include many different approaches but usually involves planting in an undisturbed seedbed, which may or may not have been tilled earlier. At planting you may do some limited tillage directly under the row, or you may cultivate the row middles later in the season.

Advantages of Reduced Tillage

Reduced tillage conserves soil and water and may reduce fuel and labor requirements. It can also be important for achieving timely planting. Generally, the seedbed is in better condition when it has not been tilled excessively. Moisture conservation from no tillage is especially important for double cropping.

Disadvantages of Reduced Tillage

Reduced tillage systems require careful management at critical times to be successful. A reduction in tillage is certainly not a shortcut to improve soybean production and is not a substitute for good management. More difficult weed control may be a major disadvantage, and often, increased spending for herbicides will offset any savings from reduced tillage. Special planting equipment may be needed and you may also have greater problems with stand establishment, especially in rough seedbeds.

When To Avoid No-till

Avoid fields with perennial weeds such as bahiagrass, bermudagrass, johnsongrass, nutsedge, redvines, trumpetvine creeper, etc. unless you recognize these problems up front and adjust management strategies accordingly.

Do not attempt to plant no-till on land that has a hard pan. This is particularly true for ryegrass or small grains that was grazed during the spring. Some tillage may be necessary to break this compaction zone, although this can depend a lot on when the grazing occurred, time of planting, and the time and amount of rainfall after planting.

Planting Equipment

Where crop stubble or residue is present on the soil surface, you will more than likely need a planter equipped with a coulter to slice or till a narrow slot in front of the openers. A fluted or serrated coulter is usually most effective.

Double-disk openers with positive depth control work best in placing the seed into the seed slot for maximum soil contact. A presswheel that firms the soil around the seed without leaving a depression is also very important.

In hard dry soils, penetration can be difficult. When selecting a planter, consider one with adequate weight and planter units with down pressure for greater flexibility in different soil conditions.

Where a hard pan is present, you may need some in-row tillage for minimum tillage planting. For planting in a ryegrass sod, a power tiller mounted in front of the planter and set to till an 8-inch strip directly in the row has been successful in research plots. A chisel or subsoil shank mounted to run between the coulter and planter has also been used on some farms with various results.

In Mississippi, in-row subsoiling has shown better results than no-tillage, but the results have not been as good as with the power tiller or conventional tillage. However, the power tiller and in-row subsoiler require more power and/or maintenance, and both are relatively slow methods of planting.

Applying Lime and Fertilizer

In a double cropping system, you can apply the lime and fertilizer for soybeans and the small grain during seedbed preparation for the small grain or ryegrass crop. You should apply enough phosphate and potash for both crops.

When no-tillage is to be used for several successive crops, the soil pH must be favorable (pH 6.0-6.5), and the fertility medium or high. On soils of low fertility, fertilizer applied to the soil surface may not be used as efficiently. Therefore, for these soils, planting in a "stale seedbed" after the fertilizer is incorporated in winter or early spring is preferable. You can surface apply fertilizer on low testing soils, but incorporation will minimize loss and speed reaction time. After application you can then plant soybeans without further seedbed preparation.

Crop Systems

Reduced tillage systems for soybeans often involve other crops. For no-till you should have enough crop residue on the soil surface to serve as a mulch for holding moisture, reducing erosion, and inhibiting weed emergence.

If you must provide a winter cover for erosion control, you can plant a cool season grass like ryegrass, wheat, or oats into which you can plant soybeans without tillage. Because of the cost of seeding and killing a winter cover crop, this system may not be economical unless you remove the grain crop.

Double cropping with wheat is the most popular no-till system in Mississippi. The major disadvantage has been a 5- to 10-bushel yield reduction for double-cropped soybeans. Planting an early maturing grain crop, harvesting the grain at high moisture, and using no-till planting can help minimize the soybean yield reduction due to double cropping. Your county Extension office has a detailed publication on double-cropping systems.

When planting after ryegrass or other winter grazing crops, you may need some tillage to break the compaction layer. Strip tillage over-the-row or in-row subsoiling is an option but not necessary. No-till yields are comparable to conventional plantings, but the major influence is early season weed control and environmental conditions.

Varieties

Select a variety adapted for the soil and location regardless of tillage. Since weeds are usually a concern, plant a variety adapted to your particular soil type and row spacing. For additional variety information, refer to the Mississippi State Soybean Variety Trials publications available at your county Extension office.

Row Spacing and Plant Population

For minimum till systems where cultivation is planned, use a row width that will allow for the movement of tractors and cultivators. Thirty-inch rows are a good compromise between the wide (40-inch) rows and very narrow (less than 20-inch) rows. Another approach is to leave an area wide enough for the tractor tires, with the other rows more narrow; however, these wider skips have led to increased weed problems in this zone. Many producers are placing a planter unit behind the tractor tire hopefully to get enough of a stand to help suppress weeds.

For no-till, plant in as narrow a row as possible to provide the most shade in the fastest time. However, keep in mind that very narrow rows that prevent tractor movement and directed herbicide applications will force you to apply herbicides broadcast over-the-top. If planting in hard soil or other poor seedbed conditions, you may need to plant 10 to 15 percent more than you would with conventional planting. For additional information on seeding rates and row spacings pick up a copy of Extension Publications 1194 and 1289.

Chemical Weed Control

Failure to control weeds is most often the reason for unsuccessful results with no-till soybeans. In many cases, the same herbicides are used, but without tillage you are limited to surface-applied preemergence herbicides. Minimum tillage systems may include an incorporated or preemergence herbicide, postemergence herbicides, or postemergence cultivations.

When planting no-till, you must use a herbicide to kill existing weeds before soybeans emerge. Gramoxone Extra or Roundup are usually the base herbicides used, but there are other options. Roundup is a systemic material and often better at suppressing johnsongrass, bermudagrass, and marestail.

Many of the same preemergence and postemergence herbicides available for use in conventional production systems can be used in a no-till system; however, depending upon the planting system you utilize, there may be fewer choices. For example, it is very difficult to use directed sprays when you plant soybeans into a crop stubble.

Complete information on labeled soybean herbicides, rates, and weeds controlled is available at your county Extension office.

Information given here is for educational purposes only. Reference to trade names or commercial products is made with the understanding that no discrimination is intended of other products that may also be suitable.

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