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3/18/2013 - 3/24/2013

Planter Adjustments for Dry Soil

By Mark Hanna, Department of Agricultural and Biosystems Engineering

Several factors affect the choice of corn seeding depth. Although many areas have received late winter precipitation, dry soil is still a concern in areas where tillage allows significant surface drying or precipitation has not occurred. Corn Seeding Depth:  Back to the Basics, a recent ICM News article, discusses how to select appropriate seed depth. This article focuses on planter adjustment settings and considerations if seed is planted deeper than normal due to dry conditions in the upper two inches at the surface.

Dry surface soil suggests deeper planting depths to obtain moisture for rapid germination. The seed depth adjustment on planters controls the distance between the bottom of the double-disc seed opener and bottom of depth-gauge wheels. Most planter row units have the ability to adjust this difference to at least 3 or 4 inches. Simply adjusting this depth difference between gauge wheels and seed opener, however, will not automatically mean seed is placed at the adjustment depth. A certain amount of weight or down force is required to push the seed opener into the soil before the adjacent depth wheel comes into contact with the surface. The down force required increases with increasing penetration depth. This is similar to increased force required to drive a spade deeper into the soil. 

It’s always a good idea to make sure depth-gauge wheels are in contact with the soil surface. This check is particularly necessary when planting at deeper than normal depths or if dry soil increases penetration resistance encountered by the seed opener. If gauge wheels are not on the soil surface, extra weight must be transferred to the row unit via the down force system on the parallel links attaching the row unit to the planter frame. In some cases, extra weight may be required on the planter toolbar frame to allow penetration of the seed opener. This last issue is more commonly encountered when a large number of row units are used on a given planter toolbar (e.g., narrow- or split-row planter use) or separate fertilizer injectors are used on the planter.

Rather than relying strictly on depth adjustment between the bottom of the seed opener and bottom of depth-gauge wheels an alternative approach to increasing planting seed depth to a zone of adequate moisture is to create a furrow ahead of the planter by setting row cleaner depth deeper than usual. This concept loosens soil for easier penetration of the seed opener. More aggressive or deeper depth settings may remove an inch or two of surface soil before insertion of the seed by the seed opener and depth-gauge wheels. 

Creating a furrow with row cleaners may be the simplest method to insert seed deeper than ordinarily capable with the planter’s seed depth adjustment (typically 3 to 4 inches).  This approach has worked well for some operators in previous planting situations with dry surface soil. As mentioned in the article above on corn seeding depth, this approach also carries potential risks if rains occur during early germination and growth. Rainfall can puddle and seal tilled soils affecting the ability of corn to emerge. Even if corn has emerged, excessive water runoff erodes soil and can wash seed and plants from furrows if rows are sloping. 

Contrary to planting in moist or wet soil, increasing down pressure somewhat on closing wheels can help seed-to-soil contact. Some extra down pressure on depth-gauge wheels slightly increases seed depth and increases emergence rate, bringing additional moisture into the seed zone by increasing capillary action on the soil water.

 

Summary

Many planters allow seed depth to be adjusted 3 to 4 inches. Actual depth should be checked however to ensure penetration of seed openers and accurate seed placement. Row cleaners may be used as an aid for deeper planting, but subsequent rainfall can create soil sealing or erosion. Greater down pressure than normal may aid seed-to-soil contact. 

 

Mark Hanna is an extension agricultural engineer in agricultural and biosystems engineering with responsibilities in field machinery. Hanna can be reached at hmhanna@iastate.edu or (515) 294-0468.

Evaluate Forage Stands for Winter Injury

By Stephen K. Barnhart, Department of Agronomy

Winter-dormant perennial forage plants remain dormant as long as temperatures in the ‘crown’ area, or upper few inches of the soil, remain between about  0 and 35 degrees F.  Snow cover and residual vegetative cover help to insulate the soil and stabilize soil and crown temperatures. Under ideal conditions, as spring temperatures warm through March, the plants ‘break dormancy’ and regrow normally into the spring. Winter injury and winter kill can occur under several conditions: if there is no snow cover and crown temperatures go much below 0 degrees F;  when mid-winter ‘warm spells’ cause the plants to ‘break dormancy’ early and are then more susceptible to late-winter cold crown temperatures; and,  when plants are submerged in frozen, ponded water in low-lying areas during the winter.

This winter, the crown temperatures have likely not been cold enough for direct cold injury, even without snow cover. While day temperatures have been warmer than normal for short periods through February and early March, night temperatures have, hopefully, been cold enough to prevent the plants from breaking dormancy. A significant concern are the localized, frozen, ponded areas. How well did they handle this winter? It is time to go find out.  

 

Stand evaluation

When evaluating alfalfa in late winter for winter injury, consider both the number of plants per square foot and, for alfalfa, the age of the stand. Crown and root diseases also have a major effect on stand reduction of legumes, so plants should be checked for dead, dying or diseased crown and root tissue.  Winter-injured plants may survive satisfactorily, but are often slow to recover in spring, so a quick decision to destroy a winter injured stand is not recommended.
 
Wait until the spring regrowth is about 3 to 4 inches high. Select random stand count sites. Check at least one 1-square-foot site for every 5 to 10 acres. Dig up all of the plants in the 1-square-foot area. Inspect for new growth and the crown and buds to determine if the tissue is still alive. Then count the number of live plants per square foot. Use Table 1 to begin your rating of the stand. Next, split the taproots and evaluate their general health. The core of a healthy taproot is firm and creamy white. Damaged or dying taproots are yellowish brown to chocolate brown in color and watery or dry and fibrous in texture. Only healthy plants will contribute significantly to yield, so if the taproots are more than 50 percent diseased, reduce your initial stand count accordingly.

Table 1.  Age of stand and rating of winter survival.

 

Good

Marginal*

Consider Reseeding

 

Plants per square foot

Year after seeding

+12

8 to 12

Less than 8

2

+8

5 to 6

Less than 5

3**

+6

4 to 5

Less than 4

4 and older**

+4

3 to 4

Less than 3

* Healthy alfalfa plants in thin stands often produce more individual stems per plant and compensate some in yield potential.

** If 50 percent or more of the plants have crown or root rot, consider reseeding.

 

Plan your management this season, based on your stand evaluation.

  • If stands are winter-injured, but will be harvested this season, allow plants to mature to 10 to 25 percent bloom or later, before cutting. 
  • Increase cutting height to 3 to 4 inches.
  • Maintain good fertilizer and insect management.
  • If stands are severely winter injured, and you have incurred a significant loss to planned stored forage, plan to reestablish a new hay field this spring and begin to plan for any needed supplemental harvested and stored forage needed until the new seeding becomes adequately productive.

Assess red clover stands similarly.    

Overwintering perennial forage grasses often survive better than winterhardy legumes. However, orchardgrass and ryegrasses are more susceptible to winter injury. Visual evaluation of grass regrowth and vitality of crown tissue is suggested when evaluating winter survival of pastures.

Reseeding in hayfields or pastures might be needed. Reseeding more alfalfa into or immediately after a two year old or older stand is not recommended.  Overseeing or drilling grasses or red clover into thin or winter damaged stands should be done from now through April. Delaying seeding increases the risk of weed and surviving forage plant competition and seedling loss to increasingly dry and hot soil surface conditions of early summer.

Iowa State University Extension Publications for further information:

Evaluation for winter injury /Publications/PM1362.pdf

Selecting forage species /Publications/PM1792.pdf

Establishing new forage stands
/Publications/PM1008.pdf

Interseeding and no-till renovation /Publications/PM1097.pdf

 

Stephen K. Barnhart is an extension forage specialist. You can e-mail him at sbarnhar@iastate.edu.



This article was published originally on 3/25/2013 The information contained within the article may or may not be up to date depending on when you are accessing the information.


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