NDSU Crop and Pest Report

Plant Science


ISSUE 3  May 16, 2002

 

MINIMUM STANDS FOR CROPS

Wet, cold soil conditions bring with it concern for erratic crop emergence and poor plant stand establishment. Some crops such as small grains, canola, sunflower and soybeans can compensate for low plant populations. Stands will be poorly established if seed was planted into wet soils and crusting occurring over the seed rows.

Crops will compensate for stand reduction through tillering, branching or increased head or kernel size. Listed below is the minimum stand of several crops to avoid major yield reductions when making decisions on tearing up the field and replanting.

Crop

Minimum Stand

% of Normal Stand

Small Grains

8-10 plants/sq. ft.

40-60

Flax

12-15 plants/sq. ft.

30-40

Safflower

2-2.5 plants/sq. ft.

40-50

Canola, Mustard

3-4 plants/sq. ft.

40

Sunflower

10-12,000 plants/a

50-60

Soybean

50-75,000 plants/a

33-50

Field peas

3-5/sq. ft.

40-70

Corn: Irrigated

Corn: Dryland

Varies by
region of state

Varies by
region of state

70


60

Dry Beans
     Navy

     Pinto


45-60,000 plants/A

28-40,000 plants/A


50-60

40-50

Even stands below 12 plants per square foot of barley and oats have yielded near normal because they typically tiller more than spring wheat which typically tillers more than durum. Refer to NDSU Extension Circular A-934, "Replanting after Early Season Crop Injury" for further information. Also available on the web at:

http://www.ext.nodak.edu/extpubs/plantsci/crops/a934w.htm

 

COUNTERING EFFECTS OF LATE PLANTING

In North Dakota planting small grains after May 15 typically results in 1.2 to 1.7% per day reduction in yield. The reduced yield is a result of fewer tillers and smaller heads. Some compensation can be made with increased seeding rates.

Yield potential in small grains is a function of three components: head number, kernel number per head and the weight of each kernel. As any one of these components is increased or decreased yield changes accordingly. Heads produced per unit area is directly related to seeding rate, or crop stand, and tillering during early vegetative development.

Yield reduction due to late planting is a result of longer days and the increased probability for high, potentially detrimental temperatures during the 3 to 6 leaf stages. Yield potential, or head number and kernel number is determined during this period. The long days and hot temperatures during early vegetative development results in fewer heads per plant and spikelets per head and a lower yield potential. The recommended normal seeding rate for small grains in North Dakota is 1.25 to 1.50 million live seeds per acre, or about 30-35 seeds per square foot.

The lower yield potential can be offset in part by increasing seeding rates of small grains. A ten percent increase above typical seeding rates for every ten days planting is delayed beyond May 15 should be sufficient. Late planting generally results in higher grain protein. While high protein is a plus in wheat, high protein barley may not make malt quality. If barley is in your crop plan, plant it first and make sure total nitrogen does not exceed your yield goal. Nitrogen recommendations for malting barley are 1.5 lbs/acre for every bushel of expected yield, and 2.5 lbs/acre for every bushel of wheat.

Expected yield reductions when planting after May 15 in North Dakota.

Crop

Percent Yield Loss/Day

Wheat
Barley
Oat
Soybean
Irrigated Corn
Dryland Corn
Flax
Dry Bean
Crambe
Canola

1.5
1.7
1.2
0.8
1.5
1.0
2.3
0.3
0.9
1.9

 

WET CONDITIONS REQUIRE PATIENCE

Demonstrating some patience now will be a key if producers want to avoid potential problems later in te growing season. Waiting until the soil has dried sufficiently before working will result in more favorable seedbed conditions maximizing plant stands and final yields.

Tillage of wet soils for seedbed preparation can result in excessive clod formation, poor seed soil contact, and uneven and dried-out seedbed, poor mixing and incorporation of chemicals, uneven erratic seedling emergence, and reduced plant stands. Don’t be in a big hurry to work wet fields. Patience is the best recommendation when fields are wet. Waiting 1to 2 additional days usually will not lengthen the growing season, but will greatly aid in obtaining a good seedbed for planting and to maximize plant stands.

When planting in compacted wet conditions the seed is put in an anaerobic environment. When seed germinates in an anaerobic environment, the lack of oxygen generally results in the death of the germ. Seeds that do survive will be weak and the wet soil conditions may be for favorable for the development of soil borne pathogens that otherwise may not be a problem. The end result is reduced stands and lower yields.

Germination of wheat or barley in compacted conditions will hinder coleoptile growth, preventing shoot development and soil penetration of the radicle, retarding root development. In addition, any crusting that occurs will further prevent the coleoptile from emerging resulting in seedling loss. The end result of both is an erratic and reduced stand. Uneven crop stands typically yield lower than uniform stands due to direct competition of plants at different stages of growth next to one another.

 

CORN AND BEAN ROW SPACING

Beans:

The practice of planting soybean and dry beans in narrow rows can result in increased yields but can also create production and some harvesting problems.

Some advantages of narrow row spacing for beans include:

Narrow rowed beans can have their problems also. One chief concern is for weed control. Row-cultivation is not possible, therefore herbicides and rotary hoeing are the means for control of weed problems. Field history of white mold (Sclerotinia stem rot) can be a severe threat in narrow-rowed soybean and dry edible bean. The canopy is slow to dry during the day following rain, irrigation or heavy morning dew. This wet environment can greatly enhance or magnify the white mold problem in bean fields.

Both soybean and navy bean can be successfully grown with narrow row spacings. Pinto bean with an indeterminate vining growth habit (type III) should be planted in 30-inch row spacings or at the very minimum 22 inches spacings. Soybean and navy bean can be grown in narrow spacings such as 6-7 inches, 12-14 inches or 20-inch row spacings with fewer problems and increase the yield potential. Check the plant growth characteristics of the bean varieties and only plant those with an upright, determinate and narrow growth habit in narrow row spacings.

Corn:

There has been a lot of interest in reduced row width spacing of corn in recent years. In irrigated corn studies conducted at Oakes averaged over two years, 20-inch row width corn out performed 30-inch spaced corn 192 bu/A to 170 bu/A, respectively. This +22 bu/A advantage was averaged over three hybrids with 80, 90, and 100 day relative maturity ratings. In an Agronomy Abstracts report, a corn row spacings survey indicated increased corn yields with narrow spacings. The corn grain yield increases for 20-inch corn rows ranged from 2.3 to 7.8%. Yield response to 20-inch corn rows was similar regardless of plant populations ranging from 18,000 to 36,000 plants/A.

Narrow rows make more efficient use of available light and also shade the surface soil more completely during the early part of the season while the soil is moist. This results in less water being lost from the soil surface by evaporation. The more uniformly you can seed plants the better as long as soils have adequate moisture. Uniform seeding maximizes photosynthesis and the proportion of water that is used in growth processes rather than evaporated from the soil.

Before going to narrow row spacing the grower should consider hybrid selection, machinery suitability for this row width (also silage harvesting equipment), the extra time needed to plant, cultivate and harvest, and the extra herbicide for band application over the row.

In summary, narrower row widths offer more yield potential with today’s modern corn hybrids. The data indicate that yields should rarely be less than what you could achieve in 30-inch row width, and that reduces the risk of making the switch. Planting rates do not necessarily have to be increased and hybrid choices can be the same as you would use in a wider row width. As one looks to the future for equipment updates and changes, this information may help calm some of your fears about moving to a narrow row width corn.

Duane R. Berglund
Extension Agronomist
dberglun@ndsuext.nodak.edu


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