NDSU Crop and Pest Report
Soils


ISSUE 9  June 27, 2002

 

FERTILIZING ANNUAL FORAGES

Nitrogen availability for annual forages is important because enough nitrogen is needed to produce good tonnage and quality, but excessive rates may lead to nitrate poisoning of livestock. Nitrate does not reduce in hay during curing, as prussic acid (cyanide) of sorghums and sudan-grass will, so attention to residual levels of nitrogen in the soil is important. Most of the areas that will be seeded to annual forages have been hit by drought or heavy rainfall. Depending on the fertility of the intended previous crop and environmental conditions leading to the use of an annual forage, residual nitrogen may or may not be present. Only soil testing will lead to the right fertilizer answer. In general, most grass annual forages will require from 50-80 lb N/acre less soil test nitrate-N to two feet in depth. Any residual fertilizer applied earlier in the spring should be easily revealed by a soil nitrate test, since conversion of nearly all ammonium nitrogen is certainly complete.

There might be some situations where residual N levels are high. Plants tend to accumulate N in the lower stems or stalks. If growing a forage crop on areas of high residual N, such as around pothole areas, raising the sickle to about 6 inches off the ground will greatly reduce the nitrate present in the hay. Also, some broadleaf weeds tend to accumulate nitrate, including pigweed, lambsquarter, russian thistle and wild sunflower. Good weed control will reduce nitrate poisoning risks.

If the forage is excessively green at the intended time of grazing or haying, a forage sample can be collected and sent to a lab for nitrate analysis. A local veterinarian can help direct you to a lab. If levels of nitrate are above 0.65% of plant tissue (dry weight), then some blending of feed sources may be needed to make use of the hay.

However, if reasonable soil testing and fertilizer application guidelines are followed, there should be little risk of nitrate poisoning. Complicating factors which will increase risk include poor growth, particularly due to continued drought or an early frost.

An excellent publication on nitrate poisoning is available from NDSU- circular V-839, C. Soltenow and G. Lardy. Also available on the web at

http://www.ext.nodak.edu/extpubs/ansci/livestoc/v839w.htm 

 

GROWING DEGREE DAYS- 1961-1990 AVERAGE COMPARED WITH 2002

Growing degree days are lower this year than the 30 year average for wheat by about 10% at this time. That coincides well with reports of the crop being about two weeks behind normal growth. Row crops vary from about 10% ahead of normal in the drought-stricken south central part of the state to normal at Minot and Crary to about 5% behind GDD’s in northern counties for row crops such as corn. Not stated in the chart is the problem with planting date. Many areas in the state were seeded much later than normal. The April 20th date for wheat is the emergence date, not seeding date, and likewise for the May 10th date for corn. Most row crops did not emerge until almost Memorial Day even if they were seeded early in May. That helps to explain many of the fields with 4-6 leaf corn, when the degree days from early in May show the corn should be much further along. So if we look realistically at the progress of the crop, factoring in the normal seeding and emergence dates of our row crops (usually late April to about May 10), with what really happened (seeding early May, emergence late May), the cool early temperatures combined with late emergence is really most of the problem.

 

Location

Wheat (32o)
April 20 - June 25

Corn (50o)
May 10 - June 25

30 year
Est. mean

2002

30 year
Est. mean

2002

Bowbells

1503

1113

512

359

Bowman

1563

1048

554

400

Carrington

1602

1140

532

419

Crary

1560

1095

540

387

Dickinson

1522

1143

522

398

Fargo

1727

1300

611

495

Grand Forks

1639

1199

575

451

Hettinger

1570

1153

535

427

Jamestown

1687

1195

593

444

Langdon

1496

1025

510

344

Mandan

1657

1205

571

449

Minot

1614

1133

540

398

Wishek

1521

1182

519

428

Williston

1681

1168

583

410

Dave Franzen
NDSU Extension Soil Specialist
(701) 231-8884
dfranzen@ndsuext.nodak.edu
 

 

SOYBEAN IRON CHLOROSIS

Yellow soybeans are nothing new to ND/NW MN. Our problems are caused by high levels of soil carbonates, and are aggravated by other stress factors, including soil salinity. In addition, wet soils, compaction, cool soil temp., herbicides and in some cases poor variety choices all contribute to greater and more extended chlorosis.

With continuing warm weather, and some movement towards drier fields, chlorosis tolerant varieties will green up quickly. Those varieties less tolerant will green up more slowly. Intolerant varieties may not green up at all. The severity of the stresses affecting the soybean response to chlorosis will also affect the speed of recovery.

Dave Franzen
NDSU Extension Soil Specialist

(701) 231-8884
dfranzen@ndsuext.nodak.edu


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