NDSU Crop and Pest Report
Soils


ISSUE 8  June 20, 2002

 

GROWING DEGREE DAYS-1961-1990 AVERAGE COMPARED WITH 2002

Growing degree days are lower this year than the 30 year average. Although the temperatures during the rest of the season may make up some difference, there is some concern that longer season row crops may need a wider frost-free window in the fall if summer degree days are just normal. Corn GDD’s are from normal to 20% lower than the long-term mean, figuring that crop emergence was May 10. If the crop did not emerge until later, these GDD’s cannot be factored into its estimated maturity.

Location

Wheat (32o)
April 20 - June 17

Corn (50o)
May 10 - June 17

30 year
Est. mean

 

2002

30 year
Est. mean

 

2002

Bowbells

1265

1113

405

359

Bowman

1316

1048

444

400

Carrington

1352

1140

420

419

Crary

1311

1095

426

387

Dickinson

1278

1143

412

398

Fargo

1458

1300

483

495

Grand Forks

1381

1199

455

451

Hettinger

1324

1153

422

427

Jamestown

1421

1195

468

444

Langdon

1258

1025

404

344

Mandan

1399

1205

451

449

Minot

1362

1133

426

398

Wishek

1281

1182

410

428

Williston

1419

1168

461

410

 

PURPLE CORN, YELLOW WHEAT, YELLOW BEANS

The spring colors for this year appear to be purple and yellow. Many fashionable fields are showing these colors in corn and wheat fields around the state. Although many growers would rather their crops revert to a more natural green, the crops are exhibiting these tones in response to environmental forces around them.

Purple corn-

It is true that if corn has a phosphorus (P) deficiency it will turn purple. Leaves, stem, leaf sheaths, will all turn purple. However, purple corn does not necessarily have P deficiency. Any condition which limits root growth and hinders the assimilation and movement of sugars within the plant results in the accumulation of red anthocyanin pigments, which when combined with a background green color create the purple we see. Conditions which can cause purpling include-cold soils, insect feeding, dry soils, excessively wet soils, compaction, salt, DNA herbicide carryover and hybrid sensitivity.

On the phosphate side, low soil test P and also summer fallow, corn following sugarbeets, and some of us also suspect canola, can be major factors. A good portion of calls this spring have been from growers growing corn after summer fallow. I have also seen the condition following sugarbeets. "Fallow syndrome" has been well documented, and is caused by a reduction of root-helpful mycchoriza fungi which infect many crop roots symbiotically, acting as supplemental feeder roots for the plants in exchange for food from the plants. Fallow and certain crops, such as sugarbeets and canola, do not support mycchorizal infection and numbers appear to decrease during these periods. The following crop, if in particular need of mycchorizal infection as is the case in a cold spring similar to the one we are in, may suffer decreased P absorption.

The main cause this spring is cold soils. The main cultural cause is corn after summer fallow and corn after sugarbeets. If we continue to have adequate soil moisture and warmer temperatures, this purple condition will rapidly fade away. Cultivation would only be helpful if the field is compacted and contributing to restricted root growth. In the future, consider high rates of P (40-60 lb P2O5 fertilizer regardless of soil test applied in a 2 by 2 band at seeding.

Yellow wheat-

Areas of wheat/barley fields inundated with water, but now fully drained off look very yellow this week. If these areas do not recover by next week they should be considered N deficient. If prospects for yield appear fair to good, top-dress with about 50 lb N/acre as liquid (consider straight stream nozzles/Chaffer bars), or urea. A rain of at least 1/4 inch would be necessary to move the N into the root zone. If the wheat/barley is younger than 6 leaf stage, yield improvements are possible. If the wheat is further along, little yield benefit would be realized.

Yellow beans-

Conditions are good for chlorosis on soybeans, dry beans (usually only in excessively salty sites), and flax. However, a more general yellowing on soybeans/dry beans may be seen due to lack of N. If the leaves are generally yellow, usually yellow-green including the veins, the cause is probably N deficiency. Look at the roots. If the plants have trifoliate leaves and have no nodules, this is not a good sign. If these areas are in previously flooded parts of the field, then the beans may recover. If they are generally found across the field, this is not a good sign. Continue to check for nodules for another ten days. If improvements have not been seen, apply at least 50 lb N/acre, using dry N sources or straight-stream nozzles are recommended, preferably before a significant rain.

Dave Franzen
NDSU Extension Soil Specialist
dfranzen@ndsuext.nodak.edu


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