ISSUE 11   July 13, 2006

LATE SEASON N APPLICATION FOR IRRIGATED CROPS

One bright spot in North Dakota agriculture is the promise for good returns from irrigation. I have had several calls on later season N applications for dry beans and especially corn. For corn, N can be applied until a couple weeks after tassel. The greatest demand for N is between about 8-leaf and tassel, but N continues to be required until nearly black-layer. If the prospects for a good crop continue past the 100-degree whether expected this week and perhaps into next, and N rates were conservative earlier in the season, and leaf-analysis indicates that the crop may benefit from more N, applications of 10 to 30 lb N/acre per pivot rotation are reasonable until tassel. I would avoid application of N during the pollination period, but then applications can be made after tassel during grain fill for a couple weeks if necessary. Avoid excessive applications of N if plant nutrition is already adequate.

Dry beans, especially higher yielding cultivars, such as navies, can also benefit from later season applications. Modest applications from 10 to 20 lb N/acre per pivot rotation during flowering can be helpful in sandier soils with poor N supplying capacity and leaching potential. Following the published charts based on N rate = YG X 0.05 can help guide the total N needed for higher yield potential dry beans.

 

FERTILIZER TRENDS

Fertilizer trends for the past six years have been surprising to me. I expected urea to overtake anhydrous ammonia due to larger farms, pressure on labor, insurance issues and liability. However, even though the gap between the two competing N sources has narrowed by about 6 percentage points, anhydrous still is the leading N source in North Dakota. It is likely that although many growers would like to switch to urea or 28%, the added cost in an already high N cost environment has contributed to the continued dominance of ammonia in the market. The increase in sulfur tonnage is also notable, because it is not tied any more to increases in canola acres, but is likely the result of continued wet years in many areas of the state during 2004-2005, and the fear of possible S deficiency in most crops especially in sandy soils. Phosphate use held higher than 2000-2003 because of generally higher yields in many areas and the switch to more row crops in the east. Potash was also higher than in the past probably again due to farmers growing more acres of crops with a higher K requirement, such as corn.

Fertilizer (Tonnage)

2000

2001

2002

2003

2004

2005

NH3

326,002

357,565

295,980

284,329

308,779

322,140

Urea

366,916

431,188

415,549

452,742

522,474

500,574

28-0-0

39,535

27,694

31,613

40,638

60,016

70,250

34-0-0

3,218

2,344

2,211

2,504

1,749

890

Am Sul

43,233

49,300

46,400

35,090

44,987

50,546

MAP

220,517

230,600

252,000

270,600

319,716

335,560

DAP

158,545

151,046

123,803

116,731

112,797

95,360

10-34-0

24,118

19,640

24,559

25,312

43,820

39,800

0-0-60

50,120

46,900

49,000

49,381

69,856

61,000

El Sul

2,525

2,859

2,586

2,500

3,700

6,580

Total N

522,000

577,000

517,000

526,000

590,000

594,000

Total P2O5

209,000

211,000

210,000

215,000

243,000

243,000

Total K2O

33,000

31,000

33,000

31,000

38,000

37,000

Total S

12,600

14,000

13,400

10,900

12,800

19,800

NH3 %tot.

51.2110

50.8151

46.9446

44.3250

42.9150

44.4705

Urea %tot

32.3335

34.3754

36.9734

39.5934

40.7352

38.7649

 

Dr. Dave Franzen
NDSU Extension Soil Specialist
701-231-8884
david.franzen@ndsu.edu


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