Sorghum Fertility

Brian ArnallOklahoma State University

Dept Plant and Soil Sciences

Outline

• Nitrogen

• Phosphorous

• Potassium

• pH

• Micro’s

Soil Testing

• OSU, Ward, ect. $10 - $15– 20 lb N $9– 20 lb P $7.2– ¼ Ton Lime $5-10

» Per Acre!!!!!

• Some Co-Ops and Fertilizer Dealers, – Take and Process samples for FREE!!!!!!

Nitrogen

• Determined by Yield LevelN

lbs / ac bu / ac lb / ac2000 36 302500 45 403000 54 504000 71 704500 80 855000 89 1007000 125 1608000 143 1959000 161 230

Grain Yield

Strips and Sensors

• Independent of Yield

Phosphorous

Enter Values5.250.36100

STP Index Sufficiency P2O5 Needs Yield Loss w/o Plb /ac % lbs/ac bu/ac

0 40 60 6010 60 50 4020 80 40 2040 95 20 565 100 0 0

Yield Potential, bu/ac

Price of sorghum, $/buCost of P2O5, $/lb

0

50

100

150

200

250

300

350

0 10 20 40 65

Soil Test P

$/ac

re

Yield Loss Cost

Cost of P Fertilizer

0

20

40

60

80

100

120

140

160

180

200

0 10 20 40 65

Soil Test P

$/ac

re

Yield Loss CostCost of P FertilizerCost of P Fertilizer MedCost of P Fertilizer High

0

50

100

150

200

250

300

350

400

0 10 20 40 65

Soil Test P

$/ac

re

Yield Loss Cost LowYield Loss Cost MedYield Loss Cost HighCost of P Fertilizer

Enter Values5.250.3660Yield Potential, bu/ac

Price of sorghum, $/buCost of P2O5, $/lb

Enter Values5.250.6080

Price of sorghum, $/buCost of P2O5, $/lb

Yield Potential, bu/ac

Enter Values5.250.90120

Price of sorghum, $/buCost of P2O5, $/lb

Yield Potential, bu/ac

• Independent of Yield

Potassium

Enter Values5.251.10100

STK Index Sufficiency K2O needs Yield Loss w/o Klb /ac % lbs/ac bu/ac

0 40 100 6075 65 75 35

125 80 50 20200 95 30 5250 100 0 0

Yield Potential, bu/ac

Price of Sorghum, $/buCost of K2O, $/lb

Variability

Soil Test K variability among 24 1-acre cells in a field, 2001

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Cell

So

il T

es

t K

Area STK Point STK

Soil test P variability among 24 1-acre cells in a field, 2001

0

65

130

195

260

325

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Cell

So

il T

est-

P

Area STP Point STP

pH Issues

WheatpH Rel Yld Yield Econ $3.8 0 0 214.004.1 0.3 12 149.804.5 0.6 24 85.605 0.85 34 32.10

5.5 0.95 38 10.706 1 40 0.00

Average Yld 40 Grain $ 5.35

Sorghum pH Rel Yld Yield Econ $4.55

5.3 0.82 66 74.445.7 0.88 71 48.175.9 0.95 76 21.896.2 1 80 0.006.9 1 80 0.00

Average Yld 80 Grain $ 5.2

Mixed Reports, some state more Al tolerant and others show less.

Nutrient

Iron

Manganese

Copper

Zinc

Boron

Chlorine

Molybdenum

Soil (lb/a)*14,000 – 1,100,000

40 – 6,000

4 - 200

20 - 600

4 - 200

40 – 1,800

0.4 - 10

*Range of total in soils. From Chemical Equilibria in Soils. W.L.Lindsay, 1979. Wiley & Sons.

Crop (lb/a)**

1

0.8

0.08

0.6

0.08

4

0.0008

**Calculated for 2 ton crop yield (67 bushel wheat).

Micronutrients Needed by all Crops

Nutrients not found deficient in Oklahoma crops.

• Calcium.–Liming prevents Ca

deficiency.

• Manganese.

• Copper.

• Molybdenum.

Nutrients seldom found deficient in Oklahoma crops.

• Magnesium.

• Sulfur.

• Iron.

• Zinc.

• Boron.

• Chlorine.

MgYellowing between veins, old leaves Dolomitic Lime Sul-po-Mag, K-Mag

SulfurCan look like N, Yellowing between veinsGyp, S, Ammon Sulfate

IronYellowing between veins, new leavesFerrous Sulfate, ect

Micro Nutrients

• Zinc, Bronze between Margin and Midrib. Bleaching on either side of Midrib Zinc Sulfate, Zinc Chloride, Zinc Chelate

• Boron, Borax

• Chloride, Upper Leave Wilt,Muriate of Potashwhich K is usually also deficient

Soil Testing

Just Do It!Just Do It!

Thank You!

• Corn and Sorghum Nutrient Need Pete’s Sheets coming soon