Enhancing Sorghum Yield and Profitability through Sensor Based N Management

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Enhancing Sorghum Yield and Profitability through
Sensor Based N Management

• Dave Mengel and Drew Tucker
• Department of Agronomy
• K-State

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Situation Risk

• Sorghum is the summer crop of choice where it is
  too dry to produce dryland corn.
• Yields vary widely from year to year due to
  weather, especially rainfall and temperature.
• Using county level yield records, farmers produce
  lt50 bu/a sorghum 30 of the time in central
  Kansas and 40 of the time in western Kansas

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Situation N Management

• N fertilizer costs are significant, 20-40/a or
  more, depending on rate and source. This
  represents 10 to 20 of gross revenues.
• Optimum N rates vary from year to year.
• Need varies due to changes in yield
• Carryover varies dramatically from field to field
• In-season N loss can be significant at times.
• People refuse to use the profile N soil test

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Long-term N Response Study Hutchinson KS

• Wheat-sorghum-soybean rotation. No-till
• Sorghum yields averaged 72 bu/acre 91-05
• Range 10-142
• lt50, 3 years
• 51-75, 5 years
• 76-100, 4 years
• gt100, 3 years

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Long-term N Response Study, Hutchinson KS

• Mean optimum N rate, 50 lbs N/acre
• Range 0-100
• 0, 4 years, 10 to 75 bu/a
• 25, 2 years, 47 to 63 bu/a
• 50, 3 years, 76 to 97 bu/a
• 75, 2 years, 94 to 107 bu/a
• 100, 4 years, 50 to 142 bu/a
• 125, 0 years

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The Big Question

• Can a N management strategy be developed to
• Reduce economic risk in bad years?
• Take advantage of the potential of good years?
• Fine-tune N needs in high yielding irrigated
  crops?
• Reduce environmental risk in sensitive
• environments?
• Enhance profitability in the long run?

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Our Approach

• Apply a base level of N to carry the crop through
  the first 40-50 days. 20 to 30 lbs/a
• Evaluate the crop at 35-45 days
• If yield potential is low, soil moisture is
  limited and outlook bleak. punt
• If moisture reserves and weather outlook are
  good., use sensor technology to estimate yield
  potential, and add appropriate N

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The Devils in the Detail

• How good is your weather crystal ball?
• How early can we accurately estimate yield
  potential in sorghum?
• How early can we pick up differences in N levels
  between normal and reference strips?
• How late can N be applied and still be utilized
  and/or get a response?

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More Details

• How do we need to apply late N?
• And not damage the crop
• And get the best response
• How much N must be put down early to maximize
  yield potential in good years?
• Can sensors be used to do this on the go?

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Procedures 2006

• Locations Manhattan, Belleville, Tribune,
  Hutch/Partridge
• No-till planted, surface plus profile N ST
• Normal practices for weeds, bugs, fert etc
• N treatments 0 to 150 lbs N pre, post/sd or
  both.
• Measure leaf, stover and grain N, yield and
  various sensor measurements using Greenseeker,
  Crop Circle and SPAD meter

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Belleville
Manhattan
Tribune
Hutch
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Relationship of Response Index and ? Yield in
Sorghum in 2006
?Grain Yield Bu/Ac
?Yld 101.05 RI -91.95 R2 .73
Response Index, NDVI reference/ NDVI unfertilized
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Effect of time and method of N application on
sorghum yield, 2006
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2007 Work

• Continuing work on sorghum, wheat and corn at
  multiple locations
• Plan on providing sensor based N rate calculators
  for wheat and sorghum this fall on our ST website
  (sorghum, developed by Drew and Bill Raun, is
  currently on the OSU/NUE site)
• Starting preliminary work on cotton and canola

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GS-3 NDVI .60, check plot
GS-3 NDVI .65, reference plot
GS-3 N Rec. 45 lbs/Ac
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Questions?
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