Enhancing Sorghum Yield and Profitability through Sensor Based N Management

1. Enhancing Sorghum Yield and Profitability through Sensor Based N Management Dave Mengel and Drew Tucker Department of Agronomy K-State

2. 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 <50 bu/a sorghum 30% of the time in central Kansas and 40% of the time in western Kansas

3. 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

4. Long-term N Response Study Hutchinson KS • Wheat-sorghum-soybean rotation. No-till • Sorghum yields averaged 72 bu/acre ‘91-’05 • Range: 10-142 • <50, 3 years • 51-75, 5 years • 76-100, 4 years • >100, 3 years

5. 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

6. 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?

7. 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

8. 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?

9. 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?

10. 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

11. Belleville Manhattan Tribune Hutch

17. 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

18. Effect of time and method of N application on sorghum yield, 2006

19. 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

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

22. Questions?