End of Yield-Based Fertilizer Recommendations. Dave Franzen, PhD Professor Soil Science NDSU Extension Soil Specialist Fargo, ND

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1 End of Yield-Based Fertilizer Recommendations Dave Franzen, PhD Professor Soil Science NDSU Extension Soil Specialist Fargo, ND

2 Yield and N rate are independent between fields. First indicated from work with active-optical sensors at Oklahoma State University Implied in the Return to N economic production functions used by NDSU and other mid-west states beginning in 2005

3 Sawyer and Nafziger, Return to N model- Integrates yield response to N with economics of the application. Recommendations are not necessarily linked to a yield goal. Assumes the grower is going for as much yield as economically practical. Categories known to affect yield are treated separately.

4 Yield, lbs per acre 4500 Eastern ND Sunflower Yield, y = x x R² = Total Known Available N, lbs per acre

5 Why is the aggregated relationship of yield and available N so diffuse, when the relationships within sites are so highly related?

6 Yield Example-Combining all sites with actual yield at N rate looks like this Total known available N

7 Yield When it really looks like this- Total known available N

8 To get a better idea of what the data look like without showing all the curves is to Normalize the data- putting it all in the same scale For example- A sunflower site with high yield 4,000 lb/acre, divide all yields by 4,000, and we end up with values from 0 to 1 A sunflower site with high yield 1,800 lb/acre, divide all yields by 1,800, and we end up with values from 0 to 1 A sunflower site with high yield 2,500 lb/acre, divide all yields by 2,500, and we end up with values from 0 to 1

9 Normalized Yield Normalizing yields at all sites ends up looking like this Total known available N

10 Normalized Yield If N rate and Yield were related between sites, the graphs would look like this after they were normalized Total known available N

11 Normalized Yield Within Site Wheat Yield, bushels per acre Western ND Conventional Till wheat sites raw yields y = x x r² = Total Known Available N, pounds per acre Western ND Conventional Till wheat sites, normalized yields y = -2E-05x x r² = Total Known Available N, pounds per acre

12 Normalized Wheat Yields Within Sites Wheat Yield, bushels per acre Western ND No-Till wheat sites raw yields y = x x r² = Total Known Available N, pounds per acre Western ND No-Till wheat sites normalized yields y = -1E-05x x r² = Total Known Available N, pounds per acre

13 Corn Yield Normalized Within Site Corn Yield, bushels per acre Eastern ND high-clay, Conventional Till, corn sites raw yields y = x x r² = Total Known Available N, pounds per acre Eastern ND high-clay, Conventional Till, corn sites normalized yields y = -6E-06x x r² = Total Known Available N, pounds per acre

14 Normalized Corn Yield Within Site Corn Yield, bushels per acre Eastern ND no-till, corn sites raw yields y = x x r² = Total Known Available N, pounds per acre Eastern ND no-till, corn sites normalized yields y = -5E-05x x r² = Total Known Available N, pounds per acre

15 Sunflower Yield Normalized Within Site Sunflower Yield, pounds per acre y = x x r² = Total Known Available N, pounds per acre Western ND no-till, sunflower sites raw yields Western ND no-till, sunflower sites normalized yields y = -5E-06x x r² = Total Known Available N, pounds per acre

16 Normalized Yield Sunflower Yield, pounds per acre Eastern ND Conventional Till, sunflower sites raw yields y = x x R² = Total Known Available N, pounds per acre Eastern ND Conventional Till sunflower sites normalized yields y = -4E-06x x R² = Total Known Available N, pounds per acre

17 The increased r 2 of the relationship between yield and available N with normalizing yield within site is only possible if the cloud of data in the original aggregated yield/ available N regression was really a series of reasonably parallel quadratic curves that lay on top of each other depending on the productivity of the site. These data and those of others analyzing similar modern data indicate that use of yield-based N rate formulas should cease, and people should recognize that a profitable N rate in a lower yield environment is similar to the N rate in a higher yield environment.

18 Low yield environmentusually drier (sometimes excessive wetness) Lower N use efficiency and crop uptake Less N mineralization High yield environment- Moisture near ideal- not too wet or too dry Higher N use efficiency and crop uptake Greater N mineralization Net result is that rate to produce economic max yield is similar in both environments.

19 All new fertilizer recommendation values will not be based on a yield-based formula. The recommendations will be relative yield-based. Wherever possible, regional and soil differences that result in a different relationship between nutrient and yield will be incorporated into the recommendations.

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24 There is a new phone app for Android phones for the 3 N calculators. Go to app store and search for North Dakota Crop Nitrogen Calculator and follow the instructions. It s free to download. We also have an app for IPhones- Go to the Iphone app store and look up North Dakota Crop Nitrogen Calculator, then follow instructions.

25 Yield-Goal RIP