Tracy Blackmer Peter Kyveryga Advancing Agricultural Performance ® 1 Iowa Soybean Association On-Farm Network®

2. The high price of nitrogen fertilizer/grain combined with the complexity of N dynamics makes it desirable to improve N management Aerial Image

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4 Started as a variable rate project to identify areas needing more or less N. The results were such that improvements are needed at a whole field level before we target a subfield level.

5 Precision ag tools help collect an unprecedented amount of data.

6 Replicated strip trial example. N-50 refers to “normal” rate and 50 lbs N/a less.

7 Replicated strip trial example. Page 1 Aerial image

8 Replicated strip trial example. Page 2 Grain yield map

9 Replicated strip trial example. Page 3 Treatment position map

10 Replicated strip trial example. Page 4 Summary statistics

Fertilizer N Grain Yield lb N/acre bu/acre C-SB C-SB C-C C-SB C-C C-SB C-C C-C C-C Year Rotation Low Rate High Rate Low Rate High Rate Diff.

12 Yield increase from an additional 50 lbs N/a as affected by rainfall Rainfall has a big impact on N management. This should be factored into the evaluations.

13 Over 1,000 guided stalk sample fields. Over 150 N replicated strip trials.

14 Stalk samples collected from 6-14 inches above ground after physiological maturity.

15 Stalk samples collected from 6-14 inches above ground after physiological maturity.

16 Data collected  Aerial Imagery  Grain yield  Stalk nitrate

17 Calibration data is consistent with recommendations.

18 How do you represent this field?

19 Four stalk nitrate samples Three by soil map units One sample based on image “deficiency”

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22 The distribution of stalk nitrate samples across Iowa in 2007 Deficient Marginal Optimal Excess Applying adaptive management results in feedback data. One outcome is a “benchmark” The benchmark can: provide a status of management to the public track impact of programming Impact regulations

23 The benefit is multiplied by focusing on results in a group – not just an individual.

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25 Summary of stalk nitrate samples Management practice Sample percentage Differences between management practices are often observed at a group level.

26 The distribution of N forms is fairly well distributed.

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