Use of Alternative Concepts for

Determining Preplant and Mid-Season N rates

Use of Alternative Concepts for

Determining Preplant and Mid-Season N rates

Hodgen and Schepers 2007Hodgen and Schepers 2007

• Late emerging corn plants were non-responsive to different N fertilizer management strategies employed in this study.

• Managing N inputs per plant can increase NUE by 23% over broadcast applications of 168 kg N/ha applied either preplant or midseason (V9) and maintain yield and grain production per plant.

Hodgen and Schepers, 2007Hodgen and Schepers, 2007

• Opportunities may exist to increase N use efficiency by capitalizing on detecting the variability of N demand per plant as indicated by differences in grain production within commercial fields.

• Ultrafine spatial N management schemes that are aimed at increasing NUE should operate at a resolution which reflects the horizontal diameter at which plants obtain the majority of their N supply.

Hodgen and Schepers, 2007Hodgen and Schepers, 2007

• Similar N management techniques that attempt to capitalize on detecting differences in biomass (leaf area) production midseason could be used to estimate the relative yield differences between plants because of corn plants’ characteristic ability to maintain a harvest index of 50 to 55%

Hodgen and Schepers, 2007Hodgen and Schepers, 2007• The results of this study indicate that producers need to

be aware of agronomic management practices that lead to uneven emergence can result in lower yield potential as 5% of yield was lost by just one day of delayed emergence.

• Results from this study indicate the early emerging corn plants produce more kernels per plant and are thus higher yielding and more competitive than late emerging plants.

• The economic impact from even small differences, such as four days, in uniformity of emergence between corn plants can contribute to lower yields of late emerging plants. The loss in yield would then lower the potential return to investment of not only seed expenditures but potential response to applied N fertilizer.

Corn grain yield as a function of delayed emergence, NE

y = -1154x + 18080

R2 = 0.9436

2000400060008000

100001200014000

4 5 6 7 8 9 10 11 12 13 14

Delayed emergence

co

rn y

ield

, kg

/ha

Corn Grain yield as a function of Delayed emergence, OK

y = -121.66x + 9826

R2 = 0.9653

8000

8400

8800

9200

9600

10000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Delayed emergence

Yie

ld, k

g/h

a

Hodgen, PhD Dissertation

Real-Time Use of Mesonet Weather Data for Refined

GreenSeeker Sensor Based N

Recommendations in Winter Wheat

Real-Time Use of Mesonet Weather Data for Refined

GreenSeeker Sensor Based N

Recommendations in Winter Wheat

On-Line N RecommendationsOn-Line N Recommendations

• 21 algorithms on-line, Sensor Based Nitrogen Rate Calculator (SBNRC) that are being used in Oklahoma, many Mid-Western States, Australia, India, Mexico, China, Argentina, and Canada. Algorithms now included on our OSU site encumber winter wheat, spring wheat, corn, canola, bermudagrass, sorghum, rice, and cotton (http://www.soiltesting.okstate.edu/SBNRC/SBNRC.php).

Figure 1. Digitized Mesonet maps of fractional water index for November 27, 2005 (left) and November 27, 2006 (right), at the 24 inch depth, Oklahoma (brown-dry, green-wet). Campbell Scientific, 229-L

Average Response to Applied NAverage Response to Applied N

y = 0.0295x + 4.2261

R2 = 0.1423

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

0 50 100 150 200 250

Pre plant N, kg/ha

Yie

ld,

Mg

/ha

Cubic                  

          Mg/ha kg/ha      

NDVI FP NDVI N Rich Sum GDD CoefA CoefB Pred. Yield   Fert Cost Grain Price NUE

0.5 0.71 750 4.893525 0.988125 8.02029659 8020.29659 0.5 4.5 0.372

                   

  CoefA CoefA = 6E-08x3 - 0.0002x2 + 0.1122x - 18.731        

  CoefB CoefB = -5E-08x3 + 0.0001x2 - 0.1183x + 31.78        

  YP0 = (CoefA * EXP (CoefB * NDVI))            

  x = cummulative GDD              

                   

                   

                   

40% NUE

Olga 12.6 kg grain/ kg N applied topdress 0.828 lb N/bu 27.05 lb loss for 1.0 lb N rate error

OFIT 29.5 kg grain/ kg N applied preplant

Varvel 24.2 kg grain/ kg N applied preplant OSU data UNL data

Yield Loss Yield Loss

due to YP0 due to YP0

Rate Reduction error error  

% Error YP0 YPN N Fert. Rec Due to Error bu/ac bu/ac N Fert. Expense Grain Revenue Gross Profit

0.0 127.9 230.1 119.3 0.0     59.6 1035.4 975.8

5.0 121.5 218.6 113.3 6.0 1.3 2.7 56.6 1023.4 966.7

10.0 115.1 207.1 107.3 11.9 2.7 5.4 53.7 1011.3 957.7

15.0 108.7 195.6 101.4 17.9 4.0 8.0 50.7 999.3 948.6

20.0 102.3 184.1 95.4 23.9 5.4 10.7 47.7 987.2 939.5

25.0 95.9 172.6 89.4 29.8 6.7 13.4 44.7 975.2 930.5

30.0 89.5 161.1 83.5 35.8 8.0 16.1 41.7 963.1 921.4

35.0 83.1 149.6 77.5 41.7 9.4 18.7 38.8 951.1 912.3

40.0 76.7 138.1 71.6 47.7 10.7 21.4 35.8 939.0 903.3

45.0 70.3 126.6 65.6 53.7 12.1 24.1 32.8 927.0 894.2

50.0 63.9 115.0 59.6 59.6 13.4 26.8 29.8 914.9 885.1