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Traditional practices of application of N fertilizer New precision nitrogen management

Traditional practices of application of N fertilizer New precision nitrogen management. N rate (lb/A) = 35 + [1.2 x EY (bu/A)] - [8 x avg. ppm NO 3 -N in soil * ] - [0.14 x EY (bu/A) x %OM] - other N credits (lb/A). EY = expected yield %OM = percent organic matter

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Traditional practices of application of N fertilizer New precision nitrogen management

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  1. Traditional practices of application of N fertilizer • New precision nitrogen management

  2. N rate (lb/A) = 35 + [1.2 x EY (bu/A)] - [8 x avg. ppm NO3-N in soil*] - [0.14 x EY (bu/A) x %OM] - other N credits (lb/A) EY = expected yield %OM = percent organic matter * in the top 2 ft of soil. Corn N Fertilization: Other credits: manure applications; legume crop, NO3 in irrigation water, etc.

  3. N Credits: Dry basis ---As is---

  4. N Credits: NO3 in irrigation water: N credit (lbs/A) = NO3-N (ppm) x 0.23* x water (inches) *an acre-inch of water contains 0.23 lbs on N for each ppm of NO3-N

  5. Timing: Sprinkler irrigated: Starter band N; plus Side-dress at V6-V8 and additional N via fertigation Furrow irrigated: Majority pre-plant apply N (heavy texture) Plus some side-dress (light texture) With manure application*, they typically apply in Fall/Spring plus side-dress N * Many farmers do not credit for manure, use it for disposal purposes

  6. Dryland Wheat N Fertilization: Above table is for yield of 50 bu/A. To adjust N rate for expected yields, add or subtract 25 lb N/Ac for each 10 bu/A difference. [Max N rate is 75lb N/A for dryland winter wheat]

  7. New precision Nitrogen management strategies • Management zones based N management • Evaluating 4 different techniques • Classifying fields into low, medium, and high productivity areas • Real-time remote sensing based N management

  8. I. Techniques of Identifying Management Zones & N Mgmt Technique I. Involves three data layers (SCMZ): Bare soil imagery Topography Farmer’s experience

  9. I. MZ Technique and N mgmt… Technique II. Involves six data layers (YBMZ): Bare soil imagery Topography Previous year’s yield map Soil O.M. Soil texture (sand/silt/clay%) Soil C.E.C.

  10. I. MZ Technique and N mgmt… Technique III. Involves only one data layers (ECMZ): Soil E.Ca.

  11. I. MZ Technique and N mgmt… Technique IV. Involves alternative soil sampling procedure to create management zones (SSMZ) Step #1. Acquire bare soil imagery Step #2. Differentiate spectral variations/ strata using spatial statistical techniques

  12. I. MZ Technique and N mgmt… Technique IV. Involves alternative soil sampling procedure to create management zones Step # 3 Take soil samples based on cluster sampling (2-4 cluster / strata)

  13. I. MZ Technique and N mgmt… Technique IV. Involves alternative soil sampling procedure to create management zones Soil reaction (pH) Soil O.M. Soil Sand % Soil Silt% Soil Clay% Soil NO3 Step #4. (a) Use spatial modeling to predict measured soil properties, and (b) based on predicted soil properties for the entire field, management zones are delineated.

  14. I. MZ Technique and N mgmt… Management Zones delineated for Site 1: Technique IV Aerial imagery + Smart sampling + Spatial modeling Technique I Soil color based Technique II Soil color + yield + other soil prop. Technique III Soil E.Ca.

  15. I. MZ Technique and N mgmt… Management Zones delineated for Site 2: Technique IV Aerial imagery + Smart sampling + Spatial modeling Technique I Soil color based Technique II Soil color + yield + other soil prop. Technique III Soil E.Ca.

  16. I. MZ Technique and N mgmt… Management Zones delineated for Site 3: Technique IV Aerial imagery + Smart sampling + Spatial modeling Technique II Soil color + yield + other soil prop. Technique I Soil color based Technique III Soil E.Ca.

  17. I. MZ Technique and N mgmt… Experimental Strips across management zones • Various Nitrogen Management • Strategies are being tested: • Traditional uniform N strategy • (ii) Grid soil sample based variable N mgmt. strategy • (iii) Constant yield goal based variable N mgmt. strategy • (iv) Variable yield goal based variable N mgmt. strategy

  18. II.Remote Sensing: Remote-sensing for in-season nitrogen management • High Clearance tractor • Mounted with GPS unit & 25 feet high radiometer • Measuring canopy reflectance on four spectral wavebands (R,G,B, and NIR) on one center pivot field.

  19. II.Remote Sensing: Spectral Wavebands • Blue (B) 450 to 520 nm • Green (G) 520 to 600 nm • Red (R) 630 to 690 nm • Near-Infrared (NIR) 760 to 900 nm

  20. Top View V.Remote Sensing… Data is collected throughout the growing season from two view points 1) Top View 2) Inclined 75o view Inclined 75o view When areas within the field measure an NRI  0.95, the farmer is advised to fertigate an appropriate amount of N as soon as possible NRI ~ Nitrogen Reflectance Index (Bausch and Duke 2001)

  21. Thank you

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