N Fertilization in Colorado Raj Khosla Colorado State University May 19 th & 20 th Oklahoma State...

• Traditional practices of application of N fertilizer

• New precision nitrogen management

Corn N Fertilization:

N rate (lb/A)N rate (lb/A) = 35 + [1.2 x EY (bu/A)] = 35 + [1.2 x EY (bu/A)]

- [8 x avg. ppm NO- [8 x avg. ppm NO33-N in soil-N in soil**]]

- [0.14 x EY (bu/A) x %OM]- [0.14 x EY (bu/A) x %OM]

- other N credits (lb/A)- other N credits (lb/A)

EY = expected yield%OM = percent organic matter* in the top 2 ft of soil.

Other credits: manure applications; legume crop, NONO33 in irrigation water, etc.

Legume Crop lb N/Acre creditAlfalfa >60% stand (4-6 plants / sq ft.) 100-140 30-60% stand (3-4 plants / sq ft.) 70-100 0-30% stand (0-3 plants / sq ft.) 0-70Dry beans 25

Manure lb N/ton credit

Beef 10 5 (at 50%DM)Dairy 15 3 (at 20% DM)Poultry 25 20 (at 75% DM)

N Credits:

Dry basis ---As is---

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

Timing:Sprinkler irrigated:Sprinkler irrigated: Starter band N; plus Side-dress at V6-V8 Starter band N; plus Side-dress at V6-V8

and additional N via fertigationand additional N via fertigation

Furrow irrigated:Furrow irrigated: Majority pre-plant apply N (heavy texture) Majority pre-plant apply N (heavy texture)

Plus some side-dress (light texture)Plus some side-dress (light texture)

With manure application*, they typically apply in Fall/Spring With manure application*, they typically apply in Fall/Spring

plus side-dress Nplus side-dress N

* Many farmers do not credit for manure, use it for disposal purposes

NO3-N in soil (ppm) Soil Organic matter

0-1 ft 0-2 ft 0-1% 1.1-2.0% >2.0%---Fertilizer rate, lb N/A---

0-3 0-5 75 75 754-6 6-9 75 70 507-9 10-12 75 45 25

10-12 13-15 50 20 013-15 15-18 25 0 0>15 >18 0 0 0

Dryland Wheat N Fertilization:

Above table is for yield of 50 bu/A. To adjust N rate for expected yields, add or subtract25 lb N/Ac for each 10 bu/A difference. [Max N rate is 75lb N/A for dryland winter wheat]

New precision Nitrogen management strategies

Management zones based N managementEvaluating 4 different techniquesClassifying fields into low, medium, and high productivity areas

Real-time remote sensing based N management

I. I. Techniques of Identifying Techniques of Identifying Management ZonesManagement Zones & N Mgmt & N Mgmt

Bare soil imagery

Topography

Farmer’s experience

Technique I.Technique I. Involves three data layers (SCMZ):

Technique II.Technique II. Involves six data layers (YBMZ):

Bare soil imagery

Topography

Previous year’s yield mapPrevious year’s yield map

Soil O.M.

Soil texture (sand/silt/clay%)

Soil C.E.C.

I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…

Soil E.Ca.

Technique III.Technique III. Involves only one data layers (ECMZ):


Technique IV.Technique IV. Involves alternative soil sampling procedureto create management zones (SSMZ)

Step #1. Acquire bare soil imagery

Step #2. Differentiate spectral variations/strata using spatial statistical techniques


Step # 3 Take soil samples based on cluster sampling(2-4 cluster / strata)


Technique IV.Technique IV. Involves alternative soil sampling procedureto create management zones

Technique IV.Technique IV. Involves alternative soil sampling procedureto create management zones

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.

Soil reaction (pH)

Soil O.M.

Soil Sand %

Soil Silt%

Soil Clay%

Soil NO3


Management Zones delineated for Site 1:Management Zones delineated for Site 1:

Technique ISoil color based

Technique IISoil color + yield+ other soil prop.

Technique IIISoil E.Ca.

Technique IVAerial imagery +Smart sampling +Spatial modeling


Various Nitrogen ManagementStrategies are being tested:

(i) 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

Experimental Stripsacross management zones


II.II. Remote Sensing:Remote Sensing:

Remote-sensing for in-season nitrogen management

High Clearance tractorHigh Clearance tractor

Mounted with GPS unit & 25 feet high radiometerMounted with GPS unit & 25 feet high radiometer

Measuring canopy reflectance on four spectral wavebandsMeasuring canopy reflectance on four spectral wavebands

((R,R, G,G, B,B, and NIR) on one center pivot field. and NIR) on one center pivot field.

Blue (B) Blue (B) 450 to 520 nm450 to 520 nm Green (G) Green (G) 520 to 600 nm520 to 600 nm Red (R) Red (R) 630 to 690 nm630 to 690 nm Near-Infrared (NIR) Near-Infrared (NIR) 760 to 900 nm760 to 900 nm

II.II. Remote Sensing:Remote Sensing:

Spectral WavebandsSpectral Wavebands

V.V. Remote Sensing…Remote Sensing…

Data is collected throughout the growing season fromtwo view points1) Top View2) Inclined 75o view

Top ViewTop View

Inclined 75Inclined 75oo view view

When areas within the field measure an When areas within the field measure an NRI NRI 0.95 0.95, , the farmer is advised to fertigate an appropriate amountthe farmer is advised to fertigate an appropriate amountof N as soon as possibleof N as soon as possible

target

reference

(/)(/)NIRG NRINIRG

NRI ~ Nitrogen Reflectance Index (Bausch and Duke 2001)

Thank you

N Fertilization in Colorado Raj Khosla Colorado State University May 19 th & 20 th Oklahoma State...

Documents

Transcript of N Fertilization in Colorado Raj Khosla Colorado State University May 19 th & 20 th Oklahoma State...