• Traditional practices of application of N fertilizer
• New precision nitrogen management
Corn N Fertilization: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.) 0-70
Dry 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:N Credits:
Dry basis ---As is---
N Credits: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: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 75
4-6 6-9 75 70 50
7-9 10-12 75 45 25
10-12 13-15 50 20 0
13-15 15-18 25 0 0
>15 >18 0 0 0
Dryland Wheat N Fertilization: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 techniques
Classifying 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):
I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…
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
I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…
Step # 3 Take soil samples based on cluster sampling(2-4 cluster / strata)
I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…
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
I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…
Management Zones delineated for Site 1:Management Zones delineated for Site 1:
Technique ISoil color based
Technique IISoil color + yield+ other soil prop.
Technique III
Soil E.Ca.
Technique IVAerial imagery +Smart sampling +Spatial modeling
I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…
Management Zones delineated for Site 2:Management Zones delineated for Site 2:
Technique ISoil color based
Technique IISoil color + yield+ other soil prop.
Technique III
Soil E.Ca.
Technique IVAerial imagery +Smart sampling +Spatial modeling
I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…
Management Zones delineated for Site 3:Management Zones delineated for Site 3:
Technique ISoil color based
Technique IISoil color + yield+ other soil prop.
Technique III
Soil E.Ca.
I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…
Technique IVAerial imagery +Smart sampling +Spatial modeling
Various Nitrogen Management
Strategies 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
I.I. MZ Technique and N mgmt… MZ Technique and N mgmt…
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 points
1) Top View
2) 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
(/)
(/)
NIRGNRI
NIRG
NRI ~ Nitrogen Reflectance Index (Bausch and Duke 2001)
Thank you