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![Page 1: Spatial variation of soil constraints and its implications for site-specific soil and nutrient management in CA. Yash Dang](https://reader034.fdocuments.net/reader034/viewer/2022051617/55a3e5a51a28ab37598b45c4/html5/thumbnails/1.jpg)
Spatial variation of soil constraints and its
implications for site-specific soil and nutrient
management in conservation agriculture
Yash Dang, Lindsay Bell and Ram Dalal
![Page 2: Spatial variation of soil constraints and its implications for site-specific soil and nutrient management in CA. Yash Dang](https://reader034.fdocuments.net/reader034/viewer/2022051617/55a3e5a51a28ab37598b45c4/html5/thumbnails/2.jpg)
Spatial and Temporal Variability
Mean 1.79
SD 0.39
CV 21.5%
Mean 0.91
SD 0.31
CV 34.5%
Mean 1.29
SD 0.40
CV 31.2%
Mean 18.9
SD 10.7
CV 56.6
Variation between seasons >
Variation within a season
PM should consider both spatial
and temporal aspects
![Page 3: Spatial variation of soil constraints and its implications for site-specific soil and nutrient management in CA. Yash Dang](https://reader034.fdocuments.net/reader034/viewer/2022051617/55a3e5a51a28ab37598b45c4/html5/thumbnails/3.jpg)
a. Grower’s Knowledge & Experience
Measuring Variability
Heavy black soil, brigalow softwood
High yielding
Open black soil, plain, no tree
Medium yielding
Light soil, box, scattered brigalow
Poor yielding
![Page 4: Spatial variation of soil constraints and its implications for site-specific soil and nutrient management in CA. Yash Dang](https://reader034.fdocuments.net/reader034/viewer/2022051617/55a3e5a51a28ab37598b45c4/html5/thumbnails/4.jpg)
b. Continuously (on the go yield monitoring)
Measuring Variability
![Page 5: Spatial variation of soil constraints and its implications for site-specific soil and nutrient management in CA. Yash Dang](https://reader034.fdocuments.net/reader034/viewer/2022051617/55a3e5a51a28ab37598b45c4/html5/thumbnails/5.jpg)
b. Continuously (proximal sensing)
Measuring Variability
ECa (mS/m)
0 50 100 150 200 250
Avera
ge w
heat yie
ld (
t/h
a)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Y=3.95 - 0.02 ECa_LL, r2=0.97
NS; ECa_UL
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c. Remotely (Satellite imagery, Landsat)
Measuring Variability
near-IR – red
near-IR + red
NDVI_2007
0.2 0.4 0.6
Wh
ea
t g
rain
yie
ld_
20
07
(t/
ha
)
0
1
2
3
4
5Y = 6.48 - 0.35 NDVI, r2=0.79
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d. Discretely (point sampling of soil)
Measuring Variability
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Potential management classes
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Ground-truthing
Cl (mg/kg)
0 500 1000
So
il d
ep
th (
m)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Low
Medium
High
EMgP (%)
30 60
NO3-N (mg/kg)
0 20 40
VMCLL
(cm3/cm3)
0.2 0.3 0.4
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Site-specific soil management:
Amelioration
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Gypsum responses
Cumulative gross margin for surface applied gypsum $143/ha over 3-4 years
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Wheat 2005 Chickpea 2007 Wheat 2008
Gra
in y
ield
(t/
ha
)Gypsum 0
Gypsum 2.5 t/ha (2005)
a a
a
a
b
b
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Gypsum reduces Cl concentration
0
20
40
60
80
100
120
140
160
0 500 1000 1500
Cl (mg/kg)
So
il d
ep
th (
cm
)
Control
Gypsum spread
115 t
NaCl
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98
7
4
56
3
2
1
16
15
13
14
121110
0 2 5 0 5 0 0 7 5 0 1 ,0 0 01 2 5M e te rs
Low
Medium
High
N46N23N0
N46N0N23
N0N23N46
Applied nitrogen (kg N/ha)
0 10 20 30 40 50
Wheat
gra
in y
ield
(t/
ha)
1
2
3
4
5High
Medium
Low
Site-specific nutrients management:
Matching inputs
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Matching Inputs to Realistic Yield Potential
• Determine realistic yield potential
in presence of soil constraints
Realistic Yield Potential = Ymax
Soil constraints Soil Nutrition
Ymax = (Starting Soil Water + In Crop Rain) * Water Use Efficiency
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Nitrogen Requirement
N required (kg/ha) = (RYP x protein goal x 1.75 x 2)- Av. NO3-N to 0.9 m
NO3-N (mg/kg)
0 20 40
Soil
de
pth
(m
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Low
Medium
High
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Matching Nitrogen Fertilizer: EconomicsZone 1
(20 ha)
Low
Zone 2
(28 ha)
Medium
Zone 3
(16 ha)
High
Field average
(64 ha)
Realistic yield potential
(t/ha)
Nitrogen requirement
(kg N/ha)
Average available N in
the soil (kg N/ha)
Farmer’s rate (kg N/ha)
Actual N required (kg
N/ha)
Consequence of uniform
N application
3.36
150
3.9 t urea
required
114
46
36
1.29
59
2.0 t urea
waste
0
46
119
2.22
100
0.06 t urea
wasted
45
46
55
2.21
101
2.0 t urea
waste
31
46
70
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Matching Nitrogen Fertilizer: Environmental
Applied nitrogen (kg N/ha)
0 25 50
N-leachin
g (
kg/h
a)
0
5
10 High
Medium
Low
Applied nitrogen (kg N/ha)
0 25 50N
-de
nitrifica
tio
n (
kg/h
a)
0
7
14 High
Medium
Low
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In Summary
Integrate spatial data with grower’s
knowledge and ground-truthing to
identify spatial variability of constraints
to crop production
Evaluate sustainable development
goals (economic, environmental and
social) for site-specific soil and nutrient
management
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Thanks to number of colleagues who have
worked on the project over the years
And many more……
Thanks!