Proper staging of your crop is important when estimating crop water use. For example, 4 leaf corn will use much less water than tasseling corn. Crop coefficients (Kc) for nine Nebraska crops based on stage of growth along with descriptions and pictures can be downloaded from this site to help you stage your crop.

The weekly ETgage change value multiplied by your crop stage's crop coefficient (Kc) will give you your crop's estimated water use.

If you are using the watermark sensors, knowing the soil type of the field is also important. Please see the soils chart (PDF, 10KB) which includes suggested irrigation trigger points. For more information on this topic, please see the UNL Extension publication "Watermark Granular Matrix Sensor to Measure Soil Matric Potential for Irrigation Management" (PDF).

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Crop StageKc1.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.50
V2 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
V4 0.18 0.18 0.20 0.22 0.23 0.25 0.27 0.29 0.31 0.32 0.34 0.36 0.38 0.40 0.41 0.43 0.45
V6 0.35 0.35 0.39 0.42 0.46 0.49 0.53 0.56 0.60 0.63 0.67 0.70 0.74 0.77 0.81 0.84 0.88
V8 0.51 0.51 0.56 0.61 0.66 0.71 0.77 0.82 0.87 0.92 0.97 1.02 1.07 1.12 1.17 1.22 1.28
V10 0.69 0.69 0.76 0.83 0.90 0.97 1.04 1.10 1.17 1.24 1.31 1.38 1.45 1.52 1.59 1.66 1.73
V12 0.88 0.88 0.97 1.06 1.14 1.23 1.32 1.41 1.50 1.58 1.67 1.76 1.85 1.94 2.02 2.11 2.20
V14 1.01 1.01 1.11 1.21 1.31 1.41 1.52 1.62 1.72 1.82 1.92 2.02 2.12 2.22 2.32 2.42 2.53
V16-Beginning Dent
Silking, Blister, Dough, Begin Dent.
1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Full Dent 0.96 0.96 1.06 1.15 1.25 1.34 1.44 1.54 1.63 1.73 1.82 1.92 2.02 2.11 2.21 2.30 2.40
Black layer 0.60 0.60 0.66 0.72 0.78 0.84 0.90 0.96 1.02 1.08 1.14 1.20 1.26 1.32 1.38 1.44 1.50
Full Maturity 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25

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Crop StageKc1.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.50
VC
Cotyledon
0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
V1
1st Node
0.20 0.20 0.22 0.24 0.26 0.28 0.30 0.32 0.34 0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50
V2
2nd Node
0.40 0.40 0.44 0.48 0.52 0.56 0.60 0.64 0.68 0.72 0.76 0.80 0.84 0.88 0.92 0.96 1.00
V3
3rd Node
0.60 0.60 0.66 0.72 0.78 0.84 0.90 0.96 1.02 1.08 1.14 1.20 1.26 1.32 1.38 1.44 1.50
R1
Begin Bloom
0.90 0.90 0.99 1.08 1.17 1.26 1.35 1.44 1.53 1.62 1.71 1.80 1.89 1.98 2.07 2.16 2.25
R2
Full Bloom
1.00 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50
R3-R5
Begin Pod, Full Pod, Begin Seed, Full Seed
1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Begin Mature 0.90 0.90 0.99 1.08 1.17 1.26 1.35 1.44 1.53 1.62 1.71 1.80 1.89 1.98 2.07 2.16 2.25
Full Mature 0.20 0.20 0.22 0.24 0.26 0.28 0.30 0.32 0.34 0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50
Mature 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25

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Crop StageKc1.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.50
Emergence 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
Visible Growth 0.50 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25
Leaf Elongation 0.90 0.90 0.99 1.08 1.17 1.26 1.35 1.44 1.53 1.62 1.71 1.80 1.89 1.98 2.07 2.16 2.25
Jointing 1.03 1.03 1.13 1.24 1.34 1.44 1.55 1.65 1.75 1.85 1.96 2.06 2.16 2.27 2.37 2.47 2.58
Boot 1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Heading 1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Flowering 1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Grain Fill 1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Stiff Dough 1.00 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50
Ripening 0.50 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25
Mature 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25

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Crop StageKc1.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.50
Emergence 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
3 Leaves 0.15 0.15 0.17 0.18 0.20 0.21 0.23 0.24 0.26 0.27 0.29 0.30 0.32 0.33 0.35 0.36 0.38
5 Leaves 0.31 0.31 0.34 0.37 0.40 0.43 0.47 0.50 0.53 0.56 0.59 0.62 0.65 0.68 0.71 0.74 0.78
8 Leaves 0.56 0.56 0.62 0.67 0.73 0.78 0.84 0.90 0.95 1.01 1.06 1.12 1.18 1.23 1.29 1.34 1.40
Final Leaf 0.87 0.87 0.96 1.04 1.13 1.22 1.31 1.39 1.48 1.57 1.65 1.74 1.83 1.91 2.00 2.09 2.18
Boot 1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Half Bloom 1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Soft Dough 1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
Hard Dough 0.84 0.84 0.92 1.01 1.09 1.18 1.26 1.34 1.43 1.51 1.60 1.68 1.76 1.85 1.93 2.02 2.10
Mature 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
Crop StageKc1.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.50
Early Vegetative 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
Vegetative 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
Bud Formation 1.00 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50
Flower Initiation 1.10 1.10 1.21 1.32 1.43 1.54 1.65 1.76 1.87 1.98 2.09 2.20 2.31 2.42 2.53 2.64 2.75
50% Disk Formation 1.15 1.15 1.27 1.38 1.50 1.61 1.73 1.84 1.96 2.07 2.19 2.30 2.42 2.53 2.65 2.76 2.88
Early Seed 1.15 1.15 1.27 1.38 1.50 1.61 1.73 1.84 1.96 2.07 2.19 2.30 2.42 2.53 2.65 2.76 2.88
Late Seed 1.15 1.15 1.27 1.38 1.50 1.61 1.73 1.84 1.96 2.07 2.19 2.30 2.42 2.53 2.65 2.76 2.88
Mature 0.20 0.20 0.22 0.24 0.26 0.28 0.30 0.32 0.34 0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50

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Crop StageKc1.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.50
Emergence 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
Cover 10-30% 0.14 0.14 0.15 0.17 0.18 0.20 0.21 0.22 0.24 0.25 0.27 0.28 0.29 0.31 0.32 0.34 0.35
Cover 30-50% 0.21 0.21 0.23 0.25 0.27 0.29 0.32 0.34 0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50 0.53
Cover 50-70% 0.34 0.34 0.37 0.41 0.44 0.48 0.51 0.54 0.58 0.61 0.65 0.68 0.71 0.75 0.78 0.82 0.85
Cover 70-80% 0.48 0.48 0.53 0.58 0.62 0.67 0.72 0.77 0.82 0.86 0.91 0.96 1.01 1.06 1.10 1.15 1.20
Cover 80-90% 0.60 0.60 0.66 0.72 0.78 0.84 0.90 0.96 1.02 1.08 1.14 1.20 1.26 1.32 1.38 1.44 1.50
Cover 90-Full% 0.73 0.73 0.80 0.88 0.95 1.02 1.10 1.17 1.24 1.31 1.39 1.46 1.53 1.61 1.68 1.75 1.83
Full Cover 0.83 0.83 0.91 1.00 1.08 1.16 1.25 1.33 1.41 1.49 1.58 1.66 1.74 1.83 1.91 1.99 2.08
Max LAI 0.91 0.91 1.00 1.09 1.18 1.27 1.37 1.46 1.55 1.64 1.73 1.82 1.91 2.00 2.09 2.18 2.28
Root Stage 0.91 0.91 1.00 1.09 1.18 1.27 1.37 1.46 1.55 1.64 1.73 1.82 1.91 2.00 2.09 2.18 2.28
After Frost 0.90 0.90 0.99 1.08 1.17 1.26 1.35 1.44 1.53 1.62 1.71 1.80 1.89 1.98 2.07 2.16 2.25

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Crop StageKc1.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.50
Emergence 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
Early Vegetative 0.13 0.13 0.14 0.16 0.17 0.18 0.20 0.21 0.22 0.23 0.25 0.26 0.27 0.29 0.30 0.31 0.33
Vegetative 0.30 0.30 0.33 0.36 0.39 0.42 0.45 0.48 0.51 0.54 0.57 0.60 0.63 0.66 0.69 0.72 0.75
Blossom 0.53 0.53 0.58 0.64 0.69 0.74 0.80 0.85 0.90 0.95 1.01 1.06 1.11 1.17 1.22 1.27 1.33
Early Tuber 0.76 0.76 0.84 0.91 0.99 1.06 1.14 1.22 1.29 1.37 1.44 1.52 1.60 1.67 1.75 1.82 1.90
Tuberization 0.91 0.91 1.00 1.09 1.18 1.27 1.37 1.46 1.55 1.64 1.73 1.82 1.91 2.00 2.09 2.18 2.28
Tuber Bulk 0.85 0.85 0.94 1.02 1.11 1.19 1.28 1.36 1.45 1.53 1.62 1.70 1.79 1.87 1.96 2.04 2.13
Tuber Bulk 0.60 0.60 0.66 0.72 0.78 0.84 0.90 0.96 1.02 1.08 1.14 1.20 1.26 1.32 1.38 1.44 1.50
Pre-Senescence 0.30 0.30 0.33 0.36 0.39 0.42 0.45 0.48 0.51 0.54 0.57 0.60 0.63 0.66 0.69 0.72 0.75
Senescence 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25
Mature 0.10 0.10 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24 0.25

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Crop StageKc1.001.101.201.301.401.501.601.701.801.902.002.102.202.302.402.50
Emergence-10% 0.06 0.06 0.07 0.07 0.08 0.08 0.09 0.10 0.10 0.11 0.11 0.12 0.13 0.13 0.14 0.14 0.15
Cover 10-50% 0.06 0.06 0.07 0.07 0.08 0.08 0.09 0.10 0.10 0.11 0.11 0.12 0.13 0.13 0.14 0.14 0.15
Cover 50-80% 0.48 0.48 0.53 0.58 0.62 0.67 0.72 0.77 0.82 0.86 0.91 0.96 1.01 1.06 1.10 1.15 1.20
Cover 80%-Full 0.81 0.81 0.89 0.97 1.05 1.13 1.22 1.30 1.38 1.46 1.54 1.62 1.70 1.78 1.86 1.94 2.03
Full Cover 1.00 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50
Pod Elongation 1.00 1.00 1.10 1.20 1.30 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10 2.20 2.30 2.40 2.50
Pod Fill 0.83 0.83 0.91 1.00 1.08 1.16 1.25 1.33 1.41 1.49 1.58 1.66 1.74 1.83 1.91 1.99 2.08
Dry Down 0.59 0.59 0.65 0.71 0.77 0.83 0.89 0.94 1.00 1.06 1.12 1.18 1.24 1.30 1.36 1.42 1.48
Senescence 0.30 0.30 0.33 0.36 0.39 0.42 0.45 0.48 0.51 0.54 0.57 0.60 0.63 0.66 0.69 0.72 0.75
Maturity 0.09 0.09 0.10 0.11 0.12 0.13 0.14 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23

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