Soil Moisture or ET-Based Smart Irrigation Scheduling: A Comparison for Sweet Corn with Sap Flow Measurements
Abstract
Introduction
Materials and Methods
Study Site
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Cultural Practices for the Sweet Corn Experiments
Experimental Design
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Field Measurements
Sap Flow Measurements
Stem and sensor properties | Corrections |
---|---|
Stem circumference | 6.9 cm |
Stem diameter | 2 cm |
Bark thickness | 0.004 cm |
Xylem radius | 1 cm |
Sapwood depth | 0.45 cm |
Thermal diffusivity | |
Sapwood fresh weight | 1 g |
Sapwood dry weight | 0.63 g |
Probe spacing | 0.5 cm |
First thermistor depth | 1.5 cm |
Wound diameter | 17 m |
Soil Moisture Measurements and Sensor Calibration
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Measured Parameters and Statistical Analysis
Results and Discussion
Soil Moisture Analysis in ET-Based Scheduling
Soil Moisture Analysis of Soil Moisture–Based Scheduling
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Comparison between Irrigation Regimes
Soil Moisture
Irrigation scheduling type | Irrigation treatments | Applied water (mm) | Average decadal soil moisture (fraction) | ||||
---|---|---|---|---|---|---|---|
59 DAP | 69 DAP | 79 DAP | 89 DAP | Overall | |||
ET (%ET) | 60 | 322 | 0.24a | 0.24a | 0.27a | 0.26a | 0.25a |
90 | 460 | 0.30bc | 0.31b | 0.33bc | 0.31b | 0.31b | |
120 | 614 | 0.36d | 0.37bc | 0.40d | 0.39c | 0.38c | |
Soil moisture (%SM) | 25 | 462 | 0.30c | 0.32b | 0.30b | 0.32b | 0.31b |
30 | 522 | 0.33bc | 0.35bc | 0.35c | 0.36c | 0.34c | |
35 | 568 | 0.36d | 0.39c | 0.39d | 0.39c | 0.38d |
Note: Statistical comparison between the two different scheduling types. Within the same columns, means with the same letter are insignificantly different at .
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Applied Water in the Various Treatments
Days after planting | ET-based (%ET) | SM-based (%SM) | ||||
---|---|---|---|---|---|---|
60 | 90 | 120 | 25 | 30 | 35 | |
0 | 30.0 | 30.0 | 30.0 | 30.0 | 30.0 | 30.0 |
10 | 52.2 | 44.2 | 41.5 | 12.7 | 111.2 | 114.1 |
20 | 41.1 | 37.1 | 35.8 | 21.4 | 70.6 | 72.1 |
30 | 10.6 | 31.4 | 61.1 | 96.8 | 76.0 | 102.9 |
40 | 43.8 | 49.0 | 46.1 | 38.1 | 56.1 | 53.0 |
50 | 66.7 | 118.1 | 142.8 | 57.0 | 103.7 | 110.9 |
60 | 63 | 108.3 | 126.4 | 127.7 | 83.1 | 133.7 |
70 | 70.0 | 97.7 | 133.4 | 131.6 | 178.4 | 141.1 |
80 | 97.7 | 136.8 | 185.8 | 87.0 | 92.2 | 116.2 |
91 | 91.1 | 117.5 | 168.3 | 115.1 | 168.2 | 176.9 |
Total | 566.4 | 770.2 | 971.1 | 717.5 | 969.5 | 1,051.0 |
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Irrigation Regime Impact on Crop Growth
Impact on Shoot Height
Statistical comparison | Irrigation scheduling type | Irrigation treatment | Shoot height (cm) | Cob length (cm) |
---|---|---|---|---|
Within each irrigation scheduling type | ET-based (% ET) | 60 | 151.67a | 17.20a |
90 | 195.20b | 20.97b | ||
120 | 203.17c | 21.37b | ||
Soil moisture–based (% SM) | 25 | 185.83a | 19.867a | |
30 | 208.60b | 21.783b | ||
35 | 213.00b | 21.417b | ||
Between the two different irrigation scheduling types | ET-based (% ET) | 60 | 151.67a | 17.20a |
90 | 195.20b | 20.97b | ||
120 | 203.17c | 21.37bc | ||
Soil moisture–based (% SM) | 25 | 185.83d | 19.87d | |
30 | 208.60ce | 21.78bce | ||
35 | 213.00e | 21.42bce |
Note: A statistical comparison within the same and between the irrigation scheduling types is shown. Values within the same columns with different letters are significantly different at ( from three replicates) based on LSD.
Cob Length
Biomass and Yield Response
Aboveground Biomass
Statistical comparison | Irrigation scheduling type | Irrigation treatment | AG biomass () | Cob weight () | Root biomass () | Grain yield () | ||
---|---|---|---|---|---|---|---|---|
Fresh | Dry | Fresh | Dry | |||||
Within each irrigation scheduling type | ET-based (% ET) | 60 | 26.54a | 8.66a | 11.92a | 5.53a | 7.17a | 2.54a |
90 | 39.87b | 12.03b | 21.81b | 6.53b | 13.00b | 4.95b | ||
120 | 48.75c | 14.17c | 26.42c | 7.41c | 15.39b | 6.41c | ||
Soil moisture–based (% SM) | 25 | 44.33a | 13.75a | 25.43a | 7.58a | 10.50a | 6.08a | |
30 | 50.41a | 13.44a | 23.42a | 7.62a | 11.27a | 6.20a | ||
35 | 56.29b | 16.14b | 33.70b | 9.12b | 13.89a | 6.47a | ||
Between the two different irrigation scheduling types | ET-based (%ET) | 60 | 26.54a | 8.66a | 11.92a | 5.53a | 7.17ac | 2.54a |
90 | 39.87b | 12.03b | 21.81b | 6.53b | 13.00bc | 4.95b | ||
120 | 48.75c | 14.17c | 26.42c | 7.41ce | 15.39b | 6.41c | ||
Soil moisture–based (%SM) | 25 | 44.33bc | 13.75c | 25.43d | 7.58cd | 10.50bc | 6.08c | |
30 | 50.41cd | 13.44bc | 23.42d | 7.62cd | 11.27abc | 6.20c | ||
35 | 56.29d | 16.14d | 33.70e | 9.12ce | 13.89bc | 6.47c |
Note: A statistical comparison within each and between the irrigation scheduling types is shown. Values within the same columns with different letters are significantly different at ( except for root biomass, where ). AG = above-ground.
Root Biomass
Cob Weight, Grain Yield, and Grain to Cob Ratio
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Harvest Index Response
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Water Productivity Response
Statistical comparison | Irrigation scheduling type | Irrigation treatment | Applied water (mm) | Cob WP () | Grain WP () | AGB () | ||
---|---|---|---|---|---|---|---|---|
Fresh | Dry | Fresh | Dry | |||||
Within each irrigation scheduling type | ET-based (%ET) | 60 | 566 | 2.80a | 0.83a | 0.6a | 6.24a | 2.03a |
90 | 770 | 3.77b | 1.14b | 0.86b | 6.9a | 2.08a | ||
120 | 971 | 3.62b | 1.02b | 0.88b | 6.7a | 1.94a | ||
Soil moisture–based (%SM) | 25 | 717 | 4.73a | 2.56a | 1.41a | 8.23a | 2.55a | |
30 | 969 | 4.28a | 2.05b | 1.15b | 7.14a | 2.05b | ||
35 | 1,050 | 3.22b | 1.85b | 1.04b | 6.93a | 1.85b | ||
Between the two different irrigation scheduling types | ET-based (%ET) | 60 | 566 | 2.80a | 0.83a | 0.6a | 6.24a | 2.03a |
90 | 770 | 3.77bc | 1.14a | 0.86b | 6.9ab | 2.08a | ||
120 | 971 | 3.62bc | 1.02a | 0.88b | 6.7a | 1.94a | ||
Soil moisture–based (%SM) | 25 | 717 | 4.73d | 2.56b | 1.41c | 8.23b | 2.55b | |
30 | 969 | 4.28cd | 2.05c | 1.15d | 7.14ab | 2.05a | ||
35 | 1,050 | 3.22ab | 1.85c | 1.04bd | 6.93ab | 1.85a |
Note: Statistical comparison within the same and between irrigation scheduling types. Values within the same columns with different letters are significantly different at from three replicates () based on LSD. WP = water productivity (); and AGB = aboveground biomass.
Sap Flow
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DAP | T SM25% () | T SM30% () | T SM35% () | % SM25% | % SM30% | % in SM35% | () |
---|---|---|---|---|---|---|---|
84 | 4.24 | 4.11 | 6.45 | 74% | 72% | 112% | 5.74 |
85 | 4.75 | 4.97 | 6.09 | 83% | 87% | 106% | 5.73 |
86 | 4.79 | 5.03 | 6.11 | 82% | 86% | 105% | 5.82 |
87 | 5.07 | 6.13 | 6.43 | 86% | 104% | 109% | 5.9 |
88 | 5.29 | 6.81 | 6.02 | 82% | 106% | 94% | 6.43 |
89 | 4.58 | 5.26 | 6.04 | 74% | 84% | 97% | 6.23 |
90 | 5.13 | 5.8 | 5.8 | 88% | 99% | 99% | 5.86 |
Total | 33.85 | 38.11 | 42.94 | 81% | 91% | 103% | 41.71 |