Soil Moisture or ET-Based Smart Irrigation Scheduling: A Comparison for Sweet Corn with Sap Flow Measurements
Abstract
Introduction
Materials and Methods
Study Site
Cultural Practices for the Sweet Corn Experiments
Experimental Design
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
Measured Parameters and Statistical Analysis
Results and Discussion
Soil Moisture Analysis in ET-Based Scheduling
Soil Moisture Analysis of Soil Moisture–Based Scheduling
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 .
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 |
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
Harvest Index Response
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
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 |