2009 Crop Management Diagnostic Clinics Response of Corn Water Use to Limited Water Bill Kranz, UNL Extension Irrigation Specialist

Transcription

1 2009 Crop Management Diagnostic Clinics Response of Corn Water Use to Limited Water Bill Kranz, UNL Extension Irrigation Specialist Use & Copyright The materials in this document were developed by and for use by University of Nebraska Lincoln Extension in the Institute of Agriculture and Natural Resources. The materials are copyrighted by the Board of Regents of the University of Nebraska Lincoln on behalf of the. All rights are reserved. Copies may be printed for individual personal use; however, these materials can not be republished in print, on another Web site or used commercially without prior written permission. To seek permission to print a publication for educational use, please us at dpittman1@unl.edu. Disclaimer Reference to commercial products or trade names in these publications is made with the understanding that no discrimination is intended and no endorsement by is implied. University of Nebraska-Lincoln Institute of Agriculture and Natural Resources Extension is a Division of the Institute of Agriculture and Natural Resources at the University of Nebraska Lincoln cooperating with the Counties and the United States Department of Agriculture. University of Nebraska Lincoln Extension educational programs abide with the nondiscrimination policies of the University of Nebraska Lincoln and the United States Department of Agriculture. H 2 O #54 alfalfa canvas cover 1

2 HPRCC ETr (in.) 7/13/ y = x R 2 = York County, NE 1: ETG ETr (in.) From: Irmak et al. (2005): Nebraska Agricultural Water Management Demonstration Network, NAWMDN 2

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5 Multiply Weekly ETgage reading change by: VC =.1 V1 =.20 V2 =.40 V3 =.60 R1 =.90 R2 = 1.0 R3 = 1.10 R4 = 1.10 R5 = 1.10 R6 = 1.10 Beginning Mature =.90 Fully Mature =.20 Multiply Weekly ETgage reading change by: V2 =.2 V4 =.18 V6 =.35 V8 =.51 V10 =.69 V12 =.88 V14 = 1.01 V16 = 1.10 R1 = 1.10 Blister = 1.10 Dough = 1.10 Beginning Dent = 1.10 Full Dent =.98 Black Layer =.60 5

6 Corn is at 12-leaf growth stage and the water level in the ETG (with a No. 54 canvas cover) sight tube decreased 1.30 inches during the 7-day period since the last irrigation. Determine the actual crop ET (ETc), net irrigation requirement (NIR), and the gross irrigation requirement (GIR) if irrigation is applied with a center pivot with an irrigation efficiency of 90 percent (IE = 0.90). Rainfall = 0. ETr = 1.30 inches (evaporation from the ETG) Kc = 0.88 (from Table I for the 12-leaf stage) ETc = ETr x Kc ETc = 1.30 inches x 0.88 = 1.1 inches NIR = ETc Rainfall NIR = 1.1 inches 0 = 1.1 inches GIR = (NIR) / (IE) GIR = 1.1 inches / 0.90 = 1.2 inches 6

7 Electrodes Sensor collar Stainless steel sleeve Hand-held meter air water soil plant root SMP is an direct indication of the energy status of the soil water It quantifies how much energy (work) the plant roots have to invest to withdraw water from the soil 7

8 Seasonal ET (cm) Relative Crop ET 7/13/2009 Effect of Soil Water on ET 120 Above 40% SW Depletion -- ET is Reduced Crop ET Rate Relative Depletion Soil Moisture Deficit Reduces ET 22 R 2 = Corn (G-I-I treatment) Soil Moisture Deficit(cm) 8

9 Leaf Water Potentia Crop Water Stress Index 7/13/2009 Crop Water Stress Index for Rainfed and Irrigated Stressed Unstressed Day of Year Leaf Water Potential for Stressed Corn Day of Year 9

10 Tc-Ta Soil matric potential (kpa) 7/13/2009 Response of Corn Leaf Temperature to Stress 6 4 Unstressed Plants Vapor Pressure Deficit % depletion Hastings Silt Loam (average of 37 sites from NAWMDN) Water holding capacity = 2.2 in/ft Plant available water = 1.1 in/ft 25% depletion Plant available water (in/ft) 10

11 Converting Soil Water Potential to Water Depletion 11

12 CANOPY EVAPORATION & PLANT TRANSPIRATION RATE 7/13/2009 CANOPY EVAPORATION AND PLANT TRANSPIRATION TRENDS DURING IRRIGATION CROP CANOPY EVAPORATION PLANT TRANSPIRATION STARTED FINISHED IRRIGATION EVENT TIME 12

13 RATE, inches/hour 7/13/2009 RUNOFF POTENTIAL WITH CENTER PIVOTS INFILTRATION RATE How fast soil takes water in 1.5 APPLICATION RATE How fast water is applied 1.0 SURFACE STORAGE Amount ponded RUNOFF POTENTIAL Water that can move in or leave the field 0.5 SURFACE SATURATES RUNOFF BEGINS TIME, hours 13

14 Problem Application pattern intercepted Water application rate increase Uniformity reduced regardless of nozzle type What to Do Avoid 2-7 feet above ground Plants and ears Decrease spacing to 7.5 feet or less 14