Field Day - University of Wyoming R&E Center Adams Ranch. Saturday, June 15, Sheridan, WY

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2 o Why Irrigation Scheduling? o Irrigation Efficiency o Water Use Efficiency (WUE) o Strategies for Irrigation Scheduling o Irrigation UW o Alfalfa x Irrigation o Limiting Water and Yield

3 WHY IRRIGATION SCHEDULING? To make the better use of the irrigation water aiming at better profits while being responsible with our environment and our society. Irrigation scheduling also allows for better irrigation efficiency and enhanced water use efficiency Irrigation Efficiency Is a measure of the irrigation performance Refers to the uniformity of the applied water. It s the fraction of water used efficiently and beneficially. Is a measure of the effectiveness of the system to deliver water to crops Irrigation can be diverted from reservoirs and transported to the field through canals or pipelines Is a measure of the effectiveness of irrigation on increasing plant production The ratio on the increase in production to the volume of water applied by irrigation as compared to non-irrigated production

4 IRRIGATION EFFICIENCY Soil Type Canal Length (ft) Sand Loam Clay to Irrigation Method Es = 0.70 x 0.60 = 0.42 Application Efficiency Surface 60 Sprinkler 75 Not all water taken from a source reaches the root zone of the plants. Part of the water is lost during transport through the canals and in the fields. The remaining part is stored in the root zone and eventually used by the plants. Conveyance Efficiency (Ec) Water that reaches the farm / Water diverted Application Efficiency (Ea) Actual storage of water in the root zone / Water applied in the field Overall System Efficiency (Es) Es = Ec x Ea Drip 90 One acre of alfalfa needs inches of water/year 35 acre-in of water = 950K gallons of water 950K 2.3 Million gallons of water (978K/0.42) from the system

5 WATER USE EFFICIENCY - WUE Is the ratio of the economic yield to the amount of water used by the crop to produce that yield WUE is the Agronomic efficiency of water use

6 IRRIGATION SCHEDULING Evapotranspiration

7 Maximum ET IRRIGATION SCHEDULING importance of ETc Maximum yield Linear relation between ET and yield The more ET the more yield Soil moisture and weather conditions will allow reaching maximum ET The relation is genotype-specific

8 IRRIGATION SCHEDULING know your crop Crop Growth Stages How Alfalfa plant develops

9 IRRIGATION SCHEDULING know your crop A L F A L F A S F A C T S Relatively drought tolerant Deep rooted perennial crop Survives long periods between irrigations Taproots: > 20 ft Effective rooting depth: about 6 ft. Relatively high water use requirement Production of high-quality alfalfa if timely application of proper amounts of water Aside from cold weather, improper irrigation is the primary cause of low yields A L F A L F A S R O O T G R O W T H Depth of roots (ft) Water extracted (%) MSU, Bozeman If no restrictive layers exist

10 IRRIGATION SCHEDULING know your crop effective root Deep soil Soil with a hardpan layer Two months in 40% in 30% in 20% Two years 4.5 months in 10% The crop s available water is critically dependent on the depth of rooting often very difficult to estimate Two years Percentage of total water extracted from that layer

11 IRRIGATION SCHEDULING know your soil - available water S O M E D E F I N I T I O N S A W V S. S O I L T Y P E Saturation All pores are filled with water Field Capacity (FC, in/ft) Water content in the soil profile after wetted and drainage becoming small Permanent Wilting Point (PWP, in/ft) Water content in the soil profile at which plants die Available Water (AW, in/ft) AW = FC - PWP

12 IRRIGATION SCHEDULING know your soil - available water Management Allowable Depletion MAD - + Soil Available Water (AW) 25% Threshold 35% Threshold 50% Threshold 65% Threshold Wilting Point Field Capacity Lab Alfalfa Readily Available Water (RAW) Used by Plants Lab & Field

13 HOW MUCH WATER IN A SEASON? o o Not all water applied reaches the root zone of the plants. Part of the water is lost in the fields. The remaining part is stored in the root zone and eventually used by the plants. Application Efficiency (Ea) o Actual storage of water in the root zone / Water applied in the field Irrigation Method Application Efficiency Surface 60 Sprinkler 75 Drip 90 o o ETc of alfalfa = 35 inches/acre/year o 35 acre-in of water = 950K gallons Adding the Application Efficiency: o 35 acre-in (Surface) = 1.6 million gallons of water o 35 acre-in (Sprinkler) = 1.3 million gallons of water o 35 acre-in (Drip) = 1.0 million gallons of water

14 IRRIGATION SCHEDULING METHODS Soil Conditions Crop Conditions Weather Conditions and/or and/or Intuition Checkbook Soil moisture Plant conditions Most practical but less accurate Non practical, time consuming but accurate Accurate and practical after calibration Requires specialization, research too complex Growers have their customized irrigation scheduling

15 IRRIGATION SCHEDULING UW IN POWELL Water use, water use efficiency and irrigation scheduling of Alfalfa for forage

16 ALFALFA STUDY procedure Objectives: Determine the impact of irrigation strategies on alfalfa yield and quality Determine water use and water use efficiency (WUE) of alfalfa for conditions in Wyoming Treatments: Three varieties: Shaw, Mountaineer, and Lander Four irrigation strategies: full, 75%, 50%, and 25%

17 ALFALFA STUDY procedure Irrigation Water Balance using FAO56 for ET and Kc Sub-surface Drip Irrigation Tape 12 in Weather Soil Moisture First year: Watermarks + Transmitter + 6, 12, 36 in Hourly and daily data from the Data recorded: solar radiation, air temp, relative humidity, rainfall Year two: Neutron 6, 12, 36, 48, 60, 72 in

18 ALFALFA STUDY results Harvest (One Cut)

19 ALFALFA STUDY results

20 % TDN % ADF RFV % Protein ALFALFA STUDY results > 185: Supreme > 22: Supreme Irrigation Strategy Irrigation Strategy > 62: Supreme Irrigation Strategy < 27: Supreme Irrigation Strategy RFV - Relative Feed Value TDN - Total Digestible Nutrients ADF - Acid Detergent Fiber

21 1. Similar, or better, alfalfa yields can be produced with less water 2. Deficit irrigation decreases DM yield but enhances some quality characteristics as well as WP.

22 THANK YOU! Plant Sciences - UW