Irrigation Management 101 Steve Melvin University of Nebraska - Extension
Why Irrigate Irrigation increases yields and profitability Managing precipitation variability Higher and more consistent yields allows for better planning of input levels (fertilizer, pesticides, labor, farm equipment, etc) and expenses to optimize returns. Managing the irrigated cropping system is key Crop residue on the soil surface will conserve water Pride and satisfaction of a good crop each year
Managing Precipitation Variability Every year is different Demand for food, fiber, and bioenergy crops is the same each year Irrigation helps stabilize the year to year difference in production Inches 25 20 15 10 5 0 Precipitation Variability Scottsbluff, NE (1893-2012) 25 20 Falls City, NE (1893-2012) Inches 15 10 5 0
Corn Yield Increases Rainfed vs Mechanized Irrigation 200 Bushels/Acre 150 100 Irrigated 50 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Year Source Missouri 2004 Irrigation Survey, University of Missouri Agricultural Extension Program Dryland
Corn Yield Response to Total Applied Water Data from Irmak and Rathje. 2008. Plant growth and yield as affected by wet soil conditions due to flooding or over-irrigation. University of Nebraska NebGuide G1904
Wheat Yield Response to Total Applied Water 8500 7500 Grain Yield (kg/ha) 6500 5500 4500 3500 2500 1500 100 200 300 400 500 600 700 Irrigation + precipitation (mm) Data from Zhang et al. 2000. Management of supplemental irrigation of winter wheat for maximum profit. Food and Agricultural Organization of the United Nations
YIELD FOR PIVOT-IRRIGATED CORN IN SOUTHWEST NEBRASKA 250 WELL WATERED YIELD = 220 bu/acre GRAIN YIELD, bushels/acre 200 150 100 50 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 DEPTH OF IRRIGATION APPLIED, inches
GRAIN YIELD PER UNIT OF WATER, bushels/acre-inch YIELD INCREASE PER INCH OF WATER 14 12 10 8 6 4 2 WITH PIVOTS INITIAL YIELD INCREASE = 13 bu/ac-in (most of water goes to ET) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 DEPTH OF IRRIGATION APPLIED, inches
Energy Balance at the Earth s Surface REFLECTED RADIATION EXTRATERRESTRIAL RADIATION ADVECTION wind SOLAR RADIATION LONG- WAVE RADIATION SOIL HEAT SOIL Source-University of Nebraska Lincoln-Extension
SOIL WATER BALANCE IRRIGATION RAIN TRANSPIRATION EVAPORATION ROOT DEPTH UPWARD FLOW STORED SOIL WATER GROUND WATER RUNOFF DEEP PERCOLATION Source-University of Nebraska Lincoln-Extension
Soil Water Terms Saturation Field Capacity More Available Less Available Permanent Wilting Point Source-University of Nebraska Lincoln-Extension Zero Water Content
SAT 6 5.8 6.1 5 5.2 100% 50% 0% FC MB PWP Water in soil (in/ft) 4 3 2 1 2.1 1.6 1.1 3.8 2.8 1.8 4.4 3.5 2.6 0 Sand Loam Silty Clay Loam
Saturation Field Capacity Minimum Balance Wilting Point Source-University of Nebraska Lincoln-Extension
Inches of Water per 60 Days 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 Hydraulic Conductivity Inches of water per 60 days Field Capacity 70% of Available Water This chart created with data from the Soil Water Characteristics, a computer program developed by Keith Saxton, USDA ARS 28 33 38 43 48 53 58 63 68 73 78 83 88 93 Centabar
Soil Water Movement 0.09-10+ in/day The soil water recharges from the top to the bottom. 0.09 in/day 1.0 in/year
Soil Water Movement A soil profile that is completely filled from rain or over irrigation can deep percolate a lot of water. 0.09-10+ in/day
Soil Water Movement 0.09-10+ in/day 1.0 in/year Typical in-season irrigated soil water levels with the top, 3 rd & 4 th foot wet and the second foot fairly dry. 0.09 in/day
Soil Water Movement Water needed to recharge soil if top four feet are at 40% of available water (dryland fields may easily hold twice this amount of water in the typical 6 ft root zone). Soil Type Sand 2.4 Loam 4.8 Silty Clay Loam 4.3 Water, In
PRECIPITATION CHANGES ABOUT 1 INCH FOR EVERY 25 MILES EAST-WEST From Nebraska Dept. of Natural Resources
1998 Yield Map Elsie Fully Watered Water Miser BMP Farmer Deficit
Evapotranspiration Deficit Impact on Corn Yield Graph from Crop Water Management, AGLW Water Management Group, FAO
Republican River Basin Irrigation Management Project 1996-2001 Summary Six Year Average of Corn Yields by Management Strategy and Site. Management Strategy Soil WHC 1 FARM Fully Water Deficit (in/ft) Watered Miser BMP Site Average Yields (bu/acre) Arapahoe 2.1" 188 189 198 190 Elsie 1.5" 196 196 185 162 Dickens 2 1.0" 202 201 187 175 Benkelman 1.8" 209 210 193 172 North Platte 3 2.0" - 203 202 188 McCook 2.0" 153 147 133 133 All Sites 4 191 193 185 171 Percent of FARM Yield 100 101 97 89 1 Soil Water Holding Capacity. 2 Data for Dickens not included in 97 due to irrigation error & soybeans in 2000. 3 FARM management strategy not used in North Platte. 4 Yield and applied water are weighted by the number of years of data at each site.
Republican River Basin Irrigation Management Project 1996-2001 Summary Six Year Average of Corn Water Use by Management Strategy and Site. Soil WHC 1 FARM Fully Water Deficit (in/ft) Watered Miser BMP Site Applied Water (acre-inches/acre) Arapahoe 2.1" 8.1 7.4 5.3 4.3 Elsie 1.5" 10.9 10.5 8.1 6.1 Dickens 2 1.0" 15.3 14.1 12.0 9.7 Benkelman 1.8" 12.8 12.5 9.7 6.2 North Platte 3 2.0" - 10.2 7.8 4.9 McCook 2.0" 16.0 9.7 8.0 5.8 All Sites 4 12 10.7 8.4 6.2 Percent of FARM Applied Water 100 87 69 50 1 Soil Water Holding Capacity. 2 Data for Dickens not included in 97 due to irrigation error & soybeans in 2000. 3 FARM management strategy not used in North Platte. 4 Yield and applied water are weighted by the number of years of data at each site.
Republican River Basin Irrigation Management Project 2003-2010 Summary 2003-2010 Average of Corn Yields and Water Use by Management Strategy and Site Management Strategy Fully Water Water Miser Def. Site Average Yields (bu/acre) Holbrook 199 195 Culbertson 142 158 127 Holdrege 239 244 233 Curtis 207 210 191 Arapahoe 192 185 171 Loomis 195 190 212 Bartley 182 179 183 All Sites 1 198 199 188 Percent of Fully Watered Yield 100 101 95 Site Applied Water (acre-inches/acre) Holbrook 10.0 8.2 Culbertson 9.2 8.8 6.6 Holdrege 6.0 4.7 2.7 Curtis 5.9 5.3 3.2 Arapahoe 8.9 8.1 6.9 Loomis 5.0 3.2 2.7 Bartley 6.5 4.4 3.8 All Sites 1 7.1 6.0 4.0 Percent of Fully Watered Applied Water 100 85 57 1 Yield and applied water are weighted by the number of years of data at each site.
Example 100 acres field to be planted to corn 490 ac-in of water to be used this year Fully Watered 400 ac-in/7.1 in = 56 acres 56 acres (Fully Watered) * 198 bu/a = 11,155 bu 44 acres (Dryland) * 90 bu/a = 3,960 bu Total 15,115 bu Deficit Irrigate 400 ac-in/4.0 in = 100 acres 100 acres * 188 bu/a = 18,800 bu Deficit irrigation produced 3,685 bu more corn
The four keys to making the Water Miser BMP work are: Invest in soil moisture monitoring equipment and use it Critically evaluate when to start irrigating Keep good rain and irrigation application records and compare them to what the ET has been for the field Starting at the dough stage, calculate the amount of rain and irrigation that is needed to get the crop to maturity
Normal water requirements for corn between various stages of growth and maturity in Nebraska Stage of growth Corn Approximate number of days to maturity Water use to maturity (inches) Blister (R2) a 45 10.5 Dough (R4) 34 7.5 Full dent (R5) 24 5.0 ¼ milk line 19 3.75 ½ milk line 13 2.25 ¾ milk line 7 1.0 Physiological maturity (R6) 0 0.0 NebGuide G1871 Predicting the Last Irrigation of the Season
Monitor the Pressure and / or Flow Rate One of cheapest ways to monitor your machine Know what the pressure should be If pressure is wrong, system can t be right. Flow meters, use them for management Source-University of Nebraska Lincoln-Extension
Example of Nozzling Problems with Pivots Good Uniformity Leak End-gun Adjust Nozzles Switched If sprinklers not properly installed / maintained high efficiency is not possible Rogers et al, 2009
Aerial Photos Tell Story of Nonuniform Water Distribution
Why Should I Want To Do Irrigation Scheduling? To know when to start for the season Water Miser Strategy saves 1-2 inches of water To know when to irrigate during the irrigation season Variation in rainfall, crop water use, and well capacity-may use more some years and save a lot on other years (-2 to 10 inches) To know how soon to begin delaying the start of the next irrigation to use up the stored soil water by crop maturity Save 2 to 5 inches
Irrigation Management 101 Steve Melvin University of Nebraska - Extension