Land Formation & Water Management
Field Development Configuring the field shape, surface and slope Installation of water control structures To Optimize water management Crop production, uniformity Conserve resources Improve operation efficiency
Site Selection Adequate water supply Low infiltration rate.03 to 0.2 per day desirable.42 to 2.0 per season High clay content in topsoil or subsoil, 35 to 60% Hardpan in subsoil Naturally flat topography Calcareous or sodic subsoils
Natural contours Rice Production Workshops Chico and Colusa February, 2004
Laser leveling Improved Water Management Increased % Land Area in Rice Rice Production Workshops Chico and Colusa February, 2004
Leveling Benefits Increases efficiency of operations 12 to 15% Increases yield 10% Improves uniformity of water depth Improves stand establishment, weed control Improves drainage
Soil Fertility Cuts and fills Depth of cut NRCS method In cut areas, when highly permeable subsoil conditions are encountered overexcavate and replace the top soil. In fill areas, the topsoil will be stripped, the fills partly made and the topsoil replaced NRCS #464
Levees Permanent type Advantages: Freedom from annual installation, road access, no borrow pits, rollovers Disadvantages: Perennial weeds, rodents Part of leveling plan Temporary type Advantages: More efficient field preparation, fewer weeds and rodents Disadvantages: Annual work, borrowpits
Grade Slope, expressed in percent or tenths of foot 0.1 /100 = 0.1% Typical rice field slope is 0.0 to 0.1% Water depth variation from 0 to 2.5 is acceptable
Levee Spacing Problem Field has uniform slope of 0.1 /100 ; depth goal is 2.5 variation. What levee spacing is required? Assume no cross slope. Convert tenths to inches: 0.1/100 x 12 = 1.2 /100 Determine levee spacing: (2.5 /(1.2 /100 ) = 208
Water depth problem Field has levees spaced 250 apart, slope of 0.1%. What is the fall (difference in water depth) between each levee? Assume no cross slope. Find the fall in 250 : 250 x 0.1 /100 =.25 Convert to inches:.25 /100 x 12 = 3
Water Management
Purposes of Water Management Water supply for the crop Establishing an optimum plant population Suppressing weeds Providing for pesticide applications Conserving nutrients Protecting against cold weather Protecting water quality Managing salinity
Water management influences Blast RWW NO3 and N2 Weed recruitment Winter flooding, GHG
Seasonal Water Use Water use category Usage (af/ac) Evapotranspiration (Et) 3.1 3.7 Percolation/seepage 0.5 2.0 Drainage 0 2.0 Total 3.6 7.7 Lourence & Pruitt, 1971
Rice Water Use Lourence & Pruitt, 1971 Month Ratio Rice ET to grass ET Rice ET (inches) May 1.02 6.8 June 1.02 8.0 July 1.04 8.3 August 1.05 7.3 September 1.04 5.7 Total 36.1
Flow Through System Advantages Low cost Can flush salts Easy to install and maintain Adapts to irregular slopes Disadvantages High management Lower basins get deep Slow response to adjustments
Recirculation System Advantages Managing residues Flexibility Less effect of cold water Water conservation Lower water expense Disadvantages Installation and maintenance costs high Land out of production More management
Static Water Irrigation System Advantages Good for holding water Water conservation Independent level control in each basin Easy management No pump required Disadvantages High cost to install and maintain Land out of production Harder to flush salts Not suited to rotation crops
Flow Rates Determine speed of initial flooding and reflooding Initial flood requires 28 gpm/ac Maintenance requires a minimum of 5 gpm/ac and 10 is better.
Flow Rate Example 500 Hours 450 400 350 300 250 200 Time to deliver 4 acre inches 100 acre field 200 acre field 150 100 50 0 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Flow rate, gpm
Water Depth vs Tillering
Salinity Management Rice sensitivity greatest during seedling and pollination stages New salinity threshold: >1.9dS/m
Blanking Protection Cold damages pollen Sensitive stage ~ 10 days after PI (PI varies with planting date) Lasts about 5 days for a head, 2 weeks for a field Water is some protection Raise water around 70 days after planting
Pre-harvest Water Management A compromise between crop and equipment Remove water 2-4 weeks before harvest Timing depends on Surface drainage Internal drainage Physiological activity of the rice Climate during the drain period Moisture content (%) 40 35 30 25 20 15 10 5 0 y = -0.3205x + 12992 R² = 0.9336 9/14 9/29 10/14 10/29 Date
When to drain? Grains have filled from the top to the bottom of the panicle Color has changed from green to golden Tip kernels have become hard Lower kernels will have soft dough but not milk
M205 yield drained at different times Yield 10400 10400 10200 10200 10000 10000 9800 9800 Yield 9600 9600 9400 9400 9200 9200 9000 9000 16 16 20 20 24 24 28 28 Drain Drain date date (DAH) (DAH)
Soil moisture by drain date 30 25 M205 (0-10cm) 20 15 10 5 0 16 DAH 24 DAH 20 DAH 28 DAH 9/21 9/23 9/25 9/27 9/29 10/1 10/3 10/5 10/7 10/9 10/11 10/13 10/15 10/17 10/19 10/21 Water content (%) Date
Water Quality Long Term Irrigated Lands Program All runoff, percolation regulated Pesticide management http://www.swrcb.ca.gov/rwqcb5/water_issues/irrigated_lands/long_term _program_development/recomnd_framewk_mar2011.pdf
Seepage Management Block exits of seep ditches leading to drains Pump severe seep back to field or fallow Inspect levees for crayfish or rodent burrows; control them Build levees in fall so they will compact Include sufficient moisture for compaction Avoid excessive straw in levees Compact levees with tracklayer
Long Term Irrigated Lands Program 4 traditional monitoring sites (circa 1985) 3 additional sites in 2009 All off farm water movement is regulated http://www.swrcb.ca.gov/rwqcb5/water_issues/irrigated_lands/long_term_ program_development/recomnd_framewk_mar2011.pdf
Rice Production Workshops Chico and Colusa February, 2004 University of California Cooperative Extension