Land Formation & Water Management

Transcription

1 Land Formation & Water Management

2 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

3 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

4 Natural contours Rice Production Workshops Chico and Colusa February, 2004

5 Laser leveling Improved Water Management Increased % Land Area in Rice Rice Production Workshops Chico and Colusa February, 2004

6 Leveling Benefits Increases efficiency of operations 12 to 15% Increases yield 10% Improves uniformity of water depth Improves stand establishment, weed control Improves drainage

7 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

8 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

9 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

10 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

11 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

12 Water Management

13 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

14 Water management influences Blast RWW NO3 and N2 Weed recruitment Winter flooding, GHG

15 Seasonal Water Use Water use category Usage (af/ac) Evapotranspiration (Et) Percolation/seepage Drainage Total Lourence & Pruitt, 1971

16 Rice Water Use Lourence & Pruitt, 1971 Month Ratio Rice ET to grass ET Rice ET (inches) May June July August September Total 36.1

17 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

18 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

19 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

20 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.

21 Flow Rate Example 500 Hours Time to deliver 4 acre inches 100 acre field 200 acre field Flow rate, gpm

22 Water Depth vs Tillering

23 Salinity Management Rice sensitivity greatest during seedling and pollination stages New salinity threshold: >1.9dS/m

24 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

25 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 (%) y = x R² = /14 9/29 10/14 10/29 Date

26 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

27 M205 yield drained at different times Yield Yield Drain Drain date date (DAH) (DAH)

28 Soil moisture by drain date M205 (0-10cm) 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

29 Water Quality Long Term Irrigated Lands Program All runoff, percolation regulated Pesticide management _program_development/recomnd_framewk_mar2011.pdf

30 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

31 Long Term Irrigated Lands Program 4 traditional monitoring sites (circa 1985) 3 additional sites in 2009 All off farm water movement is regulated program_development/recomnd_framewk_mar2011.pdf

32 Rice Production Workshops Chico and Colusa February, 2004 University of California Cooperative Extension