Screening Deficit Irrigation Strategies Using Crop Growth Simulation

1
Screening Deficit Irrigation Strategies Using
Crop Growth Simulation R. Louis Baumhardt and
Scott A. Staggenborg USDA-ARS Conservation and
Production Res. Lab. Bushland, TX Kansas State
University Plant Science Center, Manhattan, KS
2

• Well capacity has declined with the decreasing
  water table.
• The choice is between deficit irrigation or
  concentrating water to adequately irrigate a
  portion.

3
Irrigation-strategy Question

• Will uniformly spreading water resources to
  deficit irrigate a large area produce more or
  less crop yield than if that same water resource
  was concentrated to irrigate a smaller area and
  averaged with the complementary dryland area?

Uniformly Irrigate
Variably Irrigate
4
APPROACH

• Use crop growth simulators (SORKAM and GOSSYM)
  and recorded weather at Bushland from 1958-1999
  to calculate sorghum grain and cotton lint yields
  for several deficit irrigation combinations.
• Determine crop growth and yield response to
  deficit irrigation levels for various planting
  practices or cultivar maturity.

5
IRRIGATION PARAMETERS

• Irrigation 7 d application interval and 4
  capacity levels
• No Irrigation Rain only
• Irrigation Rain 2.5 mm d-1 (2 gpm/ac)
• Irrigation Rain 3.75 mm d-1 (3 gpm/ac)
• Irrigation Rain 5.0 mm d-1 (4 gpm/ac)

6
OTHER FACTORS

• Sorghum
• Cultivar Maturity Early (15-leaf), Medium
  (17-leaf), Late (19-leaf)
• Planting Date 15 May, 5 June,
  25 June
• Cotton
• Irrigation Duration 4 and 8 weeks

7
(No Transcript)
8
MODEL VALIDATION
9
Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination Mean Simulated Sorghum Yield for a Common Cultivar, Planting Date, and Irrigation Combination
Type Irrigation Cultivar Maturity Planting Date Planting Date Simulated Yield Simulated Yield Weighted Average Yield Weighted Average Yield Base Yield
mm d-1 _____ kg ha-1 _____ _____ kg ha-1 _____ _____ kg ha-1 _____ _____ kg ha-1 _____
UNIFORM 2.5 Medium Medium 5 June 5 June 5130 5130 5130 100
21 3.75 Medium Medium 5 June 5 June 7150 7150 6070 118
Dryland Medium Medium 5 June 5 June 3920 3920
11 5.0 Medium Medium 5 June 5 June 7720 7720 5820 113
Dryland Medium Medium 5 June 5 June 3920 3920
10
Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations Mean Simulated Sorghum Yield for Unique Optimum Cultivar, Planting Date, and Irrigation Combinations
Type Irrigation Cultivar Maturity Planting Date Planting Date Simulated Yield Simulated Yield Weighted Average Yield Weighted Average Yield Base Yield
mm d-1 _____ kg ha-1 _____ _____ kg ha-1 _____ _____ kg ha-1 _____ _____ kg ha-1 _____
UNIFORM 2.5 Early Early 5 June 5 June 5180 5180 5180 101
21 3.75 Late Late 5 June 5 June 7280 7280 6280 122
Dryland Early Early 5 June 5 June 4280 4280
11 5.0 Late Late 15 May 15 May 8160 8160 6220 121
Dryland Early Early 5 June 5 June 4280 4280
11 Dryland 5.0 mmd-1
21 3.75 mmd-1 Dryland
UNIFORM 2.5 mmd-1
11
SUMMARY

• Simulated grain yield increased with increasing
  irrigation, but simulations also reflect
  generally better WUE at 3.75 mm d-1 than at 5.0
  mm d-1 irrigation levels.
• The weighted average grain yield for variable
  irrigation strategies with a dryland component
  increased net grain yield from 13 to gt20 over
  uniformly irrigated sorghum.

12
CONCLUSION

• For declining water resources, converting uniform
  deficit irrigation (water spreading) of a
  determinate crop like grain sorghum to variable
  irrigation that concentrates water on smaller
  areas with a complementary dryland area will
  increase overall sorghum grain yield.

13
(No Transcript)
14
SIMULATED COTTON YIELD vs IRRIGATION STRATEGIES


15
CONCLUSION

• Cotton yield levels are maintained or increased
  by converting from uniform deficit irrigation
  (water spreading) to variable irrigation on part
  of a field (concentrating water) with a
  complementary dryland area.

16
Wheat-Sorghum-Fallow Rotation

• Two crops in three years,
• Storage of precipitation as soil water,
• Stable grain crop yields

17
35? 11 N, 102? 5 WElevation 1170 mGrowing
season 181 d