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Crop Rotation and Tillage Effects on Water
Use and Yield
of Alternative Crop Rotations
for the Central Great Plains
D.C. Nielsen, M.F. Vigil, J.G. Benjamin
PROBLEM: Increased use of conservation tillage practices
has made more soil moisture available for crop production in the central Great
Plains, thereby providing greater opportunities for more intensive crop
production as compared with conventional wheat-fallow. Information is needed
regarding water use patterns, rooting depth, water use/yield relationships,
precipitation storage and use efficiencies, and water stress effects of crops
grown in proposed alternative rotations for the central Great Plains.
APPROACH: Nine rotations [W-F(CT), W-F(NT), W-C-F(NT),
W-M-F(NT), W-C-M(NT), W-C-PEA(NT), W-SUN-F(NT), W-M-SUN-F(RT), W-SUN-M-PEA(RT)]
are used for intensive measurements of water use and water stress effects on
yield. (W:winter wheat, C:corn, F:fallow, M:proso millet, SUN:sunflower, PEA:pea;
CT:conventional till, RT:reduced till). Measurements include soil water content,
plant height, leaf area index, above ground biomass, grain yield, residue mass
and cover, and precipitation.
RESULTS:
|
Rotation |
Crop |
ET (in) |
Yield (lb/a) |
Rotation |
Crop |
ET (in) |
Yield (lb/a) |
|
W-F(CT) |
wheat |
10.6 |
1453 |
W-SUN-F |
sunflower |
7.8 |
0 |
|
W-F(NT) |
wheat |
12.6 |
1842 |
W-M-SUN-F |
sunflower |
6.6 |
0 |
|
W-C-F |
wheat |
12.8 |
1790 |
W-SUN-M-PEA |
sunflower |
8.0 |
0 |
|
W-M-F |
wheat |
12.0 |
1698 |
W-C-PEA |
corn |
7.1 |
0 |
|
W-SUN-F |
wheat |
10.7 |
1342 |
W-C-M |
corn |
6.0 |
0 |
|
W-C-M |
wheat |
7.0 |
740 |
W-C-F |
corn |
6.4 |
0 |
|
W-C-PEA |
wheat |
6.3 |
311 |
W-M-F |
millet |
3.1 |
0 |
|
W-M-SUN-F |
wheat |
10.0 |
1235 |
W-M-SUN-F |
millet |
4.5 |
0 |
|
W-SUN-M-PEA |
wheat |
6.0 |
317 |
W-C-M |
millet |
4.2 |
0 |
|
W-SUN-M-PEA |
pea |
4.1 |
27 |
W-SUN-M-PEA |
millet |
4.0 |
0 |
|
W-C-PEA |
pea |
4.5 |
28 |
|
|
|
|
INTERPRETATION: Growing season precipitation was much below normal
(wheat=5.2", pea=2.9", sunflower=5.9", corn=5.4", millet=3.8"). Consequently, no
yield was produced by sunflower, corn, and millet. Pea and wheat yields were
low. Wheat yields were correctly predicted by soil water availability using a
previously defined relationship for extremely dry years (bu/a = 13.35 +
1.5*avail. water), but only for available water amounts greater than 6.5 inches.
Actual yields for drier starting soil water situations (W-C-M, W-C-Pea,
W-Sun-M-Pea) were far below predicted yields due to the extreme drought
(pan evaporation - precipitation for April, May, and June = 38.4").
FUTURE PLANS: Experiment to continue as in past years with no
significant changes. Modeling of yield and water use from this experiment was
begun in 2002 with RZWQM and DSSAT-CERES-Wheat, and will continue in 2003.
Evaluations of corn, sunflower, and millet models will also be started. Effects
of starting water content at planting on yield of corn and sunflower will be
published. The authors may be reached via e-mail at:
D.C. Nielsen,
M.F. Vigil,
J.G. Benjamin
or phone: 970-345-2259. |