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Effects of spatially variable plant available water on optimal corn seeding rate – field scale and site-specific approaches

by Haag, Lucas A.

Abstract (Summary)
Spatial variability in plant available water can be caused by uncontrollable factors

such as topography and soil texture as well as controllable factors such as residue

management.

Research located on the High Plains evaluated the impact of wheat (Triticum aestivum L.) stubble height on snow catch, plant available water at seeding, and optimal corn seeding rates. Treatments consisted of stripper harvest height of 71 cm (28 in.), cut

heights of 25 cm (10 in.), and 10 cm (4 in.) Measured snow depths were significantly

different among treatments (p<0.0001) with equivalent precipitation of 5.77 (2.27), 3.25

(1.28), and 1.73 cm (0.68 in.) for the stripped, 25 cm, and 10 cm heights respectively.

Available soil water at planting increased 24% as stubble height increased from 10 to 71

cm (4 to 28 in) in one year of the study. Two corn hybrids of varying maturity (97 and

108 days) were planted into the stubble treatments at seeding rates ranging from 2.47 to

5.43 plants m[superscript]-2 (10 to 22 000 plants ac[superscript]-1). In the dry year, the long season hybrid

responded positively to increasing population in tall stubble and negatively in short

stubble. Yield of the short season hybrid increased with increasing stubble height and

was mostly unresponsive to population. Grain yields of both hybrids responded

positively to increasing plant population in a wet year. Treatments also affected the yield

components of yield plant[superscript]-1, kernel weight, and kernels plant[superscript]-1.

Managing seeding rates for uncontrollable factors was attempted with small-plot

and field scale research across 3 fields in northeast Kansas. A relationship between soil

electro-conductivity (EC) and measured water holding capacity values was developed for

one study field. This quadratic relationship was significant (p<0.0001) and explained

variability in water holding capacity with respect to EC quite well (R[superscript]2=0.6239).

Responses from small plots showed that sites differing in population response

characteristics could be identified. Field scale data was used to derive a function

describing optimal seeding rate with respect to soil EC. In the field under study, optimal

seeding rates varied from 3.08 to 8.74 plants m[superscript]-2 (12 500 to 35 375 plants ac-1).

Bibliographical Information:

Advisor:

School:Kansas State University

School Location:USA - Kansas

Source Type:Master's Thesis

Keywords:variable rate seeding corn stubble height snow catch soil ec wheat agriculture agronomy 0285 engineering agricultural 0539

ISBN:

Date of Publication:01/01/2008

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