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INVESTIGATOR: Schmidt, J.; Rice, C. W.

PERFORMING INSTITUTION:
AGRONOMY
KANSAS STATE UNIV
MANHATTAN, KANSAS 66506

PREDICTING POTENTIAL MINERALIZABLE NITROGEN BY REMOTE SENSING

OBJECTIVES: 9501616. The project goals are to evaluate remote sensing of potential mineralizable N (PMN) and integrating PMN into fertilizer N recommendation models. The specific objectives are to: 1) characterize the spatial distribution of mineralizable N through remote sensing and direct field measurement of soil organic matter (SOM), and 2) guided by aerial photography, establish the minimum sampling intensity needed to calibrate the digitized aerial photography of SOM.

APPROACH: Aerial photography of bare soils will be used to identify distinct areas of color, representing a range in SOM content. Soil organic matter determined from soil samples collected in each area will generate a color vs. SOM relationship from a digitized photograph that will generate a spatially distributed SOM map. Variable and uniform N management on irrigated and dryland crops will be compared with and without the PMN estimates for N recommendations. Improvement in the accuracy of N recommendations in conjunction with variable N application will be determined from field-based measurements of apparent fertilizer N recovery. Potential reduction in groundwater contamination will be quantified through soil profile N measurements after harvest.

PROGRESS: 1995/09 TO 1998/09
Nitrogen Study: Despite nitrogen rates varying between 170 and 280 kg N per hectare across entire fields, there was not a detrimental decrease in yield or leaf N content as a consequence of low nitrogen in any areas of the field. Small-plot experiments, with nitrogen rates varying between 0 and 340 kg N per hectare, indicated that optimum yields were obtained with an N rate between 150 and 200 kg N per hectare. These rates are comparable to the current Kansas State University N recommendation, yet producers applied about 70 kg N ha-1 greater than the recommended rate. These results are based on two year's of small-plot work and four years of whole-field work on five center-pivot irrigated cornfields (about 50 hectares each) in south central and southwestern Kansas. There appears to be an opportunity to refine the current nitrogen recommendation at the field scale and probably even at a smaller scale. Funding partners on the project include USDA-NRI, KDHE (EPA), Kansas Corn Commission, and local agricultural industries. Two graduate students are working on this project.

IMPACT: 1995/09 TO 1998/09
Improving the ability to prediction N mineralization will provide an opportunity to refine N recommendations for every location within an entire field. This will increase the potential to increase N use efficiency, thus decreasing the risks for loss to the groundwater. This risks is especially great in south central Kansas where soils are sandy, groundwater relatively shallow, and corn is irrigated.

PUBLICATIONS: 1995/09 TO 1998/09
No publications reported this period