Sources of variability in nitrogen availability in Iowa cornfields

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Date
1995
Authors
Perdomo, Carlos
Major Professor
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Alfred M. Blackmer
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Altmetrics
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Agronomy

The Department of Agronomy seeks to teach the study of the farm-field, its crops, and its science and management. It originally consisted of three sub-departments to do this: Soils, Farm-Crops, and Agricultural Engineering (which became its own department in 1907). Today, the department teaches crop sciences and breeding, soil sciences, meteorology, agroecology, and biotechnology.

History
The Department of Agronomy was formed in 1902. From 1917 to 1935 it was known as the Department of Farm Crops and Soils.

Dates of Existence
1902–present

Historical Names

  • Department of Farm Crops and Soils (1917–1935)

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Abstract

Studies were conducted to learn more about the spatial structure of soil NO[subscript]3[superscript]- concentrations in cornfields in late spring and to identify some major causes of variability in these concentrations. This information is specifically needed to aid in design of efficient sampling strategies for the late-spring test for nitrogen (N) availability, which is a new management tool that enables site-specific evaluation and adjustment of fertilization practices. One study assessed the importance of windrows of plant residue left by combines as a source of variability in soil nitrate (NO[subscript]3[superscript]-) concentrations for the next crop. Observations made in several fields having distinct windrows showed that yields of corn were significantly affected, but the effects on soil NO[subscript]3[superscript]- concentrations were minor compared to other unidentified sources of variability. A second study evaluated rows of young corn plants as a potential source ofvariability. Results from several fields revealed cyclic patterns in soil NO[subscript]3[superscript]- concentrations along transects perpendicular to rows. A third study evaluated nonuniform distributions of fertilizers across the width of large applicators as a possible source of variability. Observations made in several fields revealed cyclic patterns in NO[subscript]3[superscript]- concentration that seemed to be caused by fertilizer applicators and other farming operations. Models were developed that enabled integration of the observed cyclic patterns into geostatistical models commonly used to describe spatial structure. Procedures were developed for partitioning variability caused by two or more superimposed cycles;Overall, the results show that cyclic patterns are an important component of the spatial structure of soil NO[subscript]3[superscript]- concentrations in cornfields. Consideration of these cyclic patterns should enable more complete characterization of the spatial structure of soil NO[subscript]3[superscript]- concentrations in fields and, therefore, enable design of more efficient sampling strategies to assess NO[subscript]3[superscript]- concentrations within these fields. In addition, the ability to detect previously unrecognized cyclic patterns in soil NO[subscript]3[superscript]- concentrations gives the ability to demonstrate the benefits of using practices that minimize formation of troublesome cyclic patterns in fields.

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Sun Jan 01 00:00:00 UTC 1995