Degree Type

Dissertation

Date of Award

1991

Degree Name

Doctor of Philosophy

Department

Agronomy

First Advisor

Richard M. Cruse

Abstract

Economic, and environmental reasons justify searching for alternative, sustainable production systems. Including small grain crops and legumes in the rotations improve diversification, and can reduce erosion, N fertilizer use, pests, and other biological problems. Strip cropping rotations of corn and beans have shown productive advantages per unit land compared with the rotation in open fields, if water availability is not limiting. A three year strip intercropping rotation, including corn, soybeans, and oats followed by hairy vetch or interseeded with nondormant alfalfa is being studied. The objectives of the reported research were to compare the effect of tillage systems and positions in the strips, on soil water content and crop yields. In 1989 and 1990, block experiments with each crop to evaluate strip position were conducted on Typic Argiudolls and Hapludolls using ridge till (site 1); on a Typic Argiaquoll (site 2), a split-plot four block experiment, with three tillage systems (conventional, reduced, and no till) as the main plots, and strip positions as the minor treatments was evaluated. Only crop yields were measured at site 1; at site 2 also measured were corn yield components, early corn and soybean growth, soil water content, and corn and soybean canopy temperatures. Precipitation during June, July, and August was 189 and 260 mm in 1989, and 584 and 444 mm in 1990, at sites 1 and 2, respectively. Positive border effect in corn was clearly present in 1990. Positive border effect was present both years in oats. Soybean yields were reduced in the borders in 1989, but soybean border yields were closer to the center yields in 1990. On a unit land basis, the strip intercropping rotation was more productive than the sole crops rotation in the wet year, and not different in the dry year. Site 2 results indicated that oat yields were not affected by tillage in 1989; reduced and no till were the best tillage systems for corn; for soybeans, no till > reduced > conventional yields were observed. In 1990, reduced and conventional till were the best tillage systems for corn, but soybean yields were not affected by tillage. Soil water contents, and corn and soybean canopy temperatures were related with the crop yield results.

DOI

https://doi.org/10.31274/rtd-180813-12599

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Fernando García-Préchac

Language

en

Proquest ID

AAI9202354

File Format

application/pdf

File Size

147 pages

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