HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Huang, X. Articles by Kravchenko, A. N. Search for Related Content PubMed Articles by Huang, X. Articles by Kravchenko, A. N. Agricola Articles by Huang, X. Articles by Kravchenko, A. N. Related Collections Site-Specific Analysis Spatial Distribution

SITE-SPECIFIC ANALYSIS & MANAGEMENT

Management Effects on Relationships of Crop Yields with Topography Represented by Wetness Index and Precipitation

^a Monsanto, 800 N. Lindbergh Blvd., St. Louis, MO 63167
^b Dep. of Statistics, 223 Statistics Building, University of Georgia, Athens, Georgia 30602-1952 ^aMonsanto, 800 N. Lindbergh Blvd., St. Louis, MO 63167
^c Dep. of Statistics and Probability, Michigan State Univ., East Lansing, MI 48824-1325
^d Dep. of Crop and Soil Sciences, Michigan State Univ., East Lansing, MI 48824-1325

^* Corresponding author (kravche1{at}msu.edu).

Crop yields are highly variable spatially and temporally as a result of complex interactions among topography, weather conditions, and management practices. The objective of this study was to analyze the effects of management practices on the relationship between crop yields and precipitation and crop yields and topography using 10 yr of yield data from a long-term corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.) rotation experiment in southwest Michigan. The four agronomic treatments studied were chisel plowed with conventional chemical inputs (CT), no-till with conventional chemical inputs (NT), chisel plowed with low chemical input and a winter leguminous cover crop (CTL), and organic-based chisel plowed with a winter leguminous cover crop (CTO). A nonparametric (spline) regression was used to characterize the relationship between the maximal yields, as characteristics of yield potential, and a wetness index (WI), as an integrative characteristic of topographical features related to water flow, and to compare the yield differences between the treatments across a range of the WI values. Variability of yields in NT and CTO systems was better explained by precipitation in early spring and during pollination and grain fill than that in CT and CTL. No-till and CTL tended to produce higher maximal yields than CT at the summit/steep-sloped areas (lower WI), while at intermediate and high WI levels the differences between them were inconsistent. The CTL often produced higher maximal yields than CTO at low and intermediate WI values, while the difference between them was mostly not significant at high WI levels (depression areas). The nonparametric spline regression algorithm used in the study was robust and efficient in comparing the yield differences between treatments across a range of WI values.

Abbreviations: LTER, Long Term Ecological Research site • KBS, Kellogg Biological Station • CT, chisel plowed with conventional chemical inputs • NT, no-till with conventional chemical inputs • CTL, chisel plowed with low chemical input and a winter leguminous cover crop • CTO, organic-based chisel plowed with a winter leguminous cover crop • WI, wetness index

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.

Received for publication October 1, 2007.