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Introducing Winter Cover Crops In
a Maize-Soybean Rotation In Illinois

Germán Bollero Germán Bollero
Asst. Prof. of Biometry and Cropping Systems
Department of Crop Sciences
(217) 333-9475; gbollero@illinois.edu
Matías Ruffo
  Matías Ruffo
Graduate Research Assistant
Department of Crop Sciences
(217) 244-8421; ruffo@illinois.edu
Stephanie Crandall  

Stephanie Crandall
Graduate Research Assistant
Department of Crop Sciences
(217) 244-8421; scrandal@illinois.edu

The state of Illinois utilizes in excess of 27 million acres of land for agriculture, and approximately 88 percent of that is used for row crop agriculture. Most of that acreage is in a corn-soybean rotation. The problem is that the use of short rotations and intensive and extensive tillage practices in the region has reduced soil quality and thus the agronomic potential and ecosystem services of many fields.

Winter cover crops have long been recognized as possible tools for maintaining and improving soil quality and consequently addressing production and environmental concerns in agriculture. Winter cover crops used in a corn (Zea mays, L) and soybean (Glycine max, L Merr.) rotation can be a legume, a grass, or a mixture of the two. In the U.S. Central Corn Belt, hairy vetch (Vicia villosa Roth) is the preferred legume, while rye (Secale cereale L.) is the preferred grass. Hairy vetch is mainly used as a nitrogen (N) source for cash crops. Rye is utilized as a catch crop for residual nitrates and presents a vigorous growth in the fall and winter hardiness that provides soil cover.

Field trial of hairy vetch accessions

Figure 1. Field trial of hairy vetch accessions.

This study had two objectives. The first was to evaluate how changes in the level of soil quality will benefit production and environmental aspects of Illinois’ farming systems. The second was to relate changes in soil quality derived from the use of winter cover crops to crop production and critical soil functions.

This is a six-year study, and results from 1999, 2000, 2001, and 2002 will be presented. A trial comparing corn-soybean grown in a rotation with and without cover crops has been established at three University of Illinois research stations. In the cover-cropped plots, hairy vetch, rye, and a mixture of hairy vetch plus rye was planted after soybean and before corn. Cover crop biomass, biomass composition, crop yields, and N dynamics are being evaluated.

Maize grown after hairy vetch had a higher biomass and N status at the beginning of the growing season compared to the control. Rye, either alone or in biculture, was deleterious for crop growth. These effects disappear later in the season, and N fertilizer is the factor affecting crop growth and N status. In Urbana and DeKalb, hairy vetch did not add yield to maize compared to the control. At these locations, the biomass production of hairy vetch was limited by lower temperatures. In Brownstown, maize grown after hairy vetch had higher yields compared to the control. At all locations, rye in monoculture caused a significant yield reduction. In contrast with the results of other authors, cover crops in this experiment did not affect maize population. Hairy vetch dry matter accumulation and N fixation is of limited agricultural value at Urbana and DeKalb. In Brownstown, hairy vetch N concentration was lower than expected. The use of rye and hairy vetch mixture does not significantly affect dry matter production and chemical characteristics of its components.

To decide the potential use of cover crops, dry matter should be considered, but residue quality (N, hemicellulose, and cellulose concentration) also plays a major role on their impact. Hemicellulose affects C and N decomposition kinetics through its effect on decomposition rate and percent C remaining at the end of the growing season.

Although preliminary, these results show the importance of biomass quality and volume on long-term benefits for cropping systems. The amount and quality of residue decomposition from winter cover crops plays a major role in different aspects of soil quality and may improve long-term cropping system performance in Illinois. Specifically, we were able to model timing of nitrogen availability for the summer crop based on initial residue quality.

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