Intercropping Corn and Soybean to Increase Forage Protein ...

AGRONOMY DEPARTMENT 1575 Linden Drive University of Wisconsin-Madison 53706 608-262-1391/2
Field Crops June 1991
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28.5

Intercropping Corn and Soybean to Increase Forage Protein Concentration
Prepared by P.R. Carter, E.S.Oplinger, and D.J. Undersander, Extension Agronomists, University of
Wisconsin-Madison

Each year we receive questions regarding the potential to increase corn silage protein
concentration by intercropping corn and soybean.
The accompanying table summarizes results of a corn/soybean intercropping study conducted
in Massachusetts, which has a growing environment fairly similar to Wisconsin.
Monoculture corn was planted in 36-inch rows, to achieve final stands of about 28-30,000
plants/acre. Two narrow (12-inch) soybean rows replaced every third corn row in corn-corn-soybean
and every other corn row in corn-soybean planting patterns. Soybeans were seeded to give a final
stand of 160,000 plants/acre (about 6 plants per ft. of each double row).
Weeds were controlled chemically with alachlor (Lasso) and linuron (Lorox), applied
reemergence, and dinoseb (no longer registered) , applied post-emergence. Nitrogen fertilizer was
broadcast at 110 to 140 Ibs/acre. Soybean cultivar maturity was matched to corn hybrid maturity, so
that optimum maturity occurred for both when forage was harvested.
Intercropping increased forage protein concentration by 1-2 units, but reduced total forage
yields by 5-10X, compared to monoculture corn for forage (See table) . Research with monocrop
soybean conducted in Wisconsin found similar maximum soybean forage yields of 3.3 tons/acre with a
crude protein of 19.2.

Total forage dry matter yields and yield contribution of corn and soybean in carious cropping patterns
(Two-year average, Massachusetts).

Forage
DM
Yield

Planting patterns
Corn
Soybean
Total
Crude protein





------------------------Tons/A
------------------------
%
Monoculture soybean
---
3.3
3.3
20.1
Monoculture corn
8.0
---
8.0
8.0
Corn-corn-soybean 6.9
0.8
7.7
9.2
Corn-soybean 5.8
1.4
7.2
10.1

There are several management concerns that growers should consider beforemixing corn and
soybean grown for forage:
- Optimum planting date for corn is slightly earlier than that for soybean.
- Matching corn hybrids and soybean varieties, planted on the same date, so that both reach
optimum maturity for forage harvest at the same time may be difficult. (Soybeans should be
© 2004 Board of Regents of the University of Wisconsin System, doing business as the Division
of Cooperative Extension of the University of Wisconsin-Extension.

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Soybean and Small Grains
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at full bean pod, R7, and corn or near 1/2 to 3/4 kernel milkline stage to maximize forage
yield and quality).
- Weed control may be difficult, unless weed species present can be controlled mechanically
or with herbicides which are compatible with both crops.

Usually, the relatively small increase in protein concentration with corn/soybean intercropping
will likely not offset the forage yield decrease compared to monocrop corn, especially given the
management difficulties that may be encountered. An alternative way to increase forage protein
content is to plant one-half the field to each crop and chop one row of each per round to mix while
chopping. This would likely result in greater increases in forage protein content that intercropping corn
and soybean, but forage yields per acre for the field would be about 30% lower than for corn grown
alone.

In most situations, protein levels in rations including corn silage could be increased more
effectively by adding protein supplement using soybean meal or whole soybean at feeding time.

Reference

Herbert, S. J., D.H. Putnam, M.I. Poos-Floyd, A. Vargas, and J.F. Creighton. 1984. Forage yield of

intercropped corn and soybean in various planting patterns. Agron. J. 76: 507-510.

Hintz, R.W., K.A. Albrecht, and E.S. Oplinger. 1991. Yield and quality of soybean forage as affected by
cultivar and management practices. Agron. J. (submitted).




© 2004 Board of Regents of the University of Wisconsin System, doing business as the Division
of Cooperative Extension of the University of Wisconsin-Extension.

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