Shading patterns when two forage species are intercropped may be different
than in a monocrop environment. Our objectives were to quantify yield and f
orage quality response of forage soybean [Glycine mar (L,) Merr,] intercrop
ped with forage sorghum [Sorghum bicolor (L.) Moench] and compare to the me
asurements of monocrop soybean. Soybean plants were harvested from the midd
le portion of individual rows in plots containing only soybean and from plo
ts having alternating soybean and sorghum rows spaced 76 cm apart. Morpholo
gical and forage quality measurements were determined on leaf and stem frac
tions. Morphological measurements included main stem length, node number, l
eaf area ratio (LAR), specific leaf weight (SLW), and stem diameter. Forage
quality constituents included in vitro dry matter disappearance (IVDMD), n
eutral detergent fiber (NDF), hemicellulose, and cellulose, and crude prote
in (CP) concentrations. Intercropped soybean had 6 more plants m(-1) of row
, less advanced morphological development, and 2.3 Mg ha(-1) less dry matte
r than monocrop soybean. Leaf IVDMD, NDF, hemicellulose, and cellulose did
not differ between intercrop and monocrop soybean. However, stem IVDMD was
33 g kg(-1) greater for intercropped than monocrop soybean, reflecting: the
36 g kg(-1) decrease in NDF concentration. Intercropped soybean was lodged
both years more than monocrop soybean, which may have been due to the sign
ificant decrease in stem NDF. Leaf CP concentration was 25 g kg(-1) greater
for monocrop soybean than intercropped soybean; however, stems from interc
ropped soybean had 12 g kg(-1) greater CP than monocrop soybean stems. Soyb
ean exhibited a high degree of morphological plasticity, presumably in resp
onse to increased competition for solar radiation. Although forage quality
of intercrop soybean was greater than monocrop soybean, intercropping forag
e-type soybean with another tall-growing forage does not appear to be pract
ical because of the decrease in dry matter accumulation.