Sorghum intercropping effects on yield, morphology, and quality of forage soybean

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.