Relay intercropping legumes into vegetable crops provides cover and gr
een-manure benefits to subsequent crops, but has not been adequately r
esearched in high desert regions. This study evaluated the dry matter,
N yield, effect on a subsequent forage sorghum [Sorghum bicolor (L.)
Moench] crop, and estimated fertilizer-replacement value (FRV) of seve
ral legumes interseeded into sweet corn (Zea mays L.). The study took
place under furrow irrigation in north-central New Mexico (study site
elevation, 1737 m) on a Fruitland sandy loam (coarse-loamy, mixed, cal
careous, mesic Typic Torriorthent). Five legumes (hairy vetch, Vicia v
illosa Both; barrel medic, Medicago truncatula Gaertn.; alfalfa, Medic
ago sativa L.; black lentil, Lens culinaris Medik.; and red clover, Tr
ifolium pratense L.) were interseeded into sweet corn at last cultivat
ion or blister stage in 1993 and 1994. Corn ears and stover were harve
sted in August. The following spring, plots were plowed and seeded to
forage sorghum. Estimated FRV for the legumes were calculated from reg
ression equations for sorghum dry matter yield as a function of N fert
ilizer rate. Herbage N yields in the fall were greatest for hairy vetc
h and barrel medic and, averaged across interseeding dates, ranged fro
m 55 to 64 kg ha(-1) in 1993 and 100 to 108 kg ha(-1) in 1994. Whole-p
lant N yields (herbage + roots + crowns) in May were greatest for hair
y vetch, 205 kg ha(-1) in 1994 and 172 kg ha(-1) in 1995. Seasonal dry
matter yield and N uptake of sorghum were greatest following hairy ve
tch in 1994, and hairy vetch and alfalfa in 1995. Based on seasonal so
rghum yield, hairy vetch and alfalfa had the highest FRV, ranging from
78 to 140 kg ha(-1) N.