Growth Rate and Water Use by Legume Species at Three Soil Temperatures

Legumes may be used to reduce fertilizer inputs, provide ground cover for soil erosion protection, and reduce residual soil nitrates. Little data are available to guide a producer in selecting a legume that matches water and temperature conditions and produces acceptable growth and N 2 ‐fixation rates. The purpose of the experiment reported here was to provide such information. After a 14‐d germination period at 20 °C, we grew eight legume species at soil temperatures of 10, 20, and 30 °C (± 2 °) for 105 d in a greenhouse. Daily water use was recorded, and plant dry weights were measured every 21 d. Initially annual species such as soybean [ Glycine max (L.) Merr.] and fababean ( Vicia faba L.) grew fastest at all temperatures. For the first 42 d at 10 °C, white clover ( Trifolium repens L.), crimson clover ( Trifolium incarnatum L.), and hairy vetch ( Vicia villosa L.) also exhibited rapid growth. With warmer temperatures and longer growth periods, lespedeza ( Lespedeza stipula L.) as well as soybean grew rapidly. At 20 and 30 °C, soybean growth was often more than double that of most other species. Growth was maximal at 10 °C for fieldpea ( Pisum arvense L.), hairy vetch, and crimson clover; at 20 °C for fababean and white clover; and at 30 °C for soybean, sweetclover ( Melilotus alba L.), and lespedeza. Average water‐use rates and water‐use efficiency generally paralleled growth, except water use increased and water‐use efficiency decreased as soil temperature increased. These results indicate that growth and water use differed greatly among legume species, that each legume species has its own characteristic optimum growth temperature, and that this optimum temperature for a given species may change as growth progresses.