Soybean N-2 fixation estimates, ureide concentration, and yield responses to drought

作者：Purcell LC^*; Serraj R; Sinclair TR; De A

来源：Crop Science, 2004, 44(2): 484-492.

Increasing N-2 fixation tolerance to drought has been hindered by the labor and costs of quantifying N-2 fixation using N-15 methodologies. The relative abundance of ureides (RAU) in plant tissues has been used for estimating N-2 fixation in soybean [Glycine max (L.) Merr.] grown under well-watered conditions, but it has not been evaluated for drought conditions. The present research evaluated the response of N accumulation to N fertilization, the ability of the RAU technique to predict N-2 fixation under drought conditions, and the response of yield to N fertilization under well-watered and drought conditions. Under drought, shoot N accumulation rate during vegetative growth approximately doubled as the amount of N fertilizer was increased from 10 to 200 kg N ha(-1), indicating a greater sensitivity of N-2 fixation to drought than uptake and assimilation of inorganic N. Under well-watered conditions, the relationship between estimates of N-2 fixation made by N-15-dilution and RAU agreed within 15% of published reports. Under drought conditions, however, this relationship was greatly different (13 to 43%) from published reports. Fertilization with inorganic N in 1 yr increased grain yield 15 to 25% for the drought treatment and 12 to 15% for the well-watered treatment. In a second year, N fertilization increased yield of both drought and well-watered treatments approximately 9%. This research indicates that the RAU technique for estimating N-2 fixation under drought conditions may be invalid without further refinement, that N-2 fixation is more sensitive to drought than the uptake and assimilation of inorganic soil N, and that increasing the tolerance of N-2 fixation to drought would likely result in yield increases.

• 出版日期2004-4