Drought and nitrogen source effects on nitrogen nutrition, seed growth, and yield in soybean.
1996
Purcell L.C. | King C.A.
Drought in soybean [Glycine max (L.) Merr.] decreases yield-related processes and N2 fixation is more sensitive to drought than are many other of these processes. Therefore, application of nitrogen (N) fertilizer may increase drought tolerance over those plants primarily dependent on N2 fixation. In a field experiment, NH4NO3 applications (+N) to drought-stressed soybean resulted in biomass and N accumulation rates similar to those rates for an irrigated treatment without N fertilizer (-N). In contrast, biomass and N accumulation rates were decreased for the -N treatment. N fertilization increased seed growth rate and decreased seed fill duration for irrigated and drought treatments. In the drought treatment, N application increased seed number per unit area, which resulted in higher yields. In a greenhouse experiment, fertilization with either KNO3 or NH4Cl increased biomass and N accumulation rates during drought over those of plants dependent solely on N2 fixation. It was concluded that application of N fertilizer to soybean increases drought tolerance because of the extreme sensitivity of N2 fixation to drought.
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