Effect of N Starvation of Soybean Plants at Various Stages of Growth on Seed Yield and N Concentration of Plant Parts at Maturity 1
1978; Wiley; Volume: 70; Issue: 1 Linguagem: Inglês
10.2134/agronj1978.00021962007000010017x
ISSN1435-0645
Autores Tópico(s)Nematode management and characterization studies
ResumoAbstract Estimates of the minimum N concentrations of vegetative soybean ( Glycine max (L.) Merr.) plant parts are needed to assess the N supplying capacity of these tissues during seed development. Also, little is known about how the plant responds to severe N stress during reproductive growth in terms of redistribution of N among plant parts and in terms of leaf senescence. The purpose of this experiment was to determine the effect of N starvation of soybean plants at various stages of growth on seed yield and N concentration of plant parts at maturity. Non‐nodulated soybean plants were grown in sand culture with a nutrient solution containing 100 mg N/liter and adequate levels of other major and minor elements. Nitrogen was withdrawn from the solution near the end of the flowering period or during rapid pod formation or during rapid seed formation; these withdrawal times were 65, 76, or 87 days after planting (DAP), respectively. The shortest period of N stress (withdrawal 87 DAP) resulted in marked decreases in individual seed weight and N concentration but did not result in premature leaf senescence or in a decline in N concentration of vegetative organs or a decline in the number of fruits and seeds per plant. Longer periods of N stress (N withdrawal 65 and 76 DAP) caused major reductions in pod and seed numbers as well as further decreases in seed weight and in N concentrations in seeds and vegetative organs. Concentrations of 1.0% N in leaves, 0.5%, N in stems, and 1.3% N in roots (dry basis), observed under conditions of extreme N stress, are estimates of the lower limits of N in these soybean tissues after maximum export of N. However, these lower limits were not reached until the amount of N stored in seeds was reduced by greater than 50%.
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