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This article in AJ

  1. Vol. 80 No. 1, p. 125-130
     
    Received: Apr 1, 1987
    Published: Jan, 1988


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doi:10.2134/agronj1988.00021962008000010027x

Calcium Deficiency in Sorghum Grown in Controlled Environments in Relation to Nitrate/Ammonium Ratio and Nitrogen Source

  1. H. M. Murtadha,
  2. J. W. Maranville  and
  3. R. B. Clark
  1. Dep. of Computer Sci., Univ. of Nebraska, Lincoln, NE 68583

Abstract

Abstract

Sorghum [Sorghum bicolor (L.) Moench] grown under growth chamber and greenhouse conditions often develops Ca deficiency. Since information on factors affecting Ca uptake and distribution in sorghum is limited, experiments were conducted to better understand factors associated with the enhancement of this disorder. Sorghum genotypes ‘Redlan’ and ‘Martin’ were grown in a growth chamber with 21.4 mM N (300 mg L−1) at NO3/NH+4 ratios of 300:0, 250:50, 200:100, and 150:150, with Ca levels of 1.25 or 2.50 mM(50 or 100 mg L−1, respectively) to determine the effects of these N ratios on sorghum growth in nutrient solution and the occurrence of Ca deficiency. The same genotypes and conditions were used in a N source experiment where NO3, NO3/NH+4 (1:1), NH+4, and urea were compared. Symptoms of Ca deficiency were visible on young leaves of plants grown in solutions containing high proportions of NO+4 and low levels of Ca, but not with NO3 only or urea. The pH of solutions in the NO3/NH+4 ratio experiment were higher with NO3 as the predominate N source. Growth and Ca concentrations decreased but total plant N concentrations increased with high proportions of NH+4 in the treatment solutions and with decreased Ca levels. Thus, N/Ca ratios increased progressively as the proportion of NH+4 in the nutrient solution increased, which also corresponded to increasing severity of Ca deficiency observed on leaves. Lower leaves had higher Ca concentrations than upper leaves indicating the relative immobility of Ca in sorghum. When comparing N sources, plants grown with NO3 or urea as the sole source of N generally had the best growth and the highest Ca concentrations, followed by plants grown with 1:1 NO3/NH+4, and NH+4 only, respectively. Dry matter yields increased with increasing solution Ca levels regardless of N source. The enhance uptake of Ca in sorghum when grown with only NO3 is believed to occur partially as a mechanism to counterbalance anion absorption and maintain proper cation/anion balance. It is likely that a reduction in Ca concentration in plants grown with high NH+4 was partially a result of reduced solution pH exerting antagonistic effects on Ca absorption or releasing Ca from cell wall anionic sites. Reduced and abnormal root growth resulting from high solution NH+4 may have enhanced the appearance of Ca deficiency symptoms by reducing Ca uptake due to reduced absorbing surface or lack of root tip growth.

Published as Paper no. 8202 in the Journal Series of the Nebraska Agric. Exp. Stn. Work supported in part by a grant from the Int. Sorghum/Millet Coop. Res. Supp. Prog. (INTSORMIL) and is part of a dissertation submitted by the senior author as partial fulfillment for the Ph.D. degree.

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