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Sulphur nutrition of peanut

Supakamnerd, Nantarat (1991) Sulphur nutrition of peanut. PhD thesis, Murdoch University.

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Abstract

Three glasshouse trials were conducted to examine the effects of sulphur (S) deficiency on growth and development of peanut (Arachis hypogaea L. cv. White Spanish) on a sandy soil of low fertility. In the first experiment, the relationship between total sulphur concentration in plant parts and vegetative shoot yield was investigated at a range of developmental stages and criteria for diagnosing sulphur deficiency and predicting seed yield were obtained. In a second trial, the effect of nitrogen source (inorganic and biologically fixed nitrogen) on the response of peanut to sulphur fertilization and critical sulphur concentrations for diagnosis of sulphur deficiency and prognosis of seed yield were examined. Timing of sulphur application to correct sulphur deficiency symptoms and to increase seed yield was examined in a third trial.

Sulphur deficiency symptoms (yellowing of leaves) first appeared in young leaves and spread to older leaves when plants were severely deficient. Both vegetative shoot and reproductive dry matter yields were depressed by sulphur deficiency. Furthermore, the number of reproductive parts (pegs and pods), individual seed dry weight and seed sulphur concentrations were reduced in sulphur deficient plants.

Nitrogen source did not affect the expression of sulphur deficiency symptoms, plant growth or sulphur concentrations in reproductive parts. Although sulphur concentrations in the older parts of the stem were elevated in plants supplied with ammonium nitrate, critical sulphur concentrations in young leaves were not affected by nitrogen treatment.

Generally, critical sulphur concentrations in leaves for diagnosis and prognosis of sulphur deficiency declined with plant age. Sulphur concentrations in the young open leaf (YOL) and the youngest fully expanded leaf (YFEL) accurately reflected the sulphur status of the plant. However, the YFEL was chosen, in preference to the YOL, as an index tissue because it is more easily recognised in the field.

Critical sulphur concentrations in the YFEL, derived from hand-fitted curves, for diagnosis of sulphur deficiency of peanut plants were 0.22-0.23% S at pod formation and 0.15-0.18% S at early pod filling. Critical sulphur concentrations in the YFEL for predicting seed yield at early pod filling were 0.25-0.28% S at flowering and 0.23% S at pod formation. These critical sulphur concentrations, for both diagnosis and prognosis, were generally in agreement with the critical sulphur concentrations, corresponding with 90% maximum yield, derived from the Smith and Dolby two-phase linear procedure.

Critical total N/total S ratios [(N/S)t] in the YFEL for diagnosis of sulphur deficiency in inoculated peanut plants were 18 at pod formation and 17 at early pod filling, whereas the critical (N/S), ratios for predicting seed yield at early pod filling were 9 at flowering and 15 at pod formation. However, because the (N/S)t ratios were not always closely correlated with yield and varied with both sulphur and nitrogen supplies, it is recommended that diagnosis and prognosis of the sulphur status of peanut plants be determined from total sulphur concentrations in the YFEL.

Topdressing with sulphur either at pegging or late pod filling strongly stimulated vegetative shoot dry matter production in sulphur deficient plants but it did not further enhance growth in sulphur adequate plants. Furthermore, sulphur deficient plants which received a topdressing of sulphur at pegging absorbed so much sulphur that young leaves developed necrotic symptoms along the leaf margins and sulphur concentrations in these leaves were extremely high (about 1% S, mostly as sulphate sulphur). However, necrosis did not occur on young leaves of sulphur deficient plants which received a split dose of sulphur at late pod filling or on plants supplied with adequate sulphur.

During development of reproductive organs, there was little net redistribution of sulphur from vegetative shoots to reproductive parts. Thus, the sulphur demand by the developing seeds was met by uptake of sulphur from the soil, possibly through the pericarps as well as the roots. Early topdressing with sulphur at pegging to sulphur deficient plants enhanced reproductive growth allowing them to produce up to about 80% of the seed yield in plants continuously supplied with adequate sulphur. Later application of sulphur, at late pod filling, was less effective in restoring seed yield.

Item Type: Thesis (PhD)
Murdoch Affiliation: School of Biological and Environmental Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au. Thank you.
Supervisor(s): Dell, Bernard
URI: http://researchrepository.murdoch.edu.au/id/eprint/51900
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