Uptake of Calcium and Magnesium by Cotton Grown under Dryland Conditions
The mid-1940s was the last time an intensive study of the Ca and Mg nutrition of cotton (Gossypium hirsutum L.) was conducted in the USA. Since that time cultivars and cultural practices have changed, thus, field studies were conducted for 2 yr to evaluate the Ca and Mg uptake characteristics of four cultivars that are representative of those now produced in the South: ‘Deltapine 90’, ‘Stoneville 825’, ‘Coker315’ and ‘Paymaster 145’. They were grown on a nonirrigated Decatur silt loam (clayey, thermic, kaolinitic, Rhodic Paleudults) and a nonirrigated Norfolk fine sandy loam (fine loamy, thermic, siliceous, Typic Paleudults) in Alabama. Plants were collected at 2-wk intervals throughout the growing season, beginning at 15 d after emergence, partitioned into leaves, stems, burs, seed, and lint, and analyzed (except for lint) for Ca and Mg. Total Ca and Mg uptake when averaged for both soils and all four cultivars was 64 and 18 kg ha−1, respectively (or 9.3 kg of Ca and 2.6 kg hlg per 100 kg lint produced). Total Ca uptake was significantly lower on the Norfolk soil (44 kg ha−1) as compared to the Decatur soil (75 kg ha−1) which had a higher level of extractable Ca. There were no cultivar differences in total Ca and Mg uptake or uptake within a given plant part. There were no consistent differences among the cultivars for the concentration of Ca in the various plant parts. The concentration of Mg in the leaves and burs was affected by the cultivar. These cultivars accumulated similar amounts of Ca and Mg as compared to older cultivars, although previous research has shown that modern cultivars partition dry matter differently from older cultivars.
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