Effect of Soil Depth and Plant Age on 32Phosphorus Uptake by Corn and Sorghum
1969
Carrier-free H₃³²PO₄ was injected into a Sharpsburg silty clay loam soil at depths of 15, 30, and 61 cm when corn (Zea mays L., vat. ‘Nebraska 202’) and sorghum (Sorghum bicolor (L.) Moench, var. ‘Nebraska 505’) plants were 23, 39, and 59 days old. At the 23-day age most ³²P was taken up by roots in the upper 15 cm. Corn roots penetrated to a 61 cm depth earlier than sorghum roots. As the season progressed, sorghum lateral root activity at the 30 and 61 cm soil depths became important. Following the radioactive P injections when plants were 59 days old, sorghum took up more ³²P than corn. Plant age or depth of injection had little effect on the ³²P contributed by roots at varying distances from the source. Roots which extended laterally beyond 66 cm contributed little to the P nutrition of either corn or sorghum grain. Both corn and sorghum had root systems that penetrated to a depth of 152 cm and extended laterally 238 cm.
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