SOME EFFECTS OF SOIL TEMPERATURE ON PHOSPHORUS REQUIREMENTS OF YOUNG CORN PLANTS IN THE GREENHOUSE

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Abstract
Germinated corn seedlings were planted in Burford loam soil in 1-gal. glazed pots and allowed to grow for 8 weeks in the greenhouse. Two levels of phosphorus, 0 and 20 p.p.m P2O5, were used, along with a uniform treatment of nitrogen and potassium fertilizer. Carrier-free phosphorus-32 was placed in the bottom of the pot as compared with mixing throughout to indicate regions of root activity. One set of pots, consisting of four replications per treatment, was placed in a water bath averaging approximately 13 °C. A corresponding set was placed on the greenhouse bench where temperature averaged approximately 20 °C. Air temperature was the same for both sets.Although the soil used for this study tested high in acid-soluble phosphorus and thereby suggested a low fertilizer phosphorus requirement, the use of phosphorus fertilizer significantly increased both the yield and phosphorus uptake of corn plants. Moreover, the relative increase for fertilizer was much greater under low temperature than under high temperature conditions. This was due to an actual reduction in phosphorus percentage in fertilized plants grown at the higher temperature while the reverse was true at the lower temperature level.Root activity, particularly in the bottom portion of the pots, was reduced by low temperature, but phosphorus fertilizer partially overcame this effect. The consequence of these effects on growth of corn in the field, and on soil test correlation work, is mentioned.

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