Rate of Nutrient Uptake per Unit of Corn Root Under Field Conditions
1974
Mengel, D. B. | Barber, S. A.
Information on changes in the rate of nutrient uptake per unit of plant root length (nutrient flux) during the growth of the plant is important for evaluating the capacity of the soil to supply sufficient nutrient to the root surface. Since little information was available, nutrient flux into the root was determined in the field by sampling corn (Zea mays L.) plants at 9 and 14 dates in 1970 and 1971, respectively. Root length, root fresh weight, shoot dry weight, and content of 10 nutrients in the shoot were determined on replicated samples at each harvest. Nutrient uptake rates per plant per day were calculated and divided by mean root lengths to get nutrient flux into the root as related to plant age. Nutrient flux was greatest at the first sampling, decreased rapidly with increased plant age until plants were 70 days old, and then remained relatively constant. Phosphorus flux into the root was 11.3 μmoles per meter of root per day at 20 days and 0.08 μmoles m⁻¹d⁻¹ at 80 days. Mean flux into the root was similar in both years despite large grain yield differences between years. As the flux may be biased downward with older plants because of lower uptake rates by more mature tissue, efforts were made to overcome the bias by assuming that only roots less than 5 days old actively absorbed nutrients. Flux calculations on this basis still decreased as the plant developed, but the differences were smaller.
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