A Method for Measuring Short‐Term Nutrient Absorption by Plants: I. Phosphorus

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Abstract
A method has been devised which permits measurement of P absorption by plants during relatively short periods of root‐soil contact. Plants are grown without added P in sand during which time a mat of roots develops at the bottom of the container. The exposed root mat with plants intact is then placed in contact with the soil or soil‐fertilizer system. Results obtained using oats as the principal crop and concentrated superphosphate applied to Hartsells fine sandy loam support the following conclusions: (1) P uptake by oats from applied fertilizer increased linearly with time between 1 and 7 days and increased linearly with rates of applied P ranging from 0 to 50 mg. or more per 200 g. soil. (2) Moisture equivalent was approximately the optimum soil moisture level for P absorption. (3) Recovery of applied P commonly ranged from 2 to 5% after absorption periods of 3 to 7 days. The method holds considerable promise as a means of studying the influence of various factors on P absorption by plants. These include environmental factors as well as soil and fertilizer characteristics.