| heal.abstract |
The effect of nitrogen application on biomass accumulation and nutrient uptake by okra (Abelmoschus esculentus (L.) Moench.) grown in an unheated greenhouse was determined. Nitrogen (N) was applied in the form of a liquid feed at 0 (N-0), 150 (N-150) and 300 (N-300) ppm while other nutrients were maintained at a constant level. The accumulation of dry matter in the aerial plant parts (DMAe) and nutrient uptake (N, P, K, Ca, Mg) by the aerial plant parts (NUe) were recorded throughout the growth period. The data were analysed with the aid of logistic equations to determine the maximum daily DMAe and total NUe in relation to DMAe. Both DMAe and NUe follow a sigmoid curve, accurately described by a logistic equation. From the results it was found that during growth there was a period when DMAe occurred at an intense rate. The time of onset of this period and its duration varied with N application. Maximum daily DMAe (RDMAe) as well as maximum daily NUe (RNUe) occurred when 50% of the maximum DMAe and NUe had been achieved, irrespective of N application. The maximum daily uptake of N (RN-NUe) and K (RK-NUe) by the plant occurred about 2-6 days earlier than the RDMAe, irrespective of N-level. In addition, although the uptake of P (P-NUe) was low, maximum daily P-NUe also occurred prior to the maximum daily DMAe. However, the maximum daily uptake of the other ions that were measured (Ca and Mg) was less clearly defined. |
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