Abstract
Most studies dealing with the utilization of 15N labeled plant material do not present details about the labeling technique. This is especially relevant for legume species since biological nitrogen fixation difficults plant enrichment. A technique was developed for labeling leguminous plant tissue with 15N to obtain labeled material for nitrogen dynamics studies. Sun hemp (Crotalaria juncea L.) was grown on a Paleudalf, under field conditions. An amount of 58.32 g of urea with 70.57 ± 0.04 atom % 15N was sprayed three times on plants grown on eight 6-m²-plots. The labelled material presented 2.412 atom % 15N in a total dry matter equivalent to 9 Mg ha-1 This degree of enrichment enables the use of the green manure in pot or field experiments requiring 15N-labeled material.
Highlights
The use of the stable isotope 15N can help to identify nitrogen sources and is important for research on nitrogen dynamics in the soil-plant system
The 15N labeling of green manures allows the determination of the amount of the nutrient in the soil and in the subsequent crop derived from the green manure which is only feasible with the use of isotopic methods
Ambrosano (1995), using the techniques later described by Ambrosano et al (1997) for velvet bean and sun hemp, determined that 60 to 80% of plant nitrogen remained in the soil, 20 to 30% were absorbed by corn plants, and 5 to 15% were lost from the soil-plant system
Summary
The use of the stable isotope 15N can help to identify nitrogen sources and is important for research on nitrogen dynamics in the soil-plant system. Ambrosano et al (1997) established a 15N labeling technique for legumes growing in a greenhouse, and obtained a dried material with 3.177 and 4.337 atom % 15N, for velvet bean and sun hemp, respectively. Ambrosano (1995), using the techniques later described by Ambrosano et al (1997) for velvet bean and sun hemp, determined that 60 to 80% of plant nitrogen remained in the soil, 20 to 30% were absorbed by corn plants, and 5 to 15% were lost from the soil-plant system. (1985) investigated the incorporation of Sesbania aculeata residues labeled with atom % 0.617 in 15N excess, and determined that only 5% of the N from the legumes was absorbed by the corn plants. For more accurate (Bartholomew, 1965) and trustable results labeling level of at least 2 atoms % 15N excess is needed
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