UTILIZATION OF 15N LABELED RICE STRAW FOR TRACKING NITROGEN DISTRIBUTION WITH INDICATOR OF MAIZE PLANT

Abstract

The purpose of this study was to describe the nitrogen distribution of rice straw residues (RS)  applied to the soil. ¹⁵N-labeled rice straw derived from rice plants grown with different ¹⁵N concentration supply during rice growth that are 0 mM (N0), 0.625 mM (N1), 2.5 mM (N2), and 10 mM (N3). They were planted on plastic pots of 30 cm diameter containing 5 kg of quartz sand and placed in the green house. After 8 weeks, the rice is harvested and its  biomass was dried at 60 ° C for 48 hours and then analyzed its quality. The four kinds of RS with different ¹⁵N supply (N0; N1; N2; N3) were  used for two types experiment namely: (1) non leaching incubation experiment to determine the dynamics of N mineralization in soil, and (2) pot experiments conducted using maize plant indicator  in the green house to know the amount of the N uptake and N distribution, plus a control treatment (without RS residue). Results showed that RS with different 15N concentration supply produce different qualities. The  RS residues contained N by 1.05-2.04%, 15N-excess by 0.92 - 2.78%, lignin 4.24 -23.54 % and polyphenols 4.74% - 6.78%. The highest total mineral nitrogen released during the 14-week incubation was found at a 10 mM concentration treatment (N3) by 57.46%. Total N absorbed by maize plants in this treatment amounted to 28.15%. From this amount, 61.47% derived from the RS applied to the soil and 38.53%  derived from the soil.

Key words : rice straw, ¹⁵N concentration, N uptake, ¹⁵N uptake