Mitteilungen der Gesellschaft für Pflanzenbauwissenschaften Band 23

Mitt. Ges. Pflanzenbauwiss. 23: 216 (2011)
Effect of N form on the behavior of N in floodwater, soil solution and
the N uptake of rice (Oryza sativa L.)
Katja Bogdan and Joachim Lammel
Research Centre Hanninghof, YARA GmbH & Co. KG, Dülmen. E-Mail: katja.bogdan@yara.com
Introduction
Low N use efficiency due to ammonia (NH3) volatilization and denitrification after
urea and nitrate (NO3 - ) application, respectively, is a challenge in flooded rice
cultivation. N plant uptake after N application competes with N losses and the uptake
efficiency of N forms is under discussion in literature. Rice has long been regarded
as preferring NH4 + and the application of urea is common practice. However, a study
of Kronzucker et al. (2000) indicated that rice has a high N-acquisition and yield
potential when growing on NO3 - . In this study the behavior of N in floodwater and soil
solution and the effect of N form on biomass and yield was studied.
Materials and Methods
Oryza sativa L. Cv IR7521 (Hybrid) was cultivated in pots in the greenhouse until
maturity. Plants received N in form of either urea or Ca-Nitrate in 4 split applications.
Soil solution and floodwater was sampled before and after N application and
analysed on N form with the Autoanalyszer. The soil solution was sampled by means
of suction cups at 3 depths. Plants were harvested shortly before and 6 days after
each N application. The N content of the plant samples were determined by the
Kjeldahl method.
Results and Discussion
A faster decrease of N concentration in floodwater was observed after urea than after
NO3 - application. N concentration in soil solution in 2.5 cm depth was about 10 times
higher after NO3 - than NH4 + application, reflecting the higher mobility of NO3 - in soils.
In general, high amounts of applied N (up to 91% after urea application) were taken
up by the plant within only 6 days after N application. Considerably less N was taken
up after NO3 - compared to urea application although NO3 - -N was still present in
floodwater at harvest 6 days after N application. This indicates a lower N uptake
efficiency after NO3 - than after urea application. Grain yield was 32% lower after NO3 -
than after urea application. In contrast, the straw yield was not affected by the N form
indicating that urea could support grain set and filling better than NO3 - .
References
Kronzucker, H.J., A.D.M. Glass, M.Y. Siddiqi, G.J.D. Kirk 2000: Comparative kinetic analysis of
ammonium and nitrate acquisition by tropical lowland rice: implications for rice cultivation and yield
potential. New Phytologist 145:471-476.