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Ecological and practical significances of crop species preferential N uptake matching with soil N dynamics

Zhang, Jinbo, Wang, Jing, Müller, Christoph, Cai, Zucong
Soil biology & biochemistry 2016 v.103 pp. 63-70
runoff, mineralization, rice, nutrient use efficiency, nitrogen, cucumbers, nitrification, climatic factors, leaching, soil, potatoes, pH, plant response, ecosystems, denitrification, ammonium nitrate, ammonium nitrogen
Nitrogen (N) transformation dynamics are often adapted to the prevailing climatic conditions and also in response to plant N uptake characteristics of species in natural ecosystems. Thus, the interplay between plant species preferential N uptake and soil N transformation characteristics is key to an optimized N use efficiency (NUE) and the understanding how N losses via denitrification, leaching or runoff can be minimized. However, despite the intimate connection between plant and soil N characteristics is well known, only a few quantitative studies are available that address these internal ecosystem connections on a mechanistic level. In this study, the N recoveries and N balances of cucumber, potato and rice, which differ in their preferential N-uptake, were investigated under different pH conditions (pH 4.9 and 7.8, respectively). N recoveries of applied 15N either as nitrate or ammonium in plant and soil were determined and N losses were calculated by 15N balance. The results indicate that not only the match of the applied dominant N form with the optimal preferential N-uptake of crop species, but also soil N transformation characteristics could significantly affect the recoveries and losses of applied 15N. Crops preferring ammonium took up more of the applied ammonium-N in the soil characterized by low N/M (nitrification rate/mineralization rate) ratios than in the soil with high N/M ratios. In contrast, crops preferring nitrate took up more applied ammonium-N in the soil with high N/M ratios than in the soil with low N/M ratios. A match exists between the applied N form with crop species preferential N uptake and that soil gross N transformation dynamics playing an important role in providing an essential support for the specific plant associated N use. It is the intimate connection between plant and soil N dynamics that is critical for an enhanced NUE with reduced N losses in monoculture agricultural systems. These observations can serve as a blueprint for the introduction of new crop species by taking into account site-specific soil and climatic conditions as well as known plant N-uptake characteristics.