Hydroponics versus field lysimeter studies of urea, ammonium and nitrate uptake by oilseed rape(Brassica napus L.)

Abstract

N-fertilizer use efficiencies are affected by their chemical composition and suffer from potential N-losses by volatilization. In a field lysimeter experiment, (15)N-labelled fertilizers were used to follow N uptake by Brassica napus L. and assess N-losses by volatilization. Use of urea with NBPT (urease inhibitor) showed the best efficiency with the lowest N losses (8% of N applied compared with 25% with urea alone). Plants receiving ammonium sulphate, had similar yield achieved through a better N mobilization from vegetative tissues to the seeds, despite a lower N uptake resulting from a higher volatilization (43% of applied N). Amounts of (15)N in the plant were also higher when plants were fertilized with ammonium nitrate but N-losses reached 23% of applied N. In parallel, hydroponic experiments showed a deleterious effect of ammonium and urea on the growth of oilseed rape. This was alleviated by the nitrate supply, which was preferentially taken up. B. napus was also characterized by a very low potential for urea uptake. BnDUR3 and BnAMT1, encoding urea and ammonium transporters, were up-regulated by urea, suggesting that urea-grown plants suffered from nitrogen deficiency. The results also suggested a role for nitrate as a signal for the expression of BnDUR3, in addition to its role as a major nutrient. Overall, the results of the hydroponic study showed that urea itself does not contribute significantly to the N nutrition of oilseed rape. Moreover, it may contribute indirectly since a better use efficiency for urea fertilizer, which was further increased by the application of a urease inhibitor, was observed in the lysimeter study.

Silicon mitigates ammonium toxicity in plants

“…Only a few studies have addressed the effects caused by the exposure of plants to excess NH 4 + in the culture medium, with consequences in plant nutrition, especially in the decrease of the cations accumulation (such as K and Ca) in plant tissues. Some of these works were performed with Brassica napus (Arkoun et al., ), Brassica oleracea (Barreto et al., ), Zea mays (Zanin et al., ), Passiflora edulis (Silva Júnior et al., ), Eucalyptus urophylla (Guimarães et al., ), Solanum lycopersicum ( Borgognone et al., ), Pisum sativum (Ariz et al., ), and Cucumis sativus (Roosta & Schjoerring, ).…”

Molecular and physiological interactions of urea and nitrate uptake in plants

“…4,[6][7][8]39 Several authors have demonstrated that the root exposure to a combination of different N sources, led to positive effects on the nutritional status of crop plants. 6,7,40,41 In long term, the presence of both urea and nitrate enhanced plant growth 6,8 and the relative use of each N-source 7 as compared to nitrate or, especially, to urea, when provided alone. The mechanisms behind this reciprocal influence remain mostly unknown.…”

“…In wheat, when nitrate was supplied along with urea, Gln and Asn contents increased significantly in comparison to plants treated with only one N source. 6 In turn, we can hypothesize that the increase of primary assimilation might play a crucial role in determining a better use of the two Nsources when they are provided in conjunction 7 ( Fig. 1).…”

“…5 To improve the comprehension and the optimization of N nutrition in plants, a research topic of great relevance is the study of the interactions among different N-sources on the root uptake; however up to date only few works have investigated this topic. 4,[6][7][8] The present review focuses on recent evidence about the acquisition of two major N-forms, urea and nitrate, and on the reciprocal influence of these two sources on their root uptake systems.…”

Stabilising Urea Amine Nitrogen Increases Potato Tuber Yield by Increasing Chlorophyll Content, Reducing Shoot Growth Rate and Increasing Biomass Partitioning to Roots and Tubers

“…Watson and Miller 1996). In some cases, nitrogen use efficiency (NUE, the amount of nitrogen taken up by the crop, as a percentage of that applied) has been promoted (Zvomuya et al 2003;Arkoun et al 2012); however, the urease inhibitors themselves pass into roots and/or leaves, preventing natural ureic assimilation within plant tissues, allowing internalised urea to build to toxic levels (Krogmeier et al 1989). Furthermore, alterations of urea assimilation within root or leaf tissue mean that most of the urea provided fails to release the bound nitrogen that it contains; and the transcriptional profiles of genes involved in primary and secondary metabolism are altered, to the detriment of the plant (Zanin et al 2016).…”