Effects of increasing salinity and 15N-labelled urea levels on growth, N uptake, and water use efficiency of young tomato plants

Abstract

A greenhouse experiment was conducted to investigate the response of tomato plants (Lycopersicon lycopersicum L.) to salinity and to determine the interactive effects of salinity and nitrogen fertilisation on yield, nitrogen uptake, water use efficiency (WUE), and root-zone salinity during early plant growth. Furthermore, the effects of salinity and N fertilisation were evaluated by measurement of carbon isotope discrimination (Δ). Tomato plants were grown in pots filled with 8 kg (dry weight equivalent) of Krumbach sandy loam. Salinity treatments were imposed by irrigation water containing Na, Ca, and Mg salts and having electrical conductivity of 0, 3, 6, 9, and 12 dS/m at 25�C. 15N-labelled urea (10 atom % excess) was also applied at 0, 80, 160, and 240 mg N/kg soil. Increasing salinity reduced plant growth; fresh and dry weights of shoots and roots decreased significantly, except for the non-fertilised plants. The maximum growth reduction in shoots occurred due to salinity–N fertilisation relationships at 12 dS/m (59.4% reduction compared with 0 dS/m in 160 mg N/kg). Root growth was less affected than shoots. Vegetative growth and N content increased with increasing nitrogen treatment. However, salinity generally reduced N uptake by plants. Δ was negatively correlated with WUE at all salinity levels in young tomato plants. Similar correlations were also obtained between WUE and Δ at various N treatments; the result suggests that Δ is a useful tool for assessing stress conditions. Smaller Δ values were obtained when salinity or N level increased. Increasing N fertiliser increased WUE in plants, whereas increasing salinity increased WUE at 3 dS/m and decreased WUE to some extent at other salinity levels. Electrical conductivity of the root-zone increased due to increasing salinity and time, whereas pH decreased. It was concluded that the early stage of development was a salt sensitive period for tomato plants.

Effects of water, salt and nitrogen stress on sunflower (Helianthus annuus L.) at different growth stages

“…This result further demonstrated that the reasonable nitrogen application rate (135 kg N ha -1 ) could alleviate the interactive effects on post-anthesis reproductive growth under both water deficit and saline soil conditions. Similar phenomenon was reported by Xue et al, (2007) and Kütük et al, (2004), who suggested that increasing the nitrogen fertilizer supply to a certain extent could attenuate the interactive effects of water-salt stress on sunflower and tomato development, respectively.…”

Effect of Fertilizer and Fixed Nitrogen on the Water Use Efficiency of Genge (Astragalus sinicus L.)

“…There are many reports associating improvement of WUE with N supply (Heitholt, 1989; Pieterse et al, 1997Brück et al, 2001; Brueck andSenbayram, 2009;Kütük et al, 2004). However, in this experiment, the increase in supply of fertilizer N and the accompanying increase in N%, showed no relation to WUE, which remained static (Fig.…”

“…Past many researches show that an increase in N supply accompanies an increase in WUE (Heitholt, 1989;Pieterse et al, 1997;Brück et al, 2001;Kütük et al, 2004;Brueck and Senbayram, 2009). However, WUE is lower in nodulated plants with a high concentration of internal N (Unkovich and Pate, 2000;Sumi et al, 2005).…”

Continuous Nitrogen Application Differentially Affects Growth, Yield, and Nitrogen Use Efficiency of Leymus chinensis in Two Saline–Sodic Soils of Northeastern China

“…Some researchers have evaluated the effects of N application on tomato (Lycopersicon esculentum Mill.) (Kutuk et al, 2004) and cotton (Gossypium hirsutum L.) (Chen et al, 2010;Dong et al, 2012) under salinity stress, and found that N application improved yield (Chen et al, 2010). The data from 3 yr of field trials indicated an almost linear relationship between N application rates and yields of L. chinensis in both MSSL and SSSL conditions (Tables 3 and 5).…”