Differences In Nitrogen Use Efficiency Research Articles

Organic substitution accumulates more nitrogen in soil while maintaining unchanged nitrogen use efficiency in rice‐fava bean rotation system

AbstractOrganic substitution management (OSM) is critical for soil conservation and nitrogen efficiency. However, integrated assessment of soil quality and crop productivity under paddy‐upland rotation systems after OSM introduction is still lacking. Here, soil nitrogen‐related properties and crop nitrogen use efficiency (NUE) were evaluated in 2018, 2019, and 2020, based on a long‐term rice‐fava bean rotation experiment started in 2015. In comparison to chemical fertilization, OSM increased total soil nitrogen (TN) and available nitrogen (AN) by 13.1% and 13.8%, respectively, during the rice season, and by 16.3% and 15.9% during the fava bean season. However, NUE, nitrogen recovery efficiency (NRE), and nitrogen agronomic efficiency (NAE) all showed season‐specific responses to OSM. OSM decreased NUE, NRE, and NAE by 18.2%, 37.5%, and 26.2% in the rice season but increased by 8.0%, 231.0%, and 184.1% in the fava bean season. From the rotation system scale, there were no significant differences in NUE and nitrogen surplus between the treatments. We suggest that the differences in soil conditions and crop requirements between seasons play significant roles in the response of nitrogen accumulation and nitrogen utilization to OSM. Based on these differences, OSM achieves inter‐seasonal synergy in soil N pools and crop uptake, and results in yield stabilization and soil nitrogen accumulation. Because of its high capacity for improving soil quality while ensuring no yield reduction, OSM has the potential to curb regional soil degradation in paddy‐upland rotation areas where there is increasing demand for food and chemical fertilizers are currently abused.

Effects of climate and soil properties on regional differences in nitrogen use efficiency and reactive nitrogen losses in rice

Nitrogen (N) use efficiency worldwide varies greatly due to climate, agronomic, and soil factors. However, the information on individual effects of these factors on N use efficiency is crucial but has remained scanty. Given that climate cannot be regulated, understanding the relative importance of fertilizer and soil variations on regional differences in N use efficiency is critical. Here, we constructed a database of 302 studies from 1986 to 2020 in East and Northeast China to determine the effects of climate, soil properties, and fertilizer N (FN) rate on variations in N use efficiency (agronomic efficiency (AE), apparent recovery efficiency (RE), physiological efficiency (PE), N harvest index, partial factor productivity), N surplus, grain N content, and reactive N (Nr) losses (N2O emissions, NH3 volatilization, Nr leaching, and runoff). Rice yield was comparable between two regions under farmers’ N practices, yet the N input was considerably higher in East China. All indices of N use efficiency, except RE, are higher in Northeast China. Differences in AE were dominated by the ability of the plant to mobilize N (PE) rather than N uptake (RE), FN, or Nr loss. Soil properties and FN related to optimizable N management accounted for 29% (RE), 39% (PE), and 43% (Nr losses) of the variations, of which key factors as pH showed a negative effect while available N (AN) correlated positively to the N use efficiency. To realize high N use efficiency, pivotal effects of pH, AN, and FN on N use efficiency under certain climate zone should be considered.

Clonal differences in nitrogen use efficiency and macro-nutrient uptake in young clonal cocoa (Theobroma cacao L.) seedlings from Indonesia

Nitrogen (N) is one of the most required nutrients in cocoa production. Unlike in many other crops, there is limited knowledge on genotypic variation in nitrogen use efficiency (NUE) in clonal cocoa. We therefore evaluated the effect of nitrogen application on cocoa NUE in 10 clonal cocoa scions that were top-grafted on 4-month old rootstock seedlings of cocoa clone MCC 02. Grafted seedlings received either 0 or 2.3 g/plant of N at the beginning of the experiment, which lasted for five months and was arranged in a nursery of the Indonesian Coffee and Cocoa Research Institute (ICCRI) in Jember, Indonesia. A factorial randomized block design was used with four replications. We found that clones significantly affected rootstock stem diameter and dry biomass both in roots and shoots. Nitrogen application decreased rootstock stem diameter and root biomass but increased shoot-root ratio. Following the N application, we observed significantly higher N concentration and uptake both in roots and shoots. This higher N concentration and uptake contributed to significantly lower NUE in both roots and shoots. We did not observe clonal differences in N concentration, uptake, NUE in either roots or shoots and ANR (Apparent Nitrogen Recovery). Nitrogen application influenced P, K, Mg, and Ca uptake in both roots and shoots. There was a clonal effect on P, K and Mg uptake and on P and Mg use efficiency in both roots and shoots. This implies that the studied clones vary in their P and Mg nutrient use efficiency but not in NUE.

Comprehensive evaluation of nitrogen use efficiency of different Lycium barbarum L. cultivars under nitrogen stress

Nitrogen (N) deficiency is a common problem for Lycium barbarum L. (goji) production in arid and semi-arid areas of northwestern of China. The development of new nitrogen-efficient goji cultivars under low nitrogen conditions is an important way to solve this problem. In the present study, morphological and nutrient-based parameters of Ningqi 1 (A), 1402 (B), Ningqi 7 (C), 1401 (D), and Ning1Y (E) were comprehensively evaluated under different nitrogen levels in the greenhouse. Finally, we concluded that Ningqi 1 (A) was high and Ning1Y (E) was low in nitrogen use efficiency under nitrogen stress. Difference of glutamate synthase activity in the root may be the reason for the difference in nitrogen use efficiency between Ningqi 1 (A) and Ning1Y (E). This work provides a reliable and comprehensive method to assess nitrogen utilization under low nitrogen conditions in goji and reveals possible physiological difference mechanisms.

Efficiency of nitrogen uptake and utilization in sugar beet genotypes

The nitrogen use efficiency (NUE) is composed of the nitrogen uptake (NUpE) and nitrogen utilization efficiency (NUtE). The contribution of these components to overall NUE of sugar beet genotypes is unknown, as well as the reasons for genotypic variation. In 2018 and 2019, 6 genotypes were studied in field trials at three N levels (65, 120, 240 kg N ha−1). The trials revealed only minor genotypic differences in N uptake and N uptake efficiency, but distinct genotypic differences in N utilization efficiency and NUE. The interaction between genotype and environment was negligible, i.e. differences between genotypes in NUE were independent of N management, and there was no genotypic adaptation to low N availability. Differences in NUE resulted rather from differences in sugar yield potential. This demonstrates that selection to high sugar yield potential will also promote NUE. It was concluded that a high sugar yield potential resulted from an assimilate partitioning towards high sugar yield, in combination with a low leaf mass to total dry mass ratio. There was evidence that lower leaf mass resulted in higher levels of leaf N content. If a higher leaf N content could be used to identify high yielding genotypes is unclear, but it was concluded that a high leaf mass is not a prerequisite for high sugar yields.

Transcriptome Analysis of Two Near-Isogenic Lines with Different NUE under Normal Nitrogen Conditions in Wheat.

Simple SummaryHigh nitrogen use efficiency (NUE) in wheat (Triticum aestivum L.) is the key to ensure high yield and reduce pollution. Understanding the physiological and molecular changes that regulate NUE is important for the breeding of high-NUE wheat varieties. Carbon and nitrogen metabolism are the basic metabolic pathways in plants. It becomes important to reveal the underlying molecular mechanisms related to carbon and nitrogen metabolism, which may be helpful to improve NUE. In this paper, two wheat near-isogenic lines (NILs) with contrasting NUE were performed RNA-Sequencing (RNA-Seq) to identify candidate genes associated with carbon/nitrogen metabolism under normal nitrogen conditions. Our research may provide new insights into the comprehensive understanding of the molecular mechanism underlying NUE.Nitrogen (N) is an essential nutrient element for crop productivity. Unfortunately, the nitrogen use efficiency (NUE) of crop plants gradually decreases with the increase of the N application rate. Nevertheless, little has been known about the molecular mechanisms of differences in NUE among genotypes of wheat. In this study, we used RNA-Sequencing (RNA-Seq) to compare the transcriptome profiling of flag leaves at the stage of anthesis in wheat NILs (1Y, high-NUE, and 1W, low-NUE) under normal nitrogen conditions (300 kg N ha−1, corresponding to 1.6 g N pot−1). We identified 7023 DEGs (4738 upregulated and 2285 downregulated) in the comparison between lines 1Y and 1W. The responses of 1Y and 1W to normal N differed in the transcriptional regulatory mechanisms. Several genes belonging to the GS and GOGAT gene families were upregulated in 1Y compared with 1W, and the enhanced carbon metabolism might lead 1Y to produce more C skeletons, metabolic energy, and reductants for nitrogen metabolism. A subset of transcription factors (TFs) family members, such as ERF, WRKY, NAC, and MYB, were also identified. Collectively, these identified candidate genes provided new information for a further understanding of the genotypic difference in NUE.

Efficiency of nitrogen use by wheat depending on genotype and previous crop

ABSTRACT The efficiency of nitrogen use by wheat crop depends on genetic and environmental stimuli. The aim of this study was to evaluate the efficiency of nitrogen use by wheat crop, through biomass, productivity and grain quality indicators, as a function of the genotype and previous harvest, in Southern Brazil cereal cultivation systems. The experiments were conducted in soybean/wheat and maize/wheat systems during 2015, 2016, and 2017 in Augusto Pestana, RS, Brazil. The experimental design was a randomized block with four repetitions, following a 5 × 4 factorial scheme, referring to five wheat cultivars (Quartzo, TBIO Sinuelo, TBIO Sintonia, TEC 10 and TEC Vigore) and four nitrogen doses (0, 60, 120 and 180 kg ha-1) applied as a topdressing during the phenological stage of the expanded third leaf, stage 13. There were genetic differences in nitrogen use efficiency, for the productivity (yield and biomass) and quality of wheat. However, these genetic differences were influenced by the carbon:nitrogen ratios of the previous crop. Quartzo and TBIO Sinuelo had the greatest nitrogen use efficiency for grain yield, TBIO Sinuelo had the greatest nitrogen use efficiency for biomass production and Quartzo had the greatest nitrogen use efficiency for grain quality with expectation of 3 Mg ha-1, regardless of the succession system, in the joint analysis of agricultural years.

Co-Overexpression of OsNAR2.1 and OsNRT2.3a Increased Agronomic Nitrogen Use Efficiency in Transgenic Rice Plants.

The NO3 - transporter plays an important role in rice nitrogen acquisition and nitrogen-use efficiency. Our previous studies have shown that the high affinity systems for nitrate uptake in rice is mediated by a two-component NRT2/NAR2 transport system. In this study, transgenic plants were successful developed by overexpression of OsNAR2.1 alone, OsNRT2.3a alone and co-overexpression of OsNAR2.1 and OsNRT2.3a. Our field experiments indicated that transgenic lines expressing p35S:OsNAR2.1 or p35S:OsNAR2.1-p35S:OsNRT2.3a constructs exhibited increased grain yields of approximately 14.1% and 24.6% compared with wild-type (cv. Wuyunjing 7, WT) plants, and the agricultural nitrogen use efficiency increased by 15.8% and 28.6%, respectively. Compared with WT, the 15N influx in roots of p35S:OsNAR2.1 and p35S: OsNAR2.1-p35S:OsNRT2.3a lines increased 18.9%‑27.8% in response to 0.2 mM, 2.5 mM 15NO3 –, and 1.25 mM 15NH4 15NO3, while there was no significant difference between p35S:OsNAR2.1 and p35S:OsNAR2.1-p35S:OsNRT2.3a lines; only the 15N distribution ratio of shoot to root for p35S:OsNAR2.1-p35S:OsNRT2.3a lines increased significantly. However, there were no significant differences in nitrogen use efficiency, 15N influx in roots and the yield between the p35S:NRT2.3a transgenic lines and WT. This study indicated that co-overexpression of OsNAR2.1 and OsNRT2.3a could increase rice yield and nitrogen use efficiency.

Effects of water application uniformity using a center pivot on winter wheat yield, water and nitrogen use efficiency in the North China Plain

In recent years, the use of fertigation technology with center pivot irrigation systems has increased rapidly in the North China Plain (NCP). The combined effects of water and nitrogen application uniformity on the grain yield, water use efficiency (WUE) and nitrogen use efficiency (NUE) have become a research hotspot. In this study, a two-year field experiment was conducted during the winter wheat growing season in 2016–2018 to evaluate the water application uniformity of a center pivot with two low pressure sprinklers (the R3000 sprinklers were installed in the first span, the corresponding treatment was RS; the D3000 sprinklers were installed in the second span, the corresponding treatment was DS) and a P85A impact sprinkler as the end gun (the corresponding treatment was EG), and to analyze its effects on grain yield, WUE and NUE. The results showed that the water application uniformity coefficients of R3000, D3000 and P85A along the radial direction of the pivot (CUH) were 87.5, 79.5 and 65%, respectively. While the uniformity coefficients along the traveling direction of the pivot (CUC) were all higher than 85%. The effects of water application uniformity of the R3000 and D3000 sprinklers on grain yield were not significant (P>0.05); however, the average grain yield of EG was significantly lower (P<0.05) than those of RS and DS, by 9.4 and 11.1% during two growing seasons, respectively. The coefficients of variation (CV) of the grain yield had a negative correlation with the uniformity coefficient. The CV of WUE was more strongly affected by the water application uniformity, compared with the WUE value, among the three treatments. The NUE of RS was higher than those of DS and EG by about 6.1 and 4.8%, respectively, but there were no significant differences in NUE among the three treatments during the two growing seasons. Although the CUH of the D3000 sprinklers was lower than that of the R3000, it had only limited effects on the grain yield, WUE and NUE. However, the cost of D3000 sprinklers is lower than that of R3000 sprinklers. Therefore, the D3000 sprinklers are recommended for winter wheat irrigation and fertigation in the NCP.

Rootstock x Environment Interactions on Nitrogen-Use Efficiency in Grafted Tomato Plants at Different Phenological Stages

The use of grafting techniques for horticultural crops increases plant tolerance to various abiotic and biotic stresses. Tomato production under greenhouse conditions relies on plants grafted onto vigorous rootstocks because they sustain crops for longer periods. Growers under Mediterranean conditions usually grow crops in passive greenhouses during the summer and winter season, to provide fresh products throughout the year. No information is available with regard to the effect of the environment on nitrogen-use efficiency (NUE) in tomato plants grafted onto rootstocks with different vigor. In the present study, NUE, along with its components—uptake (NUpE) and utilization (NUtE) efficiencies—were evaluated in tomato plants grafted onto two interspecific rootstocks, conferring medium (“King Kong”) or high (“Kaiser”) vigor to the plants. The evaluations were carried out during the vegetative and reproductive stage in plants subjected to different environmental conditions resulting in different plant growth rates. The grafting treatments did not affect NUE, NUpE or NUtE in young plants, but at the reproductive stage, differences were found during the summer season (high N demand) where the vigorous rootstock increased NUpE from 55%, in non-grafted plants, to 94%, with the consequent differences in NUE. During the winter crop, no differences in NUE were found between the vigorous rootstock and non-grafted plants, but the less vigorous (cold-tolerant) rootstock enhanced NUpE. Significant positive relationships were found between plant growth rate and both NUE and NUpE, while NUtE decreased with increasing growth rate.

High-efficient utilization and uptake of N contribute to higher NUE of 'Qinguan' apple under drought and N-deficient conditions compared with 'Honeycrisp'.

Drought and nitrogen (N) deficiency are common factors that limit apple production in the Loess Plateau region of China. Different apple cultivars respond to drought and low N differently; however, the mechanism that underlies the difference in nitrogen-use efficiency (NUE) under drought conditions is not well understood. In this study, by comparing the physiological responses of two apple (Malus domestica Borkh.) cultivars with contrasting NUE, 'Qinguan' (higher NUE) and 'Honeycrisp' (lower NUE), under low N and drought conditions, we discovered that, 'Qinguan' had larger stomatal apertures, higher chlorophyll fluorescence levels, more active N metabolism and antioxidant enzymes, higher abscisic acid and auxin concentrations, larger root size and more efficient N uptake mediated by higher expression of MdNRT2.4 in rootstock than that of 'Honeycrisp'. Additionally, we experimentally confirmed that MdNRT2.4 enhanced low N and osmotic stress tolerance in Arabidopsis when being overexpressed. Taken together, our findings shed light on the mechanism that underlies the difference in NUE of apple under drought and N-deficient conditionss and provide MdNRT2.4 as a candidate gene for future genetic engineering.

Nitrogen utilization of potato genotypes and expression analysis of genes controlling nitrogen assimilation

IntroductionSignificant differences in nitrogen use efficiency (NUE) were detected previously among potato cultivars. Exploration of the genetic background may facilitate the breeding of cultivars with highly effective nitrogen use.MethodsExpression of NUE genes was analyzed at three different N-supply levels in five potato genotypes. Correlations of NUE gene expressions and agronomical parameters with such indices as the nitrogen uptake efficiency, nitrogen utilization efficiency, NUE, and harvest indices were analyzed.ResultsThe correlations between expression level of the nitrate-reductase, nitrite-reductase, ammonium transporter, and asparagine synthase genes and different agronomically important parameters were detected.DiscussionOur results contribute to more rational, genotype-dependent nitrogen use in potato production and have relevance in breeding of new cultivars with better nitrogen utilization, as well as in production of seed potato.

Comparison of ammonia emissions related to nitrogen use efficiency of livestock production in Europe

The increasing global demand for food and the environmental effects of reactive nitrogen losses in the food production chain, increase the need for efficient use of nitrogen (N). Of N harvested in agricultural plant products, 80% is used to feed livestock. Because the largest atmospheric loss of reactive nitrogen from livestock production systems is ammonia (NH3), the focus of this paper is on N lost as NH3 during the production of animal protein. The focus of this paper is to understand the key factors explaining differences in Nitrogen Use Efficiency (NUE) of animal production among various European countries. Therefore we developed a conceptual framework to describe the NUE defined as the amount of animal-protein N per N in feed and NH3N losses in the production of milk, beef, pork, chicken meat and eggs in The Netherlands, Switzerland, United Kingdom, Germany, Austria and Denmark. The framework describes how manure management and animal-related parameters (feed, metabolism) relate to NH3 emissions and NUE. The results showed that the animal product with the lowest NUE had the largest NH3 emissions and vice versa, which agrees with the reciprocal relationship between NUE and NH3 within the conceptual framework. Across animal products for the countries considered, about 20% of the N in feed is lost as NH3. The significant smallest proportion (12%) of NH3N per unit of Nfeed is from chicken production. The proportions for other products are 17%, 19%, 20% and 22% for milk, pork, eggs and beef respectively. These differences were not significantly different due to the differences among countries. For all countries, NUE was lowest for beef and highest for chicken. The production of 1 kg N in beef required about 5 kg N in feed, of which 1 kg N was lost as NH3N. For the production of 1 kg N in chicken meat, 2 kg N in feed was required and 0.2 kg was lost as NH3. The production of 1 kg N in milk required 4 kg N in feed with 0.6 kg NH3N loss, the same as pork and eggs, but those needed 3 and 3.5 kg N in feed per kg N in product respectively. Except for beef, the differences among these European countries were mainly caused by differences in manure management practices and their emission factors, rather than by animal-related factors including feed and digestibility influencing the excreted amount of ammoniacal N (TAN). For beef, both aspects caused important differences. Based on the results, we encourage the expression of N losses as per N in feed or per N in product, in addition to per animal place, when comparing production efficiency and NUE. We consider that disaggregating emission factors into a diet/animal effect and a manure management effect would improve the basis for comparing national NH3 emission inventories.

Identifying oilseed rape varieties with high yield and low nitrogen fertiliser requirement

Reducing the fertiliser nitrogen (N) requirement of oilseed rape (Brassica napus L.) whilst maintaining yield will be beneficial for both growers and the environment. The aim of this paper was to identify differences in fertiliser N requirement between varieties and investigate simple in-field methods to rapidly identify varieties that can maintain high yield whilst requiring lower optimal N rates (‘HYLO’ varieties) to aid breeding for lower N fertiliser requirement. Four field experiments were conducted in the UK during seasons 2011-12 or 2012-13 on a range of soil types. Each experiment included 21 elite open pollinated and hybrid varieties. Each variety was grown at seven levels of N fertiliser ranging from zero to super-optimal (340 or 400 kg N/ha). Measurements of seed yield and seed oil content were combined to calculate gross output yield, i.e. seed yield adjusted for oil content. Linear plus exponential yield response curves were fitted to calculate the economically optimum N rate (Nopt) of each variety and the associated nitrogen use efficiency (NUE) was calculated at the Nopt. Across varieties, gross output yield responses to optimum N fertiliser, compared with yields at nil N rates, were significant, ranging from 1.3 to 2.7 t/ha between sites. Nopt ranged from 117 to 286 kg N/ha between sites giving experimental average yields at Nopt (Yopt) of 3.0 to 4.6 t/ha. Varietal yield ranges at Nopt within each experiment ranged from 0.6 to 1.7 t/ha, and there was a positive trend for yield to increase with date of variety introduction by 0.24 t/ha per decade. Significant variety x N fertiliser rate interactions were measured for gross output yield in two out of four experiments and significant varietal differences in Nopt were measured in one experiment ranging from 195 kg N/ha to 296 kg N/ha. There was no correlation between Nopt and Yopt indicating that improving varietal yield potential will not necessarily increase N requirement. Significant varietal differences in NUE were measured at Nopt ranging from 13.5 to 15.9 kg of gross output yield per kg of N supply from soil residues and fertiliser. Seed with low N and high oil content, and high biomass harvest index could be useful indicators of high NUE. However, no single trait correlated consistently with varietal variation in NUE. The yield difference between sub- and super-optimal N rates was positively correlated with Nopt. Further research is required to develop new experimental approaches for measuring yield at more than one N level on small experimental plot areas and to investigate a wider range of genotypes.

Varietal differences in nitrogen use efficiency among spring wheat varieties in Montana

Most agronomic studies have focused on increasing nitrogen use efficiency (NUE) through the management of nutrients in the soil (4Rs), but little is known about the effect of cropping systems on NUE. This study examines the differences in NUE among five popular spring wheat varieties as related to soil N fertility and two Montana cropping systems, crop–fallow and continuous cropping. Earn 0.5 CEUs in Crop Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/510.

Yield, biomass composition, and N use efficiency during establishment of four Miscanthus × giganteus genotypes as influenced by N management

Few studies have examined N management strategies to accelerate Miscanthus establishment. Our objectives were: (i) determine differences in biomass yield among various M. × giganteus genotypes as influenced by N management during establishment; (ii) quantify the impact of genotype and N management on biomass composition; and (iii) determine how M. × giganteus genotype and N management influence nitrogen use efficiency (NUE). Four M. × giganteus genotypes were planted near Schochoh, KY and Lafayette, IN in 2010. A two-year total N application of 150 kg ha−1 was applied using various combinations of 50, 75, and 100 kg ha−1 y−1. Control N rates included 0 and 150 kg ha−1 each year. Yield, composition, and NUE of the MS and IL clones were similar. Two-year cumulative yields of Nagara were higher than the other genotypes in KY, and the IL clone in IN. There was no response of yield to N on the silt loam soil in KY, whereas high biomass yields were achieved with 50 kg ha−1 y−1 of N on the sandy loam soil in IN. Yields of plots provided high N in Season 1 were similar to unfertilized control plots in Season 2 suggesting little N carryover from Season 1 to 2. Biomass fiber concentrations were not influenced by N-fertilization, but high leaf retention of the Nagara lines reduced biomass cellulose and lignin concentrations. Site-specific genotypic differences in NUE were observed. Annual N applications of 50 kg ha−1 is recommended to enhanced Miscanthus yield during establishment on the coarse-textured soils.

Variation in nitrogen use efficiencies on Dutch dairy farms.

On dairy farms, the input of nutrients including nitrogen is higher than the output in products such as milk and meat. This causes losses of nitrogen to the environment. One of the indicators for the losses of nitrogen is the nitrogen use efficiency. In the Dutch Minerals Policy Monitoring Program (LMM), many data on nutrients of a few hundred farms are collected which can be processed by the instrument Annual Nutrient Cycle Assessment (ANCA, in Dutch: Kringloopwijzer) in order to provide nitrogen use efficiencies. After dividing the dairy farms (available in the LMM program) according to soil type and in different classes for milk production ha(-1) , it is shown that considerable differences in nitrogen use efficiency exist between farms on the same soil type and with the same level of milk production ha(-1) . This offers opportunities for improvement of the nitrogen use efficiency on many dairy farms. Benchmarking will be a useful first step in this process.

Cultivar Differences in Nitrogen Use Efficiency of Field Grown Rice Plant at Different Levels of Nitrogen Fertilizer

Cultivar Differences in Nitrogen Use Efficiency of Field Grown Rice Plant at Different Levels of Nitrogen Fertilizer

Genotypic variation in N uptake and assimilation estimated by 15N tracing in water deficit-stressed Brassica napus

To investigate varietal difference in nitrogen-use efficiency and water-deficit tolerance among eight Brassica napus cultivars, direct quantification of the amount of newly absorbed N and its incorporation to amino acids and proteins was performed by tracing 15N for 7 days of well-watered (control) and water-deficit conditions. Water deficit leads to reduction of leaf water potential (Ψw), biomass, chlorophyll content and nitrogen concentration with cultivar variation. The amount of newly absorbed N for the given time significantly decreased in water-deficit plants, which can be classified into three groups; high N uptake [Saturnin, Tamra (>6.5mgplant−1)], medium [Colosse, Sparta, Capitol, Akela (4–6mgplant−1)], and low [Youngsan, Pollen (<4mgplant−1)]. Water deficit significantly decreased overall the amount of N assimilated into amino acids and proteins. Significant cultivar variation for the inhibition of de novo protein synthesis caused by water deficit was found, being the highest in Pollen (−42.2% compared to control) versus the lowest in Saturnin (−31.2%). By an estimation of nitrogen-use efficiency based on N uptake (NUpE) and N assimilation (NUaE), Saturnin and Tamra could be identified as N-efficient genotypes, while Youngsan and Pollen as inefficient ones. It was found that cultivar variation in NUpE and NUaE was significantly associated with the change in Ψw as affected by water deficit. The present study suggests that the Ψw can be used as an easy and sensitive determinant predictive for assessing NUpE which is a preliminary factor for NUaE under water deficit.

The effect of soil tillage system on the nitrogen uptake, grain yield and nitrogen use efficiency of spring barley in a cool Atlantic climate

SUMMARYField experiments were conducted between 2009 and 2011 in Ireland to compare the effects of soil tillage systems on the grain yield, nitrogen use efficiency (NUE) and nitrogen (N) uptake patterns of spring barley (Hordeum vulgare) in a cool Atlantic climate. The four tillage treatments comprised conventional tillage in spring (CT), reduced tillage in autumn (RT A), reduced tillage in spring (RT S) and reduced tillage in autumn and spring (RT A+S). Each tillage system was evaluated with five levels of fertilizer N (0, 75, 105, 135 and 165 kg N/ha). Grain yield varied between years but CT had a significantly higher mean yield over the three years than the RT systems. There was no significant difference between the three RT systems. Tillage system had no significant effect on the grain yield response to fertilizer N. As a result of the higher yields achieved, the CT system had a higher NUE than the RT systems at all N rates. There was no significant difference in NUE between the three RT systems. Conventional tillage had significantly higher nitrogen uptake efficiency (NUpE) than RT A and a significantly higher nitrogen utilization efficiency (NUtE) than all three RT systems. Crop N uptake followed a similar pattern each year. Large amounts of N were accumulated during the vegetative growth stages while N was lost after anthesis. Increased N rates had a positive effect on N uptake in the early growth stages but tended to promote N loss later in the season. The CT system had the highest N uptake in the initial growth stages but its rate of uptake diminished at a faster rate than the RT systems as the season progressed. Tillage system had an inconsistent effect on crop N content during the later growth stages. On the basis of these results it is concluded that the use of non-inversion tillage systems for spring barley establishment in a cool oceanic climate remains challenging and in certain conditions may result in a reduction in NUE and lower and more variable grain yields than conventional plough-based systems.