Increased Nitrogen Uptake Research Articles

Winter and spring night-warming improve root extension and soil nitrogen supply to increase nitrogen uptake and utilization of winter wheat ( Triticum aestivum L.)

Abstract Elucidating the effects of asymmetric warming during winter and spring will help develop a feasible crop management strategy for climate change. Field experiments were conducted using the Yangmai-13 (vernal type) and Yannong-19 (semi-winter type) winter wheat cultivars to investigate the effects of night-warming during winter (warming by 1.47–1.53 °C from tillering to jointing), spring (warming by 1.68–1.77 °C from jointing to booting), and winter + spring (warming by 1.53–1.60 °C from tillering to booting) on plant growth and N utilization in 2014–2016. The results showed that the grain yield, N agronomic efficiency (NAE), and N recovery efficiency (NRE) of both cultivars were highly increased in response to night-warming, which were associated with enhanced dry matter and N accumulation, and winter + spring night-warming resulted in greater increases than winter night-warming and spring night-warming. Furthermore, the increase in pre-anthesis N accumulation was much higher than after anthesis, resulting in a greater increase in post-anthesis dry matter accumulation due to more leaf N distribution at anthesis to support photosynthetic production. Root growth characteristics (i.e., root length, surface area and volume, and root bleeding intensity) were significantly promoted, which favored plant N uptake. Soil urease and protease activity as well as the net N mineralization rate, which are involved in soil N supply capacity, were increased, whereas soil inorganic N content and apparent N surplus were clearly decreased, which indicated that plant N uptake capacity was highly improved in response to night-warming conditions. In conclusion, winter and spring night-warming improve pre-anthesis root growth and N uptake ability to promote plant growth, resulting in increased N utilization efficiency with reduced N fertilizer loss, and winter + spring night-warming has more advantages for N uptake and utilization of winter wheat.

Early sowing increases nitrogen uptake and yields of winter wheat grown with cattle slurry or mineral fertilizers

AbstractThe current study evaluated the effect of sowing date (early, mid-August or timely, mid-September) on two winter wheat (Triticum aestivum L.) cultivars (Hereford, Mariboss) with different rates of nitrogen (N) (0–225 kg total N/ha) applied as animal manure (AM; cattle slurry) or mineral fertilizers (N: phosphorus: potassium; NPK). Overwinter plant N uptake and soil mineral N content were determined during 2014/15, while harvest yields (grain, straw, N content) were determined during 2014/15 and 2015/16. Overwinter uptake of N was 14 kg N/ha higher in early than in timely-sown wheat. Despite very different yield levels in 2015 and 2016 harvests, the advantage of early sowing on grain yields was similar (1.1 and 0.9 t/ha); straw yield benefits were greater in 2015 (1.7 t/ha more) than in 2016 (0.4 t/ha more). In 2015 and 2016, N offtake was 35 and 17 kg N/ha higher in early than in timely-sown wheat, respectively. The mineral N fertilizer value of cattle slurry averaged 50%. Early sowing increased the apparent N recovery (ANR) for wheat regardless of nutrient source. However, ANR was substantially higher for NPK (82% in 2015; 52% in 2016) than for AM (39% in 2015; 27% in 2016). Performance of the two cultivars did not differ consistently with respect to the effect of early sowing on crop yield, N concentration and offtake, or ANR. Within the north-west European climatic region, moving the sowing time of winter wheat from mid-September to mid-August provides a significant yield and N offtake benefit.

Pengaruh Pupuk Hayati Endofitik Dengan Azolla Pinnata Terhadap Serapan N , N-Total Tanah, Dan Bobot Kering Tanaman Padi (Oryza Sativa L.) Pada Tanah Salin

Saline soil contain excessive NaCl content which inhibit plant growth and lead to nitrogen deficiency. Endophytic bacteria live inside the plant tissue and has the ability to fix nitrogen directly from the atmosphere, meanwhile Azolla pinnata can be used as organic ameliorant that able to increase the number of availability nitrogen for plant in soil, and improve the physical, chemical, and biological properties of soil. The aims of this experiment were to find out the treatment that cause highest nitrogen uptake by plant, total-N of soil, and dry weight of rice in saline soil. The experimental design was randomized block design with eight treatments and four repetitions. The results showed that the application of biofertilizer and ameliorant increased nitrogen uptake by plant and dry weight of rice in saline soil, but there was no significant effect on total-N of soil. This experiment suggested that endophytic bacteria biofertilizer and Azolla pinnata were effective to increase dry weight and nitrogen uptake of rice grown in soil with EC between 2 dS m-1 - 4 dS m-1.

Liming and straw retention interact to increase nitrogen uptake and grain yield in a double rice-cropping system

Liming and straw retention are often applied to increase yield in rice cropping systems on acidic soils. Although these practices affect soil fertility and rice growth through different mechanisms, it is still unclear whether or how these two management practices interact. Here we report on the first experiment to study the interaction between liming and straw management practices on rice yield. We conducted a two-year factorial field experiment to investigate the interactive effect of liming and straw retention on rice yield and nitrogen (N) uptake in a double rice-cropping system in subtropical China. We found that straw retention significantly interacted with liming to increase rice yields; without liming, straw retention increased yield by 4.2% on average, whereas with liming, straw retention increased yield by 11.6%. Straw retention also significantly interacted with liming to improve N uptake, with a stronger response for late rice compared to early rice. Liming and straw retention increased soil N availability and the activities of soil enzymes involved in both carbon and N cycling, suggesting increased organic matter decomposition and enhanced N mineralization rates. Across treatments, rice yields significantly correlated with soil N availability. Therefore, we conclude that in this short-term experiment, liming and straw retention interacted to increase rice yield, likely due to their effect on soil fertility and plant N uptake.

Alternate partial root-zone drip irrigation improves water\u2013 and nitrogen\u2013 use efficiencies of sweet-waxy maize with nitrogen fertigation

Alternate partial root–zone drip irrigation (ADI) or fertigation has favorable effect on crop water- and nitrogen- use efficiencies (WUE and NUE). However, the advantage of combined application of ADI and nitrogen fertigation on crop WUE and NUE remains unclear. A pot experiment was conducted to investigate the impact of three irrigation methods (CDI conventional drip irrigation (both halves of pot irrigated), ADI (both halves of pot alternatively irrigated) and FDI fixed partial root–zone drip irrigation (fixed half of pot irrigated)) and five nitrogen treatments (F0 no N supplied, F1-F4 0.2, 0.18, 0.16 and 0.14 g N per kg soil via fertigation) on sweet-waxy maize. Compared with CDI, ADI reduced water consumption by 19.9%, but increased water use efficiency based on dry seed yield (WUEs) by 32.3%, and also enhanced nitrogen apparent recovery fraction (Nrf) and nitrogen agronomic efficiency (NAE). F1-F4 augmented dry mass accumulation, dry seed yield and total nitrogen uptake if compared to F0. Moreover, F2-ADI had higher shoot and total dry masses, WUEs, total nitrogen uptake, Nrf and NAE. Thus ADI increased nitrogen uptake, WUE and NUE of sweet-waxy maize with nitrogen fertigation of 0.18 g N per kg soil in this study.

Environmental Impact for Applications of Neem Cake Coated Urea and Nano Iron Foliar on Rationalization of Chemical Nitrogen Fertilizers and Wheat Yield

Slow release fertilizer has become a new trend for saving chemical fertilizer consumption and to minimize environmental pollution. This study was aimed to use neem cake as a natural material for coating urea for improving fertilizer efficiency and reduce N-losses. Also to investigate the application of neem cake coated urea with or without foliar nano iron on wheat productivity. Neem cake coated urea and nano iron were prepared. Two experiments (incubation and field) were carried out. Incubation experiment was conducted using soil samples to study the efficiency of the use neem cake coated urea on NH4+ release under conditions of saturated and field capacity for nine weeks. A field experiments was carried out to study the effect of neem coated urea with or without nano iron as foliar spray on N-use efficiency, wheat yield, components and nitrate leaching. The results of incubation experiment showed that, the release of NH4+ was thehighest under saturated conditions as compared with field capacity. The release of NH4+ from neem coated urea was slow for a long period of time compared to uncoated urea. The data of the field experiment showed that the application of neem coated urea fertilizers led to a lower concentration of nitrate in drainage water. A highest increase in the grain yield of wheat was recorded by application of neem coated urea fertilizers with foliar nano iron compared to uncoated urea as a control. Results illustrated that controlled released urea fertilizer improved yield by 24% and enhanced N uptake up to 77% as compared to uncoated urea as control treatment. Applied of neem coated urea and nano iron foliar has increased nitrogen uptake and recovery efficiency of wheat. From the results obtained, it could be concluded that, the possibility of using neem coated urea as well as foliar spraying with nano iron for rationalize the use of nitrogen chemical fertilizers, thereby reducing the pollution as well as reducing the costs of agricultural production.

Some Aspects of Low Methylamine Partial Pressure Carbonitriding*

Abstract Low pressure carbonitriding is a case hardening process under development. At temperatures between 800 °C and 1050 °C and at total pressures below 50 mbar the carbon and nitrogen concentrations in the outer layer of steel parts are increased and the parts are subsequently hardened by quenching. As state of the art, ammonia is used as the nitrogen donor, in combination with a carbon donor gas, mainly acetylene or propane [1–3]. Other possible carbonitriding gases are not mentioned in recent literature with the exception of a Soviet Union patent [4], but no information on the application of this invention was found. At the Engler-Bunte-Institut of the Karlsruhe Institute of Technology, methylamine and dimethylamine were identified as potential carbonitriding gases, and their carbonitriding behavior was experimentally studied using a thermobalance. The experiments proved an increased nitrogen uptake of the steel samples in comparison to the state of the art. The carbon uptakes were in the same order of magnitude to a comparable process with acetylene. In addition to earlier published results for methylamine as the carbonitriding gas [5], this paper focuses on some operational and kinetic effects.

Five decades of selection for yield reduced root length density and increased nitrogen uptake per unit root length in Australian wheat varieties

Background and aims Given the worldwide effort to improve the nitrogen (N) economy of crops, it is critical to understand the mechanisms of improved N uptake which have resulted from selection pressure for grain yield in Australian wheat (Triticum aestivum L.). Changes in root system traits and N uptake were examined in nine Australian wheat varieties released between 1958 and 2007.

Combined Effect of Plant Density and Nitrogen Input on Grain Yield, Nitrogen Uptake and Utilization of Winter Wheat

Combined Effect of Plant Density and Nitrogen Input on Grain Yield, Nitrogen Uptake and Utilization of Winter Wheat The nitrogen input and plant density have significant effects on nitrogen uptake and utilization of winter wheat. The objective of this work was to optimize nitrogen input and plant density for higher nitrogen uptake and utilization while maintaining grain yield. Field experiments were performed during the 2011-2012 and 2012-2013 growing seasons using two cultivars under different nitrogen input rates (0,180 and 240 kg ha-1) and plant densities (120, 180 and 240 plants m-2 for Jimai 22 and 135, 270 and 405 plants m-2 for Tainong 18, respectively). The results showed that increasing plant density improved yield and increased nitrogen-use efficiency owing to the increased nitrogen uptake efficiency. The highest plant density at nitrogen input of 180 kg ha-1 obtained equivalent grain yield, and higher nitrogen uptake efficiency and nitrogen utilization efficiency compared with that at 240 kg nitrogen ha-1. Nitrogen-use efficiency positively correlated to nitrogen uptake efficiency at all nitrogen input rates. Negative relationship between nitrogen-use efficiency and nitrogen utilization efficiency was only found at nitrogen input of 240 kg ha-1, indicating that the low nitrogen utilization efficiency limited nitrogen-use efficiency increasing at high nitrogen input.. .

Interactions between water and nitrogen in Australian cropping systems: physiological, agronomic, economic, breeding and modelling perspectives

This paper reviews the interactions between water and nitrogen from physiological, agronomic, economic, breeding and modelling perspectives. Our primary focus is wheat; we consider forage crops, sorghum and legumes where relevant aspects of water–nitrogen interactions have been advanced. From a physiological perspective, we ask: How does nitrogen deficit influence the water economy of the crop? How does water deficit influence the nitrogen economy of the crop? How do combined water and nitrogen deficit affect crop growth and yield? We emphasise synergies, and the nitrogen-driven trade-off between the efficiency in the use of water and nitrogen. The concept of nitrogen–water co-limitation is discussed briefly. From agronomic and economic perspectives, the need to match supply of nitrogen and water is recognised, but this remains a challenge in dryland systems with uncertain rainfall. Under-fertilisation commonly causes gaps between actual and water-limited potential yield. We discuss risk aversion and the role of seasonal rainfall forecasts to manage risk. From a breeding perspective, we ask how selection for yield has changed crop traits relating to water and nitrogen. Changes in nitrogen traits are more common and profound than changes in water-related traits. Comparison of shifts in the wheat phenotype in Australia, UK, Argentina and Italy suggests that improving yield per unit nitrogen uptake is straightforward; it requires selection for yield and allowing grain protein concentration to drift unchecked. A more interesting proposition is to increase nitrogen uptake to match yield gains and conserve protein in grain. Increased stomatal conductance is a conspicuous response to selection for yield which partially conflicts with the perception that reduced conductance at high vapour pressure deficit is required to increase water- use efficiency; but high stomatal conductance at high vapour pressure deficit may be adaptive for thermal stress. From a modelling perspective, water and nitrogen are linked in multiple ways. In crops where water limits growth, reduced biomass reduces nitrogen demand. Reciprocally, nitrogen limitation during crop expansion reduces leaf area index and increases the soil evaporation : transpiration ratio. Water–nitrogen interactions are also captured in the water-driven uptake of nitrogen by mass flow and diffusion and in the water-driven processes of nitrogen in soil (e.g. mineralisation). The paper concludes with suggestions for future research on water-nitrogen interactions.

Plant traits related to nitrogen uptake influence plant-microbe competition.

Plant species are important drivers of soil microbial communities. However, how plant functional traits are shaping these communities has received less attention though linking plant and microbial traits is crucial for better understanding plant-microbe interactions. Our objective was to determine how plant-microbe interactions were affected by plant traits. Specifically we analyzed how interactions between plant species and microbes involved in nitrogen cycling were affected by plant traits related to 'nitrogen nutrition in interaction with soil nitrogen availability. Eleven plant species, selected along an oligotrophic-nitrophilic gradient, were grown individually in a nitrogen-poor soil with two levels of nitrate availability. Plant traits for both carbon and nitrogen nutrition were measured and the genetic structure and abundance of rhizosphere. microbial communities, in particular the ammonia oxidizer and nitrate reducer guilds, were analyzed. The structure of the bacterial community in the rhizosphere differed significantly between plant species and these differences depended on nitrogen availability. The results suggest that the rate of nitrogen uptake per unit of root biomass and per day is a key plant trait, explaining why the effect of nitrogen availability on the structure of the bacterial community depends on the plant species. We also showed that the abundance of nitrate reducing bacteria always decreased with increasing nitrogen uptake per unit of root biomass per day, indicating that there was competition for nitrate between plants and nitrate reducing bacteria. This study demonstrates that nitrate-reducing microorganisms may be adversely affected by plants with a high nitrogen uptake rate. Our work puts forward the role of traits related to nitrogen in plant-microbe interactions, whereas carbon is commonly considered as the main driver. It also suggests that plant traits related to ecophysiological processes, such as nitrogen uptake rates, are more relevant for understanding plant-microbe interactions than composite traits, such as nitrophily, which are related to a number of ecophysiological processes.

Effect of FYM, biofertilizers and zinc on nitrogen uptake by maize crop

A field experiment was conducted to study the effect of FYM, biofertilizers ( Azotobacter and VAM) and zinc on uptake of nitrogen by maize during two consecutive years of 2006-07 and 2007-08 at Instructional Farm, Rajasthan College of Agriculture, Maharana Pratap University of Agricultureand Technology, Udaipur. Application of FYM, biofertilizers and zinc significantly increased nitrogen uptake by maize. Combined use of FYM and biofertilizers significantly increased nitrogen uptake by maize and combined use of FYM and Zn also significantly increased the nitrogen uptake by maize.

Impacts of urea deep placement on nitrous oxide and nitric oxide emissions from rice fields in Bangladesh

Urea deep placement (UDP) increases nitrogen use efficiency (NUE) in lowland rice fields by reducing ammonia volatilization, surface runoff and increasing nitrogen uptake. However, its effects on N losses as nitrous oxide (N2O) and nitric oxide (NO) are not yet clear. We conducted field experiments at two locations of Bangladesh — Bangladesh Agricultural University (BAU) and Bangladesh Rice Research Institute (BRRI) — to determine the effects of UDP vs broadcast urea on N2O and NO emissions from rice fields.N2O and NO emissions were measured from three N fertilizer treatments (control [0kgN/ha], UDP, broadcast urea) using automated gas sampling and analysis system continuously for three rice growing seasons — Aus (May–Aug), Aman (Aug–Dec) and Boro (Jan–May). Urea was applied as 2–3 split application, while for UDP treatment, urea briquettes were deep placed (7–10cm depth) between 4 hills of rice at alternate rows to meet recommended N rates in a single application. Treatments were arranged in a randomized complete block design with three replications and N2O and NO measurements were done at every three-hour interval.N2O emissions were sporadic and event specific. Peaks in N2O emissions were observed after broadcast application of urea, during dry period and after re-flooding of the dry soil. For the rest of the time during the rice-growing season, emissions were very low to negligible. However, across the rice-growing seasons, UDP significantly (P<0.05) reduced N2O emissions compared with broadcast urea. Moreover, N2O emissions showed significant spatial and seasonal variations. They were higher during Boro season compared with Aus and Aman seasons and at BAU site than that of BRRI. Conversely, emissions between Aus and Aman seasons and between control and UDP treatments were similar. In contrast to N2O emissions, NO emissions were negligible and not affected by fertilizer treatment. However, significant spatial and seasonal variations were observed, with higher NO emissions at BRRI site compared with BAU and during Boro than that of Aus season.

Nitric oxide generated by nitrate reductase increases nitrogen uptake capacity by inducing lateral root formation and inorganic nitrogen uptake under partial nitrate nutrition in rice.

Increasing evidence shows that partial nitrate nutrition (PNN) can be attributed to improved plant growth and nitrogen-use efficiency (NUE) in rice. Nitric oxide (NO) is a signalling molecule involved in many physiological processes during plant development and nitrogen (N) assimilation. It remains unclear whether molecular NO improves NUE through PNN. Two rice cultivars (cvs Nanguang and Elio), with high and low NUE, respectively, were used in the analysis of NO production, nitrate reductase (NR) activity, lateral root (LR) density, and (15)N uptake under PNN, with or without NO production donor and inhibitors. PNN increased NO accumulation in cv. Nanguang possibly through the NIA2-dependent NR pathway. PNN-mediated NO increases contributed to LR initiation, (15)NH₄(+)/(15)NO₃(-) influx into the root, and levels of ammonium and nitrate transporters in cv. Nanguang but not cv. Elio. Further results revealed marked and specific induction of LR initiation and (15)NH₄(+)/(15)NO₃(-) influx into the roots of plants supplied with NH₄(+)+sodium nitroprusside (SNP) relative to those supplied with NH₄(+) alone, and considerable inhibition upon the application of cPTIO or tungstate (NR inhibitor) in addition to PNN, which is in agreement with the change in NO fluorescence in the two rice cultivars. The findings suggest that NO generated by the NR pathway plays a pivotal role in improving the N acquisition capacity by increasing LR initiation and the inorganic N uptake rate, which may represent a strategy for rice plants to adapt to a fluctuating nitrate supply and increase NUE.

A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean

Abstract. The impact of light and nutrients (such as silicate and iron) availability on nitrogen uptake and primary production vary seasonally and regionally in the Southern Ocean. The seasonal cycle of nitrogen uptake by phytoplankton in the Southern Ocean is not fully resolved over an annual scale due to the lack of winter in situ measurements. In this study, nitrate and ammonium uptake rates were measured using 15N tracers during a winter cruise in July 2012 and a summer cruise in February–March 2013. The winter cruise consisted of two legs: leg 1 extended from Cape Town to the ice margin along the GoodHope line and leg 2 stretched from the ice margin to Marion Island. The summer cruise was mostly focused on the subantarctic zone of the Atlantic sector. In winter, nitrogen uptake rates were measured at 55 and 1% of the surface photosynthetically active radiation (sPAR). The summer uptake rates were measured at four light depths corresponding to 55, 30, 10 and 3% sPAR. The integrated nitrate uptake rates during the winter cruise ranged from 0.17 to 5.20 mmol N m−2 d−1 (average 1.14 mmol N m−2 d−1) while the ammonium uptake rates ranged from 0.60 to 32.86 mmol N m−2 d−1 (average 6.73 mmol N m−2 d−1). During the summer cruise, the mean-integrated nitrate uptake rate was 0.20 mmol N m−2 d−1 with a range between 0.10 and 0.38 mmol N m−2 d−1. The integrated ammonium uptake rate averaged 4.39 mmol N m−2 d−1 and ranged from 1.12 to 9.05 mmol N m−2 d−1. The factors controlling nitrogen uptake in winter and summer were investigated. During the winter cruise, it was found that the different nitrogen uptake regimes were not separated by the fronts of the Antarctic Circumpolar Current (ACC). Light (in terms of day length) and ammonium concentration had the most influence on the nitrogen uptake. In the summer, increases in the mixed layer depth (MLD) resulted in increased nitrogen uptake rates. This suggests that the increases in the MLD could be alleviating nutrient limitations experienced by the phytoplankton at the end of summer.

Mycorrhiza symbiosis increases the surface for sunlight capture in Medicago truncatula for better photosynthetic production.

Arbuscular mycorrhizal (AM) fungi play a prominent role in plant nutrition by supplying mineral nutrients, particularly inorganic phosphate (Pi), and also constitute an important carbon sink. AM stimulates plant growth and development, but the underlying mechanisms are not well understood. In this study, Medicago truncatula plants were grown with Rhizophagus irregularis BEG141 inoculum (AM), mock inoculum (control) or with Pi fertilization. We hypothesized that AM stimulates plant growth through either modifications of leaf anatomy or photosynthetic activity per leaf area. We investigated whether these effects are shared with Pi fertilization, and also assessed the relationship between levels of AM colonization and these effects. We found that increased Pi supply by either mycorrhization or fertilization led to improved shoot growth associated with increased nitrogen uptake and carbon assimilation. Both mycorrhized and Pi-fertilized plants had more and longer branches with larger and thicker leaves than the control plants, resulting in an increased photosynthetically active area. AM-specific effects were earlier appearance of the first growth axes and increased number of chloroplasts per cell section, since they were not induced by Pi fertilization. Photosynthetic activity per leaf area remained the same regardless of type of treatment. In conclusion, the increase in growth of mycorrhized and Pi-fertilized Medicago truncatula plants is linked to an increase in the surface for sunlight capture, hence increasing their photosynthetic production, rather than to an increase in the photosynthetic activity per leaf area.

Effect of γ-PGA coated urea on N-release rate and tomato growth

The anionic polymer γ-polyglutamic acid (γ-PGA) was used to coat urea and slow its dissolution. Three types of slow release urea (SRU) fertilizers (polymer coated urea with pore constriction, polymer coated urea with enzyme inhibitor and polymer coated urea with pore constriction and enzyme inhibitor) were prepared and tested for the N-release rate. After using SRU, the effect on the tomato growth was analyzed. The extracts of SRU were analyzed for NH3/NH4 +-N and NO3 −-N. The N-release rate was used to determine the optimum ratio of ingredients. The results show that the three types of SRU met the dissolution rate standards recommended by the Committee of European Normalization. γ-PGA SRU increased the chlorophyll content of tomato (flowering stage) by an average of 100% compared with that grew in untreated urea. The results from soil analysis (0-60 cm in tomato pots) indicate that the content of NH3/NH4 +-N in SRU-treated pots was 25%–61% higher than that in soil from urea-treated pots during the growing period, while the content of NO3 −-N was nearly 50% lower after the tomato had been harvested. Newly formulated SRU fertilizer increases nitrogen uptake and reduces loss of applied nitrogen. Plant growth is enhanced, a valuable resource is conserved, and the aquatic environment benefits from decreased level of nitrate in agricultural run-off.

Nitrogen use by winter wheat and changes in soil nitrate nitrogen levels with supplemental irrigation based on measurement of moisture content in various soil layers

In northern China, water sources are one of most limiting factors for agricultural development, particularly for winter wheat. Optimizing supplemental irrigation (SI) to achieve the ideal soil moisture content and nutrient uptake by plants is therefore highly important in this region. The present study investigated how various SI regimes affect nitrogen use in winter wheat and alter soil nitrate nitrogen (NO3N) content under field conditions. The soil relative water content (SRWC) of the 0–20cm (D20), 0–40cm (D40) and 0–60cm (D60) soil layers was raised to 70% by supplemental irrigation at jointing and anthesis, and a non-irrigated, rain-fed (R-F) condition served as the control. The highest grain yields of 9648.4kgha−1 in 2011–2012 and 10,032.2kgha−1 in 2012–2013 were obtained in D40, which had higher nitrogen use efficiency (NUE) than R-F, D20 and D60. NUE was positively correlated with nitrogen translocation efficiency (NtE) and nitrogen fertilizer productivity (NfP) but not with nitrogen uptake efficiency (NupE). These results indicated that optimizing the SI regime improved NUE primarily by increasing nitrogen uptake and translocation and thereby raising NtE and NfP. The soil NO3N content was lower in D40 than in R-F, D20 and D60 in the 0–200cm soil layers, indicating that NO3N leaching was the lowest in D40. Thus, the optimal SI regime, which consisted of irrigating SRWC in the 0–40cm soil layer to 70% at jointing and anthesis, reduced NO3N leaching and increased NUE and NfP in winter wheat.

The ecophysiological determinants of nitrophily in annual weed species

SummaryPlant nitrophily plays a key role in weed community assembly. To date, the determinants of the success of nitrophilic weeds and of the decline of oligotrophic weeds in intensive cropping systems are not fully understood. This study investigated which ecophysiological traits related to carbon and N nutrition explain plant nitrophily in field annual species. Twelve species (consisting of monocotyledonous and dicotyledonous species, as well as crops and weeds) covering the oligotrophic‐nitrophilic continuum were grown in a glasshouse experiment at two contrasted conditions of soil‐nitrogen supply. From measured plant growth variables, ecophysiological traits were calculated to account for plant nutritional strategies. Globally, whatever the soil‐nitrogen supply, increased nitrophily was associated with a decreased allocation of carbon to root vs. shoot. At high soil‐nitrogen only, increased nitrophily was also generally associated with an increased nitrogen uptake activity per unit of root biomass, pointing to a trade‐off between oligotrophic species with a preferential carbon investment in root structure and nitrophilic species with a preferential carbon investment in root activity. Beyond these global trends explaining nitrophily, results also show that different strategies are possible for plant species to be considered as nitrophilic. This study provides evidence on why adjusting N fertilisation in quantity, in space (with nitrogen fertiliser placement on the row) or in time can be useful strategies to manage the most nitrophilic weeds, which are also the most problematic in intensive cropping systems.

Heterotrimeric G proteins regulate nitrogen-use efficiency in rice.

The drive toward more sustainable agriculture has raised the profile of crop plant nutrient-use efficiency. Here we show that a major rice nitrogen-use efficiency quantitative trait locus (qNGR9) is synonymous with the previously identified gene DEP1 (DENSE AND ERECT PANICLES 1). The different DEP1 alleles confer different nitrogen responses, and genetic diversity analysis suggests that DEP1 has been subjected to artificial selection during Oryza sativa spp. japonica rice domestication. The plants carrying the dominant dep1-1 allele exhibit nitrogen-insensitive vegetative growth coupled with increased nitrogen uptake and assimilation, resulting in improved harvest index and grain yield at moderate levels of nitrogen fertilization. The DEP1 protein interacts in vivo with both the Gα (RGA1) and Gβ (RGB1) subunits, and reduced RGA1 or enhanced RGB1 activity inhibits nitrogen responses. We conclude that the plant G protein complex regulates nitrogen signaling and modulation of heterotrimeric G protein activity provides a strategy for environmentally sustainable increases in rice grain yield.