Nitrogen Fertilization Regimes Research Articles

Soil dynamics of Cr(VI) and responses of Portulaca oleracea L. grown in a Cr(VI)-spiked soil under different nitrogen fertilization regimes.

The reduction potential of the highly toxic Cr(VI) to the inert Cr(III) in analkaline soil was studied during a 50-day experiment with Portulaca oleracea L. grown in pots. We aimed at assessing whether our test species can be a phytoremediation candidate for Cr(VI)-contaminated soils. We measured the Cr(VI) reduction rate in soil, determined the Cr(VI) and Cr(III) concentrations in aerial and root P. oleracea tissues, and calculated the transfer coefficient (TC = metal in plant over metal in soil) and the translocation factor (TF = metal in aerial biomass over metal in roots) in order to assess Cr(VI) uptake and distribution in plant tissues, while we also studied the effect of added nitrogen in the studied parameters. We added five different Cr(VI) levels (from the unamended T-0 to the treatment of T-4 = 150 mg Cr(VI) kg-1 soil) and also had two N levels (equivalent to 0 and 200 kg ha-1). The results indicated that Cr in plant tissues was mainly found in its reduced form (Cr(III)) and only a minor fraction of Cr was detected in its oxidized form (Cr(VI)), with only 1.04% of plant Cr being hexavalent at T-4 with no added N and 1.30% at T-4 with added N. The main remediation mechanism was found to be that of the naturally occurring Cr(VI) reduction that effectively produced Cr(III), followed by the uptake of Cr(VI) from our test plants (at T-4 with no N, 58% of soil added Cr(VI) was reduced and 0.1% absorbed, while at T-4 with added N, 63% was reduced and only 0.4% absorbed by plant). We also found that Cr(VI) in P. oleracea tissues was mainly found in roots and relatively low Cr(VI) concentrations were found in the above-ground tissues. We concluded that P. oleracea is a tolerant plant species, especially if assisted with a sufficient level of N fertilization, although it failed to approach the threshold of being categorized as an accumulator species. However, as this is a rather preliminary experiment, before reaching more conclusive suggestions about P. oleracea as a potential phytoremediation species, further investigation is necessary in order to verify the gained results with naturally contaminated soils with Cr under field conditions.

Comparative response of some tropical maize hybrid and their parental varieties to low and high nitrogen regime

The study was carried to investigate the differential response of some maize hybrids and their open pollinated parents to low and high nitrogen soil condition. Ten open-pollinated varieties were crossed in a partial diallel fashion to generate 45 F1 hybrids during the 2011 cropping season at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. The 45 F1 hybrids and the ten parents were evaluated in four environments at Mokwa and Zaria in August, 2012 under high and low N conditions with two different levels of nitrogen application (30kgha-1 and 90kgha-1) respectively.Hybrids recorded shorter plant height under the two different nitrogen fertilizer conditions compare with open pollinated parents. Thus the hybrids are better for mechanical harvesting. Taller ear height was observed among the hybrids compare with the open pollinated parents; rate of stem and root lodging were consequently higher among the hybrids. Hybrid had better husk cover under both nitrogen fertilizer regime; that's they will be less susceptible to insect and animal attack.Mean difference of ear per plant between the maize hybrids and open pollinated parents was not significant. Significant difference was observed between maize hybrids and their parents for grain yield under low and high fertilizer regimes. That the hybrids had higher grain yield under both nitrogen fertilizer regime; indicates the tolerance of maize hybrid to low-N condition than the parental varieties. Low-N environment seemed to favor shorter day to silk for maize hybrid, however, high nitrogen soil condition appeared to increase day to silk. It is an evidence that flowering and consequently maturity time is delayed under favorable nitrogen soil environments.Days to 50% pollen shed are significantly different among the maize hybrids and their parents. The maize hybrids attained day to pollen earlier than the parents under both fertilizer regime. It is an indication that setting of maize grain occur earlier among hybrids than their open pollinated parents.

Performance of apical rooted cuttings of potato grown in Mollic Andosols under different nitrogen fertilization and irrigation regimes

Potato productivity (Solanum tuberosum L) is generally influenced by several factors, including water and nitrogen (N), and potato requirement for these factors varies depending on the soil type and potato variety. This research aimed to determine the performance of apical rooted cuttings of potato grown in Mollic Andosols under different nitrogen fertilization and irrigation regimes. The treatments comprised 4 irrigation regimes of 100%, 85%, 75% and 50% of the crop evapotranspiration (ETC), where ETC100% was irrigated based on water depletion in the root zone two days after full irrigation, and 4 nitrogen rates of 0 (N0), 60 (N1), 90 (N2) and 130 kg.ha−1 (N3) applied in splits at 10 (40%), 30 (40%) and 50 (20%) days after planting. The results revealed that the water demand for apical rooted cuttings of potato (ETa) was on average 201.4, 302.1, 342.4 and 402.8 mm under ETC50%, ETC75%, ETC85% and ETC100%, respectively. It was observed that plant height and number of branches significantly (P < 0.001) varied under different N rates with the highest plant height (92.67 cm) and number of branches per potato plant (17) achieved when applying N3. Potato grown under full irrigation (ETC100%) with N3 produced the highest total potato tuber yield (58.28 t.ha−1) and marketable tuber yield (54.21 t.ha−1). The number of tubers per plant statistically reduced as the N deficit increased, with the maximum tuber number, 23, achieved under N3. It was observed that a significant Pearson correlation (r = 0.7∗∗∗) existed between tuber number and total tuber yield. The maximum harvest index (HI), 57.12 %, was obtained under ETC50% with N3, while the highest tuber dry matter, 30 %, was observed under N3. To achieve a high tuber yield from apical rooted cuttings of potato in Mollic Andosols, this study recommends an irrigation regime of ETC100% and a nitrogen rate of 130 kg.ha−1.

Comparative Response of Some Tropical Maize Hybrid and Their Parental Varieties to Low and High Nitrogen Regime

The study was carried to investigate the differential response of some maize hybrids and their open pollinated parents to low and high nitrogen soil condition. Hybrids recorded shorter plant height under the two different nitrogen fertilizer conditions compare with open pollinated parents. Thus the hybrids are better for mechanical harvesting. Taller ear height was observed among the hybrids compare with the open pollinated parents; rate of stem and root lodging were consequently higher among the hybrids. Hybrid had better husk cover under both nitrogen fertilizer regime; that’s they will be less susceptible to insect and animal attack. Mean difference of ear per plant between the maize hybrids and open pollinated parents was not significant. Significant difference was observed between maize hybrids and their parents for grain yield under low and high fertilizer regimes. That the hybrids had higher grain yield under both nitrogen fertilizer regime; indicates the tolerance of maize hybrid to low-N condition than the parental varieties. Low-N environment seemed to favor shorter day to silk for maize hybrid, however, high nitrogen soil condition appeared to increase day to silk. It is an evidence that flowering and consequently maturity time is delayed under favorable nitrogen soil environments. Days to 50% pollen shed are significantly different among the maize hybrids and their parents. The maize hybrids attained day to pollen earlier than the parents under both fertilizer regime. It is an indication that setting of maize grain occur earlier among hybrids than their open pollinated parents

Estimations of Water Use Efficiency in Winter Wheat Based on Multi-Angle Remote Sensing.

Real-time non-destructive monitoring of water use efficiency (WUE) is important for screening high-yielding high-efficiency varieties and determining the rational allocation of water resources in winter wheat production. Compared with vertical observation angles, multi-angle remote sensing provides more information on mid to lower parts of the wheat canopy, thereby improving estimates of physical and chemical indicators of the entire canopy. In this study, multi-angle spectral reflectance and the WUE of the wheat canopy were obtained at different growth stages based on field experiments carried out across 4 years using three wheat varieties under different water and nitrogen fertilizer regimes. Using appropriate spectral parameters and sensitive observation angles, the quantitative relationships with wheat WUE were determined. The results revealed that backward observation angles were better than forward angles, while the common spectral parameters Lo and NDDAig were found to be closely related to WUE, although with increasing WUE, both parameters tended to become saturated. Using this data, we constructed a double-ratio vegetation index (NDDAig/FWBI), which we named the water efficiency index (WEI), reducing the impact of different test factors on the WUE monitoring model. As a result, we were able to create a unified monitoring model within an angle range of −20–10°. The equation fitting determination coefficient (R2) and root mean square error (RMSE) of the model were 0.623 and 0.406, respectively, while an independent experiment carried out to test the monitoring models confirmed that the model based on the new index was optimal, with R2, RMSE, and relative error (RE) values of 0.685, 0.473, and 11.847%, respectively. These findings suggest that the WEI is more sensitive to WUE changes than common spectral parameters, while also allowing wide-angle adaptation, which has important implications in parameter design and the configuration of satellite remote sensing and UAV sensors.

Effects of whole‐tree harvesting at thinning and subsequent compensatory nutrient additions on carbon sequestration and soil acidification in a boreal forest

AbstractResidues from forest harvesting operations may be utilized as a renewable energy source. However, the sustainability of this practice has been questioned due to the losses of nutrients and exchangeable base cations, which may impair the forest's carbon sequestration capacity and lead to soil acidification. We report the 18 year response of biomass growth, soil carbon stock and soil chemistry to whole‐tree harvest at thinning and associated compensatory measures in a Pinus sylvestris forest in northern Sweden. The whole‐tree harvest at thinning was combined with nutrient additions to compensate for the nutrient loss caused by extracting the residues. Four main treatments, stem‐only thinning, whole‐tree thinning, whole‐tree thinning with one‐time nitrogen fertilization and whole‐tree thinning with repeated nitrogen fertilization every third year were applied, with plots split for wood‐ash treatment. Eighteen years after the treatments, whole‐tree thinning that had removed 3.0 ± 0.2 Mg C/ha in residues had no effect on forest growth, soil carbon and nitrogen stocks or soil chemistry. Both nitrogen fertilization regimes increased biomass growth, but neither one resulted in a significant increase in soil carbon stock. Wood‐ash addition increased soil pH and exchangeable base cations, but did not affect carbon stock in biomass or soil. Our long‐term data suggest that utilizing harvesting residues for biofuel feedstocks is appropriate in this type of forest. Hence, any nitrogen and wood‐ash additions appear unnecessary as compensatory measures for the removal of harvesting residues, but nitrogen can be applied to increase forest growth following thinning.

Coordinating Postanthesis Carbon and Nitrogen Metabolism of Hybrid Rice through Different Irrigation and Nitrogen Regimes

We sought to explore the role of postanthesis carbon and nitrogen (C-N) metabolism of hybrid rice in increasing yield and nitrogen utilization efficiency (NUE). We used the 13C and 15N dual-isotope tracer method and physiological/biochemical analysis and established different irrigation and nitrogen fertilization (W-N) regimes to investigate the relationship of C-N metabolism characteristics, yield, and NUE. The results showed that W-N regimes had significant effects on postanthesis absorption and translocation of N and photosynthate, yield and NUE. Aerobic irrigation combined with the N fertilization regime 30% base, 30% tillering, 40% booting was the best W-N coupling regime for rice yield and NUE increase. The regime enhanced flag leaf photosynthesis rate and the activities of ribulose 1,5-diphosphate carboxylase/oxygenase (RuBPCase), glutamine synthetase (GS), and other key enzymes of C-N metabolism, and improved the total accumulations of photoassimilates (0.97–21.57 mg 13C plant−1) and N (1.55–23.36 mg 15N plant−1), respectively. Correlation analysis showed that, under the W-N interaction, C-N metabolism enzymes promoted the positive synergistic effect between 13C and 15N accumulation in panicles (r = 0.825). In addition, the change in C/N ratio can be used as an indicator of the simultaneous improvement in yield and NUE in hybrid rice.

How Do Soil Bacterial Diversity and Community Composition Respond under Recommended and Conventional Nitrogen Fertilization Regimes?

Shifts in soil bacterial diversity and community composition are suggested to be induced by elevated input of nitrogen (N) fertilization with implications for soil quality, and consequently production. In this study, we evaluated the impacts of recommended fertilization (RF) and conventional fertilization (CF) on soil chemical properties, crop yield, bacterial diversity, and community composition from two long-term experiments conducted in fluvo-aquic soil and black soil of China. Each site comprised of four treatments, i.e., RF N−, RF N+, CF N−, CF N+. No N fertilization was indicated by N− and N fertilization was indicated by N+. Across both sites, N fertilization significantly increased crop yield compared with no N fertilization and RF successfully enhanced crop yield over CF. Interestingly, the RF maintained bacterial diversity, while CF depressed bacterial diversity in the two soils. Microbial taxa performing important ecological roles such as order Rhodospirillales and Bacillales were significantly enhanced in the RF approach, while Rhizobiales declined under CF. Furthermore, the results of partial least square path modeling revealed that soil available phosphorus (AP) negatively affected bacterial diversity while it positively affected bacterial community structure in fluvo-aquic soils. In contrast, soil pH was positively linked with both bacterial diversity and community structure in black soil. Overall, our study demonstrated that RF is an environmentally friendly approach which not only maintained above ground plant productivity, but also preserved belowground microbial populations and important soil variables regulating bacterial communities varied in different soil types.

Does nitrogen fertilization impact nonstructural carbohydrate storage in evergreen Podocarpus macrophyllus saplings?

Nonstructural carbon (NSC), which represents the relationship between the carbon source and carbon sink, is an important factor that reflects the functions and performance of a tree. However, little is known regarding the time-series responses of NSC storage in evergreen species to different nitrogen (N) fertilization regimes. This study, which was based on a pot experiment, examined the response of the NSC (soluble sugars and starch) storage to different N addition intensities [light N addition (LN): 6.5 g N m−2 a−1; moderate N addition (MN): 13.0 g N m−2 a−1; and heavy N addition (HN): 26.0 g N m−2 a−1)] in saplings of the evergreen species Podocarpus macrophyllus. Our results showed that the net photosynthetic rate (Pn) under MN was significantly higher than that under LN, but was comparable to that under HN. Moreover, saplings subject to MN had a significant higher leaf biomass than that to LN and HN. These results indicated that the C supply via photosynthesis under MN was greater than that under LN and HN. The NSCs reserve under MN was considerable with that under LN, which suggested that saplings in MN group consumed higher and stored lower properties of NSCs than those in LN group. However, saplings under HN stored higher properties of NSCs than those under MN considering that no difference in NSCs pools was found between the two treatments. The leaf N concentrations were found in the increasing sequence of LN < MN < HN, whilst the leaf chlorophyll concentration under HN was obviously lower than that under MN. The growth rate under MN was higher than that under LN and HN. We concluded that the NSCs allocation between consumption and reserve in P. macrophyllus saplings depended on soil N availability, and an excessive N addition to soil favors the storage rather than the consumption of NSCs by plants.

Farm-scale carbon and nitrogen fluxes in pastoral dairy production systems using different nitrogen fertilizer regimes

The nitrogen (N) fertilizer application rate (kg ha−1 year−1) in pastoral dairy systems affects the flow of N through the soil, plant and animal pools of the system. With better understanding of the magnitude of these pools and their fluxes, dairy systems could be managed to improve N use efficiency, therefore reducing losses to the environment. A study with three levels of N fertilizer, 0 (N0), 150 (N150) and 300 (N300) kg N ha−1 year−1, was conducted in the Canterbury region of New Zealand from 1 June 2017 till 31 May 2018. Farm measurements, e.g. pasture and milk production, were used to calibrate three different farm-scale models, DairyNZ’s Whole Farm Model, DairyMod, and Overseer®. The models were used to extrapolate periodic farm measurements to predictions of carbon (C) and N pools and fluxes on an annual basis. Pasture and milk production per hectare increased from N0 to N300 by 70 and 58%, respectively. There was a concomitant increase in farm-gate N surplus (input–output) of 43%, resulting in predicted increases in N leaching and greenhouse gas emissions of 72 and 67%, respectively. By increasing N fertilizer from 0 to 300 kg N ha−1 year−1, 53% more feed N flowed through the dairy herd with surplus N deposited as urinary N increasing by 49%. Plant uptake and soil immobilization increased by 58 and 343%, respectively, but not enough to avoid substantial increases in leaching and emission losses. Carbon flux through the soil system increased through increased litter and faecal deposition, but with very little C sequestration because of accelerated microbial respiration rates.

Impact of irrigation and fertilization regimes on greenhouse gas emissions from soil of mulching cultivated maize (Zea mays L.) field in the upper reaches of Yellow River, China

Greenhouse gas emissions from agricultural soil are strongly affected by the field practices including fertilization, irrigation and cultivation model. Understanding the mechanism of greenhouse gas emissions from soil and their impact factors is essential for cleaner agricultural production and global greenhouse gas mitigation. This paper investigated greenhouse gas emissions from soil of mulching cultivated maize (Zea mays L.) field under different irrigation and fertilization regimes. Border and drip irrigation with different schedules were implemented in the upper reaches of Yellow River, China. Border irrigation included three different irrigation depths (180, 315 and 450 mm), and drip irrigation was controlled by a tensiometer and triggered by three different matric potentials (−15, −25 and −35 kPa). Three nitrogen fertilizer levels (350, 250 and 150 kg ha−1) were applied for the drip irrigation triggered by the matric potential of −25 kPa. Soil acted as a sink of CH4 in the semiarid site regardless of irrigation and nitrogen fertilization regimes. Irrigation scheduling had no significant influence on CO2 emissions, but the irrigation method did have. Cumulative CO2 emissions increased by 24.7% for drip irrigation compared with border irrigation at the same water and nitrogen fertilizer levels. Cumulative CO2 emissions for the high nitrogen fertilizer treatment (350 kg ha−1) increased by 19.3% in comparison with the medium and low levels under drip irrigation. N2O emissions were positively related to the irrigation depth under both drip and border irrigation. Cumulative N2O emissions reduced by 23.5% for drip irrigation compared with border irrigation at the same water and nitrogen fertilizer levels. N2O emissions increased with the increase in nitrogen fertilizer application under drip irrigation. Drip irrigation with high frequency (−15 kPa) and medium nitrogen fertilization (250 kg ha−1) obtained the best economic and environmental performance through comprehensive evaluation of the yield, water and fertilizer productivity, global warming potential, greenhouse gas intensity and net ecosystem economic budget. The findings can provide an opportunity for greenhouse gas mitigation without crop yield reduction following the proper irrigation and fertilization regimes in the semiarid region.

Innovative water-saving ground cover rice production system increases yield with slight reduction in grain quality

Ground cover rice production system (GCRPS) is known to increase grain yield and reduce irrigation water and greenhouse gas emission. However, whether this innovative technology affects commercial and nutritional rice quality remains unknown. Thus, a three-year field experiment was conducted to compare three production systems: traditional paddy (Paddy) and GCRPS under two soil moisture conditions, namely, saturated and 80% of soil water-holding capacity combined with three nitrogen fertilizer regimes. We analyzed the grain-milling quality (brown rice rate, milled rice rate and head rice recovery), the appearance quality (chalky rice rate and grain size), eating quality (amylose concentration) and nutritional quality (protein and 15 amino acids concentration). Results showed that compared with Paddy, the average rice grain yield, water and nitrogen use efficiency were significantly higher in GCRPS. The milling quality was improved in GCRPS, whereas the appearance quality decreased. Amylose concentration was 7.6% higher in saturated GCRPS than in Paddy. Moreover, protein concentration was 11.5%–13.1% lower in GCRPS than in Paddy and total amino acid concentration was reduced by 6.9%, whereas protein and total amino acid yield were significantly improved. Meanwhile, the concentrations of six essential amino acids were similar to those in Paddy, whereas non-essential amino acid concentration decreased in GCRPS. Overall, our findings showed that suitable N management practices for GCRPS are to be developed to further enhance the protein and amino acid concentrations.

Nitrogen Fertilization Reduces Nitrogen Fixation Activity of Diverse Diazotrophs in Switchgrass Roots

The use of synthetic nitrogen fertilizers to grow biofuel crops adds to the economic and environmental costs of biomass production. Biological nitrogen fixation provides an alternative, eco-friendly source of nitrogen for leguminous plants and some nonlegumes. With the objective of characterizing and eventually harnessing nitrogen-fixing bacteria in switchgrass roots, we assayed nitrogenase activity and surveyed nifH-expressing bacteria in roots of switchgrass grown under agricultural conditions. Plants were cultivated at two separate locations in Oklahoma in different soil types for 5 years with three nitrogen fertilizer regimes (0, 90, and 180 kg of N ha−1 year−1). Nitrogenase activity associated with roots cleaned of soil was found to be highest in plants grown with no N fertilizer and lowest or not detectable for plants grown at the highest level of N fertilizer. A total of 454 abundant nifH operational taxonomic units (OTUs) were identified in the switchgrass roots. Diversity analysis of active nifH-expressing bacteria showed that the most common orders were Burkholderiales (171 OTUs), Desulfovibrionales (55 OTUs), and Rhizobiales (44 OTUs). OTUs belonging to Azonexus, Pseudacidovorax, Desulfovibrio, Dechloromonas, and Bradyrhizobium were enriched in roots of plants grown under low nitrogen conditions. Analysis of significant OTUs showed distinct nifH-expressing microbial communities at the two field locations, as well as a unique community in roots of unfertilized soil at Frederick that exhibited the highest rates of nitrogen fixation. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

An optimized model for simulating grain-filling of maize and regulating nitrogen application rates under different film mulching and nitrogen fertilizer regimes on the Loess Plateau, China

Grain-filling is a key stage allowing for the achievement of high grain yield. The ridge-furrow film mulching (RFFM) farming system has been widely adopted as a water saving and yield-improving planting pattern on the Loess Plateau of China. However, there is no convenient and effective model to understand the mechanism of maize grain-filling and effective nitrogen (N) management to obtain high grain yield under RFFM and N fertilizer. A two-year (2017–2018) field experiment was conducted on summer maize under RFFM (biodegradable film mulching (BM) and PE film mulching (PM)) and nitrogen fertilizer (0 (N0), 90 (N1), 180 (N2) and 270 (N3) kg N ha−1). The results showed that the 100-kernel dry weight was successfully simulated by the proposed model. After optimizing parameters, the model not only achieved minimum input requirements, but also successfully regulated N application. Moreover, characteristic parameters of grain-filling were significantly affected by the interaction of RFFM and N. N was beneficial for the improvement of the final 100-kernel dry weight (a) and grain-filling rate (Vmax, V¯) and was more improved under BM. The N1 with PM treatment reached the maximum grain-filling rate (Vmax) earlier. The maximum grain-filling rate (Vmax) and average rate of grain-filling (V¯) of PM was more sensitive to high N than BM. Parameters of the gradual-growing period were significantly affected by RFFM or N, but the interaction between RFFM and N had extremely significant effects on parameters of the fast-growing and slow-growing periods. For BM, N could improve the rate of three periods of grain-filling, and the N2 treatment was the best in the fast-growing and slow-growing periods. For PM, N could improve the rate of the gradual-growing period. According to the optimized model, the optimal nitrogen application rate of BM and PM was 205 kg ha−1 and 196 kg ha−1, respectively. Based on this optimized model, we could better understand the grain-filling process and achieve the appropriate nitrogen application rate.

Nitrogen Fertilization Regime for “Koisomeshi”, a New Rice Cultivar for Use in the Food–Service Industry

近年，精米販売量に占める業務用米の割合が増加しているが，業務用米においては多収と一定程度の品質の両立が求められるため，主食用とは異なる栽培管理が必要となる．本研究では，良食味・多収で業務利用に適した水稲新品種「恋初めし」での最適な窒素施肥体系を検討するため，生育前半の施肥量3水準（3，6，9 g m–2）と穂肥3水準（0，3，6 g m–2）を組み合わせた9処理の施肥試験を2017年と2018年に計3作期実施した．精玄米重は，3作期共通して穂肥が3または6 g m–2の条件で多収となり，その多収の要因としては，施肥量の増量による籾数の増加が関与していると考えられた．一方，外観品質は総窒素施肥量が多いほど低下し，特に穂肥の影響が大きかった．これらの結果から，「恋初めし」においては，生育前半施肥量6 g m–2，穂肥量3 g m–2が収量および品質の両面から最適な窒素施肥体系と判断された．また，外観品質の作期間差が大きく，高温および寡照条件で整粒歩合が低くなったことから，適切な作期の選択による外観品質の向上も重要と考えられた．

SOME MAIZE LEAF GROWTH TRAITS AS INFLUENCED BY SOME INTEGRATED FERTILIZATION REGIMES

A field experiment was conducted at the summer season of 2017, and then repeated at the summer season of 2018 in Agricultural Research Station. Faculty of Agric., Zigzag Univ., Sharkia Governorate, Egypt. The study investigated the impact of eleven nitrogen and five phosphorus fertilization regimes on some leaf traits 70 days after sowing (DAS) of maize cultivar single hybrid 168. Results showed that, 120kg N/fad., from different sources i.e., chemical fertilizer, compost and biofertilizers were effectless on number of leaves/plant at 70 days after sowing (DAS) of both seasons and their combined analysis. Number of leaves either under or above the ear of mono eared maize plant were not affected due to applying different nitrogen fertilization regimes studied. Leaf area/maize plant was significantly affected in the first season only. The largest leaf erea/plant (4254.22 cm2/plant) was obtained in the first season, with the appliance of the integrated N fertilization regime (90 kg N from chemical fertilizer +30 kg N from compost). Area of leaves under ear resulted from the integrated fertilization regime (cerealine + 60 kg chemical N+ 60 kg N from compost) was larger than that in the control treatment by 30.94% based on combined results. Regarding to the area of leaves above the ear, results of the 1st season displayed that area of leaves above the ear were at par in treatments N2, N3, N4, N5 and N6. Application of either 120kg chemical fertilizer (N2) or 90 kg chemical N +30 kg N from compost (N3) was conjucated with larger values of leaf area index comparably with other regimes. According to combined analysis, ear leaf area ranged from 481.87 cm2 in control treatment to 625.89 cm2 in the integrated nitrogen fertilization regimes comprised of cerealine + 60 kg chemical N/fad. + 60 kgN from compost. From the results of combined analysis, it could be noted that tassel leaf area ranged between 150.99 to 217.87 cm2 under biofertilization (N11) and the integrated fertilization regimes (N8)in the same order. Insignificant phosphorus fertilization effect under study on maize leaf traits studied at 70DAS, was recorded in both seasons and the combined analysis.

Effects of ozone on the growth and yield of rice (Oryza sativa L.) under different nitrogen fertilization regimes.

To examine whether the sensitivity of growth and yield of rice (Oryza sativa L.) to ozone (O3) varies under different nitrogen (N) fertilization conditions, rice cultivar 'Koshihikari' was exposed to O3 under either standard N (SN) fertilization or no N (NN) fertilization. The rice plants were subjected to three gas treatments (charcoal-filtered air (CF) and O3 at 1.0 (1.0×O3) and 1.5 (1.5×O3) times the ambient concentration) in combination with two conditions of N fertilization. At five time points throughout the growth period, plant samples were collected to measure the leaf area and dry mass of each plant organ. At the final harvest, yield, yield components, and harvest index were measured. There was a significant interactive effect of O3 and N on leaf, stem, root, and whole-plant dry mass at the final harvest. The dry mass of each plant organ and the whole-plant dry mass of rice plants grown in 1.5×O3 were significantly lower than those in the plants grown in CF and 1.0×O3 under SN, whereas there were no significant differences in the dry mass among the three gas treatments under NN. Brown rice yield was significantly reduced by the exposure to O3 under SN, but not under NN. Relative yield loss rate based on the AOT40 (accumulated exposure over a threshold of 40nmolmol-1) was pronounced under SN, whereas relative yield was almost unchanged at different AOT40 levels under NN. We concluded that the sensitivity of growth and yield of rice to O3 is dependent on N levels in the soil; the exposure to ambient levels of O3 has a negative effect on rice under SN, but not under NN.

Leaf mineral content govern microbial community structure in the phyllosphere of spinach (Spinacia oleracea) and rocket (Diplotaxis tenuifolia)

The plant microbiome is an important factor for plant health and productivity. While the impact of nitrogen (N) availability for plant growth and development is well established, its influence on the microbial phyllosphere community structure is unknown. We hypothesize that nitrogen impacts the growth and abundance of several microorganisms on the leaf surface. The bacterial and fungal communities of baby leaf spinach (Spinacia oleracea), and rocket (Diplotaxis tenuifolia) were investigated in a field trial for two years in a commercial setting. Nitrogen fertilizer was tested in four doses (basic nitrogen, basic + suboptimal, basic + commercial, basic + excess) with six replicates in each. Culture-independent (Illumina sequencing) and culture-dependent (viable count and identification of bacterial isolates) community studies were combined with monitoring of plant physiology and site weather conditions. This study found that alpha diversity of bacterial communities decreased in response to increasing nitrogen fertilizer dose, whereas viable counts showed no differences. Correspondingly, fungal communities of the spinach phyllosphere showed a decreasing pattern, whereas the decreasing diversity of fungal communities of rocket was not significant. Plant species and effects of annual variations on microbiome structure were observed for bacterial and fungal communities on both spinach and rocket. This study provides novel insights on the impact of nitrogen fertilizer regime on a nutrient scarce habitat, the phyllosphere.

Optimum applications of nitrogen fertilizer and water regime for wheat (Triticum aestivum L.) using 15N tracer technique under Mediterranean Environment

Optimum applications of nitrogen fertilizer and water regime for wheat (Triticum aestivum L.) using 15N tracer technique under Mediterranean Environment

Nitrogen topdressing timing modifies the gluten quality and grain hardness related protein levels as revealed by iTRAQ.

Nitrogen fertilization regimes significantly affect both grain quality and yield. Wheat plants were subjected to different application timing of topdressed nitrogen at the emergence of the top fifth (TL5), top third (TL3) and top first leaf (TL1), respectively. The iTRAQ (isobaric tag for relative and absolute quantitation) technology was adopted to obtain the complete proteome of wheat flour and to identify the differentially expressed proteins (DEPs) as regulated by nitrogen topdressing timing. Collectively, 591 proteins into 17 functional categories in flour of mature grains were identified. In comparison to TL3, 50 and 63 DEPs were identified in TL5 and TL1, respectively. Nine of the DEPs commonly dependent on nitrogen topdressing timing are the γ-gliadins or high-molecular-weight glutenin subunits. Additionally, delaying nitrogen topdressing modified the grain hardness and allergic protein content. The results suggested that altering nitrogen topdressing timing is a potential strategy for pursuing targeted processing quality of wheat flour.