Split Nitrogen Research Articles

Canopy Index and Productivity of Broadcasted Hybrid Rice (Oryza sativa L.) Influenced by Nitrogen Splitting Application

A filed experiment was layout in split plot design with three replications in two consecutive summer seasons of 2014 and 2015 in the Experimental farm of rice research section located at Sakha station, Kafr EL-Sheikh Governorate and Laboratory of Agric botany department of Faculty of Agriculture Assuit Al-Azhar university. Two Nitrogen fertilization doses in form of urea viz; 165 and 220 Kg N/ ha., were investigated under 6 schedules of nitrogen splitting application along with physiological life span of Egyptian hybrid rice one (EHR1) under broadcast seeded rice as following T1:1/2 basal(B) +1/2panicleinitiation (PI)., T2:1/3B+ 1/3ET+ 1/3PI., T3:., T5:1/4B +1/4ET +1/4PI +Mid-booting(MB)and T6:1/4B+1/4ETS+1/4PFS+1/4 panicle emergence (PE). Analysis of variance indicated that highly significant differences in all studied vegetative characters such as leaf area index, nitrogen concentration in flag leaf at flowering, vegetative dry weight at maturity under 220kg N/ha with multiple ways schedules of nitrogen application. yield and its attributes with high nitrogen dose 220kgN/ha with all schedules of nitrogen splitting application showed highly significant superiority in dry matter accumulation, chlorophyll content, nitrogen content, vegetative dry matter at maturity, leaf area index, canopy index as well as grain yield and its attributes. Four or three nitrogen doses one of them at late growth stage surpassed two way-schedule of nitrogen application in all abovementioned characters.It could be summarized that 220 Kg N/ha four equal premiums which jointed both of vegetative and reproductive growth stages with the vital premium at panicle emergence or mid-booting is considered the pertinent schedule to enhance and reach the ceiling productivity of Egyptian rice hybrid. Direct seeded for hybrid rice (DSHR) is considered the future avenue for rice cultivation in Egypt and all over the rice countries. Under DSHR improvement of canopy index is considered analeptic matrix for corresponding rice parameters which physiologically effect directly throughout raise up the contribution of post-anthesis assimilates (Current Photosynthesis) which resulted in maintaining rice grain yield and the nutritional value of rice grains and indirectly throughout increase the translocation of pre-anthesis assimilates (stored assimilates) which reflected on augmentation of harvest index.

Variability and determinants of yields in rice production systems of West Africa

Rice (Oryza spp.) is the major staple food for most countries in West Africa, but local production does not meet demand. Rice is grown mainly by smallholder farmers, and yields are generally low with high temporal and spatial variability. Low yields have been attributed to unfavorable climate conditions, poor soil quality, and sub-optimum agricultural practices. The objectives of this study were to assess variation in yields of three major rice production systems (irrigated lowland, rainfed lowland, and upland) across three climatic zones (semi-arid, sub-humid, and humid), and identify factors affecting that variation. We analyzed data on yield, climate, soil, and agricultural practices for 1305 farmers’ fields at 22 sites in 11 West African countries between 2012 and 2014. A boundary function approach was used to determine attainable yields. Random forest algorithm was used to identify factors responsible for yield variation. Average rice yield was 4.1, 2.0, and 1.5tha−1 in irrigated lowland, rainfed lowland, and rainfed upland systems, respectively, with maximum attainable yields of 8.3, 6.5, and 4.0tha−1. Yield difference between attainable and average yield tended to be higher in irrigated and rainfed lowland systems. In those two systems, yields were highest in the semi-arid zone, while no difference in yields among climatic zones was apparent for upland rice. High rice yields were associated with high solar radiation, high maximum temperature, intermediate air humidity, multiple split nitrogen (N) fertilizer applications, high frequency of weeding operations, the use of certified seeds, and well-leveled fields in the irrigated lowland system. Minimum temperature, solar radiation, rainfall, construction of field bunds, varietal choice, and the frequency of weeding operations were determinants of rice yield variation in the rainfed lowland system. Varietal choice, bird control, and frequency of weeding operations affected rice yields in the upland system. Improving access to inputs, improving input use efficiencies, and site-specific management strategies are recommended as priority interventions to boost rice yields at regional scale independent of production system and climatic zone.

Simulation of Hydrology and Nutrient Transport in the Hetao Irrigation District, Inner Mongolia, China

Intensive agricultural activities in the Hetao irrigation district have severely degraded local aquatic ecosystems and water quality, and Ulansuhai Lake is now the most rapidly degrading eutrophic lake in China. A better understanding of the hydro-agronomic and pollutant transport processes in the area is thus urgently needed. This study simulated monthly streamflow, total nitrogen (TN) and total phosphorus (TP) for the Hetao irrigation district using the Soil and Water Assessment Tool (SWAT) to evaluate the nutrient load, source areas, and hydrological pathways. The Nash-Sutcliffe efficiency (NSE) values obtained for the streamflow simulations were 0.75 and 0.78 for the calibration and evaluation periods, respectively. The SWAT model captured the temporal variation in streamflow (R2 > 0.8) for two periods; the NSE values for the TN and TP loads were 0.63 and 0.64 for the calibration period and 0.48 and 0.42 for the evaluation period, respectively. The predicted monthly TN load was correlated with irrigation (r = 0.61) and the monthly TP load with precipitation (r = 0.89), indicating that nitrogen transport is primarily associated with soil leaching and groundwater flow, and phosphorus is primarily transported by sediments caused by rainfall erosion. A case study of split nitrogen fertilizer applications demonstrated reduced annual TN load by as much as 13% in one year. Fertilization timing also affects the load in different pathways especially in lateral subsurface flow and shallow groundwater. Better agricultural management could thus reduce nitrogen losses, and buffer strips could minimize phosphorus transport.

Evaluating Split Nitrogen Applications and In-Season Tests for Organic Winter Bread Wheat

Achieving high grain yields and crude protein (CP) standards in organic winter wheat (Triticum aestivum L.) is challenging because ensuring that adequate nitrogen (N) is available at key periods of wheat growth is difficult in organic systems. Split application regimes and in-season N management tests may improve organic production. In field trials conducted over four site-years in Maine and Vermont, USA, N application regimes were analyzed for their effects on organic winter wheat, N uptake, grain yield, and CP. Tiller density and tissue N tests were evaluated as in-season decision tools. Eight treatments arranged in a non-factorial design differed in terms of N application timing (pre-plant (PP), topdress at tillering (T1), and topdress at pre-stem extension (T2)) and N rate. Treatments were: (1) an untreated check, (2) pre-plant N at a low rate of 78 kg N ha −1 (PP L ), (3) pre-plant N at a high rate of 117 or 157 kg N ha −1 (PP H ), (4) T1 78 , (5) PP L + T1 39 , (6) PP L + T2 39 , (7) PP H + T2 39 , and (8) PP L + T1 39 +T2 39 . Responses to N treatments were variable among site-years, however some common results were identified. The PP-only treatments increased grain yields more than they increased CP. The T1 78 and PP H + T2 39 treatments were the most effective at increasing yield and CP, compared with the PP-only treatments. Tiller density and tissue N tests were good predictors of grain yield (r = 0.52, p < and CP (r = 0.75, p < 0.001) respectively. Future work should test in-season decision tools using a wider range of tiller densities, and topdress N rates against tissue N measurements.

Effect of split and foliar application of nitrogen on leaf nitrogen concentration, SPAD index and photosynthesis in Bt. Cotton (Gossypium hirsutum L.)

A field experiment was carried out at Rahuri (Maharashtra) India in consecutive years of 2011 to 2012 to study the response of split and foliar application of nitrogen on leaf nitrogen concentration, SPAD index and photosynthesis in Bt cotton (Gossypium hirsutum L). Ten treatments comprising nitrogen–management practices (application of recommended dose of nitrogen in 3, 4, 5, 6 splits; foliar application of 20 g KNO3 litre-1 water, 20 g urea litre-1 water, combination of split application of nitrogen and foliar spray of 20 g KNO3 litre-1 water, 20 g urea litre-1 water and control) were tested on inceptisol. Results indicated that application of nitrogen in six splits (20% at sowing as basal and remaining in 5 equal splits at 30, 45, 60, 75 and 90 DAS) registered significantly higher leaf nitrogen content, SPAD index and rate of photosynthesis except 60 DAS where 4 nitrogen split showed higher leaf nitrogen content and SPAD index. Similarly the same treatment registered significantly higher plant height, dry matter accumulation, number of bolls plant-1 and lint yield.SAARC J. Agri., 14(2): 1-11 (2016)

Simulating the Impact of Nitrogen Management on Rice Yield and Nitrogen Uptake in Irrigated Lowland by ORYZA2000 Model

ABSTRACTThis paper considers the implications of ORYZA2000 model in simulating physiological traits of rice at different nitrogen concentrations. The experiment was conducted over the course of the growing season in 2012 and 2013 in Rice Research Institute, Deputy of Mazandaran, Iran. The variety used was Shiroudi as a high yielding variety. The considered factors were the amount of nitrogen at four levels (40, 80, 120, 160 kg N ha−1 and control) and nitrogen splitting in four levels. We compared simulated and measured grain yield, biomass, grain nitrogen, total plant nitrogen uptake, and leaf area index (LAI) by Student’s t-test of means and by absolute and normalized root mean square errors (RMSE). Results showed that grain yield was simulated with an RMSE of 411–423 kg ha−1 and a normalized RMSE of 6%. RMSE was 671–910 kg ha−1 for biomass on harvesting date. RMSE were 7–11 for grain nitrogen, and 10–13 for total plant nitrogen uptake. LAI was simulated with a normalized RMSE of 17–23%. Generally the model simulated LAI, an exceeded measured value for different nitrogen treatments. The most obvious finding that emerged from this study was that ORYZA2000 model can be applied as a supportive research tool for selecting the most appropriate strategies for rice yield improvement at various nitrogen fertilization concentrations.

Influence of rhizobium inoculation, split nitrogen application and plantgeometry on productivity of garden pea (Pisum sativum L.) in an acid alfisol

A field experiment comprising of twelve treatment combinations was conducted for two years at Himachal Pradesh Agricultural University, Palampur, India. Crop geometry treatment comprising of two row spacings (60 cm × 10 cm and 45 cm × 10 cm) were allocated to the main plots and six nitrogen management practices namely, Rhizobium inoculation in conjunction with 75 and 50 per cent of recommended N either as basal or split application and recommended N (100 %) were assigned in sub-plots. Wider spacing resulted in significant higher seed yield (7.3%) over close spacing along with superior performance of component traits and nutrient uptake. The split applied nitrogen resulted in better performance of different parameters which together enhanced seed yield by 13.8 per cent over recommended N as basal application. Augmentation of nitrogen with Rhizobium culture positively improved growth and yield parameters leading to net saving of 25 per cent N fertilizers as evident from higher seed yield in treatment comprising 75 per cent split applied N + Rhizobium over recommended N. Interaction effects of split applied N at both row spacings resulted in better performance for seed yield, other related traits and uptake of NPK. Split applied 100 per cent N at wide spacing resulted in 15.5 and 23.6 per cent higher seed yield over recommended N at wider and close spacing, respectively. It could be concluded that Rhizobium inoculation could save 25per cent synthetic fertilizer N. Wider spacing (60 cm × 10 cm) and split applied nitrogen was a better preposition for enhancing productivity of pea in an acid alfisol under north western Himalayas.

Effect of split application of nitrogen fertilizer on yield traits and yield of high yielding aromatic rice varieties in Bangladesh

A field experiment was conducted at Bangladesh Agricultural University, Mymensingh, Bangladesh during Aman season in 2013 to evaluate the effect of proper time of nitrogen application on yield and yield parameters of high yielding rice varieties. Two transplanted aromatic aman rice varieties (BRRI dhan37 and BRRI dhan38) and four timing of nitrogen fertilizer application (N 1 = ½ during final land preparation + ½ at 30 DAT, N 2 = 1 / 3 at 15 DAT + 1 / 3 at 30 DAT + 1 / 3 at 45 DAT, N 3 = 1 / 4 at 15 DAT + ½ at 30 DAT + 1 / 4 at 45 DAT and N 4 = 2 / 3 at 15 DAT + 1 / 3 at 45 DAT) were used in this experiment. The experiment was arranged in a randomized complete block design with three replications as factorial arrangement. All agronomic practices were applied as recommended for each cultivar. Yield and yield traits (plant height, total tillers, effective panicle, panicle length, grains per panicle, 1000-grain weight, grain yield, straw yield, harvest index) was measured. Results showed that the effect of nitrogen split application on plant height, total tillers, effective panicle, panicle length, grains per panicle, 1000-grain weight, grain yield and straw yield was significant. The results revealed that three equal splits of nitrogen (N 2 ) application ( 1 / 3 at 15 DAT + 1 / 3 at 30 DAT + 1 / 3 at 45 DAT) produced the highest grain yield (3.29 t ha -1 ) which was statistical differed from all N splits application treatments and the lowest grain yield (2.41 tha -1 ) was obtained from N 1 treatment which was statistically similar to N 4 treatment. The variety effect was significant on all traits except plant height, number of grains panicle -1 , number sterile spikelets panicle -1 and stubble yield. The variety BRRI dhan38 produced more grain yield than BRRI dhan37. The effect of nitrogen split application and variety (N×V) on total traits was significant and N 2 ×V 2 combination produced the highest grain yield among all the combinations.

RADIX: rhizoslide platform allowing high throughput digital image analysis of root system expansion.

BackgroundPhenotyping of genotype-by-environment interactions in the root-zone is of major importance for crop improvement as the spatial distribution of a plant’s root system is crucial for a plant to access water and nutrient resources of the soil. However, so far it is unclear to what extent genetic variations in root system responses to spatially varying soil resources can be utilized for breeding applications. Among others, one limiting factor is the absence of phenotyping platforms allowing the analysis of such interactions.ResultsWe developed a system that is able to (a) monitor root and shoot growth synchronously, (b) investigate their dynamic responses and (c) analyse the effect of heterogeneous N distribution to parts of the root system in a split-nutrient setup with a throughput (200 individual maize plants at once) sufficient for mapping of quantitative trait loci or for screens of multiple environmental factors. In a test trial, 24 maize genotypes were grown under split nitrogen conditions and the response of shoot and root growth was investigated. An almost double elongation rate of crown and lateral roots was observed under high N for all genotypes. The intensity of genotype-specific responses varied strongly. For example, elongation of crown roots differed almost two times between the fastest and slowest growing genotype. A stronger selective root placement in the high-N compartment was related to an increased shoot development indicating that early vigour might be related to a more intense foraging behaviour.ConclusionTo our knowledge, RADIX is the only system currently existing which allows studying the differential response of crown roots to split-nutrient application to quantify foraging behaviour in genome mapping or selection experiments. In doing so, changes in root and shoot development and the connection to plant performance can be investigated.Electronic supplementary materialThe online version of this article (doi:10.1186/s13007-016-0140-8) contains supplementary material, which is available to authorized users.

Split Nitrogen Application Improves Wheat Baking Quality by Influencing Protein Composition Rather Than Concentration.

The use of late nitrogen (N) fertilization (N application at late growth stages of wheat, e.g., booting, heading or anthesis) to improve baking quality of wheat has been questioned. Although it increases protein concentration, the beneficial effect on baking quality (bread loaf volume) needs to be clearly understood. Two pot experiments were conducted aiming to evaluate whether late N is effective under controlled conditions and if these effects result from increased N rate or N splitting. Late N fertilizers were applied either as additional N or split from the basal N at late boot stage or heading in the form of nitrate-N or urea. Results showed that late N fertilization improved loaf volume of wheat flour by increasing grain protein concentration and altering its composition. Increasing N rate mainly enhanced grain protein quantitatively. However, N splitting changed grain protein composition by enhancing the percentages of gliadins and glutenins as well as certain high molecular weight glutenin subunits (HMW-GS), which led to an improved baking quality of wheat flour. The late N effects were greater when applied as nitrate-N than urea. The proportions of glutenin and x-type HMW-GS were more important than the overall protein concentration in determining baking quality. N splitting is more effective in improving wheat quality than the increase in the N rate by late N, which offers the potential to cut down N fertilization rates in wheat production systems.

Efeitos de enxofre e nitrogênio na qualidade industrial e no rendimento de grãos de trigo

The consumer market’s demand and requirement for wheat grains which present a satisfactory industrial quality have driven the demand for enhanced cropping systems, especially related to nutritional aspects. In this context, the purpose of this research was to evaluate how the sulfur supplementation and the usage of nitrogen (N) affect the baking quality and the yield of the wheat grain cultivar TBIO Itaipu®. A randomized block experimental design in factorial arrangement, with two sulfur managements (with and without) and four split nitrogen managements (I: 100% of N in the double ring; II: 30% of N in the tillering period + 40% of N in the double ring + 30% of N in the ear development; III: 50% of N in the tillering period + 50% of N in the double ring; IV: 50% of N in the double ring + 50% of N in the ear development period), arranged in four repetitions. Our results showed that the sulfur supplementation increased the gluten content, which has been positively correlated with the strength and extensibility of the bread dough. This had a positive influence on the technological parameters of the flour used for baking. The splitnitrogen fertilizer application (in double ring, tillering, and ear development) increased the wheat grain yield due to the greater number of tillers per plant and also of the wheat ears per square meter.

A Comprehensive DFT Guide for Highly Efficient Electrochemical Ammonia Synthesis on New Class of Electrocatalysts

The results of a comprehensive computational screening for new electrocatalysts that are stable, active and selective towards electrochemical reduction of nitrogen to ammonia at room temperature and ambient pressure is presented on a range of transition metal nitride surfaces. Density functional theory (DFT) calculations are used to study the thermochemistry of cathode reaction so as to construct the free energy profile and to predict the required onset potential for activation of nitrogen to ammonia via a Mars-­van Krevelen mechanism. Five crucial criteria are investigated in this work to identify promising electrocatalysts for electrochemical ammonia formation in aqueous media; (1) identification of the reaction mechanism and calculation of the nitrogen splitting barrier, (2) investigation of the catalytic activity and quantification of the potential-determining/rate-determining steps, (3) determination of kinetic or thermodynamic barriers for vacancy diffusion into the bulk, (4) investigation of the stability of the surfaces against poisoning in an electrochemical environment, and (5) estimation of the potential required for removal of any oxygen atoms that may adsorb onto the surface upon exposure to electrochemical environment. With this approach, the (100) and (111) facets of the rocksalt as well as the (100) and (110) facets of the zincblende structures of all the naturally occuring d-block elements in the priodic table are scrutinized. The most promising candidates turned out to be the (100) facets of the rocksalt structure of VN, CrN, NbN and ZrN that should be able to form ammonia at ­-0.51 V, ­-0.76 V, -­0.65 V and -­0.76 V vs. SHE, respectively. All are found to be much more active towards nitrogen reduction than towards the competing hydrogen evolution reaction, in contrast to pure metals, which largely evolve hydrogen. Therefore, higher current efficiencies towards ammonia is expected at low onset potentials. An additional benefit to the present analysis is that the method presented in this work may be applicable to other aqueous phase heterogeneous catalytic reactions, where a Mars-van Krevelen mechanism is operative with both selectivity and activity being key catalytic criteria. Figure caption: Free energy diagram for NH3 formation via a Mars–van Krevelen mechanism on the (100) facet of RS VN where all the possible adsorption sites for H are investigated and the most energetically favourable site and therefore the most stable intermediates are depicted. Figure 1

Effect of split doses of nutrients on growth and yield parameters of banana cultivated in Assam

An experiment was conducted at Assam Agricultural University, to study the nutrient requirements of banana crop grown under rainfed conditions at different growth stages i.e. vegetative stage, flower bud initiation, flowering stage and bunch development stage. Application of nitrogenous and potassium fertilizer in splits at different growth stages of banana had significant influence on growth and yield parameters of the crop. The yield and quality parameters were significantly influenced by the different levels of the nitrogenous and potassium application at different stages. Combination of treatments, 100% recommended dose of fertilizers with nitrogen split as 40: 20: 20: 20 and potash split as 0: 0: 40: 60 at vegetative stage, flower bud initiation stage, pre-flowering stage and bunch development stage respectively, exhibited better growth, higher yield and quality of the fruits. This combination gave highest yield (58.64 tonnes/ha), weight of fingers (148.73 g), weight of 2nd hand (4.00 kg), bunch weight (19.00 kg), fingers per hand (21.32), length of finger (22.88 cm) and girth of finger (14.10 cm) alongwith better plant growth parameters. Thus, this combination may be recommended for commercial cultivation of banana in Assam.

Improving nitrogen-use and radiation-use efficiencies of C4 summer cerealsby split nitrogen applications under an irrigated arid environment

Shakeel AHMAD, Hakoomat ALI, Umair FAROOQ, Shahzad Usman KHAN, Atique-ur REHMAN, Naeem SARWAR, Ahmad Naeem SHAHZAD, Hulya DOĞAN*, Shabbir HUSSAIN, Muhammad Tauseef SULTAN, Abdul WAHEED, Muhammad ZIA-UL-HAQ, Khadim HUSSAIN, Muhammad Azam KHAN Department of Agronomy, Bahauddin Zakariya University, Multan, Pakistan Department of Seed Science, Vocational School, Bozok University, Yozgat, Turkey The Patent Office Karachi, Karachi, Pakistan Maize & Millet Research Institute, Yousaf Wala, Sahiwal, Pakistan Executive District Office Agriculture, Chiniot, Punjab, Pakistan

Efeito do trinexapac-etil associado a adubação nitrogenada elevada e parcelada na produtividade do trigo cultivar BRS-220

The use of high nitrogen doses, associated with the application of growth reducers, can be an alternative to wheat plants express high productive potential without the occurrence of lodging. For this reason, the aim of this study was to evaluate the effect of trinexapac-ethyl growth reducer associated with high and split nitrogen fertilization on yield and its components in wheat cultivar BRS 220. The experimental design was randomized blocks with two treatment and four replications, compose with the application of 110 kg N ha-1 with or without 0,4 g L-1 of trinexapac-ethyl. It was evaluated yield and its components, stem diameter, length of internode, plant height and stem length and the averages were submitted to Student t-test using Systat 13®. The application of the growth retardant contributed to a significant increase in yield and stem diameter of the plants, besides the reduction of height and length of stem and internode, when compared to the treatment without product application.

Is it necessary to split nitrogen fertilization for winter wheat? On-farm research on Luvisols in South-West Germany – CORRIGENDUM

Is it necessary to split nitrogen fertilization for winter wheat? On-farm research on Luvisols in South-West Germany – CORRIGENDUM

Direct Electrochemical Conversion of Nitrogen to Ammonia from Air and Water on Nitride Electro-Catalysts at Ambient Conditions

The use of ammonia as an energy carrier, chemical feedstock and specially fertilizer has triggered increased interest in developing alternative methods for ammonia synthesis in pursuit of decentralized and environmentally friendly approach. Although Ru and Fe within the Haber-Bosch process show good activity for catalysing nitrogen conversion to ammonia, its expense, scarcity, harsh experimental conditions (extremely high temperature and pressure) and sophisticated industrial setup are prohibitive to its decentralization complicating ammonia production in regions with relatively undeveloped infrastructure such as developing countries. Besides, the reliance of this process on natural gases for supplying its necessary hydrogen feedstock not only promotes severe CO2 emission to the environment but it also makes the production of ammonia and accordingly food and biofuels vulnerable to natural gas price fluctuations and political conflict in the oil-rich regions. Nature, on the other hand, reduces atmospheric nitrogen to ammonia by solvated protons and electrons at very moderate conditions, but engineering man-made ammonia to duplicate this in a small-scale approach still remains one of the challenges in modern chemistry. Nonetheless, electro-catalytic ammonia synthesis is a particularly feasible method due to the potential of utilizing renewable energy sources and mild operating conditions. Solid-state electrolytes and polymeric membrane assemblies are the most promising electrochemical approaches developed thus far and have exhibited great success with respect to increased yield of ammonia at ambient conditions. Nevertheless, the yield still remains rather low and the complexity of systems of this sort necessitates a simpler approach for realistic commercialization. In our previous work (Abghoui et al., Physical Chemistry Chemical Physics, 17 (2015) 4909), first-principles (DFT) calculations are used to identify transition metal nitride catalysts that show evidence of being able to produce ammonia electrochemically under small over-potential at ambient conditions. Among a wide range of transition metal nitrides, the (100) facets of rocksalt structure of VN and ZrN were explored as nitride (electro-) catalysts, which are able to suppress the hydrogen evolution reaction and most likely to increase the yield of ammonia production. In the current work and with similar approach, the catalytic activity of the (111) facets of mono-nitrides is investigated through Mars-van Krevelen (MVK) mechanism. This introduces new (electro-) catalysts for direct conversion of nitrogen to ammonia electrochemically at applied potentials of -0.60 V to -1.0 V vs. SHE. Possibility of ammonia formation is also explored via associative, dissociative and mixed associative-dissociative mechanisms on the clean surface of all these nitrides. Besides, stability of these catalysts against poisoning and decomposition is investigated. Upon exposure of the catalyst to atmosphere or electrochemical media, there is a possibility of oxide formation on the surface. The potential required to reduce this oxide layer to water is estimated as well. Results presented here show that both associative and dissociative pathways for ammonia formation is deactivated at the surface of these nitrides due to extremely weak adsorption of N2 on the surface and very high activation barriers of above 2.0 eV for nitrogen splitting, respectively. Therefore, the MVK mechanism is the dominant pathway for effective reduction of nitrogen to ammonia at ambient conditions on these nitride (electro-) catalysts. Hence, with the high abundance of atmospheric nitrogen and by using water as a proton source these promising catalysts could facilitate low-cost, high-yield ammonia production at ambient conditions, with significant benefits to the environment and economy.

Niobium-nitrides derived from nitrogen splitting.

The easy-to-prepare Nb(V) aryloxide complex [(ArO)2Nb(μ-Cl)Cl2]2 (OAr = 2,6-bis(diphenylmethyl)-4-tert-butylphenoxide) is a precursor to both Nb(IV), [trans-(ArO)2NbCl2(THF)2], and Nb(III), K3[(ArO)4Nb2(μ-Cl)3Cl2], molecules. The Nb(IV) and (V) complexes readily split atmospheric nitrogen at room temperature and 1 atmosphere, under reducing conditions, to produce the low-coordinate nitride dimer [(ArO)2Nb(μ-N)]2 and its radical anion, K[(ArO)2Nb(μ-N)]2.

Effect of split application of ammonical and nitrate sources of nitrogen on lilium growth and yield

The aim of experiment was to evaluate the effect of split application of urea and calcium nitrate nitrogen sources on plant growth and yield in Asiatic lilies. Significant differences were observed in growth parameters and behavior of two cultivars viz., Serreda and Navona. Calcium nitrate significantly improved plant height, leaf area (LA) and LA index (LAI) recorded at 50, 75, 90, and 105 days after planting. Bulb yield parameters varied significantly between two cultivars. Calcium nitrate significantly improved bulb weight, bulb circumference, the number of bulbs plant−1 and propagation coefficient. However, the effect of three and four split nitrogen application on plant height; LA and LAI was significant at 90-105 day interval.

Short Response of Spring Wheat to Tillage, Residue Management and Split Nitrogen Application in a Rice-Wheat System

A field experiment was conducted to study the impact of tillage, crop residue management and nitrogen (N) splitting on spring wheat (Triticum aestivum L.) yield over 2 yr (2010-2012) in a rice (Oryza sativa L.)-wheat system in northwestern Pakistan. The experiment was conducted as split plot arranged in randomized complete blocks design with three replications. Treatments comprised six tillage and residue managements: zero tillage straw retained (ZTsr), zero tillage straw burnt (ZTsb), reduced tillage straw incorporated (RTsi), reduced tillage straw burnt (RTsb), conventional tillage straw incorporated (CTsi), and conventional tillage straw burnt (CTsb) as main plots and N (200 kg ha−1) was applied as split form viz., control (no nitrogen & no splitting, N0S0); 2 splits of total N, half at sowing and half at the 1st irrigation (i.e., 20 d after sowing (DAS)) (NS1); 3 splits of total N, 1/3 at sowing, 1/3 at the 1st irrigation, and 1/3 at the 2nd irrigation (NS2); 4 splits of total N, 1/4 at sowing, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation (45 DAS), and 1/4 at the 3rd irrigation (70 DAS) (NS3); and 4 splits of total N, 1/4 at the 1st irrigation, 1/4 at the 2nd irrigation, 1/4 at the 3rd irrigation, and 1/4 at the 4th irrigation (95DAS) (NS4) as sub plots. The results showed that the most pikes m−2, grains/spike, 1000-grain weight, grain yield, and N use efficiency (NUE) were obtained at zero tillage, straw retained and 4 splits application of total N (i.e., at sowing 20, 45 and 70 d after sowing). The results indicated that ZTsr with application of 200 kg N ha−1 in 4 equal splits viz. at sowing 20, 45 and 70 d after sowing is an appropriate strategy that enhanced wheat yield (7436-7634 kg ha−1) and N efficiency (28.6-29.5 kg kg−1) in rice-wheat system.