High Nitrogen Rates Research Articles

Determine the Balance of Nitrogen, Potassium, and Silicon Fertilization for the Control of Rice Tungro Disease Using Response Surface Methodology

This study evaluates the efficacy of combined N, K, and Si treatments to find the balance of these three elements for tungro disease control and rice grain production. The study was conducted in a pot under a glasshouse. These elements were chosen as several findings have indicated the positive benefits of nitrogen (N), potassium (K), and silicon (Si) fertilization on plant development, yield, and biotic stress relief. The methods used were central composite design and response surface methodology. Complete and balanced nutrition has always been the first line of defense for plants due to the direct involvement of mineral elements in plant protection. The results showed that rice tungro disease could be controlled with 138:42:62:200 (N:P2O5:K2O:Si). A high rate of nitrogen is needed to reduce disease development. The results on N may explain that not all conditions of rice plants are at risk with high N rates. Adding Si fertilizer contributes to plant defense mechanisms and plays a role in yield formation. In contrast, the balance of fertilizer for maximizing grain yield per plant was found to be not dependent on nitrogen but needed either low K (62 kg K2O/ha) or high K (80 kg K2O/ha) but with moderate Si (150 kg Si/ha). Prioritizing tungro disease control and adopting the rate of N:K2O:Si (138:62:200), it was found that there was a yield reduction of an average of 7.7%.

Light Quality Effect on Internal N Retranslocation in Podocarpus macrophyllus Precultured with Exponential Nutrient Loading.

Streetlamp light is inevitable in the night landscape of a city and may affect the phenology of newly planted ornamental plants, but it has rarely been fully examined. Newly transplanted ornamental plants probably suffer periodic shocks, which mainly result from the inefficient reuse of internal nutrients for new growth. Exponential nutrient loading (ENL) is well known for its ability to overcome transplant shocks by promoting retranslocation for the reuse of strengthened nutrients from internal reserves in precultured seedlings. Transplantation to urbanized lands is distinct from that of montane areas; this is mainly due to a high frequency of exposure to the artificial illumination of night lighting. It is suspected that this lighting modifies vegetative phenology and generates potential risks by increasing reliance on internal nutrient retranslocation. In this study, Podocarpus macrophyllus seedlings were cultured with ENL at low and high rates of nitrogen (N) deliveries (40 and 120 mg N seedling-1, respectively), and the high-rate treatment was identified as being able to trap seedlings within toxic states. A labeled 15N isotope was pulsed to transplanted seedlings exposed to simulated light qualities in red, green, and blue light spectra. The seedlings harvested at one month showed rare responses to the interactive spectra and preculture treatments, but most of them responded to the low-rate N preculture treatment with stronger abilities in terms of the reuse of internal N and the synthesizing of photosynthetic pigments. In conclusion, it was verified that night light enforces the effect on newly transplanted plants; the red light invoked internal N for reuse, and the blue light promoted the uptake of the current N. The internal N reserve established through preculture ENL rarely made a contribution to the night light effect, except for the enhancement of height growth in the red light. The red light spectrum was recommended for the exposure of newly transplanted seedlings due to its effect on the enhancement of the retranslocation of internal N and the induction of a steady state of uptake from the current N input.

Schizolobium parahyba var. amazonicum seedling growth by Trichoderma spp. strains under nitrogen rates

This study evaluated the initial development of paricá (Schizolobium parahyba var. amazonicum) seedlings under different nitrogen rates with the application of Trichoderma spp., using a randomized complete block design in a 4x5 factorial scheme (strains and rates) with seven replications. The evaluated traits were plant height, stem diameter, leaf and stem fresh weights, leaf and stem dry weights, and aerial part dry and fresh weights. Trichoderma spp. strains did not satisfactorily promote paricá seedlings (Schizolobium parahyba var. amazonicum) under high nitrogen rates. However, the Trichoderma harzianum IBLF 006 WP strain was efficient only under low nitrogen availability.

Potential Risk Identification of Agricultural Nonpoint Source Pollution: A Case Study of Yichang City, Hubei Province

Potential risk identification of agricultural nonpoint source pollution (ANPSP) is essential for pollution control and sustainable agriculture. Herein, we propose a novel method for potential risk identification of ANPSP via a comprehensive analysis of risk sources and sink factors. A potential risk assessment index system (PRAIS) was established. The proposed method was used to systematically evaluate the potential risk level of ANPSP of Yichang City, Hubei Province. The potential risk of ANPSP in Yichang City was 18.86%. High-risk areas account for 4.95% and have characteristics such as high nitrogen and phosphorus application rates, large soil erosion factors, and low vegetation coverage. Compared with the identification results of the Diffuse Pollution estimation with the Remote Sensing (DPeRS) model, the area difference of the same risk level calculated by the PRAIS was reduced by 33.9% on average. This indicates that PRAIS has the same level of accuracy as the DPeRS model in identifying potential risks of ANPSP. Thus, a rapid and efficient identification system of potential risks of regional ANPSP was achieved.

The Influence of Mineral NPK Fertiliser Rates on Potassium Dynamics in Soil: Data from a Long-Term Agricultural Plant Fertilisation Experiment.

A fertilisation experiment, with the aim to determine the effects of different potassium fertiliser rates and their interactions with nitrogen and phosphorus on field-rotation productivity, potassium balance, fertiliser utilization, and changes in the content of potassium in soil, was carried out in Lithuania between 1971 and 2020. The multi-factorial scheme with 45 treatment plots, where seven rates (including zero) of nitrogen, phosphorus, and potassium fertilisers were studied. The experimental treatments during the study period were carried out on winter wheat, spring wheat, spring barley, sugar beet, spring rapeseed, and annual and perennial grasses. It was found that potassium fertilisers were the most effective on agricultural crops when used in combination with other major plant nutrients-i.e., nitrogen and phosphorus. The required balance of potassium (K2O) in the soil was measured, when nitrogen and phosphorus fertilisers were applied together to compensate for potassium removal; when applying low nitrogen (N) (72 kg ha-1) and phosphorus (P2O5) (64 kg ha-1) fertiliser rates, 128 kg ha-1 of potassium fertilisers are required. When using high nitrogen (180 kg ha-1) and phosphorus (160 kg ha-1) fertiliser rates, 160 kg ha-1 of potassium is needed. The highest potassium uptake, reaching 51.6%, was achieved when plants had been fertilised with nitrogen (108 kg ha-1), phosphorus (96 kg ha-1), and potassium (96 kg ha-1). When fertilising with potassium fertilisers alone, the content of plant-available K2O content in the soil increased, whereas with fertilisation with nitrogen and phosphorus combined K2O content is decreased, except in the plots where the plants had been fertilised with potassium fertiliser at rates of 128 kg ha-1 and higher. Due to the influence of fertilisers, the amount of non-exchangeable potassium in the soil also increased, but relatively little compared to the amount of available potassium content. Thus, one of the main conditions for the effective use of potassium fertilisers is ensuring optimal plant nutrition with other nutrition elements, especially nitrogen and phosphorus.

Comparative simulation of crop productivity, soil moisture and nitrate-N leaching losses for intermediate wheatgrass and maize in Minnesota using the DSSAT model

Perennial grain crops are a potential alternative source of staple foods and animal forage that can also provide additional environmental benefits over annual crops. Intermediate wheatgrass (IWG; Thinopyrum intermedium) is a new perennial dual-use crop for grain and forage, with growing interest among stakeholders as it produces grain in a more environmentally sound manner than current annual crops. DSSAT model simulations were performed for maize and a new DSSAT model for IWG based on data collected from field studies conducted during 2013–2015 at three different locations, i.e., Lamberton, Waseca and Crookston using low (zero), medium (60–80 kg ha−1) and high fertilizer nitrogen (N) rates (120–160 kg ha−1). The DSSAT CERES-Maize and CROPGRO-PFM models used as the basis for simulating IWG were calibrated at the high N rate to predict the yield/biomass, soil water balance, and soil nitrogen balance in maize and IWG, respectively, for the medium and low N rate treatments. Model predictions for maize yield and IWG biomass (0.89 >= Nash Sutcliffe Efficiency >= 0.58), soil profile moisture (0.81 >=NSE>=0.53) ranged from very good to satisfactory for maize and the high N rate in IWG, with nearly satisfactory accuracy for IWG under the medium and zero N rates. Simulation results indicate that low, medium and high N rates produced an average IWG biomass of 7.8, 9.7, and 10.5 t ha−1, in addition to observed grain yield of 0.36, 0.49, and 0.45 t ha−1, respectively. The corresponding N rates produced 5.9, 7.9, and 8.7 t ha−1 maize yield. Soil profile moisture under IWG and maize averaged 0.25 and 0.29 m3m−3, respectively. Averaged over N rates and locations, IWG and maize had values for crop evapotranspiration (ETc) of 592 vs. 517 mm; deep percolation of 100.8 vs. 154.5 mm; and nitrate-N leaching losses of 2.6 vs. 17.9 kg ha−1, respectively. Results indicate that perennial IWG not only produced high biomass under rainfed conditions, but also reduced deep percolation by efficiently using soil profile moisture, leading to nitrate-N leaching losses six to seven times lower than for maize.

Nitrogen and Sulfur Fertility Practices: Influences on Hop Chemistry, Aroma, and Nitrate Accumulation

Multiphasic studies were conducted to quantify how sulfur fertilization influences nitrate levels in hops, and how nitrogen and sulfur fertilizer dose jointly affect hop yield, brewing chemistry, and aroma of hops and beer. In an observational study of commercial lots of Simcoe® hops, a weak positive correlation was found between sulfur and nitrate concentrations. In field studies with Simcoe® in Washington, factorial combinations of representative low and high rates of nitrogen and sulfur fertilizer revealed that nitrate content of cones increased 13 to 22% with increasing nitrogen dose yet declined 8 to 8.7% with an increasing sulfur dose. Yield was unaffected by the lower dose of nitrogen when sulfur dose was high; effects on α-acids, total oil, and hop and beer aroma were not detected. Cysteine-3SH and cysteinylglycine-3SH were reduced 19% and 23%, in cones that received the higher sulfur dose in one year; other thiols and precursors were unaffected. In cultivar Willamette in Oregon, increasing sulfur dose over an 11-fold range by varying nitrogen fertilizer form from urea to ammonium sulfate had small to non-detectable effects on yield, α-acids, or nitrate concentrations. Hop aroma and brewing characteristics appear largely invariant to sulfur fertilization; increased sulfur fertilization may reduce hop nitrate levels modestly in certain situations.

Energy Crisis—Alternative Use of Winter Bread Wheat Grain Depending on Protein Content

Our economic analysis aimed to evaluate the profitability of winter bread wheat production based on two fundamental aspects. The first was the grainprotein content as a criterion for determining grain prices. The other was a comparative simulation of production profitability relying on grain production costs in 2015 and 2022. We used the results of a field experiment conducted in 2014 and 2015 involving winter bread wheat fertilised with nitrogen applied at progressive increments of 40 kg N ha−1 within arange from 0 to 240 N ha−1 with or without fungicide protection. We assumed that experimental factors significantly affected both the yield and the market value of grain, and hence the profitability conditioned by wheat prices on global markets. The working hypothesis of this paper is: wheat production profitability has not changed in the face of a global energy crisis. Our analysis shows that growing bread wheat generates profit when inputs are high: these inputs include high nitrogen rates and full crop protection. The real grain selling price guarantees production profitability. We should consider that, in the circumstances of a global energy crisis, the world should possibly switch to baking products from low-protein flour. Only upon such an assumption can the expenditure on fertilisers and fungicides be significantly reduced.

Effects of Different Topdressing Nitrogen Rates on Soil Fungal Community Structure and Ecological Network in Wheat Field Under Crop Residue Retention

Crop residue retention and fertilizer application are the main sources of soil nutrient input in fields. Crop residue retention combined with appropriate fertilizer application rates could provide necessary nutrients for crop production under the premise of environmentally friendly conditions. The aim of this study was to clarify the influence of different topdressing nitrogen rates on the soil fungal community in a wheat field under crop residue retention and to evaluate the rationality of nitrogen fertilizer management in winter wheat from the perspective of soil ecological function. On the basis of full straw retention and 150 kg·hm-2 basal nitrogen, treatments with five topdressing nitrogen rates (0, 37.5, 75, 112.5, and 150 kg·hm-2) were set up. The abundance, diversity, structure, and ecological network of soil fungal communities were analyzed using real-time fluorescence quantitative PCR and high-throughput sequencing, and the main soil physical and chemical factors driving the change in soil fungal communities were explored. The results showed that, compared with the no topdressing nitrogen and low topdressing nitrogen rate treatments, high topdressing nitrogen rate treatments increased soil total nitrogen and mineral nitrogen and decreased soil pH, total phosphorus, available phosphorus, and available potassium. Compared with the no topdressing nitrogen treatments, the 37.5-150 kg·hm-2 topdressing nitrogen treatments significantly increased soil fungal community abundance (P<0.05), whereas there was no significant difference among different topdressing nitrogen treatments (P>0.05). The Heip index and Shannon index of soil fungal communities decreased gradually with the increase in topdressing nitrogen rate, and the Sobs index, Heip index, and Shannon index of soil fungal communities in the treatment with 150 kg·hm-2 topdressing nitrogen were significantly lower than those of 0-75 kg·hm-2 topdressing nitrogen treatments (P<0.05). Principal component analysis and similarity analysis showed that there were significant differences in soil fungal community structure under different topdressing nitrogen rate treatments (P<0.05). With the increase in topdressing nitrogen rate, the number of network edges and average number of neighbors of soil fungal ecological network increased first and then decreased, and the network complexity of 37.5 kg·hm-2 topdressing nitrogen treatments was the highest. Compared with 0-75 kg·hm-2 topdressing nitrogen treatments, 112.5 kg·hm-2 and 150 kg·hm-2 topdressing nitrogen treatments increased the characteristic path length of the soil fungal ecological network, whereas it decreased the network density. With the increase in topdressing nitrogen rate, the relative abundance of soil saprotrophs gradually increased, and the pathotroph-saprotroph-symbiotroph relative abundance gradually decreased. Redundancy analysis showed that soil pH, total phosphorus, mineral nitrogen, available phosphorus, and available potassium were the main soil physicochemical factors affecting the soil fungal community structure in the wheat field under different topdressing nitrogen rate treatments. In conclusion, on the basis of straw retention and basal nitrogen, topdressing nitrogen at the wheat jointing stage could change the diversity, structure, and species composition of the soil fungal community, in turn affecting the soil fungal ecological network and function, and high topdressing nitrogen rates could reduce soil fungal community diversity, ecological network complexity, and network density.

Varying plantain content in temperate ryegrass-white clover pastures affects urinary-nitrogen excretion of non-lactating dairy cows

Dairy cow urine patches contain high rates of nitrogen (N; >500 kg N/ha) and represent the main source of N loss from grazed pastoral systems. Emerging research has identified plantain (Plantago lanceolata) as a key forage to potentially reduce urine N (UN) losses from dairy cows. This experiment examined the effect of increasing proportions of plantain in the diet of dairy cows on UN excretion relative to a ryegrass-white clover diet. Twenty mixed aged non-lactating dairy cows were randomly assigned to one of five treatment diets; 0 %, 20 %, 40 %, 60 % or 100 % plantain (dry matter basis), with the remainder comprised of ryegrass-white clover pasture and grass-silage. Cows were fitted with urine sensors to measure urination event N concentration, volume and frequency. Daily N intake increased with increasing proportions of plantain in the diet due to the greater N concentration of plantain. Conversely, mean UN concentration was reduced as the proportion of plantain in the diet increased. Urine-N concentration was >40 % lower for cows on 100 % plantain compared with 0 % plantain (0.46 and 0.81 % N respectively). There was no treatment effect on the total daily amount of UN excreted, indicating a dilution effect of plantain as total daily urine volumes markedly increased with increasing plantain diets. Nitrogen load per urination event was lower for cows on 100 % plantain than 0 % despite greater N intake, with no significant difference for the intermediate treatment groups. The reduced N load per event for cows on >60 % plantain could help to reduce N leaching losses at the urine patch level. This experiment suggests that a reduction in UN concentration can be achieved on low levels of plantain (20 % of the diet), but >60 % plantain diets are required to reduce N load per event.

Influence of Nitrogen Fertilization on Root Growth Dynamics and Yield of Chia (Salvia hispanica L.) in Greenhouse Pots

&#x0D; A greenhouse pot experiment was conducted in Western Greece in order to evaluate the effect of different nitrogen rates on the development of the root system and productivity of chia (Salvia hispanica L.) plant. The experiment followed a completely randomized design (CRD), with six treatments, different rates of applied nitrogen (0, 25, 50, 75, 100 and 125 kg ha-1 equivalent to 0, 134, 268, 402, 536 and 670 mg nitrogen pot-1). The results of this study showed that root length density (RLD) and root mass density (RMD) increased with the increased rate of applied nitrogen and the highest values (1.297 cm cm-3 and 1.178 mg cm-3, respectively) were found after the application of 670 mg nitrogen pot-1 at 100 days after sowing (DAS). Plant height (106.06 cm) and leaf area per plant (883.14 cm2) were significantly affected by the highest rate of nitrogen. Additionally, dry matter and seed yield per plant were clearly affected by fertilization, with the highest values (27.57 g and 4.20 g, respectively) obtained in plants treated with 670 mg nitrogen pot-1. In conclusion, increasing the levels of applied nitrogen up to 670 mg N pot-1 improves root development and therefore the yields of chia.&#x0D;

Intraspecific Leaf Trait Variation across and within Five Common Wine Grape Varieties.

Variability in traits forming the Leaf Economics Spectrum (LES) among and within crop species plays a key role in governing agroecosystem processes. However, studies evaluating the extent, causes, and consequences of within-species variation in LES traits for some of the world’s most common crops remain limited. This study quantified variations in nine leaf traits measured across 90 vines of five common wine grape (Vitis vinifera L.) varieties at two growth stages (post-flowering and veraison). Grape traits in these varieties covary along an intraspecific LES, in patterns similar to those documented in wild plants. Across the five varieties evaluated here, high rates of photosynthesis (A) and leaf nitrogen (N) concentrations were coupled with low leaf mass per area (LMA), whereas the opposite suite of traits defined the “resource-conserving end” of this intraspecific LES in grape. Variety identity was the strongest predictor of leaf physiological (A) and morphological traits (i.e., leaf area and leaf mass), whereas leaf chemical traits and LMA were best explained by growth stage. All five varieties expressed greater resource-conserving trait syndromes (i.e., higher LMA, lower N, and lower Amass) later in the growing season. Traits related to leaf hydraulics, including instantaneous water-use efficiency (WUE), were unrelated to LES and other resource capture traits, and were better explained by spatial location. These results highlight the relative contributions of genetic, developmental, and phenotypic factors in structuring trait variation in the five wine grape varieties evaluated here, and point to a key role of domestication in governing trait relationships in the world’s crops.

Auxin-regulated timing of transition from vegetative to reproductive growth in rapeseed (Brassica napus L.) under different nitrogen application rates.

Accelerating the differentiation of floral meristem (FM) from shoot apical meristems (SAM) which determines the conversion from vegetative to reproductive growth is of great significance for the production of rapeseed (Brassica napus L.). In this research, the mechanisms of different nitrogen (N) application rates (low N, N1; normal N, N2; and high N, N3) on different FM development stages triggering the regulation of FM differentiation genes through the auxin biosynthetic and signal transduction were investigated. We found that the stage of FM differentiation, which was identified through a stereomicroscope and scanning electron microscope, came 4 and 7 days earlier under high N rate than under normal and low N levels, with the seed yield increased by 11.1 and 22.6%, respectively. Analysis of the auxin and its derivatives contents showed that the main biosynthesis way of auxin was the indole acetaldehyde oxime (IAOx) pathway, with 3-Indole acetonitrile dramatically accumulated during FM differentiation. At the same time, an obvious decrease of IAA contents at each FM differentiation stage was detected, and then gradually rose. Results of the expression of genes involved in auxin biosynthesis, auxin signaling transduction, and FM identification under five FM differentiation stages and three nitrogen application rates showed that genes involved in auxin biosynthesis were regulated before the FM differentiation stage, while the regulation of FM identity genes appeared mainly at the middle and later periods of the five stages, and the regulation level of genes varied under different N rates. Taken together, a high nitrogen rate could accelerate the initiation of FM differentiation, and auxin involved a lot in this regulation.

Model-based evaluation of the impacts of aeration on tightly bound and loosely bound extracellular polymeric substance production under non-steady-state conditions

Tightly bound extracellular polymeric substances (TB-EPS) and loosely bound extracellular polymeric substances (LB-EPS) affect the flocculability and settleability of sludge and the transfer of oxygen, which are highly related to aeration. In this study, we systemically evaluated the expanded unified model-TL2.1 for its long-term simulation of TB-EPS and LB-EPS. Two different aeration conditions and three different influent carbon sources were used to evaluate the model, and the simulation results fit well with the experimental data. TB-EPS and LB-EPS production increased with aeration intensity. The influence of aeration parameters on TB-EPS and LB-EPS production in a short-term batch system and long-term sequencing batch reactor (SBR) system was compared. The aeration parameters included the total transfer coefficient (kLa) and the concentration of dissolved oxygen at the interface (CS). To ensure a high removal rate of substrates and ammonia nitrogen and achieve a stable active biomass concentration, the following aeration parameters can be adopted to reduce energy wastage during aeration: when CS is 2 mg/L, kLa can be set above 30 h−1 and below 50 h−1; when kLa is 50 h−1, CS can be set above 1 mg/L and below 1.5 mg/L. This study systematically revealed the influence of aeration on TB-EPS and LB-EPS formation in an SBR system through a mathematical model, and it provides a theoretical basis for better understanding aeration.

Nitrogen metabolism of two tropical forage grass species: nitrogen availability × cultivars

The understanding about N metabolism in roots and/or shoots of forage grasses should help determine how some cultivars use N more efficiently. This study was designed to determine whether two Brachiaria brizantha cultivars and two Panicum maximum cultivars differ in their N metabolism. Two cultivars of Panicum maximum and two cultivars of Brachiaria brizantha were investigated under the supply of low and high nitrogen rates in a greenhouse experiment. Some characteristics such as dry mass production, total nitrogen, nitrate and ammonium concentrations and contents; nitrate reductase (NR) and glutamine synthetase (GS) activities; and total free amino acid concentrations in shoots and roots were measured. The results showed that Panicum cultivars showed higher NR activity and GS activity in diagnostic leaves (DL) than Brachiaria cultivars. Brachiaria cultivars showed the highest ammonium concentrations in roots at low N supply and Panicum cultivars at high N supply. The total amino acid concentrations in DL were highest in Panicum and root total amino acid concentrations were highest in Brachiaria. Panicum and Brachiaria cultivars differed in their nitrogen metabolism with varying N supply. The results indicate that at low nitrogen supply to the pasture, Brachiaria brizantha cultivar Piatã may be an option to use in less intensive production environments, instead of high dry mass production. For those pastures with high nitrogen availability, the cultivars Mombaça and Aruana of Panicum maximum were clearly superior to Piatã, which suggests priority in the selection of these cultivars to be used in more intensive production systems that apply more nitrogen

In situ nitrous oxide and dinitrogen fluxes from a grazed pasture soil following cow urine application at two nitrogen rates

Cattle grazing of pastures deposits urine onto the pasture soil at high nitrogen (N) rates that exceed the pasture's immediate N demands, increasing the risk of N loss. Nitrous oxide (N2O), a greenhouse gas, and dinitrogen (N2) are lost from the cattle urine patches. There is limited information on the in situ loss of N2 from grazed-pasture systems which is needed for understanding pasture soil N dynamics and balances. The 15N flux method was used to determine N2 and N2O fluxes over time following synthetic urine-15N application at either 400 or 800 kg N ha−1 to a grazed perennial pasture soil. Results showed that daily N2O fluxes were higher under 800 kg N ha−1 than under 400 kg N ha−1, but there was no significant difference in N2 fluxes. Cumulative N2O emissions from soil with 400 kg N ha−1 and 800 kg N ha−1 applied represented 0.16 ± 0.08% and 0.43 ± 0.08% of deposited N, respectively, while emitted N2 accounted for 32.1 ± 4.1% and 14.4 ± 1.7%, respectively, over 95 days after urine application. Codenitrification and denitrification co-occurred, with denitrification accounting for 97.9 to 98.5% of total N2 production. Recovery of urine-15N in pasture decreased with increasing N rate with 14.7 ± 0.5% and 9.9 ± 0.8% recovered at 400 and 800 kg N ha−1, respectively after 95 days. The N2O/(N2 + N2O) product ratio was generally higher during periods of nitrification of urine-N (the first month after urine application) but with no clear relationship to other measured variables. Contrary to our hypothesis, an elevated urine-N rate did not enhance N2 loss. This is speculated to be due to enhanced ammonia volatilisation and transfer of N as nitrate, to deeper soil layers. Soil relative gas diffusivity indicated that high N2 fluxes resulted from entrapped N2 diffusing from the draining soil.

Maximizing spring wheat productivity in the eastern Canadian Prairies: I. Yield, yield components, and lodging risk

AbstractSpring wheat (Triticum aestivum L.) yields across the Canadian prairies are rising, however, a yield gap remains between average yield and yield potential, which can be explored further under Prairie conditions. The high rates of nitrogen (N) fertilizer required for current high‐yielding cultivars may increase lodging risk adding to this yield gap. The objectives of this study were to determine the influence of intensive management through N fertilization and plant growth regulator (PGR) application, on grain yield, yield components, and their relationships, in addition to lodging risk. Field trials were conducted at two locations in 2018 and 2019 in Manitoba, Canada, to evaluate three high‐yielding spring wheat cultivars, three N management strategies, and the application of a PGR. Kernels per spike had the strongest overall linear relationship with grain yield (r2 = .47), while the response of spikes per plant was highly related to yield response with alterations in N and PGR management practices (r2 = .98). Splitting N fertilizer applications showed potential to reduce lodging risk of spring wheat, while maintaining yield and increasing protein. The PGR applications reduced lodging and increased grain yield by 91 kg ha−1 mainly through increases in kernels per spike. To achieve consistent yield increases, management practices should maximize early season N availability to target increases in spikes per plant and kernels per spike, thus a PGR application may be required to balance increased lodging risk.

Dense Planting with Reducing Nitrogen Rate Increased Nitrogen Use Efficiency and Translocated Nitrogen in Grains in Double-Cropped Rice

Nitrogen fertilization and planting density are two key factors that influence the yield of rice. Reducing nitrogen fertilizer input and increasing planting density will help to improve nitrogen use efficiency and stabilize yield. Field and 15N tracer method in plot experiments were conducted to study the trends of yield, nitrogen use efficiency (NUE) and nitrogen transfer of hybrid rice and conventional rice under dense planting with a reduced nitrogen rate (DPRN) and sparse planting with a high nitrogen rate (SPHN). Among the nitrogen in rice plants, the proportion of nitrogen from fertilizer under the DPRN was reduced by 1.8–13%. The late-season rice (LSR) had a higher rate of decrease compared with the early-season rice (ESR). The uptake efficiency of nitrogen fertilizer was significantly higher under the DPRN than that under the SPHN, with an increase of 7.7–21.9%. The accumulated nitrogen and translocated ratio under the DPRN before the heading stage were 6.1–10.8% and 2.0–9.6% higher than those under the SPHN, respectively. The yield did not change under different treatments. Those findings suggest that the DPRN could guarantee a stabilized yield while increasing the NUE and the amount of translocated nitrogen in the double-cropped rice system.

Hot-pressed membrane assemblies enhancing the biofilm formation and nitrogen removal in a membrane-aerated biofilm reactor

Membrane-aerated biofilm reactor (MABR) is gaining popularity in wastewater treatment as a result of the low-energy delivery of oxygen from the carrier side and reduced sludge waste production, although its wider application suffers from the difficulty in microbial colonization on the smooth, hydrophobic membrane surface. In this study, a newly designed membrane/non-woven fabric assembly, prepared via a facile hot-pressing method, is demonstrated to be efficient in promoting the biofilm formation and nitrogen removal in MABR. The assembly achieved rough surface structure to retain biomass whilst sustained the surface hydrophobicity for a high oxygen transfer ability, which is crucial to support a resilient biofilm. Compared with the slower biomass growth and severe detachment of biofilm in the control, a thicker biofilm was quickly developed on the hot-pressed membrane assembly. High loading rates of organic matter, ammonia nitrogen and total nitrogen (TN) in the MABR using the hot-pressed membrane were 154.9 ± 5.4 g COD/(m2·d), 25.5 ± 0.6 g N/(m2·d) and 22.6 ± 0.7 g N/(m2·d), respectively. Particularly, the removal efficiency of TN was up to 82.8%, which was 2.5 times higher than the control. Furthermore, the biofilm grown on the hot-pressed membrane assembly organized a stable microbial community structure with a steady evolution to achieve a synergistic denitrifying function. Among the bacterial phylotypes, OLB8 might be crucial in denitrification. This study highlighted the significance of this facile membrane modification method to improve the process performance of MABR in wastewater treatment.

Accumulation of Nitrogen, Phosphorus, and Potassium in Various Stages of Hybrid Maize (Zea mays L.) as Affected by Different Levels of NPK in Silty Clay Loam Soil of Nepal

ABSTRACT Field experiments were conducted to investigate the effect of various levels of nitrogen, phosphorus, and potassium on the nutrient content of maize grain and stover and their uptake at different growth stages of hybrid maize in silty clay loam soil of Khumaltar, Lalitpur, Nepal, during summer of 2019 and 2020. Experiment was carried out in three factorial randomized complete block design with a total of 27 treatment combinations and replicated 3 times. Three factors were three levels of nitrogen (150, 180, and 210 N kg/ha), phosphorus (40, 60, and 80 P2O5 kg/ha), and potassium (40, 60, and 80 K2O kg/ha). Increasing nitrogen and potassium rates significantly (p < .05) increased total dry matter, grain yield, nutrient concentration, and accumulation of NPK in maize. On average, application of a higher rate of nitrogen (210 kg/ha) and potassium (80 kg/ha) produced grain yields of 10.95 t/ha and 10.54 t/ha, respectively, indicating higher uptake and higher grain yield. The average concentrations of N, P2O5, and K2O were 15.79, 9.56, and 3.77 g/kg in grain and 6.74, 4.17, and 10.46 g/kg in stover at maturity differentiated depending upon the rate of NPK applied. Nitrogen and phosphorus were accumulated mostly in grain (68–83%), whereas potassium was observed more in stover (64–77%). On average, 9.97 tons of maize grain removed 282.81 kg NPK/ha with a positive linear regression (R2) value of 0.89. The reference value of nutrient contents in maize crop obtained from this study can be used to estimate the time and amount of NPK removed from soil for better nutrient management.