Nitrogen Requirements Research Articles

Nitrogen requirements of first‐year small grains after alfalfa

AbstractSmall grains are commonly grown in rotation following alfalfa (Medicago sativa L.) in Utah and the Intermountain West, especially during drought years, as they require less irrigation than corn (Zea mays L.). Several studies have shown that corn following alfalfa rarely needs N fertilizer, yet few have evaluated the N needs of small grains. Objectives of this research were to determine whether N fertilizer is needed to economically optimize the yield and quality of first‐year soft white winter wheat (Triticum aestivum L.) following alfalfa and whether the response could be predicted. Fertilizer trials (four replications of up to 13 N rates) were conducted on 12 first‐year wheat sites in Utah during 2018–2019. Three sites in 2018 with spring soil nitrate concentrations ≥17 mg kg–1 required no N to improve yield. The remaining nine sites in 2019 with soil nitrate ≤13 mg kg–1 all had yield, test weight, and protein responses to fertilizer N. Economic optimum N rates for optimal yield, protein, and test weight across the nine sites in 2019 were 22 kg N ha–1 (18%) greater for split applications (fall and spring) compared with single spring N across various wheat/N price ratios. Delaying N applications until flag leaf decreased yield in 2019 provided no economic protein or test weight advantages. Results indicate that 96–147 kg N ha–1 (depending on price ratio) should be applied as a single application in the spring to first‐year soft white winter wheat following alfalfa only when spring soil nitrate is <17 mg kg–1.

Soil Nitrate Nitrogen Content and Grain Yields of Organically Grown Cereals as Affected by a Strip Tillage and Forage Legume Intercropping.

Reducing tillage intensity and increasing crop diversity by including perennial legumes is an agrotechnical practice that strongly affects the soil environment. Strip tillage may be beneficial in the forage legume–cereals intercropping system due to more efficient utilization of biological nitrogen. Field experiments were conducted on a clay loam Cambisol to determine the effect of forage legume–winter wheat strip tillage intercropping on soil nitrate nitrogen (N-NO3) content and cereal productivity in various sequences of rotation in organic production systems. Forage legumes (Medicago lupulina L., Trifolium repens L., T. alexandrinum L.) grown in pure and forage legume–winter wheat (Triticum aestivum L.) strip tillage intercrops were studied. Conventional deep inversion tillage was compared to strip tillage. Nitrogen supply to winter wheat was assessed by the change in soil nitrate nitrogen content (N-NO3) and total N accumulation in yield (grain and straw). Conventional tillage was found to significantly increase N-NO3 content while cultivating winter wheat after forage legumes in late autumn (0–30 cm layer), after growth resumption in spring (30–60 cm), and in autumn after harvesting (30–60 cm). Soil N-NO3 content did not differ significantly between winter wheat strip sown in perennial legumes or oat stubble. Winter wheat grain yields increased with increasing N-NO3 content in soil. The grain yield was not significantly different when comparing winter wheat–forage legume strip intercropping (without mulching) to strip sowing in oat stubble. In forage legume–winter wheat strip intercropping, N release from legumes was weak and did not meet wheat nitrogen requirements.

Assessment of morpho-physiological and quantitative and qualitative yield of Peppermint (Mentha piperita L.) under different irrigation regimes and application of different nitrogen fertilizer

Introduction Water and nitrogen fertilizer are major determinants of the level of agricultural production in the world, in addition to the quantity and quality of Medicinal plants are also effective. Iran's climate is mainly dry and semi-arid, in such a situation, where abnormal environmental stresses occur for plants. Improving crop yields in these stress conditions require good management of inputs (such as water and nutrients), their amount and type, and knowledge of physiological processes and plant defense mechanisms is essential. Water stress can significantly alter the metabolism of plants and reduce growth and photosynthesis and ultimately yield of plants. In this situation, effective management of water consumption in agriculture is an urgent necessity. In this regard, the use of agronomic techniques such as application of organic fertilizers or enhancement of soil biological conditions may be effective in reducing the effects of water stress and less use of chemical fertilizers for sustainable agriculture and human nutritional health. Also, intensive agriculture with the widespread use of chemical fertilizers, especially nitrogen can cause an increase in costs and environmental pollution. A key component of sustainable agriculture is use of organic fertilizers such as vermicompost and azocompost. Materials and methods In order to investigate the effects of water deficit stress and different nitrogen fertilizers on morphological, physiological traits, biological yield and essential oil percentage of peppermint, a experiment was conducted in a factorial arrangement in a randomized complete block de sign with three replications were carried out in 2018 at the field research station of the Agricultural Research Center of Tarbiat Modares University in Karaj (51 10’E, 33 44’ N, 1305.2 m above sea level). Experimental treatments consisted of three irrigation regimes (irrigation up to field capacity and after unloading 25, 40 and 55% water use in root zone, respectively) as the major factor and six fertilizer treatments based on nitrogen requirement respectively (100% chemical fertilizer, no fertilizer, 50% chemical + 50% azocompost, 100% vermicompost, 100% azocompost and 50% chemical fertilizer + 50% vermicompost) were as sub-factors. After field preparations, this area was divided into 54 experimental plots each of which were 2 m long with six rows, 0.2 m apart. Between all the main plots, a 3 m alley was kept to eliminate the influence of lateral water movement. Plant to plant distance in each row was 0.2 cm. Results Analysis of variance showed that the effect of all the experimental treatments and their interaction on all measured traits was significant. The results showed that mild and severe drought stress decreased plant height (18.2 and 42.92%) and biological yield (15.11 and 51.98%, respectively), while pigment, carotenoid, anthocyanin, proline and essential oil percentage increased. Nitrogen fertilizer application increased all measured traits. In most of the traits measured in this experiment, 50% chemical fertilizer and 50% vermicompost fertilizer were evaluated even better under severe water deficit conditions than other treatments. Conclusion: The results also showed that if the aim of planting peppermint is to improve the quality (essential oil percentage) of the plant by applying high water deficit stress, it can save more than 50% water consumption by producing the highest essential oil percentage. And vermicompost fertilizer can also be substituted for nitrogen chemical fertilizer to promote safe and sustainable

Optical-Sensor-Based Nitrogen Management in Oat for Yield Enhancement

The deficiency of nitrogen (N) in soil restricts agricultural productivity and its overdosage pollutes the atmosphere. Nitrogen is a vital component of protein, chlorophyll and various physiological processes. When it is applied at a recommended dose, it may be lost through fixation, leaching, volatilization and denitrification, etc. Therefore, there is a dire need to harmonize the supply of nitrogen according to crop and soil requirements. Under this situation, precision nitrogen management is one of the best options. GreenSeekerTM is an integrated optical sensor with a variable application rate and mapping system that measures crops’ nitrogen requirements. To ascertain the abovementioned facts, a research study was conducted at the National Agriculture Research Center, Islamabad, Pakistan, to examine the response of fodder oat to nitrogen management (N0 = control, N1 = 80 kg ha−1 basal dose, N2 = 40 + 40 kg ha−1 split doses, N3 = 40 kg ha−1 with one-time management with GreenSeekerTM and N4 = 20 kg ha−1 with two-time management with GreenSeekerTM) and seed rate (S1 = 80, S2 = 100, S3 = 120 and S4 = 140 kg ha−1). Data were recorded on the agronomic and physiological aspects of the crop and economic analysis was performed for GreenSeekerTM-based N application against the conventional recommended dose of nitrogen application. Mean values showed that greater number of tillers plant−1 (6), fresh weight (16572 kg) and photosynthetic rate (11.64 mmol m−2 s−1) were noted in the treatment N4 (20 kg ha−1 and two-time management with GreenSeekerTM). Greater plant height (70.8 cm) and leaf area (64.14 cm2) were recorded in treatment N2 (40 + 40 kg ha−1 split doses) as compared to the control. The effects of nitrogen on fodder oat were forecasted through NDVI. The results suggested that nitrogen treatment N4 (18 kg ha−1) managed by GreenSeeker in the PARC Oat cultivar produced the maximum NDVI value (0.68) at the booting stage among all treatments. The correlation of NDVI at the tillering and booting stages with green fodder yield was positive (R2 = 0.80). Therefore, the tillering and booting stages can be good depictive stages at early and later growth stages of fodder oat under the agro-climatic conditions of Islamabad, Pakistan. Based on the results, it is recommended to apply an initial dose of 20 kg ha−1 nitrogen along with two-time management with GreenSeekerTM for obtaining more green fodder yield in fodder oat. In Crux, with N1, a total of 80 kg ha−1 nitrogen was applied to achieve an estimated net profitability of USD 582.13. With N4, a total 58 kg ha−1 nitrogen was used to achieve a net profitability of USD 836.16; therefore, this treatment was found to be environmentally safe as compared to N1 (80 kg ha−1).

Hydrolysis of fish waste using fruit wastes of Ananas comosus and Carica papaya for the formulation of liquid fertilizers

Purpose Fish waste is a protein-rich source that can be used as a value-added product in the formulation of organic liquid fertilizers. This study carried out to investigate the utilizing potential of fruit wastes of Ananas comosus and Carica papaya that contain bromelain and papain as major proteases in order to hydrolyze fish waste proteins to fulfill plant nitrogen requirements. Method Proteases were extracted from A. comosus (leaves, crown, unripe fruit pulp, ripe fruit peels and pulp) and C. papaya (leaves, ripe fruit peels and unripe fruit peels). The optimum temperature and pH for the enzymatic activities were determined. Four liquid organic fertilizers were produced with hydrolyzed fish waste that enriched by adding Gliricidia sepium, Chromolaena odorata, Tithonia diversifolia, Mikania scandens and coconut husk-ash. Fertilizers were tested on the growth of Basella alba comparing with a standard fertilizer. Results Ananas comosus ripe fruit peels and the mixture of (A. comosus + C. papaya) showed the highest enzyme activities (0.33±0.02 and 0.36±0.01 U mL-1 enzyme respectively) at 55 oC and 70 oC. The optimum pH for all the studied extracts was 7.5 at 37 oC. The highest plant fresh and dry weights were recorded in the foliar-applied fertilizer produced by hydrolyzing the fish waste using A. comosus and C. papaya, showing no significant differences to the standard fertilizer. Conclusion Hydrolysis of fish waste using the fruit wastes of A. comosus and C. papaya could be effectively used as an organic fertilizer for the growth of B. alba that leads towards sustainable waste management.

Impact of Nitrogen Addition on Wine Fermentation by S. cerevisiae Strains with Different Nitrogen Requirements.

In modern oenology, supplementation of nitrogen sources is an important strategy to prevent sluggish or stuck fermentation. The present study thoroughly determined the effect of nitrogen addition timing and nitrogen source type on fermentation kinetics and aroma production, carried out by yeast strains with low and high nitrogen requirements. The results revealed that yeast strains with different nitrogen requirements have divergent reactions to nitrogen addition. Nitrogen addition clearly shortened the fermentation duration, especially for the high-nitrogen-demanding yeast strain. Nitrogen addition at 1/3 fermentation was the most effective in terms of fermentation activity, nitrogen assimilation, and production of acetate esters. Interestingly enough, yeast cells preferentially took up amino acids related to fermentative aroma synthesis with the addition at 2/3 fermentation. The addition of nitrogen sources also largely affected the production of important metabolites. Generally speaking, acetic acid, glycerol, and succinic acid reduced with the supplementation of nitrogen sources. The results revealed significant application importance for the winemaking industry.

Nutrient requirement and use efficiency of rice (Oryza sativa L.) as influenced by graded levels of customized fertilizer

Balanced nutrient application is an important concern to minimize fertilizer use in crop culture. Field experiments were conducted during kharif 2017 and 2018 to find out the best level of NPK fertilizer for rice with two varieties of rice of same duration (130-135 days). Three grades of customized fertilizers (250, 350 and 450 kg ha−1) along with 100% RDF (Recommended dose of fertilizer) and absolute control constituted the treatment variables. The results revealed that the grades of customized fertilizer (CF) influenced the yield and uptake of nutrients. Application of CF @ 450 kg ha−1 was found to be significantly superior over absolute control and 100% RDF with respect to yield and uptake of nutrients, and found on par with all other grades of CF (250 and 350 kg ha−1). Applying 250 kg ha−1 of CF recorded higher agronomic efficiency (AE), apparent recovery efficiency (ARE) and partial factor productivity (PFP) for phosphorus (P) and potassium (K) but higher AEn, AREn and PFPn in 450 kg ha−1 of CF. The higher utilization efficiency of nitrogen (UEn) of 43.05%, phosphorus (UEp) of 181.88% and potassium (UEk) of 34.40% were recorded in 250 kg ha−1 of CF. The CF @ 450 kg ha−1 recorded higher nitrogen and phosphorus requirement (NR and PR) i.e., 2.65 and 0.61 kg’s, respectively. Whereas, potassium requirement (KR) was higher in 100% RDF. Higher response yard stick (RYS) of 5.33 was recorded in 250 kg ha−1 of CF compared to other grades of CF, 100% RDF and absolute control.

Quantifying the Nitrogen Requirement of Castor Cultivars in Post Monsoon Season on Alfisols

Aim: The experiment is aimed at quantifying the nitrogen requirement and identifying suitable hybrids and varieties of castor to be grown during post monsoon season on Alfisols in Telangana
 Study Design: Split plot design.
 Place and Duration of Study: Regional Agricultural Research Station, Professor Jayashankar Telangana State Agricultural University, Palem, Telangana state, India during post monsoon season of 2010-11 and 2011-12.
 Methodology: The study consisted of four N levels (0, 40, 80 kg and 120 kg N ha-1) in main plots and five cultivars (DCH-177, PCH-111, GCH-4, Haritha and 48-1)in sub plots. The growth parameters, yield attributes, seed yield, water use efficiency, economic returns, correlation and regression were studied.
 Results: The pooled data indicated that significantly taller plants with more no. of branchesplant-1, longer and effective spikes thus seed yield of castor were observed due to application of 80 kg Nha-1 and 120 kg Nha-1. However, application of 120 kg N ha-1 resulted in greater net returns (USD 1049 ha-1) and also returns per rupee invested (1.66). The results further showed that the castor hybrids PCH-111 (1900 kg/ha) and DCH-177 (1809 kg/ha) produced similar yield, but, both significantly outyielded over other cultivars. The performance of hybrids was superior to the varieties. A highly significant positive correlation was observed for seed yield with no. of branches/plant, total and effective spike length.
 Conclusion: The cultivation of castor hybrids either PCH-111 or DCH-177 under N supply of 120 kg N ha-1 would help to realize higher yields, water use efficiency and income from post monsoon season castor on Alfisols.

Global option space for organic agriculture is delimited by nitrogen availability.

Organic agriculture is widely accepted as a strategy to reduce the environmental impacts of food production and help achieve global climate and biodiversity targets. However, studies concluding that organic farming could satisfy global food demand have overlooked the key role that nitrogen plays in sustaining crop yields. Using a spatially explicit biophysical optimization model that accounts for crop growth nitrogen requirements, we show that, in the absence of synthetic nitrogen fertilizers, the production gap between organic and conventional agriculture increases as organic agriculture expands globally (with organic producing 36% less food for human consumption than conventional in a fully organic world). Yet, by targeting both food supply (via a redesign of the livestock sector) and demand (by reducing average per capita caloric intake), public policies could support a transition towards organic agriculture in 40-60% of the global agricultural area even under current nitrogen limitations thus helping to achieve important environmental and health benefits.

Nutritional contribution of seaweed Ulva lactuca single-cell detritus and microalgae Chaetoceros calcitrans to the growth of the Pacific oyster Crassostrea gigas

The Pacific oyster Crassostrea gigas (Thunberg, 1793) is the most cultivated bivalve in the world. Nonetheless, the massive production of microalgae as feed represents a substantial cost during laboratory production stages. The use of single cell detritus (SCD) from seaweed Ulva lactuca, cultivated in fish farm effluents, has been proposed as an alternative to microalgae Chaetoceros calcitrans in oyster culture, with the aim of reducing microalgae production costs. Seaweed meal was subjected to an acid and enzymatic digestion process to obtain SCD particles smaller than 20 μm to feed the oysters. Five levels of SCD (w:w) replacing microalgae were evaluated: 0, 25, 50, 75, and 100% in a feeding assay of 5 weeks. At the end of the experiment, growth parameters, condition index, enzymatic activity in the digestive gland (amylase, protease, lipase, and aminopeptidase) were analysed. In addition, during the course of the experiment, the stable isotope ratio of nitrogen (δ15N) was analysed at natural abundance levels in both feed sources and in the mantle tissue of oysters reared on different feeding regimes. Contribution to growth was estimated using an isotope mixing model. Better growth (74 to 94% dry weight gain) and condition indexes (81–75) were observed in oysters fed on experimental regimes having from 0 to 50% substitution of microalgae with SCD, showing no significant differences among them. Oysters under the latter treatments also showed similar enzymatic activity for amylase, alkaline-protease, and lipase. At higher substitution levels of microalgae (75–100%), oysters presented lower growth (13 to 34% dry weight gain) and poor condition indexes (<60); 100% of SCD also elicited higher amylase, alkaline-protease, and lipase activities, whereas (Leu) aminopeptidase N activity was lower. The digestive capacity of lipase was improved in oysters fed with 50 and 75% levels of SCD. Isotopic equilibrium for nitrogen (δ15N) was reached by day 14 in the 50% substitution treatment. Metabolic turnover rates of nitrogen decreased (0.15 to 0.08 day−1) whereas elemental half times in tissue increased (4.1 to 8.2 days) with higher microalgae substitution. Oysters under treatment with 50% microalgae substituted by SCD incorporated similar amounts of dietary nitrogen and dry matter from the microalgal biomass as from SCD to meet the nitrogen requirement for oyster growth. In conclusion, results suggest that SCD from U. lactuca can substitute up to 50% of microalgae C. calcitrans without modifying C. gigas productivity.

Effects of clipping on the nitrogen economy of four Triticum species grown in a Mediterranean environment

• N uptake in old and ancient wheats was not affected by dual-purpose use when the N removed by clipping was considered. • Both HI and NHI increased following clipping. • Einkorn was the species whose N economy suffered the least from dual-purpose utilization. • A high tillering capacity represented a desirable trait for both pre- and post clipping N uptake in dual-purpose cereals. • Cultivars with high biomass and N at anthesis and a low sink were at risk of N losses between anthesis and maturity. Dual-purpose utilization (herbage + grain) of ancient wheats and old durum wheat cultivars provides an interesting option for mixed farming systems in Mediterranean environments. Interest towards these species is partly due to their low nitrogen (N) requirements, but little information is available about their N economy, particularly under dual-purpose utilization. In this two-year field trial carried out in Sardinia (Italy), we assessed whether the morpho-physiological differences between emmer, einkorn, durum and Khorasan wheat translated into different N economies, and whether these economies were differentially impacted by dual-purpose utilization. At both clipping and anthesis, biomass accumulation played a key role in the genotypic variability in N uptake. At clipping, einkorn cultivars had produced the greatest amount of biomass and removed the greatest amount of N (74 kg ha −1 ) thanks to their late terminal spikelet; whereas Cappelli, Khorasan and Padre Pio showed the greatest biomass production and N uptake at anthesis (212 kg ha −1 ) owing to their tallness and morphology. The large genotypic variation observed in total N uptake at anthesis levelled off at maturity, mainly because of the N losses occurring at the canopy level after anthesis in cultivars Cappelli, Khorasan and Padre Pio. On average, clipped crops showed a lower (by about 46 kg ha −1 ) total N uptake at maturity compared with unclipped crops, but dual-purpose utilization did not negatively affect the N uptake if the N removed by clipping was taken into account. Clipping did not negatively affect N partitioning to the grain as the N harvest index increased after clipping as a consequence of the increased harvest index.

Estimating nitrogen, phosphorus, potassium, and sulfur uptake and requirement in soybean

Estimation of crop nutrient demand, seed nutrient removal, and nutrient use efficiency (yield to nutrient uptake ratio) are crucial for pursuing both balanced nutrition and more sustainable farming systems. However, the estimation of the nutrient requirements as the nutrient uptake per unit of seed yields is impaired in many situations due to the narrow variation of the dataset used to obtain these values or by the overgeneralization of considering a constant value for the nutrient demand at varying yield levels. Past studies focused on other crops and using linear models for estimation of the nutrient requirements, but not yet for soybeans (Glycine max L.). The aims of this research study were to: (i) quantify nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) requirements in soybean and (ii) compare linear and non-linear (spherical) models in their relationship between plant and seed nutrient content all relative to seed yield at varying probabilities utilizing quantile regression. A large dataset from different studies conducted between 2009–2018 period, including data of seed yield, total biomass at physiological maturity, and N, P, K, and S uptake. Soybean seed yield ranged from 955 to 6525 kg ha−1, aboveground biomass from 1990 to 15,814 kg ha−1, and harvest index from 0.16 to 0.57. On average, nutrient uptake was 261 kg N ha−1, 25 kg P ha−1, 133 kg K ha−1, and 16 kg S ha−1 (N:P:K:S ratio = 17:1.6:8.5:1), while nutrient content in seeds averaged 191 kg N ha−1, 17 kg P ha−1, 54 kg K ha−1, and 9 kg S ha−1 (N:P:K:S ratio = 21:1.8:5.8:1). The spherical model described better than the linear model the relationship between plant nutrient uptake or nutrient content in seeds with seed yield in soybean, and thus, nutrient requirements per unit of yield decreased as seed yield increased. A relationship between nutrient internal efficiency and seed yield for the different percentiles as determined by the non-linear quantile regression offered probabilistic values for estimating nutrient uptake in soybean, providing useful information for obtaining more reliable estimates of nutrient balances at the system-level.

High throughput identification of miRNAs reveal novel interacting targets regulating chickpea-rhizobia symbiosis

Legumes developed symbiotic associations to meet its nitrogen requirement. The nitrogen fixation takes place in root nodules which involves bacterial colonization, organogenesis and nitrogen fixation. In order to unravel the miRNA mediated regulation of chickpea symbiosis, one microRNA and four parallel analysis of RNA ends (PARE) libraries were sequenced. Analysis of microRNA library identified a set of 91 miRNAs comprising of 84 conserved and 7 novel miRNAs. Additionally, PARE library analysis revealed 564 genes being targeted by 85 miRNAs. Phylogenetic analysis of the precursor sequences of the 91 miRNAs was carried out which revealed their ancestral relationships. Further, the mechanism of miRNAs biogenesis was predicted using the miRNAs information from other legumes. Reads from the nodule library were mapped to bacterial genomes to predict bacterial-encoded small RNAs. Real time expression analysis was used to validate the antagonistic expression pattern of important miRNA-mRNA target pairs. Four candidate miRNAs were selected for in planta study based on the antagonistic expression profiling as well as the novelty of their respective targets. miR171f, miR172c, miR394 and miR1509 targeted nodulation receptor kinase, Apetala2, histidine phosphotransferase, adenylate kinase respectively and were ectopically expressed in chickpea roots. The overexpression lines showed significant change in nodule numbers, the miR172c, miR394 and miR1509 resulted in an increase in nodule number whereas, miR171f overexpression led to a decrease in nodule number. Our analysis lays the foundation for functional characterization of novel miRNAs and their respective target pairs which control nodulation in chickpea and other leguminous crops.

Legume-Modified Rotations Deliver Nutrition With Lower Environmental Impact

Introducing legumes to crop rotations could contribute toward healthy and sustainable diet transitions, but the current evidence base is fragmented across studies that evaluate specific aspects of sustainability and nutrition in isolation. Few previous studies have accounted for interactions among crops, or the aggregate nutritional output of rotations, to benchmark the efficiency of modified cropping sequences. We applied life cycle assessment to compare the environmental efficiency of ten rotations across three European climatic zones in terms of delivery of human and livestock nutrition. The introduction of grain legumes into conventional cereal and oilseed rotations delivered human nutrition at lower environmental cost for most of the 16 impact categories studied. In Scotland, the introduction of a legume crop into the typical rotation reduced external nitrogen requirements by almost half to achieve the same human nutrition potential. In terms of livestock nutrition, legume-modified rotations also delivered more digestible protein at lower environmental cost compared with conventional rotations. However, legume-modified rotations delivered less metabolisable energy for livestock per hectare-year in two out of the three zones, and at intermediate environmental cost for one zone. Our results show that choice of functional unit has an important influence on the apparent efficiency of different crop rotations, and highlight a need for more research to develop functional units representing multiple nutritional attributes of crops for livestock feed. Nonetheless, results point to an important role for increased legume cultivation in Europe to contribute to the farm and diet sustainability goals of the European Union's Farm to Fork strategy.

Nutrient deficiency enhances the rate of short-term belowground transfer of nitrogen from Acacia mangium to Eucalyptus trees in mixed-species plantations

While a recent study showed that significant amounts of the nitrogen (N) requirements of young Eucalyptus trees can be provided by nitrogen-fixing trees (NFTs) in mixed-species plantations through short-term belowground N transfer, the consequences of soil fertility on this facilitation process remain unknown. We assessed the effect of fertilization on the percentage of N derived from transfer (%NDFT) from Acacia mangium trees to Eucalyptus trees in mixed-species plantations. A complete randomized block design with two treatments (fertilized vs unfertilized) and three blocks was set up in mixed-species plantations of A. mangium and Eucalyptus in Brazil, with 50% of each species at 2.5 m × 2.5 m spacing. Collection of litterfall and forest floor made it possible to estimate the annual N release from forest floor decomposition between 46 and 58 months after planting, close to harvest age. 15N-NO3- was injected into the stem of one dominant Acacia tree in each plot, 58 months after planting. The x(15N) values of Acacia and Eucalyptus fine roots sampled within 1.8 m of the labelled A. mangium tree were determined at 7, 14, 30 and 60 days after labelling. The x(15N) values in wood, bark, branch and leaf samples were also determined for the 6 labelled Acacia trees and their two closest Eucalyptus neighbours, just before and 60 days after labelling. The amount of N released from forest floor decomposition was 31% higher in fertilized (F+) than in unfertilized (F-) plots. Sixty days after labelling, the aboveground compartments of Eucalyptus trees were significantly 15N enriched in both treatments. The x(15N) values of Acacia fine roots were higher than background values from 7 days after labelling onwards in F+ and 30 days after labelling in F-. The x(15N) values of Eucalyptus fine roots were higher than background values in both treatments, from 30 days after labelling onwards. Mean %NDFT values were 18.0% in F+ and 33.9% in F- over the first 60 days after labelling, and 22.8% in F+ and 67.7% in F- from 30 to 60 days after labelling. Fertilization decreased short-term transfer belowground of N from Acacia trees to Eucalyptus trees. Our study suggests that belowground facilitation processes providing N from NFTs to Eucalyptus trees in mixed-species plantations are more pronounced in low-fertility soils than in nutrient-supplied stands.

Defining the physiological determinants of low nitrogen requirement in wheat.

Nitrogen (N) is a major nutrient limiting productivity in many ecosystems. The large N demands associated with food crop production are met mainly through the provision of synthetic N fertiliser, leading to economic and ecological costs. Optimising the balance between N supply and demand is key to reducing N losses to the environment. Wheat (Triticum aestivum L.) production provides food for millions of people worldwide and is highly dependent on sufficient N supply. The size of the N sink, i.e. wheat grain (number, size, and protein content) is the main driver of high N requirement. Optimal functioning of temporary sinks, in particular the canopy, can also affect N requirement. N use efficiency (i.e. yield produced per unit of N available) tends to be lower under high N conditions, suggesting that wheat plants are more efficient under low N conditions and that there is an optimal functioning yet unattained under high N conditions. Understanding the determinants of low N requirement in wheat would provide the basis for the selection of genetic material suitable for sustainable cereal production. In this review, we dissect the drivers of N requirement at the plant level along with the temporal dynamics of supply and demand.

A novel ammoniation treatment of barley as a strategy to optimize rumen pH, feed degradability and microbial protein synthesis in sheep.

BACKGROUNDMeeting the energy and nitrogen (N) requirements of high‐performing ruminants at the same time as avoiding digestive disturbances (i.e. rumen acidosis) is a key priority in ruminant nutrition. The present study evaluated the effect of a cereal ammoniation treatment, in which barley grains are combined with urea and enzymes that catalyze the conversion of urea to ammonia to optimize rumen function. Twelve rumen cannulated sheep were randomly divided into two groups and fed a diet containing 60% of ammoniated barley (AMM) or untreated barley supplemented with urea (CTL) to investigate the impact on rumen fermentation and feed utilization.RESULTSAMM had higher total N content and effective rumen degradable N than untreated barely. AMM sheep had a consistently higher rumen pH throughout the day (6.31 versus 6.03) and tended to have a lower post‐prandial ammonia peak and higher acetate molar proportion (+5.1%) than CTL sheep. The rumen environment in AMM sheep favored the colonization and utilization of agro‐industrial by‐products (i.e. orange pulp) by the rumen microbes leading to a higher feed degradability. AMM sheep also had higher total tract apparent N digestibility (+21.7%) and urinary excretion of purine derivatives (+34%), suggesting a higher N uptake and microbial protein synthesis than CTL sheep.CONCLUSIONThe inclusion of AMM in the diet of ruminants represents a valid strategy for maintaining rumen pH within a physiological range and improving N utilization by the rumen microbes, which could have positive effects on the health and productivity of animals in intensive production systems. These findings warrant further studies under conventional farm conditions. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Deep maxima of phytoplankton biomass, primary production and bacterial production in the Mediterranean Sea

Abstract. The deep chlorophyll maximum (DCM) is a ubiquitous feature of phytoplankton vertical distribution in stratified waters that is relevant to our understanding of the mechanisms that underpin the variability in photoautotroph ecophysiology across environmental gradients and has implications for remote sensing of aquatic productivity. During the PEACETIME (Process studies at the air-sea interface after dust deposition in the Mediterranean Sea) cruise, carried out from 10 May to 11 June 2017, we obtained 23 concurrent vertical profiles of phytoplankton chlorophyll a, carbon biomass and primary production, as well as heterotrophic prokaryotic production, in the western and central Mediterranean basins. Our main aims were to quantify the relative role of photoacclimation and enhanced growth as underlying mechanisms of the DCM and to assess the trophic coupling between phytoplankton and heterotrophic prokaryotic production. We found that the DCM coincided with a maximum in both the biomass and primary production but not in the growth rate of phytoplankton, which averaged 0.3 d−1 and was relatively constant across the euphotic layer. Photoacclimation explained most of the increased chlorophyll a at the DCM, as the ratio of carbon to chlorophyll a (C:Chl a) decreased from ca. 90–100 (g:g) at the surface to 20–30 at the base of the euphotic layer, while phytoplankton carbon biomass increased from ca. 6 mg C m−3 at the surface to 10–15 mg C m−3 at the DCM. As a result of photoacclimation, there was an uncoupling between chlorophyll a-specific and carbon-specific productivity across the euphotic layer. The ratio of fucoxanthin to total chlorophyll a increased markedly with depth, suggesting an increased contribution of diatoms at the DCM. The increased biomass and carbon fixation at the base of the euphotic zone was associated with enhanced rates of heterotrophic prokaryotic activity, which also showed a surface peak linked with warmer temperatures. Considering the phytoplankton biomass and turnover rates measured at the DCM, nutrient diffusive fluxes across the nutricline were able to supply only a minor fraction of the photoautotroph nitrogen and phosphorus requirements. Thus the deep maxima in biomass and primary production were not fuelled by new nutrients but likely resulted from cell sinking from the upper layers in combination with the high photosynthetic efficiency of a diatom-rich, low-light acclimated community largely sustained by regenerated nutrients. Further studies with increased temporal and spatial resolution will be required to ascertain if the peaks of deep primary production associated with the DCM persist across the western and central Mediterranean Sea throughout the stratification season.

Manure and inorganic fertilization impacts on soil nutrients, aggregate stability, and organic carbon and nitrogen in different aggregate fractions

ABSTRACT Manure application can enhance soil fertility and crop yield; however, knowledge of optimum application rates of manure is needed to prevent negative impacts on soils and environment. This study was aimed to compare the long-term effects of manure and inorganic fertilizer application at different rates on soil nutrients, aggregate stability, organic carbon, and nitrogen in different aggregate size fractions. The experiment was conducted on a long-term manure site under a randomized complete block design with six treatments: three manure [low manure (LM; application based on phosphorous requirement), medium manure (MM; application based on nitrogen requirement), high manure (HM; two times prescribed nitrogen rate)], two chemical fertilizer [medium fertilizer (MF; suggested inorganic fertilizer rate), high rate of fertilizer (HF)], and control (CK; no manure nor fertilizer). Manure application maintained soil pH, improved nutrient availability and aggregate stability compared to the CK. The HM treatment increased aggregate-associated soil organic carbon (SOC) and total nitrogen (TN) concentration by 40 to 50% in all size fractions as compared to the CK. Further, HM increased particulate organic matter (POM) by 1.2 times as compared to the CK, while inorganic fertilizer application did not alter these parameters compared to the CK.

Nitrogen Management Based on Visible/Near Infrared Spectroscopy in Pear Orchards

The timely estimation of nitrogen (N) requirements is essential for managing N fertilizer application in pear orchards. Visible/near infrared spectroscopy is a non-destructive and effective technique for real-time assessment of leaf N concentration, but its utility for decisions about fertilizer application in the pear orchards remains to be determined. In this study, we used leaf spectroscopy to determine leaf N concentration, used this value to calculate the amounts of N required for supplementary fertilization, and then evaluated the effects of the application. Over the two-year study, Cuiguan pear trees were treated with N at the following rates: 0 (N0), 100 (N1), 200 (N2), 300 (N3), and 400 (N4) g N per tree, regarded as five “controlled” N application rates. Another four “regulatory” treatments (Nr1-4) were fertilized as the “controlled” N application rates the first year, then given adjusted N application by topdressing as calculated using the N concentrations inferred from visible/near infrared spectroscopy data the second year. A model (R2 = 0.82) was established the first year to relate leaf spectra and N concentration using a partial least squares regression with full bands (350–2500 nm). The amount of N in the topdressing for the supplemental treatments was determined using the predicted leaf N concentration and the topdressing calculation method adapted from the N balance formula. Results showed that adjusted N applications of the Nr1 and Nr2 increased yield by 26% and 23%, respectively, over the controlled treatments N1 and N2. Although treatments Nr3 and Nr4 did not increase yield significantly over N3 and N4, the partial factor productivity of nitrogen in Nr4 was higher than the N4. The transverse diameter of fruit from Nr1 trees was significantly higher than from N1 trees, while the longitudinal diameter of fruit from Nr1, Nr2, and Nr3 trees was significantly higher than from N1, N2 and N3 trees, suggesting that fruit longitudinal growth and single-fruit weight is stimulated by adjusted N applications. However, the soluble solids in fruit from trees receiving adjusted N were not significantly greater than in fruit from non-supplemented trees. In conclusion, our results illustrate that regulatory N management contributes to fruit yield and quality especially in the nitrogen deficiency condition and improves the nitrogen use efficiency in nitrogen surplus. The N prediction model established using the nondestructive visible/near infrared spectroscopy is convenient and economical.