Nitrogen Utilization Efficiency Research Articles

Evaluating Suitable Rootstocks for Grafting in Organic Pepper System

Organic farming systems are often plagued with challenges such as nutrient stress complexing with other biotic and abiotic issues. These issues can significantly affect the growth and productivity of vegetable crops, including peppers (Capsicum spp.). Grafting with suitable rootstocks is a promising technique to address these challenges and improve the growth and productivity of peppers in low-input systems. In the United States, grafting is not as commonly practiced in pepper as compared with other solanaceous and cucurbit crops, in part because of limited availability of rootstocks. This study examined promising rootstocks with demonstrated disease resistance and further explored their suitability for organic systems under normal and reduced fertilization. A hybrid Italian sweet pepper ‘Mama Mia Giallo’ was used as scion and grafted onto four different rootstocks and grown in a greenhouse in summer with natural heat stress. The plants received organic fertilizer weekly or biweekly for a period of 5 weeks. Results showed that grafting plants with the rootstocks ‘CM-334’, ‘YC-207’, ‘Keystone Resistant Giant’, and ‘Scarface’ resulted in similar or improved growth relative to nongrafted and self-grafted plants under normal and reduced fertilization. The rootstocks showed promising traits that could be explored in further stress tolerance studies. Specifically, ‘YC-207’-grafted plants showed higher nitrogen utilization efficiency, shoot nitrate content, and phosphorous content as well as higher stomatal conductance, transpiration, and electron transport rate, which is indicative of stress tolerance. ‘YC-207’-grafted plants also had lower malondialdehyde content, indicating less oxidative damage to the cell membrane. ‘CM-334’-grafted plants showed higher antioxidant activity, nitrate reductase (NR) activity, and shoot nitrate content. This study provides evidence of the value of evaluating potential rootstocks and explores grafting as a promising technique for pepper crop to improve plant growth and performance under organic systems.

DETERMINATION OF NITROGEN UTILISATION AND NITROGEN UPTAKE EFFICIENCY OF SOME WHEAT GENOTYPES UNDER LIMITED NITROGEN CONDITIONS

Wheat is one of the most important human foods in Turkey and the most important nutrient of wheat plant is nitrogen. Since the green revolution in wheat variety breeding, high nitrogen high yielding varieties have been bred. Nitrogen resources of our world are limited, the use of excess nitrogen fertilisers for years has caused environmental pollution. It is also one of the important costs in wheat farming. There is a need to breed new wheat varieties that will reduce the use of nitrogen fertiliser. In order to reduce the damage to the environment and economic damage to the producer, it is important to breed high yielding varieties that require less nitrogen fertiliser. Otherwise, the cost of nitrogen fertiliser and the depletion of its reserve will negatively affect wheat production. A total of 7 genotypes including 4 local bread wheat genotypes, 2 durum wheat varieties (svevo, fırat93), 1 local siyez wheat collected from the villages of the Southeastern Anatolia region which is the homeland of wheat plant were used. The experiment was established according to split-plot design with 4 nitrogen doses and four replications. Nitrogen uptake efficiency and nitrogen utilisation efficiency were inversely proportional to nitrogen dose and nitrogen uptake efficiency increased as nitrogen dose decreased. Increasing nitrogen doses had an inverse effect on nitrogen uptake efficiency and the nitrogen dose with the highest nitrogen uptake efficiency was in the lowest nitrogen dose application. The genotype with the highest value among the local genotypes was GYE4.

Analysis of nitrogen flow in the Yellow River Basin over a long time series.

Since the Industrial Revolution, human activities have led to increased nitrogen (N) inputs, causing excess N in the Yellow River Basin (YRB) and leading to various environmental issues. Based on the basic statistical data and related parameters of the YRB from 2000 to 2019, an N flow model was characterized using the full nitrogen flow analysis (FNFA) and the emission factor method to analyze the characteristics of N inputs and outputs in the YRB. The results revealed that over the past 20years, both the total N inputs and outputs in the YRB have shown a significant increasing trend. Specifically, the total N input rose from 12,806.69 to 18,553.42 Gg, while the total output increased from 9250.93 to 12,955.0 Gg. Among the subsystems, the industrial and cropland subsystems were the largest contributors to the N balance, accounting for 28.30% and 26.22% of total N input and 40.48% and 26.23% of total N output, respectively. Overall nitrogen utilization efficiency (NUE) across the subsystems requires improvement, particularly within the cropland subsystem, which exhibited an NUE ranging from 25.67% to 36.10%. In contrast, the livestock subsystem had only half the NUE of the cropland subsystem. High emissions and inefficient N utilization have led to a continuous increase in environmental N loads, particularly in atmospheric N loads. Additionally, the life cycle assessment (LCA) of industrial N revealed that a substantial amount of N was enriched in the atmosphere. These findings provide a scientific basis for regulating N inflow and outflow within watershed areas and for formulating more rational integrated management strategies for N.

Enhancement of nitrogen transformation in media-based aquaponics systems using biochar and zerovalent iron

Aquaponics combines aquaculture and hydroponics, offering methods to produce fish and plants. However, optimization of its nitrogen transformation processes, which would lead to higher nitrogen utilization efficiency (NUE) and lower nitrous oxide (N2O) emission, is still a daunting challenge. This study investigated these issues by using biochar and zerovalent iron (ZVI) with low (LD) and high (HD) doses. Results showed that LD improved NUE by 15%, reaching 57%, along with a significant 36% reduction in N2O emissions. Conversely, denitrifying bacteria were disturbed in HD due to incomplete denitrification, resulting in higher N2O emissions. Microbial analysis showed that the abundance of denitrifying bacteria increased from 12% to 24% in LD, compared with the control, leading to lower N2O emissions and optimized nitrogen cycling. These findings suggested that using the appropriate proportion of biochar and ZVI would be a promising approach to enhance the sustainability and productivity of aquaponics systems.

Using Milk Urea to Evaluate Production, Efficiency of Nitrogen Utilization and Urinary Nitrogen Excretion During The Lactation In Dairy Cows

Abstract The aim of this study was to use milk urea to evaluate production parameters, efficiency of nitrogen utilization, and urinary nitrogen excretion during lactation in Holstein dairy cows. Cows in the 1st lactation phase compared to the 2nd and 3rd lactation phases showed: increase (P < 0.05) in daily milk yield; decrease (P < 0.05) in fat and protein content in milk; decrease in milk urea content (P < 0.05); with a lower individual number of animals (31% of dairy cows in the 1st stage of lactation, 39 % of dairy cows in the 2nd stage of lactation, and 44 % of dairy cows in the 3rd phase of lactation) with an above-limit milk urea content (35.0 ± 4.7; 34.9 ± 4.1, 34.8 ± 4.1 mg.dl-1); decreased urinary nitrogen excretion (P < 0.05); and efficiency of nitrogen utilization from feed to milk (P < 0.05). According to the phase of lactation, the efficiency of nitrogen utilization decreased and urinary nitrogen excretion increased with increasing milk urea content.

Effect of Sprouted Barley on Performance, Nutrient Digestibility, Nitrogen Utilization, Blood Markers and Economic Efficiency in Lambs

Background: This study aimed to investigate the effects of adding sprouted barley in the diet of lambs on growth performance, digestibility, nitrogen utilization, hematological and biochemical blood parameters and economic evaluation over 75 days. Methods: Thirty-six healthy 3-month-old Awassi lambs were used in this experiment. All lambs were individually divided into four dietary treatments with nine lambs each (T1 to T4: lambs receiving 0%, 25%, 50% and 75% sprouted barley as a replacement for the traditional diet, respectively). The growth performance, dry matter intake and dry matter excretion were assessed. The digestibility of the ingested dry matter and nitrogen, nitrogen balance, blood health markers, hematological and blood biochemical and economic evaluation were estimated. Result: Lambs fed T3 had a lower body weight on day 75 than those fed the other dietary treatments, with weight gain also being reduced for those fed sprouted barley during both the 45-75 and 1-75 day period. Feed intake generally increases with the sprouting of barley, resulting in a higher feed-to-gain ratio. White blood cell count and hemoglobin concentration reduced in lambs receiving T3 and T4. Total protein, globulin, triglyceride and glucose levels decreased in lambs receiving T3 and T4, whereas total cholesterol and HDL increased. Urea and ALT levels were lower in lambs fed sprouted barley. Sprouted barley had the highest dry matter content and nitrogen digestibility. Economic evaluations, including the profit rate, relative economic efficiency and investment rate, were higher. Overall, this experiment suggests that sprouting barley at 25% (T2) had no negative effect on the hematological and blood biochemical parameters of lambs, whereas economic evaluation indicators were higher at T2. The inclusion of sprouted barley resulted in the highest nitrogen balance and digestibility of dry matter and nitrogen. However, its effects on growth performance require further investigation.

Enhanced nitrogen fixation and Cd passivation in rhizosphere soil by biochar-loaded nitrogen-fixing bacteria: Chemisorption and microbial mechanism

This study developed a biochar-loaded Ac material and clarified its chemical and microbial mechanisms for cadmium (Cd) immobilization and plant growth promotion. Results showed that biochar-loaded nitrogen-fixing bacteria (Azotobacter chroococcum; BAc) enhanced Cd adsorption by forming stable complexes with bacterial secretions and activating biochar functional groups. Compared with BC and Ac, after BAc application, Ac successfully colonized the lettuce rhizosphere, tagged with green fluorescent protein. It improved plant nitrogen by 47.39–72.47 % and increased root and shoot biomass by 50.35–107.32 % through nitrogen fixation and amino acid release. BAc reduced soil Cd bioavailability by 16.67–46.42 % and Cd accumulation in root and shoot by 14.28–69.74 %. This occurred through increasing soil pH and converting exchangeable Cd to carbonate-bound and Fe/Mn oxide-bound fractions. Importantly, BAc improved the rhizosphere nutrient environment and promoted the deterministic assembly of the rhizosphere microbial community. It also increased microbial diversity and attracted taxa like Actinomycetales (7.59 %), Solirubrobacteriales (5.17 %), Rhizobiales (5.17 %), and Sphingomonadales (5.17 %), all associated with nitrogen fixation, plant growth promotion, and Cd immobilization. Structural equation modeling (SEM) confirmed that BAc increased nitrogen utilization efficiency in lettuce and facilitated biotic immobilization of soil Cd by optimizing the microbial structure. This study provides insights into how biochar-loaded Ac improve plant growth and control soil Cd pollution.

Slow-Release Fertilisers Control N Losses but Negatively Impact on Agronomic Performances of Pasture: Evidence from a Meta-Analysis

High nitrogen (N) losses and low nitrogen utilisation efficiency (NUE) of conventional-nitrogen fertilisers (CNFs) are due to a mismatch between N-delivery and plant demand; thus, slow-release N fertilisers (SRNFs) are designed to improve the match. A quantitative synthesis is lacking to provide the overall assessment of SRNFs on pasture. This meta-analysis analyses application rate and type of SRNFs on N losses and agronomic performances with 65 data points from 14 studies in seven countries. Standardized mean difference of SRNFs for nitrate leaching losses and N2O emission were −0.87 and −0.69, respectively, indicating their effectiveness in controlling losses. Undesirably, SRNFs had a more negative impact on dry matter (DM) yield and NUE than CNFs. Subgroup analysis showed that SRNF type and application rate had an impact on all tested parameters. The biodegradable coating-type of SRNF outperformed other types in controlling N losses and improving agronomic performances. High application rates (>100 kg N ha−1) of SRNFs are more effective in controlling N losses. In conclusion, SRNFs are more conducive to controlling N losses, but they showed a negative impact on yield and NUE in pasture. Further studies are recommended to assess the efficacy of SRNFs developed using advanced technologies to understand their impact on pastoral agriculture.

Association of nitrogen utilisation efficiency with sustenance of reproductive stage nitrogen assimilation, transcript abundance and sequence variation of nitrogen metabolism genes in rice (Oryza sativa L.) sub-species

Association of nitrogen utilisation efficiency with sustenance of reproductive stage nitrogen assimilation, transcript abundance and sequence variation of nitrogen metabolism genes in rice (Oryza sativa L.) sub-species

Cecal metabolomics of 2 divergently selected rabbit lines revealed microbial mechanisms correlated to intramuscular fat deposition.

The gastrointestinal microbiota plays a key role in the host physiology and health through a complex host-microbiota co-metabolism. Metabolites produced by microbial metabolism can travel through the bloodstream to reach distal organs and affect their function, ultimately influencing the development of relevant production traits such as meat quality. Meat quality is a complex trait made up of a number of characteristics and intramuscular fat content (IMF) is considered to be one of the most important parameters. In this study, 52 rabbits from 2 lines divergently selected for IMF (high-IMF (H) and low-IMF (L) lines) were used to perform an untargeted metabolomic analysis of their cecal content, with the aim to obtain information on genetically determined microbial metabolism related to IMF. A large, correlated response to selection was found in their cecal metabolome composition. Partial least squares discriminant analysis was used to identify the pathways differentiating the lines, which showed a classification accuracy of 99%. On the other hand, 2 linear partial least squares analyses were performed, one for each line, to extract evidence on the specific pathways associated with IMF deposition within each line, which showed predictive abilities (estimated using the Q2) of approximately 60%. The most relevant pathways differentiating the lines were those related to amino acids (aromatic, branched-chain, and gamma-glutamyl), secondary bile acids, and purines. The higher content of secondary bile acids in the L-line was related to greater lipid absorption, while the differences found in purines suggested different fermentation activities, which could be related to greater nitrogen utilization and energy efficiency in the L-line. The linear analyses showed that lipid metabolism had a greater relative importance for IMF deposition in the L-line, whereas a more complex microbial metabolism was associated with the H-line. The lysophospholipids and gamma-glutamyl amino acids were associated with IMF in both lines; the nucleotide and secondary bile acid metabolisms were mostly associated in the H-line; and the long-chain and branched-chain fatty acids were mostly associated in the L-line. A metabolic signature consisting of 2 secondary bile acids and 2 protein metabolites was found with 88% classification accuracy, pointing to the interaction between lipid absorption and protein metabolism as a relevant driver of the microbiome activity influencing IMF.

Scoping Opportunities for Nitrogen Use Efficiency Among Productive Agricultural Forage Grasses With Diverse Rooting Systems

ABSTRACTFor forage production to be efficient and environmentally sustainable, the extent and timing of nitrogen fertiliser applications should match the uptake and growth capabilities of a grass crop. A two‐year field experiment, comprising four diverse grass cultivars, was conducted to assess the impact of two contrasting N‐application rates on forage and root biomass (RB) production and nitrogen‐use‐efficiencies (NUEs). Replicated field plots of perennial ryegrass, tall fescue and two Festulolium (ryegrass × fescue hybrid) cultivars were compared at Low N (LN) 178 and High N (HN) 356 kg ha−1 over 2 years. HN applications increased dry matter yield (DMY) in Year 1 (p < 0.05) but not in Year 2. Ryegrass outyielded all in Year 1 but in Year 2, fescue had the highest DMY at HN (p < 0.05), but cultivars did not differ in yield at LN. Festulolium yields were consistently intermediate. Root biomass at LN in Yr1 was highest in the Festulolium (Lolium perenne × Festuca arundinacea var glaucescens) (p < 0.05). For all grasses, and in both years, mean RB and nitrogen use efficiency (NUE) and nitrogen utilisation efficiency (NutE) were higher under LN, than HN. Nitrogen uptake efficiency (NupE) was similar in all grasses in Year 1, irrespective of N treatment, but in Year 2, excepting tall fescue, was greater in grasses grown under LN. Increasing RB correlated (p < 0.05) with improved NUE and NutE, but no association was evident for NupE. Grass cultivars differed in their response to nitrogen applications. Whilst relative forage production of ryegrass and fescue contrasted over the 2 years, forage yields of Festulolium cultivars were more consistent. In conclusion, HN application depressed NUE by productive grass cultivars and correlations between RB and NUEs may indicate opportunities to help tailor grass cultivar/fertiliser combinations and achieve sustainable forage and root production.

Heredity and fine mapping of a yellow leaf and less tillering mutant yllt10 in rice

Rice (Oryza sativa L.) is a major food crop and increasing rice yield is the primary objective of rice research. Photosynthesis and nitrogen utilization efficiency directly affect the tiller number of rice, which affects the yield of rice. In this study, a stable yellow leaf and less tillering rice mutant yllt10 (yellow leaf and less tillering 10) was obtained by heavy-ion beam mutagenesis of rice variety 'Ke-fu-geng 7'. Compared with the wild type, yllt10 showed reduced chlorophyll content, decreased photosynthesis rate, and abnormal chloroplast structure. The genetic analysis indicated that the phenotype of yllt10 was controlled by a single recessive nuclear gene. Map-based cloning localized YLLT10 between two molecular markers J4 and J5 on chromosome 10. The sequencing of candidate genes within this interval revealed that YLLT10 was an allelic mutation of CAO1/PGL with a single base deletion in the first exon resulting in the frame shift mutation of CAO1/PGL, and YLLT10 was a new allelic variation of CAO1/PGL. The mutant yllt10 was insensitive to changes in nitrogen concentration when being incubated with different nitrogen concentrations. YLLT10 controls leaf color and tiller number and affects photosynthesis and yield of rice. The study of this gene provides a theoretical basis for molecular breeding of rice.

Effects of Recommended Fertilizer Application Strategies Based on Yield Goal and Nutrient Requirements on Drip-Irrigated Spring Wheat Yield and Nutrient Uptake

Excessive application of fertilizers in drip-irrigated wheat production can suppress yields, lower nutrient utilization efficiency, and lead to economic and environmental issues such as nitrogen residues in the soil. Based on a recommended fertilizer application (RF) strategy that takes into account target yield and nutrient requirements, this study explores the responses of wheat plant traits, changes in topsoil and subsoil nutrients, fertilizer utilization, and economic benefits under this strategy. From 2022 to 2023, a field experiment was conducted in a typical oasis spring wheat production area at the northern foot of the Tianshan Mountains in Xinjiang. The treatments included no fertilizer control (CK), the farmer’s conventional practice (FP), recommended fertilizer (RF), RF with nitrogen omission (RF-N), phosphorus omission (RF-P), and potassium omission (RF-K). The results showed that compared with FP, the RF reduced 91 kg N ha−1 (30.3%) and 33 kg P2O5 ha−1 (24.8%) in 2022, and 69 kg N ha−1 (23.0%) and 2 kg P2O5 ha−1 (1.5%) in 2023. The effect in 2023 was better; RF also decreased the NO3−1-N residue in the 0–100 cm soil layer by 40.1 kg N ha−1 compared with FP, with no significant difference in wheat grain yield (RF: 5382.9 kg ha−1) or economic benefit (RF: USD 1613.1 ha−1). Furthermore, there were no significant differences between RF and FP in pre-anthesis NP transport or post-anthesis NP accumulation; however, RF significantly increased pre-anthesis potassium transport volume (15.8%) and transport rate (12.5%). RF led to a 16.3% increase in nitrogen utilization efficiency (NUE), while there was no significant difference in phosphorus utilization efficiency (PUE) compared with FP. The fertilizer yield effect for RF was evaluated as N > P > K. Correlation analysis indicated that grain yield was significantly positively correlated with pre-anthesis NPK transport and post-anthesis NP accumulation. It was also positively correlated with organic matter, alkali-hydrolyzed nitrogen, and Olsen-P content in both the topsoil (0–20 cm) and subsoil (20–40 cm), but not with available potassium in the soil. Therefore, conducting soil tests and determining fertilizer recommendations based on the proposed RF method at harvest can reduce fertilizer usage and achieve a balance between the conflicting objectives of environmental protection, increased crop yields, nutrient utilization efficiency, and improved economic benefits in oasis agricultural areas facing excessive fertilizer application.

Nitrogen use efficiency for seed and oil yield in some Moroccan rapeseed (Brassica napus L.) varieties under contrasting nitrogen supply

In the actual context of climate change and increasing oil and nitrogen prices, oil crops varieties with high nitrogen use efficiency (NUE) will be highly appreciated. As no studies on NUE in spring rapeseed have been carried out in Mediterranean area, including Morocco, this work aimed to assess responses of six rapeseed varieties to six nitrogen levels (0, 30, 60, 90, 120, and 150 Kg N/ha) and their NUE for grain and oil yields. The experiment was conducted according to a split-plot design with three replications, during two cropping seasons. Results showed that increasing nitrogen rate from 0 to 120 kg N/ha led to a significant increase in seed, oil and dry matter yields up to 85.3, 72.35 and 97.9%, respectively. NUE, NUpE (nitrogen uptake efficiency) and NUtE (nitrogen utilization efficiency) decreased by increasing nitrogen application. Regarding oil content, it was negatively affected by nitrogen fertilization, declining from 40.78% for control to 37.77% for 150 kg N/ha. Likewise, nitrogen use and nitrogen utilization efficiency for oil production (ONUE & ONUtE) were negatively affected by nitrogen application. The genotypic variation was statistically significant for all investigated traits. The variety hybrid ‘Trapper’ was the most interesting for ONUE, NUE, seed yield and dry matter. However, for oil yield it was comparable to ‘Moufida’ and ‘Alia’ which showed the highest values for harvest index, branching, pods number per plant, oil content and ONUE. These varieties grown under 120 kg N/ha treatment can be recommended for Morocco.

Integrated Transcriptomic Analyses of Liver and Mammary Gland Tissues Reveals the Regulatory Mechanism Underlying Dairy Goats at Late Lactation When Feeding Rumen-Protected Lysine.

Although low-protein diets can improve the nitrogen utilization efficiency and alleviate economic pressures in ruminants, they may also negatively impact dairy performance. Rumen-protected lysine (RPL) supplementation can improve the health status and growth performance of ruminants without compromising nitrogen utilization efficiency and feed intake. In this study, a total of thirty-three multiparous dairy goats in the late-lactation period were randomly divided into three groups that were separately fed the control diet (namely the protein-adequacy group), the low-protein diet (namely the protein-deficient group), and the RPL-supplemented protein-deficient diet (namely RPL-supplementation group) for five weeks. Here, we investigated the molecular mechanisms regarding how low-protein diets with RPL supplementation compromise lactation phenotypes in dairy goats through cross-tissue transcriptomic analyses. Dietary protein deficiency caused an imbalance in amino acid (AA) intake, disrupted hepatic function, and impaired milk synthesis. Transcriptomic analyses further showed that RPL supplementation exhibited some beneficial effects, like mitigating abnormal lipid and energy metabolism in the liver, elevating hepatic resistance to oxidative stress, improving the mammary absorption of AAs, as well as activating mammary lipid and protein anabolism primarily through peroxisome proliferator-activated receptor (PPAR) and janus kinase-signal transducer (JAK)-signal transducer and activator of transcription (STAT) signaling, respectively. RPL supplementation of a low-protein diet contributes to maintaining late lactation in dairy goats primarily through mitigating hepatic energy disturbances and activating both lipid and protein metabolism in the mammary glands. Since RPL supplementation initiated a series of comprised events on mammary protein and lipid metabolism as well as the hepatic function and energy generation in dairy goats under protein deficiency during late lactation, these findings thus provide some insights into how RPL supplementation helps maintain milk production and health in dairy mammals especially at late lactation.

Dynamics of Fermentation Parameters and Bacterial Community in Rumen of Calves During Dietary Protein Oscillation.

Dietary crude protein concentration oscillation can improve the nitrogen utilization efficiency of ruminants. However, little is known about the dynamic changes in microbiota and fermentation in the rumen of calves during the oscillation period. In this study, six calves were fed an oscillating diet at 2-day intervals, including a high-protein diet (HP) and a low-protein diet (LP). The rumen fermentation parameters, plasma urea-N concentration, and rumen bacterial diversity were characterized throughout the oscillation period. The concentrations of volatile fatty acids, NH3-N, and plasma urea-N in rumen changed significantly with an oscillating diet. The abundance of Prevotella_1, Selenomonadales, Succiniclasticum, Clostridiales, Ruminococcaceae, Lachnospiraceae, and Rikenellaceae_RC9_gut_group showed significant changes with diet. Prevotella_1 was positively correlated, and Lachnospiraceae_AC2044_group and Saccharofermentans were negatively correlated with NH3-N. The abundance of Amino Acid Metabolism, Metabolism of Other Amino Acids, and Glycan Biosynthesis and Metabolism pathways, annotated by bacterial functional genes, decreased when the diet changed from HP to LP. The abundance of the Carbohydrate Metabolism pathway increased after the two dietary changes. In conclusion, the plasma urea-N concentration was not as sensitive and quick to adapt to diet changes as the rumen fermentation parameters. Rumen bacteria were responsible for increasing the nitrogen utilization efficiency of calves fed an oscillating diet.

Rational Nitrogen Reduction Helps Mitigate the Nitrogen Pollution Risk While Ensuring Rice Growth in a Tropical Rice–Crayfish Coculture System

The incorporation of aquaculture feed within a rice–crayfish coculture system significantly enhances nitrogen cycling, thereby diminishing the reliance on chemical fertilizers. However, this benefit is often overlooked in practice, and farmers continue to use large quantities of chemical fertilizers to maximize production, resulting in excessive soil fertility and water nitrogen pollution. Thus, avoiding nitrogen pollution in rice–crayfish coculture systems has become a pressing issue. In this study, we conducted a two-year experiment with two rice cultivars, and a 33.3% reduction in nitrogen fertilizer in a rice–crayfish coculture system (RC), to systematically analyze the overall nitrogen balance, rice nitrogen nutrition, and soil fertility, as compared with a rice monoculture system (RM). Our findings revealed the following: (1) Under the 33.3% reduction in nitrogen fertilizer, the nitrogen surplus in the rice–crayfish coculture system was comparable to that in the rice monoculture, and was controlled at an environmental safety level. (2) Nitrogen utilization efficiency and the accumulation of nitrogen in the rice–crayfish coculture were comparable to those in the rice monoculture. The nitrogen cycle in this system was able to provide the nitrogen required for rice growth after nitrogen fertilizer reduction. (3) The rice–crayfish coculture significantly improved the overall soil fertility and the effectiveness of soil nitrogen nutrition. Furthermore, cutting off the application of nitrogen fertilizer after the mid-tillering stage effectively controlled the total nitrogen content in soil after rice maturity. In conclusion, reducing nitrogen fertilizer in a rice–crayfish coculture system is feasible and beneficial. It ensures rice production, reduces the risk of excessive nitrogen surplus and surface pollution, and promotes a greener, more environmentally friendly paddy field ecosystem.

Effects of different ratios of nitrogen base fertilizer to topdressing on soil nitrogen form and enzyme activity in sugar beet under shallow drip irrigation

Sugar beets account for 30% of global sugar production each year, and their byproducts are an important source of bioethanol and animal feed. Sugar beet is an important cash crop in Inner Mongolia, China. To achieve high yields and sugar content, it is essential to supply nitrogen fertilizer in accordance with the growth characteristics of sugar beet, thereby enhancing the efficiency of nitrogen fertilizer utilization. A two-year experiment was carried out in the experimental field of the Inner Mongolia Academy of Agricultural & Animal Husbandry Sciences. The impact of varying ratios of nitrogen-based fertilizer to topdressing on nitrate nitrogen and ammonium nitrogen levels in the 20–60 cm soil layer, as well as the activities of protease, urease, catalase, and sucrose in the 20–40 cm soil layer were investigated during the rapid leaf growth period and root and sugar growth period. Results indicated that different ratios of nitrogen-based fertilizer to topdressing significantly influenced the levels of nitrate nitrogen and ammonium nitrogen, and the activities of protease and urease in the 0–20 cm soil layer, with these effects diminishing as soil depth increased. The activities of catalase and sucrose were minimally impacted. Nitrogen was applied at 150 kg/ha during the growth period of sugar beet, according to the growth characteristics of sugar beet to maximize nitrogen utilization efficiency. Topdressing was completed with irrigation at the rapid growth stage. The nitrogen-based fertilizer to topdressing ratio of 6:4 resulted in optimal crop yield and sugar yield of sugar beet under shallow drip irrigation. Additionally, the activities of protease and urease in different soil treatments were significantly different, and the activities of protease and urease in the 0–40 cm soil layer were identified as useful soil physiological indicators for nitrogen utilization in sugar beet.

Nitrogen use efficiency of open-pollinated maize cultivars and topcrosses under low nitrogen soil

The study was conducted to evaluate the nitrogen utilization efficiency (NUE) of open-pollinated maize cultivars under low nitrogen soil conditions. It took place at the Lower Niger River Basin Development Authority in Ilorin, Nigeria, during the 2019 and 2020 cropping seasons. The nitrogen treatments (0, 45, and 90 kg N ha⁻1) were assigned as the main plots, while the genotypes were designated as sub-plots in a split-plot design. The NUE of open-pollinated varieties (OPVs) and Topcrosses significantly increased with the application of 45 kg of nitrogen per hectare compared to 0 kg. Similarly, the maize grain yield for both OPVs and Topcrosses ranged from 1.40 to 3.57 t ha⁻1 and from 1.07 to 2.64 t ha⁻1 across the two years with the application of 45 kg of nitrogen per hectare compared to 0 kg. With the exception of days to 50 % silking, all other traits tested exhibited a significant correlation with grain yield. A gene pool for tolerance to low nitrogen may have been present in the cultivars Dmr-Esr Y Cif 2 and Acr 95 Tze Comp 4C3, which combined well with other cultivars to produce high grain yield and NUE. Topcrosses, including Ev Dt-Y 2000 Str C0 × Tze-W Dt Str C4, Dmr-Esr Y Cif 2 × Acr 95 Tze Comp 4C3, Ak 95 Dmr-Esrw × Tzb Rel D4 CO-W, Dmr-Esr Y Cif 2 × Tze-W Dt Str C4, and Br 9922 Dmr Sr × Ev Dt-Y 2000 Str C0, also demonstrated strong potential for maize grain yield and NUE. This suggests that these crosses could serve as promising candidates for developing low nitrogen tolerance in maize for low nitrogen soil environments. A positive relationship between fertilizer levels, NUE, and grain yield indicates that proper nitrogen fertilizer management can enhance both NUE and the grain yield of maize genotypes. Genetic analysis revealed that both phenotypic coefficient of variation (PCV) and environmental variance (δ2p) were higher than genotypic coefficient of variation (GCV) and genetic variance (δ2g), suggesting that environmental influences were more significant than genetic factors for the tested traits. Consequently, improving these traits may be achieved by manipulating environmental conditions.

Sensitivity analysis of the INRA 2018 feeding system for ruminants by hybrid local and global approaches: Comparing the contribution of dietary input variables to multiple response prediction in dairy cattle

We conducted sensitivity analysis (SA) of the INRA 2018 feeding system for ruminants applied to dairy cows. We evaluated which dietary input variables contribute most to changes in each output variable, considering the potential interactions presence among input variables. A quantitative analysis (one-at-a-time analysis, OAT; i.e., local SA) and a relative comparative analysis (global SA, GSA) through variance-based SA considering potential interactions and non-monotonicity were applied. The 5 likely influential dietary input variables were selected: CP, Gross energy (GE), OM apparent digestibility (OMd), effective degradability of nitrogen assuming a passage rate of 6%/h (ED6_N) and true intestinal digestibility of nitrogen. The sensitivity of 5 selected animal responses (output variables) to input variables was analyzed: DMI, milk protein yield (MPY), energy in methane (ECH4), nitrogen utilization efficiency (NUE), and ratio between urine and total N excretion (UN/TN). Six diets for dairy cattle, reflecting the diversity of diets commonly used in practice, were formulated to meet 95% of the potential milk production (37.5 kg/d) of a multiparous dairy cow at wk 14 of lactation. For each diet, the 5 input variables were randomly sampled around the INRA 2018 feed table values (reference point), and the animal responses around this reference situation were calculated using the rationing software INRAtion®V5. In OAT, the sensitivity of animal responses was quantified by calculating the normalized tangent value at the reference point, and in GSA, the Sobol indices were calculated for relative influence of each input and their interaction. The influence of the 5 key input variables on the 5 main animal responses predicted from the INRA feeding system was consistent across both SA approaches. With the 6 diets, GE and OMd appeared as the main contributors to changes in DMI, MPY, ECH4, and NUE. Crude protein was the main contributor to changes in UN/TN and another major contributor to changes in NUE. When considering OAT, the sensitivity of outputs showed differences depending on diet, more particularly for DMI and MPY. With grass hay-based diets (GH diets), DMI was less sensitive and MPY was more sensitive to variations in input variables than other diets. When considering GSA, interactions between input variables were also noticeable for DMI and MPY; the interactions were high with the GH diets for DMI, and with fresh ryegrass and grass silage diets for MPY. On the other hand, for MPY, the non-GH diets were less sensitive to variations in input variables and the interaction between inputs was higher than with GH diets. In both cases, the interactions were mainly related to energy-related inputs (i.e., OMd and GE). Our results support the hypothesis that MPY, unlike DMI, is more responsive to energy-related factors at high PDI/UFL ratio (i.e., between metabolizable protein and NEL, e.g., GH diets >117 g PDI/UFL), than at lower PDI/UFL ratio. Hence, hybridizing the SA methods can help to interpret the system and facilitate a more precise evaluation thereof, especially GSA, which is amenable to non-monotonic models such as those characterizing complex feeding systems integrating multiple nutritional and animal factors.