N-use Efficiency Research Articles

Validating genomic prediction for nitrogen efficiency index and its composition traits of Holstein cows in early lactation.

Nitrogen (N) use efficiency (NUE) is an economically important trait for dairy cows. Recently, we proposed a new N efficiency index (NEI), that simultaneously considers both NUE and N pollution. This study aimed to validate the genomic prediction for NEI and its composition traits and investigate the relationship between SNP effects estimated directly from NEI and indirectly from its composition traits. The NEI composition included genomic estimated breeding value of N intake (NINT), milk true protein N (MTPN) and milk urea N yield. The edited data were 132,899 records on 52,064 cows distributed in 773 herds. The pedigree contained 122,368 animals. Genotypic data of 566,294 SNP was available for 4514 individuals. A total of 4413 cows (including 181 genotyped) and 56 bulls (including 32 genotyped) were selected as the validation populations. The linear regression method was used to validate the genomic prediction of NEI and its composition traits using best linear unbiased prediction (BLUP) and single-step genomic BLUP (ssGBLUP). The mean theoretical accuracies of validation populations obtained from ssGBLUP were higher than those obtained from BLUP for both NEI and its composition traits, ranging from 0.57 (MTPN) to 0.72 (NINT). The highest mean prediction accuracies for NEI and its composition traits were observed for the genotyped cows estimated under ssGBLUP, ranging from 0.48 (MTPN) to 0.66 (NINT). Furthermore, the SNP effects estimated from NEI composition traits, multiplied by the relative weight were the same as those estimated directly from NEI. This study preliminary showed that genomic prediction can be used for NEI, however, we acknowledge the need for further validation of this result in a larger dataset. Moreover, the SNP effects of NEI can be indirectly calculated using the SNP effects estimated from its composition traits. This study provided a basis for adding genomic information to establish NEI as part of future routine genomic evaluation programs.

Trade-offs and synergies of plant traits co-drive efficient nitrogen use in intercropping systems

ContextNitrogen (N) enrichment increases aboveground net primary productivity, but causes a loss of plant diversity and a decline in ecosystem stability. Diverse systems that enhance the N-use efficiency help achieve sustainable development goals. Functional traits have been used to predict ecosystem functions in diverse systems. However, few studies considered both the effect of functional traits and evaluated the relationship between traits and N acquisition in intercropping. ObjectiveThe aim of this study was to evaluate the relationships between functional traits resulting from interspecific interactions and determine relationships between functional traits and N acquisition of intercropping systems. MethodsBased on a four-year N-manipulation field experiment, we measured 10 functional traits related to light interception and nutrient-use efficiency in different systems (maize (Zea mays L.), peanut (Arachis hypogaea L.), soybean (Glycine max L. Merrill.) monocultures, and maize/peanut and maize/soybean intercrops) at the pre-tasseling stage of maize, calculated the crude protein yield and aboveground N content at harvest time. ResultsThe maize grain N concentration was increased by N application, and it increased by intercropping in legumes. Both maize/soybean and maize/peanut intercropping systems increased crude protein productivity. Synergies among plant functional traits of maize allowed maize to establish its dominance, which resulted in greater N acquisition and crude protein yield of intercrops. Trade-offs among plant functional traits (between root traits and shoot traits of legumes) show strategies of legumes in response to interspecific competition. The specific leaf area of the legume was a key trait and affected interspecific interactions. This N-use advantage of intercropping was directly influenced by the aboveground functional traits of the system (community-weighted mean values of functional traits), but indirectly affected by belowground functional traits of the system. Conclusions and significanceOur study highlights greater N uptake of the intercropping system and suggests that intercropping can be used to increase the quality of crop products via enhancing crude protein production. The synergy and trade-offs in plant functional traits together enhance efficient N use in the intercropping systems. These findings help to better understand the underlying mechanisms that determine efficient resource use in diverse cropping systems and have implications for the sustainable management of food-production systems.

Is India’s largest fertilizer manufacturer misleading farmers and society using dubious plant and soil science?

Background and AimsThe accessibility and relatively low cost of nitrogen (N) fertilizers have been a gift to humankind and made it possible to feed the exponentially growing world population. The excessive use of N, in combination with a poor N use efficiency (NUE) in crop production, is associated with severe environmental impacts, and the scientific community has repeatedly warned that the safe operating space for N within the planetary boundaries has been exceeded. In the light of these considerations, a global player and India’s largest fertilizer manufacturer, the Indian Farmers Fertilizer Cooperative (IFFCO), has recently developed and patented a nanotechnology-based fertilizer marketed as Nano Urea (liquid). Strikingly, the producers state that it is now possible to replace a 45 kg bag of conventional urea, containing 21 kg N, by foliar application of just 20 g N in the form of nano urea (NU). If so, N from this novel high-tech fertilizer product should be able to increase the NUE of crops more than 1000 times compared to conventional urea. This year, the Indian government and IFFCO announced plans to massively boost production by building 10 new factories, with an annual production capacity of 440 million bottles NU by 2025 and to expand export of the product to another 25 countries, mainly situated in Asia, Africa and South-America. In the marketing of NU, IFFCO states that there is scientific evidence for distinct beneficial properties in terms of higher crop yields and reduced negative environmental impacts. Similar ambitions have recently been presented for Nano Zinc, Nano Copper, and Nano Di-Ammonium-Phosphate, a product that entered the market in March 2023.MethodsIn this Opinion Paper, we compare the claims made by IFFCO scientists to the existing scientific evidence in the field of foliar nanofertilizers.ResultsWe observe that NU is a poorly described product with no scientifically proven effects. The product is marketed with misleading and wrong statements about its fertilizer efficiency, the underlying plant uptake pathways, and the environmental friendliness.ConclusionThe expectations raised by IFFCO are far from reality and may lead to large-scale yield losses with serious consequences for food security and the livelihood of farmers. At the same time, the confidence in innovative sustainable products as well as the science behind them may be threatened. Based on the IFFCO case, and considering the booming emergence of novel nano based fertilizers appearing all over the world these years, it is clear that much more priority should be given to scientifically prove their efficacy and mode of action, before they are launched on the markets.

Variation of the water-use efficiency and nutrients of Pinus armandii under different ages and growth season

Seasonal changes in carbon (C), nitrogen (N), and phosphorus (P) stoichiometry and water-use efficiency (WUE) in the needles of Pinus armandii were investigated. The needles of P. armandii were sampled in January, May, August, and November 2021. The results showed that (1) the needle δ13C values of young P. armandii forests were higher than those of middle-aged P. armandii forests, and these differences were significant in winter. (2) Both young and middle-aged P. armandii forests were restricted by N and P, and P. armandii was more restricted by N in summer, autumn, and winter. (3) Needle δ13C values were significantly positively correlated with P and negatively correlated with N, C/P, and N/P in young P. armandii forests; P. armandii (especially young stands) can compensate for decreases in N-use efficiency by increasing WUE. The C, N, and P content and their stoichiometric ratios were affected by a combination of season, stand age, and WUE. This study contributes to an in-depth understanding of the adaptive mechanisms of nutrients and WUE in P. armandii in the subtropical region. Our findings also have implications for the management of P. armandii plantations in the study area.

Survey of farm-gate N and P balances on arable and dairy organic and conventional farms in Sweden—basis for improved management

About half of all N and P loads to Swedish waters originate from agriculture and must decrease to reach environmental goals. Studying nutrient management at farm level can provide an understanding of nutrient recycling and the risk of losses. In a survey of organic and conventional dairy and arable farms in three southern counties of Sweden, farm-gate N and P balances and N use efficiency (NUE) were analysed. Crop distribution differed significantly between organic and conventional farms, with organic dairy farms having higher proportions of ley and pulse crops and organic arable farms having a much higher proportion of N-fixing crops than corresponding conventional farms. Conventional dairy and arable farms had on average 70% and 40% higher N surplus than corresponding organic farms. Farm-gate P surplus was larger on conventional dairy farms and much larger on organic arable farms, mainly due to purchase of P-rich organic fertilisers. Organic dairy farms had higher NUE than corresponding conventional farms, but the opposite was true for arable farms. However, in the southernmost county Skåne, where soil fertility and yield potential are high, NUE was similar on all arable farms. Total inputs of N and P were positively correlated with N and P surpluses, especially on dairy farms. Improved manure and crop residue management, reduced use of purchased mineral N fertilisers coupled to more uniform within-farm distribution of manure, use of catch crops, intercropping and organic fertilisers with appropriate N:P ratio are measures that can reduce farm nutrient surpluses and improve nutrient management on both organic and conventional farms.

Effect of Lolium perenne population differences on shoot tissue nitrogen concentrations when grown on a peat soil

AbstractGrass nitrogen (N) concentrations of dairy grasslands are higher on peat soil than on mineral soils. This can lead to increased N losses to air and water from dairy farming systems on peat soils. Our hypothesis was that the use of low-N perennial ryegrass (Lolium perenne L.) genotypes could be a means to lower grass N concentrations, when grown on peat soils. Our objective was to determine whether perennial ryegrass populations with different shoot tissue N concentrations, recorded on a sandy soil, would show different shoot tissue N concentrations and N use efficiencies (NUE) or N uptake efficiencies (NUptE) when grown on a peat soil. First, a pot experiment lasting 62 days was carried out with nine diploid and seven tetraploid populations, followed by a field experiment with two diploid and two tetraploid populations and a control lasting 30 months. Both experiments had three N fertilization levels. In the pot experiment, populations explained 3% of the variation in shoot tissue N concentration among tetraploids, 5 and 7% of the variation in NUE among diploids and tetraploids and 12% of the variation in NUptE among diploids. In the field experiment, populations explained 44% of the variation in NUptE. A higher NUE coincided with lower shoot tissue N concentrations among tetraploid populations in the pot experiment. We conclude that there is potential to alter the shoot tissue N concentrations of perennial ryegrass grown on peat soil, via selection for shoot tissue N concentrations and NUE.

Field Screening of Wheat Cultivars for Enhanced Growth, Yield, Yield Attributes, and Nitrogen Use Efficiencies

Optimizing nitrogen (N) inputs is crucial for maximizing wheat yield and ensuring environmental sustainability. Wheat’s economic significance in India calls for a comprehensive evaluation of its ecological implications to develop a resilient production system. This study aimed to identify and evaluate ten wheat cultivars for their yield and N-use efficiency under varying nitrogen inputs (control (N0), half of the recommended nitrogen (N75), and the recommended nitrogen (N150)) using the surface application of neem-oil-coated urea. All N inputs were applied in three splits, basal, crown root initiation, and tillering stages, and an experiment was conducted in a split-plot design. The application of N150 gave the highest dry matter accumulation (DMA) at harvesting stage (AHS) (871 g m−2), seed/spike (60), grain yield (GY = 7.4 t ha−1), straw yield (SY = 8.9 t ha−1), harvest index (HI = 45.2%), protein (12.5%), and total uptake of N (TUN) (223 kg ha−1) by the cultivar ‘HD 3249’, being closely followed by the cultivar ‘HD3117’. Six cultivars (‘HD 3298’, ‘HD 3117’, ‘HD 3249’, ‘PBW 550’, ‘HD 3086’, ‘HD 2967’) out of the ten cultivars evaluated responded well to different input treatments with respect to the grain yield efficiency index (GYEI ≥ 1). Regarding N input, N75 and N150 recorded the highest increases in plant height, AHS (16.5%; 21.2%), dry matter accumulation (DMA) at 30 days after sowing (DAS) (37.5%; 64%), DMA-60 DAS (42%; 53%), DMA-90 DAS (39.5%; 52.5%), TILL-30 DAS (19.8%; 26.4%), TILL-60 DAS (33.3%; 44%), TILL-90 DAS (37.2%; 47.2%), seed/spike (8%; 10%), 1000-grain weight (7.8%; 12.2%), and protein content (23.3%; and 33%) when compared with N0. Furthermore, the application of N75 and N150 improved GY (72.1%; 142.6%), SY (61.1%; 110.6%), BY (65.5%; 123%), and HI by 4.4% and 9%, respectively, over N0. Nitrogen addition (N75 and N150) also significantly increased total nitrogen uptake (104.7%; 205.6%), respectively, compared to N0. The correlation analysis revealed a positive association among most of the crop parameters. Overall, our research results suggest that the cultivars ‘HD 3249’ and ‘HD 3117’ have the potential to be effective options for improving N utilization efficiency, grain yield, and GYEI in North-West India.

Global nitrogen deposition inputs to cropland at national scale from 1961 to 2020

Nitrogen (N) deposition is a significant nutrient input to cropland and consequently important for the evaluation of N budgets and N use efficiency (NUE) at different scales and over time. However, the spatiotemporal coverage of N deposition measurements is limited globally, whereas modeled N deposition values carry uncertainties. Here, we reviewed existing methods and related data sources for quantifying N deposition inputs to crop production on a national scale. We utilized different data sources to estimate N deposition input to crop production at national scale and compared our estimates with 14 N budget datasets, as well as measured N deposition data from observation networks in 9 countries. We created four datasets of N deposition inputs on cropland during 1961–2020 for 236 countries. These products showed good agreement for the majority of countries and can be used in the modeling and assessment of NUE at national and global scales. One of the datasets is recommended for general use in regional to global N budget and NUE estimates.

Key to Life, Risks and Cycle of Nitrogen

Nitrogen is practically inert and largely unreactive, existing mostly in molecular form (N2) in the atmosphere and unsuitable for uptake by living matter. But it is one of the most commonly used practices to increase crop yields throughout the world because of the abundant availability of N fertilizers and their great effectiveness to increase yields compared with other organic fertilizers, such as manure and compost. It is essential to achieve production levels, which enable global food security, without compromising environmental security. Excessive application of N fertilizers in the last several decades, however, has resulted in undesirable consequences of soil and environmental degradations, such as soil acidification, N leaching to the groundwater, and greenhouse gas (N2O) emissions. Crop yields have declined in places where soil acidification is high due to the unavailability of major nutrients and basic cations and the toxic effect of acidic cations. Other disadvantages of excessive N fertilization include increased cost of fertilization, reduced N-use efficiency, and negative impact on human and livestock health. Diffuse pollution, caused by N fertilization in agriculture, has become a global problem that is difficult to solve. Nearly half of N fertilizer input is not used by crops and is lost into the environment via the emission of gases or by polluting water bodies. The N pollution level expected by 2050 is projected to be 150% higher than in 2010, with the agricultural sector accounting for 60% of this increase. So, to reduce these problems globally, understanding of nitrogen cycle and nutrient use efficiency is important.

Effect of topdressing time on spring maize yield and nitrogen utilization in black soil of northeast China

Topdressing time is crucial to achieving a high yield. To determine the optimum topdressing time for spring maize in the black soil of northeast China in the “one base and one topdressing” mode, the effects of topdressing time of nitrogen (N) fertilizer on maize yield, N utilization, and inorganic N residue and distribution were investigated by using 15N labeling technique. Four treatments were designed: no N fertilizer (N0), N fertilizer topdressing at jointing stage (N1), N fertilizer topdressing at belling stage (N2), and N fertilizer topdressing at tasseling stage (N3). The results showed that compared with N1 and N3, the maize yield, N uptake and N use efficiency (NUE) in N2 treatment significantly increased by 12.1% and 24.7%, 10.0% and 16.0%, and 26.4% and 38.9%, respectively (P < 0.05). The later the topdressing time, the more inorganic N remained in the soil profile (0–60 cm). The rate of potential N loss was higher when the topdressing time was too early or too late. Compared with N1, the residual amount of 15N in the soil profile (0–60 cm) of N2 and N3 treatments increased by 17.2% and 44.8%, respectively. The soil inorganic N (SIN) accumulation in the deep soil profile (40–60 cm) of N2 treatment decreased by 7.6% and 42.7%, respectively, as compared with N1 and N3. Therefore, the application of N fertilizer at the belling stage was beneficial to the high yield and efficient production of maize in the black soil region of Northeast China.

Optimizing nitrogen fertilization for hybrid canola (Brassica napus L.) production across Canada

Context or problemHybrids are currently the dominant varieties in canola production, but their yield response to nitrogen (N) application across Canada has not been adequately updated. As a result, there is a lack of effective N management guidelines for modern hybrid canola to reach their full yield potential and cope with growing abiotic stresses caused by climate change. Objectives or research questionsThis study was designed to investigate the responses of yield and N use efficiency (NUE) of modern canola hybrids to N fertilization for determining site-specific economic optimum N rates (EONR). Additionally, the key driving factors of canola yields and N recommendations were identified. MethodsA 32 site-year field study across Canada was conducted to test 8 combinations of N rates and application methods on 2 site-specific hybrids in each trial. ResultsNitrogen fertilization greatly increased canola yield by an average of 41%, with significant responses in 19 out of 32 trials. Split-N strategy led to similar yield, NUE, and yield response index compared to preplant-only N application. However, these traits varied among hybrids due to different growing environments and hybrid-specific tolerance to abiotic stresses. The number of heat-stress days and heat-induced thermal accumulation surrounding the 4 weeks before and post-flowering stage directly determined the canola responses to N fertilization and EONR. ConclusionsOur results suggest a site-specific EONR of 146–166 kg N ha−1 in the Black soil zone, 85–100 kg N ha−1 in the low-yielding Brown soil zone, and 140 kg N ha−1 in Ontario, preferably with a split-N strategy for hybrid canola production. The split-N fertilization is generally recommended, as it provides an opportunity to adjust the amount of topdressing N based on historical and early season weather conditions to achieve the dual goals of increasing canola productivity and reducing greenhouse gas (GHG) emissions from fertilizer use. The energy and time costs must be considered when making practical decisions. Environment-specific selection of canola hybrids also played an important role in the response to N, with ‘6074RR’ in favorable weather and ‘L233P’ in drought-prone conditions appearing to be good choices for specific ecoregions.

Effects of nitrogen forms on nitrogen utilization, yield, and quality of two wheat varieties with different gluten characteristics

The assimilation and utilization of different nitrogen (N) forms in wheat are different. Therefore, supplying suitable forms of N may be an effective way to optimize yield, quality, and N use efficiency (NUE) synergistically. A two-year field trial was conducted with Jimai22 (JM22) and Jimai44 (JM44) wheat varieties at differential gluten characteristics, with N form treatments: no nitrogen (N0), and nitrogen supply (225 kg ha−1) as urea (U), ammonium nitrogen (ammonium chloride, A), nitrate nitrogen (calcium nitrate, NI), U + A (1:1, UA), U + N (1:1, UN), and N + A (1:1, NA). The results showed that different N forms significantly affected wheat yield, N utilization, and grain quality. Combined application of urea and nitrate nitrogen (UN) significantly increased the spike number by 3.5% on average over U (conventional fertilization), but with no statistical difference in grain yield. N and A treatments significantly increased the activity of N metabolism enzymes in flag leaves and grains at the early filling stage but rapidly declined at the middle and late filling stages. In contrast, UN treatment significantly increased nitrate reductase and glutamine synthetase activities of wheat flag leaves and grains within 7–28 d after anthesis, which facilitated N assimilation and significantly increased free amino acids content in the middle and late filling stages, thereby significantly promoting the accumulation of gliadin and glutenin in grains, resulting in the highest protein content and the best processing quality of JM22 and JM44. Except for N0, NUE, N uptake efficiency (NUPE), and N apparent recovery fraction (NARF) under UN were the highest, which were significantly increased by 4.3%, 5.8%, and 11.8% on average compared to the U treatment, respectively. Therefore, the combined application of urea and nitrate nitrogen could synergistically improve quality and nitrogen use efficiency while maintaining yield, which is important for the rational application of nitrogen fertilizer and achieving stable yield, high quality and efficient production of wheat.

Excessive N applications reduces yield and biological N fixation of summer-peanut in the North China Plain

ContextThe North China Plain (NCP) is China’s largest peanut producing area, where winter-wheat summer-peanut is an important double cropping system. Excessive nitrogen (N) applications are widely used leading to declined N use efficiency (NUE) and biological N fixation (BNF). However, the influence of excessive fertilizer N inputs on yield and BNF of summer-peanut remains uncertain. ObjectiveThe study aims to evaluate the impacts of different fertilizer N inputs on yield and BNF of summer-peanut in the NCP, and explore the optimal N rates for achieving high NUE and low N losses without sacrificing yield. MethodsA three-year field experiment and pot experiment involving five N treatments (N rates with 0, 50, 100, 150, and 200 kg N ha−1, defined as N0, N50, N100, N150 and N200 in the study, respectively) were conducted in the NCP. The jointing use of field experiment and pot experiment were adopted to measure BNF of summer-peanut, and the partial least squares path model and a nightingale rose diagram were both included in the study. ResultsSummer-peanut yield increased quadratically with increasing N application, but N rates larger than 150 kg N ha−1 caused inadequate seed filling and thus led to slightly reduced yield. Generally, increased N applications significantly increased soil mineral N (SMN) between 0 and 60 cm depth, and dramatically reduced BNF as high SMN strongly inhibits biological nitrogenase activity. ConclusionsThe N application required to obtain an optimum yield of 3915 kg ha−1 with relatively high NUEoi (the ratio of N output and N input, 73.0%) and low N losses in the summer-peanut production was 150 kg N ha−1 in the NCP. ImplicationsThe sustainable development of summer-peanut systems will involve reduced N application rates, and N optimization in the winter-wheat summer-peanut rotation should receive further attention considering the N legacy effects.

Leaf trait responses to global change factors in terrestrial ecosystems

Global change influences plant growth by affecting plant morphology and physiology. However, the effects of global change factors vary based on the climate gradient. Here, we established a global database of leaf traits from 192 experiments on elevated CO2 concentrations (eCO2), drought, N deposition, and warming. The results showed that the leaf mass per area (LMA) significantly increased under eCO2 and drought conditions but decreased with N deposition, whereas eCO2 levels and drought conditions reduced stomatal conductance and increased and decreased photosynthetic rates, respectively. Leaf dark respiration (Rd) increased in response to global change, excluding N deposition. Leaf N concentrations declined with eCO2 but increased with N deposition. Leaf area increased with eCO2, N deposition, and warming but decreased with drought. Leaf thickness increased with eCO2 but decreased with warming. eCO2 and N deposition enhanced plant water-use efficiency (WUE), eCO2 and warming increased photosynthetic N-use efficiency (PNUE), while N fertilization reduced PNUE significantly. eCO2 produced a positive relationship between WUE and PNUE, which were limited under drought but increased in areas with high humidity and high temperature. Trade-offs were observed between WUE and PNUE under drought, N deposition, and warming. These findings suggest that the effects of global change factors on plants can be altered by complex environmental changes; moreover, diverse plant water and nutrient strategy responses can be interpreted against the background of their functional traits.

Evaluating How Enhanced Efficiency Nitrogen Fertilizers Improve Agricultural Sustainability: Greenhouse Multi-Phase Tracking System

The vast consumption of nitrogen-based fertilizers is a significant source of environmental pollutants in all phases. While enhanced-efficiency nitrogen fertilizers (EENFs) improve N-use efficiency and reduce environmental impact, their performance depends on local conditions. Here, we present a relatively simple soil–fertilizer–plants greenhouse setup for the multi-phase tracking of N species of the effects of EENFs. We compared the environmental and agronomic performance of three urea-based EENFs (urea embedded with urease inhibitors, 2-month, and 4-month controlled release urea) and the common split surface application of the granulated urea. We tested the fertilizer applications on basil seedlings for three consecutive growing cycles. The analyses carried out included nitrogen recovery in plant biomass, soil, drainage, and NH3 and N2O emissions. This multi-phase research indicates that tested EENFs perform better than the standard surface-applied urea. The four-month controlled-release urea fertilizer matched the basil N demand the best, significantly increasing yield and improving nitrogen use efficiency while reducing NO3− leaching and NH3 and N2O emissions. The presented soil–fertilizer–plants experimental setup provides a relatively easy-to-handle system for the comprehensive tracking of N dynamics, including plant response. It allows stakeholders to estimate and improve fertilization sustainability.

A Review of Effect of Saponins on Ruminal Fermentation, Health and Performance of Ruminants.

Saponins are steroid, or triterpene glycoside, compounds found in plants and plant products, mainly legumes. However, some plants containing saponins are toxic. Saponins have both positive and negative roles in animal nutrition. Saponins have been shown to act as membrane-permeabilizing, immunostimulant, hypocholesterolaemic, and defaunating agents in the rumen for the manipulation of ruminal fermentation. Moreover, it has been reported that saponins have impair protein digestion in the gut to interact with cholesterol in the cell membrane, cause cell rupture and selective ruminal protozoa elimination, thus improving N-use efficiency and resulting in a probable increase in ruminant animal performance.

Optimizing nitrogen input and nitrogen use efficiency through soil nitrogen balance in a long-term winter wheat-summer maize rotation system in North China

Nitrogen (N) fertilizer application has revolutionized agricultural productivity, but excessive N fertilizer application has resulted in low N use efficiency (NUE) and high N accumulation, increasing the risk of N losses. Here, we hypothesize that the apparent N balance can be used as an indicator to identify the N input for obtaining high yield with a high NUE. Thus, a 12-year field experiment involving seven N treatments (0, 120, 240, 360, 480, 600, and 720 kg N ha–1 per year) in a typical winter wheat-summer maize rotation system in North China was conducted to investigate the response of crop yield and NUE to the N balance under different N application rates and to identify the N input–output framework. The annual yield increased in a linear-platform and NUE decreased with increasing N fertilizer application. The N balance and yield are strongly correlated to predict changes in yield, and a critical N balance of 44.4–64.9 kg N ha–1 per year was recommended for optimal yield with minimal risk of N loss. The N balance and NUE can be presented in the framework of N input–output, and the critical N input estimated from the N balance of 217–252 kg N ha–1 could obtain high productivity with high NUE (74.3–79.6 %). Overall, the apparent N balance could be used as a key indicator for optimizing N input, providing a strong reference for limiting N excess in intensive production areas and evaluating agronomic and environmental performance in N management. Data AvailabilityThe datasets generated during and analyzed during the current study are available from the corresponding author on reasonable request.

The role of root size and root efficiency in grain production, and water-and nitrogen-use efficiency in wheat.

The root system is the major plant organ involved in water and nutrient acquisition, influencing plant growth and productivity. However, the relative importance of root size and uptake efficiency remains undetermined. A pot experiment was conducted using two wheat varieties with different root sizes to evaluate their capacity for water and nitrogen (N) uptake and their effects on grain production, water-use efficiency (WUE), and N-use efficiency (NUE) under two water treatments combined with three N levels. The leaf water potential and root exudates of changhan58 (CH, small root variety) were higher or similar to those of changwu134 (CW, large root variety) under water/N treatment combinations, indicating that small roots can transport enough water to above the ground. The addition of N improved plant growth, photosynthetic traits, and WUE significantly. There were no significant differences in WUE or grain production between the two cultivars under well-watered conditions. However, they were significantly higher in CH than in CW under water deficit stress. Nitrogen uptake per unit root dry weight, glutaminase, and nitrate reductase activities were significantly higher in CH than in CW, regardless of moisture conditions. Root biomass was positively correlated with evapotranspiration, while the root/shoot ratio was negatively correlated with WUE (P < 0.05) but not with NUE. In a pot experiment, water and N uptake were more strongly associated with resource uptake availability than root size. This may provide guidance in wheat breeding programs for drought-prone regions. © 2023 Society of Chemical Industry.

Optimizing nitrogen application improves its efficiency by higher allocation in bolls of cotton under drip fertigation

Nitrogen (N) loss is becoming one of the main limitations for sustainable agricultural production globally, particularly for crops such as cotton. To alleviate this issue, a promising strategy may be to exploit the N-saving potential of cotton plants by optimizing N application ratios at different growth stages under lower N rate and higher planting density with wide-row spacing. Two field experiments were carried out to investigate cotton yield, N use efficiency (NUE), N accumulation characteristics, and 15N uptake and distribution in response to N fertilization. First, a two-year experiment was conducted with N fertilization of either 0, 120, 240, 360 (control) or 480 kg ha−1. A three-year experiment was then carried out with 240 kg N ha−1 being applied with different ratios across three periods (squaring, flowering to peak boll, and late peak boll), i.e., 0:6:4 (N064), 1:6:3 (N163), 2:6:2 (N262, control), 3:6:1 (N361) and 4:6:0 (N460). Compared with conventional N fertilization (360 kg N ha−1), moderate fertilization at 240 kg N ha−1 resulted in steady and higher seed cotton yields of 5945 and 5603 kg ha−1 in 2017 and 2018, respectively, and improved NUE by 49.1–53.6%. Compared with conventional N262, a shift to later N application (N064) increased both lint yield and partial factor fiber productivity of nitrogen (PFFPN) by 4.4–7.7%, and accumulated 6.1–14.4% more total N (K) in reproductive organs due to higher average (Vt) and maximum (Vm) accumulation rates by 25.2–49.0% and 15.0–48.7%, respectively, while the fast N accumulation period (∆t) shortened by 15.2–24.4%. N064 partitioned 15.6% more 15N to reproductive organs. NUE was significantly positively correlated with K, t1 (the day when ∆t started), Vt, Vm, Tm (the day on which Vm occurred) and 15N accumulation in middle and upper canopy bolls, and negatively correlated with ∆t of total N accumulation in reproductive organs. Allocating N from the squaring period to the late peak boll period led to an increase in N uptake during the reproductive growth stage and greater allocation of N to cotton bolls under reduced-N cultivation and drip fertigation. This N management strategy is a potential way to improve NUE and achieve sustainable and efficient production of cotton in arid areas.

A Moderate Wetting and Drying Regime Combined with Appropriate Nitrogen Application Increases Grain Yield and Nitrogen Use Efficiency in Rice

This study investigated whether and how irrigation regimes interact with nitrogen (N) application rates to mediate the grain yield, N use efficiency (NUE) and water use efficiency (WUE) in rice and to understand the underlying mechanism. A field experiment was conducted with two irrigation regimes, continuously flooded (CF) and alternate wetting and moderate drying (AWMD), and three N application rates, 120 kg ha−1 N (a low N rate, LN), 240 kg ha−1 N (a medium N rate, MN) and 360 kg ha−1 N (a high N rate, HN) in 2021 and 2022. The results showed that the grain yield exhibited the lowest values at the LN, regardless of the irrigation regime, while it was the highest at the MN when the CF regime was adopted. The grain yield was comparable between the MN and HN regarding the AWMD regime. AWMD significantly increased the grain yield, NUE and WUE compared to CF at the same N rate, which was attributed to a higher photosynthetic rate, improved population quality, enhanced nonstructural carbohydrate remobilization from stems to grains during grain filling, and elevated activities of enzymes involved in N assimilation in the roots. The results suggest that an AWMD regime combined with MN treatment could pronounce a synergistic interaction on the grain yield, NUE and WUE in rice by improving root and shoot physiological performances.