Nitrogen Use Efficiency Values Research Articles

Effect of nitrogen fertilizer and zinc sulfate on growth, physiological, biochemical and nutrient use efficiency in fodder maize under irrigation regimes

To investigate the effect of nitrogen fertilizer and zinc (Zn) sulfate on growth, physiological, biochemical, and nutrient use efficiency in fodder maize under drought stress, an experiment was conducted during two cropping years 2019 and 2020. The experiment was performed as a split-factorial in the form of a randomized complete block design with four replications. The main factor was irrigation regimes in three levels: full irrigation (without stress or 100% of field capacity), irrigation based on 75% of field capacity, and irrigation based on 50% of field capacity. The first sub-factor included urea fertilizer at three levels of 0, 69, and 138 kg ha−1. The second sub-factor included foliar application of zinc sulfate at three levels of 0, 2, and 4 mg kg−1. The results showed that the highest fresh weight of maize fodder was obtained under conditions of full irrigation and the use of 138 kg ha−1 of N. The use of zinc at all irrigation levels increased the fresh weight of maize fodder. These results confirmed that if higher amounts of N are used, more zinc should be used to achieve a higher yield of maize forage. With the increase in the severity of drought stress, the concentration of nitrogen and phosphorus in the crop tissue, as well as the efficiency of using nitrogen and phosphorus, decreased. The highest value of nitrogen use efficiency was obtained in full irrigation conditions, using 69 kg ha−1 of N and 4 mg kg−1 of zinc. In addition, at all irrigation levels, the efficiency of using this element decreased with increasing zinc consumption.

Optimizing nitrogen use efficiency of six forage grasses to reduce nitrogen loss from intensification of tropical pastures

We aimed to evaluate the effect of different types and rates of nitrogen (N) fertilizers on plant biomass production, nitrogen use efficiency (NUE), and nitrous oxide (N2O) emissions of six tropical forage grass cultivars. This field study was conducted in Colombia under tropical conditions in two phases. Phase 1: we evaluated the effect of different types of N fertilizers (urea; calcium ammonium nitrate (CAN); and urea-ammonium sulfate (U-AS) using a single dose of application of 25 kg N ha−1 cut−1, along with a control treatment for each grass without application of fertilizer) on forage dry matter, crude protein, N uptake, N surplus, and NUE. The study focused on six tropical forage grass cultivars: Urochloa humidicola cv. Tully, U. hybrid cv. Cobra, U. hybrid cv. Cayman, Megathyrsus maximus cv. Mombasa, Cynodon nlemfuensis cv. Stargrass and U. decumbens cv. Basilisk. We found that the biomass production and protein content of each forage grass cultivar responded differently to different N fertilizer types. In consequence, the NUE of each forage grass cultivar was strongly affected by the type of N fertilizer applied. For example, Cayman showed a NUE of 87.8% with CAN and 40.4% with urea, while the NUE of Basilisk with CAN was 8.0% and 76.4% with urea. Maximum NUE values were obtained for Stargrass and Cayman with CAN (91.7 and 87.8%, respectively) and for Mombasa with urea (89.9%). Phase 2: we selected three combinations of forage grass cultivars and type of N fertilizer, and we evaluated the impact of four rates of N application (0, 10, 20, and 30 kg N ha−1 cut−1) on forage production and N2O emissions upon fertilization. In general, higher N fertilization rates increased the accumulated N2O emissions. However, we observed that the fertilization of Stargrass and Cayman grass with a rate of 20 kg N−1 cut−1 and Mombasa grass with a rate of 30 kg N−1 cut−1 were more beneficial than the other rates of N fertilization based on the biomass production and amount of N2O emitted are considered. This study highlights the importance of optimizing NUE in tropical pasture systems using an appropriate design of N fertilization strategy. Inappropriate N fertilizer use can significantly increase the N losses (e.g., through N2O emissions, with a potential contribution from N leaching). These findings provide valuable information for sustainable intensification of productive tropical livestock systems to spare land for other uses.

Understanding nitrogen dynamics in the Brazilian beef industry: A comprehensive decadal analysis

Brazil stands as a prominent beef producer and exporter, witnessing major transformations and expansions in its production chain over the past 20 years. These changes have prompted concerns regarding waste generation and environmental pressure. This study employs material flow analysis (MFA) to quantify nitrogen flows throughout the cattle slaughter process and subsequent beef consumption in Brazil, spanning from 2011 to 2021. The analysis encompasses co-production streams like leather, tallow, viscera, and blood. Nitrogen use efficiency (NUE) and the nitrogen cascade indicator (NCI) were used to evaluate efficiency and nitrogen accumulation in the production chain. Nitrogen inputs in the system increased by 8.47 %, while beef production rose by 7.29 %. In contrast, per capita beef consumption decreased by 1.29 kg, despite an overall consumption increase of 2.84 %, attributed to population growth in Brazil. Beef exports witnessed a notable surge of 86.03 %. Conversely, human excreta and food waste losses experienced increments of 10.88 % and 2.84 %, respectively. Examining NUE reveals the highest values during the slaughter phase (90 %), followed by processing, transportation, and storage stages (79–88 %). The consumption phase exhibited the lowest NUE values (29–34 %). Regarding the cumulative nitrogen effect, the NCI varied between 77 % and 82 % throughout the study period. This highlights opportunities for enhancing nitrogen use efficiency, particularly by addressing food waste at the consumer level. Notably, the study observes nitrogen accumulation across the Brazilian beef production chain, potentially contributing to the nitrogen cascade effect and heightening environmental pressure. Recognizing these dynamics provides avenues for targeted improvements, emphasizing the need to address nitrogen-related challenges and enhance sustainability in the beef production and consumption landscape.

Productivity, economic efficiency and agronomic efficiency of traditional rice varieties as influenced by EM compost and fertilizer nitrogen under Cauvery delta zone of Tamil Nadu, India

Field experiment was carried out at the Experimental farm, Annamalai University, Annamalai Nagar to study the productivity, economic efficiency and agronomic efficiency of traditional rice varieties as influenced by EM compost and fertilizer nitrogen under Cauvery delta zone of Tamil Nadu (2018). The experiment conducted in split-plot design and treatments were replicated thrice, the three traditional rice varieties were assigned as main plot treatments viz., Mapillai samba, Illupai poo samba and Seeraga samba, and integrated nutrient management were assigned as sub plot treatments, it includes control, graded dose of nitrogen alone ant it combination with FYM, EM (effective microorganisms) compost, pressmud, green manure. From the results of field study, among the rice varieties, Mapillai samba significantly recorded higher grain yield of 2574 kg ha-1, straw yield of 3831 kg ha-1 and harvest index of 39.85 and nitrogen use efficiency of 36.58 (NUE) agronomic efficiency of 21.68 (AE) and apparent N recovery (%) of 56.93 (ANR). The aforesaid parameters were least under Illupai poo samba rice variety. In respect of INM treatments, plots received with 75% RDN along with EM compost @ 5 t ha-1 significantly recorded maximum grain yield of 2967 kg ha-1, straw yield of 4341 kg ha-1 and harvest index of 40.56. Also the same treatment recorded higher values of nitrogen use efficiency of 39.56 (NUE), agronomic efficiency of 25.58 (AE) and apparent N recovery (%) of 66.44 (ANR). The lowest grain yield, straw yield and harvest index of rice were registered under control. But lowest values of nitrogen use efficiency (NUE), agronomic efficiency (AE) and apparent N recovery (%) (ANR) were recorded under 100% recommended dose of nitrogen (RDN). In respect of economics, among the treatment combination seeraga samba rice variety received with 75% RDN + EM compost @ 5 t ha-1 registered higher gross return, net return and return per rupee invested.

Improving crop model accuracy in the development of regional irrigation and nitrogen schedules by using data assimilation and spatial clustering algorithms

Crop growth models have been used to develop irrigation and nitrogen schedules (INSs). However, differences in crop cultivar coefficients are often ignored in the development of regional INSs. This study aimed to formulate suitable INSs under spatial heterogeneities in crop cultivar coefficients. Therefore, we propose two strategies for retrieving maize cultivar coefficients by using a data assimilation algorithm and spatial clustering algorithm. The first strategy involves determining the cultivar coefficients for each simulation unit in the examined region and then assigning different cultivar coefficients to the different clusters obtained using a spatial clustering algorithm, with the cultivar coefficients employed as clustering characteristics (CAs). The second strategy involves assigning different cultivar coefficients to the different clusters obtained using a spatial clustering algorithm on the basis of cultivar coefficients and geographical characteristics (CAGCs). By using observational data, the accuracy of cultivar coefficients CAs and CAGCs was compared with that of commonly used regional representative coefficients (RRs) and sub-region representative coefficients (SRRs). Furthermore, we formulated INSs with these four coefficients by using yield maximization as the objective and water use efficiency (WUE) and nitrogen use efficiency (NUE) as constraints. We examined the differences between the INSs, yields, WUE values, and NUE values obtained using each of the aforementioned four coefficients and those obtained using a point optimization approach. The results revealed that the highest accuracy in the simulation of the regional leaf area index, yield, and phenological stage was exhibited by the CAGCs-based strategy, followed by the CAs-based strategy. The RRs-based and SRRs-based strategies produced considerable errors. Crucially, the INSs obtained using the CAGCs-based strategy were more similar to those obtained through point optimization and more reasonable than were the INSs obtained using the other three strategies. In addition, more accurate yield, WUE, and NUE values were obtained with the CAGCs-based strategy than with the other three coefficients-based strategies. The results of this study indicate that the combination of a data assimilation algorithm and spatial clustering algorithm can improve the application potential of crop models in agricultural systems.

Effect of using reclaimed water via furrow and subsurface drip systems under alternate partial root-zone irrigation mechanism on crops growth and soil properties

The growing population in the face of water scarcity inevitably necessitates the quest for alternative sources of irrigation water, which integrates them with irrigation strategies for improved agricultural productivity to meet the Sustainable Development Goals. A three-year field experiment was conducted in 2017, 2018, and 2019 to investigate the effect of water quality (reclaimed water (RW) and clean water (CW)), irrigation techniques (subsurface drip irrigation (SDI) and furrow irrigation (FUI)), irrigation methods (full irrigation (FI) and alternate partial root-zone irrigation (APRI) (70% ETc)), and their interactions on the fresh fruit yield (FY), irrigation water use efficiency (IWUE), and nitrogen use efficiency (NUE) of tomatoes. Further, electrical conductivity (EC), pH, and organic matter (OM) of soil were evaluated. The experiments were undertaken over three growing spring seasons in a greenhouse at the Chinese Academy of Agricultural Sciences in Henan Province, China. Throughout the three years of this study, the yield, the IWUE, and the NUE values of all treatments under RW were higher than those corresponding values under CW. The trend was the same under SDI as it was under FUI. Statistical analyses revealed that there was no significant effect (P > 0.05) of water quality, irrigation technique, and irrigation methods on the soil EC, pH, and OM over the three years. In addition, the interaction between the different experimental factors over the three years of the study was not significant. In conclusion, the application of RW under SDI can result in saving CW and increasing productivity without any negative effect on the investigated soil properties. Furthermore, when RW-SDI is used in conjunction with APRI, it can result in increasing IWUE.

Effect of replacing synthetic nitrogen fertilizer with animal manure on grain yield and nitrogen use efficiency in China: a meta-analysis.

To reduce reliance on synthetic nitrogen (N) fertilizer and sustain food production, replacing synthetic N fertilizer with animal manure as an effective method is widely used. However, the effects of replacing synthetic N fertilizer with animal manure on crop yield and nitrogen use efficiency (NUE) remain uncertain under varying fertilization management practices, climate conditions, and soil properties. Here, we performed a meta-analysis of wheat (Triticum aestivum L.), maize (Zea mays L.), and rice (Oryza sativa L.) based on 118 published studies conducted in China. Overall, the results indicated that substituting synthetic N fertilizer with manure increased yield by 3.3%-3.9% for the three grain crops and increased NUE by 6.3%-10.0%. Crop yields and NUE did not significantly increase at a low N application rate (≤120 kg ha-1) or high substitution rate (>60%). Yields and NUE values had higher increases for upland crops (wheat and maize) in temperate monsoon climate/temperate continental climate regions with less average annual rainfall (AAR) and lower mean annual temperature (MAT), while rice had higher increases in subtropical monsoon climate regions with more AAR and higher MAT. The effect of manure substitution was better in soil with low organic matter and available phosphorus. Our study shows that the optimal substitution rate was 44% and the total N fertilizer input cannot be less than 161kg ha-1 when substituting synthetic N fertilizer with manure. Moreover, site-specific conditions should also be considered.

Compost and plant growth-promoting bacteria enhanced steviol glycoside synthesis in stevia (Stevia rebaudiana Bertoni) plants by improving soil quality and regulating nitrogen uptake

Stevia ( Stevia rebaudiana Bertoni) is an important industrial crop, and its leaves contain steviol glycosides (SGs), which are valuable compounds because they are characterized by a high sweetness and low caloric content. SGs yield depends on nitrogen (N) nutrition; however, the role of N uptake in SGs synthesis needs clarification, especially in organic farming systems that depend on organic and biofertilizers. Plant growth-promoting bacteria (PGPB; i.e., Azospirillum brasilense and Bacillus circulans ) and compost were used to study the effect of N nutrition on SGs yield. The experiment consisted of five N treatments with or without PGPB inoculation. The fertilization treatments were: C = without N, T 1 = urea, T 2 = compost, T 3 = urea and compost (75% of N from urea and the rest from compost) and T 4 = urea and compost (50% of N from urea and the rest 50% from compost). Compost and PGPB increased the soil quality indicators and enhanced the synthesis of chlorophyll and nutrient uptake by stevia plants. Mixtures of compost and urea under inoculation with PGPB enhanced soil microbes and enzymatic activity. The highest significant value of nitrogen use efficiency (NUE) resulted from urea alone, while the maximum phosphorus (P) and potassium (K) uptake came from compost. Although urea led to an increase in stevia N uptake, it led to a clear decrease in SGs yield. Urea decreased the total soluble sugar and leaf C/N ratio by 29% and 31%, respectively, compared to those of C. T 4 increased the SGs concentration by 74% and 46%, respectively, compared to that of urea alone in the presence and absence of PGPB. PGPB enhanced the soil quality and promoted nutrient uptake, resulting in significant increases in SGs yield. Regulating N uptake enhanced synthesis of soluble sugars and increased the C/N ratio, which caused an increase in SGs production. The use of compost and plant growth-promoting bacteria is a suitable strategy to produce stevia plants with low rates of inorganic nitrogen without any yield loss. • Compost and plant growth-promoting bacteria (PGPB) enhances stevia growth. • Compost and PGPB reregulate N-uptake in stevia plants. • Urea decreased the total soluble sugar and leaf C/N ratio. • Regulating N-uptake increased the synthesis steviol glycosides (SGs). • The findings might be an aid for sustainable N management in stevia production.

Nitrogen budgets and nitrogen use efficiency as agricultural performance indicators in Lake Victoria basin

Too little nitrogen (N) is a threat to crop productivity and soil fertility in sub-Saharan Africa (SSA). Nitrogen budgets (NB) and nitrogen use efficiency (NUE) are critical tools for assessing N dynamics in agriculture and have received little or no attention in the region. Data were collected from smallholder farmers clustered into two categories, farmers applying and farmers not applying N fertilizers. NB were calculated using the Coupled Human and Natural Systems (CHANS) model approach for field and farm spatial scales. The results showed spatial variabilities in NB and NUE at the field level (maize and rice) across all the catchments. At the field level, N balances were negative for the two crops in all the catchments. Similarly, at the farm gate, a deficit of −78.37 kg N ha−1was observed, an indicator of soil N mining. NUE values at the field scale varied across the catchments for both crops, with values for maize grown without N ranging from 25.76 to 140.18%. Even with the application of mineral N at higher levels in rice fields compared to maize fields, NUE values ranged between 81.92 and 224.6%. Our study revealed that the Lake Victoria region suffers from inefficient N cycling due to depleted soil N pools and low synchrony between N input and N removal. Therefore, a challenge lies in exploiting more sustainable N sources for farmers in the region for sustainable farming systems. The NB and NUE provide critical information to agriculture stakeholders to develop environmental, agronomic, and economically viable N management solutions.

Grafting Eggplant Onto Underutilized Solanum Species and Biostimulatory Action of Azospirillum brasilense Modulate Growth, Yield, NUE and Nutritional and Functional Traits

The grafting of vegetable crops is considered a valuable mean for ensuring the yield and quality under different cultivation conditions. Simultaneously, there are increasing research efforts in exploiting underutilised plants as potential rootstocks for vegetables to increase the sustainability of horticultural systems. In accordance with the European Green Deal, the application of biostimulants is a fashionable and ecological agronomic practice to enhance the production and quality of vegetables. Thus, the current research appraised the synergistic effect of grafting eggplant onto various allied potential rootstocks (Solanum torvum, S. aethiopicum and S. macrocarpon) and of applying a plant growth-promoting bacteria (Azospirillum brasilense DSM 2298) on eggplant growth, production, fruit quality traits (nutritional and functional features) and nitrogen use efficiency (NUE). The findings showed that ‘Gloria’ F1 plants grafted onto S. torvum or S. aethiopicum had a significant increase in plant height 50 DAT by 11.6% and 9%, respectively, compared with not grafted plants. Simultaneously, plants inoculated with A. brasilense DSM 2298 acquired a significant upsurge of plant height 50 DAT by 6% compared with the control. Our results revealed that S. torvum and S. aethiopicum-grafted plants improved their marketable yield by 31.4% and 20%, respectively, compared with not grafted ones. Furthermore, A. brasilense DSM 2298 significantly boosted the yield compared with the control plants. Plant type had no effect on fruit dry matter and firmness, whereas plants grafted onto S. macrocarpon showed a significant increase in the soluble solids content (SSC) and fruit K concentration compared with not grafted plants. Plants grafted onto S. torvum rootstock and inoculated with A. brasilense DSM 2298 had a significant increase in fruit protein concentrations compared with the combination not grafted × control. Moreover, S. torvum-grafted plants and those inoculated with the microbial biostimulant revealed the highest NUE values. The results evidenced that S. torvum and S. macrocarpon-grafted plants, inoculated with A. brasilense DSM 2298, had the highest ascorbic acid (average 7.33 and 7.32 mg 100 g−1 fw, respectively). Interestingly, S. torvum rootstock increased the chlorogenic acid concentration and reduced the glycoalkaloids concentration compared with not grafted plants. Our data also showed that A. brasilense DSM 2298 significantly increased SSC by 4.5%, NUE by 5.5%, chlorogenic acid concentration by 2.0% and the total anthocyanins by 0.2% compared to the control. Thus, our study underlined that S. aethiopicum rootstocks inoculated with A. brasilense DSM 2298 could represent a valid substitute to the common S. torvum rootstock.

Assessment of the 2006 Abuja Fertilizer Declaration With Emphasis on Nitrogen Use Efficiency to Reduce Yield Gaps in Maize Production

The Abuja Fertilizer Declaration in 2006 recommended the increase of fertilizer use from the current practice for Sub-Saharan Africa (SSA) to achieve food sufficiency and improve soil fertility status. However, the current recommended rates of fertilizer have not been evaluated for specific crops on their potential to reduce the yield gap and optimize nitrogen use efficiency (NUE). In this study, with nitrogen (N) being a significant yield-determinant nutrient, four N use scenarios were drawn from existing recommendations and were evaluated under field conditions for maize crops in two catchments of the Lake Victoria basin. The scenarios included Business as Usual (BAU, 0 kg N ha−1), 25% of the Abuja declaration (ADS 12.5 kg N ha−1), 50% of the Abuja declaration (ADS 25 kg N ha−1), and Abuja declaration–Abuja scenario (ADS, 50 kg N ha−1). The results revealed that increasing N input levels significantly influenced the growth and yield of maize crops. The ADS scenario recorded the highest grain yield increase (167.39%) in Nyando and 103.25% in Rangwe catchments compared to the BAU scenario. N deficits were observed in all the N use scenarios with a range of −66.6 to −125.7 kg N ha−1 in Nyando and −62.5 to −105.4 kg N ha−1 in Rangwe catchments with the 50% ADS scenario having the highest deficits. The deficits imply that the added N input is insufficient to create an N balance for optimal NUE with consequent high risks of soil N mining. In both catchments, all N use scenarios were within the recommended agro-physiological N efficiency (APEN) level of between 40 and 60 kg kg−1 N. The partial N balance obtained at Nyando (1.56–3.11) and Rangwe (1.10–4.64) was higher than the optimal values, a sign of insufficiency of N inputs and possible risk of soil N depletion in all the scenarios. Our findings conclude that the proposed N rates in the region are still very low for food sufficiency and optimized NUE. Therefore, there is a need to explore other sources of N such as biological N fixation and organic manure and inform policy- and decision-makers to recommend higher rates beyond the “Abuja declaration” with the prospect of reaching target yield and optimizing NUE values based on specific crop recommendations.

Nitrogen use efficiency trends for sustainable crop productivity in Lake Victoria basin: smallholder farmers’ perspectives on nitrogen cycling

Nitrogen Use Efficiency (NUE) is one of the established metrics for benchmarking management of Nitrogen (N) in various systems. Numerous approaches to calculate NUE exist, making it difficult to compare the performances of systems depending on the methodology used. This study adopted the conceptualized framework by European Union Nitrogen Expert Panel (EUNEP) to calculate NUE values for cereal crops to determine future trends for the first time in the Lake Victoria region. Data were collected through in-person interviews among maize and rice smallholder farmers within the Lake Victoria region. A total of 293 observations were recorded. Collected data on yield and N fertilizer were used to make projections on the changes of NUE based on scientific and policy recommendations for Sub-Saharan Africa for 2020 (base year), 2025, 2030, and 2050. Significant differences in maize grain yield for both fertilized and unfertilized farms were observed with very low yields of 2.4 t ha−1 (fertilized) and 1.4 t ha−1 (unfertilized). The graphical representation of NUE of both maize and rice showed that most farmers were in the zone of soil N mining. Projected results showed that most maize farmers within Lake Victoria region will continue to experience NUE values >90%, low N inputs <50 kg N ha−1) and less than 5 t ha−1 maize crop yield over the years. For rice farmers, Nyando and Nzoia catchments had surpassed the set target of both yield (6 t ha−1) and N input (50 kg N ha−1). However, NUE values remain higher than the optimal ranges of 50%–90% (127.14%−267.57%), indicating risks of depleting soil N status. The unbalanced N fertilization also showed a trend below the linear neutrality option and the average N output for good N management for both crops. Therefore, farmers need to explore various crop management options that could increase N use efficiencies. This should be coupled with policies that promote farmers to access more N input and advocate for optimal management of N and improved quality of the cereals.

Temporal and spatial variations in nitrogen use efficiency of crop production in China

The low value of nitrogen use efficiency (NUE) (around 30%) of crop production in China highlights the necessity to adopt reasonable N managements in national scale. After the implementation of ‘National Soil Testing and Formulated Fertilization’ program in 2005, many field experiments have reported an increase of NUE for crop productions in China. This has prompted discussion regarding the extent to which NUE in crop production has been improved. Here, we analyzed the temporal and spatial changes in NUE (crop N uptake/total N input) and cumulative synthetic and non-synthetic N fertilizer recovery efficiency of crop production in China during 1980–2014, and evaluated the relationship between NUE and economic growth (purchasing power parity, PPP) at national and provincial scale. The results showed that the overall NUE of crop production in China clearly increased from 35 to 42% during 2003–2014, and an increase in NUE was further evidenced by increases in cumulative recovery efficiency of both synthetic and non-synthetic N fertilizer. The relationship between NUE and PPP can be described by an environmental Kuznets curve at the national scale, with NUE first decreasing then increasing with PPP. However, this relationship exhibited large spatial variation: 1) In economically developed (e.g., Guangdong and Zhejiang) and undeveloped provinces (e.g., Yunnan and Guizhou), NUE generally decreased and then remained at low levels (20–35%) as PPP increased. 2) In major agricultural provinces with high (e.g., Shandong and Jiangsu) or intermediate levels (e.g., Hunan and Hebei) of economic development, a pronounced increasing trend in NUE with PPP was observed. These results highlight the necessity of developing region-oriented N management strategies to further increase the NUE of crop production in China, particularly in the economically developed and undeveloped provinces.

Different quantification approaches for nitrogen use efficiency lead to divergent estimates with varying advantages.

Nitrogen use efficiency (NUE) is a key indicator with which to study nitrogen cycles and inform nitrogen management. However, different quantification approaches may result in substantially divergent NUE values even for the same production system or for the same experimental plot. Based on our investigation of the differences between and connections among the three principal approaches for NUE quantification, we offer recommendations for choosing the appropriate approach and call for long-term observations to assess the impacts of management practices.

Suitable fertilizer application depth can increase nitrogen use efficiency and maize yield by reducing gaseous nitrogen losses

During spring maize production, nitrogen is lost in the form of gaseous N because of shallow fertilizer application, which leads to a low nitrogen use efficiency (NUE). However, the specific effects of the fertilization depth on the losses of gaseous nitrogen (NH3 and N2O) from the soil are unclear. During 2019 and 2020, we established a field experiment with spring maize (Zea mays L.) to test the effects of different fertilizer placement depths of 5 cm (D5), 15 cm (D15), 25 cm (D25), and 35 cm (D35) on the NUE and gaseous nitrogen loss intensity (GNLI). The losses of N in the forms of NH3 and N2O were measured throughout the maize growth period. The trends in terms of NH3 volatilization, N2O emissions, and nutrient uptake were similar for different fertilizer depths during 2019 and 2020. NH3 was the main form of gaseous nitrogen lost compared with N2O. The ratio of gaseous nitrogen loss relative to nitrogen application (GNLR) was 13.11%, and the GNLI was 3.43 g N kg−1 grain under D5. Compared with D5, the GNLR values were 34.77%, 54.67%, and 70.23% lower under D15, D25, and D35, respectively, and the GNLI values decreased significantly by 31.27%, 49.91%, and 54.12%. The nitrogen uptake amounts by maize were 8.07% and 17.41% higher under D15 and D25 during the two years, respectively, while the NUE values were 17.79% and 38.37% higher, and the maize yields were 5.68% and 13.83% greater compared with D5. Structural equation modeling showed that 79% of the NUE could be explained by the differences in the fertilization depth. Therefore, deep-band placement fertilizer at a depth of 25 cm can reduce GNLI by decreasing the NH4+-N concentration in the surface layer to ultimately increase the nitrogen uptake, NUE, and maize yield. Deep-band placement fertilizer is a suitable method for supporting the development of agricultural ecosystems.

Optimizing Nitrogen Recommendations for Tillage and Corn Residue Management in Irrigated Wheat, Southern Iran

ABSTRACT In southern Iran, intensive tillage operations and residue removal have been the major cause of declining crop productivity and nitrogen-use efficiency (NUE). A 2-year field experiment (2016–2017) was conducted to test four nitrogen (N) rates (0, 101, 152, and 202 kg N ha−1) and tillage practices (conventional, CT; reduced, RT; and no tillage, NT) effects on irrigated wheat (Triticum aestivum L.) grown with or without corn (Zea mays L.) residue removal, using a split-plot design with three replications near Shiraz, Iran. After 2 years, wheat yields were tended to be increased with increasing N rates from 101 to 202 kg N ha−1 under RT with residue retention. Increasing N rate decreased NUE values particularly N physiological efficiency (PEN). Likewise, the lowest NUE was obtained under NT, while RT and CT either showed similar effects or RT was superior over CT. Furthermore, the NNI value around 1 was obtained at 152 kg N ha−1 under RT, when crop residues were retained or removed. Our research has shown that replacing CT with conservation tillage (especially RT) with residue retention and 152 kg N ha−1 can greatly protect wheat yield and optimize NUE values under wheat- and corn in a rotation, but it is based on the short-term results and evaluation of long-term experiment is highly recommended.

Co-application of controlled-release urea and a superabsorbent polymer to improve nitrogen and water use in maize

ABSTRACT A field experiment consisted of two types of N fertilizer, controlled release urea (CRU) and normal urea (U), in combination with three SAP application rates (0, 45 and 90 kg ha−1) in a split-plot design was conducted in 2018 and 2019. The successive release of N from polymer-coated urea corresponded well to the N requirements of maize growth. The NO3 −-N and NH4 +-N contents in the 0–20 cm soil layer were enhanced at the jointing and 12 leaf collar stages, and the leaching of soil NO3 −-N was reduced by using CRU. The application of superabsorbent polymer (SAP) increased soil water stock, decreased evapotranspiration, and enhanced water use efficiency (WUE) and nitrogen use efficiency (NUE). The combined application of CRU and 90 kg ha−1 SAP achieved maximal maize yield, WUE, NUE, and net income values that were 0.8–32.9%, 0.2–37.4%, 4.1–13.1%, and 2.8–42.1%, respectively, higher than those of other treatments. These results demonstrate that the co-application of CRU and 90 kg ha−1 SAP is an effective practice that enhances the water and N utilization of maize and could potentially have wide application on the North China Plain.

Review of Active Optical Sensors for Improving Winter Wheat Nitrogen Use Efficiency

Improvement of nitrogen use efficiency (NUE) via active optical sensors has gained attention in recent decades, with the focus of optimizing nitrogen (N) input while simultaneously sustaining crop yields. To the authors’ knowledge, a comprehensive review of the literature on how optical sensors have impacted winter wheat (Triticum aestivum L.) NUE and grain yield has not yet been performed. This work reviewed and documented the extent to which the use of optical sensors has impacted winter wheat NUE and yield. Two N management approaches were evaluated; optical sensor and conventional methods. The study included 26 peer-reviewed articles with data on NUE and grain yield. In articles without NUE values but in which grain N was included, the difference method was employed to compute NUE based on grain N uptake. Using optical sensors resulted in an average NUE of 42% (±2.8% standard error). This approach improved NUE by approximately 10.4% (±2.3%) when compared to the conventional method. Grain yield was similar for both approaches of N management. Optical sensors could save as much as 53 (±16) kg N ha−1. This gain alone may not be adequate for increased adoption, and further refinement of the optical sensor robustness, possibly by including weather variables alongside sound agronomic management practices, may be necessary.

Scope and strategies for sustainable intensification of potato production in Northern China

AbstractPotato (Solanum tuberosum) is an important staple crop in China, however, potato yields are low, and thus a general aim is to produce more crop with fewer resources and minimal environmental effects. This study aimed to assess the relationships between yield, resource use efficiencies, and environmental performance of potato production in China. Three major potato production regions (Inner Mongolia, Gansu, and Heilongjiang) were surveyed. The current production performance was evaluated, and the scope for improvement was assessed based on a lower and upper target for yield (financial breakeven point and 85% of the potential yield, respectively), water productivity (upper target is 85% of the potential water productivity), nitrogen use efficiency (50 and 90%) and nitrogen surplus (upper target is 80 kg ha−1). Long‐term situations were evaluated to identify the target values of nitrogen use efficiency and nitrogen surplus based on currently available technologies. The results indicate that in the short‐term nitrogen fertilizer input can be reduced by allowing for soil nitrogen mining to improve the nitrogen use efficiency and reduce nitrogen surplus. Water productivity can be increased by enhancing yield, and water surplus can be reduced by more efficient management of irrigation and rainfall water. In the long‐term, with good agronomy, we assess it is feasible to improve yield (from 33–43 to 46–57 t FM ha−1), improve nitrogen use efficiency (to 84%), and reduce nitrogen surplus (from 50–156 to 16–34 kg N ha−1) simultaneously. The latter should be validated experimentally.

Crop yield after 5\xa0decades of contrasting residue management

The benefits of soil organic input on crop yields have long been discussed, yet details of their relationship remain controversial. This study considers the effects of different residue management on crop performance as assessed by yield and nitrogen use efficiency (NUE). Three residue management (residue removal, residue incorporation, and residue incorporation + added poultry manure), combined with five levels of N application, were studied in a long-term experiment starting in 1966. Crop residue incorporation improved maize yield by 12% (nutritional effect) and sugar beet yield by 16% (non-nutritional), and the combination of crop residue incorporation with added poultry manure increased both winter wheat and sugar beet yields by 8% (nutritional effect). The NUE values of mineral fertiliser were almost three-fold those of residues and the combination of residue with poultry manure, except in sugar beet and maize, where NUE of mineral fertilizer approached those observed for residues (0.44 vs 0.45, on average). In wheat, NUE for residue incorporation with added poultry manure was nearly double the NUE for residues alone. Residue management effects depended on crop type; spring-sown crops showing stronger effects than those sown in autumn. Residues primarily produced a nutritional effect, suggesting that they decomposed within 1 year. While residue use offers little potential for soil improvement, it does reduce the need for fertilisers.