Increase In Nitrogen Use Efficiency Research Articles

Application of Potassium along with Nitrogen under Varied Moisture Regimes Improves Performance and Nitrogen-Use Efficiency of High- and Low-Potassium Efficiency Cotton Cultivars

Low nitrogen-use efficiency (NUE) is a serious issue for cotton production and environmental sustainability in arid climates. A pot study was conducted to evaluate the effect of K nutrition on NUE and performance of low- and high-K-efficiency cotton cultivars under two moisture regimes. Treatments included two soil moisture levels—i.e., normal irrigation, 100% available water content (AWC); reduced irrigation, 50% AWC—three levels of nitrogen (N)—i.e., 0, 375, and 750 mg N pot−1—and two K levels, i.e., 0 and 208 mg K pot−1. Results reveal that 208 mg K pot−1 application with nitrogen significantly enhanced the N-use efficiency, growth, and yield attributes of both cotton cultivars compared with sole N fertilization. Similarly, the combined application of NK @ 375 N + 208 K mg pot−1 caused up to 83% increase in NUE under AWC50% and AWC100%, as compared with NK control (0 N + 0 K). Compared with the control, imposed low-moisture stress caused a decrease of 13.9% in stomatal conductance (gs), 2.5% in transpiration rate (E), and 6.5% in net photosynthetic rate (PN), respectively. The physiological water use efficiency (PN/E) decreased by 13.2% under AWC50%. Applied NK @ 375 N:208 K, mg pot−1 caused 27.39 and 27.56% improvement in the PN/E in HKE and LKE cultivars under AWC50%, respectively. The HKE cultivar, i.e., CIM-554, maintained the highest gs and PN than FH-901, that was low-K-efficiency cultivar. The study suggests that varietal selection and adequate K fertilization have the prospects to improve NUE and save considerable quantities of fertilizer and irrigation water in cotton production under arid environments.

Synergistic effects of biological nitrification inhibitor, urease inhibitor, and biochar on NH3 volatilization, N leaching, and nitrogen use efficiency in a calcareous soil–wheat system

Urease inhibitors (UIs), chemical nitrification inhibitors (CNIs), and biochar (BC) are commonly applied nitrogen (N) management strategies in reducing soil N loss and increasing nitrogen use efficiency (NUE) in agriculture. Biological nitrification inhibitors (BNIs) are natural abilities of certain plant roots to suppress soil–nitrifier activity. They have some advantages over chemical nitrification inhibitors (CNIs), but their effects on N loss and NUE are not critically examined yet. In this study, the synergistic effects of BNI of methyl 3-(4-hydroxyphenyl) propionate (MHPP at dosage of 1000 mg kg−1), UI of N-(n-butyl), thiophosphoric triamide (NBPT, 2% of applied_urea_N), and BC (w heat straw biochar, 1% (w/w)) on NH3 volatilization, inorganic N leaching, plant N uptake (N_yield), and NUE are explored through a wheat growth pot experiment. MHPP and BC can increase NH3 volatilization, which increased by 18.5% in the BC treatment and 32.9% in the MHPP_BC treatment. Individual application or co-application of MHPP, NBPT, and BC significantly decreased N leaching by 25.4% to 42.6% (P < 0.05). The treatments of MHPP, BC, MHPP_NBPT, and MHPP_BC significantly increased the N_yield in the range of 7.41%–10.3% and the NUE in the range of 9.94%–13.7% compared with the CF treatment (P < 0.05). The partial mechanism of those strategies in regulating N pathways was by causing niche differentiation between ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA), and changing community structure mainly of AOB. NBPT, MHPP, and BC were found mainly in the targeted Nitrosospira cluster 3a.2 and Nitrosospira cluster 3b. In general, the application of MHPP_NBPT is a promising strategy for simultaneously reducing NH3 and increasing NUE.

Consolidation of agricultural land can contribute to agricultural sustainability in China.

China's agricultural sector is dominated by smallholder farms, which mostly exhibit relatively low nutrient use efficiency, low agricultural income and substantial non-point-source pollution. Here we assess the spatial feasibility and cost-effectiveness of agricultural land consolidation in China by integrating data from over 40,000 rural surveys, ecological modelling and geostatistical analysis. We found that 86% of Chinese croplands could be consolidated to establish a large-scale farming regime with an average field size greater than 16 ha. This would result in a 59% and 91% increase in knowledge exchange and machinery use, respectively, contributing to a 24% reduction in total nitrogen input, an 18% increase in nitrogen use efficiency and a 39% reduction in labour requirement, while doubling labour income. Despite requiring a one-time investment of approximate US$370 billion for land consolidation, total agricultural profits would double due to agricultural production costs being halved.

Rare metals trade: Year-on-year growth in Japanese imports since Apr 2021

Nitrogen (N) has played an important role in the global economy, food security, and environmental sustainability. However, the recent developments in nitrogen science have raised concerns about the negative impacts of the excessive and imbalanced use of N on human health, ecosystem, and environmental sustainability. It is being argued that improving nitrogen use efficiency (NUE) and reducing N losses are critical for a country to be food secure and environmentally healthy. Recent advances in nitrogen management suggest that a range of technological solutions and policy instruments are needed to tackle “the nitrogen challenge.” Globally, different policies have started recognizing the nitrogen challenge and suggesting measures for sustainable N use across different sectors. Pakistan is one of the leading nitrogenous fertilizer consuming countries in the world, but its average NUE is far below than the global average. Low NUE has led to a massive concurrent N surplus that is being lost to the environment in one or the other way. Currently, Pakistan lacks institutional and regulatory frameworks to address and control the damaging effects of excessive and imbalanced N use. Yet, there is no direct N management policy available in Pakistan and the indirect N-related policies do not adequately address “the nitrogen challenge.” Given this scenario, the institutional and regulatory setup requires modernization of all practices and procedures involved in N production to consumption encompassing all relevant sectors such as agriculture, livestock, transport, and industry to reduce N waste and emissions and increase NUE. Reducing N waste and increasing NUE will help Pakistan reap benefits for environmental sustainability, food security, and overall economy.

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.

Localized nutrient supply can facilitate root proliferation and increase nitrogen-use efficiency in compacted soil

Soil compaction constrains root growth and crop yield. Previous studies have shown that localized nutrient supply can significantly improve maize plant growth in field conditions at the early growth stage. However, this promoting effect has not been tested in the compacted soil. We describe 2-year field experimentation on a fluvo-aquic soil in the North China Plain to investigate the effect of localized vs. broadcast ammonium and phosphorus supply on maize under three soil compaction treatments (NC: non-compacted, C: compacted and SC: severely compacted) during 2012 and 2013. Results showed that compared with broadcast ammonium and phosphorus (BNP), localized ammonium and phosphorus supply (LNP) resulted in significantly higher PFPN in the NC (by 31–37%), C (by 43–44%) and SC (by 45%) treatments at harvest. When soil was compacted (C and SC), the enhancement of nitrogen (N) utilization in the LNP treatment was attributed to the increased root growth, including greater specific root length (a greater proportion of fine roots), lower root tissue density and deeper rooting at the seedling stage, especially in the compacted treatment (C). The enhanced root penetration capacity contributed to the increased N and water uptake from the deep soil layers. Our study highlighted the importance of nutrient management for mitigating negative impacts of soil compaction on crops, and will underpin new soil compaction management practices by considering optimal fertilization to strengthen the root-soil interactions.

Benefits of controlled-release/stable fertilizers plus biochar for rice grain yield and nitrogen utilization under alternating wet and dry irrigation

Identifying approaches to producing greater amounts of rice with higher water productivity (WP) and nitrogen use efficiency (NUE) is a major challenge for economical, environmentally friendly rice production. Despite the advantages of controlled-release N fertilizers, few studies have investigated their effects on rice agronomic performance, grain yield, NUE and WP under different irrigation regimes. In this study, a three-year field experiment was conducted in Zhejiang, South China, with two irrigation regimes (flood irrigation, FI; alternating wet and dry irrigation, AWD) and five N application methods (zero N, N0; the conventional N level, PUN100; 80 % of the conventional N level, PUN80; 80 % of the conventional N level applied as controlled-release N fertilizer and urea, plus biochar, CRFN80-BC; and 80 % of the conventional N level applied as stable compound N fertilizer and urea, plus biochar, SFN80-BC) using the indica hybrid rice cultivar Zhongzheyou 1. Compared with FI, AWD significantly increased rice yield, irrigation WP (WPi) and irrigation plus rainfall WP (WPi+r), and the values of these variables under CRFN80-BC and SFN80-BC were significantly higher than those under PUN80 and PUN100 (P < 0.05). Under AWD, compared to those under PUN100, rice grain yield, nitrogen recovery efficiency (NRE) and WPi+r under CRFN80-BC were 6.6 %, 28.5 % and 6.6 % higher, respectively, and 10.6 %, 44.6 %, and 10.6 % higher, respectively, under SFN80-BC on average over the three years. The higher rice yield was accompanied by higher crop growth rate (CGR) and grain “sink” capacity, as indicated by higher effective panicle and grain spikelet numbers and grain-filling rates. Under CRFN80-BC and SFN80-BC, AWD enhanced dry matter (DM) and N accumulation in the rice vegetative organs (functioning as “sources” for the grains) before the heading (HD) stage and the masses, ratios and contributions of DM and nonstructural carbohydrates (NSCs) transferred from the stems/sheaths and of N transferred from the leaves (as “flow”) from the rice HD to maturity (MA) stages compared with those in PUN80 and PUN100. These results indicate that maintaining the source-sink-flow balance of carbohydrates and N in rice helps increase rice grain yield and NUE; the significant and positive correlations among these parameters confirm this interpretation. Overall, the results suggest that under AWD, controlled-release/stable N fertilizers plus biochar can increase the grain yield, NUE and WP of rice.

Controlled‐release urea improved cotton productivity and nitrogen use efficiency in China: A meta‐analysis

AbstractThe use of controlled‐release urea (CRU) is recommended to improve crop productivity without compromising environmental quality, but the overall effects on cotton (Gossypium hirsutum L.) growth are not well studied. A meta‐analysis was conducted to evaluate the effectiveness and potential role of CRU in improving cotton productivity in China. The results indicated that CRU increased cotton yield by 9.8% and nitrogen use efficiency (NUE) by 19.4% relative to urea at equal N rates, although the increase in yield was not statistically significant. Cotton yield increases were greater in sandy‐textured soil than in loam or clay soil, and in experiments sustained for more than 2 yr than in experiments sustained for 1 yr. In addition, the increase in NUE with CRU was enhanced at medium (170 &lt; N ≤ 220 kg N ha−1) and high N rates (&gt;220 kg N ha−1), at high CRU blending ratios (≥70%) and in soils with pH &gt;7.5. These results demonstrate that CRU should be more widely used for cotton production in China, especially in sandy‐textured soil with increased N application.

Application of biochar-coated urea controlled loss of fertilizer nitrogen and increased nitrogen use efficiency

BackgroundThe use of biochar-based N fertilizers have been considered among the most effective strategy for reducing nitrogen loss and improving nitrogen use efficiency (NUE). However, effect and mechanism of biochar-coated urea (BCU) controlling the loss of nitrogen from soil and NUE are rarely reported.MethodologyIn this study, a 65-d culture pot experiment of oilseed rape was used to investigate the impact of BCU on nitrogen leaching, ammonia volatilization, soil nitrogen concentrations, soil pH, nitrogen uptake, NUE and oilseed rape biomass as compared with urea and urea combined with biochar at same nitrogen level.ResultsResults showed that the application of BCU could minimize nitrogen loss mainly by reducing nitrate leaching loss; which could be attributed to the slow-release performance of BCU, followed by biochar induced adsorption/fixation of nitrogen due to the porous nature and surface functional groups of biochar. However, the application of BCU enhanced ammonia volatilization due to the increase of soil NH4+–N concentration and pH value of microenvironment around urea by BCU. The application of BCU increased NUE by about 20% when compared with urea, since BCU reduced losses of nitrogen fertilizer and increased concentration of nitrogen in the soil as well as nitrogen uptake in oilseed rape. Furthermore, the reduction of nitrogen application by 20% when BCU served as a nitrogen source not only reduced nitrogen loss but significantly improved NUE, with no negative effect on the biomass of oilseed rape.ConclusionBCU can serve as a promising control release nitrogen fertilizer for reducing loss of nitrogen and increasing NUE. However further investigations are required to validate the dosage-effect relationship of BCU on crop yield at the field scale.

Comparative life cycle assessment of technologies and strategies to improve nitrogen use efficiency in egg supply chains

A non-trivial challenge along egg supply chains is inefficient use of nitrogen, which may have a combination of negative economic, human/animal health, and environmental implications. A variety of technologies and management strategies have been proposed to improve nitrogen use efficiency (NUE) and reduce emissions at key supply chain stages. This study considered seven scenarios representing NUE strategies: (1) biochar addition to the soil and (2) application of the “4Rs” approach to fertilizer management in feed input production; (3) a reduced crude protein supplemented with synthetic amino acids diet; (4) use of acid scrubbers in poultry barns; (5) biochar addition to stored manure; (6) manure incorporation at the time of land application; and (7) joint application of all strategies. ISO 14044 compliant environmental life cycle assessment (LCA) along with NUE calculations were performed to analyze and compare these mitigation options. The functional unit was one tonne of egg production at the farm gate in Canada. The most significant increase in NUE (13%) resulted from the application of the scrubber in the layer barn. The scrubber also significantly lowered acidifying (21%) and eutrophying (16%) emissions compared to the baseline. The combined application of all strategies increased NUE by 15% compared to the baseline scenario and reduced acidification, global warming, and eutrophication potential, but at the cost of a large increase in energy consumption. Each strategy might be more or less suitable depending on the considered environmental impacts, as well as NUE outcomes. Use of LCA is essential to informed decision making in this context.

Increased nitrogen use efficiency in crop production can provide economic and environmental benefits

Potential economic and environmental benefits of increasing nitrogen-use efficiency (NUE) are widely recognized but scarcely quantified. This study quantifies the effects of increased NUE on 1) the national agricultural economy using a simulation model of US agriculture and 2) regional water quality effects using a biogeochemical model for the Arkansas-White-Red river basin. National economic effects are reported for NUE improvement scenarios of 10%, 20%, 50%, and 100%, whereas regional water quality effects are estimated for a 20% NUE improvement scenario in the Arkansas-White-Red river basin. Simulating a 20% increase in NUE in row crops is shown to reduce N requirements by 1.4 million tonnes y−1 and increase farmer net profits by 1.6% ($743 million) per year by 2026 over the baseline simulation for the same period. For each 10% increase in NUE, annual farm revenues for commodity crops increased over the baseline by approximately $350 million per year by 2026. Changes in crop prices and land-use relative to the baseline were less than 2%. This suggests a net benefit even though fertilizer cost savings can result in increased cultivation of land, i.e., ‘Jevon's paradox’. Results from the biogeochemical model of the Arkansas-White-Red river basin suggest that a 20% increase in NUE corresponds to a 5.72% reduction in nitrate loadings to freshwaters, with higher reductions in agricultural watersheds. The value of these reductions was estimated as $43 ha−1, for a total of $15.3 to 136.7 million yr−1 in avoided water treatment costs. After estimating the social value of increased NUE, we conclude with a discussion of potential strategies to increase efficiency and the research needed to achieve this goal. These include perennialization of the agricultural landscape, genetic crop improvement, targeted fertilizer application, and manipulation of the plant-root microbiome.

Strobilurin Effects on Nitrogen Use Efficiency for the Yield and Protein in Durum Wheat Grown Under Rainfed Mediterranean Conditions

In wheat, the increase in nitrogen use efficiency (NUE) and optimization of the nitrogen doses to be used are both very important aspects for improving sustainable and productive agriculture. The aim of this study was to investigate, under rainfed Mediterranean conditions, the influence of strobilurin treatment and N fertilization on durum wheat N use efficiency for yield (NUEy) and protein (NUEp) and on the contribution of their components, nitrogen uptake efficiency (UPE) and nitrogen utilization efficiency (NUtE). Two durum wheat cultivars (Saragolla and Sfinge) were grown for two years in field conditions under five nitrogen treatments (60 kg ha−1 N60; 90 and 120 kg ha−1 given two and three times; N90, N90T3, N120 and N120T3) comparing a control without strobilurin treatment (ST0) and one application of strobilurin (STaz). In Sfinge, STaz caused a decrease in UPE and NUEp and an increase in NUtE and NUEy. In Saragolla, the opposite behavior was observed. Moreover, strobilurin positively affected the contribution of UPE and negatively that of NUtE to NUEy only in Saragolla. Furthermore, strobilurin determined higher NUEy and NUEp values under most of the N treatments adopted in the drier year. With this study, we supported the hypothesis that in Mediterranean conditions, the possibility of reducing N rate application from 120 to 90 kg ha−1 with a strobilurin-based treatment, even in the absence of fungal diseases, could represent a useful agronomic strategy for durum wheat grown under drought conditions as those predicted under the ongoing climate change.

Drip fertigation significantly increased crop yield, water productivity and nitrogen use efficiency with respect to traditional irrigation and fertilization practices: A meta-analysis in China

Improving irrigation and fertilization management for greater productivity is critical to address water scarcity. Drip fertigation can synchronize the water and nitrogen (N) supply with crop demand, offering the potential for enhanced water productivity (WP) and nitrogen use efficiency (NUE). To quantitatively assess the efficacy of drip fertigation and identify the main affecting factors, we used a meta-analysis to evaluate the effects of drip fertigation on the yield, WP and NUE under different conditions and to quantify the irrigation water saving potential (WSP) and N saving potential (NSP) of drip fertigation. Our results showed that, overall, drip fertigation led to significantly higher yields (12.0%), WP (26.4%) and NUE (34.3%), while significantly decreased crop evapotranspiration (ET) by 11.3%, compared to farmers’ practices referring to traditional irrigation by furrow or flood and fertilization by broadcasting N fertilizer (broadcasting N fertilizer without irrigation in rainfed farming). However, the extent of improvement highly depended on crop types and was subject to edaphic, climatic and managerial factors. Among crop types, potato showed the highest increase in yield (40.3%) and WP (100.3%), and fruit showed the highest increase in NUE (68.2%). At a regional scale, drip fertigation performed best in semiarid regions. In addition, irrigation water inputs had large effects (P < 0.05) on the magnitude of yield, ET, and WP response, while N inputs had significant effects (P < 0.05) on yield and NUE but not on WP and ET. The results of WSP and NSP indicated that water input under drip fertigation for maize, wheat, potato, tomato and cotton could be further decreased by 14% (41 mm), 22% (87 mm), 20% (42 mm), 20% (59 mm) and 13% (50 mm), and N input could be further decreased by 23% (68 kg N ha−1), 26% (88 kg N ha−1), 33% (60 kg N ha−1), 21% (117 kg N ha−1) and 23% (66 kg N ha−1), respectively, without crop yield reduction.

Deep Placement of Briquette Urea Increases Agronomic and Economic Efficiency of Maize in Sandy Loam Soil

Imbalanced use of fertilizers along with inappropriate sources and application methods has attributed to reduced nitrogen use efficiency (NUE) and crop productivity. The use of the right N source and appropriate application method is essential to reduce N losses and increase NUE, crop yield, and economic return. A field trial was conducted at the Agricultural Research Station, Dasharathpur, Surkhet following a randomized complete block design with seven treatments (three replications) using various N sources (urea, urea briquette, and three different blended fertilizers) and their application methods to assess their fertilizing efficiencies. Treatments showed a significant effect (p<0.05) for all the traits viz. plant and ear height, stover and grain yield, harvest index, and thousand-grain weight. Compared to the recommended dose of fertilizer (RDF), the grain yield advantage of blended fertilizer (10:26:26 NPK) in a combination of Zinc followed by RDF+Zn and urea deep placement (UDP) applied treatments were 7.8, 2.7, and 2.4% respectively. Among all, deep placement of urea briquette was found to be economic for the cultivation of Khumal Hybrid-2 maize variety while producing similar yield (2.4% higher) with 25% lower nitrogen dose, increasing agronomic nitrogen use efficiency by 10.41 kg/kg N, and economic benefit by US$30.4/ha compared to RDF.

Increase of nitrogen-use efficiency by phosphorus fertilization in grass–legume pastures

Forage legumes intercropped with grasses add nitrogen (N) to the production system and may increase forage yields. However, both phosphate fertilization and the solubility of phosphorus (P) sources may affect this contribution. This study aimed to evaluate the response of Guinea grass (Panicum maximum) intercropped with legumes and fertilized with phosphate fertilizers of different solubility. Guinea grass was grown as a single crop, fertilized or not with mineral N, and intercropped with Java (Macrotyloma axillare), or dwarf pigeon pea (Cajanus cajan); phosphorus was applied as triple superphosphate (P-TSP) or Bayovar (P-Bay), plus a control without phosphorus. The highest forage yield and N accumulation was observed in Guinea grass fertilized with N and P, with 70,364 and 60,036 kg ha−1of dry matter, resulting in 977 and 1004 kg ha−1 of N accumulated by the plants for P-TSP and P-Bay, respectively. The introduction of legumes increased the N accumulation but decreased yield of Guinea grass. The highest nitrogen use efficiency (NUE) was found with P fertilization, i.e., 56% and 54% for P-TSP and P-Bay, respectively. The use of legumes intercropped with Guinea does not improve the effectiveness of the reactive rock phosphate. Therefore, the introduction of legumes intercropping with Guinea grass may be an alternative to N fertilization only when P is not applied to low fertile soils. Broadcast and incorporated P fertilization by the time of Guinea grass sowing, not only increases forage yields but also results in higher NUE regardless of P fertilizer solubility.

Measures to increase the nitrogen use efficiency of European agricultural production

Inputs of nitrogen to agricultural production systems are necessary to produce food, feed and fibre, but nitrogen (N) losses from those systems represent a waste of a resource and a threat to both the environment and human health. The nitrogen use efficiency (NUE) of an agricultural production system can be seen as an indicator of the balance between benefits and costs of primary food, feed and fibre production. Here, we used modelling to follow the fate of the virgin N input to different production systems (ruminant and granivore meat, dairy, arable), and to estimate their NUE at the system scale. We defined two ruminant meat production systems, depending on whether the land places constraints on farming practices. The other production systems were dairy, granivore and arable production on land without constraints. Two geographic regions were considered: Northern and Southern Europe. Measures to improve NUE were identified and allocated to Low, Medium and High ambition groups, with Low equating to the current situation in Europe for production systems that are broadly following good agricultural practice.The NUE of the production systems was similar to or higher in Southern than Northern Europe, with the maximum technical NUEs if all available measures are implemented were for North and South Europe, respectively, 82% and 92% for arable systems, 71% and 80% for granivores, 50% and 36% for ruminant meat production on constrained land, 53% and 55% for dairy production on unconstrained land and 46% and 62% for ruminant meat production on unconstrained land. The values for NUE found here tend to be higher than reported elsewhere, possibly due to the accounting for long-term residual effects of fertiliser and manure in our method. The greatest increase in NUE with the progressive implementation of higher ambition measures was in unconstrained granivore systems and the least was in constrained ruminant meat systems, reflecting the lower initial NUE of granivore systems and the larger number of measures applicable to confined livestock systems.Our work supports use of NUE as an indicator of the temporal trend in the costs and benefits of existing agricultural production systems, but highlights problems associated with its use as a sustainability criteria for livestock production systems.For arable systems, we consider well-founded the NUE value of 90% above which there is a high risk of soil N depletion, provided many measures to increase NUE are employed. For systems employing fewer measures, we suggest a value of 70% would be more appropriate.We conclude that while it is feasible to calculate the NUE of livestock production systems, the additional complexity required reduces its value as an indicator for benchmarking sustainability in practical agriculture.

Increasing nitrogen use efficiency in rice through fertilizer application method under rainfed drought conditions in Nepal

Nitrogen (N) is the most important yield-limiting plant nutrient. Despite various measures available for improvement of N management, nitrogen use efficiency (NUE) is still very low in rice (Oryza sativa L.), particularly under rainfed conditions. A field experiment was conducted at the Regional Agricultural Research Station, Banke, Nepal, during the rainy seasons of 2017 and 2018 to study the effects of nitrogen application method on NUE and grain yields across different varieties. The field experiment was laid out in a split-plot design, consisting of three rice varieties—Arize 6444, Radha-4, and Sukkha Dhan-3—as the main plots and five fertilizer treatments in sub-plots, and replicated thrice. The five fertilizer treatments included control (0 kg N ha−1), broadcast prilled urea at 78 kg N ha−1 and 100 kg N ha−1, and deep placement of prilled urea and briquetted urea at 78 kg N ha−1. Both rice variety and fertilizer treatment had a significant (p < 0.05) effect on grain yield. The hybrid variety (Arize 6444) increased grain yield by 23% compared to Sukkha Dhan-3 (4.9 Mg ha−1). Deep-placed briquetted urea increased grain yield by 21–23% (6.7 Mg ha−1) compared to broadcast and deep-placed prilled urea. A higher grain yield for briquetted urea positively correlated (r = 0.43) with the number of tillers per hill. Deep-placed briquetted urea increased NUE (apparent N recovery, agronomic NUE, partial factor productivity of N, and physiological efficiency by 44%, 40%, 34%, and 3%, respectively), while reducing ammonia volatilization by 57% compared to the current recommended rate of broadcast prilled urea. Our results confirm that deep placement of briquetted urea significantly increases grain yields and NUE of rainfed rice.

Combining Azolla and urease inhibitor to reduce ammonia volatilization and increase nitrogen use efficiency and grain yield of rice

Paddy Azolla is considered as a promising technical approach to reduce ammonia (NH3) volatilization and increase nitrogen use efficiency (NUE). However, it is not effective in highly fertilized paddy fields as the high ammonium N (NH4+-N) concentrations adversely inhibit the growth and N uptake of Azolla. Urease inhibitors could effectively decrease NH4+-N concentrations in surface water and NH3 volatilization. However, a lack of information still exists regarding the combined effects of Azolla and urease inhibitors on NH3 volatilization, NUE, and grain yield (GY) of rice. A two-year field experiment was conducted including five treatments (no urea application (control), urea (N), urea + Azolla (NA), urea + urease inhibitor (NUI), and urea + Azolla + urease inhibitor (NAUI)). Results showed that NA treatment (−25.2%) was not effective in reducing NH3 volatilization compared with NUI treatment (−43.3%). The NAUI treatment substantially reduced NH3 volatilization (−54.6%) more than that by NA and NUI treatments, primarily because of the lower NH4+-N concentrations, pH, and temperature in surface water. Furthermore, NAUI treatments significantly increased the grain yield (GY) and the apparent N recovery efficiency (ANRE) of rice by 9.0–9.7% and 66.0–71.3%, respectively. The significant increase in GY was mainly from the increased panicle number (4.0%), spikelet number per panicle (15.9%), and total biomass (22.9%), which caused by the enhanced total N uptake (35.8%). NAUI treatment also decreased the yield-scaled NH3 volatilization by 61.1–63.6%. Overall, the co-application of Azolla and urease inhibitor in the rice field substantially decreased NH3 volatilization, and increased NUE and rice yield.

Metabolomic Responses of Maize Shoots and Roots Elicited by Combinatorial Seed Treatments With Microbial and Non-microbial Biostimulants.

Microbial and non-microbial plant biostimulants have been successfully used to improve agriculture productivity in a more sustainable manner. Since the mode of action of biostimulants is still largely unknown, the present work aimed at elucidating the morpho-physiological and metabolomic changes occurring in maize (Zea mays L.) leaves and roots following seed treatment with (i) a consortium of two beneficial fungi [arbuscular mycorrhizal fungi (AMF) and Trichoderma koningii TK7] and rhizobacteria, (ii) a protein hydrolyzate-based biostimulant (PH) alone, or (iii) in combination with a consortium of T. koningii TK7 and rhizobacteria. The application of PH alone or in combination with Trichoderma elicited significant increases (+16.6%) in the shoot biomass compared to untreated maize plants, whereas inoculation with AMF + Trichoderma elicited significant increases in root dry biomass (+48.0%) compared to untreated plants. Distinctive metabolomic signatures were achieved from the different treatments, hence suggesting that different molecular processes were involved in the plants response to the biostimulants. The metabolic reprogramming triggered by the treatments including the protein hydrolyzate was hierarchically more pronounced than the application of microorganisms alone. Most of the differential metabolites could be ascribed to the secondary metabolism, with phenylpropanoids and terpenes being the most represented compounds. The application of PH triggered an accumulation of secondary metabolites, whereas the opposite trend of accumulation was seen in the case of microorganisms alone. The increase in biomass could be related to two processes, namely the modulation of the multilayer phytohormone interaction network and a possible increase in nitrogen use efficiency via the GS-GOGAT system.

Integrated use of farm manure and synthetic nitrogen fertilizer improves nitrogen use efficiency, yield and grain quality in wheat

Lower nitrogen use efficiency (NUE) is a major yield limiting factor in semi-arid regions due to poor organic contents of the soils. There is a close relationship between soil organic matter and NUE of fertilizers. Therefore, this study was conducted to assess the effect of sole N fertilizer and its combinations with organic amendments (farm manure combinations) on N use efficiency and crop productivity. For this purpose, a two-year field study was conducted to access the influence of integrated use of synthetic N fertilizer (urea) and farm manure on N use efficiency and wheat productivity. Treatments include i.e. Control, 100% N by Urea + 0%N by farm manure (FM), 75% N by Urea + 25 % N by FM, 50% N by Urea + 50% N by FM, 25% N by Urea + 75% N by FM, 0% N by Urea + 100% N by FM arranged in a triplicate randomized complete block design having recommended N rate of 150 kg ha–1. The results revealed that the treatment having 75% Urea and 25% FM followed by 50% Urea and 50% FM showed better results in term of wheat growth and yield. There was 98% increase in N uptake of wheat grains and 200% increase in NUE by the application of 75% urea+25% FM relative to sole application of urea. This study suggests use of 3:1 ratio of urea and FM for maximum NUE and sustainable wheat production.