Nitrogen Use Efficiency In Rice Research Articles

Combination of Polymer-Coated Urea and Rapid-Release Urea Increases Grain Yield and Nitrogen Use Efficiency of Rice by Improving Root and Shoot Activities

The use of polymer-coated urea (PCU) can improve nitrogen use efficiency (NUE), compared to the application of rapid-release urea (RU). However, the effect of PCU-based nitrogen management on grain yield and the NUE of rice and its underlying mechanism remain unclear. A japonica rice cultivar Jinxiangyu 1 was grown in the field with four treatments including N omission (0N), split application of RU (Control), one-time application of 100% PCU (T1), and one-time application of 70% PCU + 30% RU (T2). Results showed that, compared to the control, the grain yield was significantly increased in the T2 treatment, while it was comparable in the T1 treatment. This was mainly due to increased total spikelets in the T2 treatment. Root oxidation activity (ROA) and root zeatin (Z) + zeatin riboside (ZR) content during booting were the distinct advantages of the T2 treatment, compared to either the control or T1 treatment, exhibiting significant or highly significant correlations with leaf photosynthesis. This process contributed significantly to total spikelets and total N uptake. Additionally, the T2 treatment absorbed more N than the control without reducing the internal N use efficiency (IEN), primarily due to its unchanged harvest index (HI) driven by comparable non-structural carbohydrate remobilization. In conclusion, combining PCU with RU can enhance the coordination of root and shoot traits during booting while maintaining a competitive HI at maturity, thereby significantly improving grain yield and achieving a balance in N uptake and utilization.

Rational Utilization of Sediment Resources Improves Rice Yield and Nitrogen Use Efficiency under Salt Stress

Soil salinization negatively affects rice growth and yield; however, how different sludge sources regulate rice growth and yield under salt stress was rarely investigated. This study evaluated the performance of two salt-tolerant rice cultivars, Chaoyou 1000 and Longliangyou 506, grown in two sediment sources, pond sediment (PS) and river sludge (RS), under salt stress (56 ds m−1 brine irrigation) with conventional soil (CS) used as the control. The results showed that the rice yield under the PS and RS treatments was enhanced by 51.0% and 43.6% as compared with CS, respectively, owing to an improvement in spikelet per panicle, 1000-grain weight, dry matter accumulation, and the chlorophyll content in both rice cultivars. Compared with CS, the total nitrogen accumulation, nitrogen grain production efficiency, nitrogen harvest index, and nitrogen partial productivity under the PS and RS treatments were increased by 18.9–28.9%, 17.0–20.6%, 7.2–16.6%, and 43.8–50.9%, respectively. Moreover, rice grown in PS and RS showed higher activities of nitrogen metabolism-related enzymes (nitrate reductase, glutamine synthetase, and glutamate synthetase) at the heading stage and higher K+ and K+/Na+ contents in the leaves. Overall, a balanced utilization of sediment resources (especially pond sediment) can effectively alleviate salt stress and improve the yield and nitrogen use efficiency in rice.

Productivity and nitrogen use efficiency of rice under conventional and organic nutrition

The current study demonstrates the influence of conventional and organic nutrient management practices on nitrogen use efficiency, growth, yield, and physiological and biochemical parameters in four rice varieties, namely, Jaiva, Ezhome 2, Jyothi and Uma. Growth parameters, grain yield per hill, and physiological and biochemical parameters were higher under conventional management for all rice varieties. Although the nitrogen use efficiency of each variety varied significantly with nutrient management practices, the variation was least in Jaiva (23.8%), which is the organic rice variety released by Kerala Agricultural University. The rice varieties Jaiva and Ezhome 2 showed consistency in the grain weight per panicle under both conventional (Jaiva- 4.57 g, Ezhome 2- 5.86 g) and organic (Jaiva, 4.24 g, Ezhome 2, 4.54 g) management. The soil nitrogen content at the tillering stage (0.66**) showed a significantly higher positive correlation with nitrogen use efficiency under organic management. The results of the study provide a better understanding of factors that can lead to a sustained yield in organic rice production in terms of nitrogen use efficiency.

Effect of Nitrogen Fertilizers Applied through Nano Clay Polymer Composites on Nitrogen Use Efficiency of Rice

Nitrogen (N) is an essential nutrient for crop growth. However, excessive nitrogen fertilizer application leads to environmental losses. In this study, an attempt was made to reduce the nitrogen losses by loading of urea and urea ammonium nitrate (UAN) into Nano clay polymer composites (NCPCs) to act as slow release N fertilizers. To achieve the objectives of the present study, five N fertilizer treatments (T1-control, T2- N applied through urea, T3- N applied through UAN, T4- N applied through NCPC loaded with urea and T5- N applied through NCPC loaded with UAN) were assessed using three rice genotypes namely IR-64, Nagina 22 and MTU 1010. Results of the greenhouse study indicated that the UAN loaded NCPC treatment was more effective in terms of increasing the grain yield, nitrogen uptake, agronomic use efficiency and apparent nitrogen recovery by 36.9%, 51.0%, 64.2%, and 92.0% over urea, respectively. Amongst the genotypes, MTU 1010 was recorded with highest gran yield followed by IR-64 and Nagina-22.

Balanced nitrogen–iron sufficiency boosts grain yield and nitrogen use efficiency by promoting tillering

Crop yield plays a critical role in global food security. For optimal plant growth and maximal crop yields, nutrients must be balanced. However, the potential significance of balanced nitrogen–iron (N–Fe) for improving crop yield and nitrogen use efficiency (NUE) has not previously been addressed. Here, we show that balanced N–Fe sufficiency significantly increases tiller number and boosts yield and NUE in rice and wheat. NIN-like protein 4 (OsNLP4) plays a pivotal role in maintaining the N–Fe balance by coordinately regulating the expression of multiple genes involved in N and Fe metabolism and signaling. OsNLP4 also suppresses OsD3 expression and strigolactone (SL) signaling, thereby promoting tillering. Balanced N–Fe sufficiency promotes the nuclear localization of OsNLP4 by reducing H2O2 levels, reinforcing the functions of OsNLP4. Interestingly, we found that OsNLP4 upregulates the expression of a set of H2O2-scavenging genes to promote its own accumulation in the nucleus. Furthermore, we demonstrated that foliar spraying of balanced N–Fe fertilizer at the tillering stage can effectively increase tiller number, yield, and NUE of both rice and wheat in the field. Collectively, these findings reveal the previously unrecognized effects of N–Fe balance on grain yield and NUE as well as the molecular mechanism by which the OsNLP4–OsD3 module integrates N–Fe nutrient signals to downregulate SL signaling and thereby promote rice tillering. Our study sheds light on how N–Fe nutrient signals modulate rice tillering and provide potential innovative approaches that improve crop yield with reduced N fertilizer input for benefitting sustainable agriculture worldwide.

CRISPR/Cas9-mediated elimination of OsHHO3, a transcriptional repressor of three AMMONIUM TRANSPORTER1 genes, improves nitrogen use efficiency in rice.

CRISPR/Cas9-mediated elimination of OsHHO3, a transcriptional repressor of three AMMONIUM TRANSPORTER1 genes, improves nitrogen use efficiency in rice.

Identification of quantitative trait loci controlling nitrogen use efficiency-related traits in rice at the seedling stage under salt condition by genome-wide association study.

Rice cultivation is facing both salt intrusion and overuse of nitrogen fertilizers. Hence, breeding new varieties aiming to improve nitrogen use efficiency (NUE), especially under salt conditions, is indispensable. We selected 2,391 rice accessions from the 3K Rice Genomes Project to evaluate the dry weight under two N concentrations [2.86 mM - standard N (SN), and 0.36 mM - low N (LN)] crossed with two NaCl concentrations [0 (0Na) and 60 mM (60Na)] at the seedling stage. Genome-wide association studies for shoot, root, and plant dry weight (DW) were carried out. A total of 55 QTLs - 32, 16, and 7 in the whole, indica, and japonica panel - associated with one of the tested traits were identified. Among these, 27 QTLs co-localized with previously identified QTLs for DW-related traits while the other 28 were newly detected; 24, 8, 11, and 4 QTLs were detected in SN-0Na, LN-0Na, SN-60Na, and LN-60Na, respectively, and the remaining 8 QTLs were for the relative plant DW between treatments. Three of the 11 QTLs in SN-60Na were close to the regions containing three QTLs detected in SN-0Na. Eleven candidate genes for eight important QTLs were identified. Only one of them was detected in both SN-0Na and SN-60Na, while 5, 0, 3, and 2 candidate genes were identified only once under SN-0Na, LN-0Na, SN-60Na, and LN-60Na, respectively. The identified QTLs and genes provide useful materials and genetic information for future functional characterization and genetic improvement of NUE in rice, especially under salt conditions.

Genome-wide association study using specific-locus amplified fragment sequencing identifies new genes influencing nitrogen use efficiency in rice landraces.

Nitrogen is essential for crop production. It is a critical macronutrient for plant growth and development. However, excessive application of nitrogen fertilizer is not only a waste of resources but also pollutes the environment. An effective approach to solving this problem is to breed rice varieties with high nitrogen use efficiency (NUE). In this study, we performed a genome-wide association study (GWAS) on 419 rice landraces using 208,993 single nucleotide polymorphisms (SNPs). With the mixed linear model (MLM) in the Tassel software, we identified 834 SNPs associated with root surface area (RSA), root length (RL), root branch number (RBN), root number (RN), plant dry weight (PDW), plant height (PH), root volume (RL), plant fresh weight (PFW), root fractal dimension (RFD), number of root nodes (NRN), and average root diameter (ARD), with a significant level of p < 2.39×10-7. In addition, we found 49 SNPs that were correlated with RL, RBN, RN, PDW, PH, PFW, RFD, and NRN using genome-wide efficient mixed-model association (GEMMA), with a significant level of p < 1×10-6. Additionally, the final results for eight traits associated with 193 significant SNPs by using multi-locus random-SNP-effect mixed linear model (mrMLM) model and 272 significant SNPs associated with 11 traits by using IIIVmrMLM. Within the linkage intervals of significantly associated SNP, we identified eight known related genes to NUE in rice, namely, OsAMT2;3, OsGS1, OsNR2, OsNPF7.4, OsPTR9, OsNRT1.1B, OsNRT2.3, and OsNRT2.2. According to the linkage disequilibrium (LD) decay value of this population, there were 75 candidate genes within the 150-kb regions upstream and downstream of the most significantly associated SNP (Chr5_29804690, Chr5_29956584, and Chr10_17540654). These candidate genes included 22 transposon genes, 25 expressed genes, and 28 putative functional genes. The expression levels of these candidate genes were measured by real-time quantitative PCR (RT-qPCR), and the expression levels of LOC_Os05g51700 and LOC_Os05g51710 in C347 were significantly lower than that in C117; the expression levels of LOC_Os05g51740, LOC_Os05g51780, LOC_Os05g51960, LOC_Os05g51970, and LOC_Os10g33210 were significantly higher in C347 than C117. Among them, LOC_Os10g33210 encodes a peptide transporter, and LOC_Os05g51690 encodes a CCT domain protein and responds to NUE in rice. This study identified new loci related to NUE in rice, providing new genetic resources for the molecular breeding of rice landraces with high NUE.

Global patterns and controls of yield and nitrogen use efficiency in rice

Factors influencing rice (Oryza sativa L.) yield mainly include nitrogen (N) fertilizer, climate and soil properties. However, a comprehensive analysis of the role of climatic factors and soil physical and chemical properties and their interactions in controlling global yield and nitrogen use efficiency (e.g., agronomic efficiency of N (AEN)) of rice is still pending. In this article, we pooled 2293 observations from 363 articles and conducted a global systematic analysis. We found that the global mean yield and AEN were 6791 ± 48.6 kg ha−1 season−1 and 15.6 ± 0.29 kg kg−1, respectively. Rice yield was positively correlated with latitude, N application rate, soil total and available N, and soil organic carbon, but was negatively correlated with mean annual temperature (MAT) and soil bulk density. The response of yield to soil pH followed the parabolic model, with the peak occurring at pH = 6.35. Our analysis indicated that N application rate, soil total N, and MAT were the main factors driving rice yield globally, while precipitation promoted rice yield by enhancing soil total N. N application rate was the most important inhibitor of AEN globally, while soil cation exchange capacity (CEC) was the most important stimulator of AEN. MAT increased AEN through enhancing soil CEC, but precipitation decreased it by decreasing soil CEC. The yield varies with climatic zones, being greater in temperate and continental regions with low MAT than in tropical regions, but the opposite was observed for AEN. The driving factors of yield and AEN were climatic zone specific. Our findings emphasize that soil properties may interact with future changes in temperature to affect rice production. To achieve high AEN in rice fields, the central influence of CEC on AEN should be considered.

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.

Genotypic Variation in Photosynthetic Traits, Grain Yield and Nitrogen Use Efficiency in Rice (Oryza sativa L.) Under Differential Nitrogen Levels

Nitrogen (N) is one of the yield limiting nutrients for rice. Unwarranted usage of N fertilizer to achieve higher crop returns is affecting environment and increasing the cost of cultivation. A field experiment was conducted under two differential N experimental plots (N-Low and N-Rec) to evaluate the effect of N on photosynthesis, grain yield and nitrogen use efficiency (NUE) of six rice genotypes belonging to three diverse groups. At N-Rec, Kolajoha3 exhibited highest mean SCMR value (43.2), flag leaf length (39.0 cm), flag leaf width (1.77 cm), flag leaf area (53.8 cm2 ), photosynthetic rate (19.50 µmol CO2 m-2 s-1),stomatal conductance (0.38 mol [H2 O] m-2 s-1),transpiration rate (10.72 mmol [H2 O] m-2 s-1). IC463254 recorded highest mean grain yield (621.5 g m-2), total dry matter (1302.5 g m-2), harvest index (47.7%), grain N uptake (84.4 kg ha-1) and nitrogen use efficiency (18.2). Significant reduction in growth, photosynthetic rate and yield of rice occurred under N-Low compared with N-Rec. In comparison N-Rec, Kolajoha3 exhibited least mean reduction in plant height (10.68%), photosynthetic rate (14.96%), productive tiller number (35.40%), grain yield (50.63%), straw yield (24.83%), total dry matter (36.03%), agronomic efficiency (14.6%) and NUE (26.21%) under N-Low, while IC463254 exhibited least mean reduction in SCMR value (14.11%) and flag leaf width (23.66%).

PH-responsive/sustained release nitrogen fertilizer hydrogel improves yield, nitrogen metabolism, and nitrogen use efficiency of rice under alternative wetting and moderate drying irrigation

Rice is challenged by inefficient nitrogen (N) fertilizer and water inputs. However, pH-responsive N fertilizers (pH-RNFs) could improve rice yield and N use-efficiency under water-saving irrigation. Thus, a pot experiment was conducted without N fertilizer (0 mg N/kg, ZNF), with 175 mg/kg mineral N fertilizer (MNF), and with 175 mg/kg pH-responsive N fertilizer (pH-RNF) by using three water regimes: alternate wetting/critical drying (AWCD, 70–60% saturation, 5 cm flooded), alternate wetting/severe drying (AWSD, 80–70% saturation, 5 cm flooded), and alternate wetting/minor drying (AWMD, 100–90% saturation, 5 cm flooded). Under the same alternate wetting/drying regime, the growth traits, yield, and N utilization of rice were found to be higher in pH-RNF than in MNF. The growth attributes and yield and the N efficient use of rice were greater in the AWMD regime than in the AWCD regime under the same N fertilization. The surface area, diameter, length density, oxidation ability, reductase activity, and peroxidase activity of roots were greater in AWMD × pH-RNF than in AWCD × ZNF, because the former treatment increased the total N contents in the rhizosphere, whereas the latter reduced them. In the photosynthesis process, leaf nitrate reductase (41.7 µg/[g.h]) and leaf glutamine synthetase (1158.1 µmol/[g.h]) were larger in AWMD × pH-RNF than in AWCD × ZNF at 22.7 µg/(g.h) and 501.2 µmol/(g.h), respectively, resulting in the amelioration of oxidative leaf cell damage, as revealed by reduced radical oxidative sequence release and lower malonaldehyde level (7.2 µmol/g). Meanwhile, the optimum N nutrition enhanced the leaf mesophyll structure, cell cycle progression, and the development traits of the stem and panicle under the combination AWMD × pH-RNF. Panicle glutamine synthetase (24.35 µmol/[g.h]) and catalase activity (13.86 µg/min) were larger in AWMD × pH-RNF than in AWCD × ZNF at 14.77 µmol/[g.h] and 7.59 µg/min, respectively. The combination AWMD × pH-RNF resulted in the highest N crop removal efficiency (CREN, 49.5%), N agronomic use efficiency (AUEN, 7.97 g/g), N partial factor productivity (PFPN, 18.66 g/g), and N harvest index (HIN, 67.83%). However, the minimum values of CREN (10.3%), AUEN (1.49 g/g), PFPN (7.59 g/g), and HIN (43.48%) were observed in AWCD × MNF. This study suggests that AWMD × pH-RNF could promote root and shoot morpho-physio-biochemical traits, guaranteeing optimal overall plant growth with high yield and adequate N acquisition, and efficient N utilization for sustainable rice production.

Nitrogen use efficiency of rice in India: A regional analysis

ABSTRACT The crop nitrogen (N) use efficiency has been recognized as a useful indicator to measure the overall progress of the country towards achieving the sustainable development goal. Moreover, national level N use efficiency indicators are essential for improved estimate of global N budget and environmental impact assessment. We made an attempt to calculate the indicators of N use efficiency for rice at national and regional level in India. We utilized the data from research papers (23 no) published in reputed scientific journals and theses (83 no) submitted to different state agricultural universities over a period of 46 years (between 1972 and 2018). The partial factor productivity of N for rice in India ranged from 39.8 to 68.0 kg kg−1 with a national average value of 52.8 kg kg−1. The national average agronomic N use efficiency and nitrogen recovery efficiency (REN) were 18 kg kg−1 and 42.6%, respectively. Conducive agro-climatic condition coupled with improved crop management resulted in higher REN (>50%) in northern zone states of India. Whereas, rain-fed eastern and central zone states have REN<40%. The partial N balance (PNB) in rice ranged from 0.72–1.42 in India. The states with lower PNB need to reconcile their N addition with crop N uptake by adopting N responsive varieties and advanced fertilizer management to prevent environment degradation and economic loss. The findings of this study have significant implications for N budget estimation and policy decisions on hunger, food security and environment at national and global level.

Soil nitrogen dynamics drive regional variation in nitrogen use efficiency in rice: A multi‐scale study

AbstractNortheast and East China account for ~36% of the Chinese rice cultivation area, yet considerable spatial disparities in nitrogen use efficiency (NUE) exist between these regions. The underlying causes remain poorly understood. Herein, we conducted a case study in two sample sites from two regions, Wuchang and Changshu, using multi‐scale evidence chains spanning macro‐ and micro‐ processes to identify the determinants of spatial NUE variability. Field studies showed higher NUE (partial factor productivity, PFP, and agronomic efficiency, AE) but lower ammonia volatilisation in Wuchang paddy soil. By separating edaphic factors from climatic conditions, soil replacement pot studies between Wuchang and Changshu revealed that both apparent (AE and recovery efficiency, RE) and 15N‐traced NUE were higher, whereas 15N fertilizer losses were lower in Wuchang‐soil than Changshu‐soil irrespective of site, suggesting soil type contributed to differences in soil N retention capacity and NUE of the soils. Process‐scale results showed that greater rates of gross N mineralizsation (13‐fold higher), gross nitrification (93% higher), and denitrification (52% higher) in Changshu‐soil compared to Wuchang‐soil corresponded to functional gene relative abundance, signifying larger reactive N losses and reduced soil N retention capacity. Microbial community analysis suggested that the differential N transformations were caused by differences in ammonia‐oxidizing archaea (AOA) family nitrososphaeraceae and Nitrospira‐like nitrite‐oxidizing bacteria (NOB). This highlights the importance of specific efficiency‐enhanced strategies tailored to the edaphic characteristics of cropping regions, such as increasing soil N retention capacity using enhanced‐efficiency fertilizer in East China, while implementing conservation management strategies in Northeast China.Highlights Field‐scale studies revealed higher NUE and lower NH3 volatilisation in Wuchang site. Soil replacement pot studies showed higher NUE in Wuchang‐soil regardless of sites. Process‐scale results unravelled high N losses and low soil N retention in Changshu‐soil. Varying NUE partially correlated with Nitrososphaeraceae AOA and Nitrospira‐like NOB.

Determining optimal nitrogen management to improve rice yield, quality and nitrogen use efficiency based on multi-index decision analysis method.

Reasonable nitrogen (N) supply is critical for increasing rice yield while improving grain quality and nitrogen use efficiency (NUE). However, the trade-off relationship between yield, quality and NUE of rice under N management has not been well understood enough. In the present study, a 2-year field experiment was conducted to identify optimal N fertilizer management practices that resulted in high-yield, high-quality and high-NUE by using the technique for order preference by similarity to an ideal solution (TOPSIS) with entropy weight (EW) method. All the parameters of rice yield, quality and efficiency were remarkably affected by fertilization treatments. Compared with farmer's fertilization practice (FFP), optimizing N fertilizer treatment (OPT) and substituting 20% of N fertilizer with pig manure based on OPT treatment (OPTM) increased grain yield (2.87-6.62%) by maintaining higher 1000-grain weight and filled grains rate. The agronomic NUE (AE) and N partial factor productivity (PFP) under OPT and OPTM treatment were also remarkably increased by 32.81-43.01% and 28.59-33.28% with respect to the value under FFP treatment, respectively. Meanwhile, OPT and OPTM significantly improved the milling quality of rice by increasing brown rice rate (0.71-1.17%) and head rice rate (1.34-2.31%). OPT and OPTM significantly improved appearance quality by decreasing chalkiness and eating quality by reducing amylose content in 2020. The TOPSIS with EW showed that rice comprehensive evaluation could be maintained at a high level under OPT and OPTM. OPT and OPTM were nutrient management modes of high-yield, high-quality and high-efficiency, and promising practice to improve rice comprehensive productivity. This strategy is also highly-consistent with the United Nations Sustainable Development Goals. © 2023 Society of Chemical Industry.

Understanding the physiological, genetic and molecular basis of nitrogen deficiency tolerance and their application in rice improvement

Nitrogen (N) is a major nutrient required for growth and yield of rice plants. Several factors including plant, edapic and climate conditions influence the criticle yield response curve of the plants. Apart from breeding for N responsive rice varieties, excessive use of nitrogenous fertilizers have become a general farmers practice to boost rice productivity under intensive cropping system. Now, it is imperative to orient the crop improvement programme for sustainable crop production strategy as well as to achieve the evergreen revolution through improving nitrogen use efficiency (NUE) under global climate change condition. To develop N-efficient rice varieties under crop breeding programs, it is crucial to comprehend the physiological, genetic and molecular features associated with tolerance to nitrogen deprivation. It has always been challenging for a rice breeders to develop rice varieties with high nitrogen use efficiency (NUE), as it is highly complex physiological trait involving several component traits and its dynamic interaction with environemental factor. NUE is a polygenic traits controlled by number of quantitative trait loci's at genomic level. Till date, researchers targeted component traits for increasing NUE such as, nitrogen uptake/absorption, transport from root to shoot, assimilation, utilisation, remobilisation, reasssssmilation and partitioning /redistribution. Here, we described a short summary of the physiological, genetic and molecular underpinnings of nitrogen deficit tolerance and how these prior art information can be used for improving NUE in rice. Insight from our discussions may facilitate the breeders to improve the NUE of rice plants in future.

Rice‐Animal Co‐Culture Systems Benefit Global Sustainable Intensification

AbstractProducing more food with less pollution and greenhouse gas emissions is a grand challenge for the 21st century. Strategies to successfully promote win‐win outcomes for both food security and environmental health are not easy to identify. Here we comprehensively assess an ecological rice‐animal co‐culture system (RAC) (e.g., rice‐fish, rice‐duck, and rice‐crayfish) through a global meta‐analysis and identify the potential benefits of global promotion. Compared to traditional monoculture of rice or animal production, the RAC can not only reduce the demand for agricultural land areas, but also increase rice yields (+4%) as well as nitrogen use efficiency of rice (+6%). At the same time, RAC reduces nitrogen losses (−16% runoff and −13% leaching) and methane emissions (−11%), except for rice‐fish coculture systems, which are likely to increase methane emissions (+29%). Furthermore, RAC increases the net income of farmers through reducing cost of fertilizer and pesticide input and achieving higher outputs with more marketable products. According to the development stage of different countries, promotion of RAC will thus realize multiple benefits and aid sustainable intensification.

Promising physiological traits associated with nitrogen use efficiency in rice under reduced N application.

Higher grain yield in high-yielding rice varieties is mostly driven by nitrogen (N) fertilizer applied in abundant amounts leading to increased production cost and environmental pollution. This has fueled the studies on nitrogen use efficiency (NUE) to decrease the N fertilizer application in rice to the possible extent. NUE is a complex physiological trait controlled by multiple genes, but yet to be completely deciphered in rice. With an objective of identifying the promising physiological traits associated with NUE in rice, the performance of 14 rice genotypes was assessed at N0, N50, N100, and N150 for four (two wet and two dry) seasons using agro-morphological, grain yield, flag leaf traits, photosynthetic pigment content, flag leaf gas exchange traits, and chlorophyll fluorescence traits. Furthermore, the data were used to derive various NUE indices to identify the most appropriate indices useful to screen rice genotypes at N50. Results indicate that with the increase in N application, cumulative grain yield increased significantly up to N100 (5.02t ha-1); however, the increment in grain yield was marginal at N150 (5.09t ha-1). The mean reduction of grain yield was only 26.66% at N50 ranging from 15.0% to 34.2%. The significant finding of the study is the identification of flag leaf chlorophyll fluorescence traits (Fv/Fm, ΦPSII, ETR, and qP) and Ci associated with grain yield under N50, which can be used to screen N use efficient genotypes in rice under reduced N application. Out of nine NUE indices assessed, NUpE, NUtE, and NUEyield were able to delineate the high-yielding genotypes at N50 and were useful to screen rice under reduced N conditions. Birupa emerged as one of the high yielders under N50, even though it is a moderate yielder at N100 and infers the possibility of cultivating some of the released rice varieties under reduced N inputs. The study indicates the possibility of the existence of promising genetic variability for grain yield under reduced N, the potential of flag leaf chlorophyll fluorescence, and gas exchange traits as physiological markers and best suitable NUE indices to be deployed in rice breeding programs.

Effects of coated and briquette urea on yield and nitrogen use efficiency of rice at Rampur, Chitwan, Nepal

Nitrogen is one of the most limiting element for the growth and yield of rice. However, the imbalance use of conventional urea leads to loss of nitrogen from rice field, decrease nitrogen use efficiency, increase environmental pollution and cost of cultivation. This study was done to evaluate the response of polymer coated urea (PCU) and urea briquette (UB) on the yield and nitrogen use efficiencies (NUE) of rice on a sandy loam soil. The experiment was conducted at the agronomy research farm of Agriculture and Forestry University during the rainy season of 2018 in a randomized complete block design with three replications for each treatment (T1 - control, 0 kg N ha-1; T2- Prilled urea, 150 kg N ha-1 single application at basal; T3- Prilled urea, 150 kg N ha-1 standard split application; T4-PCU, 150 kg N ha-1 single application at basal; T5-UB, 150 kg N ha-1 single application at basal). The data on yield, and NUE were recorded and analyzed by using R studio. The physical and economic maximum dose of Nitrogen for these different types of urea were also calculated. Compared with single application of Prilled urea (3698 kg ha-1), rice fertilized with Prilled urea with standard split application (4747 kg ha-1), single application of PCU (5183 kg ha-1) and BU (4787 kg ha-1) had significantly higher grain yield and NUE. Economic maximum dose of nitrogen was reduced greatly for the single application of PCU (124 kg N ha-1) compared to Prilled urea with standard split application (167 kg N ha-1). Single application of PCU and UB can be considered as an alternative nitrogen fertilizer for rice even in the sandy loam soil.

Precise delivery of nitrogen at tillering stage enhances grain yield and nitrogen use efficiency in double rice cropping systems of South China

Nitrogen fertilizer management substantially affects the growth, productivity, and nitrogen use efficiency (NUE) of rice production systems. To assess the effects of precise application of nitrogen fertilizer at tillering stage as ‘tillering-fertilizer’ on grain yield and nitrogen use efficiency, field trials were conducted in the late season of 2019 and 2020, in addition to a radioisotope 15 N tracer experiment. The experiment was comprised of four N fertilizer treatments i.e., no fertilizer application as a control (T1), traditional surface broadcast fertilization (90 kg N/ha as basal fertilizer and 60 kg N/ha as tillering fertilizer, T2), deep placement of tillering fertilizer (surface broadcast at 90 kg N/ha as basal fertilizer and 45 kg N/ha as tillering fertilizer at 10 cm depth, T3), deep placement of tillering fertilizer (surface broadcast at 90 kg N/ha as basal fertilizer and 30 kg N/ha as tillering fertilizer at 10 cm depth, T4) and two rice cultivars i.e., Wufengyou 615 and Yuxiangyouzhan . Results showed that grain yield remained 18.8% and 12.4% higher owing to increase in productive panicles and grain filling, 42.2% and 38.9% higher nitrogen agronomic efficiency, 4.6% and 10.4% higher nitrogen recovery efficiency, and 10.2% and 7.8% higher nitrogen physiological efficiency in T3 than T2 for Wufengyou 615 and Yuxiangyouzhan , respectively. Moreover, nitrogen derived from fertilizer in T3 was increased by 8.0% and 4.4% compared to T2 for Wufengyou 615 and Yuxiangyouzhan , respectively whereas the residual rate of T3 was increased by 31.5%. In addition, the T3 treatment substantially enhanced the leaf area index and leaf chlorophyll content that led to improved photosynthesis and the activities of enzymes related to nitrogen metabolism. Overall, 45 kg N/ha as tillering fertilizer at 10 cm depth and surface broadcast at 90 kg N/ha as basal fertilizer can improve grain yield as well as nitrogen use efficiency in late season rice production system of South China. • Precise delivery of nitrogen (PDN) at tillering stage (TS) can enhance grain yield in rice. • PDN at TS can improve nitrogen use efficiency in rice. • PDN at TS can increase nitrogen residual rate in the soil and decrease nitrogen unaccounted rate.