Agronomic Nitrogen Use Efficiency Research Articles

Integrated assessment of yield, nitrogen use efficiency and ecosystem economic benefits of use of controlled-release and common urea in ratoon rice production

Controlled-release urea (CRU) is commonly used to improve the crop yield and nitrogen use efficiency (NUE). However, few studies have investigated the effects of CRU in the ratoon rice system. Ratoon rice is the practice of obtaining a second harvest from tillers originating from the stubble of the previously harvested main crop. In this study, a 2-year field experiment using a randomized complete block design was conducted to determine the effects of CRU on the yield, NUE, and economic benefits of ratoon rice, including the main crop, to provide a theoretical basis for fertilization of ratoon rice. The experiment included four treatments: (i) no N fertilizer (CK); (ii) traditional practice with 5 applications of urea applied at different crop growth stages by surface broadcasting (FFP); (iii) one-time basal application of CRU (BF1); and (iv) one-time basal application of CRU combined with common urea (BF2). The BF1 and BF2 treatments significantly increased the main crop yield by 17.47 and 15.99% in 2019, and by 17.91 and 16.44% in 2020, respectively, compared with FFP treatment. The BF2 treatment achieved similar yield of the ratoon crop to the FFP treatment, whereas the BF1 treatment significantly increased the yield of the ratoon crop by 14.81% in 2019 and 12.21% in 2020 compared with the FFP treatment. The BF1 and BF2 treatments significantly improved the 2-year apparent N recovery efficiency, agronomic NUE, and partial factor productivity of applied N by 11.47–16.66, 27.31–44.49, and 9.23–15.60%, respectively, compared with FFP treatment. The BF1 and BF2 treatments reduced the chalky rice rate and chalkiness of main and ratoon crops relative to the FFP treatment. Furthermore, emergy analysis showed that the production efficiency of the BF treatments was higher than that of the FFP treatment. The BF treatments reduced labor input due to reduced fertilization times and improved the economic benefits of ratoon rice. Compared with the FFP treatment, the BF1 and BF2 treatments increased the net income by 14.21–16.87 and 23.76–25.96%, respectively. Overall, the one-time blending use of CRU and common urea should be encouraged to achieve high yield, high nitrogen use efficiency, and good quality of ratoon rice, which has low labor input and low apparent N loss.

Synergism of sulfur availability and agronomic nitrogen use efficiency

AbstractNutrient management strategies that exploit nutrient elements’ synergistic interaction to enhance nitrogen use efficiency (NUE) are needed for economic and environmental reasons. A field study was carried out during the 2020–2022 growing seasons at six locations in three countries: two each in the United States, Ghana, and Mali using three sulfur (S) sources with different bioavailability levels (micronized elemental S, untreated elemental S, and ammonium sulfate); applied at five S application rates: site‐specific recommended S rate (SR), 25%, 50%, 75%, and 125% of SR; and a single nitrogen (N) application rate (site‐specific recommended N rate) to comprehensively investigate the influence of S availability on NUE. Specific objectives were to evaluate the impact of S availability on corn (Zea mays L.) yield, N uptake, and NUE. Regardless of the S source and experimental site, the aboveground S and N uptake were strongly and positively correlated (r > 0.88). Increases in apparent N recovery efficiency and agronomic NUE occurred with corresponding increases in S application rate, irrespective of the site and S source. The combined data showed that the agronomic efficiency of applied N fertilizer sources could be enhanced significantly by increasing S availability in soils. With the rising N fertilizer costs in recent times, N losses from the applied fertilizer are a drain on farmers’ income and of environmental concern. Thus, increasing NUE is a needed strategy to safeguard against excessive N application, increase farm profits, and minimize N losses to the environment that could disrupt the ecosystem function.

Improving grain quality and nitrogen use efficiency of cereal-based cropping systems on vertisols in semi-arid tropics

ContextSemi-arid tropics is facing serious issues of malnutrition in population owing to poor quality of food grain production. Malnutrition is directly linked to lower grain protein and zinc yield due to inappropriate land and water, and nutrient management practices, which also resulted into reduced nitrogen use efficiency (NUE) in cereals. ObjectiveThe objectives of the study were to evaluate the effect of land and water and nutrient management on grain protein and zinc yield, and NUE of cereal-based cropping systems on vertisols soils in semi-arid tropics. MethodsThe study was carried out at Hyderabad in India during 2014–15 and 2015–16 and involved three cropping systems (two rotation systems: sorghum-chickpea and maize-groundnut; and one intercropping: pearl millet + pigeonpea), two land and water management i.e. flatbed and broad bed furrows and four nutrient management-N1: Control (no fertilizer), N2: 100% recommended application of macronutrient (nitrogen, phosphorus and potassium) through chemical fertilizer, N3: N2 + 100% recommended application of secondary nutrient (sulphur) and micronutrient (zinc and boron) through chemical fertilizer, and N4 (integrated nutrient): 50% of N2 + 50% nitrogen in cereals or phosphorus in legumes through organic fertilizer as vermicompost. ResultsIn sorghum-chickpea rotation system, the treatment interaction broad bed furrows with 100% recommended application of macronutrient, secondary nutrient and micronutrient recorded significantly higher grain zinc yield in both the years, while grain protein yield was significantly higher in second year. The grain protein and zinc yield in sorghum-chickpea rotation system, and agronomic nitrogen use efficiency in pearl millet+pigeonpea intercropping system was significantly higher in broad bed furrows than flatbed. The agronomic NUE of broad bed furrows was higher by 61% in 2014–15 and 65% in 2015–16 over flatbed. Among the nutrient management treatments, grain protein and zinc yield, and agronomic NUE were significantly higher in combined application of macronutrient, secondary nutrient, and micronutrients through chemical fertilizer i.e. N3 followed by N4, N2 and N1. ConclusionThe broad bed furrows and application of macronutrient, secondary nutrient and micronutrient could be an effective integrated land and water and nutrient management approach to improve grain quality and agronomic nitrogen use efficiency of cereal-based cropping systems in semi-arid tropics. ImplicationsThis study contributed to develop integrated land and water and nutrient management as an innovative agronomic management practice for cereal-based cropping systems, which needs to scale-up through Government agricultural policies to overcome the issue of malnutrition in population living in semi-arid tropics.

Selection and evaluation of gene-edited knockout mutants of AtAAP2 and AtCRF4 homologs of rice for agronomic nitrogen use efficiency (ANUE)

Nitrogen (N) is essential for amino acid synthesis in rice production, but its excessive use poses an environmental concern. This research aimed to improve rice agronomic nitrogen use efficiency (ANUE) by knockout (KO) of rice homologs of the two selected genes from Arabidopsis thaliana: AtAAP2, an amino acid permease involved in N transportation in shoots, and AtCRF4, a transcription factor participating in N uptake in roots. The homologs of these genes in rice were identified based on amino acid sequence similarity and knocked out using CRISPR/Cas9 mediated gene editing (GE). The AAP2-KO and CRF4-KO lines were subjected to agronomic evaluations with three N doses: 100% (180 kg ha-1), 50% (90 kg ha-1), and 0% (0 kg ha-1) and showed a 130-175% increase in dry biomass weight and a 183-313% increase in panicle number compared to wild type (WT) in the first experiment. These lines also had slower leaf senescence, the so-called “stay-green” trait, indicating the KO effect of target genes in N metabolism. However, neither AAP2-KO nor CRF4-KO showed better yield or ANUE than WT. This study demonstrated the usefulness of GE technology in gene evaluation and highlighted the effects of AtAAP2 and AtCRF4 genes in the plant N cycle.

Assessing fertilizer nitrogen sources and application timing for water‐seeded rice systems

AbstractIn California's water‐seeded rice systems, both high yields and nitrogen (N) use efficiency are achieved when the pre‐plant N fertilizer (usually aqueous‐ammonia [aqua‐N]) is injected into a dry seedbed before flooding and planting. However, there are situations where applying N fertilizer in this manner is not possible. The objective of this study was to evaluate alternative N management practices by testing different N sources and application times. In 2020, we tested 13 treatments and in 2021, six more treatments were added. The following N sources were evaluated: urea, ammonium sulfate, and three enhanced efficiency nitrogen fertilizers (EENFs). Application times for the EENFs, urea, and ammonium sulfate were one day after flooding and 2 weeks after flooding. Urea and ammonium sulfate were also applied in a four‐way split. In 2021, additional treatments were added with aqua‐N, ammonium sulfate, and urea applied before flooding, and urea applications at 3, 4, and 5 weeks after flooding. Grain yield and agronomic nitrogen use efficiency (ANUE) were used for comparison. All fertilizer N treatments increased grain yields relative to the zero‐N control, which averaged 5093 kg ha−1. Applying aqua‐N or urea preplant to a dry soil resulted in the highest yields and ANUE. The EENF fertilizers performed similarly to or worse than urea applied alone. If the field was already flooded, splitting urea applications was the best option. Only one split N treatment was evaluated in this study; this warrants further research on fine‐tuning the best N splits for these systems.

In-season assessment of agronomic nitrogen use efficiency and its components in winter wheat using critical nitrogen dilution curve.

Accurate and timely nitrogen (N) scheduling requires knowledge of in-season crop N deficit. Therefore, understanding the association between crop growth and crop N demand during its growth period is imperative for fine-tuning N scheduling decisions to actual crop N demand and to enhance N use efficiency. The concept of the critical N dilution curve has been employed to assess and quantify the intensity and time of crop N deficit. However, research regarding the association between crop N deficit and N use efficiency in wheat is limited. The present study was carried out to determine whether there are relationships between the accumulated nitrogen deficit (Nand) and agronomic N use efficiency (AEN) as well as with its components (N fertilizer recovery efficiency (REN) and N fertilizer physiological efficiency (PEN)) of winter wheat and to explore the potential capacity of Nand for predicting AEN and its components. Data acquired from five variable N rates (0, 75, 150, 225, and 300kg ha-1) field experiments using six winter wheat cultivars were used to establish and validate the relationships between Nand and AEN, REN, and PEN. The results indicated that plant N concentration in winter wheat was significantly affected by N application rates. Nand varied from -65.73 to 104.37kg ha-1 after Feekes stage 6 under different N application rates. The AEN and its components were also affected by cultivars, N levels, seasons, and growth stages. A positive correlation was observed between Nand, AEN, and its components. Validation using an independent data set showed the robustness of the newly developed empirical models to accurately predict AEN, REN, and PEN with an RMSE of 3.43kg kg-1, 4.22%, and 3.67kg kg-1 and RRMSE of 17.53%, 12.46%, and 13.17%, respectively. This indicates that Nand has the potential to predict AEN and its components during the growth period of winter wheat. The findings will assist in improving in-season N use efficiency by fine-tuning N scheduling decisions in winter wheat cultivation.

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.

Effects of Planting and Nitrogen Application Patterns on Alfalfa Yield, Quality, Water–Nitrogen Use Efficiency, and Economic Benefits in the Yellow River Irrigation Region of Gansu Province, China

Appropriate planting and nitrogen application patterns to support high-quality production of cultivated forage in light of issues of water scarcity, extensive field husbandry, and low productivity in cultivated grassland planting areas were investigated in this study. Using Medicago sativa L. (alfalfa) as the research object, this study analyzed the effects of planting patterns (conventional flat planting (FP) and ridge culture with film mulching (RM)) and nitrogen level (N0: 0 kg·ha−1, N1: 80 kg·ha−1, N2: 160 kg·ha−1, N3: 240 kg·ha−1) on the growth, yield, quality (crude protein content (CP), acid detergent fiber content (ADF), neutral detergent fiber content (NDF), and relative feeding value (RFV)), the water–nitrogen use efficiency, and economic benefits (EB) of alfalfa in the year of establishment. Results demonstrated that (1) RM might greatly increase the growth of alfalfa when compared to FP. The plant height, stem diameter, and leaf:stem ratio of alfalfa all increased under the same planting patterns before decreasing as the nitrogen application rate (NAR) increased. (2) Appropriate NAR combined with RM could improve the yield and quality of alfalfa. Compared with other treatments, the yield, CP, and RFV under RMN2 treatment increased by 5.9~84.9%, 4.9~28.6%, and 19.6~49.3%, respectively, and the ADF and NDF decreased by 14.0~27.6% and 13.0~26.1%, respectively. (3) Under the same nitrogen level, RM showed better performance than FP in terms of water use efficiency (WUE), irrigation water use efficiency (IWUE), precipitation use efficiency (PUE), partial factor productivity of nitrogen (PFPN), agronomic nitrogen use efficiency (ANUE), and EB of alfalfa. Under the same planting pattern, PFPN decreased as the NAR increased, while WUE, IWUE, PUE, ANUE, and EB first increased and then decreased as the NAR increased and reached a maximum value under the N2 condition. In conclusion, the RM planting pattern combined with a nitrogen level of 160 kg·ha−1 can significantly promote alfalfa growth as well as the yield, quality, water–nitrogen use efficiency, and EB of alfalfa, making it a suitable planting management mode for alfalfa production in the Yellow River irrigation region in Gansu Province, China and areas with similar climate.

Optimizing Agronomy Improves Super Hybrid Rice Yield and Nitrogen Use Efficiency through Enhanced Post-Heading Carbon and Nitrogen Metabolism

The super hybrid rice breeding program in China has raised genetic yield ceilings through morphological improvements and inter-subspecific heterosis. Despite this, little information on the physiological basis underlying this yield transformation exists, and less so on the genotype x environment x management conditions enabling consistent yield gains. Here, we assess grain yield, photosynthetic physiology, and leaf carbon and nitrogen (N) metabolic properties of super rice (Y-liangyou900) under four management practices (i.e., zero-fertilizer control, CK; farmers’ practice, FP; high-yield and high-efficiency management, OPT1; and super-high-yield management, OPT2) using a field experiment conducted over five years. Grain yield and agronomic N use efficiency (AEN) of OPT2 were 15% and 10% higher than OPT1, and 30% and 78% higher than FP, respectively. The superior yields of OPT2 were attributed to higher source production capacity, that is, higher leaf photosynthetic rate, carbon metabolic enzyme activity (i.e., AGP and SPS), nitrogen metabolic enzyme activity (i.e., NR, GS, and GOGAT), soluble protein and sugar content, and delayed leaf senescence (the latter due to elevated activity of protective enzyme systems) during grain filling. The higher AEN of OPT2 was associated with higher activity of leaf carbon metabolic enzyme (i.e., AGP and SPS), nitrogen metabolic enzyme (i.e., NR, GS, GDH, and GOGAT) and protective enzyme (POD) after heading, and lower C/N ratio in grains. We conclude that optimized management (optimized water and fertilizer management with appropriate dense planting) improved grain yield and N use efficiency simultaneously by enhancing post-heading leaf carbon and N metabolism and delayed leaf senescence.

Overexpression of Nitrate Transporter 1/Peptide Gene OsNPF7.6 Increases Rice Yield and Nitrogen Use Efficiency.

Overuse of nitrogen fertilizer in fields has raised production costs, and caused environmental problems. Improving nitrogen use efficiency (NUE) of rice is essential for sustainable agriculture. Here we report the cloning, characterization and roles for rice of OsNPF7.6, a member of the nitrate transporter 1/peptide transporter family (NPF). The OsNPF7.6 protein is located in the plasma membrane, expressed in each tissue at all stages and is significantly regulated by nitrate in rice. Our study shows that the overexpression of OsNPF7.6 can increase the nitrate uptake rate of rice. Additionally, field experiments showed that OsNPF7.6 overexpression increased the total tiller number per plant and the grain weight per panicle, thereby improving grain yield and agronomic NUE in rice. Thus, OsNPF7.6 can be applied to be a novel target gene for breeding rice varieties with high NUE, and provide a reference for breeding higher yielding rice.

Polymer-coated urea application can increase both grain yield and nitrogen use efficiency injaponica-indicahybrid rice

AbstractWe investigated whether the one-time application of polymer-coated urea (PCU) before transplanting could simultaneously improve the grain yield and nitrogen use efficiency (NUE) ofjaponica-indicahybrid rice (JIHR) through a field experiment. The local high-yield JIHR cultivar Chunyou-927 was field grown during the rice-growing seasons in 2019 and 2020. The experiment consisted of three treatments: no nitrogen application (0N), application of conventional urea (CU), and the one-time application of PCU. Grain yield was 1.0–1.3 t/ha higher, and agronomic NUE (kg grain yield increase per kg N applied) was 5.2–5.9 kg/kg higher, respectively, under the PCU treatment compared with the CU treatment across the two study years. When compared with the CU treatment, the PCU treatment could (1) improve root morphological trait, (2) reduce redundant vegetative growth during the early growth period, (3) increase matter production during the mid and late growth period, and (4) increase plant activity during the grain-filling period. Overall, our findings indicate that one-time PCU application before transplanting of the JIHR cultivar holds great promise for increasing grain yield and NUE.

Straw return and nitrogen fertilization regulate soil greenhouse gas emissions and global warming potential in dual maize cropping system

Abundant nitrogen (N) fertilization is needed for maize (Zea mays L.) production in China because of its huge residual biomass return. However, excessive N fertilization has a negative impact on the soil ecosystem and environment, which contributes to climate change. Soil incorporation of maize residues is a well-known practice for reducing chemical N fertilization without compromising maize yield and soil fertility. Thus, residues incorporation has the capacity to minimize N fertilization uses and hence mitigate soil greenhouse gas emissions by improving plant N uptake and use efficiency. There is still a research gap regarding the effects of maize residues incorporation on maize yield, soil fertility, greenhouse gas emissions, and plant N and carbon (C) contents. Therefore, we conducted a field experiment during spring and autumn involving four different N fertilization rates (N0, N200, N250, and N300 kg N ha−1), with and without maize residues incorporation, to evaluate grain yield, soil fertility, plant N and C contents, and greenhouse gas emissions (GHGs). Compared to N0, N fertilizer application at 300 kg N ha−1 with residues incorporation significantly increased area-scaled global warming potential (GWP) compared to other N fertilization rates in both spring and autumn seasons, but soil nutrient contents and plant N and C contents were not statistically different from the N250 treatment. In contrast, the N recovery use efficiency (NRUE), physiological N use efficiency (PNUE), and agronomic N use efficiency (ANUE) were significantly lower in the N300 treatment than in the lower N treatment groups. Nitrous oxide (N2O) and carbon dioxide (CO2) fluxes, area-scaled GWP, and greenhouse gas intensity (GHGI) were significantly lower in the N200 treatment with straw incorporation than the N250 and N300 treatments of the traditional planting system. Thus, we concluded that N200 treatment with residues incorporation is optimal for improving grain yield, soil fertility, plant N uptake, and mitigating greenhouse gas emissions.

The difference method is not necessarily reliable for comparing the nitrogen use efficiency of hybrid rice cultivars with different tolerance to low nitrogen conditions

The difference method is one of the most commonly used methods to measure crop nitrogen (N) use efficiency. This study aimed to test the reliability of using this method to evaluate the N use efficiency of low-N tolerant hybrid rice. Two years of N fertilization experiments were conducted to compare yield attributes and N use efficiency measured by the difference method between two hybrid rice cultivars with contrasting tolerance to low N conditions, i.e. Deyou 4727 (D4727) with higher tolerance and Y-liangyou 900 (Y900) with relatively lower tolerance. Results showed that D4727 produced 17–24% higher grain yield than Y900 under zero-N fertilization conditions, confirming the higher tolerance of D4727 to low N conditions. Higher grain weight, harvest index, and internal N use efficiency were responsible for the higher grain yield in D4727 than in Y900. However, recovery efficiency of N determined by the difference method was not consistently different between D4727 and Y900, and physiological N use efficiency (PEN) and agronomic N use efficiency (AEN) determined by the difference method were 31–68% lower in D4727 compared to Y900. The lower PEN and AEN in D4727 than in Y900 were mainly due to a higher grain yield in D4727 than in Y900 under unfertilized conditions. This study suggests that the difference method is not necessarily reliable for comparing the N use efficiency of rice cultivars with different tolerance to low-N conditions, and both crop performance under unfertilized conditions and N responses under fertilized conditions should be considered when using this method to evaluate the N use efficiency of rice.

Contrasting corn yield responses to nitrogen fertilization in southeast coastal plain soils

Nitrogen (N) fertilizer recommendations based on yield goals are common and do not consider variability in soil N supply between fields. Nitrogen transformations in soils are dynamic and may vary widely among different soils, climates, cropping systems, and management practices, making it difficult to provide general N recommendation rates for a region, state, or even a county. To optimize N fertilization rates for corn (Zea mays L.), eight field trials were conducted on different fields at the Edisto Research and Education Center of Clemson University in 2018–2021. The soils varied in pH, inorganic N, management practices (irrigate, dryland, cover, and no-cover crop), and climatic conditions (temperature and precipitation). Six nitrogen fertilizer rate treatments were used during 2018 and 2019, eight in 2020, and five in 2021 trials. Test sites were different in each year except in 2021 in which trials were conducted on the same site but were differentiated by multi-species and no-cover crop treatments. Nitrogen fertilizer was applied as a complete one-time dose in all trials in 2018 and 2021 and in several splits in 2019 and 2020. The corn yields generally increased with N fertilization rates; however, a strong variation of up to 4–11 Mg ha−1 existed at each N level among different fields. Based on yield responses, the eight field trials were divided into two groups: low-yielding and high-yielding sites. The low-yielding sites on average produced 3.8 Mg ha−1 of corn, which was 137% less than the corn harvested from high-yielding sites (9.0 Mg ha−1). The agronomic N use efficiency (AgNUE) in high-yielding sites was almost double (32.68 kg kg−1 N) compared to low-yielding sites (17.16 kg kg−1 N), and the differences were even wider for partial factor productivity of N (PFPN). The economic optimum N rate (EONR) remained below 300 kg N ha−1 for all sites with no marked difference among sites. However, relative yield (ratio of corn yield in unfertilized control to the N level giving the highest yield) was comparatively lower in low-yielding sites (29.45%). Baseline inorganic N, pH, and precipitation were identified as the major factors controlling corn yield responses to N fertilization. The yield variations driven by several factors make N management challenging, indicating the need for site-specific N management for corn in the southeast United States.

Grain yield and nitrogen use efficiency of an ultrashort-duration variety grown under different nitrogen and seeding rates in direct-seeded and double-season rice in Central China

Nitrogen (N) and seeding rates are important factors affecting grain yield and N use efficiency (NUE) in direct-seeded rice. However, these factors have not been adequately investigated on direct-seeded and double-season rice (DDR) in Central China. The objective of this study was to evaluate the effects of various N and seeding rates on the grain yield and NUE of an ultrashort-duration variety grown under DDR. Field experiments were conducted in 2018 in Wuxue County and 2019 in Qichun County, Hubei Province, China with four N rates and three seeding rates. The results showed that the grain yield of the ultrashort-duration variety ranged from 6.32 to 8.23 t ha–1 with a total growth duration of 85 to 97 days across all treatments with N application. Grain yield was increased significantly by N application in most cases, but seeding rate had an inconsistent effect on grain yield. Furthermore, the response of grain yield to the N rates was much higher than the response to seeding rates. The moderate N rates of 100–150 and 70–120 kg N ha–1 in the early and late seasons, respectively, could fully express the yield potential of the ultrashort-duration variety grown under DDR. Remarkably higher N responses and agronomic NUE levels were achieved in the early-season rice compared with the late-season rice due to the difference in indigenous soil N supply capacity (INS) between the two seasons. Seasonal differences in INS and N response should be considered when crop management practices are optimized for achieving high grain yield and NUE in ultrashort-duration variety grown under DDR.

Rice Yield and Nitrogen Use Efficiency With System of Rice Intensification and Conventional Management Practices in Mkindo Irrigation Scheme, Tanzania

AimThis study investigated the impacts of system of rice intensification (SRI) and conventional management practice (CP) on rice growth, grain yield, and nitrogen use efficiency by nitrogen application.MethodsField experiments were conducted in wet and dry seasons; each season, the experiment was set in a split-plot randomized complete block design in triplicate with crop management practices in main plots and nitrogen levels in subplots.ResultsThe average grain yield by SRI was 7.1 and 6.7 t ha−1, while by CP it was 6.1 and 4.4 t ha−1in the wet and dry seasons, respectively. The grain yield of the SRI practice was significantly (p < 0.05) greater than that of the conventional practice (CP) at all levels of nitrogen application. The average yield under the treatment interaction of SRI and nitrogen levels were increased by 13.1% in the wet season and 35.8 % in the dry season. Roots of SRI plants had significantly (p < 0.05) greater fresh weight, length, and volume as indicated by increased root dry weight per hill. SRI improved crop growth, effective tillers, filled grains per panicle, grain filling rate, panicle weight, spikelet per panicle, straw yield, and 1,000-grain weight. Nitrogen application rate had a significant effect (p < 0.05) on agronomic nitrogen use efficiency (ANUE). As the N application rate was increased beyond 90 kg N ha−1, the ANUE and partial factor productivity (PFP) under both SRI and CP were significantly decreased in both seasons.ConclusionOverall, the SRI production system with 60 kg N ha−1 improved rice growth, yield, and nitrogen use efficiency compared to the CP.

Nitrogen efficiency indexes association with nitrogen recovery, utilization, and use efficiency in spring barley at various nitrogen application rates

AbstractThe nitrogen use efficiency (NUE) is the ratio of the N uptake by the plant to the total amount of applied N fertilizer. The optimization of NUE is essential for sustainable agriculture, especially in the breeding programs to improve the yield of barley (Hordeum vulgare L.). We investigated the NUE variation in 32 barley genotypes and to examine the response relationship between phenotypic traits and N level to determine the traits essential for the selection of breeding programs to optimize the NUE. The NUE was investigated in 32 barley genotypes for 2 yr under field conditions using three N levels (60, 120, and 180 kg N ha−1). Growth, physiological and agronomic traits, and N efficiency‐related parameters were determined. The parameters investigated were significantly affected by N application and its interactions with traits. Plant height, biological yield, spike length, and grain number (GN) were increased at higher N levels, but the 1,000‐grain weight decreased. The lowest grain yield was 2,000.7 kg ha−1 at 60 kg N ha−1, and the highest was 8,607.9 kg ha−1 at 120 kg N ha−1. An increase in the N rate from 60 to 120 kg N ha−1 was associated with a higher total chlorophyll content (CHLSPAD) (from 19.04 to 23.13), but no significant change in CHL was seen at 180 kg N ha−1. The agronomic nitrogen use efficiency (ANUE), fertilizer N recovery efficiency and the nitrogen utilization efficiency were both reduced with an increase of the N application rate. A path analysis revealed that GN was the most essential trait for NUE breeding program selection due to its high direct effect (0.72) on ANUE. A linear discriminant analysis showed that CHL at 60 d after sowing was the best trait for distinguishing low from high N levels.

Synchronizing Nitrogen Fertilization and Planting Date to Improve Resource Use Efficiency, Productivity, and Profitability of Upland Rice.

Synchronizing nitrogen (N) fertilization with planting date (PD) could enhance resource use efficiency and profitability of upland rice (Oryza sativa L.) production in Thailand. The objective of the study was to assess upland rice responses to four N fertilization rates (NFRs) and three planting dates. Field experiments were conducted during two growing seasons under four NFRs, no N applied (N0), 30 (N30), 60 (N60), and 90 kg N ha−1 (N90), and NFR were applied at the initiation of tillering and panicle emergence stages. The planting dates selected were early (PD1), intermedium (PD2), and late planting (PD3) between September and December of each season. The NFRs and planting dates had a significant influence on N uptake, N use efficiency (NUE), crop water productivity, yield and yield attributes, and profitability of upland rice production. A linear relationship among NFRs, agronomic traits of upland rice, N uptake, and crop water productivity was observed, and a significant seasonal effect was indicated. Fertilization at N90 under PD2 enhanced yields, yield attributes, and grain yields, as well as crop water productivity by 56 and 105% during the second and first seasons, respectively. Grain N, total N, and straw N were increased by 159, 159, and 160%, and by 90, 114, and 153%, during the first and second seasons, respectively. Enhanced N efficiencies, including agronomic efficiency, recovery efficiency, partial factor productivity, and N harvest index, at varying NFRs were observed under PD2 during both seasons. Highly significant (p < 0.001) and positive associations were observed among agronomic attributes, N uptake, NUE, and crop water productivity of upland rice in correlation assessment. Profitability from grain yields was observed with N fertilization and N90 resulted in maximum profit under all the PDs. However, the highest marginal benefit-cost ratio was observed at N60 under PD2 during both seasons. The results suggest that the NFR of 90 kg N ha−1 and planting at the end of September or start of October would enhance resource use efficiency and productivity, and maximize profitability. Furthermore, long–term field investigations with a range of NFRs and adopting forecasting measures to adjust the planting date for upland rice are recommended.

Slow but sure: the potential of slow-release nitrogen fertilizers to increase crop productivity and farm profit in Nepal

Reduction of nitrogen (N) input in cropping systems is critical to reduce environmental pollution and achieve sustainable development goals. Multi-location field trials for maize (n = 120) and rice (n = 84) were conducted across nine districts in Nepal during 2018 and 2019 to assess the potential of polymer coated urea (PCU) and urea briquette (UB) to increase agronomic N use efficiency (AEN), crop productivity and farm profits over conventional urea (CU). Nitrogen rates applied in PCU and UB treatments were 22% to 50% lower than CU (120 and 100 kg N ha−1 for maize and rice respectively). In maize, both PCU (8.4 t ha−1) and UB (8.5 t ha−1) applied at 50% and 25% lower N rates respectively produced similar grain yields compared with CU (7.9 t ha−1). Similar results were observed in rice where PCU and UB applied at 22% less N led to a productivity of 5.4 and 5.5 t ha−1 respectively over CU (5.1 t ha−1). Moreover, both PCU and UB increased maize and rice yields significantly compared with current farmer’s practices (FP). In both maize and rice, PCU and UB significantly increased partial factor productivity of N (PFPN) and agronomic NUE (AEN) compared with CU. Furthermore, PCU and UB increased farmer’s net income by US$88 and US$148 in maize and by US$10 and US$87 in rice respectively. These results suggest that PCU and UB could save N input by 22-50% while maintaining similar or even higher yield and higher benefit to farmers compared with CU.

Reasonable Nitrogen Regime in the Main Crop Increased Grain Yields in Both Main and Ratoon Rice

Planting ratoon rice can realize one sowing and two harvests, which is of great significance for improving grain yield. However, the effects of nitrogen (N) regime in the main crop on the grain yield of ratoon rice and the associated physiological mechanisms are not clearly understood. The indica hybrid rice Liangyou 6326 was used, and three N fertilizer levels (100 kg ha−1 (low N, LN), 250 kg ha−1 (medium N, MN), and 400 kg ha−1 (high N, HN)) and four different ratios of basal tillering fertilizer to panicle fertilizer (7:3, 6:4, 5:5, and 4:6) applied to the main crop were designed to investigate their effects on the grain yields of the main and ratoon crops. The results showed that excessive N application rate and panicle N application rate in the main crop was not conducive to the improvement of yield and agronomic nitrogen use efficiency (ANUE) in both seasons. The increased yield in the ratoon crop was attributed to the increase in the regeneration rate. Appropriate increasing of the panicle N application rate was beneficial for increasing the ROA and NSC concentration in the main crop, resulting in an increase in the number, length, and fresh weight of regenerated buds, which caused an improvement in the regeneration rate. However, when excessive panicle N was applied in the main crop, the excessive germination of regenerated buds decreased the length and fresh weight of the regenerated bud and resulted in a decrease in the regeneration rate. These results suggest that in the production of ratoon rice, reasonable N regime in the main crop could increase the yield and ANUE in both seasons.