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Rice yield and nitrogen use efficiency will be affected by different nitrogen (N) application rate. However, previous studies were limited on different nitrogen fertilization rate under deep placement. In order to study the effect of different nitrogen fertilization rate on grain yield, nitrogen use efficiency and its physiological traits under deep placement in mechanical pot-seedling transplanting rice, the field experiment was conducted with two rice varieties Meixiangzhan-2 (MXZ-2) and Y-liangyou 1378 (YLY-1378) from July to November of 2021. And a radioisotope N15 tracer experiment was conducted. There were five fertilizer treatments used as basal fertilizer: all N-fertilizer were deeply applied with application rates of 150 kg ha−1 by machine (T1); all N-fertilizer were deeply applied at a 10% reduction (135 kg ha−1) by machine (T2); all N-fertilizer were deeply applied at a 15% reduction (127.5 kg ha−1) by machine (T3); all N-fertilizer were manually surface broadcast with application rates of 150 kg ha−1 (T4) and blank treatment was designed without N-fertilizer (T0). The results showed that 31.20 and 26.42% higher grain yield, 63.09 and 58.52% higher nitrogen recovery efficiency, and 121.58 and 121.04% higher nitrogen agronomic efficiency in T1 and T2 than T4 for MXZ-2 and YLY-1378, respectively. Nitrogen derived from fertilizer in T1 and T2 was enhanced by 43.72 and 26.96% than T4 for MXZ-2, 49.54 and 32.97% for YLY-1378, respectively. Nitrogen residual rate of T1 and T2 was increased by 26.59 and 46.36% than T4 for MXZ-2, 8.62 and 20.24% for YLY-1378, respectively. The increase in NUE was due to the increase in nitrogen metabolism enzyme activity including nitrate reductase (NR), glutamine synthetase (GS) and glutamate synhthase (GOGAT) promoted by deep N-fertilization. The total chlorophyll content, leaf area index (LAI) and total aboveground biomass (TAB) under T1 and T2 were also enhanced compared with T4. There was also no significant difference on grain yield or NUE between T1 and T2. Hence, basal nitrogen fertilizer with 135 kg N ha− 1 under deep placement is an efficient method to increase grain yield and nitrogen use efficiency in mechanical pot-seedling transplanting rice in South China. [ABSTRACT FROM AUTHOR]

Different fertilization methods will affect rice yield and its growth. To address the influence of different fertilization methods on yield, photosynthetic intensity, and nitrogen synthetase enzymatic activities for hill direct-seeded rice, the field trials were conducted using two different rice varieties Yuxiangyouzhan and Wufengyou 615 in 2018 and 2019. There were four fertilizer application treatments at the rate of 150 kg N ha−1 in hill direct-seeded rice: All the fertilizer deep application as a disposable basal fertilizer by machine (T1); deep application of mechanized decrement fertilizers, i.e. 50% of all fertilizers into 10 cm depth of soil as basal by machine, whilst 25% of fertilizers at tillering stage and 25% of the fertilizer in the panicle initiation (PI) stage were artificially sown on the soil surface (T2), respectively; farmers' manually traditional surface broadcast, i.e. 40% of the fertilizers as the basal fertilizer, whilst 30% of fertilizers was applied at tillering and PI stage (T3), respectively, and the control treatment is no fertilization (T0). The result showed that grain yield of Yuxiangyouzhan and Wufengyou 615 for T2 was increased by 25.79 and 11.98%, compared with T3, respectively. The rate of photosynthetic, water use efficiency and stomatal conductance for T2 treatment was 35.86, 27.32, and 56.87% higher than that for T0 treatment, respectively. It was also found that T2 had the highest chlorophyll and carotenoids during the heading stage (HS). We also observed that glutamine systhetase (GS) and glutamate synhthase (GOGAT) activities of T2 were higher than T3 at mid-tillering stage for both rice varieties, respectively. Among all treatments at the HS, Wufengyou 615 had the largest leaf area index and total above-ground biomass. Hence, the present study revealed that 50% of total amount of fertilization as basal fertilization deep placement with the rest of fertilization as topdressing more benefited the rice growth and produced more grain yield. [ABSTRACT FROM AUTHOR]

This study aimed to determine the mechanism of exogenous melatonin application in alleviating the combined Pb and Cd (Pb-Cd) toxicity on aromatic rice (Oryza sativa L.). In this study, a pot experiment was conducted; two aromatic rice varieties, Yuxiangyouzhan and Xiangyaxiangzhan, were selected, and sprays using 50, 100, 200, and 400 μmol L−1 melatonin (denoted as S50, S100, S200, and S400) and irrigation using 100, 300, and 500 μmol L−1 melatonin (denoted as R100, R300, and R500) were also selected. The results showed that, under the S50, S100, and S200 treatments, the Pb content of aromatic rice grain decreased, and the grain yield increased significantly. Moreover, the application of exogenous melatonin significantly reduced the accumulation of H2O2 in rice leaves at maturity under Cd–Pb stress and reduced the MDA content in Xiangyaxiangzhan leaves. In addition, the microbial community structure changed significantly under S50 and R300 treatments. Some pathways, such as the synthesis of various amino acids and alanine, aspartate, and glutamate metabolism, were regulated by S50 treatment. Overall, melatonin application improved aromatic rice grain yield while reducing heavy metal accumulation by regulating the antioxidant capacity and metabolites in aromatic rice plants and altering the physicochemical properties and microbial community structures of the soil. [ABSTRACT FROM AUTHOR]

2-acetyl-1-pyrroline (2AP) is recognized as the key aromatic compound in fragrant rice, however, the effect of light quality on rice aroma is not fully understood. In this study, two fragrant rice varieties (Xiangyaxiangzhan and Yuxiangyouzhan) were grown under four light quality treatments (CK: natural light, L1: red light, L2: blue light and L3: combined light). Results depicted that L1, L2 and L3 treatments enhanced the grain yield by 14.24–35.36%, compared to CK whilst L2 and L3 treatments reduced the 2AP content in grains by 17.18–28.68%. Moreover, L1, L2 and L3 treatments enhanced the grain yield owing to improved filled grain percentage and regulation in antioxidant enzyme activities. On the other hand, L2 and L3 reduced the 2AP content in grains by decreasing pyrroline-5-carboxylic acid content and modulating proline and γ-aminobutyric acid content. Overall, this study revealed that light quality substantially affects the grain yield and quality characters of fragrant rice. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the effects of deep application of nitrogen (N) fertilizer and straw incorporation on grain yield and quality, nutrient accumulation, and root morphological and physiological traits in both rice (Oryza sativa L.) cultivars during 2019 and 2020. The experimental treatments were comprised of deep N fertilization with (DF+S) and without straw incorporation (DF) as well as broadcasting fertilization with (BF+S) and without straw return (BF). No fertilizer and no straw return treatment were taken as control. Results depicted that the DF+S and DF treatment significantly increased the grain yield by 46.4 and 42.2%, respectively, compared with BF. The DF+S also significantly increased total N accumulation by 37.9 and 44.0%, total phosphorus accumulation by 39.3 and 41.7%, total potassium accumulation by 63.6 and 73.3% for the cultivars Yuxiangyouzahn (YXYZ) and Wufengyou615 at maturity, respectively, compared with BF. Moreover, nutrient accumulation and grain yield of BF+S were slightly higher than BF. Straw incorporation resulted in better total root volume and total root length than no straw incorporation treatments in YXYZ, regardless of fertilizer application method. Root morphology traits are positively associated with other positive traits such as yield or nutrient uptake. The DF+S treatment also significantly increased the milled rice rate and remarkably reduced the chalkiness degree for both rice cultivars, compared to BF treatment. Overall, DF+S is recognized as the optimal method to improve rice productivity and quality with better nutrient acquisition. Core Ideas: Deep N placement resulted in consistently better nutrient accumulation than broadcasting fertilizer (BF) treatment, regardless of straw incorporation.Deep N placement could improve the root morphology traits compared to BF, regardless of straw incorporation.Deep N placement coupled with straw incorporation significantly improved milled rice rate and remarkably reduced the chalkiness degree compared to BF. [ABSTRACT FROM AUTHOR]

Deep placement of nitrogen (N) fertilizer has become one of the effective management practices for increasing crop yield and improving N recovery efficiency (NRE). However, it is unclear how different N fertilization depths affect grain yield, nitrogen use efficiency, and root characteristics in direct-seeded rice (DSR) in South China. Here, we conducted stainless steel-box experiment to evaluate the effects of different N fertilization depths at four fertilization depths (0, 4, 8, and 12 cm, written as D0, D4, D8, and D12, respectively) with a conventional ammonium bicarbonate fertilizer (TN = 17.7%) (150 kg N ha−1) and a control (no N fertilizer applied, CK) on grain yield, NRE, and root characteristics of DSR. The results indicated that both D8 and D12 significantly increased grain yields by 72.91 and 81.84%, respectively, compared with CK. The highest nitrogen agronomic efficiency (NAE) and NRE were found under D12 treatment, which were increased by 165.42 and 129.45% compared to D0, respectively. We also found that deep placement of N fertilizer (both D8 and D12) could also promote rice root growth such as larger root length, root superficial area, and thicker root diameter. Furthermore, nitrate reductase (NR), glutamine synthetase (GOGAT), and glutamine synthetase (GS) activities of flag leaves at the heading stage were also increased. The result shows that both 8 and 12 cm are relatively reasonable fertilization depths depended on adopted rice varieties when ammonia bicarbonate fertilizer is used in DSR production. [ABSTRACT FROM AUTHOR]

The influences of γ-aminobutyric acid (GABA) and nitrogen on grain yield, yield-related traits, plant growth, grain–leaf ratio and NSC contents in different fragrant rice genotypes are not fully understood. A pot experiment was conducted with four nitrogen rates, i.e. 0, 0.87, 1.75, and 2.61 g pot−1, two GABA levels, i.e. 0 and 250 mg L−1, and three fragrant rice cultivars, i.e. Yuxiangyouzhan, Yungengyou 14 and Basmati. Results depicted that GABA treatment significantly increased the mean grain yield by 11.84% as a consequence of the increment of grain weight, spikelet per pot, grain weight per leaf area, stem sheath dry weight at HS, panicle dry weight at HS, panicle dry weight at MS and total dry weight at MS. Besides, significant effects of nitrogen and cultivar on yield and yield-related traits and some rice growth parameters were observed. Moreover, significant positive correlation relationships between yield and panicle number per pot, leaf area and dry weight for all the cultivars were observed. GABA application could alleviate the effects of nitrogen on grain yield in fragrant rice. These results suggest that GABA is feasible to increase grain yield and improve rice plant growth for fragrant rice varieties grown under different nitrogen conditions. [ABSTRACT FROM AUTHOR]

Cloudy weather with low light is more common during rice growing season of South China which often leads reduced yield and aroma formations in fragrant rice. However, exogenous γ-aminobutyric acid (GABA) application could enhance the 2-acetyl-1-pyrroline (2AP) accumulations and yield of fragrant rice under low light conditions. Field and pot experiments were conducted with three fragrant rice cultivars i.e., Basmati and Yuxiangyouzhan (indica), and Yungengyou 14 (japonica) that were grown under three different treatments i.e., normal light + GABA 0 mg L−1 (CK), low light + GABA 0 mg L−1 (T1), and low light + GABA 250 mg L−1 (T2). The results revealed that the grain 2AP contents were increased by 14.67–34.83% and up to 29.34% under T1 and T2 treatments in pot and field experiments, respectively, as compared with CK. The T1 and T2 treatments improved aroma owing to regulation in the accumulation of micronutrients i.e., Na, Mn, and Fe and enzyme activities involved in 2AP biosynthesis. The grain yield was substantially reduced in T1 as compared with T2 treatment for all rice cultivars. On the other hand, GABA application improved the grain yield under low light conditions by regulating the plant growth, and related physiological and biochemical attributes in all rice cultivars. Thus, GABA could balance low light-induced 2AP content and grain yield by modulating morphological and yield related attributes as well as physio-biochemical responses of fragrant rice. The roles of GABA in alleviating the effects of low light on fragrant rice plants. Foliar application of GABA positively altered several physio-biochemical processes in plants, improved the balance between 2-acetyl-1-pyrroline (2AP) content and yield in fragrant rice under low light conditions [Display omitted] • GABA improved the yield and 2AP contents in fragrant rice under low light conditions. • GABA-induced modulation in yield is linked to the regulations of yield related attributes. • Alteration in 2AP biosynthesis related traits caused aroma regulations under GABA × low light. • Activities of enzymes involved in 2AP biosynthesis varied from heading to maturity stage. • GABA affected the accumulation of Na, Mn and Fe in fragrant rice under low light conditions. [ABSTRACT FROM AUTHOR]

The effect of the light quality on 2-acetyl-1-pyrroline (2AP) during the grain filling period in fragrant rice has rarely been investigated. A pot experiment was carried out with two fragrant rice varieties, Xiangyaxiangzhan and Yuxiangyouzhan, grown under three light treatments, 100% red light (L1), 100% blue light (L2), and compound light (L3), during the grain filling period, and natural light was taken as the control (CK). The yield, quality, and fragrance were investigated. The results showed that light quality treatments significantly decreased the 2AP content in mature grains by 16.67–32.82% but improved the grain yield by 2.70–21.41% compared to CK. The regulation effects of light quality treatments on grain yield and 2AP are linked to yield-related traits, biomass accumulation, antioxidant physiology, and 2AP formation-related physiology. Additionally, light quality treatments decreased the chalky rice percentage and chalkiness, and increased the length-to-width ratio. Overall, light quality treatments during the grain filling period had a positive effect on the grain yield but not on fragrance in fragrant rice. [ABSTRACT FROM AUTHOR]

Mechanical pot-seedling transplanting (PST) is an efficient transplanting method and deep nitrogen fertilization has the advantage of increasing nitrogen use efficiency. However, little information is available about the effect of PST when coupled with mechanized deep nitrogen (N) fertilization on grain yield, nitrogen use efficiency, and antioxidant enzyme activities in rice. A two-year field experiment was performed to evaluate the effect of PST coupled with deep N fertilization in both early seasons (March–July) of 2018 and 2019. All seedlings were transplanted by PST and three treatments were designed as follows. There was a mechanized deep placement of all fertilizer (MAF), broadcasting fertilizer (BF), no fertilizer (N0). MAF significantly increased grain yield by 52.7%. Total nitrogen accumulation (TNA) was enhanced by 27.7%, nitrogen partial factor productivity (NPFP) was enhanced by 51.4%. nitrogen recovery efficiency (NRE) by 123.7%, and nitrogen agronomic efficiency (NAE) was enhanced by 104.3%, compared with BF treatment. Moreover, MAF significantly improved peroxidase (POD), catalase (CAT), and notably reduced the malonic dialdehyde (MDA) content for both rice cultivars, compared to BF. Hence, the result shows that mechanical pot-seedling transplanting coupled with nitrogen deep placement is an efficient method with the increase of grain yield and nitrogen use efficiency in rice cultivation in South China. [ABSTRACT FROM AUTHOR]

Background: Water (W) and nitrogen (N) management generally cause regulations in the 2-acetyl-1-pyrroline (2AP) accumulation in fragrant rice; nevertheless, the feasibility of such management strategies at booting stage in improving 2AP accumulation has not been examined in details. Methods: Field experiments were conducted in the early season (March–July) and repeated in the late season (July–November) in 2013. The treatments were applied urea (90 kg ha− 1), calcium super phosphate (90 kg ha− 1) and potassium chloride (195 kg ha− 1) as basal fertilizer, and urea (65 kg ha− 1) at tillering stage. Three N levels i.e., 0 kg N ha− 1 (N1), 30 kg N ha− 1 (N2), and 60 kg N ha− 1 (N3) and three water levels i.e., W1 treatment (well-watered treatment with water layer of 2–4 cm), W2 treatment (soil water potential was − 15 ± 5 kPa), and W3 treatment (soil water potential was − 25 ± 5 kPa) at booting stage was set up for three rice varieties i.e., Nongxiang 18, Yungengyou 14 and Basmati. The grain yield, head milled rice yield, 2AP contents and the biochemical parameters related to 2AP formation were investigated. Results: Result indicated that W and N dynamics regulated the grain yield, head milled rice yield, and 2AP contents in brown rice across three varieties. The N2 and N3 treatment significantly increased the 2AP contents in brown rice by 9.54% and 11.95%, and 8.88% and 32.54% in the early and the late season, respectively; improved grain yield and head milled rice yield. The W3 treatment improved grain yield, head milled rice yield and 2AP content. Significant W and N interaction effect on 2AP content in brown rice was detected, where the W3 N3 treatment showed the strongest interaction regarding improvement of 2AP contents in brown rice. The 2AP accumulation and its related biochemical parameters and their relationships in different plant tissues at different growth stages under W and N treatments had also been assessed. The 2AP content, P5C content and DAO activity during grain filling periods was highly related to the 2AP content in brown rice. Conclusion: This study revealed that the 60 kg N ha− 1 coupled with − 25 ± 5 kPa treatment showed the best positive effects on yield and aroma in fragrant rice, suggested that water and nitrogen management at booting stage can improve grain yield and fragrance in fragrant rice. However, further study to evaluate the metabolic and molecular basis of 2AP accumulation in fragrant rice is needed. [ABSTRACT FROM AUTHOR]

Present study aimed to assess silicon (Si) mediated yield, grain quality and regulations in 2-acetyl-1-pyrroline accumulation (2-AP) in aromatic rice. Four different levels of Si at 15, 30, 45 and 60 mg kg −1 were applied to two aromatic rice cultivars i.e., Nongxiang 18 and Meixiangzhan 2, while pots without Si were served as control (CK). Results revealed that Si fertilization improved 2-AP, Si and proline contents in leaves and grains as well as activities of proline dehydrogenase (PRODH) and net photosynthetic rates (Pn) (in leaves) while interfered with total N contents in leaves and grains. Moreover, leaves N and proline contents, and net photosynthetic rates (Pn) were decreased with plant age i.e., tillering > flowering > maturity while PRODH activities and Si contents were highest at flowering and maturity stages, respectively and minimum at tillering stage. Furthermore, growth, yield and quality components were also improved by Si application but results were not consistent regarding grain quality for both rice cultivars. Further, Si contents in leaves have significant positive relations ( r = 0.3974 , P < 0.05) with grain 2-AP contents at flowering stage. Hence, Si proved better for both rice cultivars whereas 2-AP contents were higher for Meixiangzhan 2 than Nongxiang 18. [ABSTRACT FROM AUTHOR]

Deep nitrogen fertilization (DNF) coupled with straw incorporation has the potential to improve the grain yield and nitrogen use efficiency of mechanically transplanted rice. However, the effects of different fertilization approaches combined with straw incorporation on lodging resistance ability, and soil properties are still uncertain. Therefore, a two-year field experiment was comprised of broadcast fertilizer treatments (broadcast fertilizer without straw (BFS0) or with straw (BFS)), deep fertilizer treatments (DNF without straw (DFS0) or with straw (DFS)). Results depicted that deep fertilizer treatments significantly improved the pushing resistance force by 63.81–129.58 % and decreased the lodging index by 22.01–80.82 % of rice compared with broadcast fertilizer treatments. Deep fertilizer treatments optimized the length of the first four internodes and increased the internodes diameter and culms wall thickness in the third and fourth internode, and higher silicon and lignin content in the fourth internode, compared to broadcast fertilizer treatments. Furthermore, the straw incorporation treatments also improved soil total nitrogen, soil available potassium, and soil organic matter by 5.60–11.48 %, 17.75–22.56 %, and 7.17–18.26 %, respectively, regardless of fertilizer application method. Hence, this study suggests that deep nitrogen fertilization can be adopted as an agronomically effective tactic to improve lodging resistance in rice whilst the combination of straw incorporation and deep fertilization can be considered to further improve the soil properties. • Deep N fertilization (DNF) improved lodging resistance in rice compared to broadcast fertilization. • The DNF coupled with straw incorporation improved soil nitrogen status and organic matter content. • The DNF with straw incorporation did not reduce the lodging index as compared to DNF without straw. [ABSTRACT FROM AUTHOR]

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 15N 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. [ABSTRACT FROM AUTHOR]

In general, nitrogen (N), silicon (Si), and planting method influence fragrant rice yield and lodging resistance. Nevertheless, the response of fragrant rice yield and lodging resistance to N-Si fertilization under different planting methods has not been examined in detail. Field trials were undertaken in the early seasons of 2018 and 2019. Two Si levels i.e., 0 kg Si h m−2 (Si0) and 150 kg Si h m−2 (Si1), three N levels i.e., 0 kg N h m−2(N0), 150 kg N h m−2(N1), and 220 kg N h m−2(N2) as well as three planting methods i.e., artificial transplanting (AT), mechanical transplanting (MT), and mechanical direct-seeding (MD) were set up for two indica fragrant rice cultivars i.e., 'Yuxiangyouzhan' (YX) and 'Xiangyaxiangzhan' (XY). Results revealed that the N-Si treatments and planting methods significantly affected the grain yield, lodging index, and some related parameters across the two cultivars. The mean fold change (FC) in grain yield for the different planting methods was ranked MD＞MT＞AT, while MT and MD have larger variation of FC in grain yield and lodging index as compared with AT. Besides, under all planting methods, the N1 and N2 treatments significantly increased grain yield and lodging index, while the Si1 treatment significantly reduced lodging index without affecting grain yield. There were also significant Si and N interaction effects on grain yield and lodging resistance, with the Si1N2 treatment producing the best balance of grain yield and lodging resistance. The treatments differed in grain yield and yield-related traits such as yield components, biomass yield and photosynthetic properties, as well as in lodging index and lodging-related traits such as plant height, N and Si content in the stem sheath, and biomass allocation ratio. Overall, this study revealed that the 150 kg Si h m−2 coupled with 220 kg N h m−2 treatment showed the best positive effects on balancing grain yield and lodging resistance under all planting methods. Additionally, fragrant rice planted by mechanical methods requires more stricter N-Si fertilization because mechanical planting methods produce greater variation in the physio-biochemical characteristics that underlie grain yield formation and lodging resistance. • Nitrogen (N) fertilization significantly increased grain yield and lodging risk. • Silicon (Si) fertilization significantly reduced lodging risk without affecting grain yield. • Mechanical direct-seeding showed higher variation in grain yield and lodging index than artificial transplanting at N-Si. • Application of 150 kg Si hm−2 and 220 kg N hm−2 produced the optimal balance between grain yield and lodging resistance. [ABSTRACT FROM AUTHOR]

Increasing energy output and improving energy production efficiency is essential to ensure the long-term sustainability of rice production systems in China. Present study assessed the energy input/output and its production efficiency for manual transplanted rice with manual broadcasting fertilizer (TR-MBF), mechanical pot-seedling transplanted rice synchronized with deep fertilization (MPST-DF), and mechanical hill direct-seeding rice synchronized with deep fertilization (MHDS-DF) in a three-year field experiment. Two rice cultivars i.e., Yuxiangyouzhan (YXYZ, inbred rice) and Wufengyou615 (WFY615, hybrid rice) were used to determine the energy input/output and production efficiency of each system. Results depicted that the MHDS-DF and MPST-DF treatment substantially improved the grain yield by 20.9% and 32.3% for WFY615 and YXYZ owing to enhanced total above-ground biomass (TAB) and leaf area index (LAI), respectively. Means across years and cultivars for energy input in the TR-MBF, MPST-DF, and MHDS-DF were remained 31918.0, 35267.1 and 36036.7 MJ ha−1, respectively. The energy consumed by diesel and fertilizer for energy inputs in the production system exceeds 70% of the total energy input. Moreover, the three rice production systems were highly dependent on non-renewable energy. The highest output energy and net energy were obtained for MHDS-DF and MPST-DF treatments with 221517.2 and 185670.0 MJ ha-1, respectively. Among the three rice production systems, the highest energy use efficiency, energy productivity efficiency, energy profitability efficiency was found in MPST-DF, which was slightly higher than MHDS-DF. However, the human energy profitability efficiency of MHDS-DF treatment was significantly higher than other treatments. Therefore, MHDS-DF and MPST-DF could be best alternative technologies than conventional rice production systems with improved energy input and energy production efficiency in South China. Furthermore, both MHDS-DF and MPST-DF would also be suitable in the regions with lack of labor force for rice production. • Deep fertilization substantially improved the yield and energy output in rice production systems. • MPST-DF had the highest energy production efficiency than other rice production systems. • MHDS-DF significantly improved HEPF for both rice cultivars. [ABSTRACT FROM AUTHOR]

• Application of chelated selenium significantly increased net photosynthetic and grain yield of fragrant rice. • Lower chalky rice rate and chalkiness were recorded in chelated selenium treatments as well as higher protein content. • Grain 2-acetyl-1-pyrroline content in fragrant rice increased due to the application of chelated selenium. • The activities of enzymes related to 2-acetyl-1-pyrroline biosynthesis were regulated by chelated selenium. The main aim of the present study was to explore the effect of chelating selenium (Se) on aromatic rice performance. A field experiment was conducted in 2017 and 2018. At initial heading stage, five different Se solutions of 0, 10, 20, 30 and 40 μmol L−1 were applied to rice leaves and named as CK, Se1, Se2, Se3 and Se4 treatments, respectively. The results showed 1.64–10.78 % higher seed-setting rate and 2.17–6.98 % higher 1000-grain weight in the chelating Se treatments than in the CK. Compared with the CK, the Se2 and Se3 treatments increased the grain yield and net photosynthetic rate by 8.24–14.65 % and 8.00–24.74 %, respectively. The Se2 and Se3 treatments also increased grain protein contents and reduced both the chalky rice rate and chalkiness. Moreover, the Se1, Se2 and Se3 treatments increased the grain content of 2-acetyl-1-pyrroline (2-AP) by 15.02–47.47 % compared with CK. The contents of proline, △1-pyrroline-5-carboxylic acid (P5C) and 1-pyrroline (precursors in 2-AP biosynthesis) and the activities of proline dehydrogenase (ProDH), ornithine aminotransferase (OAT), and diamine oxidase (DAO) were also improved under the Se1, Se2 and Se3 treatments compared to CK. Furthermore, the chelating Se applications improved the total Se and Fe content in grains. The Se2 treatment was considered as the optimum concentration for chelating Se application in fragrant rice production. [ABSTRACT FROM AUTHOR]