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With the existing model of chemical fertilizer application faces, improving grain yield and quality is challenging. Fragrant rice is known for its distinctive aroma and flavor, but it generally produces less grain than non-fragrant rice varieties. Limited research has been conducted on the potential of biochar as a solution for increasing the grain yield of fragrant rice. In a two-year field trial conducted in 2022 and 2023, two fragrant rice cultivars, Meixiangzhan2 (MXZ2) and Xiangyaxiangzhan (XYXZ), were selected as the experimental materials. These rice cultivars were subjected to four different rates of biochar application: no biochar treatment(T1); biochar with 0.375 t ha−1 (T2); biochar with 0.75 t ha−1 (T3); and biochar with 1.50 t ha−1 (T4). The results showed that the grain yield of both cultivars increased to an extent in both 2022 and 2023 (an 8.57–33.77% increase for MXZ2; a 6.00–21.59% increase for XYXZ). Furthermore, under the T2, T3, and T4 treatments, there was an increase in the number of effective panicles, seed setting rate, 1000-grain weight, biomass accumulation, net photosynthetic rate, and intercellular CO2 concentration. However, the transpiration rate and stomatal conductance decreased. The content of 2-acetyl-1-pyrroline (2-AP) increased with an increased rate of biochar application, and the highest content was observed under the T4 treatment (153.54–178.32 µg kg−1 in 2022; 163.93–180.28 µg kg−1 in 2023). The activities of proline dehydrogenase (PDH) and 1-pyrrolin-5-carboxylic acid synthase (P5CS), as well as the contents of proline (PRO), 1-pyrrolin-5-carboxylic acid (P5C), ∆1-pyrroline, and methylglyoxal, were improved under the T2, T3, and T4 treatments compared to the T1 treatment. Moreover, under the T2, T3, and T4 treatments, the brown rice rate, milled rice rate, and head rice rate increased, while the chalkiness degree and chalk rice rate decreased. Our correlation analysis showed that grain yield was positively correlated with total biomass accumulation, the number of grains per panicle, and the seed setting rate. Additionally, the content of 2-AP showed positive correlations with PRO, P5C, ∆1-pyrroline and methylglyoxal, and the activities of PDH and P5CS. In conclusion, applying biochar at a rate of 1.5 t ha−1 can be more effective in increasing the grain yield and 2-AP content of fragrant rice. [ABSTRACT FROM AUTHOR]

The present study was conducted to assess the effects of water and nitrogen applications at the booting stage on yield, grain quality, and nutrient use efficiencies in fragrant rice in the early (March–July) and late (July–November) seasons of 2013. The experiment was comprised of two fragrant rice cultivars, i.e., Nongxiang 18 and Basmati; three nitrogen levels, i.e., 0 kg N ha−1 (N0), 30 kg N ha−1 (N1), and 60 kg N ha−1 (N2); and three water levels, i.e., 2–4 cm water layer well-watered (W0), water with a soil water potential of −15 ± 5 kPa (W1), and water with a soil water potential of −25 ± 5 kPa (W2), which were randomized in a split-split plot design. Results showed that Basmati produced a higher grain yield than Nongxiang 18 (16.20 and 9.61% in the early and late season, respectively), whereas the W1 exhibited the maximum grain yield and harvest index. The moderate application of nitrogen (N1) at the booting stage resulted in higher grain yield, nevertheless, cultivar, water, and nitrogen revealed different trends for some of the grain quality attributes, i.e., brown rice rate, milled rice rate, head milled rice rate, protein content, and amylose content as well as nutrient uptake and use efficiencies in the double rice production system. Basmati had a higher nitrogen harvest index (NHI; 18.28–20.23%) and P harvest index (PHI; 3.95–12.42%) but lower physiological P use efficiency for biomass (PPUEB; 7.66–23.66%) and physiological K use efficiency for biomass (PKUEB; 2.53–7.10%) than Nongxiang 18 in both seasons. Furthermore, the grain number per panicle, biomass yield, grain P uptake, and the whole plant P uptake were significantly related to the grain yield of fragrant rice. In both seasons, the interaction of water and nitrogen (W × N) had a significant effect on panicle number, grain quality attributes, and N, P uptake of straw, as well as the physiological N, P use efficiency for grain and the physiological N, K use efficiency for biomass. Overall, results suggest that moderate nitrogen and irrigation input at the booting stage could be feasible to improve the productivity and quality of the double rice production system with improved nutrient use efficiency under the agro-climatic conditions of 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]

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]

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]

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]

Mechanical hill direct-seeded rice synchronous with deep placement of N fertilizer (MHDSR-NF) is an efficient alternative to conventional transplanted-flooded rice (CTFR), however, little is known about the effects of MHDSR-NF on grain yield, nitrogen use efficiency (NUE), and economic profitability. In present study, two types of N fertilizer viz., commercial compound fertilizer (CF) and ammonia bicarbonate (AB), placed mechanically at 10 cm of soil depth (M) or broadcasted manually (B), (written as CFM, CFB, ABM and ABB, respectively) in two rice cultivars viz., Tianyou998 and Yuxiangyouzhan which were grown in both early and late seasons of 2014 in double rice cropping system of South China. Plants without N fertilizer application were taken as control (N0). Compared to surface broadcasting, mechanically deep placement of N fertilizer enhanced NUE and grain yield significantly while improved nitrogen recovery efficiency (NRE) by 32.52–50.79%, 21.51–32.68%, and nitrogen agronomy efficiency (NAE) by 32.10–50.43%, 19.47–38.78%, of Tianyou 998 and Yuxiangyouzhan , respectively, in both seasons. Compared to surface broadcasting, the grain yields of Tianyou 998 and Yuxiangyouzhan under mechanically deep placement of N fertilizer were also increased by 6.31–8.03% and 4.70–6.78%, respectively, which were ascribed to the increased spikelet number per panicle. Furthermore, the lower production cost and the higher total return in CFM led to the highest benefit-cost ratio (BCR) in CFM, followed by CFB and ABM, whereas the lowest BCR was recorded for ABB. In addition, significant improvements were also observed in leaf area index, total aboveground biomass, and photosynthesis rate in CFM at the heading stage. Catalase (CAT) and Peroxidase (POD) activities of the uppermost leaves were significantly higher under deep placement of N fertilizer than surface broadcasting. Hence, mechanized deep placement of commercial compound fertilizer can be taken as an efficient fertilization method in mechanical hill direct-seeded rice in South China. [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]

Cadmium (Cd) contamination in agricultural soil is a global concern for soil health and food sustainability because it can cause Cd accumulation in cereal grains. An in-situ stabilizing technology (using organic amendments) has been widely used for Cd remediation in arable lands. Therefore, the current study examined the influence of vermicompost (VC) on soil biochemical traits, bacterial community diversity and composition, Cd uptake and accumulation in rice plants and grain yield in a Cd-contaminated soil during the late growing season in 2022. Different doses of VC (i.e., V1 = 0 t ha -1 , V2 = 3 t ha -1 and V3 = 6 t ha -1 ) and two concentrations of Cd (i.e., Cd1 = 0 and Cd2 = 50 mg Cd Kg -1 were used. We performed high-throughput sequencing of 16S ribosomal RNA gene amplicons to characterize soil bacterial communities. The addition of VC considerably affected the diversity and composition of the soil bacterial community; and increased the relative abundance of phyla Chloroflexi, Proteobacteria, Acidobacteriota, Plantomycetota, Gemmatimonadota, Patescibacteria and Firmicute. In addition, VC application, particularly High VC treatment, exhibited the highest bacterial diversity and richness (i.e., Simpson, Shannon, ACE, and Chao 1 indexes) of all treatments. Similarly, the VC application increased the soil chemical traits, including soil pH, soil organic carbon (SOC), available nitrogen (AN), total nitrogen (TN), total potassium (TK), total phosphorous (TP) and enzyme activities (i.e., acid phosphatase, catalase, urease and invertase) compared to non-VC treated soil under Cd stress. The average increase in SOC, TN, AN, TK and TP were 5.75%, 41.15%, 18.51%, 12.31%, 25.45% and 29.67%, respectively, in the High VC treatment (Pos-Cd + VC3) compared with Cd stressed soil. Redundancy analysis revealed that the leading bacterial phyla were associated with SOC, AN, TN, TP and pH, although the relative abundance of Firmicutes, Proteobacteria, Bacteroidata, and Acidobacteria on a phylum basis and Actinobacteria, Gammaproteobacteria and Myxococcia on a class basis, were highly correlated with soil environmental factors. Moreover, the VC application counteracted the adverse effects of Cd on plants and significantly reduced the Cd uptake and accumulation in rice organs, such as roots, stem + leaves and grain under Cd stress conditions. Similarly, applying VC significantly increased the fragrant rice grain yield and yield traits under Cd toxicity. The correlation analysis showed that the increased soil quantities traits were crucial in obtaining high rice grain yield. Generally, the findings of this research demonstrate that the application of VC in paddy fields could be useful for growers in Southern China by sustainably enhancing soil functionality and crop production., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflicts of interest., (Copyright © 2023 Elsevier B.V. All rights reserved.)