Increase Rice Yield Research Articles

Impact of biological manure substitution on grain yield, nitrogen recovery efficiency, and soil biochemical properties.

Fertilization plays a crucial role in ensuring global food security and ecological balance. This study investigated the impact of substituting innovative biological manure for chemical fertilization on rice (Oryza sativa L) productivity and soil biochemical properties based on a three-year experiment. Our results suggested rice yield and straw weight were increased under manure addition treatment. Specifically, 70% of total nitrogen (N) fertilizer substituted by biological manure derived from straw, animal waste and microbiome, led to a substantial 13.6% increase in rice yield and a remarkable 34.2% boost in straw weight. In comparison to the conventional local farmer practice of applying 165 kg N ha-1, adopting 70% of total N plus biological manure demonstrated superior outcomes, particularly in enhancing yield components and spike morphology. Fertilization treatments led to elevated levels of soil microbial biomass carbon and N. However, a nuanced comparison with local practices indicated that applying biological manure alongside urea resulted in a slight reduction in N content in vegetative and economic organs, along with decreases of 10.4%, 11.2%, and 6.1% in N recovery efficiency (NRE), respectively. Prudent N management through the judicious application of partial biological manure fertilizer in rice systems could be imperative for sustaining productivity and soil fertility in southern China.

Bio-nano selenium fertilizer improves the yield, quality, and organic selenium content in rice

To investigate the impact of bio-nano Se on rice yield and quality and Se accumulation, three different forms of Se were applied: Se nanoparticles (SeNPs) synthesized by Proteus penneri LAB-1, a conventional inorganic Se fertilizer (sodium selenite) and an organic Se fertilizer (selenomethionine). The relative chlorophyll content of rice increased in plants treated with the different Se treatments and reached the highest level in the 5 mg/L bio-nano Se treatment. However, the height of rice showed little change. Applying 20 mg/L SeNPs increased rice yield by about 5% compared with organic Se treatment and 6% with inorganic Se treatment. Compared with the control, spraying 20 mg/L bio-nano, organic and inorganic Se on the leaf surface increased the soluble sugar content of rice by about 70%, 59% and 61%, respectively, and the amylose content by 15%, 11% and 10% and decreased soluble protein content by 25%, 18% and 22%, respectively. The Se content of rice increased with the increasing of spraying Se concentration. After spraying 10 mg/L of bio-nano Se, the Se content in the rice reached 271.2–306.5 µg/kg, and the proportion of organic Se was over 85.0%, which met the Se-rich rice and safety standards. This study provides a reference for determining the appropriate bio-nano Se supply level and developing Se-rich rice.

Polypeptide urea increases rice yield and nitrogen use efficiency through root growth improvement

ContextElucidating rice root growth and development characteristics is essential for improving nitrogen use efficiency (NUE) and grain yield (GY) of crops, particularly in light of innovations such as polyaspartic acid (PASP)–urea formulations. However, the effectiveness of PASP–urea on the morphological properties of rice roots is insufficiently explored. ObjectiveWe aimed to examine the effect of PASP–urea on root morphology properties, NUE, and grain yield of mid-season rice in southwest China. MethodsIn 2016 and 2017, a two-factor randomized block design experiment was conducted in Sichuan, China, during the rice planting season. Three N treatments: no N (control), conventional urea [CU], and polyaspartic acid–urea [PU] were administered to two rice varieties: Yixiangyou 2115 and Fyou 498. ResultsOur findings showed that grain yield and nitrogen recovery efficiency (NRE) of rice were closely related to the root surface area density (RSAD), root length density (RLD), and root volume density (RVD) of rice. Compared to the CU treatment, the PU application significantly boosted the root dry matter weight, RLD, RVD, and RSAD of both varieties by 12.00–16.87 %, 0.16–28.98 %, 12.41–37.06 %, and 8.14–33.66 % at the jointing, heading, and maturity stages, respectively. This contributed to a 0.37–15.63 % and 23.45–48.12 % increase in grain yield and NRE, respectively, in both years, and a 12.26–15.69 % increase in N partial productivity efficiency (NPPE) in 2017 by improving the effective panicle number per unit area, spikelets per panicle, and N uptake. ConclusionNRE and grain yield of rice were significantly increased by PU application by improving the rice root system. ImplicationsThe study findings offer insight on how PASP–urea application influences the root morphology of rice and its relationship with grain yield and NRE while offering novel strategies and concepts for optimizing N use in rice cultivation.

Adjusting harvesting time according to nitrogen application rate maximizes rice yield and nitrogen use efficiency

Nitrogen (N) and harvest time are important factors in determining rice production potential. Elucidating reasonable N application rates and the relationship between N rate and harvesting time is necessary to maximize rice yield and efficiency. Two field trials were conducted with four N levels (0, 82.5, 165, and 247.5 kg N ha−1) and five N levels (0, 90, 180, 270, and 360 kg N ha−1) in Shayang (SY) and Wuxue (WX) counties, Hubei Province, respectively. Each was harvested at two time points (T1 and T2), at and after maturation, to investigate grain yield and N use efficiencies of rice. The results showed that the applied N and appropriately adjusted harvesting time significantly increased the grain yield, and compared with zero-N, the N additions increased rice yield by 3.7–26.9% and 8.4–22.5% for the SY and WX sites, respectively. However, with the increase of N application rate, the N use efficiency first increased and then decreased. Effects of harvest time on grain yield and N use efficiency vary with N application rates. At higher N levels, the appropriate delay in harvest time (T2) resulted in an increase in the 1000-grains weight and the rate at which grains were filled. Consequently, this led to an overall increase in grain yield. However, with zero or low N application rates, delayed harvest (T2) resulted in grain abscission, which decreased grain yield. In summary, applying N appropriately significantly increased the rice yield, and adjusting the harvesting time according to the N application rate further increased grain yield and N use efficiency.

Nature-based solutions to increase rice yield: An experimental assessment of the role of birds and bats as agricultural pest suppressors in West Africa

Rice is widely consumed as a staple food, being cultivated worldwide. However, in West Africa, production is not enough to satisfy demand. Rice often suffers intensive damage by herbivorous arthropods that affect quality and quantity of the grain. Birds and bats have been shown to suppress arthropod pests, potentially enhancing rice productivity and food security. However, the degree to which these taxa provide nature-based solutions for mitigating pest-induced rice losses is poorly known, especially in West Africa. Here, we used experimental exclosures to investigate whether birds and bats reduce plant damage and boost rice yield by suppressing arthropod abundance. In a rural area in northern Guinea-Bissau, we established 14 sets of paired control and experimental exclosures parcels, precluding access of birds and bats to rice plants. We then quantified how the absence of birds and bats influenced arthropod communities, plant damage, and rice yield over a full rice production cycle (six months). Arthropod numbers in exclosures (10.1 ± 9.1 ind./plot) were nearly double those in control plots (5.8 ± 3.0 ind./plot), a result mostly due to a lower spider abundance in the controls. The percentage of leaf and grain damage showed no difference between exclosure and control. Using Structural Equation Models, we uncovered that the exclusion of birds and bats boosted arthropod abundance but had only marginal effects on rice damage and no detectable effect on yield. The exclusion of flying vertebrates led to a marked increase in spider abundance, suggesting an effect of mesopredator release, which in turn likely helped maintaining pest abundance low and potentially contributing to the small overall effect on rice damage and yield. Enhancing the abundance of birds and bats is an interesting option to suppress agricultural pests, but our results highlight the need for a better understanding of ecological interactions in agricultural landscapes in West Africa. We stress the need for more research to inform evidence-based policies using nature-based solutions that foster the natural consumption of pests by vertebrates, as a means to improve food security.

Isolation of endophytic fungi from wild rice species for disease management and growth promotion in cultivated rice (Oryza sativa L.)

ABSTRACT The focus of plant health management is shifting from synthetic chemicals to bio-agents, and endophytes are beneficial for this purpose. In the present study, we isolated eleven endophytic fungi from seven wild rice species. Independent treatment of endophytic fungi in rice showed significant improvements in plant growth, higher tillering and percent fertility, panicle number/hill and filled grain number in endophyte-inoculated plants compared to control plants. Growth promotion activities of two endophytes Curvularia lunata (NRRI EF-11) and Hypocreals sp. (NRRI EF-8) were recorded with increased rice yield. These isolates also exhibited higher plant growth promoting chemicals namely, Indole acetic acid (IAA) and Inorganic phosphate (IP) which was realised into better growth promotion in rice. The biocontrol efficacy of endophytic fungi was highest in NRRI EF-11among all isolates as indicated by inhibition of radial growth of pathogens by 76.98–77.06% and in NRRI EF-8 by 74.81–76.61%, which is due to higher production of prussic acid. Defense induction was confirmed by analyzing the expression of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) defense enzymes, where expression of CAT, POD and SOD increased by 19.44–25.86, 2.70–3.16, 11.14–12.95 Units g−1 in treated NRRI EF-11 plants and 18.39–25.84, 2.16–2.94, 10.96–12.62 Units g−1 in treated NRRI EF-8 plants, respectively. These two endophytes have the potentiality to manage crop health in a sustainable way.

Application of Planting System and Organic Fertilizer on the Yield of Inpari IR Nutri Zinc in Lampung

The low rice productivity in Lampung needs to be increased. The objectives of this study were to introduce new superior Inpari IR Nutri Zinc rice and determine the effect of planting systems and biofertilizer on the growth and yield of Inpari IR Nutri Zinc rice in technically irrigated rice fields in Lampung. The experiment was carried out in technically irrigated rice fields in Kalirejo Village, Negeri Katon District, Pesawaran Regency, Lampung Province, using a split-plot design in a randomized block design with three replications. The treatments tested were three rice planting systems as the main plot and the dose of biofertilizer as a sub-plot. The parameters observed components of growth and yield components. Data were analyzed with the SAS software 5.4 version. The results showed that the application of biofertilizers gave effects on rice yield. From the results of this study, it can be concluded that the use of biofertilizers can increase rice yields by 10-12% compared to those without biofertilizers, in the three cropping systems. The application of biofertilizers resulted in the highest harvested dry grain production, namely 6.61 tons per hectare and significantly different than that without biofertilizers, namely 5.96 tons per hectare. The production of dry grain harvested by the three cropping systems was not significantly different at an average of 6.28 tons per hectare.

Straw management adopted by large farms sustains grain yield but mitigates greenhouse gas emissions

ContextStraw incorporation is a globally recommended strategy for enhancing soil fertility. The methods for straw incorporation adopted by large farms usually differ from those used by small households, primarily because of variations in cost affordability. However, the effects of straw management on rice yields and greenhouse gas (GHG) emissions have not been well explored at different farming scales. ObjectivesThis study aims to compare the grain yield and greenhouse gas emissions under different straw management adopted by large farms than small households. MethodsA three-year field experiment using split-plot design, with straw management as the main plot and preceding tillage as the sub-plot, was conducted in a wheat-rice rotation system. Four treatments were given as rotary tillage with straw removal (RT-S), rotary tillage with straw incorporation (RT+S; small households), ploughing tillage with straw removal (PT-S), and ploughing tillage with straw incorporation (PT+S, large farms) in the preceding wheat season. Soil tillage in the rice season was the same, which was rotary tillage after irrigation. ResultsStraw incorporation significantly increased methane (CH4) and nitrous oxide (N2O) emissions, and 60%-62% of CH4 was emitted during the transplanting to jointing stages while 45–73% of N2O was emitted during the jointing to the booting stage. The stimulation of CH4 and N2O emissions by straw incorporation was closely correlated to enhanced soil organic carbon (SOC) and denitrification enzyme activity, respectively. In the last year, PT+S significantly reduced the global warming potential (GWP) compared to RT+S in the whole rice season, which can be attributed to the dramatically decline of CH4 emission, even though N2O emission was increased. Additionally, the decreased CH4 emission was mainly due to lower methanogenic activity, and the increased N2O emission was mainly resulted from lower nosZ abundance under PT+S compared to RT+S. Straw incorporation increased rice yield by 15.73% on average in the last two years, and rice yield of PT+S in the last year was significantly enhanced by 27.50%, resulting in a lower greenhouse gas intensity (GHGI) by 25.54% compared to RT+S. ConclusionStraw management practices adopted by large farms (PT+S) have the potential to synchronize high rice yields with lower GHG emissions compared to small households (RT+S). ImplicationsOur findings provide some evidence that large-scale agricultural organization may be helpful for sustainable rice production in China.

Interactions of Microbial Inoculations with Fertilization Options and Crop Establishment Methods on Modulation of Soil Microbial Properties and Productivity of Rice

A field investigation was undertaken to assess the interactive effects of different crop establishment methods (CEMs) and microbial formulations in field conditions. The two year experiment was carried out in kharif season (June to October) of both 2013–14 and 2014–15 at Research Farm of ICAR-Indian Agricultural Research Institute, New Delhi India. The CEMs studied consist of puddled transplanted rice (PTR), system of rice intensification (SRI) and aerobic rice system (ARS); while microbial formulations consist of Anabaena sp. (CR1)+Providencia sp. (PR3) consortium (MC1) and Anabaena–Pseudomonas biofilm formulation (MC2). The microbial inoculation was applied with 75% recommended dose of nutrients (RDN) (90 kg nitrogen ha-1 and 19.35 kg phosphorus ha-1) and compared with 100% RDN. Soil microbiological properties showed significantly higher values in SRI in the first year; while in the second year, SRI and PTR remained on par and superior to ARS. Among the combinations of nutrient supplements, application of Anabaena–Pseudomonas biofilm formulation (MC2) with 75% RDN was superior in terms of all microbiological attributes studied [acetylene reduction activity (ARA), soil chlorophyll, soil dehydrogenase activity, microbial biomass carbon and alkaline phosphatase activity]. Application of microbial inoculation led to an increase in milled rice yield from 230 to 240 kg ha-1. Among the different combinations of CEMs and inputs investigated the application of 75% RDN+MC2+zinc (Zn) (soil applied 5 kg Zn ha-1 through zinc sulphate heptahydrate) in SRI can be a judicious option to maximize rice yield and soil health.

Mitigating methane emissions and global warming potential while increasing rice yield using biochar derived from leftover rice straw in a tropical paddy soil

The sustainable management of leftover rice straw through biochar production to mitigate CH4 emissions and enhance rice yield remains uncertain and undefined. Therefore, we evaluated the effects of using biochar derived from rice straw left on fields after harvest on greenhouse gas emissions, global warming potential (GWP), and rice yield in the paddy field. The experiment included three treatments: chemical fertilizer (CF), rice straw (RS, 10 t ha−1) + CF, and rice straw-derived biochar (BC, 3 t ha−1 based on the amount of product remaining after pyrolysis) + CF. Compared with CF, BC + CF significantly reduced cumulative CH4 and CO2 emissions, net GWP, and greenhouse gas emission intensity by 42.9%, 37.4%, 39.5%, and 67.8%, respectively. In contrast, RS + CF significantly increased cumulative CH4 emissions and net GWP by 119.3% and 13.8%, respectively. The reduced CH4 emissions were mainly caused by the addition of BC + CF, which did not increase the levels of dissolved organic carbon and microbial biomass carbon, consequently resulting in reduced archaeal abundance, unlike those observed in RS + CF. The BC + CF also enhanced soil total organic carbon content and rice grain yield. This study indicated that using biochar derived from leftover rice straw mitigates greenhouse gas emissions and improves rice productivity in tropical paddy soil.

The improvement of soil properties in rice cropping systems using an integrated fertilization method to increase rice yield

AbstractThe global food crisis provides an impetus for agricultural green transformation via optimized fertilization methods. While organic substitution, green manure incorporation, and targeted fertilization sites have individually shown promise in enhancing rice yield, there is still a gap between optimized fertilization methods and achieving sustainable rice production. To explore the factors influencing rice yield across different fertilization strategies, we conducted a field experiment in Southern China encompassing five treatments, such as CK (no N input), RN (broadcasting urea with recommended N rates), RON (broadcasting organic–inorganic fertilizer with recommended N rates), RONS (side‐deep placement of organic–inorganic fertilizer with recommended N rates), and RONSA (coupled RONS with Azolla [Azolla pinnata R. Brown]). Using a Minimum Data Set approach, we identified the primary variables influencing soil properties and rice production, with a focus on soil physicochemical characteristics and bacterial communities. Further, the soil properties index (SPI), calculated by multiplying the linear score with the weight of each variable, served as an indicator of soil properties variations. Our findings revealed that RONSA significantly increased the SPI by 21.1% compared with RN, predominantly because of higher soil labile organic carbon (LOC) and available N (SAN) fractions (p < .05). N uptake in rice plants (23.9%–28.4%) increased dramatically under RONSA leading to higher rice yield (11.0%–16.9%) and NUE (30.2%–36.1%) than RN (p < .05). The enhancement in soil properties, characterized by increased LOC, SAN fractions, and bacterial community diversity, was essential in boosting rice yields, with dissolved inorganic N emerging as the dominant contributor. In summary, our results highlight the effectiveness of integrated fertilization approaches in enhancing soil properties, subsequently leading to improved rice yields and NUE. This fertilizer strategy holds promise for guiding field fertilization practices and advancing sustainable rice production.

Biochar and Manure Co-Application Increases Rice Yield in Low Productive Acid Soil by Increasing Soil pH, Organic Carbon, and Nutrient Retention and Availability.

In recent years, overuse of chemical fertilization has led to soil acidification and decreased rice yield productivity in southern China. Biochar and manure co-application remediation may have positive effects on rice yield and improve acid paddy soil fertility. This study was conducted to understand the effects of co-application of wood biochar and pig manure on rice yield and acid paddy soil quality (0-40 cm soil layers) in a 5-year field experiment. The experiment consisted of six treatments: no biochar and no fertilizer (CK); biochar only (BC); mineral fertilizer (N); mineral fertilizer combined with biochar (N + BC); manure (25% manure N replacing fertilizer N) combined with mineral fertilizer (MN); and manure combined with mineral fertilizer and biochar (MN + BC). Total nitrogen application for each treatment was the same at 270 kg nitrogen ha-1y-1, and 30 t ha-1 biochar was added to the soil only in the first year. After five years, compared with N treatments, N + BC, MN, and MN + BC treatments increased the rice yield rate to 2.8%, 4.3%, and 6.3%, respectively, by improving soil organic matter, total nitrogen, and available phosphate under a 0-40 cm soil layer. MN + BC had the strongest resistance to soil acidification among all the treatments. The interaction between fertilizers and biochar application was significant (p < 0.05) in rice yield, soil electrical conductivity (10-20 cm), and soil available phosphate (20-40 cm). Principal component analysis indicated that the effect of manure on soil property was stronger than that of biochar in the 0-40 cm soil layer. The overall rice yield and soil fertility decreased in the order of biochar + mineral fertilizer + manure > mineral fertilizer + manure > biochar + mineral fertilizer > mineral fertilizer > biochar > control. These results suggest that biochar and manure co-application is a long-term viable strategy for improving acid soil productivity due to its improvements in soil pH, organic carbon, nutrient retention, and availability.

Polyploidized rice improves plant height and yield through regulation of the expression of yield-related genes

Polyploidization is one of the most effective ways to improve plant height and yield in rice (&lt;i&gt;Oryza sativa&lt;/i&gt; L.). However, the molecular mechanism of its regulation is not yet fully understood. Here, we investigated the agronomic traits of diploid (‘Balilla- 2x’) and tetraploid (‘Balilla-4x’) lines of the japonica rice variety ‘Balilla’. Compared with ‘Balilla-2x’, ‘Balilla-4x’ exhibited significantly increased plant height, spike length and yield per plant. RNA-seq analysis showed that the expression levels of yield-related genes controlling plant height and panicle development (e.g., &lt;i&gt;STH1&lt;/i&gt;,&lt;i&gt;OsYUC9&lt;/i&gt; and &lt;i&gt;OsDEP1&lt;/i&gt;) were significantly upregulated in ‘Balilla-4x’ rice plants. These results indicated that polyploidization changed the expression of genes related to agronomic traits such as plant height and spike length, thereby increasing rice yield. is study provides a further basis for understanding the yield of rice after polyploidization and can serve as a new theoretical reference for breeding high-yielding rice varieties.

Optimizing the rate of straw returning to balance trade-offs between carbon emission budget and rice yield in China

Rice paddies are a prominent contributor to greenhouse gases (GHGs) emissions, accounting for 22 % of the overall agricultural methane (CH4) emissions. Although returning rice straw to the field can increase yield and soil organic carbon (SOC), the significant GHGs released during this process often negate these positive effects. Thus, understanding the impact of straw returning on the relationship between rice yield and GHGs is crucial for farming adaptation and climate change mitigation. This study aims to investigate the effects of varying straw returning rates on rice yield and GHGs in China and identify the optimal rates on a provincial scale. This study utilized county-level meteorological, soil, and field management data. The Dynamic Nitrogen and Carbon Model (DNDC) model was used to simulate the impacts on rice yield, GHGs, and SOC changes under different straw returning rates in China from 2010 to 2022, including no straw, 1/3, 2/3, and full straw returning. The results showed that 1/3, 2/3, and full straw incorporation increased rice yield per unit area by 1.07 %, 2.25 %, and 3.26 % for single rice cropping, 1.10 %, 2.24 %, and 3.52 % for early rice, and 1.92 %, 3.91 %, and 5.95 % for late rice, respectively. Compared with no straw returning, the total SOC content (0–50 cm) increased by 3.88 % (78.07 Tg), 7.75 % (156.09 Tg), and 11.65 % (234.62 Tg) under 1/3, 2/3, and full straw returning, respectively. However, the total GHGs were increased by 23.32 %, 43.50 %, and 61.48 % for 1/3, 2/3, and full straw incorporation compared to no straw returning. While the overall benefits of straw returning varied across regions, in certain areas like northeastern China, Xinjiang, and Yunnan, an increase in straw returning rates leads to a significant increase in yield with a relatively smaller increase in GHGs. This can be attributed to factors such as lower temperatures, decreased SOC, and lower soil pH, restricting CH4 production. Conversely, in regions with higher soil pH, such as north China and the Sichuan Basin, as well as in warmer southern areas, the increase in GHGs is quite pronounced. In summary, implementing straw returning significantly increases rice production and SOC but simultaneously increases GHGs. In China, the most widespread utilization of rice straw remains straw returning. We have summarized the average impact of straw returning on yield, SOC, and GHGs, and proposed straw returning rates tailored to the comprehensive benefits in different regions, to enhance the carbon sequestration and emission reduction rate of rice straw returning.

The rice endophytic bacterium Bacillus velezensis LS123N provides protection against multiple pathogens and enhances rice resistance to wind with increase in yield

Rice (Oryza sativa) is a globally important staple food, but its production was influenced by various biotic and abiotic stresses. This study involved screening endophytic bacterial strains for their antagonistic activities and control efficacy against multiple rice pathogens in planta assays. Subsequent greenhouse investigations identified Bacillus velezensis LS123N as the most promising strain for effectively controlling various rice diseases, including bacterial blight, rice blast, bakanae disease, Pythium disease, and brown spot disease. Field trials further demonstrated that LS123N significantly reduced naturally occurring brown spot disease caused by Bipolaris oryzae in both seedlings and mature rice plants, and increased rice yields. For disease control against bacterial blight, Pythium disease, and brown spot, only a single treatment during seed germination resulted in significant disease control efficacy. The application of LS123N during seed germination aligns with common rice cultivation practices. Additionally, LS123N exhibited the capacity to improve rice resistance to wind stress and enhance rice growth during the seedling stage. Endophytic colonization of LS123N was evidenced from seed to mature rice plants after seed treatment. Interestingly, the expression of many rice defense genes was suppressed within 48 h of the LS123N introduction. In vitro assays showed that LS123N inhibited spore germination and normal growth of germ tubes of B. oryzae, produced multiple hydrolases, siderophores, and IAA, and had the ability to solubilize phosphorus compounds. In summary, these results indicate that B. velezensis LS123N is a promising biocontrol agent and has the potential to be developed into a biofungicide, biofertilizer, and biostimulator.

The Use of Magnesium Fertilizer Can Improve the Nutrient Uptake, Yield, and Quality of Rice in Liaoning Province

In this study, the effects of the soil application and foliar spraying with magnesium fertilizers on rice yield and quality in Liaoning Province were investigated. Field experiments were conducted at Kaiyuan, Xinmin, and Dawa in 2022 and 2023. Magnesium fertilizers were used in the soil as magnesium sulfate monohydrate and silicon–magnesium fertilizer and on leaves was magnesium sulfate heptahydrate. The results showed that the application of 12 kg magnesium hm−2 in the soil at the Kaiyuan site can significantly increase rice yield by 14.8% compared with sites without magnesium fertilizer. The use of silicon–magnesium fertilizer showed a more obvious yield increase of 22.2%. The application of 3 kg magnesium hm−2 or 6 kg magnesium hm−2 on the leaf surface increased the rice yield at Kaiyuan by 19.4% and 21.6% and at Xinmin by 17.8% and 5.4%, respectively. The yield increase was more significant under the optimal fertilization treatment compared with the conventional fertilization treatment. The application of magnesium fertilizer increased the magnesium, nitrogen, and phosphorus contents in rice shoots and the potassium and crude protein contents in rice grains. The effect of foliar spraying with magnesium fertilizers was more obvious than soil application. Therefore, the magnesium fertilizer used on the leaf surface plays an important role in improving rice yield and quality in rice-growing areas with relatively rich soil magnesium content. Magnesium fertilizer can compensate for the yield decrease caused by the reduced use of nitrogen and phosphorus fertilizers by promoting nitrogen and phosphorus absorption in rice. Conclusively, the application of magnesium fertilizer is a promising measure to improve rice production in Liaoning province under a reduced nitrogen and phosphate fertilizer background.

THOUSAND-GRAIN WEIGHT 6, which is an IAA-glucose hydrolase, preferentially recognizes the structure of the indole ring

An indole-3-acetic acid (IAA)-glucose hydrolase, THOUSAND-GRAIN WEIGHT 6 (TGW6), negatively regulates the grain weight in rice. TGW6 has been used as a target for breeding increased rice yield. Moreover, the activity of TGW6 has been thought to involve auxin homeostasis, yet the details of this putative TGW6 activity remain unclear. Here, we show the three-dimensional structure and substrate preference of TGW6 using X-ray crystallography, thermal shift assays and fluorine nuclear magnetic resonance (19F NMR). The crystal structure of TGW6 was determined at 2.6 Å resolution and exhibited a six-bladed β-propeller structure. Thermal shift assays revealed that TGW6 preferably interacted with indole compounds among the tested substrates, enzyme products and their analogs. Further analysis using 19F NMR with 1,134 fluorinated fragments emphasized the importance of indole fragments in recognition by TGW6. Finally, docking simulation analyses of the substrate and related fragments in the presence of TGW6 supported the interaction specificity for indole compounds. Herein, we describe the structure and substrate preference of TGW6 for interacting with indole fragments during substrate recognition. Uncovering the molecular details of TGW6 activity will stimulate the use of this enzyme for increasing crop yields and contributes to functional studies of IAA glycoconjugate hydrolases in auxin homeostasis.

Soil Nitrogen Distribution Affects Nitrogen Utilization and Yield of Drip-Irrigated Rice

The cultivation of drip-irrigated rice has resulted in lower yields. However, the decrease in rice yield under drip irrigation and its relationship with the existing water and N regime have not been fully explained. Research and development of optimized water and N-management techniques are crucial for increasing rice yield under drip irrigation. In this study, two irrigation treatments were set: conventional drip irrigation (DIO) and drip irrigation with water stress (DIS). Each irrigation treatment contained four N rates: urea N 240 kg ha−1 (LN), urea N 300 kg ha−1 (MN), urea N 360 kg ha−1 (HN), and ammonium sulfate N 300 kg ha−1 (AN). The soil’s ammonium and nitrate contents were measured on the 2nd and 28th days after N application at panicle initiation stage. At anthesis, the aboveground and root biomass of rice were measured. In heading and maturity stage the N content of aboveground was measured and the yield, yield components, and NPFP were assessed at maturity stage. The results showed the following: (1) On the second day after N application, the contents of soil NO3−-N and NH4+-N in the 0–10 cm soil layer were highest for both the DIO and DIS. On the 28th day after N application, the soil NO3−-N content was highest at the 20–40 cm depth, while the soil NH4+-N content was still highest at the 0–10 cm depth. (2) The aboveground and root biomass in DIO treatment were significantly higher than in DIS. Furthermore, the root biomass at the 0–10 cm depth was significantly greater than at the 10–50 cm depth for both the DIO and DIS treatments. In the DIO treatment, the root biomass at the 10–50 cm depth was significantly higher with the HN and AN treatments compared to MN. However, in the DIS treatment, the root biomass at the 10–50 cm depth did not show significant differences between the MN, HN, and AN. (3) N accumulation in rice was significantly higher for the DIO treatment compared to the DIS treatment. Under the same irrigation treatment, the N accumulation in rice was highest in the AN and lowest in the LN. The PrNTA and PrNTC in DIS were significantly higher than in DIO, while the PoNAA and PoNAC were significantly lower in DIS. (4) The number of panicles, spikelets per panicle, seed-setting rate, 1000-grain weight, and grain yield were significantly lower in DIS. Under the DIS, these parameters were not significantly different among the MN, HN, and AN. In the DIO, the seed-setting rate, 1000-grain weight, and yield were not significantly different between the HN and AN, but were significantly higher than in the MN and LN. (5) NPFP was significantly higher in the DIO compared to the DIS. Among the different N rates, NPFP was highest with the AN treatment and lowest with the LN. In summary, under drip irrigation, there was a mismatch between soil mineral N and the distribution of rice roots, leading to reduced N accumulation and utilization in rice, ultimately impacting yield formation. Increasing N application and soil ammonium nutrition can improve rice yield under drip irrigation. However, optimizing N fertilizer management may not increase rice yield further when irrigation is further limited.

Significant Synergy Effects of Biochar Combined with Topdressing Silicon on Cd Reduction and Yield Increase of Rice in Cd-Contaminated Paddy Soil

Pot and field trials were conducted to explore the combined effect of biochar (BC) with topdressing silicon (Si) on Cd uptake by rice and grain yield in Cd-contaminated paddy soil. The treatments, including BC applied before transplanting (TBC), topdressing Si applied in the soil at the jointing stage (JSi) and BC combined with topdressing Si (TBC + JSi), were designed in a complete random block, and treatment without application of BC and Si was used as a control (CK). Results showed that Cd concentration in milled rice treated with TBC + JSi was decreased by 34.62%, 22.73% and 10.53%, respectively, when compared to CK, TBC and JSi, with the concentration being only 0.17 mg·kg−1. At rice maturity, available Cd in the soil was reduced by 7.98% (TBC), 4.76% (JSi) and 6.02% (TBC + JSi) when compared with CK, while the concentrations of total Cd were 32.07% (TBC), 27.85% (JSi) and 35.44% (TBC + JSi) higher than CK. Moreover, BC and Si increased the Cd sequestrated by leaves markedly, especially for TBC + JSi, which was much higher than TBC and JSi. Therefore, the transfer of Cd from leaf to milled rice was greatly decreased by TBC + JSi. In addition, a synergy effect of TBC + JSi on rice yield was also found. Compared with CK, the grain yields of TBC, JSi and TBC+ JSi were increased by 8.35%, 8.20% and 18.74%, respectively. Nutrient contents in soil and rice plants were also elevated by the application of BC and Si to a certain extent; for example, the contents of nitrogen (N), phosphorus (P), potassium (K) and Si in soil treated with TBC + JSi were raised by 8.96–60.03% when compared with CK. Overall, the combined application of BC with topdressing Si not only increases soil nutrients significantly, promotes their uptake by rice and boosts grain yield, but also effectively inhibits Cd transfer and reduces its accumulation in rice, which ultimately guarantees milled rice security. These results also imply that the combined application of biochar with topdressing silicon might be considered as an effective agronomic measure to decrease the milled-rice Cd in Cd-contaminated paddy soil, which would guarantee food security.

Optimizing rice yield, quality and nutrient use efficiency through combined application of nitrogen and potassium.

Reasonable nitrogen (N) and potassium (K) application rates can effectively improve fertilizer use efficiency, rice yield and quality. A two-year field experiment was conducted with combined application of three N rates (135, 180, and 225 kg ha-1, denoted as N1-N3) and four K rates (0, 90, 135, and 180 kg ha-1, denoted as K0-K3) using super indica hybrid rice cultivar Yixiangyou (YXY) 2115 to explore the effects of co-application of N and K on rice growth and development. The results indicated that the combined application of N and K had significantly interactive effects on dry matter (DM) accumulation, nutrients absorption, N harvest index (NHI), K harvest index (KHI), spikelets per panicle and most rice quality indexes. The highest total DM accumulation (17998.17-19432.47 kg ha-1) at maturity stage was obtained under N3K2. The effect of co-application of N and K on nutrients absorption and utilization varied between the two years and within each year. The highest total N and K accumulations at maturity stage were observed under N3K1 and N3K2, respectively, while the highest N recovery efficiency (NRE) and K recovery efficiency (KRE) were observed under N1K3. High expression levels of N and K metabolism-related genes in rice grains were observed under N3K2 or N3K3, consistent with N and K uptake. Co-application of N and K increased rice yield significantly and the highest yield (6745.02-7010.27 kg ha-1) was obtained under N2K2. As more N was gradually applied, rice appearance quality improved but milling, cooking and eating quality decreased. Although appropriate application of K could improve rice milling, cooking and eating quality, it reduced appearance quality. The optimal milling, cooking and eating quality were obtained under N1K2, while the best appearance quality was obtained under N3K0. Overall, a combination of 135-210 kg ha-1 N and 115-137 kg ha-1 K application rates was recommended for achieving relatively higher yield and better quality in rice production.