Increase Rice Yield Research Articles

Assessing the environmental impacts of agrifood production

Agriculture, forestry, and other land use approximately contribute to 24 percent of 2010 global greenhouse gas (GHGs) emissions. This study, therefore, focuses on assessing the environmental impacts of jasmine rice production. The life cycle assessment method is used to find the hotspots that are of high environmental impacts. Face-to-face interviewing was conducted with 49 rice producers engaged in chemical, organic, and good agricultural practices in farming activities. The results show that most of the emissions were caused during the post-harvest management stage. Following eco-efficiency, organic jasmine rice production offers a reduction in the consumption of resources, reduced impact on the environment, and increased product value. Furthermore, our study shows that crop residue is a key to increase rice yields and decrease GHGs emissions. Our findings thus add to the limited literature on organic jasmine rice production and propose a recommendation for policymakers to promote sustainable agricultural practices to reduce the environmental impact.Graphic abstract

Effects of Organic Fertilizers on Cd Activity in Soil and Cd Accumulation in Rice in Three Paddy Soils from Guizhou Province.

A greenhouse pot experiment was conducted to investigate the effects of organic fertilizer application on Cd activity in soil and Cd accumulation in rice in paddy soils with different levels of contamination from varying Cd sources in Guizhou Province (the soil types are NJ, which is a soil with a high geological background of Cd; and QX and JZ, which are anthropogenic Cd-polluted soils). The application of organic fertilizer increased the content of organic matter in the soil and reduced the concentration of acetic acid-extractable Cd in QX and JZ paddy soils. Organic fertilizer increased rice yields and significantly decreased the Cd concentration in brown rice. In the QX and JZ soils, however, the concentration of Cd in brown rice exceeded the allowable maximum levels (MLs) of Cd in China. In contrast, the concentration of Cd in brown rice in NJ soil met the MLs of Cd. Additionally, the average daily dose and the health risk index of Cd in NJ soil were much lower than those in QX and JZ soils. The results indicate that organic fertilizer application is a promising and economic means to control Cd pollution in paddy soil. Moreover, risk assessment shows that the risk of exposure to Cd in the high geological background soil (NJ) was much lower than that in anthropogenically polluted soils (QX and JZ).

Genetic relationships and identification of core germplasm among rice photoperiod- and thermo-sensitive genic male sterile lines

BackgroundHarnessing heterosis is one of the major approaches to increase rice yield and has made a great contribution to food security. The identification and selection of outstanding parental genotypes especially among male sterile lines is a key step for exploiting heterosis. Two-line hybrid system is based on the discovery and application of photoperiod- and thermo-sensitive genic sensitive male sterile (PTGMS) materials. The development of wide-range of male sterile lines from a common gene pool leads to a narrower genetic diversity, which is vulnerable to biotic and abiotic stress. Hence, it is valuable to ascertain the genetic background of PTGMS lines and to understand their relationships in order to select and design a future breeding strategy.ResultsA collection of 118 male sterile rice lines and 13 conventional breeding lines from the major rice growing regions of China was evaluated and screened against the photosensitive (pms3) and temperature sensitive male sterility (tms5) genes. The total gene pool was divided into four major populations as P1 possessing the pms3, P2 possessing tms5, P3 possessing both pms3 and tms5 genes, and P4 containing conventional breeding lines without any male sterility allele. The high genetic purity was revealed by homozygous alleles in all populations. The population admixture, principle components and the phylogenetic analysis revealed the close relations of P2 and P3 with P4. The population differentiation analysis showed that P1 has the highest differentiation coefficient. The lines from P1 were observed as the ancestors of other three populations in a phylogenetic tree, while the lines in P2 and P3 showed a close genetic relation with conventional lines. A core collection of top 10% lines with maximum within and among populations genetic diversity was constructed for future research and breeding efforts.ConclusionThe low genetic diversity and close genetic relationship among PTGMS lines in P2, P3 and P4 populations suggest a selection sweep and they might result from a backcrossing with common ancestors including the pure lines of P1. The core collection from PTGMS panel updated with new diverse germplasm will serve best for further two-line hybrid breeding.

Screening of Rice Varieties based on Remodeling of Root Architecture Linked to Enhanced Phosphorus Transporters and Ethylene Signaling for Better Phosphorous Acquisition under Limiting Conditions

Root architectural modifications in response to altered nutrient level can be used as selection marker for better adapted rice varieties. In this study, we screened six local rice varieties commonly grown in Pakistan, using their unique root architecture and several molecular markers to identify best adapted local variety under phosphorus limiting conditions. Our data showed that rice variety with significant changes in its three-dimensional root architecture system (RSA) and enhanced expression of phosphorus transporters (OsPT2, OsPT4 and OsPT6) is the best variety to handle stress as compared to other varieties. Along with development of screening strategy/method, our data provided evidence that phosphorus starvation leads to upregulation of stress hormone ethylene, which regulates root elongation and root hair development therefore facilitating root architecture modification. We then further checked, how to mitigate or enhance phosphorus starvation responses by application of hormones exogenously, our results showed that ethylene application/treatment enhances phosphorus starvation responses, whereas cytokinin on the other hand reverses deficiency effects which implicates hormonal cross talk is key to modulate P-deficiency responses in rice. This study provides an easy and quick method of analysis of root architecture as physiological marker for rice screening and improve crop yield by selecting best adapted variety for P deficient soils. In future, detail study for understanding phytohormone mediated transcriptomic changes in response to nutrient deficiency and in correlation with physiological response will help to select better adapted varieties that will eventually result in increase of rice yield.

Influence of rice varieties, organic manure and water management on greenhouse gas emissions from paddy rice soils.

The study is focused on impact of manure application, rice varieties and water management on greenhouse gas (GHG) emissions from paddy rice soil in pot experiment. The objectives of this study were a) to assess the effect of different types of manure amendments and rice varieties on greenhouse gas emissions and b) to determine the optimum manure application rate to increase rice yield while mitigating GHG emissions under alternate wetting and drying irrigation in paddy rice production. The first pot experiment was conducted at the Department of Agronomy, Yezin Agricultural University, Myanmar, in the wet season from June to October 2016. Two different organic manures (compost and cow dung) and control (no manure), and two rice varieties; Manawthukha (135 days) and IR-50 (115 days), were tested. The results showed that cumulative CH4 emission from Manawthukha (1.084 g CH4 kg-1 soil) was significantly higher than that from IR-50 (0.683 g CH4 kg-1 soil) (P<0.0046) with yield increase (P<0.0164) because of the longer growth duration of the former. In contrast, higher cumulative nitrous oxide emissions were found for IR-50 (2.644 mg N2O kg-1 soil) than for Manawthukha (2.585 mg N2O kg-1 soil). However, IR-50 showed less global warming potential (GWP) than Manawthukha (P<0.0050). Although not significant, the numerically lowest CH4 and N2O emissions were observed in the cow dung manure treatment (0.808 g CH4 kg-1 soil, 2.135 mg N2O kg-1 soil) compared to those of the control and compost. To determine the effect of water management and organic manures on greenhouse gas emissions, second pot experiments were conducted in Madaya township during the dry and wet seasons from February to October 2017. Two water management practices {continuous flooding (CF) and alternate wetting and drying (AWD)} and four cow dung manure rates {(1) 0 (2) 2.5 t ha-1 (3) 5 t ha-1 (4) 7.5 t ha-1} were tested. The different cow dung manure rates did not significantly affect grain yield or greenhouse gas emissions in this experiment. Across the manure treatments, AWD irrigation significantly reduced CH4 emissions by 70% during the dry season and 66% during the wet season. Although a relative increase in N2O emissions under AWD was observed in both rice seasons, the global warming potential was significantly reduced in AWD compared to CF in both seasons (P<0.0002, P<0.0000) according to reduced emission in CH4. Therefore, AWD is the effective mitigation practice for reducing GWP without compromising rice yield while manure amendment had no significant effect on GHG emission from paddy rice field. Besides, AWD saved water about 10% in dry season and 19% in wet season.

Benefits of controlled-release/stable fertilizers plus biochar for rice grain yield and nitrogen utilization under alternating wet and dry irrigation

Identifying approaches to producing greater amounts of rice with higher water productivity (WP) and nitrogen use efficiency (NUE) is a major challenge for economical, environmentally friendly rice production. Despite the advantages of controlled-release N fertilizers, few studies have investigated their effects on rice agronomic performance, grain yield, NUE and WP under different irrigation regimes. In this study, a three-year field experiment was conducted in Zhejiang, South China, with two irrigation regimes (flood irrigation, FI; alternating wet and dry irrigation, AWD) and five N application methods (zero N, N0; the conventional N level, PUN100; 80 % of the conventional N level, PUN80; 80 % of the conventional N level applied as controlled-release N fertilizer and urea, plus biochar, CRFN80-BC; and 80 % of the conventional N level applied as stable compound N fertilizer and urea, plus biochar, SFN80-BC) using the indica hybrid rice cultivar Zhongzheyou 1. Compared with FI, AWD significantly increased rice yield, irrigation WP (WPi) and irrigation plus rainfall WP (WPi+r), and the values of these variables under CRFN80-BC and SFN80-BC were significantly higher than those under PUN80 and PUN100 (P < 0.05). Under AWD, compared to those under PUN100, rice grain yield, nitrogen recovery efficiency (NRE) and WPi+r under CRFN80-BC were 6.6 %, 28.5 % and 6.6 % higher, respectively, and 10.6 %, 44.6 %, and 10.6 % higher, respectively, under SFN80-BC on average over the three years. The higher rice yield was accompanied by higher crop growth rate (CGR) and grain “sink” capacity, as indicated by higher effective panicle and grain spikelet numbers and grain-filling rates. Under CRFN80-BC and SFN80-BC, AWD enhanced dry matter (DM) and N accumulation in the rice vegetative organs (functioning as “sources” for the grains) before the heading (HD) stage and the masses, ratios and contributions of DM and nonstructural carbohydrates (NSCs) transferred from the stems/sheaths and of N transferred from the leaves (as “flow”) from the rice HD to maturity (MA) stages compared with those in PUN80 and PUN100. These results indicate that maintaining the source-sink-flow balance of carbohydrates and N in rice helps increase rice grain yield and NUE; the significant and positive correlations among these parameters confirm this interpretation. Overall, the results suggest that under AWD, controlled-release/stable N fertilizers plus biochar can increase the grain yield, NUE and WP of rice.

Transport and transformation of water and nitrogen under different irrigation modes and urea application regimes in paddy fields

Nitrogen pollution from paddy fields is a main contributor to global non-point source (NPS) pollution and greatly increases the risks of surface water eutrophication and groundwater contamination. This study assesses the comprehensive transport and transformation of water and nitrogen (TTWN) for a 4-year irrigation and urea application in the paddy field using 6 water balance components and 12 nitrogen inputs and outputs. The results show that alternate wetting and drying (AWD) irrigation reduces water and nitrogen for irrigation, drainage, and leaching, but has a minor effect on rice evapotranspiration (ETc). Urea application and mineralization are the most important nitrogen inputs to the paddy field, accounting for 58.7–68.2% and 23.7–35.0% of nitrogen input, respectively. Rice plant uptake, ammonia volatilization (AV), and nitrification-denitrification account for 68.0–75.0%, 11.9–17.1%, and 5.1–9.3% of nitrogen output, respectively. Nitrogen leaching (3.5–11.5 kg·ha−1) is also large while the observed depth of leaching needs to be further investigated. Meanwhile, nitrogen drainage (0.72–1.11 kg·ha−1) is not as large as conventionally accepted. AWD affects the nitrogen accumulation and release of duckweed, which is one of the potential reasons for the increase in rice yields. In the course of four continuous rice seasons, the soil nitrogen content (SNC) of the 0–20 cm and 20–40 cm soil layers continued to decrease and increase, respectively, and the overall nitrogen content did not change significantly. Irrigation modes and fertilization splits may promote or inhibit AV, and it depended on the time when urea was applied. In addition, AWD and three fertilization splits significantly promote nitrification-denitrification and nitrogen uptake by rice. This study presents a theoretical basis for NPS pollution reduction and provides an important framework for establishing an accurate model of TTWN for paddy fields.

Long-term organic fertilizer substitution increases rice yield by improving soil properties and regulating soil bacteria

Applying organic and inorganic fertilizers together could sustainably increase crop yields. The effects of long-term organic fertilizer substitution on soil microbial community structure and function in paddy soil and on rice yield remain unclear. We evaluated changes in soil physicochemical factors, bacterial community structure responses, and the contributions of soil properties and bacterial communities to rice yield after 34 years of different fertilization treatments. A high ratio of organic fertilizer substitution significantly reduced soil acidification, improved soil nutrients, and increased soil urease and catalase activities (P < 0.05). Organic fertilizer substitution significantly changed the soil bacterial community structure and increased the relative abundance of beneficial bacteria, such as Bacilli and Flavobacteriales. The highest proportion of organic substitution treatment significantly enhanced carbon-related functional groups (P < 0.05), like aromatic hydrocarbon degradation and chitinolysis. The biomarkers enriched in the inorganic treatment and the organic fertilizer substitution treatments had similar correlated environmental factors but opposite correlation trends. Soil nutrient levels, especially total nutrients, explained most of the variation in annual rice yield, while bacteria indirectly affected annual yield through enzyme activities and nutrient levels. Our results provide evidence that soil nutrients and bacteria contribute to rice yield increase in long-term organic fertilizer substitution treatment.

Synergistic effects of bast fiber seedling film and nano-silicon fertilizer to increase the lodging resistance and yield of rice

The use of bast fiber film can improve rice seedling quality, and nano-silicon fertilizer can increase rice yields. This study aimed to compare the effects of using bast fiber film, nano-silicon fertilizer, and both treatments on rice yield and lodging resistance. A 2-year field experiment was conducted in 2017 and 2018, in Liaoning, China. The experiment comprised a control (no-bast fiber film, no nano-silicon fertilizer; CK), and three treatments: seedlings cultivated with bast film (FM), single nano-silicon fertilization (SF), and bast fiber film seedlings + nano-silicon fertilization (FM + SF). The japonica rice (Oryza sativa L.) cultivar Liaojing 371 was used. Compared with the plants in CK, those in the FM treatment showed greater average root diameter, root volume and root dry weight. The SF treatment increased the single stem flexural strength, increased the contents of silicon, lignin, and cellulose in the rice plant stalk, and reduced the lodging index, thereby increasing lodging resistance. The SF treatment resulted in increased leaf chlorophyll content at late growth stage and a higher net photosynthetic rate, which increased plant dry matter accumulation. In the FM + SF treatment, plant growth was enhanced during the whole growth period, which resulted in an increased number of effective panicles and an increased grain yield. The results show that the combination of FM and SF synergistically improves rice lodging resistance and grain yield. This low-cost, high-efficiency system is of great significance for improving the stability and lodging resistance of rice plants, thereby increasing yields.

Effects of nitrogen-enriched biochar on rice growth and yield, iron dynamics, and soil carbon storage and emissions: A tool to improve sustainable rice cultivation

Biochar is often applied to paddy soils as a soil improver, as it retains nutrients and increases C sequestration; as such, it is a tool in the move towards C-neutral agriculture. Nitrogen (N) fertilizers have been excessively applied to rice paddies, particularly in small farms in China, because N is the major limiting factor for rice production. In paddy soils, dynamic changes in iron (Fe) continuously affect soil emissions of methane (CH4) and carbon dioxide (CO2); however, the links between Fe dynamics and greenhouse gas emissions, dissolved organic carbon (DOC), and rice yields following application of biochar remain unclear. The aims of this study were to examine the effects of two rates of nitrogen (N)-enriched biochar (4 and 8 t ha−1 y−1) on paddy soil C emissions and storage, rice yields, and Fe dynamics in subtropical early and late rice growing seasons. Field application of N-enriched biochar at 4 and 8 t ha−1 increased C emissions in early and late rice, whereas application at 4 t ha−1 significantly increased rice yields. The results of a culture experiment and a field experiment showed that the application of N-enriched biochar increased soil Fe2+concentration. There were positive correlations between Fe2+concentrations and soil CO2, CH4, and total C emissions, and with soil DOC concentrations. On the other way around, these correlations were negative for soil Fe3+concentrations. In the soil culture experiment, under the exclusion of plant growth, N-enriched biochar reduced cumulative soil emissions of CH4 and CO2. We conclude that moderate inputs of N-rich biochar (4 t ha−1) increase rice crop yield and biomass, and soil DOC concentrations, while moderating soil cumulative C emissions, in part, by the impacts of biochar on soil Fe dynamics. We suggest that water management strategies, such as dry-wet cycles, should be employed in rice cultivation to increase Fe2+ oxidation for the inhibition of soil CH4 and CO2 production. Overall, we showed that application of 4 t ha−1 of N-enriched biochar may represent a potential tool to improve sustainable food production and security, while minimizing negative environmental impacts.

Alternate wetting and drying enhanced the yield of a triple-cropping rice paddy of the Mekong Delta

ABSTRACT In the Mekong Delta, triple rice cropping is widely spread. The rice cultivation is characterized by a short cropping period and nearly year-round flooding. Putting the soil under an oxidative condition through changing the water regimes during cropping periods might have a potential to increase the rice yield. To test this potential, an experiment was conducted at a typical triple-cropping farmer’s alluvial paddy in a central area of the delta for five years, 15 consecutive cropping seasons. We adopted an intermittent irrigation technique known as alternate wetting and drying (AWD). Under AWD, we irrigated to a depth of 5 cm above the soil surface only when the field water level dropped to 15 cm below the soil surface, with some exceptions. As a control, we prepared a treatment under which the paddy was continuously flooded (CF) except 2 weeks before expected harvest. We also prepared three straw treatments: all raw straw return, all straw-ash return, and no straw return to the paddy. For other field management, we adopted locally conventional methods. Results show that the straw treatment effects on the rice yield were not significant. For water treatments, the soil redox potential under AWD remained higher, in most cases, than that under CF; and the rough rice yield, harvest index, and percentage of ripened grains under AWD respectively became 8.9%, 4.4%, and 3.5% higher (p < 0.01) than those under CF, with lower N contents in rice grains and 43% less irrigation water use. The increase in rice yield by AWD was found with an increase in harvest index and a decrease in aboveground biomass and nitrogen content, indicating that it was due to the promotion of nutrient translocation in rice by AWD. The effect of AWD was enhanced particularly in the winter–spring cropping season, during which the nighttime temperature was the lowest. This piece of evidence that the rice yield of the delta can be increased simply by introducing AWD has the potential to encourage farmers to take voluntary actions that will also lead to a reduction in methane emission from rice paddies.

Arsenic and cadmium load in rice tissues cultivated in calcium enriched biochar amended paddy soil

Arsenic (As) and cadmium (Cd) are unnecessary metal(loids) toxic at high concentration to plants and humans, hence lessening their rice grain accumulation is crucial for food security and human healthiness. Charred eggshell (EB), corncob biochar (CB), and eggshell-corncob biochar (ECB) were produced and amended to As and Cd co-polluted paddy soil at 1% and 2% application rates to alleviate the metal(loids) contents in rice grains using pot experiments. All the amendments increased paddy yields at 1%, while EB at 2% significantly reduced the yields compared to untreated control. The resulting yield loss in 2%EB was from the combined effects of its high CaCO3 supplementation, and the increment of rhizosphere soil pH which could insolubilize plant nutrients. The amendments were inefficient in decreasing rice grain As (AsGrain), but all the treatments significantly reduced the rice grain Cd (CdGrain) at both 1% (44.4–77.1%) and 2% (79.8–91.5%) application rates compared to that of control. Regression analysis for contribution weights of control factors revealed that rhizosphere soil Eh and pH were vital influential factors regulating the AsGrain, whereas porewater Cd was main factor controlling CdGrain accumulation. These investigations indicated that the Ca-enriched eggshell-corncob biochar even at high application rate (i.e., 2%ECB) could be a potential tactic for grain accumulation remediation of the cationic pollutant (i.e., Cd) from the paddy soil to rice grain scheme with concurrent increase in rice yields.

Modelling rice yield from biochar-inorganic fertilizer amended fields

Rice yield is vulnerable to climatic changes. High concentrations of atmospheric CO 2 is noted to increase yield by improving upon nutrient uptake and water use efficiency of plants. Temperature variations also affect plant growth and eventually crop yield as it has an effect on respiration and photosynthesis. Soil fertility is an important parameter affecting the production of most crops and rice is not an exception. The cost as well as the environmental consequences of using inorganic fertilizers makes it necessary to use other soil amendments such as biochar. Field experiments are often time consuming and involves a lot of drudgery. This research was therefore conducted to model the quantities of biochar-inorganic fertilizer combinations that give optimum yields of rice and assess the effect of changes in climatic parameters on the yield of rice. CERES-Rice model was used to simulate the yield of rice using different combinations of biochar-inorganic fertilizer as soil amendments. Effects of changes in climatic parameters on the yield of rice were also simulated. The yield of rice from the simulations were sensitive to the soil amendments especially the biochar. Treatments with no biochar had relatively low rice yields compared with those with biochar. The average simulated yields were 1.5 t/ha, 5.6 t/ha and 5.5 t/ha for treatments with 0 t/ha, 20 t/ha and 30 t/ha of biochar respectively. Increasing or decreasing rainfall resulted in reduction in the yield of rice. Increasing carbon dioxide concentrations generally led to an increase in the simulated yields of rice. On the other hand, decreasing the carbon dioxide concentrations resulted in decreased simulated rice yields. It was observed that increasing temperature resulted in a reduction in rice yield for the various treatments. The reduction in the yield of rice ranged from 7.64% to 34 .67%. • Biochar-inorganic fertilizer improve upon simulated rice yield. • Increase in temperature results in a decrease in simulated rice yield. • Increase in carbon dioxide results in an increase in simulated rice yield. • An increase in solar radiation results in an increase in rice yield.

Influence of Rhizobacteria on Soil Ion Concentration under Paddy Cultivation

Sustainable agriculture requires nutrient management options that can increase crop yields that are profitable for N nutrient availability and are environmentally friendly. However, N nutrient is dynamic and easy to lose, and excessive use of chemical N fertilizers has a negative impact on the environment. Biofertilizer by rhizobacteria is an effective way to maintain a reliable N-supply for rice growth. This study investigates the effect of a different combination of rhizobacterial fertilizers on nitrogen ion concentration in the soil and total rice production. The field experiment was conducted in two seasons. There were three treatments, including PGPR with 25% CF, PGPR with 50% CF, and 100% CF. The soil sample was taken from each treatment in six growth stages of rice i.e. 15, 36, 50, 72, 100, and 118 days after transplanting. Soil chemicals NH4+ and NO3- were analyzed by Ion Chromatography. The results showed that the uniformity of NH4+ and NO3- in the soil were the highest in fertilizer application with PGPR. The application of PGPR with 50% CF confirms that it can increase rice yields by 25.5% and 12.9%, respectively. The application of rhizobacteria can reduce the use of chemical fertilizers.

The Effects of different agricultural management measures on CH4 emission from paddy fields in southwest Shandong Province

The field experiments were conducted on garlic stubble rice fields in southwestern Shandong Province. The experimental program was designed and the influence of different agricultural management measures on CH4 emission flux and the factors affecting CH4 emission were analyzed. The results show that although temperature affects CH4 emissions from paddy fields, it is not the only influencing factor. Compared with submerged irrigation+no basal fertilizer method, the CH4 emission flux of intermittent irrigation+basal fertilizer method is significantly larger; under the same submerged irrigation method, applying basal fertilizer is beneficial to CH4 emission. In the submerged irrigation+basal fertilizer mode, tillering fertilizer is more conducive to methane emission than panicle fertilizer. The use of intermittent irrigation method to apply appropriate amount of base fertilizer and tiller fertilizer can effectively control the increase of rice yield and the reduction of CH4 emissions in the rice field. The above operations can increase agricultural production and income and reduce greenhouse gas emissions.

Effect of Digestate and Straw Combined Application on Maintaining Rice Production and Paddy Environment.

Few studies have focused on the combined application of digestate and straw and its feasibility in rice production. Therefore, we conducted a two-year field experiment, including six treatments: without nutrients and straw (Control), digestate (D), digestate + fertilizer (DF), digestate + straw (DS), digestate + fertilizer + straw (DFS) and conventional fertilizer + straw (CS), to clarify the responses of rice growth and paddy soil nutrients to different straw and fertilizer combinations. Our results showed that digestate and straw combined application (i.e., treatment DFS) increased rice yield by 2.71 t ha−1 compared with the Control, and digestate combined with straw addition could distribute more nitrogen (N) to rice grains. Our results also showed that the straw decomposition rate at 0 cm depth under DS was 5% to 102% higher than that under CS. Activities of catalase, urease, sucrase and phosphatase at maturity under DS were all higher than that under both Control and CS. In addition, soil organic matter (SOM) and total nitrogen (TN) under DS and DFS were 20~26% and 11~12% higher than that under B and DF respectively, suggesting straw addition could benefit paddy soil quality. Moreover, coupling straw and digestate would contribute to decrease the N content in soil surface water. Overall, our results demonstrated that digestate and straw combined application could maintain rice production and have potential positive paddy environmental effects.

Reasonable Nitrogen Fertilizer Management Improves Rice Yield and Quality under a Rapeseed/Wheat–Rice Rotation System

To determine the influence of N fertilizer management on rice yield and rice quality under diversified rotations and establish a high-yield, high-quality, and environmentally friendly diversified planting technology, a rapeseed/wheat–rice rotation system for 2 successive years was implemented. In those rotation systems, a conventional N rate (Nc; 180 kg/hm2 N in rape season, 150 kg/hm2 N in wheat season) and a reduced N rate (Nr; 150 kg/hm2 N in rape season, 120 kg/hm2 N in wheat season) were applied. Based on an application rate of 150 kg/hm2 N in the rice season, three N management models were applied, in which the application ratio of base:tiller:panicle fertilizer was 20%:20%:60% in treatment M1, 30%:30%:40% in treatment M2, and 40%:40%:20% in treatment M3. Zero N was used as the control (M0). The results showed that, under Nc and Nr in the rape season, M3 management produced an increase in rice yield. The average rice yields in 2018 and 2019 were 9.41 t/hm2 and 9.54 t/hm2, respectively. An increase in rice peak viscosity, hot viscosity, break disintegration, and chalkiness was achieved. Under Nc and Nr in the wheat season, the panicle fertilizer of 40%:40%:20% in rice season produced a higher rice yield. The average yield was 9.45 t/hm2 and 9.19 t/hm2, respectively, and an increase in rice peak viscosity, hot viscosity, and break disintegration was produced. Reduced N for rapeseed and the panicle fertilizer of 40%:40%:20% in rice season under a rapeseed–rice rotation system can be recommended to stabilize yield and ensure high-quality rice production and environmentally friendly rapeseed–rice rotation systems in southern China.

Nitrogen/potassium interactions increase rice yield by improving canopy performance

AbstractThe interactions between nitrogen (N) and potassium (K) are important determinants of rice yield, but the mechanisms involved remain poorly understood. For example, N/K interactions may influence light utilization and N distribution in the canopy. Field experiments were therefore performed to resolve this issue, using factorial combination of N and K. The interaction between N and K had a significant effect on the grain yield, N uptake, and the NUE of grain production (NUEg), and biomass production (NUEb). The application of either N or K alone resulted in lower yields than the combined application of these nutrients. The combined application of N and K increased rice yields by 54.5% in 2018 and by 76.1% in 2019, compared with N0K0. Similarly, N uptake, NUEg, and NUEb were higher when N was supplied with K than with N application alone. The higher grain yields, N uptake rates, and NUEs observed with the combined N and K treatment were attributed to the following: (1) a higher leaf area index that resulted in better light interception; (2) improved the coordination of light and N distribution within the canopy. Evidence for improved light use by photosynthesis is provided by the observed lower light extinction coefficient (KL), the higher specific leaf N in the top leaves (SLNo), higher extinction coefficients for effective leaf N (KN) and KN/KL values. We conclude that the interactions between N and K support higher yields by improving canopy performance even at lower N rates.

Soil microbial response to silicate fertilization reduces bioavailable arsenic in contaminated paddies

Rice grown in arsenic (As)-contaminated soils will have an elevated As concentration in the edible parts and lower yield due to the stressful growing environment. Silicon fertilizer is a soil amendment that can prevent As bioaccumulation and increase rice yield. This may be due to chemical interactions between silicon and As, but we hypothesized that silicon fertilization would improve soil microbial functions that control the bioavailable As concentration and improve the growing environment for rice in As-contaminated agroecosystems. We tested the hypothesis on two geographically different rice varieties (Indica and Japonica) grown on As spiked soils. Rice grown in pots amended with slag-based silicon fertilizer (silicate fertilizer) at a rate of 2 Mg ha−1 had a significantly lower As concentration in the grain, with 28% less As in the grain of Indica rice and 30% less As in the Japonica rice grain. The rice grain yield was 20–22% greater in these rice varieties. There are several reasons that As uptake declined in the rice grain, including: (i) a reduction in As bioavailability, likely because As was absorbed to amorphous and crystalline iron oxides in the soil and on root Fe-plaque, (ii) an increase in As resistant and arsenite-oxidizing bacteria that likely contribute to the natural attenuation of As in soil, and (iii) an increase in the pore-water silicon concentration that competitively inhibited As uptake by plants. Adding silicate fertilizer improved the general soil fertility by increasing the abundance of microbial functional communities involved in nutrient (carbon, nitrogen, and phosphorus) cycling, nitrogen and carbon fixation, methane consumption, and heavy metals/metalloid detoxification, while decreasing the number of microorganisms involved in methane and nitrous oxide production. We conclude that silicate fertilizer amendments stimulate soil microbial functions that are beneficial for rice growth while controlling As bioavailability, and thus are a potential solution to allow rice production in As-contaminated paddy soils.

QTGW12a, a naturally varying QTL, regulates grain weight in rice

Key messageA stable QTL associated with rice grain type with a large effect value was found in multiple environments, and its candidate genes were verified by genetic transformation.Rice (Oryza sativa L.) grain size is critical to both yield and appearance quality. Therefore, the discovery and identification of rice grain size genes can provide pathways for the cultivation of high-yielding varieties. In the present work, 45,607 SNP markers were used to construct a high-density genetic map of rice recombinant inbred lines, and hence a total of 14 quantitative trait loci (QTLs) were detected based on the phenotypic data of grain weight, grain length and grain width under four different environments. qTGW12a and qGL12 are newly detected QTLs related to grain weight, and are located between 22.43 Mb and 22.45 Mb on chromosome 12. Gene annotation shows that the QTL region contains the LOC_Os12g36660 annotated gene, which encodes the multidrug and toxic compound extrusion (MATE) transporter. Mutations in exons and the splice site were responsible for the changes in grain type and weight. Gene knockout experiments were used to verify these results. Hence, these results provide a basis for the cloning of qTGW12a. This discovery provides new insights for studying the genetic mechanism of rice grain morphology, and reveals a promising gene to ultimately increase rice yield.