Paddy Rice Yield Research Articles

Mapping Ratoon Rice Fields Based on SAR Time Series and Phenology Data in Cloudy Regions

Ratoon rice (RR) has emerged as an active adaptation to climate uncertainty, stabilizing total paddy rice yield and effectively reducing agriculture-related ecological environmental issues. However, identifying key remote sensing parameters for RR under cloudy and foggy conditions is challenging, and existing RR monitoring methods in these regions face significant uncertainties. Here, given the sensitivity of synthetic aperture radar (SAR) backscattering signals to the crop phenological period, this paper introduces a threshold model utilizing Sentinel-1A SAR data and phenological information for mapping RR. The Yongchuan District of Chongqing, which is often cloudy and foggy, was selected as a specific study region where VH-polarized backscatter coefficients of Sentinel-1 images were obtained at 10 m spatial resolution in 2020. Based on the proposed threshold model, the RR extraction overall accuracy was up to 90.24%, F1 score was 0.92, and Kappa coefficient was 0.80. Further analysis showed that the extracted RR boundaries exhibited high consistency with true Sentinel-2 remote sensing images and the RR extracted area was in good agreement with the actual planted area situation. This threshold model demonstrated good applicability in the studied cloudy and foggy region, and successfully distinguished RR from other paddy rice types. The methodological framework established in this study provides a basis for extensive application in China and other significant RR-producing regions globally.

A Bayesian approach to assessing uncertainty in the effect of fertilization strategies on paddy rice yield via multiple on-farm experiments

ABSTRACT The surge in global agricultural input prices, particularly for nitrogen (N) fertilizers, has presented challenges for farmers facing stagnant crop prices and rising production costs. This study explored a system designed to sustain or enhance farmers’ income while reducing production costs, with a specific focus on implementing practices that involve cultivating crops with lower rates of fertilizer than conventional rates, particularly in smaller land settings, through on-farm experimentation (OFE). OFE was conducted over three years across 11 fields in Gifu, Japan, utilizing a strip trial design to investigate the effect of fertilizer input rates on rice yield. To collect yield data, unmanned aerial vehicle (UAV)-mounted multispectral cameras were deployed. A Gaussian process model was used to address the impact of fertilizer input rates on yield while accounting for spatial yield variation. The study further assessed the number of field trials achieving positive profits at certain probability levels by integrating outcomes from multiple OFEs. The results highlighted little rice yield response to fertilizer input in most of the fields, while several fields showed significant positive yield responses. Notably, the use of lower fertilizer input rates in certain fields proved to be more profitable whereas higher fertilizer input rates were less profitable in most fields. The results further emphasized the economic viability of lower rates, especially when fertilizer prices are high, thus contributing valuable insights for sustainable and profitable rice production in Japanese cultivation.

Long-Term Straw Incorporation under Controlled Irrigation Improves Soil Quality of Paddy Field and Rice Yield in Northeast China.

Soil quality is an indicator of the ability to ensure ecological security and sustainable soil usage. The effects of long-term straw incorporation and different irrigation regimes on the yield and soil quality of paddy fields in cold regions remain unclear. This study established four treatments: controlled irrigation + continuous straw incorporation for 3 years (C3), controlled irrigation + continuous straw incorporation for 7 years (C7), flooded irrigation + continuous straw incorporation for 3 years (F3), and flooded irrigation + continuous straw incorporation for 7 years (F7). Analysis was conducted on the impact of various irrigation regimes and straw incorporation years on the physicochemical characteristics and quality of the soil. The soil quality index (SQI) for rice fields was computed using separate datasets for each treatment. The soil nitrate nitrogen, available phosphorus, soil organic carbon, and soil organic matter contents of the C7 were 93.51%, 5.80%, 8.90%, and 8.26% higher compared to C3, respectively. In addition, the yield of the C7 treatment was 5.18%, 4.89%, and 10.32% higher than those of F3, C3, and F7, respectively. The validity of the minimum data set (MDS) was verified by correlation, Ef and ER, which indicated that the MDS of all treatments were able to provide a valid evaluation of soil quality. The MDS based SQI of C7 was 11.05%, 11.97%, and 27.71% higher than that of F3, C3, and F7, respectively. Overall, long-term straw incorporation combined with controlled irrigation increases yield and soil quality in paddy fields in cold regions. This study provides a thorough assessment of soil quality concerning irrigation regimes and straw incorporation years to preserve food security and the sustainability of agricultural output. Additionally, it offers a basis for soil quality diagnosis of paddy fields in the Northeast China.

Integrated Effects of Straw Incorporation and N Application on Rice Yield and Greenhouse Gas Emissions in Three Rice-Based Cropping Systems

Crop straw and N fertilizer applications impact paddy rice yield and greenhouse gas (GHG) emissions. However, their interactive effects have not been well documented. This study investigated the effects of straw (S), no straw incorporation (NS), and three levels of N fertilization rates (N0, N1, and N2) on single rice (SR), double rice (DR), and rice-wheat (RW) cropping systems. Straw incorporation significantly increased total CH4 emissions by 118.6%, 8.0%, and 79.0% in the SR, DR, and RW, respectively, compared to the NS. The total GHG emissions in DR are significantly 72.6% and 83.5% higher than those in RW and SR, respectively. Compared to NS, straw incorporation significantly increased yield-scaled emissions by 27.8%, 15.0%, and 89.0% in SR, DR, and RW, respectively. Straw with N application significantly increased average rice yield over N1 and N2 by 39.4%, 50.0%, and 6.7% in SR, DR, and RW, respectively. There was a significant correlation between methyl coenzyme M reductase (mcrA) and CH4 emissions in rSR = 0.87 (p < 0.05) and rRW = 0.85 (p < 0.05), except in rDR = 0.06 (p > 0.05). This study scientifically supports straw incorporation combined with a moderate N application rate in rice-based cropping systems to maintain high rice yields and mitigate GHG emissions.

Fertilization enhances rice productivity by promoting phosphorus uptake and altering soil microbiota

Fertilization can enhance crop yield and improve soil health. However, its effects on nutrient uptake, soil microbiota, and rice yield remain unclear. Herein, we designed a double-cropping system with different fertilization treatments to determine their contributions to paddy soil agroecosystem and rice yield. Soil samples were collected before planting the early rice, after harvesting early rice, and after harvesting the late rice. Soil physicochemical properties, and rice yield, and rice nutrient (total nitrogen, phosphorus, and potassium contents) were determined. Variation of soil microbiota were also determined by high-throughput sequencing. We found that soil potassium content significantly improved during the planting process (P < 0.05), while rice phosphorus displayed significant variation under fertilization (P < 0.05). Notably, late rice yield was significantly higher than early rice yield (P < 0.001) after fertilization treatment. Furthermore, rice yield was positively correlated with available soil phosphorus (P < 0.05), indicating that fertilization promoted phosphorus uptake. Organic fertilizer altered the soil microbiota and increased Chloroflexi phyla abundance, while organic fertilizer combined with a compound microbial agent increased the diversity of soil microbial communities. A partial least squares path model revealed that fertilizer treatment directly positively affected rice yield by influencing phosphorus uptake and Shannon index (P < 0.01). Collectively, this study demonstrates that organic fertilization with compound microbial agents can stabilize soil nutrients, increase soil microbial diversity, and improve rice yield, thereby offering a guide for enhancing fertilizer utilization and improving agroecosystems.

Effects of long-term different-scale rice-duck farming on the growth and yield of paddy rice.

To maintain rice production and increase revenue, rice-duck (RD) farming is a contemporary ecological cycle technology that has been widely used in Asia. However, due to the clustering activity of duck flocks, the consequences of long-term RD farming on rice growth at different scales are still unknown. Here, we studied RD farming using several different treatments (CK: conventional rice farming; RD1: 667 m2 ; RD2: 2000 m2 ; and RD3: 3333 m2 ). The results demonstrated that the maximum tillers, effective spikes, dry matter accumulation, and lodging index of rice under RD farming were significantly decreased by 17.9%, 9.8%, 14.8%, and 17.8%, respectively, which ultimately caused a significant decrease in yield of 10.6%. However, RD farming significantly increased root oxidation activity and the ear-bearing tiller rate of rice by 25.5% and 11.1%, respectively, and improved yield stability. For different scales of RD farming, the lodging resistance index of RD1 was significantly lower than that of RD2 and RD3 by 10.0% and 15.2%, respectively, whereas the root oxidation activity and dry matter accumulation of RD2 were significantly higher than those of RD1 and RD3 by 11.1%, 4.7%, 8.6%, and 5.1%, respectively. For rice yield, there was no significant difference among the different scales. This long-term experiment helped elucidate the complicated effects of RD farming at different scales on the growth and yield of rice. It is also critical to consider the economic advantages of different scales of RD farming to assess the impact of this system more thoroughly. © 2023 Society of Chemical Industry.

EFFECTIVENESS OF LIQUID NPKSi AND N, P, K FERTILIZER ON NUTRIENT UPTAKE AND YIELD OF RICE PADDY IN ULTISOLS

Agricultural intensification and extensification need to be done to increase rice productivity. Silicon (Si) is a non-essential nutrient that plays a positive role in growth and yield. The application of liquid NPKSi fertilizer increases nutrient availability, particularly on Ultisols. The purpose of this study was to assess the effectiveness of liquid NPKSi fertilizer and straight fertilizer on nutrient uptake and yield of paddy rice on Ultisols. This research was conducted from September 2023 to June 2024 at the Soil Fertility and Plant Nutrition Experimental Farm and the Soil Chemistry and Plant Nutrition Laboratory. This study used a Randomized Block Design (RBD), which consisted of nine treatments and three replications. The treatments included control, recommended N, P, and K fertilizers, and various doses of liquid NPKSi fertilizer and straight fertilizer. The results showed that liquid NPKSi fertilizer and straight fertilizer were effective in increasing nutrient uptake and yield of paddy rice on Ultisols. The highest fertilizer effectiveness was found in the treatment of 6 L.ha-1 liquid NPKSi fertilizer and straight fertilizer (175 kg.ha-1 Urea, 37.5 kg.ha-1 SP-36, and 25 kg.ha-1KCl) with an RAE value of 218%.

Reasonable dry cultivation methods can balance yield and grain quality of rice

Reducing the water consumption of rice production in China without affecting grain yield and quality is an important challenge. The purpose of this study was to explore whether different dry cultivation methods could improve rice quality while balancing yield to maintain sustainable rice production. A japonica upland rice cultivar and a japonica paddy rice cultivar were cultivated in the field with three cultivation methods: plastic film mulching dry cultivation (PFMC), bare dry cultivation (BC), and continuous flooding cultivation (CF) as control. There was no significant difference in upland rice yield between PFMC and BC, and there was also no significant difference in paddy rice yield between PFMC and CF. Compared with CF, the two varieties yield decreased significantly with BC. Dry cultivation, especially PFMC, could decrease active filling period, chalky rice rate, chalkiness, amylose content, gel consistency, breakdown viscosity, ratio of glutelin to prolamin, leaf senescence, and increase water use efficiency, protein components content, setback viscosity, grain Q-enzyme activity and average filling rate. Compared with paddy rice, upland rice had lower yield, shorter active filling period, lower chalkiness grain rate and gel consistency, and higher amylose content, breakdown viscosity, protein components content and average filling rate. Grain Q-enzyme activity and grain filling parameters were closely related to rice quality. Reasonable dry cultivation methods could balance yield and quality, especially improve the nutritional and appearance quality of rice.

Effect of Elevated Air Temperature on the Growth and Yield of Paddy Rice

Rice is one of the major food crops, particularly in Asia. However, it is vulnerable to high temperature and has high yield fluctuations. Monitoring crop growth and physiological responses to high temperatures can help us better understand the agricultural impacts of global warming. The aim of this study is to monitor growth, development, and physiological responses to high temperature conditions on paddy rice and to assess their combined effects on yield. In this study, changes to growth, maturity, and senescence in paddy rice throughout the growing season were identified under elevated air temperature conditions created by a temperature gradient field chamber (TGFC). That facility provides a gradient from the ambient air temperature (AT) to 3 °C above AT (AT + 3 °C). To represent crop physiology and productivity, we measured the plant height, chlorophyll, normalized difference vegetation index (NDVI), and maximum photosynthetic rate (Amax) to assess growth and physiological processes, and heat stress effects on four yield measurements were assessed using the heating degree day index. Rice height increased more rapidly in the AT + 3 °C treatment from the early growth stage to heading, while SPAD and NDVI decreased more rapidly at AT after heading. The Amax of AT and AT + 3 °C was not significantly different in the tillering stage. However, it was higher at AT in the booting stage but higher at AT + 3 °C in the grain filling stage. These results indicate that paddy rice was not affected by heat stress at the tillering stage, but a cumulative effect emerged by the booting stage. Further, photosynthetic capacity was maintained much later into the grain filling stage at AT + 3 °C. These results will be useful for understanding the growth and physiological responses of paddy rice to global warming.

Performance evaluation of the ORYZA_V3 model for rice growth and organ nitrogen content

AbstractThe ORYZA version 3 (ORYZA_V3) model is commonly used for simulating paddy rice (Oryza sativa L.) growth. However, few studies have investigated the performance of the ORYZA_V3 model for predicting in‐season crop growth variables, especially for the nitrogen (N) translocation process among paddy rice organs in the whole growing season, that is, from sowing to harvest stages. This study examines the prediction accuracy of seven paddy rice growth variables based on one cropping season of field experiment. The results show that (1) the ORYZA_V3 model generates accurate prediction of paddy rice leaf area index, above‐ground biomass, and yield, where root mean square errors (RMSEs) are 0.98–1.11 ha/ha, 2360.5–3028.7 kg/ha, and 492.9–515.2 kg/ha, respectively, coefficient of determination (R2) ranges from 0.76 to 1.00, and index of agreement (D‐index) ranges from 0.50 to 0.98. (2) The prediction accuracy of paddy rice leaf and stem N contents is acceptable, where RMSE ranges from 0.0017 to 0.0041 kg/kg, R2 ranges from 0.82 to 0.96, and D‐index ranges from 0.93 to 0.98. (3) The ORYZA_V3 model cannot generate accurate prediction of rice root and panicle N contents, where RMSE ranges from 0.0007 to 0.0022 kg/kg, R2 ranges from 0.01 to 0.20, and D‐index ranges from 0.17 to 0.65. The structural uncertainty in the N translocation module may be a major reason for the unacceptable crop model prediction. This study demonstrated the substantial potential of the ORYZA_V3 model for simulating and understanding paddy rice growth and organ N translocation.

Quality attributes of paddy rice as affected by frozen storage

ABSTRACT After harvest, paddy rice may encounter frozen conditions during the storage and transportation periods. However, the effect of frozen storage on quality of paddy rice remains unclear. In this research, two moisture contents of paddy rice (13.5% and 15.1%) were stored at two frozen temperatures (−18°C and −30°C) for two months and then evaluated for quality attributes, including germination rate, peroxidase and polyphenol oxidase activities, fat acidity, milling quality, pasting property, cooking property, and texture of the cooked rice. The results showed that the frozen storage generally decreased the germination rate, activities of peroxidase and polyphenol oxidase, husked rice yield, head rice yield of paddy rice, reduced the water uptake ratio and volume expansion rate of milled rice during cooking, and lowered the hardness of cooked rice. At frozen condition, the decrease of temperature and the increase of moisture content led to a more pronounced reduction in germination rate and peroxidase activity. Frozen treatment of paddy rice did not significantly affect the pasting temperature of milled rice flour, but decreased the peak viscosity. Fat acidity of paddy rice slightly increased after frozen storage.

Assessing combined effects of biochar concentrations and different fertilizer applications on physicochemical properties of a sandy loamy soil

Biochar application in the soil is a major strategy for modifying or improving its physicochemical properties, while soil fertility can be boosted by fertilizer application. The process of soil amendment was explored to investigate the impact of combined biochar and fertilizer treatments on soil properties and yield of New Rice for Africa (NERICA 2) upland rice variety. A Randomized Complete Block Design experiment was conducted using three different fertilizer types, three different biochar concentrations, and two sets of control each, with zero biochar and zero fertilizer. The biochar levels were 0 t/ha, 5 t/ha, 10 t/ha, and 15 t/ha, while the fertilizer types were zero fertilizer, liquid organic fertilizer (LOF), solid fertilizer (NPK), and farmyard poultry manure (PM). A drip irrigation system with the completed layout captured the entire set-up, while soil properties were measured before soil treatment, post-season 1, and post-season 2. A significant increase in particle density from 3 3 3 3 2.51 g/cm3 to 2.56 g/cm3 was recorded while bulk density decreased from 1.42 g/cm3 to 1.41 g/cm3 , and soil textural classification remained relatively unchanged. Organic carbon, organic matter, nitrogen, phosphorus, potassium, cation exchange capacity, and base saturation increased from their respective pre-treatment values. Also, soil pH improved significantly from 6.38 to 6.37. There was a better improvement in soil properties, which resulted in increased paddy rice yield with an average value of 6.36 t/ha obtained using NPK with a biochar concentration of 15 t/ha (NPKB15) treatment. This is an equivalent of approximately 400% increase in yield compared to the zero fertilizer and zero biochar (FOBO) treatment yield of 1.14 t/ha. NPK fertilizer at a biochar concentration of 15 t/ha, gave the best result in the soil's physical and chemical properties and is recommended for rice production.

Effects of Sowing Methods on Paddy Rice Yields and Milled Rice Quality in Rainfed Lowland Rice in Wet Savannah, Togo

Identifying the socio-economic constraints of seeding technologies uptake and analyzing the yields, milled quality and growers’ income under various seeding methods are a strategy for sustainable rainfed lowland rice. A survey and an on-farm experiment were carried out at five locations with a random sample of 50 farmers grouped in five of the fourteen partner cooperatives of ESOP-Pagouda. The survey focused on socio-economic data collection. The experiment, replicated at five locations, involved three treatments: broadcast seeding, direct seeding, and transplanting. The paddy rice yields and milled rice quality were analyzed using R software version 4.1.3, and arithmetic means discriminated at the 5% by the Duncan test. The profitability indicators, such as the Gross Margin (GM) and the Benefit/Cost Ratio (BCR), were calculated. The results showed that 14% of farmers adopted rice transplanting method. The transplanting method increased rice yield (3.3 t/ha) compared to direct seeding (2.8 t/ha) and broadcast seeding (2.2 t/ha). The milled long grain rate (56%) was significantly higher than those under both seeding methods. Additionally, the transplanting method improved the gross margin (1,146 $USD/ha) compared to 663 $USD/ha and 431 $USD/ha for direct and broadcast seeding, respectively. The benefit/cost ratio 1.5 for transplanting was almost double from that of both seeding methods. Despite its high demand for labor and agricultural inputs, the transplanting method provided the highest paddy rice yields and milled rice quality to improve farmers’ income.

Evaluasi Status Hara dan Rekomendasi Pemupukan Padi Sawah Di Kecamatan Batin III Ulu Kabupaten Bungo Jambi

Evaluation of Nutrient Status and Recommendations for Fertilization of paddy rice. The assessment was carried out in Batin III Ulu District, Bungo Jambi Regency with a rice field area of 655 ha spread across 8 (eight) villages. This study aims to evaluate the nutrient status and determine fertilization recommendations in paddy rice. The study used a description method based on field observations and laboratory analysis. Examples of composite soils resulting from the field, analyzed the nutrient status of N, P, and K as well as soil pH with the Paddy Soil Test Kit. Based on the value of the N, P, K nutrient status test, it is determined to recommend fertilizer application. N fertilizer during the growth period is applied 3 (three) times, namely at planting time (before 14 DAP), without the use of LCC (leaf colour chart), the second fertilization on active tillering stadia (21-28 DAP), and the third on flower primordia stadia (50 days after planting). The results of the nutrient status analysis with STD, the P and K nutrient status of the soil are grouped into three classes, namely low, medium, and high. From the P and K status classes of the soil, recommendations for fertilization P (SP-36) and K (KCl) are made. The results showed that the obstacle to increasing the productivity of paddy rice in this area is that the content of N, P and K is generally low, and the soil pH ranges from 5-6. Therefore, to increase the productivity of paddy rice yields, it is recommended to apply inorganic fertilizers (N, P, and K) and the addition of organic matter. Based on the results of soil analysis and the nutrient status of paddy soils, site-specific N, P and K fertilization recommendations were obtained. Fertilizers used in the form of Urea, SP-36 and KCl, without the addition of organic matter and with the addition of organic matter.

Response of Lowland Rice as Affected by Seedling Age and Time of Weed Control in Sudan Savana of Nigeria

An experiment was conducted at the Research and Training Farm of Federal College of Horticulture Gombe State (10020’N and 10030’E) during the 2021 rainy season in the Sudan Savanah agro-ecological zone of Nigeria. The aim of the research is to evaluate the effect of seedling age and time of application of post-emergence herbicide on the growth and yield of lowland rice (Faro 44). The experiment consisted of two factors, namely:- seedling age ( 3, 4, and 5-week-old seedlings) and time of weed control by post-emergence herbicide at 2, 3, and 4 weeks after transplanting. Farmer's practice hoes weeding, 7 weeks after transplanting as check and controls i.e. no weeding). These treatments were factorial combined (3 x 5) to give 15 treatment combinations of treatment and replicated thrice. The seedling was allocated to the main plot while weed control was to the sub-plot. Data gathered on weed, growth, yield, and yield attributes were subjected to analysis of variance, and mean differences were separated using Student Newman keuls (SNK ) at p&lt; 0.05. The result revealed significant differences due to seedling age and time of weeding in most characters measured. Generally, the 3-week-old seedling (3WOS) performed better but at par with 4WOS, while earlier application of herbicides at 2 weeks after transplanting (WAT) gave excellent weed control. The highest yield of paddy rice 8849.4 and 9517.2 kg/ha, was obtained from 2WOS and herbicide application at 2WAT. It can be concluded that 3-4WOS seedlings of Faro 44 variety of rice and early application of herbicide at 2wat can be suggested to the rice farmers in the study area.

Green manure rotation and application increase rice yield and soil carbon in the Yangtze River valley of China

The addition of organic matter via green manure rotations in paddy rice has previously been proposed as a smart agricultural practice to maintain soil productivity and support environmental sustainability. However, to date, only a few studies have assessed quantitatively the impact of green manure application on the interactions between agronomic management practices, soil fertility, and crop production. In this study, 800 pairs of data from 108 studies, conducted in the Yangtze River agricultural region of China were assessed, and a meta-analysis was carried out to evaluate and quantify the effect of green manure application on rice yield and soil properties. Firstly, compared to a winter fallow system, amendment with green manure significantly increased paddy rice yield and soil organic carbon (SOC) by 8.1% and 8.4%, respectively. Secondly, analysis using a Random Forest model revealed that paddy rice type, green manure application rate and duration, mineral and organic N fertilizer rate, and initial SOC and pH were identified as the main drivers for paddy rice yield and SOC change. Finally, Marginal Benefit Analysis (MBA) revealed that green manure application rates for production in early rice of double cropping rice (ER) and single rice (SR) were approximately of 20 and 26 t ha-1 respectively. and further, for carbon sequestration, that the optimal rate was ~25 t ha-1. It should, however, be noted that green manure application to soils with already high SOC level might result in the soil becoming a net C source. The study supported the scientific and quantitative indicators for achieving the best benefits of paddy rice yield and SOC increase after green manure application.

Sustainable production of ethyl levulinate by levulinic acid esterification obtained from Colombian rice straw

E-fuels are synthetic fuels produced from renewable sources that have garnered attention because of their potential to reduce environmental impacts in the transport sector. Ethyl levulinate is a fuel additive that can address issues associated with traditional fuels. This product can be obtained from agro-industrial wastes such as rice straw. Therefore, the aim of this study was to assess the technical, economic, and environmental feasibility of producing ethyl levulinate from Colombian rice straw. Aspen Plus v12 and life cycle assessment methodology were used for evaluating the process through the cultivation to the biorefinery stage. A base scenario was analyzed, with an overall yield of 0.115 kg ethyl levulinate/kg rice straw and a total energy consumption of 133.2 kWh/kg of ethyl levulinate produced. A carbon footprint of 2.71 kg CO2-eq/kg Ethyl levulinate was observed, which primarily ascribed to the use of steam derived from fossil fuels. An alternative scenario was proposed by implementing two changes to reduce the environmental impacts. First, steam was generated by the solid hydrolyzed residue combustion, and second, the paddy rice yield was increased to 5.7 t/ha. Reductions of 58.5% and 25.4% in the carbon footprint and ozone depletion were respectively obtained from these improvements. A class V economic assessment is performed for the alternative scenario, yielding a net present value of 18.7 MUSD, payback period of 5 years, and return on investment of 19.6%. Hence, the production of Ethyl levulinate from rice straw is a feasible alternative to boost the e-fuel market while upgrading agro-industrial waste into valuable products.

Practical application of high‐sodicity wasteland reclamation with flue gas desulfurization gypsum in the Songnen Plain of China

AbstractBased on global food supply demands and the need for sustainable development, it is necessary to rapidly reclaim saline‐sodic wasteland as productive land on a large scale. However, the large‐scale application of flue gas desulfurization (FGD) gypsum for the reclamation of high‐sodicity wasteland to obtain productive fields still lacks quick and concise evaluation indicators. Therefore, four FGD gypsum reclamation practices were applied in high sodicity‐affected wastelands. After 6 months, the topsoil (0–20 cm) pH, exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), electrical conductivity (EC), and paddy rice yield were evaluated. During the rice harvest, the topsoil pH, ESP, and SAR significantly decreased by 0.9–1.9 units, 29.3–67.2% and 2.3–53.7 (mmolc L−1)1/2, respectively, below initial values. Across the application sites, the interquartile range of the rice yield ranged from 1.7 to 5.8 Mg ha−1 with a median yield of 3.7 Mg ha−1. Correlation analysis between the rice yield and topsoil chemical parameters indicated that the soil pH was the primary factor of rice yield reduction, followed by ESP and SAR. To achieve a median yield, we propose that the pH, ESP and SAR of reclaimed topsoil should be lower than 8.7, 27.5%, and 8.5 (mmolc L−1)1/2, respectively, during the first season. This study provides a practical template and reference values for the salinity and sodicity of topsoil when reclaiming high sodicity‐affected wastelands via large‐scale FGD gypsum application.

Influence of planting methods and organic amendments on rice yield and bacterial communities in the rhizosphere soil.

A comprehensive understanding of rice cultivation techniques and organic amendments affecting soil quality, enzyme activities and bacterial community structure is crucial. We investigated two planting methods (direct seeding and transplanting) of paddy rice (Oryza sativa) and organic amendments with rice straw and biochar on crop yield and soil biological and physicochemical properties. Rhizosphere bacterial communities at the maturity stage of rice growth were characterized through high-throughput 16S rRNA sequencing. Soil biochemical properties and enzyme activity levels were analyzed. Grain yield of paddy rice with transplanting increased 10.6% more than that with direct seeding. The application of rice straw increased grain yield by 7.1 and 8.2%, more than with biochar and the control, respectively. Compared to biochar and the control, the application of rice straw significantly increased sucrase, cellulase, protease, organic carbon, available phosphorus, nitrate, and ammonium. The application of biochar increased microbial biomass nitrogen and carbon, urease, pH, available nitrogen, and available potassium compared to the application of rice straw and the control. Principal coordinate analysis and dissimilarity distances confirmed significant differences among the microbial communities associated with planting methods and organic amendments. Bacteroidetes, Nitrospirae, Firmicutes, and Gemmatimonadetes abundance increased with rice straw relative to biochar and the control. The biochar addition was associated with significant increases in Chloroflexi, Patescibacteria, Proteobacteria, and Actinobacteria abundance. Pearson’s correlation analyzes showed that Chloroflexi, Bacteroidetes and Nitrospirae abundance was positively correlated with grain yield. The relative abundance of these bacteria in soil may be beneficial for improving grain yield. These results suggest that planting methods and organic amendments impact soil biochemical characteristics, enzyme activity levels, and microbial community composition.

High Sink Capacity Improves Rice Grain Yield by Promoting Nitrogen and Dry Matter Accumulation

Sink capacity, nitrogen (N), and dry matter accumulation (DMA) all play essential roles in promoting high rice grain yield, but their relationship is unclear. Here, a field experiment was conducted from 2020 to 2021 with Zhuangxiangyou Baijin 5 as the test cultivar. Two rates of N (T1 = 90 kg ha−1 N and T2 = 180 kg ha−1 N) and three transplanting densities (272,000 hills ha−1 (M1), 238,000 hills ha−1 (M2), and 206,000 hills ha−1 (M3)) were used to investigate rice grain yield and corresponding yield attributes. The results showed significant differences in rice yield, sink capacity, N and DMA, and the leaf area index (LAI) at the heading stage among the different treatments. The results showed that the output of T2M1 was the highest in 2020, increasing by 16.6% compared with the lowest output, while the output of T2M2 was the highest in 2021, increasing by 11.9% compared with the lowest output. During 2020, the highest sink capacity, LAI at the heading stage, and maximum dry matter accumulation at the maturity stage of rice were recorded in T2M1, while the highest N accumulation was recorded in T2M2. Furthermore, the sink capacity, as well as levels of N and DMA, of rice in 2020 was higher in T2M2, and the LAI was higher in T2M1 at the heading stage. Correlation analyses showed that yield was significantly positively correlated with N and DMA. In addition, a significant positive correlation between sink capacity and DMA was observed during both years, while a significant positive correlation between sink capacity and N accumulation was observed in 2021. Thus, we conclude that a high sink capacity can increase rice yield by increasing N and DMA because a high sink capacity is the internal driving force of high rice grain yield. In conclusion, the T2M1 regimen is a promising approach for improving the grain yield of paddy rice.