Search Results (31)

The accurate estimation of double-season rice yield is critical for ensuring national food security. To address the limitations of traditional crop models in spatial resolution and accuracy, this study innovatively developed the HASM-APSIM coupled model by integrating High-Accuracy Surface Modeling (HASM) with the Agricultural Production Systems sIMulator (APSIM) to simulate the historical yield of double-season rice in Jiangxi Province from 2000 to 2018. The methodological advancements included the following: the localized parameter optimization of APSIM using the Nelder–Mead simplex algorithm and NSGA-II multi-objective genetic algorithm to adapt to regional rice varieties, enhancing model robustness; coarse-resolution yield simulations (10 km grids) driven by meteorological, soil, and management data; and high-resolution refinement (1 km grids) via HASM, which fused APSIM outputs with station-observed yields as optimization constraints, resolving the trade-off between accuracy and spatial granularity. The results showed that the following: (1) Compared to the APSIM model, the HASM-APSIM model demonstrated higher accuracy and reliability in simulating historical yields of double-season rice. For early rice, the R-value increased by 14.67% (0.75→0.86), RMSE decreased by 34.02% (838.50→553.21 kg/hm²), MAE decreased by 31.43% (670.92→460.03 kg/hm²), and MAPE dropped from 11.03% to 7.65%. For late rice, the R-value improved by 27.42% (0.62→0.79), RMSE decreased by 36.75% (959.0→606.58 kg/hm²), MAE reduced by 26.37% (718.05→528.72 kg/hm²), and MAPE declined from 11.05% to 8.08%. (2) Significant spatiotemporal variations in double-season rice yields were observed in Jiangxi Province. Temporally, the simulated yields of early and late rice aligned with statistical yields in terms of numerical distribution and interannual trends, but simulated yields exhibited greater fluctuations. Spatially, high-yield zones for early rice were concentrated in the eastern and central regions, while late rice high-yield areas were predominantly distributed around Poyang Lake. The 1 km resolution outputs enabled the precise identification of yield heterogeneity, supporting targeted agricultural interventions. (3) The growth rate of double-season rice yield is slowing down. To safeguard food security, the study area needs to boost the development of high-yield and high-quality crop varieties and adopt region-specific strategies. The model proposed in this study offers a novel approach for simulating crop yield at the regional scale. The findings provide a scientific basis for agricultural production planning and decision-making in Jiangxi Province and help promote the sustainable development of the double-season rice industry. Full article

The sustainability of rice-cropping systems hinges on balancing resources, output, and environmental impacts. China is revitalizing the ancient ratoon rice (RR) system for input savings and environmental benefits. Prior research has explored the RR system’s performance using various individual indicators, but few studies have focused on its overall balance of these factors. Environmental efficiency (EE) analysis addresses this gap. Using field survey data from Hunan Province in China and the slacks-based data envelopment analysis method, we quantified the EE of the RR, double-season rice (DR), and single-season rice (SR) systems. Key findings include: (1) the RR system outperforms in carbon emissions and non-point source pollution; (2) the RR system’s EE is 0.67, significantly higher than the DR (0.58) and SR (0.57) systems, indicating superior performance; and (3) despite its relatively high EE, the RR system can still improve, mainly due to input redundancy and production value shortfall. These findings provide strategies for optimizing RR systems to enhance agricultural sustainability. Full article

The rising temperatures and changes in precipitation due to climate change have significantly impacted agricultural production. Evaluating the effects of climate change on rice production is crucial for improving rice cultivation techniques and ensuring food security. It is essential to comprehensively examine the climatic, spatial, and temporal variations during the duration of crop production. Previous research has mainly focused on different rice planting areas, rice types, and various growth stages of rice. However, more research is needed on the climatic changes during the crop-growing season in specific regions. Therefore, this study compiled complete daily meteorological data from 37 meteorological stations in Hunan Province from 1961 to 2020. The period from 1961 to 2020 was divided into three segments: 1961–1980 (a), 1981–2000 (b), and 2001–2020 (c), to analyze the characteristics of agricultural climate resource changes during different growth stages of early-season rice in Hunan Province. Results show that the heat resources were significantly increased (accumulated temperature growth rate of 43.36 °C/10a), the sunshine resources were decreased by −14.60 h/10a, and the precipitation resources were slightly increased by 6.85 mm/10a. The increase in heat resources mainly occurs during the vegetative growth stage of early-season rice. Additionally, the high-value regions of heat resources and precipitation in period c are 97.8% and 34.2% higher than the average values of periods a and b, respectively. In contrast, the regions with high sunshine hours significantly decreased in period c compared to periods a and b. In summary, the heat, sunshine, and water resources in the central and eastern regions of Hunan Province increase simultaneously, and appropriate cultivation measures should be adopted in the future to improve the yield and resource utilization efficiency of early-season rice in a double-cropping system. Full article

Rice (Oryza sativa L.) cultivation using direct seeding is susceptible to chilling stress, particularly during seed germination and early seedling growth in the early season of a double cropping system. Alternatively, seed priming with various plant growth-promoting hormones is an effective technique to promote rapid and uniform emergence under chilling stress. Therefore, we evaluated the impact of gibberellin A3 (GA₃) and brassinolide (BR) priming on rice seed emergence, examining their proteomic responses under low-temperature conditions. Results indicated that GA₃ and BR increased the seed germination rate by 22.67% and 7.33% at 72 h and 35% and 15% at 96 h compared to the control (CK), respectively. Furthermore, proteomic analysis identified 2551, 2614, and 2592 differentially expressed proteins (DEPs) in GA, BR, and CK, respectively. Among them, GA exhibited 84 upregulated and 260 downregulated DEPs, while BR showed 112 upregulated and 102 downregulated DEPs, and CK had 123 upregulated and 81 downregulated DEPs. Notably, under chilling stress, both GA₃ and BR are involved in peroxide metabolism, phenylpropanoid biosynthesis, and inositol phosphate metabolism, enhancing antioxidant capacity and providing energy substances for germination. In addition, GA₃ triggers the specific regulation of stress responsive protein activation, GTP activation, and ascorbic acid biosynthesis and promotes the stability and integrity of cell membranes, as well as the synthesis of cell walls, providing physical defense for seeds to resist low temperatures. At the same time, BR triggers specific involvement in ribosome synthesis and amino acid synthesis, promoting biosynthetic ability and metabolic regulation to maintain plant life activities under low-temperature stress. Furthermore, the various genes’ expression (OsJ_16716, OsPAL1, RINO1) confirmed GA₃ and BR involved in peroxide metabolism, phenylpropanoid biosynthesis, and inositol phosphate metabolism, enhancing antioxidant capacity and providing energy substances for germination. This study provides valuable insights into how rice seed embryo responds to and tolerates chilling stress with GA₃ seed priming. Full article

Crop straw returning to the field is an effective practice for straw utilization to improve soil fertility and sustain crop productivity. However, little information is available about the long-term effects of paddy straw return on soil properties and rice yield under a double-rice system. The objectives of this study were to test the hypothesis of the effects of different amounts of paddy straw returned to the field on soil physicochemical properties and rice yield, and to clarify the correlation between crop yield and soil physicochemical properties as well as quick-acting nutrients under different straw-returning modes. The experiment, initiated in the 2005 rice season, utilized “Xiang 45” and “Xiang 13” long-grained rice cultivars within a double-season rice cropping system. Three straw-returning treatments were implemented: rotary tillage with full rice straw incorporation (RTS), incorporation of one-third of the rice straw (1/3RTS), and incorporation of two-thirds of the rice straw (2/3RTS). This study found that among the three straw return rates, 2/3RTS had the most significant impact on soil physicochemical properties. Soil nitrogen content was identified as a crucial factor influencing soil organic carbon (SOC) accumulation, while pH levels significantly affected rice yield. Straw incorporation effectively increased the content and stocks of SOC. Full article

Rice effective panicle is a major trait for grain yield and is affected by both the genetic tiller numbers and the early tillering vigor (ETV) traits to survive environmental adversities. The mechanism behind tiller bud formation has been well described, while the genes and the molecular mechanism underlying rice-regulating ETV traits are unclear. In this study, the candidate genes in regulating ETV traits have been sought by quantitative trait locus (QTL) mapping and bulk-segregation analysis by resequencing method (BSA-seq) conjoint analysis using rice backcross inbred line (BIL) populations, which were cultivated as late-season rice of double-cropping rice systems. By QTL mapping, seven QTLs were detected on chromosomes 1, 3, 4, and 9, with the logarithm of the odds (LOD) values ranging from 3.52 to 7.57 and explained 3.23% to 12.98% of the observed phenotypic variance. By BSA-seq analysis, seven QTLs on chromosomes 1, 2, 4, 5, 7, and 9 were identified using single-nucleotide polymorphism (SNP) and insertions/deletions (InDel) index algorithm and Euclidean distance (ED) algorithm. The overlapping QTL resulting from QTL mapping and BSA-seq analysis was shown in a 1.39 Mb interval on chromosome 4. In the overlap interval, six genes, including the functional unknown genes Os04g0455650, Os04g0470901, Os04g0500600, and ethylene-insensitive 3 (Os04g0456900), sialyltransferase family domain containing protein (Os04g0506800), and ATOZI1 (Os04g0497300), showed the differential expression between ETV rice lines and late tillering vigor (LTV) rice lines and have a missense base mutation in the genomic DNA sequences of the parents. We speculate that the six genes are the candidate genes regulating the ETV trait in rice, which provides a research basis for revealing the molecular mechanism behind the ETV traits in rice. Full article

Accurately tracking the changes in rice cropping intensity is a critical requirement for policymakers to formulate reasonable land-use policies. Southern China is a traditional region for rice multi-cropping, yet less is known about its spatial–temporal changes under the background of rapid urbanization in recent decades. Based on images from Landsat and MODIS and multiple land cover products, the gap-filling and Savitzky–Golay filter method (GF-SG), the enhanced pixel-based phenological features composite approach (Eppf-CM), random forest (RF), and the difference in NDVI approach (DNDVI) were combined to map the rice cropping pattern with a spatial resolution of 30 × 30 m over Southern China in 2000 and 2020 through Google Earth Engine (GEE). Subsequently, the spatial–temporal changes in rice cropping intensity and their driving factors were examined by Getis-Ord Gi* and geographical detector. The results showed that the produced rice cropping pattern maps exhibited high accuracy, with kappa coefficients and overall accuracies exceeding 0.81 and 90%, respectively. Over the past two decades, the planting areas of double-season rice in Southern China decreased by 54.49%, and a reduction was observed across eight provinces, while only half of the provinces exhibited an increase in the planting areas of single-season rice. Compared to the year 2000, the planting area of the conversion from double- to single-season rice cropping systems in 2020 was 2.71 times larger than that of the conversion from single- to double-season rice cropping systems. The hotspots of the change in rice cropping intensity were mainly located in the central part of Southern China (excluding the Poyang Lake Plain). The decline in the rural labor force, coupled with ≥10 °C accumulated temperature and topographical factors, plays a crucial role in the decreased intensity of rice cropping. Our findings can be beneficial for realizing regional agricultural sustainability and food security. Full article

The ratoon rice cropping system (RR) is developing rapidly in China due to its comparable annual yield and lower agricultural and labor inputs than the double rice cropping system (DR). Here, to further compare the greenhouse effects of RR and DR, a two-year field experiment was carried out in Hubei Province, central China. The ratoon season showed significantly lower cumulative CH₄ emissions than the main season of RR, the early season and late season of DR. RR led to significantly lower annual cumulative CH₄ emissions, but no significant difference in cumulative annual N₂O emissions compared with DR. In RR, the main and ratoon seasons had significantly higher and lower grain yields than the early and late seasons of DR, respectively, resulting in comparable annual grain yields between the two systems. In addition, the ratoon season had significantly lower global warming potential (GWP) and greenhouse gas intensity-based grain yield (GHGI) than the main and late seasons. The annual GWP and GHGI of RR were significantly lower than those of DR. In general, the differences in annual CH₄ emissions, GWP, and GHGI could be primarily attributed to the differences between the ratoon season and the late season. Moreover, GWP and GHGI exhibited significant positive correlations with cumulative emissions of CH₄ rather than N₂O. The leaf area index (LAI) and biomass accumulation in the ratoon season were significantly lower than those in the main season and late season, and CH₄ emissions, GWP, and GHGI showed significant positive correlations with LAI, biomass accumulation and grain yield in the ratoon and late season. Finally, RR had significantly higher net ecosystem economic benefits (NEEB) than DR. Overall, this study indicates that RR is a green cropping system with lower annual CH₄ emissions, GWP, and GHGI as well as higher NEEB. Full article

Multiple cropping systems constitute an essential agricultural practice that will ensure food security within the increasing demand of basic cereals as a consequence of global population growth and climate change effects. In this regard, there is a need to develop new methodologies to adequately monitor cropland intensification. The main objective of this research was to assess cropland intensification by means of spectral analysis of MODIS NDVI time series in a high cloudiness tropical area such as Ecuador. A surface of 89,225 ha of the main staple crops in this country, which are rice and maize crops, was monitored to assess the evolution of the number of crop cycles. The 20-year period of NDVI time series was used to calculate the periodograms across four subperiods (2001–2005, 2006–2010, 2011–2015, 2016–2020). The maximum ordinate value of each periodogram was used as an indicator of the number of growing crop cycles per year identifying single-, double-, and triple-cropping systems in each subperiod. Cropland intensification was assessed by comparing the cropping system between the subperiods. Results reveal that more than half of the studied croplands experienced changes in the cropping systems, and 40% showed positive trends in terms of the number of growing crop cycles, being principally located near the main rivers where irrigation facilitates crop development during the dry season. Therefore, the area under single cropping decreased from over 60,000 ha in the first subperiod to less than 50,000 ha in the last two subperiods. The cropland surface subjected to multi-cropping practices increased during the second decade of the study period, with a double-cropping system being more widely used than growing three crops per year, reaching surfaces of 24,400 ha and 10,450 ha in the last subperiod, respectively. The robust results obtained in this research show the great potential of the periodogram approach for the discrimination of cropping systems and for mapping intensification areas in tropical regions where dealing with noisy remote sensing time series as a consequence of high cloudiness is a great challenge. Full article

Ratoon rice, an effective rice cultivation system, allows paddy rice to be harvested twice from the same stubble, playing an important role in ensuring food security and adapting to climate change with its unique growth characteristics. However, there is an absence of research related to remote-sensing monitoring of ratoon rice, and the presence of other rice cropping systems (e.g., double-season rice) with similar characteristics poses a hindrance to the accurate identification of ratoon rice. Furthermore, cloudy and rainy regions have limited available remote-sensing images, meaning that remote-sensing monitoring is limited. To address this issue, taking Yongchuan District, a typical cloud-prone region in Chongqing, China, as an example, this study proposed the construction of a time-series optical dataset using the Modified Neighborhood Similar Pixel Interpolator (MNSPI) method for cloud-removal interpolation and the Flexible Spatiotemporal DAta Fusion (FSDAF) model for fusing multi-source optical remote-sensing data, in combination with vegetation index features and phenological information to build a threshold model to map ratoon rice at high-resolution (10 m). The mapping performance of ratoon rice was evaluated using independent field samples to obtain the overall accuracy and kappa coefficient. The findings indicate that the combination of the MNSPI method and FSDAF model had a stable and effective performance, characterized by high correlation coefficient (r) values and low root mean square error (RMSE) values between the restored/predicted images and the true images. Notably, it was possible to effectively capture the distinct characteristics of ratoon rice in cloudy and rainy regions using the proposed threshold model. Specifically, the identified area of ratoon rice in the study region was 194.17 km², which was close to the official data (158–180 km²), and the overall accuracy and kappa coefficient of ratoon rice identification result were 90.73% and 0.81, respectively. These results demonstrate that our proposed threshold model can effectively distinguish ratoon rice during vital phenological stages from other crop types, enrich the technical system of rice remote-sensing monitoring, and provide a reference for agricultural remote-sensing applications in cloudy and rainy regions. Full article

Accurate and timely acquisition of cropping intensity and spatial distribution of paddy rice is not only an important basis for monitoring growth and predicting yields, but also for ensuring food security and optimizing the agricultural production management system of cropland. However, due to the monsoon climate in southern China, it is cloudy and rainy throughout the year, which makes it difficult to obtain accurate information on rice cultivation based on optical time series images. Conventional image synthesis is prone to omission or redundancy of spectral and temporal features that are potentially important for rice-growth identification, making it difficult to determine the optimal features for high-precision mapping of paddy rice. To address these issues, we develop a method to granulate the effective use interval of classification features by extracting phenological signatures of rice to obtain cost-effective and highly accurate mapping results. Two steps are involved in this method: (1) analyzing the information on various features (spectra, polarization, and seasonal regularity) to identify three key phenological periods throughout the lifespan of paddy rice; (2) identifying the features with the highest class separation between paddy rice, non-paddy crops, and wetlands under different phenological stages; and (3) removing redundant features to retain the optimal feature combinations. Subsequently, the obtained feature sets are used as input data for the random forest classifier. The results showed that the overall accuracy of the identified rice results was 95.44% with F1 scores above 93% for both single- and double-cropping rice. Meanwhile, the correlation coefficient of our mapped rice area compared with the official statistics of rice area at county and district levels was 0.86. In addition, we found that combining Sentinel-1 and Sentinel-2 images for rice recognition was better than using Sentinel-1 or Sentinel-2 alone, and the classification accuracy was improved by 5.82% and 2.39%, which confirms that the synergistic Sentinel-1 and Sentinel-2 data can effectively overcome the problem of missing optical images caused by clouds and rain. Our study demonstrates the potential of distinguishing mixed rice-cropping systems in subtropical regions with fragmented rice-field distribution in a cloudy and rainy environment, and also provides a basis for the rational layout of rice production and improvement of cultivation systems. Full article

This study aimed to investigate the impacts of straw and biochar on greenhouse gas (GHG) emissions and grain yield in a double rice cropping system under optimal N fertilizer reduction. Conventional fertilization (CF) was used as the control group, and treatments included optimal fertilization and 15% less nitrogen (OF), together with straw (S) or biochar (B) applied under different fertilization conditions, namely CF + S, CF + B, OF + S, and OF + B. The effects of treatments on soil CH₄ and N₂O emissions were studied, and changes in soil physicochemical properties were analyzed. The results showed that relative to CF, CF + S and OF + S increased the cumulative CH₄ emissions by 11.80% and 2.35%, respectively, while CF + B and OF + B resulted in significant reductions in cumulative CH₄ emissions by 27.80% and 28.46%, respectively. Biochar was effective in reducing N₂O emissions, and OF further increased the potential, with CF + B and OF + B achieving the best N₂O reductions of 30.56% and 32.21%, respectively. Although OF reduced yields by 0.16%, this difference was within reasonable limits; the remaining treatments increased grain yields by 2.55% to 3.47%. CF + B and OF + B reduced the global warming potential (GWP) by 27.93% and 28.63%, respectively, and ultimately reduced the greenhouse gas emission intensity (GHGI) by 30.42% and 30.97%. Both straw and biochar increased the soil organic matter, NH₄⁺-N, and NO₃⁻-N contents, and biochar increased the soil pH, which may be the potential mechanism regulating soil GHG emissions. Overall, OF + B is beneficial for reducing GHG emissions and may be a better agronomic cropping pattern in double season rice growing areas. Full article

Excessive nitrogen (N) fertilization, low use efficiency, and heavy pollution are the dominant issues that exist in intensively cultivated double rice cropping systems in China. Two-year field and ¹⁵N microregion experiments were conducted to evaluate the N fate in a soil-rice system under a series of different N rate treatments from 2020 to 2021. The economic N application rate that simultaneously improved rice yield and N use efficiency in the rotation system was also investigated. Results demonstrated that soil residues and mineralized N accounted for more than 58.0% and 53.2% of the total N input in the early and late rice seasons, respectively. Similarly, most of the total N input was absorbed by rice, ranging from 43.7% to 55.6% in early rice and from 36.8% to 54.7% in late rice. Rice N use efficiency significantly decreased with increasing N application, while rice grain yield and its N uptake increased when the N application rate was below 150 kg ha⁻¹ in early rice and 200 kg ha⁻¹ in late rice. Exceeding this point limited rice N uptake and yield formation. The apparent N recovery rate, N residual rate, and N loss rate were 23.5–34.4%, 17.0–47.1%, and 26.0–47.8% for the early rice, and 32.8–37.3%, 74.2–87.0%, and 71.5–92.1% for the late rice. The linear plateau analysis further indicated that the recommended N application rate (118.5–152.8 kg ha⁻¹ for early rice and 169.9–186.2 kg ha⁻¹ for late rice) can not only maintain a relatively higher rice yield and N utilization but also significantly reduce soil N residue. Our results provide theoretical guidance for improving N management in double-cropping rice fields in southern China. Full article

Double-cropping rice cultivation reduces soil fertility, and the extensive use of chemical fertilizers has harmful effects on both the environment and grain yield. The application of organic materials could be used as a practical strategy to maintain soil fertility and improve grain yield in a double-season rice cropping system. For this purpose, field experiments with six growing seasons over three years, from 2016 to 2018, were conducted to assess the effects of five organic materials (biochar, Chinese milk vetch, rice straw, rapeseed cake fertilizer, and manure) on the grain yield and soil fertility, aiming to save about 25% of the chemical nitrogen (N) fertilizer required for all rice growing stages. The result showed that, compared with CK (the most common dose of fertilizer in this study region; 100% chemical fertilizer without organic fertilizer), the grain yield and soil fertility of double-cropped rice were increased after applying organic fertilizers for three consecutive years. Specifically, the CRC treatment (Chinese milk vetch (10.77 t ha⁻¹ in fresh)/rice straw (26.51 t ha⁻¹ in fresh) + 75% chemical fertilizer) showed significantly higher rates of effective panicles (4.65–10.92%) and annual grain yield (8.00–8.82%). The total N, total phosphorus (P), total potassium (K), alkaline N, and available P content in the CRC soil were significantly increased by 11.85%, 12.22%, 15.08%, 23.32%, and 41.04%, respectively, relative to CK. The decomposition of the applied Chinese milk vetch and rice straw combined with 75% chemical fertilizer resulted in more soil humus (9.50 g kg⁻¹), humic acid (3.19 g kg⁻¹), fulvic acid (3.26 g kg⁻¹), and active organic carbon (5.78 g kg⁻¹) and a significantly higher carbon pool management index (13.5%), as well as significantly higher soil urease activity (18.10%) and acid phosphatase activity (17.64%). Therefore, in this study, Chinese milk vetch (10.77 t ha⁻¹ in fresh) in the early rice season/rice straw (26.51 t ha⁻¹ fresh) in the late rice season + 75% chemical fertilizer treatment was the optimal dose for the double-season rice cropping system. It resulted in higher rice yields and has the potential to be used for more sustainable soil fertility. Full article

Enhanced-efficiency nitrogen fertilizer (EENF) is a recommend nitrogen fertilizer for rice production because of its advantage on improving nitrogen use efficiency. However, its efficacy on CH₄, the dominant greenhouse gas, emission from rice fields showed great variation under field conditions. And the factors influencing its efficacy are still unclear. We synthesized the results of 46 field studies and analyzed the impact of product type, rice variety, and primary agronomic measures (rice cropping system, nitrogen (N) application rate, and water management options) on the effectiveness of EENF on the CH₄ emission and rice yield. Overall, EENF, including inhibitors (IS) and slow/control-released fertilizer (S/CRF), significantly reduced CH₄ emission by 16.2% and increased rice yield by 7.3%, resulting in a significant reduction in yield-scaled CH₄ by 21.7%, compared with conventional N fertilizer. Nitrapyrin, DMPP (3,4-dimethylpyrazole phosphate), and HQ (Hydroquinone) + Nitrapyrin showed relative higher efficacy on the mitigation of CH₄ emission than other EENF products; and HQ showed relative lower efficacy on rice yield than other EENF products. The reduction in CH₄ emission response of hybrid rice varieties to IS and S/CRF was greater than that of inbred rice varieties. IS significantly reduced the CH₄ emission and increased the rice yield under all three rice cropping systems, and showed the highest efficacy in the late rice season of double rice cropping system. Whereas, S/CRF did not significantly reduce the CH₄ emission from rice seasons of single rice cropping system and rice-upland crops rotation system. IS did not reduce the CH₄ emission when N application rate less than 100 kg ha⁻¹, and S/CRF did not affect the CH₄ emission when N application rate less than 100 kg ha⁻¹ or above 200 kg ha⁻¹. Continuous flooding was unfavorable for IS and S/CRF to mitigate CH₄ emission and enhance rice yield. These results emphasized the necessary to link EENF products with rice varieties and agronomic practices to assess their efficacy on CH₄ emissions and rice yield. Full article