2021 Vol. 20 No. 10 Previous Issue    Next Issue

    Crop Science
    Plant Protection
    Animal Science · Veterinary Medicine
    Agro-ecosystem & Environment
    Agricultural Economics and Management

      Cover illustration

    For Selected: Toggle Thumbnails
    Triple bottom-line consideration of sustainable plant disease management: From economic, sociological and ecological perspectives
    HE Dun-chun, Jeremy J. BURDON, XIE Lian-hui, Jiasui ZHAN
    2021, 20(10): 2581-2591.  DOI: 10.1016/S2095-3119(21)63627-4
    Abstract ( )   PDF in ScienceDirect  

    Plant disease management plays an important role in achieving the sustainable development goals of the United Nations (UN) such as food security, human health, socio-economic improvement, resource conservation and ecological resilience.  However, technologies available are often limited due to different interests between producers and society and lacks of proper understanding of economic thresholds and the complex interactions among ecology, productivity and profitability.  A comprehensive synergy and conflict evaluation of economic, sociological and ecological effects with technologies, productions and evolutionary principles as main components should be used to guide sustainable disease management that aims to mitigate crop and economic losses in the short term while maintaining functional farm ecosystem in the long term.  Consequently, there should be an increased emphasis on technology development, public education and information exchange among governments, researchers, producers and consumers to broaden the options for disease management in the future.

    Crop Science
    A rice geranylgeranyl reductase is essential for chloroplast development
    LIU Xi, YI Xin, YANG Yan-rong, HUANG Qian-qian
    2021, 20(10): 2592-2600.  DOI: 10.1016/S2095-3119(20)63324-X
    Abstract ( )   PDF in ScienceDirect  
    Chloroplasts are essential for plant photosynthesis and growth. Many genes have been identified that regulate plant chloroplast development. However, it is not known at a molecular level how these genes regulate chloroplast biogenesis. In this study, we isolated a mutant ygl2 (yellow-green leaf2) that exhibited a pigment-defective phenotype. YGL2 encodes a geranylgeranyl reductase, and in mutant ygl2, there was a single base change (T1361G) located in the third exon of YGL2 that resulted in a missense mutation (L454R) in the encoded product. Transmission electron microscopy revealed that chloroplast development was impaired in the ygl2 mutant. The expression levels of plastid-encoded genes were significantly altered in the ygl2 mutant. Furthermore, in a yeast two-hybrid assay, we found that YGL2 interacted with the RNA editing factor MORF8.
    Impacts of climate change on drought risk of winter wheat in the North China Plain
    ZHANG Li, CHU Qing-quan, JIANG Yu-lin, CHEN Fu, LEI Yong-deng
    2021, 20(10): 2601-2612.  DOI: 10.1016/S2095-3119(20)63273-7
    Abstract ( )   PDF in ScienceDirect  
    Drought is a major natural disaster causing crop yield losses, while its occurrence mechanism and spatiotemporal variations in a changing climate are still not clear. Based on a long-term climatic dataset (during 1958–2015) from weather stations in the North China Plain (NCP), the influencing mechanism of various climatic factors on drought risk of winter wheat was quantified by using sensitivity analysis, Mann-Kendall trend test and slope estimation. The results indicated that climatic factors have changed considerably over the past six decades in the growth season of winter wheat. As a result, winter wheat suffered from severe droughts (with 350 mm of water deficit during its growth season), particularly at the jointing–heading and heading–mature stages, which were critical to crop yield formation. There were large spatial and temporal variations in drought risk and climatic change factors at different growth stages of winter wheat. Despite precipitation playing a vital role in determining the spatiotemporal patterns of drought risk, high temperature and low humidity along with other climatic factors at key growth stages of winter wheat aggravated drought risk. Particularly, temperature at nearly 90% weather stations showed a notablely upward trend, which exacerbated water deficit and drought risk of winter wheat. Given the complexity and high uncertainty of climate change, these findings provide important information for adapting crop production to future climate change and accompanied droughts while ensuring food security and agricultural sustainability.
    Rapid determination of leaf water content for monitoring waterlogging in winter wheat based on hyperspectral parameters
    YANG Fei-fei, LIU Tao, WANG Qi-yuan, DU Ming-zhu, YANG Tian-le, LIU Da-zhong, LI Shi-juan, LIU Sheng-ping
    2021, 20(10): 2613-2626.  DOI: 10.1016/S2095-3119(20)63306-8
    Abstract ( )   PDF in ScienceDirect  
    Waterlogging is becoming an obvious constraint on food production due to the frequent occurrence of extremely high-level rainfall events.  Leaf water content (LWC) is an important waterlogging indicator, and hyperspectral remote sensing provides a non-destructive, real-time and reliable method to determine LWC.  Thus, based on a pot experiment, winter wheat was subjected to different gradients of waterlogging stress at the jointing stage.  Leaf hyperspectral data and LWC were collected every 7 days after waterlogging treatment until the winter wheat was mature.  Combined with methods such as vegetation index construction, correlation analysis, regression analysis, BP neural network (BPNN), etc., we found that the effect of waterlogging stress on LWC had the characteristics of hysteresis and all waterlogging stress led to the decrease of LWC.  LWC decreased faster under severe stress than under slight stress, but the effect of long-term slight stress was greater than that of short-term severe stress.  The sensitive spectral bands of LWC were located in the visible (VIS, 400–780 nm) and short-wave infrared (SWIR, 1 400–2 500 nm) regions.  The BPNN Model with the original spectrum at 648 nm, the first derivative spectrum at 500 nm, the red edge position (λr), the new vegetation index RVI (437, 466), NDVI (437, 466) and NDVI´ (747, 1 956) as independent variables was the best model for inverting the LWC of waterlogging in winter wheat (modeling set: R2=0.889, RMSE=0.138; validation set: R2=0.891, RMSE=0.518).  These results have important theoretical significance and practical application value for the precise control of waterlogging stress. 
    Does nitrogen application rate affect the moisture content of corn grains?
    ZHANG Yuan-meng, XUE Jun, ZHAI Juan, ZHANG Guo-qiang, ZHANG Wan-xu, WANG Ke-ru, MING Bo, HOU Peng, XIE Rui-zhi, LIU Chao-wei, LI Shao-kun
    2021, 20(10): 2627-2638.  DOI: 10.1016/S2095-3119(20)63401-3
    Abstract ( )   PDF in ScienceDirect  
    Nitrogen fertilizer application is an important measure to obtain high and stable corn yield, and the moisture content of corn grains is an important factor affecting the quality of mechanical grain harvesting.  In this study, four different nitrogen fertilizer treatments from 0 to 450 kg ha–1 pure nitrogen were set for a planting density of 12.0×104 plants ha–1 in 2017 and 2018, and 18 different nitrogen fertilizer treatments from 0 to 765 kg ha–1 pure nitrogen were set for planting densities of 7.5×104 and 12.0×104 plants ha–1 in 2019, to investigate the effect of nitrogen application rate on the moisture content of corn grains.  Under each treatment, the growth of corn, leaf area index (LAI) of green leaves, grain moisture content, and grain dehydration rate were measured.  The results showed that, as nitrogen application increased from 0 to 765 kg ha–1, the silking stage was delayed by about 1 day, the maturity stage was delayed by about 1–2 days, and the number of physiologically mature green leaves and LAI increased.  At and after physiological maturity, the extreme difference in grain moisture content between different nitrogen application rates was 1.9–4.0%.  As the amount of nitrogen application increased, the corn grain dehydration rate after physiological maturity decreased, but it did not reach statistical significance between nitrogen application rate and grain dehydration rate.  No significant correlation was observed between LAI at physiological maturity and grain dehydration rate after physiological maturity.  In short, nitrogen application affected the grain moisture content of corn at and after physiological maturity, however, the difference in grain moisture content among different nitrogen application rates was small.  These results suggest that the effect of nitrogen application on the moisture content of corn grains should not be considered in agricultural production.
    Effects of drought stress on root morphology and spatial distribution of soybean and adzuki bean
    Hyen Chung CHUN, Sanghun LEE, Young Dae CHOI, Dong Hyeok GONG, Ki Youl JUNG
    2021, 20(10): 2639-2651.  DOI: 10.1016/S2095-3119(20)63560-2
    Abstract ( )   PDF in ScienceDirect  
    Due to global climate change, Korea is facing severe droughts that affect the planting and early vegetative periods of upland crops.  Soybean and adzuki bean are important legume crops in Korea, so it is critical to understand their adaptations to water stress.  This study investigated the changes in root morphological properties in soybean and adzuki bean and quantified the findings using fractal analysis.  The experiment was performed at the National Institute of Crop Science in Miryang, Korea.  Soybeans and adzuki beans were planted in test boxes and grown for 30 days.  The boxes were filled with bed soil with various soil moisture treatments.  Root images were obtained and scanned every two days, and the root properties were characterized by root length, depth and surface area, number of roots, and fractal parameters (fractal dimension and lacunarity).  Root depth, length and surface area and the number of roots increased in both crops as the soil moisture content increased.  The fractal dimension and lacunarity values increased as the soil moisture content increased.  These results indicated that the greater the soil moisture, the more heterogeneous the root structure.  Correlation analysis of the morphological properties and fractal parameters indicated that soybean and adzuki bean had different root structure developments.  Both soybean and adzuki bean were sensitive to the amount of soil moisture in the early vegetative stage.  Soybean required a soil moisture content greater than 70% of the field capacity to develop a full root structure, while adzuki bean required 100% of the field capacity.  These results would be useful in understanding the responses of soybean and adzuki bean to water stress and managing irrigation during cultivation.
    Genome-wide analysis of the invertase genes in strawberry (Fragaria×ananassa)
    YUAN Hua-zhao, PANG Fu-hua, CAI Wei-jian, CHEN Xiao-dong, ZHAO Mi-zhen, YU Hong-mei
    2021, 20(10): 2652-2665.  DOI: 10.1016/S2095-3119(20)63381-0
    Abstract ( )   PDF in ScienceDirect  
    Sugar is an important material basis in fruit development, and strawberry fruit flavour and sweetness largely depend on the sugar content and variety.  Invertases (INVs) play an important role in the regulation of sugar accumulation because they irreversibly catalyse the hydrolysis of sucrose into the corresponding nucleoside diphosphate-glucose, glucose or fructose in fruit.  In this work, we provided a comprehensive analysis of the INV gene family in octoploid strawberry (Fragaria×ananassa), including the gene structure, chromosomal locations, conserved domains, and gene evolution and expression profiles during strawberry fruit development.  Our study revealed that polyploid events resulted in the abundant amplification (almost three- or four-fold) of the INV gene in the F.×ananassa genome, and these amplified INV genes showed dominant expression in strawberry fruit.  More than half of the FaINVs transcripts with low expression had incomplete coding sequences by alternative splicing.  Previous studies have shown that cell wall invertases (CWINV) are involved in the regulation of phloem unloading and sink strength establishment.  The expression of FaCWINV1 was markedly upregulated during fruit development and strongly expressed in ripe fruit.  Moreover, a significant correlation was observed between the total sugar content and the FaCWINV1 expression level.  These findings suggest that FaCWINV1 may be involved in sugar accumulation in strawberry fruit.  Taken together, the results of our study will be beneficial for further research into the functions of INVs in the regulation of fruit ripening.
    Genome-wide analysis of the SCPL gene family in grape (Vitis vinifera L.)
    WANG Xi-cheng, WU Wei-min, ZHOU Bei-bei, WANG Zhuang-wei, QIAN Ya-ming, WANG Bo, YAN Li-chun
    2021, 20(10): 2666-2679.  DOI: 10.1016/S2095-3119(20)63587-0
    Abstract ( )   PDF in ScienceDirect  
    Serine carboxypeptidase-like (SCPL) proteins are a group of acyltransferase enzymes that have important roles in plant growth, development, and stress responses.  Although SCPL proteins have been studied in many plants, the biological functions of SCPL genes in grape are still unknown.  In this study, 59 putative SCPL proteins were identified from the grape genome.  A bioinformatics analysis, including chromosomal locations, exon/intron structures, phylogeny, cis-elements, and conserved motifs, was performed for the gene family.  The phylogenetic analysis revealed that VvSCPL proteins could be classified into three groups, with the gene motifs in each group showing high similarity levels.  The number of exons in the VvSCPL genes ranged from 1 to 19, suggesting significant variations among grape SCPL genes.  The expression of the VvSCPL genes, as assessed by RNA sequencing (RNA-seq) and quantitative real-time PCR, showed that most VvSCPL genes responded to drought- and waterlogging-stress treatments, which indicated their roles in abiotic stress responses.  The results provide useful information for further study of SCPL genes in grape.
    Optimization of rhizosphere cooling airflow for microclimate regulation and its effects on lettuce growth in plant factory
    LI Kun, FANG Hui, ZOU Zhi-rong, CHENG Rui-feng
    2021, 20(10): 2680-2695.  DOI: 10.1016/S2095-3119(20)63382-2
    Abstract ( )   PDF in ScienceDirect  
    In plant factories, the plant microclimate is affected by the control system, plant physiological activities and aerodynamic characteristics of leaves, which often leads to poor ventilation uniformity, suboptimal environmental conditions and inefficient air conditioning.  In this study, interlayer cool airflow (ILCA) was used to introduce room air into plants’ internal canopy through vent holes in cultivation boards and air layer between cultivation boards and nutrient solution surface (interlayer).  By using optimal operating parameters at a room temperature of 28°C, the ILCA system achieved similar cooling effects in the absence of a conventional air conditioning system and achieved an energy saving of 50.8% while bringing about positive microclimate change in the interlayer and nutrient solution.  This resulted in significantly reduced root growth by 41.7% without a negative influence on lettuce crop yield.  Future development in this precise microclimate control method is predicted to replace the conventional cooling (air conditioning) systems for crop production in plant factories.
    Plant Protection
    Combining simplified DNA extraction technology and recombinase polymerase amplification assay for rapid and equipment-free detection of citrus pathogen Phytophthora parasitica
    CHEN Wei-yu, YU Jia, XU Heng, LU Xin-yu, DAI Ting-ting, TIAN Yue-e, SHEN Dan-yu, DOU Dao-long
    2021, 20(10): 2696-2705.  DOI: 10.1016/S2095-3119(20)63459-1
    Abstract ( )   PDF in ScienceDirect  
    Foot and root rot caused by Phytophthora parasitica is a substantial threat to citrus cultivation, affecting both yield and quality.  Thus, rapid and accurate detection of P. parasitica plays an important role in disease management.  The aim of this study was to develop a simple diagnostic method to detect P. parasitica infection by combining recombinase polymerase amplification and lateral flow strips (LF-RPA).  To establish the LF-RPA assay of P. parasitica, the primers and probe designed based on the Ypt1 gene were tested for specificity to P. parasitica, which showed no cross-reactivity with DNAs of other related oomycete species.  The LF-RPA assay detected the amount of genomic DNA of P. parasitica which was as low as 1 pg.  To make the LF-RPA assay useful in low-resource settings, four simplified DNA extraction methods were compared, after which the LF-RPA assay was applied, with no specialized equipment, to analyze a diverse range of citrus tissues by using a simplified PEG-NaOH method for DNA extraction.  This method was successful in detecting P. parasitica in infected plant samples within 30 min.  Combining the LF-RPA assay and a simplified DNA extraction method could be a potential  detection test for P. parasitica, especially in areas with limited resources.
    Isolation and molecular characterization of entomopathogenic nematode, Heterorhabditis sp. from an arable land in Nigeria
    Fisayo Y. DARAMOLA, Osarenkhoe O. OSEMWEGIE, Stephen O. OWA, Samuel B. ORISAJO, Evbuomwan IKPONMWOSA, Elizabeth T. ALORI
    2021, 20(10): 2706-2715.  DOI: 10.1016/S2095-3119(21)63609-2
    Abstract ( )   PDF in ScienceDirect  
    The occurrence of entomopathogenic nematodes (EPNs) in arable soil samples from Nigeria was investigated using Baermann extraction tray and insect-bait (White’s trap) techniques.  Isolates were tested for infectivity using the larvae of Galleria mellonella (greater moth) and Tenebrio molitor (mealworm).  The study revealed a new species of Heterorhabditis (MT371593) in soil samples that were randomly collected from an arable farmland cultivated with cassava TMS-30572 at the Teaching and Research Farm of Landmark University, Nigeria.   Amplification of the internal transcribed spacer region (ITS) of the ribosomal DNA produced a nucleotide sequence of 933 base pairs (bp).  A BLASTN search of GenBank showed that the sequence of the Nigerian isolate is identical at 99% similarity to that of Heterorhabditis sp. from Thailand.   Infectivity test of the isolate showed 100% mortality against T. molitor larvae within 48 h of exposure while only 80% mortality was recorded for G. mellonella after 1 week of exposure.  This is the first account of Heterorhabditis sp. in Nigeria.  The varying degrees of infectivity against mealworm and greater moth observed in this study proved that the Nigerian isolate of Heterorhabditis sp. could potentially be an attractive option in the management of insect pests of cash crops.
    Egg tanning improves the efficiency of CRISPR/Cas9-mediated mutant locust production by enhancing defense ability after microinjection
    ZHANG Ting-ting, WEN Ting-mei, YUE Yang, YAN Qiang, DU Er-xia, FAN San-hong, Siegfried ROTH, LI Sheng, ZHANG Jian-zhen, ZHANG Xue-yao, ZHANG Min
    2021, 20(10): 2716-2726.  DOI: 10.1016/S2095-3119(21)63736-X
    Abstract ( )   PDF in ScienceDirect  
    The mutant efficiency and hatching ratio are two key factors that significantly affect the construction of genome-modified mutant insects.  In the construction of CRISPR/Cas9-mediated dsLmRNase2–/–mutant locusts, we found that the tanned eggs which experienced a 20-min contact with the oocyst exhibited a higher success rate compared to fresh newly-laid eggs that were less tanned.  However, the heritable efficiency of the dsLmRNase2 deletion to the next generation G1 progeny was similar between adults derived from the tanned or less tanned engineered eggs.  Further, the similar effective mutant ratios in the normally developed eggs and G0 adults of tanned and less tanned eggs also indicated that tanning did not reduce the absolute mutation efficiency induced by CRISPR/Cas9.  Moreover, we found that the syncytial division period, which was longer than the time for tanning, conferred a window period for microinjection treatment with efficient mutation in both tanned and less tanned eggs.  We further found that tanned eggs exhibited a higher hatching rate due to a reduced infection rate following microinjection.  Both the anti-pressure and ultrastructure analyses indicated that the tanned eggs contained compressed eggshells to withstand increased external pressure.  In summary, tanned eggs possess stronger defense responses and higher efficiency of genome editing, providing an improved model for developing Cas9-mediated gene editing procedures in locusts.
    Optimization of the sex pheromone-based method for trapping field populations of Phthorimaea operculella (Zeller) in South China
    YAN Jun-jie, MEI Xiang-dong, FENG Jia-wen, LIN Zhi-xu, Stuart REITZ, MENG Rui-xia, GAO Yu-lin
    2021, 20(10): 2727-2733.  DOI: 10.1016/S2095-3119(20)63320-2
    Abstract ( )   PDF in ScienceDirect  
    Despite the identification of the potato tuber moth Phthorimaea operculella (Zeller) sex pheromone, no effective application based on this pheromone has yet been developed and evaluated.  This study investigated the effect of pheromone lures, trap densities, heights of trap deployment, and pheromone doses in Yunnan, China, for the purpose of increasing the control efficiency of P. operculella and improving the application of pheromone technology in the field.  The results showed that lures made of corn oil and red PVC pipes attracted the highest number of moths (11.73±1.90 per trap per day).  Sex pheromone loading of 100 μg was optimal for trapping moths, but higher doses of pheromone inhibited attraction.  The density of traps did not affect capture rates; therefore, the optimum trap density was 30–40 traps ha–1.  The optimum height of trap deployment was not above the height of the plant canopy.  This study provides technical details necessary for the monitoring and control of potato tuber moth using sex pheromones.
    Animal Science · Veterinary Medicine
    Integration of association and computational methods reveals functional variants of LEPR gene for abdominal fat content in chickens
    LI Yu-dong, WANG Wei-jia, LI Zi-wei, WANG Ning, XIAO Fan, GAO Hai-he, GUO Huai-shun, LI Hui, WANG Shou-zhi
    2021, 20(10): 2734-2748.  DOI: 10.1016/S2095-3119(20)63575-4
    Abstract ( )   PDF in ScienceDirect  
    Leptin receptor (LEPR) plays a vital role in obesity in humans and animals.  The objective of this study is to assess LEPR functional variants for chicken adipose deposition by integration of association and in-silico analysis using a unique chicken population, the Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF).  Five online bioinformatics tools were used to predict the functionality of the single nucleotide polymorphisms (SNPs) in coding region.  Further, the possible structure–function relationship of high confidence SNPs was determined by bioinformatics analyses, including the conservation and stability analysis based on amino acid residues, prediction of protein ligand-binding sites, and the superposition of protein tertiary structure.  Meanwhile, we analyzed the association between abdominal fat traits and 20 polymorphisms of chicken LEPR gene.  The integrated results showed that rs731962924 (N867I) and rs13684622 (C1002R) could lead to striking changes in the structure and function of proteins, of which rs13684622 (C1002R) was significantly associated with abdominal fat weight (AFW, P=0.0413) and abdominal fat percentage (AFP, P=0.0260) in chickens.  Therefore, we are of the opinion that rs13684622 (C1002R) may be an essential functional SNP affecting chicken abdominal fat deposition, and potentially applied to improvement of broiler abdominal fat in molecular marker-assisted selection (MAS) program.  Additionally, the coupling of association with computer electronic predictive analysis provides a new avenue to identify important molecular markers for breeders.
    Follicle-stimulating hormone is expressed in ovarian follicles of chickens and promotes ovarian granulosa cell proliferation
    BI Yu-lin, YANG Shu-yan, WANG Hai-yan, CHANG Guo-bin, CHEN Guo-hong
    2021, 20(10): 2749-2757.  DOI: 10.1016/S2095-3119(21)63606-7
    Abstract ( )   PDF in ScienceDirect  
    Follicle-stimulating hormone (FSH), an important hypothalamic-pituitary-gonadal axis (HPG) hormone, is secreted by the pituitary gland.  This study confirms that FSH is expressed in chicken follicles at different stages, and positive FSHβ mRNA signals were stronger (P<0.05) in granulosa cells than in oocytes.  The 369 bp coding sequence of FSHβ in ovaries is 100% identical to that in the pituitary gland.  The experiment in vitro revealed that the ovary possessed FSH secretory capacity.  Further, FSHβ mRNA was significantly upregulated (P<0.05) in follicles and significantly higher (P<0.05) than that in the pituitary gland by approximately 2–23 times with the development.  The number of granulosa cells decreased significantly (P<0.05) in the cells with siRNA treatment, confirming that the ovarian FSH could promote granulosa cell proliferation.  This view was supported by cell cycle analysis and CCND2 and CCNE2 expression.  Further research indicated that no difference (P>0.05) was observed between the number of granulosa cells treated with FSHβ siRNA and in exogenous FSH. However, the number of granulosa cells without FSHβ siRNA transfection was significantly higher (P<0.05) for exogenous FSH.  This finding suggests that the proliferative effect of exogenous FSH on ovarian granulosa cells depend on endogenous FSH.  This study demonstrated that the FSH gene was expressed in chicken follicles and promoted ovarian granulosa cell proliferation, which enriched the theory on HPG axis.
    Agro-ecosystem & Environment
    Changes in organic C stability within soil aggregates under different fertilization patterns in a greenhouse vegetable field
    LUAN Hao-an, YUAN Shuo, GAO Wei, TANG Ji-wei, LI Ruo-nan, ZHANG Huai-zhi, HUANG Shao-wen
    2021, 20(10): 2758-2771.  DOI: 10.1016/S2095-3119(21)63646-8
    Abstract ( )   PDF in ScienceDirect  
    Knowledge of the stability of soil organic C (SOC) is vital for assessing SOC dynamics and cycling in agroecosystems.  Studies have documented the regulatory effect of fertilization on SOC stability in bulk soils. However, how fertilization alters organic C stability at the aggregate scale in agroecosystems remains largely unclear.  This study aimed to appraise the changes of organic C stability within soil aggregates after eight years of fertilization (chemical vs. organic fertilization) in a greenhouse vegetable field in Tianjin, China.  Changes in the stability of organic C in soil aggregates were evaluated by four methods, i.e., the modified Walkley-Black method (chemical method), 13C NMR spectroscopy (spectroscopic method), extracellular enzyme assay (biological method), and thermogravimetric analysis (thermogravimetric method).  The aggregates were isolated and separated by a wet-sieving method into four fractions: large macroaggregates
    (>2 mm), small macroaggregates (0.25–2 mm), microaggregates (0.053–0.25 mm), and silt/clay fractions (<0.053 mm).  The results showed that organic amendments increased the organic C content and reduced the chemical, spectroscopic, thermogravimetric, and biological stability of organic C within soil aggregates relative to chemical fertilization alone.  Within soil aggregates, the content of organic C was the highest in microaggregates and decreased in the order microaggregates>macroaggregates>silt/clay fractions.  Meanwhile, organic C spectroscopic, thermogravimetric, and biological stability were the highest in silt/clay fractions, followed by macroaggregates and microaggregates.  Moreover, the modified Walkley-Black method was not suitable for interpreting organic C stability at the aggregate scale due to the weak correlation between organic C chemical properties and other stability characteristics within the soil aggregates.  These findings provide scientific insights at the aggregate scale into the changes of organic C properties under fertilization in greenhouse vegetable fields in China.
    Regional distribution of wheat yield and chemical fertilizer requirements in China
    XU Xin-peng, HE Ping, CHUAN Li-min, LIU Xiao-yan, LIU Ying-xia, ZHANG Jia-jia, HUANG Xiao-meng, QIU Shao-jun, ZHAO Shi-cheng, ZHOU Wei
    2021, 20(10): 2772-2780.  DOI: 10.1016/S2095-3119(20)63338-X
    Abstract ( )   PDF in ScienceDirect  
    Quantification of currently attainable yield and fertilizer requirements can provide detailed information for assessing the food supply capacity and offer data support for agricultural decision-making.  Datasets from a total of 5 408 field experiments were collected from 2000 to 2015 across the major wheat production regions in China to analyze the spatial distribution of wheat yield, the soil nutrient supply capacity (represented by relative yield, defined as the ratio of the yield under the omission of one of nitrogen (N), phosphorus (P) and potassium (K) to the yield under the full NPK fertilizer application), and N, P and K fertilizer requirements by combining the kriging interpolation method with the Nutrient Expert Decision Support System for Wheat.  The results indicated that the average attainable yield was 6.4 t ha−1, with a coefficient of variation (CV) of 24.9% across all sites.  The yields in North-central China (NCC) and the northern part of the Middle and Lower reaches of the Yangtze River (MLYR) were generally higher than 7 t ha−1, whereas the yields in Southwest China (SWC), Northeast China (NEC), and the eastern part of Northwest China (NWC) were usually less than 6 t ha−1.  The precentage of area having a relative yield above 0.70, 0.85, and 0.85 for N, P, and K fertilizers accounted for 52.3, 74.7, and 95.9%, respectively.  Variation existed in N, P, and K fertilizer requirements, with a CV of 24.8, 23.9, and 29.9%, respectively, across all sites.  More fertilizer was needed in NCC and the northern part of the MLYR than in other regions.  The average fertilizer requirement was 162, 72, and 57 kg ha−1 for N, P2O5, and K2O fertilizers, respectively, across all sites.  The incorporation of the spatial variation of attainable yield and fertilizer requirements into wheat production practices would benefit sustainable wheat production and environmental safety.
    Increased ammonification, nitrogenase, soil respiration and microbial biomass N in the rhizosphere of rice plants inoculated with rhizobacteria
    ZHANG Jun-hua, HUANG Jing, Sajid HUSSAIN, ZHU Lian-feng, CAO Xiao-chuang, ZHU Chun-quan, JIN Qian-yu, ZHANG Hui
    2021, 20(10): 2781-2796.  DOI: 10.1016/S2095-3119(20)63454-2
    Abstract ( )   PDF in ScienceDirect  
    Azospirillum brasilense and Pseudomonas fluorescens are well-known plant growth promoting rhizobacteria.  However, the effects of A. brasilense and P. fluorescens on the N cycles in the paddy field and rice plant growth are little known.  This study investigated whether and how A. brasilense and P. fluorescens contribute to the N transformations and N supply capacities in the rhizosphere, and clarified the effects of A. brasilense and P. fluorescens on the N application rate in rice cultivation.  Inoculations with A. brasilense and P. fluorescens coupled with N application rate trials were conducted in the paddy field in 2016 and 2017.  The inoculations of rice seedlings included four treatments: sterile saline solution (M0), A. brasilense (Mb), P. fluorescens (Mp), and co-inoculation with a mixture of A. brasilense and P. fluorescens (Mbp).  The N application rate included four levels: 0 kg N ha–1 (N0), 90 kg N ha–1 (N90), 180 kg N ha–1 (N180), and 270 kg N ha–1 (N270).  The results indicated that the Mbp and Mp treatments significantly enhanced the ammonification activities in the rhizosphere compared with the M0 treatment, especially for higher N applications, while the Mbp and Mb treatments greatly enhanced the nitrogenase activities in the rhizosphere compared with the M0 treatments, especially for lower N applications.  Azospirillum brasilense and P. fluorescens did not participate in the nitrification processes or the denitrification processes in the soil.  The soil respiration rate and microbial biomass N were greatly affected by the interactions between the rhizobacteria inoculations and the N fertilizer applications.  In the Mbp treatment, N supply capacities and rice grain yields showed no significant differences among the N90, N180, and N270 applications.  The N application rate in the study region can be reduced to 90 kg N ha–1 for  rice seedlings co-inoculated with a mixture of A. brasilense and P. fluorescens.
    Bacterial diversity and community composition changes in paddy soils that have different parent materials and fertility levels
    MA Xin-ling, LIU Jia, CHEN Xiao-fen, LI Wei-tao, JIANG Chun-yu, WU Meng, LIU Ming, LI Zhong-pei
    2021, 20(10): 2797-2806.  DOI: 10.1016/S2095-3119(20)63364-0
    Abstract ( )   PDF in ScienceDirect  
    Parent materials and the fertility levels of paddy soils are highly variable in subtropical China.  Bacterial diversity and community composition play pivotal roles in soil ecosystem processes and functions.  However, the effects of parent material and fertility on bacterial diversity and community composition in paddy soils are unclear.  The key soil factors driving the changes in bacterial diversity, community composition, and the specific bacterial species in soils that are derived from different parent materials and have differing fertility levels are unknown.  Soil samples were collected from paddy fields in two areas with different parent materials (quaternary red clay or tertiary sandstone) and two levels of fertility (high or low).  The variations in bacterial diversity indices and communities were evaluated by 454 pyrosequencing which targeted the V4–V5 region of the 16S rRNA gene.  The effects of parent material and fertility on bacterial diversity and community composition were clarified by a two-way ANOVA and a two-way PERMANOVA.  A principal coordinate analysis (PCoA), a redundancy analysis (RDA), and multivariate regression trees (MRT) were used to assess changes in the studied variables and identify the factors affecting bacterial community composition.  Co-occurrence network analysis was performed to find correlations between bacterial genera and specific soil properties, and a statistical analysis of metagenomic profiles (STAMP) was used to determine bacterial genus abundance differences between the soil samples.  The contributions made by parent material and soil fertility to changes in the bacterial diversity indices were comparable, but soil fertility accounted for a larger part of the shift in bacterial community composition than the parent material.  Soil properties, especially soil texture, were strongly associated with bacterial diversity.  The RDA showed that soil organic carbon (SOC) was the primary factor influencing bacterial community composition.  A key threshold for SOC (25.5 g kg–1) separated low fertility soils from high fertility soils.  The network analysis implied that bacterial interactions tended towards cooperation and that copiotrophic bacteria became dominant when the soil environment improved.  The STAMP revealed that copiotrophic bacteria, such as Massilia and Rhodanobacter, were more abundant in the high fertility soils, while oligotrophic bacteria, such as Anaerolinea, were dominant in low fertility soils.  The results showed that soil texture played a role in bacterial diversity, but nutrients, especially SOC, shaped bacterial community composition in paddy soils with different parent materials and fertility levels.
    Agricultural Economics and Management
    Food safety inspection and the adoption of traceability in aquatic wholesale markets: A game-theoretic model and empirical evidence
    JIN Cang-yu, Retsef LEVI, LIANG Qiao, Nicholas RENEGAR, ZHOU Jie-hong
    2021, 20(10): 2807-2819.  DOI: 10.1016/S2095-3119(21)63624-9
    Abstract ( )   PDF in ScienceDirect  
    Supply chain traceability is key to reduce food safety risks, since it allows problems to be traced to their sources.  Moreover, it allows regulatory agencies to understand where risk is introduced into the supply chain, and offers a major disincentive for upstream agricultural businesses engaging in economically motivated adulteration.  This paper focuses on the aquatic supply chain in China, and seeks to understand the adoption of traceability both through an analytical model, and empirical analysis based on data collected through an extensive (largest ever) field survey of Chinese aquatic wholesale markets.  The field survey includes 76 managers and 753 vendors, covering all aquatic wholesale markets in Zhejiang and Hunan provinces.  The analytical and empirical results suggest that the adoption of traceability among wholesale market vendors is significantly associated with inspection intensity, their individual history of food safety problems, and their risk awareness.  The effect of inspection intensity on traceability adoption is stronger in markets which are privately owned than in markets with state/collective ownership.  The analysis offers insights into the current state of traceability in China.  More importantly, it suggests several hypothesized factors that might affect the adoption of traceability and could be leveraged by regulatory organizations to improve it.
    Assessing the impact of non-governmental organization’s extension programs on sustainable cocoa production and household income in Ghana
    2021, 20(10): 2820-2836.  DOI: 10.1016/S2095-3119(21)63607-9
    Abstract ( )   PDF in ScienceDirect  
    Globally, cocoa is famous for the production of chocolates and beverages. However, it also serves as a source of raw material for the manufacturing of high-quality cosmetic and pharmaceutical products.  Due to its high demand, cocoa is regarded as a major commodity for poverty alleviation in deprived cocoa farming communities.  Government has therefore instigated relevant measures to address issues facing the sector by investing in extension programs.  These programs act as information dissemination tools for teaching modern farming technologies and enhancing learning among farmers.  This study highlighted the effects of the Cocoa Life Project (CLP) by Cooperative for Assistance and Relief Everywhere (CARE) International on farm productivity and income of 200 cocoa farmers in three districts of the Eastern Region, Ghana.  Regression on covariates, Heckman’s treatment effects model, and propensity scores were used to test the robustness of the estimates.  A positive association between extension program participation, farm productivity, and household income was discovered.  Specifically, after correcting for selection bias, the estimated results of the Heckman’s model showed that the extension program significantly increased participating farmers’ cocoa yield by 14.3%.  The effects on total farm income showed a significant increase of 25.1 and 42.9%, respectively from regression on propensity scores and the Heckman’s model.  Across all three models, program participation led to an increase in total household income by 46.1, 31.7, and 69.3%, respectively.  Other variables such as farming characteristics, institutional and demographic factors affected farmers’ income, depending on the estimation method used.  This study reiterated the supporting role played by extension programs in enhancing cocoa production and increasing household income in Ghana.  Conclusively, government and development partners should invest in extension programs by providing enough logistics, training qualified agents, and creating a conducive atmosphere to support learning and technology adoption.