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Yan Y.,CAS Shenyang Institute of Applied Ecology | Yan Y.,ShenYang Agricultural University | He H.,CAS Shenyang Institute of Applied Ecology | Zhang X.,CAS Shenyang Institute of Applied Ecology | And 8 more authors.
Canadian Journal of Soil Science | Year: 2012

The response of soil organic matter (SOM) dynamics to long-term fertilization may be deduced from changes in the accumulation and distribution of different soil organic carbon (SOC) and nitrogen (N) pools. The SOC and N in particle-size fractions were therefore measured to assess the influences of pig manure and synthetic fertilizer application on the characteristics of these pools. A long-term fertilization experiment, established in 1979 in the Mollisol area (Gongzhuling, China) was used for this study. Composite soil samples (0-20 cm) were collected in 2005 from 12 treatment plots that had received annual applications of pig manure, synthetic fertilizers or combinations of both. Soils were fractionated into fine clay (<0.2 μm), coarse clay (0.2-2 μm), silt (2-50 μm), fine sand (50-250 μm) and coarse sand (250-2000 μm) and then SOC and N contents in each particle-size fraction were measured. Although most of the SOC and N were associated with clay and silt fractions, the large proportion of silt in the soil mass played a key role in the retention of SOC and N. The application of pig manure alone increased accumulation of SOC and N in each particle-size fraction, but preferential enrichment was found in the coarse sand fraction. This indicates that pig manure is efficient in restoring SOM in the temperate Chinese Mollisol under a tilled maize (Zea mays L.) monocropping system and having a long frozen period in winter. The application of synthetic fertilizers had no clear effect on SOC and N accumulation or their distribution in particle-size fractions. However, the combined application of pig manure and synthetic fertilizers enhanced the accumulation of SOC and N in all particle-size fractions, and led to a shift of SOC and N from fine to coarse particles. We extended the hierarchy model for SOC protection to consider a shift in SOC accumulation from fine to coarse particles, depending on the initial SOC content of the specific soil. The findings reveal a clear positive interaction between pig manure and synthetic fertilizers that may improve the quantity of SOM in the temperate Chinese Mollisol. Source

Wang K.,International Rice Research Institute | Wang K.,China National Rice Research Institute | Qiu F.,International Rice Research Institute | Qiu F.,Liaoning Rice Research Institute | And 3 more authors.
Plant Genetic Resources: Characterisation and Utilisation | Year: 2014

The characterization of genetic diversity and structure for improved cultivated varieties/elite lines is tremendously important to assist breeders in parental selection for inbred and hybrid breeding and heterotic group construction. In this study, a total of 737 improved indica varieties/lines developed recently and/or widely used by present indica breeding programmes worldwide were genotyped with a 384-single-nucleotide polymorphism assay. Model-based population structure analysis revealed the presence of two major groups with six subgroups (SGs), wherein no clear correlation was found between the groups/SGs and breeding programmes or geographical origin of the accessions. Over half of the accessions (51.8%) appeared to have less than 0.6 memberships assigned to any one of the six model-based groups, highlighting the wide range of gene flow within improved indica varieties/lines and the genetic integration of valuable alleles shared by ancestries among improved high-yielding varieties/lines through germplasm exchanges. Distance-based clustering revealed that Latin-American cultivated indica lines have tended to form their own ecological cline, which could serve as a potential heterotic ecotype for hybrid rice breeding, although they are still closely related to Asian indica lines. African cultivated indica lines, on the other hand, have not yet formed their own ecological cline. It was also observed that the most well-known hybrid rice parents, Zhenshan97B and Minghui63, were unexpectedly clustered in the same SG with a relatively narrow genetic distance, which suggests that a significant genetic distance between parents is not a prerequisite for all elite hybrid rice lines with high heterosis. © NIAB 2014. Source

Wang K.,International Rice Research Institute | Wang K.,China National Rice Research Institute | Wang K.,Yahua Seed Research Institute | Qiu F.,International Rice Research Institute | And 4 more authors.
Theoretical and Applied Genetics | Year: 2015

Key message: Four heterotic groups were identified for tropicalindicarice germplasm to develop hybrid rice in the tropics based on two studies.Abstract: Heterotic groups are of fundamental importance in hybrid crop breeding. This study investigated hybrid yield, yield heterosis and combining ability within and among groups based on genetic distance derived from single-nucleotide polymorphism markers. The main objectives of the study were to (1) evaluate the magnitude of yield heterosis among marker-based groups, (2) identify possible heterotic groups for tropical indica hybrid rice, and (3) validate heterotic patterns concluded from a previous study. Seventeen rice parents selected from improved indica germplasm from the tropics with high genetic divergence and 136 derived hybrids were evaluated in five environments. The hybrids had more yield than their parents with an average of 24.1 % mid-parent heterosis. Genotype × environment interaction was the major factor affecting variations in yield and yield heterosis, which raised a necessity and a challenge to develop heterotic rice hybrid adapted to different regions and seasons in the tropics. Yield, yield heterosis and combining ability were significantly increased in inter-group than in intra-group hybrids. Four heterotic groups and three promising hybridization patterns, which could be used in tropical hybrid rice breeding, were identified based on marker-based grouping, yield and yield heterosis analyses in the two studies. The study reveals that molecular markers analysis can serve as a basis for assigning germplasm into heterotic groups and to provide guidelines for parental selection in hybrid rice breeding. © 2014, Springer-Verlag Berlin Heidelberg. Source

Chen Y.,CAS Shenyang Institute of Applied Ecology | Chen Y.,Liaoning Rice Research Institute | Zhang X.,CAS Shenyang Institute of Applied Ecology | Zhang X.,Chinese Academy of Sciences | And 6 more authors.
Journal of Soils and Sediments | Year: 2010

Purpose: It is known that soil organic matter (SOM) dynamics are sensitive to fertilizations, but it is different from soil to soil. It is unclear how the long-term applications of organic manure and mineral fertilizers impact the accumulation and distribution of soil organic carbon (SOC) and total nitrogen (TN) especially in soil aggregate fractions of Chinese Mollisols, which have been intensively cultivated for decades under maize monocropping and conventional tillage ways. Thereby, the research of this kind is very important for the sustainable use of agricultural land in China, where land resources are extremely limited for its huge population. The objectives of this study were to identify how the long-term fertilization treatments would affect the aggregate, SOC and TN distribution pattern in the Chinese Mollisol, and how soil aggregation contribute to the storage and stabilization process of SOC and TN. Materials and methods: Soils were sampled in April 2005 from a long-term experiment site established in 1979. Six treatments were selected as follows: CK (zero fertilizer), NPK (mineral fertilizers), M1 (organic manure at lower level), M1NPK (combination of M1 and NPK), M2 (organic manure at higher level) and M2NPK (combination of M2 and NPK). Four aggregate fractions, i.e., large macroaggregate (>2,000 μm), small macroaggregate (250-2,000 μm), microaggregate (53-250 μm) and silt + clay fraction (<53 μm), respectively, were obtained by wet sieving. SOC and TN in bulk soils and aggregates were analyzed using a C/N/H/S-analyzer (Vario ElementarIII, Germany). Results and discussion: The small macroaggregate was the most abundant component in the soils, accounting for 46.1-60.2% of the dry soil mass and about 50% of SOC and TN. The small macroaggregate proportion decreased while large macroaggregate percentage increased significantly after organic manure treatment. However, mineral fertilizers application enlarged the proportion of microaggregate and silt + clay fraction. Consequently, SOC and TN contents in all the four aggregates increased remarkably with organic manure application, whereas mere mineral fertilizers addition did not affect SOC and TN content significantly. The combination of NPK with the higher level of organic manure was more effective in improving SOC and TN accumulation than organic manure application alone. Moreover, organic manure application tended to decrease C/N ratios, in general, and higher C/N ratios in >53 μm fractions than in others, suggesting that SOC in the larger fractions is relatively fresh or little altered by microorganisms, whereas, the SOC associated with <53 μm fraction is more decomposed and relative aged. However, the higher enrichment factor for N (EN) than for C (EC) in <53 μm fraction indicates a preferential depletion of labile SOC and relative accumulation of stable SOC pools in the finest fraction. Conclusions: The long-term application of organic manure generally facilitated aggregation processes and then improved the quantity and quality of SOM in the Mollisol, whereas the long-term mineral fertilizers application generally resulted in the de-aggregation effect. The combination of organic manure and mineral fertilizers was a better way to further enhance the sequestration of SOC and improve SOM quality by aggregation compared to the pure organic manure. It is concluded that when increasing organic input, physical protection plays a major role for the sequestration of the increased SOC in the Chinese Mollisol. However, when SOC is depleted under a certain management practice, it will happen preferentially in the physical protected SOC in large aggregates. This study has great implications for better understanding SOC and N dynamics as affected by long-term fertilization. © 2009 Springer-Verlag. Source

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