Search

Purple soil is a type of global soil that is referred to by various names in different countries, which makes it difficult to understand, utilize, and ameliorate purple soil internationally. Soil Taxonomy (ST) and the World Reference Base for Soil Resources (WRB) are the most widely used soil classification systems in the world. The aim of this study was to clarify the classification of purple soil in ST and the WRB and to establish a reference between different classification systems of purple soil. Therefore, based on the current principles and methods of the ST and WRB systems, 18 typical purple soil profiles in the eastern Sichuan Basin were identified, retrieved, and classified. Then, the soil units of the WRB were compared with those of ST and the Chinese Soil Taxonomy (CST). The results revealed that the 18 typical purple soil profiles could be classified into three soil orders, four soil group orders, and seven soil subgroups in ST and four reference soil groups (RSGs) in the WRB; each profile had its own unique principal and supplementary qualifier combinations within the soil units. It was found that when compared with the ST system, the WRB and CST systems had stronger abilities to distinguish purple soil. In addition, the WRB system was able to more comprehensively consider soil characteristics such as soil layer thickness, ferric horizon, soil color, texture mutations, and carbonate through qualifiers. However, the CST system added diagnostic characteristics, such as the lithologic characteristics of purplish sandstones and shales and the ferric properties and alic properties at the soil group and subgroup levels, which enhanced the differentiation ability of the purple soil at the subgroup level. [ABSTRACT FROM AUTHOR]

Soil aggregates are the basic units of soil, which regulate soil carbon cycling and nutrient availability through the protective effect of soil aggregates on soil organic matter. It is still uncertain whether larger aggregates are more conducive to soil nutrient availability in red soil. This study explored the regulation of soil aggregates on soil nutrient availability by studying the distribution of soil aggregates, nutrient concentrations, nutrient availability and organo-mineral bonds in soil aggregates in a low-productivity Chinese fir forest, in south China. We sampled the 0–10 cm soil with nine repeated plots and analyzed the soil aggregate structure, total nutrients, available nutrients and organo-mineral bonds of soil aggregates. The results showed that the contribution of >2 mm soil aggregates to soil nutrients was highest, because the mass of >2 mm soil aggregates accounted for about 50% of the total mass of aggregates and was much higher than that of other aggregates. The availability (available nutrient/total nutrient) of nitrogen, phosphorus and potassium increased with decreases in soil aggregate size, indicating that soil aggregates with a larger particle size were more averse to nutrient availability. Strong organo-mineral bonds accounted for more than 80% of the total organo-mineral bonds in the soil aggregates of each size, and the proportion of weak organo-mineral bonds in the soil aggregate increased with decreases in the soil aggregate size. There was a significant negative correlation between the size of soil aggregates and the proportion of weak organo-mineral bonds in soil aggregates. The availability of carbon, nitrogen, phosphorus and potassium in soil aggregates was positively correlated with the proportion of weak organo-mineral bonds. These results suggest that Fe/Al oxides may play an important role in regulating nutrient availability, especially in red soil. A higher proportion of strong organo-mineral bonds in larger soil aggregates may exert a stronger negative effect on the accessibility of microorganisms to organic matter and result in a lower nutrient availability. In conclusion, this study shows that larger-sized soil macroaggregates may exert a negative effect on nutrient availability, owing to a higher proportion of strong binding bonds, which can better prevent microorganisms from mineralizing organic matter into effective nutrients in red soil. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Poor soil quality is affected by salinity, which limits land productivity and sustainable agricultural development in coastal China. Hence, it is essential to choose suitable and efficient approaches to revitalize coastal saline soil quality and improve agricultural productivity. Biochar and polyacrylamide (PAM) have been widely applied as soil amendments to enhance soil structure, but the interactive effects of biochar and PAM on rice growth are unclear. The experiment described in this study was conducted over five consecutive growing seasons (from 2016 to 2020) with biochar (at 0, 32, and 79 t/hm2) and PAM (at 0, 0.6, and 1.6 t/hm2) applications to study the effects of amendments on soil properties, rice photosynthesis, and rice yield in coastal saline land. The soil property results showed that wheat straw biochar and PAM lowered soil total salt and bulk density, but increased the soil organic matter (SOM), mean weight diameter of water-stable aggregates (MWD), and macroaggregate (> 0.25 mm) content. The application of either biochar or PAM increased the rice net photosynthetic rate, transpiration rate, and stomatal conductance. The combined application of 32 t/hm2 biochar + 0.6 t/hm2 PAM increased the net photosynthetic rate by 26.0% and the transpiration rate by 24.8% relative to the control. The application of 32 t/hm2 biochar and 1.6 t/hm2 PAM significantly increased the rice grain yield. The path analysis model showed that spikelets per panicle and canopy gross photosynthesis had strong and significant positive effects on grain yield, whereas soil total salt had a negative effect on grain yield. The combined application of 32 t/hm2 biochar + 0.6 t/hm2 PAM was identified as the most effective for rice growth. Biochar and PAM amendments at an optimal level may enhance soil properties by reducing salinity. These findings indicate that biochar and PAM have the potential to remediate coastal saline soil quality and the environment, which would simultaneously increase the sustainable use of coastal land resources and food production to preserve the ecological environment. [ABSTRACT FROM AUTHOR]

An extensive knowledge of the temporal variability of soil fertility parameters and how this variation affects the environment is imperative to a wide range of disciplines within agricultural science for optimal crop production and ecosystem preservation. This paper examines the temporal variability of soil pH, organic matter (OM), cation exchange capacity (CEC), total nitrogen (TN), total phosphorus (TP), available phosphorus (PAv), and available potassium (KAv) on Cambosols (Entisols) (n =179) and Anthrosols (Inceptisols) (n =95) in Zhangjiagang County, China from 1980 to 2004. Nutrient input was monitored from 1983 to 2004. Annual N fertilizer rates were significantly different during three periods (1983–1989, 1989–1999, 1999–2004), where annual rates increased significantly after 1989 and then decreased after 1999. Annual P fertilizer rates were significantly different during two periods (1983–1993, 1993–2004) where annual rates increased after 1993. No change was found in K fertilizer rates. Soil pH marginally increased by 0.14 units in Cambosols, but significantly decreased by 1.02 units in Anthrosols. OM, CEC, and TN increased in both soil orders an average of 2.15gkg−1, 1.6cmolkg−1, and 0.21gkg−1, respectively. TP decreased in Anthrosols by 70mgkg−1, PAv increased in Cambosols by 4.83mgkg−1, and KAv decreased in Cambosols by 15mgkg−1. Fertilizer input rates are causing nutrient imbalances, contributing to acidification in Anthrosols, and decreasing C/N ratios. Nutrient loading of N and deficiency of K is also a potential problem in the area. Efforts should be made to readjust soil nutrient inputs to reach an optimal, sustainable level. [Copyright &y& Elsevier]

From the latest Cretaceous (late Campanian to Maastrichtian, ~75–66 Ma) to the earliest Paleogene, fluctuations in greenhouse climate, inferred primarily from marine sediments, have been linked to volcanism, the Chicxulub asteroid impact, and the Cretaceous-Paleogene (K-Pg) mass extinction. In this paper, we summarize terrestrial climate records in mid-latitude East Asia during the latest Cretaceous and across the K-Pg boundary, based on a multi-proxy approach from the geochronologically well-constrained Sifangtai and Mingshui formations (SMF), accessed by scientific drilling of the Songliao Basin in northeastern China. Evolution of sedimentary environments is characterized by five depositional units of fluvial-deltaic-lacustrine facies. Development of four types of paleosols, including Inceptisols, Aridisols, Vertisols and Alfisols, is interpreted to primarily reflect climatic changes. Correlations among sedimentary facies, paleosol features, illite chemistry index, chemical index of alteration, as well as stable and clumped isotopes of pedogenic carbonates and clay minerals of the SMF validate their reliability for paleoclimate reconstruction, and indicate significant fluctuations in terrestrial climate and sedimentary environment. During global warming intervals possibly triggered by volcanism (e.g. ~69.5–68.5 Ma), the Songliao Basin experienced a warmer and wetter climate with stronger terrestrial chemical weathering and more monsoon-derived moisture sourced from the Pacific. In contrast, during global cooling intervals (e.g. ~70.5–69.5 Ma and ~ 68.5–66.5 Ma), the SMF record a cooler and drier climate with less intensive chemical weathering and more westerlies-derived moisture. Across the K-Pg boundary, dramatic changes in land temperatures and hydroclimate correspond to the latest Maastrichtian warming episode (~66.4–66.1 Ma), the transient cooling preceding the K-Pg boundary (~66.1–66.0 Ma), and the earliest Paleogene warming interval (~66.0–65.7 Ma). Temporal correlation of weathering index changes with the Deccan Traps volcanism suggests that volcanism and subsequent intensified weathering played a major role for climatic changes across the K-Pg boundary. The integrated records of sedimentological and geochemical datasets from the Songliao Basin robustly demonstrate that the terrestrial climate of mid-latitude East Asia responded strongly to greenhouse climate changes and to the catastrophic geological events from the latest Cretaceous to the earliest Paleogene. [ABSTRACT FROM AUTHOR]

Soil microbial communities are affected by interactions between agricultural management (e.g., fertilizer) and soil compartment, but few studies have considered combinations of these factors. We compared the microbial abundance, diversity and community structure in two fertilizer dose (high vs. low NPK) and soil compartment (rhizosphere vs. bulk soils) under 6-year fertilization regimes in a continuous garlic cropping system in China. The soil contents of NO3– and available K were significantly higher in bulk soil in the high-NPK. The 16S rRNA gene-based bacterial and archaeal abundances were positively affected by both the fertilizer dose and soil compartment, and were higher in the high-NPK fertilization and rhizosphere samples. High-NPK fertilization increased the Shannon index and decreased bacterial and archaeal richness, whereas the evenness was marginally positively affected by both the fertilizer dose and soil compartment. Soil compartment exerted a greater effect on the bacterial and archaeal community structure than did the fertilization dose, as demonstrated by both the nonmetric multidimensional scaling and redundancy analysis results. We found that rhizosphere effects significantly distinguished 12 dominant classes of bacterial and archaeal communities, whereas the fertilizer dose significantly identified four dominant classes. In particular, a Linear Effect Size analysis showed that some taxa, including Alphaproteobacteria, Rhizobiales, Xanthomonadaceae and Flavobacterium, were enriched in the garlic rhizosphere of the high-NPK fertilizer samples. Overall, the fertilizer dose interacted with soil compartment to shape the bacterial and archaeal community composition, abundance, and biodiversity in the garlic rhizosphere. These results provide an important basis for further understanding adaptive garlic-microbe feedback, reframing roots as a significant moderating influence in agricultural management and shaping the microbial community. [ABSTRACT FROM AUTHOR]

Farmers are increasingly planting vegetables during the winter fallow period in the double-rice growing area of Guangdong Province, southern China. The intensified winter crop rotation system (rice-rice-vegetable, RRV) may improve the annual planting benefit and change the soil fertility. To address this, yields, biomass, and profitability of each crop in the RRV, relative to the traditional rice-rice-fallow system (RRF), were compared, and the dynamics of physical, chemical and biological properties of soil at different crop stages were determined in this paper. The annual crop yield, biomass and economic return of RRV were significantly higher than those of RRF due to the inclusion of winter vegetables (green beans) in the cropping system. The contribution of green beans to the total revenue per year for RRV was as high as 73%. Filling winter fallow with green beans had no influence on the yield of early and late rice. Soil NO 3 −-N, available P, exchangeable K, exchangeable Fe, exchangeable Cu and acid phosphatase activity at the winter stage were significantly higher in RRV than in RRF, whereas soil pH, soil organic carbon (SOC), dissolved organic carbon (DOC), exchangeable Ca, exchangeable Mg, catalase activity, dehydrogenase activity and invertase activity at the winter stage were lower. The soil NO 3 −-N, exchangeable Fe, exchangeable Cu, and acid phosphatase activity during the early rice stage also tended to be higher in the RRV system. The annual dynamics of soil physical, chemical and biological properties were proven to be greater in the RRV system than in the RRF system. The findings of our study contribute to the understanding of dynamic changes in physical, chemical and biological properties of soil across different crop stages due to intensified green bean planting during the winter fallow period in a double-rice cropping system, which will be useful for the sustainable development of RRV. • Yield and economic income increased significantly in RRV system than RRF system. • Most soil nutrients content were significantly higher in RRV than in RRF. • Soil pH, SOC, and some soil enzyme activity were lower in RRV than in RRF. • The annual dynamics of soil properties were proved to be greater in RRV than in RRF. [ABSTRACT FROM AUTHOR]

• IQI-NLS index performed better than other soil quality model in BSZJLC. • The determined MDS for BSZJLC included BD, CEC, SOM, AN, TK, ACu, and AFe. • The soil quality in study area was dominated by moderate grades. • Effects of environmental factors on soil quality has local characteristic. Soil quality assessment is an effective way to improve understanding of the heterogeneity of soil quality and to encourage the adoption of proper agricultural practices. The object of this paper is to select the most effective soil quality indices and the minimum data set (MDS) for the black soil zone of Jilin Province, China, and analyze the association between soil quality and the environmental control. Taking the croplands of the black soil zone of Jilin Province, China, as the study area, different combinations of scoring methods, indices, and data set methods were compared. A minimum data set, based on the integrated quality index derived from non-linear scoring methods (MDS IQI-NLS index), was then selected via principal components analysis to assess the soil quality of the study area. The determined minimum data set for the study area included bulk density, cation exchange capacity, soil organic matter, alkali-dissolvable N, total K, extractable Cu, and extractable Fe. The results showed that the soil quality in the study area was of dominantly moderate grades (grades II, III and IV), accounting for approximately 90% of the total as well as the minimum data set, and the soil quality index increased from the northwest to the southeast. Group analysis was applied because different combinations of environmental factors play different roles in different sub-regions. The analysis results showed that the most important factors affecting soil quality in group 1 (in decreasing order of importance) were: mean annual temperature, DEM, amount of straw return, parent material, and topographic wetness index. For group 2 they were: parent material, annual precipitation, mean annual temperature, chemical fertilizer, DEM, amount of straw return. This analysis proves to be an effective way to determine the factors that affect the spatial distribution of soil quality. [ABSTRACT FROM AUTHOR]

The total uranium (U) content and various forms of U content in the farmland-paddy rice system around uranium tailings dam were investigated and analyzed to reveal the actual situation of U pollution and its influencing factors. The results showed that the U content in the study area was not high overall and mainly existed in the form of residual state, so the actual contamination degree of U was low. Soil physicochemical properties had different effects on U content in soil and rice. The research results were of positive significance for guiding the treatment of U pollution in this region. [ABSTRACT FROM AUTHOR]

Aims: Two field microcosm experiments and N labeling techniques were used to investigate the effects of biochar addition on rice N nutrition and GHG emissions in an Inceptisol and an Ultisol. Methods: Biochar N bioavailability and effect of biochar on fertilizer nitrogen-use efficiency (NUE) were studied by N-enriched wheat biochar (7.8803 atom% N) and fertilizer urea (5.0026 atom% N) (Experiment I). Corn biochar and corn stalks were applied at 12 Mg ha to study their effects on GHG emissions (Experiment II). Results: Biochar had no significant impact on rice production and less than 2 % of the biochar N was available to plants in the first season. Biochar addition increased soil C and N contents and decreased urea NUE. Seasonal cumulative CH emissions with biochar were similar to the controls, but significantly lower than the local practice of straw amendment. NO emissions with biochar were similar to the control in the acidic Ultisol, but significantly higher in the slightly alkaline Inceptisol. Carbon-balance calculations found no major losses of biochar-C. Conclusion: Low bio-availability of biochar N did not make a significantly impact on rice production or N nutrition during the first year. Replacement of straw amendments with biochar could decrease CH emissions and increase SOC stocks. [ABSTRACT FROM AUTHOR]