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To achieve the carbonization utilization of Triarrhena lutarioriparia straw and relieve the environmental pressure caused by improper disposal in the Dongting Lake area, the agricultural efficiency of biochar derived from Triarrhena lutarioriparia was clarified. Two typical paddy soils in southern China, namely reddish clayey soil developed from a Quaternary laterite parent material and granitic sandy soil developed from a granite parent material, were selected. Six treatments with different dosage of biochar (0, 1%, 2%, 4%, 6%, and 8% of the soil mass，0-20 cm soil depth) were set. Rice pot experiments were conducted in 2020 to study the effects of different application rates of Triarrhena lutarioriparia biochar on rice nutrient utilization characteristics in two typical soils. The results showed different application rates of Triarrhena lutarioriparia biochar and soil types had certain effects on dry matter accumulation and nutrient uptake by rice organs and aboveground structures. With the addition of biochar, compared with the treatment without biochar, the accumulation of dry matter of rice increased from 0.6% to 18.6% and from 15.5% to 42.4% in the granitic sandy soil and reddish clayey soil, respectively. With the addition of 4% biochar, the accumulation of nitrogen, phosphorus, and potassium nutrients in the rice plant of the treatment increased by 8.6%, 10.5%, and 82.5% in the granitic sandy soil and by 33.8%, 100.0%, and 125.3% in the reddish clayey soil, respectively. The quadratic regression equation and fertilizer – carbon coupling model fitting showed that the optimal addition amounts of biochar in the granitic sandy soil and reddish clayey soil were 2.51% and 4.80% for nitrogen utilization, 4.33% and 7.03% for phosphorus utilization, and 4.67% and 4.81% for potassium utilization, respectively. Therefore, the application of Triarrhena lutarioriparia biochar is conducive to promoting the accumulation and growth of nitrogen, phosphorus and potassium nutrients in rice, and the amount of biochar added and soil conditions are important factors affecting the coupling effect of fertilizer and carbon. [ABSTRACT FROM AUTHOR]

Purpose: Land subsidence has caused serious geological damage in many countries, including China. Soil pore number, size, shape, and pore size distribution affect soil deformation and thus land subsidence. Quantification of complex pore structures in different soil types and at various soil depths, however, remains cumbersome. The objective of this study was to quantify pore characteristics of three different soil types using computed tomography (CT) technique, investigate the effects of soil depth, examine the relationships between various parameters, and preliminarily determine the pore deformation pattern. Materials and methods: Undisturbed soil samples (70 mm diameter × 50 mm height) of clay, silt, and silty clay soils were collected from two 300-m-deep engineering geological boreholes on both sides of the Xi'an D7 ground fissure. One hundred CT images were acquired for each soil sample. Soil pore characteristics and morphological parameters, including porosity, macroporosity, coarse mesoporosity, microporosity, number of pores, number of macropores (diameter > 1000 μm), number of coarse mesopores (diameter 200–1000 μm), number of micropores (diameter < 200 μm), circularity, structure model index, degree of anisotropy, and the Euler number, were analyzed. Results and discussion: Micropores were generally regularly shaped and the main contributors to the total number of pores, whereas macropores were mostly elongated and contributed to total porosity. With increasing depth, the most noticeable changes appeared in silt soil and the least noticeable in clay soil. The alternate pore deformation pattern was significant in silt and silty clay soils. Conclusions: Soil depth significantly influenced all soil pore parameters, whereas soil type significantly affected the remaining parameters, except circularity and degree of anisotropy. The elongated macropores in silt and silty clay soils favor land subsidence in the Xi'an area. The present results can help optimize the groundwater exploitation layer, reducing soil compaction and land subsidence in this area. [ABSTRACT FROM AUTHOR]

Based on the soil temperature and humidity data of soybean farmland under conservation tillage in Northeast China in the published article, the impact of conservation tillage measures on the soil hydrothermal status of soybean farmland in Northeast China was quantitatively assessed by using conventional tillage (CT) as a control, no-tillage (NT), reduced tillage (RT), straw mulching (SM), and no-till straw mulching (NTSM) as treatments. The results showed: compared with CT, conservation tillage increased the soil volume water content of 0-170cm soil layer in soybean farmland in Northeast China by 9.2%, and reduced the temperature of the shallow soil layer (0-30cm) by 8.2%. Four conservation tillage could increase soil moisture under different climatic conditions; straw mulching could increase soil moisture content throughout the growth period of soybeans, and the effect on soil hydrothermal was greatest during the nutrition period of soybean, and soil temperature increased with the increase of straw mulching; the magnitude of soil temperature reduction by conservation tillage decreases with the decrease of soil clay particles, the magnitude of soil moisture increased by conservation tillage decreases with the increase of soil depth. Among them, NTSM at different soil depths was the most obvious effect of water storage and moisture retention, and the soil moisture in the soil layer of 0-20cm was increased by 32.9%. In summary, conservation tillage could increase soil moisture but reduce soil temperatures. Temperature, precipitation, growth period, straw mulching amount, soil type and soil depth all had an impact on soil hydro-thermality in soybean farmland under conservation tillage. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the extent and causes of soil compaction of the apple orchards in the Weibei Dry Highland. Nine 'Red Fuji' apple orchards with number of planting years in the ranges of <10‐year, 10–20‐year and >20‐year were included. Soil bulk density, porosity, penetration resistance, organic matter (SOM), clay, water and soil aggregate size distribution were determined. The results showed that the subsoil (20–30 cm) of apple orchards was compacted. The bulk density and packing density (PD) of subsoil increased sharply by an average of 17.9% and 18.0%, respectively, relative to topsoil (0–10 cm), and the porosity decreased by 17.0%. The depths of the soil layer with penetration resistance exceeding 1,000 kPa became shallower with increased planting years. Compared with <10‐year apple orchards, the bulk density, PD and soil penetration resistance in 10–20‐year and >20‐year apple orchards were increased, respectively, by 5.3%, 5.3% and 29.3%, but the porosity decreased by an average of 8.2%. Compared with topsoil, the water‐stable aggregates of >0.25 mm and the mean weight diameter of wet sieve aggregates (MWDW) of compacted soil were 57.6% and 25.4% lower, respectively. Soil clay content increased with soil depth from 0 to 60 cm, but the SOM showed an opposite trend. Additionally, there was a dry soil layer at a depth of 20–40 cm. Thus, the factors affecting the soil compaction process were determined to be inferior agglomeration ability of soil, internal soil desiccation, and the downward migration of soil clay particles. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering 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.)

[Display omitted] • High soil P content was found in eastern and northern subtropical China. • Soil clay strongly and negatively affected regional-scale variation in soil P. • Humidity index and DBH indirectly affected soil available P via soil clay content. • Extending the rotation period benefits the recovery of soil P availability. Evaluating the environmental effects on soil phosphorus (P) availability is the key to understanding P cycling and regulating forest productivity. However, what and how environmental factors affect soil P availability in regional plantation ecosystems remains unclear. The study evaluated the effects of climatic factors, nitrogen deposition rate, stand attributes, litter characteristics, and soil-associated properties on soil P availability in Masson pine plantations across subtropical China using stepwise regression and structural equation modelling (SEM) analyses. At the 0–20 cm and 20–40 cm soil depths, soil total P ranged from 0.24 to 0.43 g kg−1 and from 0.24 to 0.48 g kg−1, respectively. Similarly, soil available P varied from 0.35 to 7.55 mg kg−1 and from 0.14 to 4.34 mg kg−1, respectively. Soil total and available P had high values in the eastern and northern distribution areas of subtropical China. Soil total P linearly decreased with an increase in bulk density, clay and pH but linearly increased with an increase in DBH. These four factors had a similar contribution (15.5–35.1 %) to soil total P. Soil available P linearly decreased with an increase in bulk density and clay. The relative contribution of clay (48.1–75.7 %) to soil available P was higher than that of bulk density (16.2–33.5 %). Soil total P decreased during the initial 30 years of plantations and then increased. But other variables (e.g., climate, nitrogen deposition, and litter) had no significant impacts on soil P. Overall, the SEM explained 35.4 % and 28.1 % of soil available P variations at the 0–20 cm and 20–40 cm soil depths, respectively, and revealed that clay had strong total effects (β = -0.526 and −0.396) on the soil available P. These results reveal the dominant roles of soil texture (especially clay) in affecting soil P availability in Masson pine plantations and suggest that extending the rotation period benefits soil P recovery in pine plantation ecosystems of subtropical China. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering 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.)

This study aimed to improve runoff simulations and explore deep soil hydrological processes for a watershed in the center of the Loess Plateau (LP), China. This watershed, the Wuding River Basin (WRB), has very complex topography, with soil depths ranging from 0 to 197 m. The hydrological model used for our simulations was the Community Land Model (CLM) version 5 developed by the National Center for Atmospheric Research. Actual soil depths and river channels were incorporated into CLM to realistically represent the physical features of the WRB. Through sensitivity tests, CLM with 150 soil layers produced the most reasonable results and was adopted for this study. Our results showed that CLM with actual soil depths significantly suppressed unrealistic variations of the simulated sub-surface runoff when compared to the default simulations with a fixed soil depth of 8 m. In addition, CLM with higher-resolution soil layering slightly improved runoff simulations, but generated simulations with much smoother vertical water flows that were consistent with the uniform distribution of soil textures in our study watershed. The runoff simulations were further improved by the addition of river channels to CLM, where the seasonal variability of the simulated runoff was reasonably captured. Moreover, the magnitude of the simulated runoff remarkably decreased with increased soil evaporation by lowering the soil water content threshold, which triggers surface resistance. The lowered threshold was consistent with the loess soil, which has a high sand component. Such soils often generate stronger soil evaporation than soils dominated by clay. Finally, with the above changes in CLM, the simulated total runoff matched very closely with observations. When compared with those for the default runoff simulations, the correlation coefficient, root-mean-square error, and Nash Sutcliffe coefficient for the improved simulations changed dramatically from 0.02, 10.37 mm, and -12.34 to 0.62, 1.8 mm, and 0.61. The results in this study provide strong physical insight for further investigation of hydrological processes in complex terrain with deep soils. [ABSTRACT FROM AUTHOR]

Purpose: Soil organic nitrogen (SON) biochemistry trends in paddy soils are poorly understood on a long-term scale. Methods: To explore the effect of land use on SON sequestration, SON and amino acid (AA) fractions were investigated in soil profiles comprising recent and buried paddy soil (BPS) and buried non-paddy soils (BNS). Two ancient paddy soils from Chuodun ruin site, China, were distinguished based on colour and rice phytolith abundance. 14C abundance in soil organic carbon was used to estimate the age of carbonized rice and ancient paddy soil via a liquid scintillation analysis method, dating to 3800–5500 and 960–4000 BC. Results: The proportions of D-AAs and acidic AAs in BPS, up to 6.13% and 7.73%, respectively, were higher than those in modern paddy soils. D-alanine (and the D-/L- ratio), aspartate, and glutamate increased with soil depth in BPS, and the amount of D-aspartate was linearly and significantly positively correlated with soil depth (p < 0.05). Based on phytolith stability and abundance, the N sequestration rate (NSR: residual N content as a proportion of initial N content) was proposed to indicate the residual N content varied with time. The NSR was estimated as 10.8–91.2% in BPS with a phytolith stability factor of 0.5–0.9. Conclusion: These data suggest that intermittent continuous high-intensity rice cultivation could increase soil N sequestration potential over the long term, and that N sequestration is not only associated with AA aging in the organic N fraction, but also with biogeochemical processes in BPS and paddy management. In addition, high-intensity rice cultivation can increase N loss risks, and in turn result in large fluctuations in N sequestration. [ABSTRACT FROM AUTHOR]

In this study, a series of resonant-column experiments were conducted on marine clays from Bohai Bay and Hangzhou Bay, China. The characteristics of the dynamic shear modulus (G) and damping ratio (D) of these marine clays were examined. It was found that G and D not only vary with shear strain (γ), but they also have a strong connection with soil depth (H) (reflected by the mean effective confining pressure (σm) in the laboratory test conditions). With increasing H (σm) and fixed γ, the value of G gradually increases; conversely, the value of D gradually decreases, and this is accompanied by the weakening of the decay or growth rate. An intelligent model based on a back-propagation neural network (BPNN) was developed for the calculation of these parameters. Compared with existing function models, the proposed intelligent model avoids the forward propagation of data errors and the need for human intervention regarding the fitting parameters. The model can accurately predict the G and D characteristics of marine clays at different H (σm) and the corresponding γ. The prediction accuracy is universal and does not strictly depend on the number of neurons in the hidden layer of the neural network. [ABSTRACT FROM AUTHOR]

Tamarix chinensis and Ziziphus jujuba are two dominant shrub species on Chenier Island in the Yellow River Delta, China. Water is a restrictive factor determining the plant growth, vegetation composition, and community succession in this coastal zone. We investigated how water uptake tradeoffs of the two shrub species responded to soil water fluctuations caused by seasonal variations of precipitation. The soil water content, salinity and δ18O values of potential water sources (soil water in 0–20, 20–40, 40–60, and 60–100 cm soil layers, and groundwater) and plant xylem water were measured in wet (July 2013) and dry (July 2014) seasons. The IsoSource model was employed to calculate the contributions of different water sources to plant xylem water. The results showed that δ18O values of soil water decreased significantly with soil depth in the dry season, while increased significantly with soil depth in the wet season. In the wet season, when the soil water was abundant, Z. jujuba mostly used the soil water from the 60–100 cm layer, while T. chinensis took up a mixture of groundwater and soil water from the 60–100 cm layer. In the dry season, when the soil water was depleted because of low precipitation, Z. jujuba mainly took up a mixture of the soil water from 20 to 100 cm soil layers, while T. chinensis mainly used groundwater. T. chinensis and Z. jujuba showed different ecological amplitudes of water sources during dry and wet seasons. The niche differentiation of major water sources for T. chinensis and Z. jujuba demonstrated their adaptabilities to the fluctuations of soil moisture in water-limited ecosystems. Water niche differentiations of coexisting shrub species were expected to minimize their competition for limited water sources, contributing to successful coexistence and increasing the resilience of the coastal wetland ecosystem to drought. [ABSTRACT FROM AUTHOR]