Higher Soil Water Content Research Articles

Conservation Tillage Impacts and Adaptations in Irrigated Corn Production in a Humid Climate

Core Ideas No‐till land management (NT) decreases corn production in a humid climate. The reasons for reduced yield were investigated by integrating system models with experiments. Soil N deficiencies under NT possibly contributed to the yield decrease. Split application or enhancing N rate can compensate for the yield decrease under NT. We initiated a long‐term experiment in 2008 on 1.25‐ha farm‐scale plots to assess the production impacts of no‐till with full residue retention (NT) system over a conventional tillage (CT) system under irrigated corn (Zea mays L.) production on a Dundee silt loam soil in a humid climate. Data collected in the experiment from 2009 to 2015 were mainly confined to grain yield at harvest. In 2016 and 2017, additional data were collected including soil surface crop residue mass and soil surface residue cover; corn leaf area index (LAI) and biomass; soil water, temperature, N, C, and bulk density (Db); and the corn phenology. In 7 out of 9 yr (2009–17), harvested grain yields under NT were significantly lower than those harvested under CT. To investigate the possible reasons for the yield decreases under NT, we integrated the experiment with the Root Zone Water Quality Model to synthesize information on the various components in the system. The N loss to runoff and deep percolation, denitrification caused by higher soil water content, and a low N mineralization rate caused by lower soil temperatures under NT potentially contributed to the observed grain yield decrease under this treatment. Simulations showed that an additional N application at 40 kg ha−1 at planting or a split application of 50 kg ha−1 at planting and the remaining 174 kg ha−1 in the second week of May could make the yield return under NT comparable to that under CT.

Stomatal sensitivity inCorylus avellana(L.): first analysis from a global dataset

The cultivated area planted with hazelnut is rapidly increasing. The species is now being planted in areas where precipitation is scarce and irrigation is needed for ensuring profitable orchards. Moreover hazelnut is known to be sensitive to water shortage as it responds quickly to the increase of vapor pressure deficit by reducing stomatal aperture and consequently carbon assimilation. However modeling stomatal responses in different climatic conditions is still a challenging task. The general aim of the research was to predict stomatal responses by collecting data in different climatic conditions and soil water availability. We installed five measurement sites with different cultivars (‘Tonda Gentile delle Langhe’, ‘Tonda di Giffoni’, ‘Ennis’) in different countries (France, Georgia, Australia, Chile) and under different irrigation regimes. In each site we measured the sap flow in six trees, the soil water content, the stem diameter variations and the meteorological parameters. In two sites (Australia and France) we measured the stomatal conductance and the carbon assimilation by using a portable gas analyzer. Results showed that in all sites and cultivars, hazelnut trees strongly reduce the stomatal aperture when the vapor pressure deficit exceeds 10 hPa, which leads to a decrease in the assimilation rate. The daily course of stomatal aperture showed that the maximum is reached very early in the morning (about 9 AM) and then it drops abruptly. Furthermore, the species responses at leaf level were coherent with those at the tree canopy level, establishing a crucial basis for the future modelling of the water use at the orchard level. We showed that the carbon assimilation is mainly controlled by stomatal sensitivity to vapor pressure deficit and that, even in conditions of high soil water content, the photosynthetic capacity of the species is clearly reduced.

Changes in plant biomass induced by soil moisture variability drive interannual variation in the net ecosystem CO2 exchange over a reclaimed coastal wetland

Changes in the timing and magnitude of precipitation is a threat to agricultural productivity and farmland carbon stocks. However, the relationship between inter-annual variations in precipitation and net ecosystem CO2 exchange (NEE) remains to be clarified, particularly when combined with water-salt transport in reclaimed coastal wetland. Here, based on the eddy-covariance technique, we investigated the interannual variation in carbon dioxide exchange and its control mechanism over a reclaimed coastal wetland of the Yellow River Delta from 2010 to 2014. The coastal wetland functioned as a strong sink for atmospheric CO2, with the annual NEE of −229, −175, −142, −92 and −80 g C m−2 in the 5 years from 2010 to 2014, respectively. Surprisingly, we find that large annual variation in net ecosystem exchange (NEE) can be predicted accurately using plant biomass. Plant biomass was driven by soil water content (SWC), with about 48%–80% seasonal variation of biomass attributed to SWC. During the early growing stage, high SWC accompanied with low salinity promoted plant biomass and NEE. While high SWC accompanied with increased waterlogged stress inhibited plant biomass and NEE during the middle growing stage. The same results were also observed in a field manipulation experiment over a nearby natural coastal wetland. Our study indicated that extreme climate accompanied with extreme drought and flooding may decrease carbon sequestration capacity of the reclaimed coastal wetland due to the increase in salinity.

Impact of projected climate change on workability, attainable yield, profitability and farm mechanization in Norwegian spring cereals

In cold-temperate climate with high soil water content in spring, the farmer often faces the choice between topsoil compaction during seedbed preparation and delayed sowing, both of which may reduce attainable cereal yield. The objective of this study was to explore whether future climate change with increasing precipitation would aggravate this dilemma. We generated weather based on historical and projected future climate in South-eastern and Central Norway. Using this weather data as input, we simulated spring workability, attainable yield, timeliness costs, and mechanization management with a workability model and a mechanization model. The projected climate changes resulted in improved workability for spring fieldwork and higher attainable yield in South-eastern Norway, and either positive or negative changes in Central Norway compared to historical conditions. We observed a general increase in variability of workability and attainable yield, and a larger risk of extremely unfavourable years in the most unfavourable scenarios in Central Norway. Changes in profitability and mechanization management were small, but followed the same pattern. The negative effects in the most unfavourable climate scenarios in Central Norway were in contrast to positive effects in earlier studies. We explained discrepancies by differences in research methods and purpose. However, simulated sowing dates of annual crops should consider workability of the soil, in terms of water content. Under worst-case conditions, in need of a certain time window to complete their spring fieldwork, farmers might adapt to impaired spring workability by working the soil at higher water content than simulated in our study. The consequence would be a larger loss of attainable yield and less profitability in the future. We anticipate that negative effects may also be expected in other northern cold-temperate regions with high soil water content in spring.

Actively heated fiber optics method to monitor three-dimensional wetting patterns under drip irrigation

Monitoring dynamics in wetting patterns under drip irrigation is important to optimize the frequency and duration of irrigation, the emitter discharge rate and the spacing. However, difficulties in measurement of soil water content (SWC) at high spatial and temporal resolution and in three-dimensions (3D) restricts direct monitoring around drip emitters. Indirect methods such as actively heated fiber optics (AHFO) has shown the potential to measure SWC at sub-meter intervals. Therefore, the objective of this study was to examine the feasibility of the AHFO method to monitor 3D spatial and temporal variations in wetting patterns under a single drip emitter. Heat pulses of three minutes duration were applied at a rate of 20 Wm−1 through a helically wrapped fiber optic cable in a soil column before, during, and after irrigation. A distributed temperature sensing (DTS) instrument was used to estimate the cumulative temperature increase (Tcum) at locations along the cable. An indirect relationship between Tcum and SWC was developed and validated using the SWC measurements determined by the gravimetric method. Data from the network of 3D points (from fiber optic cable) were used to generate 3D surfaces of SWC. In comparison with the gravimetric method, AHFO showed predictive accuracies; root mean squared error (RMSE) of 0.03 m3 m−3 for SWC <0.05 m3 m−3 (N = 17), 0.03 m3 m−3 for SWC 0.05–0.3 m3 m−3 (N = 19) and, 0.05 m3 m−3 for SWC >0.3 m3 m−3 (N = 6). The time evolution of the 3D SWC helped to identify wetting bulb formation, movement of the wetting front and changes in the dimensions (wetted radius and depth) of wetting bulbs. This study showed not only the potential of AHFO to help design drip emitters but also the ability to provide high resolution SWC information to improve water movement models in the future.

Numerical modelling of the long runout character of 2015 Shenzhen landslide with a general two-phase mass flow model

High fluid content or pore-fluid pressure is generally the main reason for the triggering and high mobility of landslides. A catastrophic landslide occurred at Hongao construction waste dumpsite in the Guangming New District of Shenzhen, China, on Dec 20, 2015. Due to the high water content of soil in the source area, this landslide propagated over an extremely long travel distance, with maximum length and width of the affected area 1100 m and 630 m, respectively. High water content pesents a great challenge to numerical methods. In order to simultaneously include the evolution of the solid and fluid components in the mixture, a general two-phase mass flow model of Pudasaini (J Geophys Res 117: F03010, 2012) has been employed in our simulations. The complex interactions between the solid and fluid phases, including buoyancy, the virtual mass force, generalized drag and enhanced non-Newtonian viscous stress, are considered in this two-phase flow model. These are essential aspects in the motion of landslides consisting of viscous fluid and solid particles. Based on the actual geology and engineering conditions, runout characteristics of the Shenzhen landslide were analyzed numerically. The principal reasons for the long runout character and the inundation are discussed based on the physics-based model and high-resolution numerical results.

Potassium Fertilization Role in Tomato Tolerance of Water Salinity and Stress under Drip Irrigation System

A study was carried out on a field scale during two successive growth seasons (2009/2010 and 2010/2011) on tomato plants irrigated with saline ground water (2.24 and 3.86 dS m-1) using drip irrigation system, subjected to water stress (irrigation every 3, 4, and 5 days), and were grown under application of potassium fertilization (96, 120, and 144 kg K2O/feddan) in newly reclaimed lands at the Agricultural Experiments and Research Center, Faculty of Agriculture, Minia University, El-Minia Governorate, Egypt. The current study aims to investigate the effects of irrigation water salinity and water stress on tomato growth, tomato yield, and tomato fruit quality under application of a salinity and water stress alleviated amendment (potassium fertilization) using drip irrigation system. The obtained results of the current study showed that increasing irrigation water salinity level from 2.24 dS m-1 to 3.86 dS m-1 decreased tomato plant height, tomato shoots fresh weight, average tomato fruit weight, fresh tomato fruit yield, and tomato fruit dry weight, while, it increased tomato shoots dry weight, number of tomato fruits per plant, total soluble solids of tomato, and tomato fruits marketability (shelf life) in growth seasons. Increasing irrigation interval from 3 up to 5 days decreased tomato shoots fresh weight in both growth seasons, however, it increased tomato shoots dry weight, total soluble solids, and tomato fruits marketability in the two growth seasons. Increasing the potassium fertilization level from 96 up to 144 kg K2O/feddan increased the tomato plant height, tomato shoots dry weight, average tomato fruit weight, total soluble solids of tomato, and tomato fruits marketability. Increasing the potassium fertilization level from 96 to 120 or 144 kg K2O/feddan increased the tomato shoots fresh weight, number of tomato fruits per plant, fresh tomato fruit yield, and tomato fruit dry weight in the two growth seasons. The increase in the tomato plant height, tomato shoots fresh weight, tomato shoots dry weight, number of tomato fruits per plant, average tomato fruit weight, fresh tomato fruit yield, total soluble solids of tomato, tomato fruits marketability, and tomato fruit dry weight implies that application of potassium fertilization to soil alleviated adverse effects of salinity stress and water stress on tomato growth, tomato yield, and tomato fruit quality. The results of the current research indicated that it can be recommended that to alleviate and manage adverse effects of salinity stress and water stress on tomato growth, tomato yield, and tomato fruit quality, good cultural practices management to be followed are: (1) irrigate tomato plants every 4 days, (2) apply appropriate and optimized requirements of potassium fertilization to soils (120 kg K2O/feddan), and (3) use drip irrigation system as an irrigation management which might control soil salinity build-up and soil water content since it can keep a high soil water content and low salt concentration in the root zone.

Tree Water Use Patterns as Influenced by Phenology in a Dry Forest of Southern Ecuador.

Tropical dry forests are composed of tree species with different drought coping strategies and encompass heterogeneous site conditions. Actual water use will be controlled by soil moisture availability. In a premontane dry forest of southern Ecuador, tree water use patterns of four tree species of different phenologies were studied along an elevational gradient, in which soil moisture availability increases with altitude. Main interest was the influence of variation in soil moisture, vapor pressure deficit, species (representing phenology), elevation, and tree diameter on water use. Special emphasis was put on the stem succulent, deciduous Ceiba trichistandra, as high water use rates and drought coping involving stem succulence was to be expected. Tree water use rates increased linearly with diameter across species at high soil water content. However, when soil moisture declined, sap flux densities of the species responded differently. The stem succulent, deciduous Ceiba and other deciduous tree species reduced sap flux sensitively, whereas sap flux densities of the evergreen (broad leaved) Capparis scabrida were increasing. This was also reflected in diurnal hysteresis loops of sap flux vs. vapor pressure deficit (VPD) of the air. Under dry soil conditions, Ceiba and other deciduous tree species had much smaller areas in the hysteresis loop, whereas the area of Capparis was largely enhanced compared to wet conditions. The evergreen Capparis potentially had access to deeper soil water resources as water use patterns suggest that top soil drought was tolerated. The deciduous species followed a drought avoidance strategy by being leafless in the dry season. The stem succulent deciduous Ceiba flushed leaves at the end of the dry season before the rainy season began and also re-flushed early in the dry season after a rain event; however, water use rates at this occasion remained low. Ceiba was also ready for fast and strong response in water use when conditions were most favorable during the wet season. The study thus indicates a strong influence of species’ drought coping strategy on water use patterns in tropical dry forests.

Effects of temperature and soil moisture on gross nitrification and denitrification rates of a Chinese lowland paddy field soil

Alternate wetting and drying (AWD) irrigation is widely adopted to save water in rice production. AWD practice shifts lowland paddy fields from being continuously anaerobic to being alternately anaerobic and aerobic, thus affecting nitrogen (N) transformations in paddy field soils. Using the barometric process separation technique, a large number of soil cores sampled from lowland paddy field soil profiles were measured for gross nitrification and denitrification rates under different temperature and soil moisture conditions. The gross nitrification and denitrification rates vary with rice growth stages and range between 1.18–30.8 and 0.65–13.54 mg N m−3 h−1, respectively. Results indicate that both gross nitrification and denitrification rates increased with the increase in temperature in all three studied soil layers. Gross nitrification rates significantly decrease with increasing soil moisture while denitrification rates increase, and different soil layers demonstrated different rates of variation to the increase in soil moisture. Gross nitrification rates in the cultivated horizon layer decreased more sharply with the increase in soil moisture. High soil water content is favorable to denitrification of all soil layers.

Impact of Soil Water Content on Hybrid Bermudagrass Athletic Fields

Soil water content (SWC) influences the consistency and performance of athletic field surfaces. Two studies were conducted at the University of Tennessee Center for Athletic Field Safety, Knoxville, TN, to determine how SWC affects wear tolerance of hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy, ‘Tifway’] on root zones composed of either silt loam (cohesive) or sand meeting US Golf Association specifications (noncohesive). Soil water content treatments for cohesive root zones averaged low (0.06–0.13 m3 m−3), medium (0.14–0.21 m3 m−3), medium‐high (0.22–0.29 m3 m−3), and high (0.30–0.37 m3 m−3); comparatively, SWC on noncohesive averaged low (0.05–0.11 m3 m−3), medium (0.12–0.19 m3 m−3), and high (0.20–0.27 m3 m−3). Differences in the amount of ranges between root zones were due to plant available water of the soil texture. Plots were subjected to 50 traffic events for 5 wk each fall over a 2‐yr period. Green turfgrass cover was reduced four times faster at high SWC than the low and medium SWC treatments on cohesive soil. All SWC treatments on noncohesive soil lost green turfgrass cover at a predictable rate. Surface hardness increased as SWC decreased for both root zones. Turfgrass shear strength decreased with traffic for all treatments on cohesive soils. Soil water content of noncohesive soils did not compound the effect of traffic on turfgrass shear strength. The optimal mean SWC ranges to maximize hybrid bermudagrass wear tolerance on cohesive soils were low to medium, and low to medium on noncohesive soils.

Influence of rainwater harvesting and soil anti-seepage on soil water infiltration, distribution and use efficiency in hilly orchard.

Rainwater harvesting and soil anti-seepage technology is a new technology based on the ridge film mulching and furrow rainwater harvesting. To explore the application effects of rainwater harvesting and soil anti-seepage technology, four different treatments including control (CK), loessal soil with compacted anti-seepage treatment (L1), red clay with anti-seepage treatment (R1), and red clay with compacted anti-seepage treatment (R2) were set up in a "Fuji" hillside orchard in Mizhi Demonstration Station of northern Shaanxi Province. Soil bulk density, stable infiltration rate, soil water content, fruit quality and yield, and water use efficiency were measured. Results showed that R2 had the best anti-seepage efficiency with the highest bulk density (1.61 g·cm-3), the minimum water holding capacity, and the least stable infiltration rate (0.02 mm·min-1). The empirical formula of Kostiakov equation was suitable for describing water infiltration characteristics. Throughout the growing season, soil moisture for 0-60 cm soil depth in the rainwater harvesting ditch could be improved by the different anti-seepage treatments. R2 had the highest soil water content all the time and could satisfy the suitable water content standard for growth and development of apple trees in the dry season. Under the anti-seepage treatment, there was an "low humid layer" with 20-30 cm of soil layer under 60 cm soil depth, but the variation tendency of soil water content from "low humid layer" to 200 cm soil layer was stable and slightly higher than that in CK. Rainwater harvesting and soil anti-seepage treatments could increase fruit yield and water use efficiency, and improve the quality of fruit. Compared with that in CK, the fruit yield, the rate of good fruit, and water use efficiency of R2 treatment increased by 19.2%, 26.5%, and 24.5%, respectively. Therefore, rainwater harvesting and soil anti-seepage technology was recommended as the effective agricultural measurement in the apple production in loess hilly areas of northern Shaanxi Province.

Failure mode and dynamic response of a double-sided slope with high water content of soil

A double-sided slope with high water content in sandy clay was considered under the action of seismic load. Its failure mode and dynamic response were investigated using a hydraulic servo shaking table test. The typical characteristic of failure mode and dynamic responses of the double-sided slope were analyzed. Experimental results show that slope failure undergoes a process of progressive deformation. The slope failure mode can be explained as creep sliding landslide. AFA (Amplification Factor of Acceleration) at the surface and inner parts of the slope shows an increasing trend with the increase of relative elevation. The relationship between AFA and EAA (Excitation Amplitude of Acceleration) is nonlinear. An empirical formula is proposed to describe preferably the relationship between AFA, relative elevation and dimensionless EAA. The AFA at the middle and upper parts of the slope increases apparently with increasing EFA (Excitation Frequency of Acceleration).

Is a Water Content of 60% Maximum Water Holding Capacity Suitable for Folsomia candida Reproduction Tests? A Study with Silver Nanoparticles and AgNO₃.

Silver nanoparticles (AgNP) are increasingly emitted to the environment due to a rise in application in various products; therefore, assessment of their potential risks for biota is important. In this study the effects of AgNP at environmentally relevant concentrations (0.6–375 µg kg−1 soil) on the soil invertebrate Folsomia candida in OECD (Organisation for Economic Co-operation and Development) soil was examined at different soil water contents. Animals were retrieved by heat extraction, which had an efficiency of about 90% compared with the floatation method. The tested water content range is set by OECD Guideline 232 (40–60% of the maximum water holding capacity, WHC), and we detected significant differences in toxicity due to these. With AgNO3, used as an ionic control, the number of juveniles significantly decreased only at 40% WHC, which might be due to dilution of the toxicant at higher soil water content. In turn, at 60% WHC, the reproduction of F. candida significantly increased in the presence of AgNP compared with in the control. However, at this water content, the required number of juveniles in the control treatment was not reached in three independent tests. The fact that the OECD validity criterion is not met indicates that the soil conditions are not suitable for reproduction at 60% WHC.

Hydrological gradients and functional diversity of plants drive ecosystem processes inPoyang Lakewetland

AbstractFunctional trait approaches have greatly improved the mechanistic understanding of the impacts of biodiversity in ecosystem. We evaluated how hydrological gradients (i.e., soil water content and elevation) affected the taxonomic diversity, functional identity, and functional diversity and assessed how changes in these measures of diversity ultimately drove variations in above‐ground biomass (AGB). Results showed that a combination of hydrological gradients and functional trait composition (i.e., the community weighted means, the single‐trait functional diversity and the multiple‐trait functional diversity) better explained variations (40.8%) of AGB. No significant relationships between taxonomic diversity and AGB were observed. The dominant species became taller with thicker stem, and co‐occurring species showed greater divergent distribution of stem diameter towards higher soil water content. As elevation increased, the dominant plant had thinner leaves with later onset of flowering and longer flowering duration, and co‐occurring species showed less divergent distribution of lamina thickness and leaf dry‐mass content. Our results highlighted that the positive biodiversity–ecosystem functioning relations were largely attributed to the co‐operations of selection and complementary effects, as evidences showed that the dominant trait values (i.e., community weighted mean of shoot height) and trait diversity (i.e., functional evenness) improved biomass production of wetland plants.

Potato canopy growth, yield and soil water dynamics under different irrigation systems

The aim of this research was to compare two irrigation and N application systems, gun irrigation (GI) and drip fertigation (DF), in terms of soil water dynamics, N uptake, N use efficiency, and yield of table potatoes. Two treatments were set up in a three-year field experiment. Treatments differed by irrigation and N application methods, and scheduling. Water and N management in GI was managed according to typical best-practice while irrigation and N for DF was applied through drip fertigation according to a crop simulation model. Results showed that DF provided high soil water content at the center of the ridge. Average soil water content across the ridge soil profile was higher for DF than GI. Compared to DF, GI led to relatively high canopy growth early in the season through applying all N at planting, while the opposite trend was detected later in the growing season. Tuber yields in GI were 46, 43 and 44 t ha−1 in 2013, 2014 and 2015, respectively. Tuber yields in DF were 48, 43 and 40 t ha−1 in 2013, 2014 and 2015, respectively. There was no significant difference in yield between systems for any of the three seasons of the experiment. However, DF led to significantly higher tuber N recovery and agronomic N use efficiency in one of the years (2013). In addition, GI caused greater nitrate leaching during the growing season in both 2013 and 2014, as measured by suction cups and simulated by the Daisy simulation model.

Impact of stone bunds on temporal and spatial variability of soil physical properties: A field study from northern Ethiopia

AbstractIn the Ethiopian Highlands, stone bunds (SBs) are a common practice for soil and water conservation, influencing runoff and erosion processes from sloped agricultural areas. The objective of this study was to investigate how SBs affect spatiotemporal relationships of these processes to better understand their impacts on soil water development at the smallholder farmer's field level. Study area was the Gumara‐Maksegnit Watershed in northern Ethiopia, where two representative transects were investigated: One transect crossed a 71 m‐long field intersected by 2 SBs traced along the contour. The second transect crossed a similar hillslope without conservation structures at a length of 55 m representing baseline (untreated) conditions (no stone bund). During the rainy season of 2012, bulk density and volumetric water content were monitored, and tension disc infiltrometer experiments were performed to determine the saturated hydraulic conductivity and to derive soil water retention characteristics. Our observations show that SB decreased significantly soil bulk density in center and lower zones of SB transect compared with no stone bund. No temporal change was observed. Results targeting the surface soil moisture indicate that infiltration was higher with SB and happened earlier in the rainy season in the zones around the SBs. Saturated hydraulic conductivity was positively affected by SB and increased significantly. Improved soil hydrology by SB fields may increase crop yields by higher soil water contents but also by extending the growing season after the rainy season. Therefore, SBs are a successful measure to establish climate‐resilient agriculture in the Ethiopian Highlands.

生物土壤结皮碳释放对水热因子的响应

在室内控制条件下，以腾格里沙漠东南缘1964年人工固沙植被区藻类、混生和藓类结皮为对象，研究了3个温度梯度(15℃、25℃和35℃)和7个水分梯度(3%、5%、10%、15%、20%、25%和30%质量含水量)条件下其碳释放特征。在相同水分条件下，BSCs和流沙呼吸速率随着温度的增加而增加，35℃时BSCs和流沙呼吸速率达到最大值。藓类结皮的呼吸速率显著高于其他土壤类型土壤呼吸。藓类结皮Q10为1.40~3.17，藻类结皮为0.81~3.07，混生结皮为0.55~3.84，流沙为1.19~2.16。BSCs类型、水分和温度显著影响BSCs碳释放量(P < 0.001)。水分含量较高的条件下，藻类和混生结皮的呼吸速率受到了明显抑制，而对藓类结皮的呼吸速率影响不显著。 The carbon release of different types of biological soil crusts (BSC) covered soil was measured under different temperatures condition (15˚C, 25˚C and 35˚C) and different soil water content conditions (3%, 5%, 10%, 15%, 20%, 25% and 30%) in fixed sand dunes at the re-vegetated area in Tengger Desert, Northern China. In the same soil water content condition, the carbon release rate of BSCs and sand were increased with temperature increasing, the highest carbon release rate occurred at 35˚C. The carbon release rate of moss crust was significantly higher than other soil types. Q10 value of moss crust was 1.40 - 3.17, algae crust was 0.81 - 3.07, mixed crust was 0.55 - 3.84 and sand was 1.19 - 2.16. BSCs types, soil water content and temperature were significantly affected on carbon release rate (P < 0.001). The results showed that the respiration rate of the algal crust and mixed crust were significantly restrained by higher soil water content; however, moss crust was not significantly influenced.

Strength Characteristics and Slope Stability of Expansive Soil from Pingdingshan, China

By analyzing the characteristics of expansive soil from Pingdingshan, China, the shear strength parameters at different water contents, dry densities, and dry‐wet cycles of expansive soil are obtained. It is found that, at higher soil‐water content, the internal friction angle is 0° and the shallow layer of expansive soil slope will collapse and destroy; this has nothing to do with the height of the slope and the size of the slope. The parameters of soil influenced by atmosphere are the ones which have gone through dry‐wet cycles, and the parameters of soil without atmospheric influence are the same as those of natural soil. In the analysis of slope stability, the shear strength parameters of soil can be determined by using the finite element method, and the stability coefficient of the expansive soil slope can be calculated.

Reclamation of acid sulphate soils in paddy cultivation area with organic amendments

A soft soil is distinguished by high compressibility and low strength. It is formed in acid sulphate soil under a zero or low pressure gradient as an incompletely consolidated fine grain medium. The problem is related to the presence of weak hardpan structure that permits the soil to experiencing continuous wet condition. The objective of study was to examine closely the effects of addition of organic soil amendment namely Hasil Tani Organic Compound (HTOC) to soft soil in order to enhance its quality and strength. The study was carried out in paddy soils of Muda Agricultural Development Authority (MADA) Alor Senibong Kedah, Malaysia. High water content of soft soil caused low soil strength, which delayed the formation of hardpan layer. The application of HTOC could increase soil strength and reduce water content. After being treated with HTOC, soil strength has increased from 0.22 MPa to 0.70 MPa and organic matter content increased from 3.19% to 7.07%. Whilst, exchangeable sodium percentage (ESP) has decreased from 21% to 5% and soil water content decreased from 40.11% to 24.38%. As whole, the application of HTOC product could improve soft soil in study area.

Modelling soil water dynamic in rain-fed spring maize field with plastic mulching

Numerical solution of the Richards equation with Hydrus-2D model is a low cost and fast way to get information on spatio-temporal soil water dynamics. Previous researches with Hydrus-2D have developed two different approaches to represent the rainfall infiltration in irrigated field with plastic mulching: ‘BP’ – an approach comprised by bare strip boundary and plastic strip boundary without consideration of film side infiltration;‘BP + ’- an approach comprised by bare strip and plastic strip with integrating the process of film side infiltration by increasing the rainfall infiltration amount in bare strip. Nevertheless, the performance of these approaches has not yet been evaluated in rain-fed fields. Considering much more dominant role of rainfall infiltration in rain-fed agriculture, we tested an additional approach which comprised a bare strip, plastic strip and planting hole (BPH) to take into account the effect of the rainfall canopy redistribution and film side infiltration, and we compared its performance to the two existing approaches. Results suggested BP completely failed to reproduce the soil water content (SWC) in all soil layers of plastic strip and in the deep soil layers of bare strip. BP+ overestimated the SWC in 0–20 cm of the bare strip, while the performance of BPH was acceptable in different positions. After that, we compared the soil water distribution between no-mulched field (NM) and plastic mulched field (PM) with approach BPH. Our simulation showed that the highest SWC in PM occurred near the planting hole, SWC in the center zone of plastic strip was lower, while SWC in the bare strip was lowest. PM improves the soil water availability not only in the plastic strip but also in the bare strip as compared to NM.