Soil pore is an important part of soil structure. According to the causes of formation, soil pores can be divided into biological pores formed by animal movement and plant root development and ...non-biological pores formed by dry-wet and freeze-thaw alternation or artificial tillage. The soil pore structure affects the migration of water, gas, nutrients and so on in the soil, especially the macropores can also produce water or solute preferential migration. Studying soil pores is of great significance for predicting soil hydraulic properties, reducing groundwater pollution and soil nutrient loss. Based on previous studies on soil pore structure, this paper systematically summarized the role of soil pores, influencing factors and the advantages and disadvantages of various research methods. This paper not only introduces traditional methods (including direct and indirect methods), but also summarizes the new research on soil pores combined with computed tomography (CT) technology and other science and technology in recent years. Finally, the prospect and development trend of soil pore research in the future were predicted, so as to provide reference for further research on soil pore structure.
Sediment deposition significantly impacts soil erosion processes, consequently influencing the geographical morphology and surrounding environments of reservoirs and estuaries. Given the intricate ...nature of sediment deposition, it is imperative to consolidate and analyze existing research findings. Presently, studies on sediment settling velocity primarily employ theoretical, laboratory, and field experimentation methods. Theoretical approaches, rooted in mechanics, examine the various forces acting on sediment particles in water to derive settling velocity equations. However, they often overlook external factors like temperature, salinity, organic matter, and pH. Although laboratory experiments scrutinize the influence of these external factors on sedimentation velocity, sediment settling is not solely influenced by individual factors but rather by their collective interplay. Field observations offer the most accurate depiction of sediment deposition rates. However, the equipment used in such experiments may disrupt the natural sedimentation process and damage flocs. Moreover, measurements of sediment particle size from different instruments yield varied results. Additionally, this paper synthesizes the impact of suspended sediment concentration, particle size, shape, temperature, salinity, and organic matter on sediment settling velocity. Future research should focus on innovating new laboratory observation methods for sediment settling velocity and utilizing advanced scientific and technological tools for on-site measurements to provide valuable insights for further investigation into sediment settling velocity.
► Shallow sand-filled niches beneath drip emitters made reclamation of an impermeable saline-sodic soil possible. ► Low-salinity and low-pH zone under the drip emitter enlarged year by year. ► The ...average SAR in root zone decreased sharply in the first year, then leveled off in the next two years. ► After 3 planting years, survival rate of 81% was given when SMP was higher than −15kPa, and the yield was up to 865.7kg/ha.
The native soils of large areas of the Ningxia Plain in northwest China are saline-sodic, known as takyric solonetz, with very low saturated hydraulic conductivities (ks<0.1mm/d). A 3-year field experiment was conducted to determine if reclamation could be achieved while growing Lycium barbarum L. using drip irrigation where soil beneath the drip emitters, near the plants, was replaced with sand in niches that were 0.2m ground diameter and 0.2m deep. The purpose of sand-filled niche was to increase the area over which infiltration of water occurs thereby reducing the application rates to values that more closely matched the saturated hydraulic conductivity of the native soil. The initial values for ECe, pHs, and SAR of the surface soil was 12dS/m, 9.4 and 44.1(mmol/L)0.5, respectively. After deep tillage, beds (1m wide, 0.5m high) were formed. The drip lines were placed on beds covered with plastic. L. barbarum L. seedlings were then planted. Five water treatments were based on the soil matric potential (SMP), measured with tensiometers installed 0.2m beneath the emitter, used to trigger an irrigation of 5mm: the SMP levels were −5kPa (S1), −10kPa (S2), −15kPa (S3), −20kPa (S4), and −25kPa (S5). The salinity and SAR of the applied water were 2.14dS/m and 6.02(mmol/L)0.5. Considerable reclamation was achieved in three years. The low-salinity and the low-pH zone, which formed under the drip line during the first year, enlarged year by year. The average ECe and pHs in root zone increased with decreasing (more negative) SMP. The average SAR in root zone decreased sharply in the first year, then leveled off in the next two years. After 3 years, S3 and S4 had the better survival (∼80%) and higher fruit yields, around 900kg/ha, which were close to the level in local farmland. Our findings indicated that a sand-filled niche beneath the drip emitter could be adopted for the reclamation of saline-sodic wasteland in Ningxia Plain, northwest China, and an SMP of −10kPa in the first two years and −20kPa from the third year could be used to trigger drip irrigation while cropping L. barbarum L.
Freshwater resources are scarce in desert regions. Highly saline groundwater of different salinity is being used to drip irrigate the Taklimakan Desert Highway Shelterbelt with a double-branch-pipe ...system controlling the irrigation cycles. In this study, to evaluate the dynamics of soil moisture and salinity under the current irrigation system, soil samples were collected to a 2-m depth in the shelterbelt planted for different years and irrigated with different groundwater salinities, and soil moisture and salinity were analyzed. The results showed that both depletion of soil moisture and increase of topsoil salinity occurred simultaneously during one irrigation cycle. Soil moisture decreased from 27.4% to 2.4% for a 15-day irrigation cycle and from 26.4% to 2.7% for a 10-day-cycle, respectively. Topsoil electrical conductivity (EC) increased from 0.64 to 3.32 dS/m and 0.70 to 3.99 dS/m for these two irrigation cycles. With increased shelterbelt age, profiled average soil moisture (0-200 cm) reduced from 12.8% (1-year) to 7.1% (10-year); however, soil moisture in 0-20-cm increased, while topsoil salinity decreased. In addition, irrigation salinity mainly affected soil salinity in the 0-20-cm range. We conclude that water supply with the double-branch-pipe is a feasible irrigation method for the Taklimakan Desert Highway Shelterbelt, and our findings provide a model for shelterbelt construction and sustainable management when using highly saline water for irrigation in analogous habitats.
Green manure crops intercropping is an effective agricultural practice to alleviate water and nutrient deficit by improving soil properties in the Loess Plateau of China. However, green manure crops ...intercropping could cause water and nutrient competition, but the effects of different green manure crops intercropping on soil water and nutrient status are rarely evaluated. Thus, we conducted a field experiment to investigate the responses of soil moisture, nitrogen, and yield to green manure crops intercropping. Three intercropping patterns, apple–ryegrass (AR), apple–spring rape (AS), and apple–alfalfa (AA), were set up with a blank control (CK), which employed clean tillage in the inter-row and row. All treatments had no significant difference on evapotranspiration. At maturity, AR, AS, and AA treatments reduced soil organic matter content by 4.2%, 6.5%, and 18.8%, and total nitrogen content by 0.01%, 1.3%, and 20.3%, relative to CK, respectively. The water competition degree in AR, AS, and AA were 38.4%, 48.8%, and 64.6%, respectively. Ryegrass, spring rape, and alfalfa’s nitrogen use efficiency were 19.71%, 29.24%, and 39.42%, respectively. AR and AS treatments increased the apple yield by 11.7% and 5.7%, and water-use efficiency (WUE) by 14.4% and 7.5%, relative to CK, respectively. AA treatment reduced the apple yield by 6.9% and WUE by 6.8%, relative to CK. All treatments had no significant difference on apple quality. Therefore, in normal water years, we suggest adapting the ryegrass–apple tree intercropping pattern for apple production on the Plateau Loess, China.
The nature and extent of climate and soil nutrient controls in Chinese forests remain poorly resolved. Here, we synthesized the data on carbon–climate–soil in eastern China, and litter N was firstly ...taken into consideration, to examine the variation of net primary productivity (NPP) and its driving forces. Results showed that NPP had significant latitude pattern and varied substantially across climate zones. Bivariate analyses indicated that mean annual temperature (MAT), mean annual precipitation (MAP), soil N content (Nsoil), and annual litter N (Nre) were the main controlling factors in spatial pattern of forest NPP. Notably, partial general linear model analysis revealed that MAT, MAP, and Nre jointly explained 84.8% of the spatial variation of NPP. Among the three major factors, Nre explained more variation of forest NPP than the other two factors, and MAT and MAP affected NPP mainly through the change of litter N rather than via themselves, highlighting the importance of litter N in estimating forest NPP. However, to accurately describe the pattern of forest NPP in China, more detailed field measurements and methodologies on NPP and relevant confounding factors should be addressed in future studies.
Soil hydrothermal condition is one of the most important factors affecting crop growth in arid regions. This study aimed to investigate the effect of mulching and tillage on moisture and temperature ...variations in soil under drip irrigation in the arid Hetao Irrigation District, northwest China. Four treatments were included: (1) alternating ridges (40 cm wide and 20 cm high) and furrows (40 cm wide) with plots fully mulched with plastic film (RFM); (2) alternating ridges (40 cm wide and 20 cm high) and furrows (40 cm wide) with partial film mulch (only the plant rows mulched) (RPM); (3) flat tillage with plots fully mulched with plastic film (FFM); and (4) flat tillage with partial film mulch (only the plant rows mulched) (FPM). The ridge tillage and plastic film increased soil temperature and significantly conserved soil water, and thus increased the maize yield and water use efficiency (WUE). The RFM treatment had a greater effect than the RPM, FFM, and FPM treatments on the soil moisture and water storage over 0–70 cm in depth during the entire growing period in 2014 and 2015, indicating that full transparent plastic film mulch increased soil water status and promoted deep water percolation, and ridge tillage further enhanced water redistribution to deep soils. Furthermore, RFM proportionally increased soil temperature by 0.36 °C, 1.49 °C, and 1.27 °C above the temperatures under RPM, FPM, and FFM, respectively, in 2014 and by 1.19 °C, 1.62 °C, and 0.35 °C, respectively, in 2015. During the drought year of 2014, tillage influenced temperature more than mulching; however, mulching played a more important role in preserving thermal conditions than tillage during the humid year of 2015. Consequently, RFM increased the maize yield and WUE significantly. We conclude that a combined system of full plastic film mulch and ridge tillage creates beneficial soil hydrothermal conditions under drip irrigation and thus promotes the growth and performance of field crops.
•Water consumption and economic profits of maize production under different irrigation methods and water levels were evaluated in an arid area.•Lower Ky under drip irrigation indicates the lesser ...reduction in yield caused by the declined ETc than furrow irrigation.•Drip irrigation had the higher water consumption coefficient in maize’s R3-R6 stages than border and furrow irrigations.•Drip irrigation with SMP threshold of −30 kPa or 360-mm furrow irrigation is recommended.
Water scarcity is everywhere and more prominent in arid and semi-arid regions. Moreover, water allocation for irrigation is hit by other economic sectors for low per capita profit. It is inevitable to extend higher-efficient irrigations to replace conventional border irrigation. A three-year field experiment was conducted to examine the effects of different irrigation methods on maize’s water use and economics in the Hetao Irrigation District of China. Taking 525-mm border irrigation as the control, furrow and drip irrigations at three water levels were implemented. Furrow irrigation included 100 % (450 mm), 80 % (360 mm) and 60 % (270 mm) of the recommended level, while three threshold values of soil matric potential: −10 kPa, −30 kPa, and −50 kPa, were used to trigger drip irrigation. The grain yield, ETc (water consumption for the whole growing season), ETcs (water consumption during a special growth stage), and water productivity were affected significantly by the irrigation methods and water levels. The average ETc of border, furrow and drip irrigations was 537.4 mm, 401.8–514.4 mm, and 306.6–496.2 mm for different levels, respectively. On average 10 % of the irrigation water was lost through deep percolation under border irrigation, while 10.5–29.0 mm of groundwater contributed to ETc under drip irrigation with −50 kPa. The higher Kwc (water consumption coefficient) was observed in R3-R6 (Milk-Maturity) stages under drip than border and furrow irrigations. The lower Ky (yield response factor) of drip (0.68) than furrow (0.82) indicated the lesser reduction in yield induced by the decreased ETc under drip irrigation. The 360-mm furrow irrigation obtained a comparable grain yield and net profit with the control, but reduced water application by 31 %. Drip irrigation at −30 kPa enhanced yield by 15 %, increased net profit by 23 %, and reduced water application by 57 %. Thus, drip irrigation at −30 kPa is recommended as the priority to replace border irrigation for maize production in the study area. If drip irrigation is unavailable, a 360-mm furrow irrigation is also an alternative to reduce water application without compromising benefit.
Plastic mulched ridge-furrow irrigation is a useful method to improve crop productivity and decrease salt accumulation in arid saline areas. However, inappropriate irrigation and fertilizer practices ...may result in ecological and environmental problems. In order to improve the resource use efficiency in these areas, we investigated the effects of different irrigation amounts (400 (I1), 300 (I2) and 200 (I3) mm) and nitrogen application rates (300 (F1) and 150 (F2) kg N/hm
2
) on water consumption, salt variation and resource use efficiency of spring maize (
Zea mays
L.) in the Hetao Irrigation District (HID) of Northwest China in 2017 and 2018. Result showed that soil water contents were 0.2%–8.9% and 13.9%–18.1% lower for I2 and I3 than for I1, respectively, but that was slightly higher for F2 than for F1. Soil salt contents were 7.8%–23.5% and 48.5%–18.9% lower for I2 than for I1 and I3, but that was 1.6%–5.5% higher for F1 than for F2. Less salt leaching at the early growth stage (from sowing to six-leaf stage) and higher salt accumulation at the peak growth stage (from six-leaf to tasseling stage and from grain-filling to maturity stage) resulted in a higher soil salt content for I3 than for I1 and I2. Grain yields for I1 and I2 were significantly higher than that for I3 and irrigation water use efficiency for I2 was 14.7%–34.0% higher than that for I1. Compared with F1, F2 increased the partial factor productivity (PFP) of nitrogen fertilizer by more than 80%. PFP was not significantly different between I1F2 and I2F2, but significantly higher than those of other treatments. Considering the goal of saving water and nitrogen resources, and ensuring food security, we recommended the combination of I2F2 to ensure the sustainable development of agriculture in the HID and other similar arid saline areas.
•The most cracks occurred in the low EC-low SAR treatments.•High electrolyte concentration can inhibit the negative action of Na+.•Cracks suppressed the reduced infiltration rate caused by clay ...dispersion.•Saline water exceeding a SAR threshold, Mg2+/Na+ ratio affects crack formation.
The impact of saline water irrigation on soil infiltration properties can be assessed based on electrical conductivity (EC) and sodium adsorption ratio (SAR). However, current saline water quality assessment method does not account for crack formation and related preferential flow problems. To refine the current method of evaluating saline water quality, we incorporated the impact of saline water irrigation on soil cracking and proposed indicators that affect crack formation. An indoor soil column experiment was conducted with varying EC levels (3.0, 4.0, 5.0, 6.0 and 7.0 dS m−1) to observe changes in water-salt movement, turbidity of soil suspensions, and development of soil cracks under different salinity and sodicity conditions. To capture the multifaceted influence of Mg2+ in soil, we adjusted the coefficient of Mg2+ in the SAR equation to 0.6 (SARr), referencing the cation ratio of soil structural stability equation. The experimental results indicated that turbidity initially rose and then fell with increasing SARr values for saline water with an EC of 3.0–5.0 dS m−1, but this trend did not occur at EC > 5.0. Higher SARr values were associated with increased salt accumulation for saline water with equivalent EC levels. Abundant crack generation was observed at SARr around 4.0 (mmolc L-1)0.5 for the EC = 3.0 dS m−1 treatments, surpassing other treatments. In contrast, the soils treated with EC = 7.0 dS m−1 and SARr around 20.0 (mmolc L-1)0.5 showed minimal crack formation, exhibiting the fewest cracks among all treatments. EC and Na+ had similar and significant negative effects on crack width, area, and saturated hydraulic conductivity (Ksat). Their effects were stronger than those of Ca2+ and Mg2+. Although Ca2+ widened the cracks, Mg2+ had minimal impact on crack formation but affected soil salt accumulation capacity. Increasing the Mg2+/Na+ ratio reduced soil suspension turbidity, enhanced crack generation, and thus reduced Ksat. At varying EC levels, there was a SARr threshold. Above the threshold, higher Mg2+/Na+ ratios led to increased soil Ksat, with this threshold progressively increasing as EC level rose. Including Mg2+/Na+ as an assessment indicator was recommended to evaluate saline water quality. Saline water was categorized into two types according to the revised water quality assessment standard: those affected solely by EC and SARr, and those additionally influenced by Mg2+/Na+ values. Further research is required to refine SARr thresholds for precise classification under varying complex conditions.
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