Soil Water Changes Research Articles

Study on the Hydro‐Thermal‐Mechanical Characteristics of the Lime‐Soil Compaction Pile in the Forming Process

To study the effect of the lime‐soil compaction pile on the collapsible loess foundation and the influence of water‐heat‐force characteristics on the soil during compaction, the field test of lime‐soil compaction pile treatment of collapsible loess foundation is carried out. This paper monitors the process of soil temperature, water, and soil pressure change in the process of pile forming. According to the macroprocess and micromechanism of lime‐soil compaction pile treatment of collapsible loess foundation, the qualitative law of water‐heat‐force change in the process of pile forming is obtained. Meanwhile, the influence of soil damage is introduced in the process of compaction expansion. The model of pore expansion under linear damage conditions in the plastic zone is established. The formula of radial stress distribution under damage conditions is given. The influence of different damage factors on the expansion process is analyzed.

English

Variations in plant functional traits might reveal the adaptation strategies of vegetation under changing environment. However, few studies have focused on the variation of dominant plant functional traits in changing soil water content in marsh wetland of the arid regions. In this study, functional traits were investigated in the dominant species Phragmites australis growing at distinct soil water contents in marshes of the arid middle-lower reaches of the Shule River Basin in Northwest China. Three soil water gradients (33.38 ± 1.40, 15.97 ± 1.99 and 10.22 ± 1.61%) were identified from three marsh sites. Results showed that leaf thickness, specific leaf area, maximum height and leaf phosphorous content in P. australis were significantly varied from the high soil water to low soil water in arid marshes. Soil water content driven variations in functional traits of P. australis, mainly by its effect on soil salinity and available nitrogen, affected the functional traits of P. australis. In conclusion, in marshes of arid regions, P. australis adapted well to resource-poor habitats through the coordinated combination of multiple functional traits i.e., low specific leaf area, leaf nitrogen content and leaf phosphorous content, high leaf dry matter content and leaf thickness, which reflected that P. australis had conservative strategy. © 2021 Friends Science Publishers

Net positive soil water content following cover crops with no tillage in irrigated semi-arid cotton production

Conservation management practices such as no-tillage and cover cropping can reduce soil erosion, enhance soil biological activity, increase water capture and storage, and sequester C. Cover crops, however, utilize stored soil water during the winter months, and the water depletion is thought to have negative impacts on the subsequent cotton (Gossypium hirsutum L.) crop in semi-arid ecoregions where water resources are limited. The objective of this research was to quantify the long-term impacts of conservation tillage and cover crop use on volumetric water content of soil in an irrigated cotton production system. Soil water was measured in a long-term (established 1998) conservation system in Lamesa, TX and water dynamics during the 2015–2017 growing seasons are presented here. Volumetric water content was reduced by cover crops prior to their termination but was replenished by spring precipitation and deficit irrigation prior to planting cotton. A stepwise regression analysis was used to determine changes in soil water at depth. In each of the study years, soil water increased more with no-tillage following cover crop termination and decreased less during cotton growth than the conventionally tilled system. Cotton water use efficiency was not significantly different between treatments in any year. Results from this study challenge the concept that winter cover crops result in reduced in-season soil water in irrigated systems, a supposition that has limited adoption of conservation tillage and cover crop use on the Texas High Plains.

Planting practices and mulching materials improve maize net ecosystem C budget, global warming potential and production in semi-arid regions

Planting and mulching practices have long been used to change soil water storage, which may increase crop yields in dry-land farming systems. But, few research works have focused on mulching practices on the greenhouse gas intensity (GHGI), global warming potential (GWP), and net ecosystem C budget (NECB). Therefore, a two years field study was carried out in 2017–2018 to evaluate NECB, GWP, GHGI, biomass and maize production under six treatments: RPS: ridge tillage with film mulch on ridges and straw on furrows; RP: ridge tillage with film mulch on ridges; RT: ridge tillage without film mulch; FM: film mulching; SM: straw mulching; CT: conventional tillage. Finding of our results showed that both plastic film and straw mulching under two planting methods considerable reduced (41.3 %) GHGI, and improving the maize production and soil water status. The RPS treatment improved the soil environment, thus significantly increased corn productivity, C breathing loss, NECB, GWP, N2O, and CH4 emissions. The improve in NPP through RPS treatment is higher than the C loss in respiration, but seasonal NECB shows larger negative values because more NPP is removed as grain and straw. In the RPS treatment increased (22.3 %) the net GWP over flat planting without mulched, but decreased GHGI, due to increased (42.1 %) biomass productivity. The RPS treatment results in higher N2O, CO2 emissions and GWP, and therefore, has an adverse impact on the environment compared to CT treatment. However, the higher WUEg (72.1 %), WUEb (34.4 %), biomass and (83.1 %) grain yields obtained through RPS treatment may balance the negative ecological impacts associated with climate change. Thus, under dry farming systems, RPS treatment may be an effective water-saving management strategy that can increase WUE, biomass, corn yield and reduce the impact of global warming by increasing crop yields.

Linking Soil Water Changes to Soil Physical Quality in Sugarcane Expansion Areas in Brazil

Brazil is the world’s largest sugarcane producer with projections for expanding the current area by 30% in the coming years, mainly in areas previously occupied by pastures. We assess soil water changes induced by land-use change (LUC) for sugarcane expansion in the central-south region of Brazil. For that purpose, soil samples were collected in a typical LUC sequence (native vegetation–pasture–sugarcane) in two contrasting soil textures (i.e., sandy and clayey). Soil hydro-physical properties such as pores size distribution, bulk density, soil water content, water tension, and drainage time at field capacity, plant-available water, and S-index were analyzed. Our data showed that long-term LUC from native vegetation to extensive pasture induced severe degradation in soil physical quality and soil water dynamics. However, conventional tillage used during conversion from pasture to sugarcane did not cause additional degradation on soil structure and soil water dynamics. Over time, sugarcane cultivation slightly impaired soil water and physical conditions, but only in the 10–20 cm layer in both soils. Therefore, we highlight that sustainable management practices to enhance soil physical quality and water dynamics in sugarcane fields are needed to prevent limiting conditions to plant growth and contribute to delivering other ecosystem services.

Soil water dynamics under a warm-season cover crop mixture in continuous wheat

Cover crop technology can potentially benefit monoculture wheat systems in the semi-arid US Southern Great Plains, but the biggest hurdle in such regions where evapotranspiration exceeds precipitation is soil water. Cover crop impact on soil water use and availability is a major cause for concern in water-limited environments. The objective of this study was to evaluate the impact of cover crops, grazing, and intercrops on soil water dynamics under rainfed conditions. Seven treatments were evaluated, including conventional tillage (CT) and combinations of no-tillage (NT) with a cover crop mixture, grazed cover crops, and/or cash crop intercropping. The three-year study was conducted on a long-term NT continuous wheat system in the Texas Rolling Plains. Despite dry periods, the cover crop mixture produced 2141 to 3503 kg ha−1 dry herbage mass. Stored soil water was significantly lower within 60 days after planting for cover crop compared to no cover crop treatments. Stored soil water was 22–26% lower in cover crop plots at time of termination. In the final two years of the study, the positive change in stored soil water from cover crop termination to wheat planting was two to four times greater for cover crop treatments compared to non-cover crop treatments. The greater infiltration and water capture after termination has the potential to make up for the loss in soil water that cover crops used.

The physiological response of winter wheat under short-term drought conditions and the sensitivity of different indices to soil water changes

Studying the physiological responses of winter wheat to drought is conducive to learning to utilize biological water-saving technologies, such as regulating deficit irrigation and obtaining higher water use efficiency (WUE). However, the close relationship between the trend of responses of physiological functions in wheat and changes in soil moisture merits further study. In this study, a two-season pot experiment with three levels of water deficit (45 %–75 % FC, field capacity) was established at three growth stages, based on the theory that the drought-resistant physiological functions of winter wheat could respond to regulated deficit irrigation. The goal was to explore the effects of short-term drought-re-watering on yield and WUE and the sensitivity of wheat leaf physiological indicators to reflect changes in soil moisture. The results showed that the short-term drought in different periods after the jointing period reduced the yield of winter wheat by 2.03 %–64.39 % compared with the treatment of an adequate supply of water (75 %–85 % FC). Priority should be placed on ensuring irrigation during the jointing and filling periods. Treatments that experienced drought during the heading period (55 %–75 % FC) and then recovered to 75 %–85 % FC after flowering can improve the WUE by 5 %–22 %. The physiological function of drought resistance in winter wheat leaves responds noticeably to drought and the re-watering process in the range of 45 %–85 % FC. The maximum values of the activities of superoxide dismutase (SOD) and peroxidase and the contents of malondialdehyde and proline (Pro) during drought increased by 51.9 %, 15.1 %, 40.4 %, and 157.2 %, respectively, compared with those of the control group. The activity of catalase primarily increased after rehydration, and the maximum value was 1.5-fold that of the control group. After 14 days of rehydration, the physiological index values ​​of multiple treatments can be restored to the level of control, which proves that the physiological response within the range of 45 %–85 % FC water change is reversible. Based on the experimental data of the two seasons, the changes in activity of SOD and content of Pro more effectively reflect the changes in soil moisture than the other indicators (ROC analysis, AUC = 0.720−0.978) and have a significant correlation with yield (P < 0.05). Therefore, they can be considered as physiological reference tools to monitor the effect of irrigation and adjust its strategy.

Organic manure input improves soil water and nutrients use for sustainable maize (Zea mays. L) productivity on the Loess Plateau.

Long-term chemical fertilizer input causes soil organic matter losses, structural compaction, and changes in soil water and nutrient availability, which have been subdued in the most of dry farmland in China. The concept of “more efficiency with less fertilizer input” has been proposed and is urgently needed in current agriculture. Application of chemical fertilizer combined with organic manure (OM) could be a solution for soil protection and sustainable production of dry-land maize (Zea mays. L). Field research over three consecutive years on the Loess Plateau of China was conducted to evaluate the integrated effects of chemical fertilizer strategies and additional OM input on soil nutrients availability and water use in maize. The results showed that, after harvest, soil bulk density decreased significantly with OM application, concomitant with 11.9, 18.7 and 97.8% increases in topsoil total nitrogen, organic matter, and available phosphorus contents, respectively, compared with those under equal chemical NPK input. Water use in the 1.0–1.5 m soil profile was improved, therefore, the soil conditions were better for maize root growth, leaf area and shoot biomass of individual maize plants increased significantly with OM application. Optimized NPK strategies increased grain yield and water use efficiency by 18.5 and 20.6%, respectively, compared to only chemical NP input. Furthermore, additional OM input promoted yield and water use efficiency by 8.9 and 5.8%, respectively. Addition of OM promotes sustainable soil and maize grain productivity as well as friendly soil environmental management of dry land farming.

Differences in soil water changes and canopy temperature under varying water × nitrogen sufficiency for maize

Crop nitrogen (N) status is known to affect crop water status and crop water use. To investigate further the N effects on soil water changes and on canopy temperature, three water levels × four N levels were imposed on two growing seasons of maize in west central Nebraska, USA. Soil water changes were measured using a neutron probe, whereas canopy temperature was measured using infrared thermometers on a ground-based mobile platform. At all water levels, soil water losses over month-long intervals were generally greater as N levels increased. Given equal water levels, early afternoon canopy temperatures were usually lower with higher N levels, but no trend or even the opposite trend was occasionally observed. Jointly considering canopy reflectance and soil water depletion shows potential to explain much of the variation in estimated instantaneous water use among plots. However, determining the relative contributions of the canopy and soil factors on a particular day may require season-to-date knowledge of the crop. Further research on assimilating such sensor data for a combined stress coefficient would improve crop modeling and irrigation scheduling when variable water sufficiency and variable N sufficiency are simultaneously significant.

Response of Soil Water Dynamics to Rainfall on A Collapsing Gully Slope: Based on Continuous Multi-Depth Measurements

Soil water conditions play an important role in the formation of a collapsing gully, but we are still at the early stages of understanding how the soil water changes on the slope after different rainfall events due to a lack of high-frequency continuous field observations. This study aimed to reveal the response of soil water dynamics to rainfall events for different slope aspects and positions based on continuous multi-depth observations of soil water on a typical collapsing gully slope from 2017 to 2019 in Wuhua County, Guangdong Province, China. The vegetation characteristics and soil properties were investigated, and the storage of soil water was also calculated. The results showed that the dynamics and storage of soil water varied with the slope aspect, slope position and vegetation cover. The response time of the soil water to intensive rainfall events on the sunny slope was shorter than that on the shady slope, while soil water storage in the sunny slope was significantly lower than in the shady slope (p &lt; 0.01). For the different slope positions, the soil water response time to the intensive rainfall events on the upper slope was shorter than that in the middle slope, while the soil water storage in the middle slope was significantly higher than on the upper slope. This was mainly due to the redistribution runoff from the upper slope to middle slope, delaying the process by which rainwater infiltrated into the soil layers. Moreover, vegetation significantly allayed the response of soil water dynamics to an intensive rainfall event but increased the storage of soil water, owing to the protection of soil surface from rain and conservation of high soil clay content. The bare area in the middle position of the sunny slope was speculated to be the potential source of the collapsing gully because it lacked the cover of vegetation. Our findings highlight the importance of soil water dynamics on the formation of a collapsing gully and provided valuable insights for the optimization of soil conservation and management practices for collapsing erosion.

The Impact of Soil Water Content on Yield, Composition, Energy, and Water Indicators of the Bioenergy Grass Saccharum spontaneum ssp. aegyptiacum under Three-Growing Seasons

Raising water and energy productivity in agriculture can contribute to reducing the pressure on the limited freshwater availability and non-renewable energy sources. Bioenergy perennial grasses are efficient from a water perspective and can afford a low-energy cultivation system; however, crop selection and cultivation practices for minimizing land use change and maximizing resource use efficiencies remain a challenging task in view of sustainable bioeconomy development. The present work investigated the soil water effect on a long-term plantation of Saccharum (Saccharum spontaneum ssp. aegyptiacum), a bioenergy perennial grass holding great promise for semiarid Mediterranean areas. The plantation was in its 13th year following establishment and was subjected to three levels of irrigation for three successive growing seasons. Regression models between crop water use (CWU) and productivity, biomass composition, energy, and water indicators showed different prediction curves. Raising CWU (from 230 to 920 mm) enhanced the dry biomass yield (from 14.8 to 30.1 Mg ha−1) and the net energy value (from 257.6 to 511 GJ ha−1). On the same CWU range, unirrigated crops improved the energy efficiency (from 99.8 to 58.5 GJ ha−1), the energy productivity (from 5.6 to 3.4 Mg GJ−1) and the water productivity (from 114.5 to 56.1 MJ m−3) by reducing the water footprint (from 8.7 to 17.8 m3 GJ−1). Biomass composition was also superior in unirrigated crops, as the lower heating value, structural polysaccharides, and the acid detergent lignin were higher, while ash and soluble compounds were lower. Present findings demonstrated the good yield levels and persistence of Saccharum, improving our knowledge of plant responses to changing soil water availability to maximize energy and conserve natural resources, paving the way for sustainable bioeconomy development in the Mediterranean area.

Drought stress induces biosynthesis of flavonoids in leaves and saikosaponins in roots of Bupleurum chinense DC

Drought stress affects vegetative and reproductive growth processes and synthesis of secondary metabolites in plants. We assessed relevant indicators of vegetative and reproductive growth in Bupleurum chinense DC. during drought stress. Samples were collected on days 4, 8, 12, 20, and 24 of a drought treatment according to drought stress severity in order to elucidate potential effects on synthesis of flavonoids in leaves and saikosaponins in roots of B. chinense. The results showed that B. chinense can adapt to drought stress mainly by increasing concentrations of osmoregulatory substances (soluble protein and proline) and increasing activity of protective enzymes (superoxide dismutase and catalase), as observed on days 12 and 20 of the treatment. Secondary metabolite concentrations in B. chinense roots and leaves showed significant differences—drought stress increased saikosaponin concentrations in roots by 9.85% and 6.41% during vegetative and reproductive growth, respectively, on day 20, and saikosaponin concentrations in roots were higher during vegetative growth than during reproductive growth. In leaves, large amounts of antioxidants were consumed owing to drought stress, which decreased leaf rutin concentrations by 38.79% and 30.11% during vegetative and reproductive growth, respectively, as observed on day 20; overall, leaf rutin concentrations were lower during vegetative growth than during reproductive growth. Changes in soil water content are known to affect synthesis of secondary metabolites in medicinal plants by altering gene transcription, and affected genes may synergistically respond to soil water changes and alter concentrations of flavonoid in leaves and of saikosaponin in roots. The gene F3H down-regulates flavonoid production in leaves. Squalene epoxidase and β-amyrin synthase genes may be key genes regulating saikosaponin accumulation, and changes in their expression corresponded to accumulation of saikosaponins. Our results provide insights in B. chinense adaptation to drought stress through physiological changes and regulation of secondary metabolite production in different plant tissues.

Effects of Earthworm Cast Application on Water Evaporation and Storage in Loess Soil Column Experiments

Earthworm cast is a common bio-organic fertiliser, which can effectively improve soil fertility and structure. However, only a few studies have focused on the effect of earthworm cast on soil water movement. In this study, loess soil was used to determine the effects of earthworm cast application on soil evaporation. The effects on water storage capacity and capillary upward movement were also investigated. A laboratory-based soil column experiment using earthworm cast with different particle sizes (1–3 × 1–2 cm and 3–5 × 2–4 cm) and three application doses (5%, 7.5%, and 10%) was carried out. The daily evaporation and volume of capillary ascension were monitored. The addition of earthworm cast clearly affected the soil evaporation by changing soil water storage capacity and capillary water upward movement. Compared with control soil, the application of 5% small-particle cast reduced the soil cumulative evaporation by 5.13%, while the cumulative evaporation was higher in all large-particle cast treatments. The upward capillary water movement increased with increasing dose of earthworm cast, but decreased with increasing particle size. Overall, the addition of earthworm cast clearly enhanced the water storage capacity of the soil, with the small-particle cast having greater effects than the large-particle cast. We concluded that the application of 5% small-particle earthworm cast can enhance soil water retention and reduce soil evaporation.

Deficit and Recovery of Deep Soil Water Following a Full Cycle of Afforestation and Deforestation of Apple Trees on the Loess Plateau, China

Land-use change could substantially alter the soil water balance and hydrological cycles; however, little is known on the changes in deep soil water following a cycle of afforestation and deforestation. The purpose of this study was to quantify the soil water deficit in an apple orchard and subsequent replenishment of deep soil water after the orchard was felled. Soil water changes were quantified using the “space-for-time” method through a paired plot design. The results showed that the water storage in deep soil (&gt;3 m in depth) began to decrease when the apple tree reached about 10 years of age. The cumulative deficit of deep soil water storage in the 3–18 m soil depth could reach about 1200 mm; however, deep soil water was so depleted that apple trees can no longer adsorb water from the deep soil when apple trees are older (&gt;22 years old). After the apple orchard was converted to cropland, precipitation replenished the desiccated deep soil to a depth of about 7 m in the first two years, but thereafter, both water recovery amount and the advance rate of the wetting front were slowed down. After 15–16 years of recovery, soil water storage increased by 512–646 mm, accounting for 42.7–53.8% of the total cumulative soil water deficit caused by the apple orchard. However, it will take more than 26 years for soil water to be replenished to the level of the original cropland prior to planting apple trees. The considerable water deficit after afforestation and subsequent long water recovery time following deforestation extend our understanding of the effect of deep-rooted trees on water balance at the decade scale.

Root capacitance measurements allow non-intrusive in-situ monitoring of the seasonal dynamics and drought response of root activity in two grassland species

Background and aimsIn this study, the potential of non-intrusive root electrical capacitance (CR) measurements for monitoring the seasonal changes and drought response of root activity was tested on two grassland species in a climate change experiment.MethodsCR was detected between a ground electrode inserted into the soil and a plant electrode attached to the stem of the perennial grass Stipa borysthenica and the biennial herb Crepis rhoeadifolia in control and drought plots throughout two growing seasons. A pilot study revealed that CR was strongly correlated with root biomass for a given time and soil water content. The effect of changing soil water content on the measured CR value was accounted for by means of species-specific experimental calibrations.ResultsRoot activity (CR) was found to peak at the flowering stage in late spring (S. borysthenica) or early summer (C. rhoeadifolia). Both the natural shortage of rainfall and the experimental summer drought reduced root activity in both species. Stipa borysthenica displayed great plasticity in root activity, including quick post-treatment recovery during the rainy autumn. The changes observed in root activity were similar to those previously recorded using conventional root investigation techniques (i.e. destructive, minirhizotron, ingrowth core) in temperate grasslands.ConclusionsRoot capacitance measurements proved to be adequate for monitoring root activity in situ in natural grassland. The method could be particularly useful in studies where plant injury or soil disturbance need to be avoided.

Using an improved SWAT model to simulate hydrological responses to land use change: A case study of a catchment in tropical Australia

Land use change is one of the dominant driving factors of watershed hydrological change. Thus, hydrological responses to land use changes require detailed assessments to ensure sustainable management of both water resources and natural ecosystems. The Soil and Water Assessment Tool (SWAT) model has been widely used to simulate the impacts of land use change on water balance. However, the original SWAT model has poor performance in estimating the leaf area index (LAI) of different vegetation types for tropical areas. The objective of this study was to simulate the impact of different land use change scenarios (deforestation, afforestation and urbanization) on the water balance, using an improved SWAT model with vegetation growth calibrated from MODIS LAI data. The North Johnstone River catchment in wet tropical eastern Australia was selected as the case study area. Results showed that the modified SWAT model was able to reproduce smoothed MODIS LAI with NSE ≥ 0.59 (NSE < 0 for default SWAT), R2 ≥ 0.70 (R2 ≤ 0.66 for default SWAT), and |PBIAS| ≤ 2.5% (|PBIAS| ≥ 42% for default SWAT), and to predict monthly streamflow well with NSE ≥ 0.92 (NSE ≥ 0.90 for default SWAT), R2 ≥ 0.94 (R2 ≥ 0.90 for default SWAT). It is noted that SWAT-T had |PBIAS| ≤ 10% while |PBIAS| ≤ 5% for default SWAT. Land use change impacted all hydrological variables, with the impact on surface runoff being the most notable at yearly scale (8.9%, 5.7%, −9.5% and 15.9% for scenario 1, 2, 3 and 4, respectively). Absolute changes of surface runoff under land use change scenarios differed across months, with the most notable absolute change occurring during the wet season (December to May) (1.2 ~ 6.6 mm, 1.0 ~ 3.5 mm, −7.3 ~ -1.1 mm and 3.0 ~ 9.0 mm for scenario 1, 2, 3 and 4, respectively). Urbanization increased surface runoff (5.7% and 15.9% for scenario 2 and 4, respectively) and decreased lateral runoff (−0.7% and −1.3%) and groundwater (-0.9% and −3.5%), but produced no clear change in total runoff (0.2% and 0.2%), actual evapotranspiration (−0.3% and −0.3%), and soil water (0.5% and 0.7%) at the annual time scale. Furthermore, afforestation could decrease surface runoff (−9.5% for scenario 3) and soil water (−2.0%), increase evapotranspiration (1.7%), and lead to slight changes (absolute values ≤0.8%) in other hydrological variables at the annual time scale. A strong positive correlation (r ≥ 0.94) was observed between annual rainfall and total runoff for forest-evergreen, range-grasses, and urban land use. Forest-evergreen generally produced less total runoff than range-grasses and urban land use under conditions of the same rainfall, terrain slope, and soil texture. In addition, urban land use generally produced more surface runoff and less lateral runoff and groundwater than forest-evergreen and range-grasses under the same conditions. These results contribute important information for development of effective adaptation strategies and future policy plans for sustainable water management in tropical eastern Australia.

Cover Crops and Frond Piles for Improving Soil Water Infiltration in Oil Palm Plantations

Oil palm plantations may cause problems in the hydrological cycle due to a low soil water infiltration capacity. In this study, we (a) compared oil palm plantations with other land use types, and (b) within oil palm plantations, analyzed whether legume cover crops and the deposition of frond piles can change soil water infiltration. The study was conducted in the lowlands of Sumatra in mixed jungle rubber stands, and in monospecific rubber and oil palm plantations by using ring in filtrometers. Observed in filtration rates in jungle rubber and monospecific rubber stands (approximately 20 cm h−1) were about 5 times higher than in oil palm plantations, underlining the problem. Within the oil palm cultivation system, a legume cover crop, as well as the deposition of palm fronds, significantly enhanced infiltration rates. We conclude that indeed low soil water infiltration is very low in conventional oil palm plantations. Management including the planting of cover crops and deposition of fronds may offer options for improving the situation.

Determining the Shear Strength and Permeability of Soils for Engineering of New Paddy Field Construction in a Hilly Mountainous Region of Southwestern China.

As a constructed wetland ecosystem, paddy field plays an irreplaceable role in flood storage and detention, groundwater replenishment, environmental protection, and ecological balance maintenance. New paddy field construction can give full play to the production and ecological functions of paddy field and can adjust the development structure of the agricultural industry effectively. The soil properties of shear strength and permeability, which provide a theoretical basis for engineering design, construction, and post-operation, are important indexes in the site selection of new paddy field. The shear strength and permeability properties of soils from different land use types (vegetable field, gentle slope dryland, corn field, grapery, and abandoned dryland) for engineering new paddy field construction were investigated in this study. The results showed that the soil water content had a significant effect on the soil shear strength, internal friction angle, and cohesion. The total pressure required for soil destruction decreased with increasing water content under the same vertical pressure, resulting in easier destruction of soils. The internal friction angle decreased with increasing soil water content, and the soil cohesion first increased and then decreased with increasing soil water content. Considering that paddy fields were flooded for a long time, the soil strength properties had certain water sensitivity. Effective measures must be taken to reduce the change in soil water content, so as to ensure the stability of the embankment foundation, roadside ditch foundation, and cutting slope. In addition, the influence of changing soil water content on the strength properties of paddy soils should be fully considered in engineering design and construction, and the soil bulk density at the plough pan should reach at least 1.5 g cm−3 or more to ensure better water retention and the anti-seepage function of paddy field. The study can provide construction technology for engineering new paddy field construction in a hilly mountainous region of southwestern China.

Changing Rainfall Patterns Over the Western Lake Erie Basin (1975–2017): Effects on Tributary Discharge and Phosphorus Load

AbstractIn agricultural watersheds, shifting climate and hydrologic patterns present an immediate and future risk to both farm productivity and downstream aquatic ecosystems. Here, our objective was to evaluate long‐term spatiotemporal trends in rainfall amount and intensity within the Maumee River‐Lake Erie system and quantify the effects of rainfall patterns on streamflow and phosphorus loading. Across the watershed, annual rainfall increased by 102 ± 115 mm (11 ± 13%) from 1975–2017. Heavy (25.4–76.2 mm) and very heavy (&gt;76.2 mm) rainfall accounted for most of the increase in total rainfall, with observed increases of 45 ± 32% that occurred primarily during spring and summer. Trends in streamflow for 12 monitored subwatersheds generally followed patterns in rainfall, as discharge increased by 19 ± 32%. Discharge‐to‐rainfall ratio increased in 9 of 12 subwatersheds despite no change or increases in watershed storage capacity, suggesting that increasing rainfall intensity that exceeds short‐term watershed storage capacity (i.e., during/immediately following the rainfall event) may control patterns of discharge more than long‐term gains in watershed storage (i.e., changes in soil water holding capacity). Long‐term trends in phosphorus (total phosphorus and soluble reactive phosphorus) load indicate that changes in rainfall amount and intensity have substantially contributed to increased loading through increased discharge volumes. Differences in total phosphorus and soluble reactive phosphorus concentration trends also highlight how concomitant changes in rainfall and land management practices have influenced loading. Findings therefore suggest that changing patterns in rainfall amount and intensity have and will likely continue to pose a significant challenge to conservation efforts in agricultural landscapes aiming to decrease phosphorus delivery to surface waters.

Effects of Water Deficit on Growth, Biomass Allocation and Photosynthesis of &lt;i&gt;A. senegal&lt;/i&gt; Seedlings from Nguru and Gujba Provinces of Yobe State, North Eastern Nigeria

Acacia senegal (L) Willd is a multipurpose tree species that occurs throughout semi-arid Africa. Poor yields of gum from the species in the semi-arid region of Nigeria may be due to more frequent drought events. It is not yet clear whether some populations of A. senegal may respond differently to any encroaching drought. The effects of water deficit on growth, biomass allocation and photosynthesis of A. senegal seedlings from Nguru and Gujba province of Yobe state, North Eastern Nigeria were studied under glasshouse conditions for 120 days. Plants were subjected to three watering regimes; control (well-watered) conditions corresponding to 25% gravimetric water content (GWC), mild water deficit at 15% (GWC) and severe-water-deficit at 10% (GWC), respectively. There was a highly significant difference in stomata conductance among the treatments (F2, 84=11.38, P&lt; 0.001) in relation to water deficit. There was no statistical difference in quantum yield between the two provenances (F1, 84 =0.15, P=0.695) and interaction between treatment and provenances was also not significant (F2, 84= 2.14, P=0.124). mean root length between the provenances were significantly different (F2,84 =0.60, P&lt; 0.001) however Root length was not statistically significant between treatments (F2,84= 0.60, P= 0.550). Plant biomass, stomata conductance, quantum yield, chlorophyll fluorescence, relative water content, root length and root: shoot ratios were highly responsive to changes in soil water. It was concluded that A. senegal is capable of physiological adjustment in response to soil moisture as a form of ecological adaptation.Keywords: biomass allocation, provenances, relative water content, stomata conductance.