Mean Soil Moisture Content Research Articles

Development and Evaluation of a Pilot Scale GravityCentre Pivot Sprinkler Irrigation System under Okra (Abelmoschusesculentus) Cultivation

A pilot scale gravity-centre pivot sprinkler irrigation system (GCPSIS) was designed, constructed and evaluated at two operating speeds on an Okra field at the experimental field of the Department of Agricultural and Environmental Engineering of Joseph Sarwuan Tarka University Makurdi, Analysis of variance (ANOVA)at P(0.05)from the data sets showed mean Soil Wetting Depth (SWD) ranging between 7.75±0.35 to 13.75±035cm/hr and 5.90±0.14 to 3.15±0.49cm/hr at speeds 5 and 7 rpm respectively and were not significantly different both in speeds, orientation and distances from the pivot station. The mean Soil Moisture Content (SMC) was 15.95 ±6.30 and 11.78 ±1.81% at 21-40cm depth at 5rpm and 7rpm respectively. The average Soil Bulk Density (SBD) at 0-20, and 21-40cm soil depth was1.23+0.5g/cm3 and 1.23±0.13g/cm3 respectively at 5rpm indicating a higher variability. At 7rpm mean values were 1,31±0.06 and 1.28+0.06g/cm3 at 0-20, and 21-40cm soil depth respectively indicating similar variability at both depths. Both speed and depth were not significant with respect to the SBD but speed was significant for SMC. Application Efficiency (Ea), Coefficient of Uniformity (CU), Distribution Uniformity (DU) along the pivot lateral complied with acceptable standards and were 77.67, 45.35 and 85.80 % respectively at 5rpm and 86.83, 44.89 and 94.03% at 7rpm respectively. The and Nozzles Discharge (ND) was highest (9.12 L/min) at the nozzle closest to the pivot station, high (9.00 L/min) at the middle nozzle and low (8.94 L/min) at the nozzle at the end of the lateral line in the first week and decreased slightly up to week five due to clogging.

Effect of Land Ploughing Methods and Leveling Techniques on Wheat Production in the Upper Terraces of the Northern State - Sudan

Precision land leveling must be treated as a precursor technology for improving crop yield, enhancing input-use efficiency and ensuring long-term sustainability of the resources. A field experiment was conducted in Dongola Agricultural Research Farm, Northern State, for two successive seasons to investigate the effect of three type of ploughing; heavy disc harrow (H1), disc plough (H2) and no-ploughing (H3), and three land leveling techniques, Laser (L), Scraper (S) and traditional (T),on wheat production. The experiment was arranged in a strip split plot design and the treatments were replicated three times.
 The results indicated that effective field capacity, fuel consumption, and slippage were significantly affected by ploughing method. Laser land leveling recorded the highest fuel consumption (16.3 L/hr), and the lowest field efficiency (55%). while the heavy disc harrow recorded the highest effective field capacity (0.98 ha/hr), field efficiency (71.2%) and wheel slippage (8.1%). The soil moisture content (db %) was increased with time and depth. The highest mean soil moisture content was obtained with the laser land leveling and heavy disc harrow treatment at 75-100cm soil depth as 24.82%. The results revealed that the highest average grain yield (4.63 ton/ha) and infiltration rate (31cm/hr) were also recorded by the laser land leveling and heavy disc harrow. The treatments showed significant differences at the 5% level between the treatments for the parameters measured. Multiple regression analysis showed a highly significant effect (P≤ 0.001) of laser leveling with disc harrow ploughing on grain yield, compared to the other treatments used in the study (R2 = 0.40). The relation between the grain yield (Y) and the treatments: X1 ploughing, X2 leveling is summarized in the following equation: 
 Y = 2.875 + 0.552X1 + 0.254X2
 The study concluded that, although Laser leveling has increased the grain yield with high cost, yet it is not an expensive technique when the cost is distributed over the period of Laser leveling. The highest grain yield was obtained by the heavy disc harrow with laser land leveling.

The UKSCAPE-G2G river flow and soil moisture datasets: Grid-to-Grid model estimates for the UK for historical and potential future climates

Abstract. Appropriate adaptation planning is contingent upon information about the potential future impacts of climate change, and hydrological impact assessments are of particular importance. The UKSCAPE-G2G datasets were produced, as part of the Natural Environment Research Council (NERC) UK-SCAPE (UK Status, Change and Projections of the Environment) programme, to contribute to this information requirement. They use the Grid-to-Grid (G2G) national-scale hydrological model configured for both Great Britain and Northern Ireland (and the parts of the Republic of Ireland that drain to rivers in NI). Six separate datasets are provided, for two sets of driving data – one observation-based (1980–2011) and one climate-projection-based (1980–2080) – for both river flows and soil moisture on 1 km × 1 km grids across Great Britain and Northern Ireland. The river flow datasets include grids of monthly mean flow, annual maxima of daily mean flow, and annual minima of 7 d mean flow (m3 s−1). The soil moisture datasets are grids of monthly mean soil moisture content (m water / m soil), which should be interpreted as depth-integrated values for the whole soil column. The climate-projection-based datasets are produced using data from the 12-member 12 km regional climate model ensemble of the latest UK climate projections (UKCP18), which uses RCP8.5 emissions. The production of the datasets is described, along with details of the file format and how the data should be used. Example maps are provided, as well as simple UK-wide analyses of the various outputs. These suggest potential future decreases in summer flows, annual minimum 7 d flows, and summer/autumn soil moisture, along with possible future increases in winter flows and annual maximum flows. References are given for published papers providing more detailed spatial analyses, and some further potential uses of the data are suggested. The datasets are listed in Table 1.

Effect of moisture conservation techniques on almond (Prunus dulcis) productivity under rainfed conditions

A field experiment was conducted to study the effect of moisture conservation techniques on productivity enhancement in almond (Prunus dulcis Mill) during 2010-11 to 2012-13 at Srinagar, Jammu and Kashmir. Treatment sincluded five water harvesting techniques, viz. half-moon (W1), full-moon (W2), cup and plate (W3), trench (W4) and control (W5) and three mulch materials, viz. plastic mulch (M1), organic mulch (M2) and control (M3) were laid out in factorial randomized block design with three replication. The experimental results revealed that maximum mean trunk cross sectional area (266.82 cm2), nut yield (5.37 kg/tree), productivity efficiency (19.47 g/cm2 TCSA) and soil moisture content (13.48%) were recorded in full moon water harvesting technique. Among mulch material, plastic mulch found better in respect to TCSA (255.59 cm2), nut yield (4.99 kg/tree), productivity efficiency (18.88 g/cm2 TCSA) and soil moisture content (12.86%) compared to other treatments. The combined effect of water harvesting and mulching indicated that maximum TCSA (270.48 cm2), nut yield (5.82 kg/tree), productivity efficiency (20.92 g/cm2 TCSA) and soil moisture (13.98 %) were recorded in full moon water harvesting + plastic mulch in almond cultivar Non Pareil under rainfed conditions of north west Himalayan regions of India.

Latitudinal and Altitudinal Patterns and Influencing Factors of Soil Humus Carbon in the Low-Latitude Plateau Regions

The composition of forest soil organic matter is an important part of the global carbon cycle, which is effective by temperature and moisture. As we all know, the temperature and moisture in the low-latitude plateau regions are very sensitive to changes in latitude and altitude. However, the composition of soil organic matter response to changes in latitude and altitude in the low-latitude plateau regions is unknown. In this study, the effects of latitude (21–29° N) and altitude (500–4000 m) on soil organic carbon (SOC) and humic acid carbon (HAC), fulvic acid carbon (FAC), and humin carbon (HMC) in forest surface soil (0–10 cm) were investigated. The results showed that the contents of soil organic carbon and humus increased with the increase in altitude and latitude. The effect of altitude on the composition of organic matter was significant only at 23° N to 25° N. The composition of organic matter is not only regulated by mean annual temperature (MAT) and soil moisture content (SMC) but also affected by soil pH, carbon to nitrogen ratio (C/N), and powder. The soil surface layer (0–10 cm) carbon sequestration capacity in high-latitude and high-altitude areas is stronger than that in low-latitude and low-altitude areas. As a consequence, in today’s response to global climate change, the high carbon sequestration capacity of high latitude and high altitude areas should be given attention and protection.

A decadal record of soil moisture space–time variability over a south‐east Australian catchment

AbstractSemi‐arid to temperate south‐east Australian catchments with agricultural landscapes demonstrate unique hydro‐climatic characteristics. Understanding the behaviour of soil moisture over such catchments and the influence of driving factors are crucial for hydrologic, climatic and agricultural applications. However, this is challenging due the complex, non‐linear relationship between these factors and soil moisture, and the lack of long‐term catchment scale data records. To address this, spatial and temporal patterns of soil moisture over two south‐east Australian river catchments (i.e., Krui and Merriwa) and the influence of soil texture, topography, vegetation and rainfall on soil moisture variability were evaluated using a decadal in‐situ dataset. This unique in‐situ soil moisture monitoring network is established over a semi‐arid to temperate catchment representing typical south‐east Australian agricultural landscape and the data record has captured some major climatic events. Time stability of catchment‐scale soil moisture and the potential of predicting catchment mean soil moisture content using one representative station were also examined using a linear regression model. Soil texture was found as the dominating factor driving the spatial variability of soil moisture in the area. The temporal patterns of soil moisture showed a positive agreement with vegetation dynamics and rainfall at topsoil layers (0–5 cm and 0–30 cm). A higher spatial variability of soil moisture was observed during dry catchment conditions compared to wet catchment conditions. The deeper soil layers (30–60 cm and 60–90 cm) showed highly stable soil moisture values, which might be the driving force of the agriculture in the area. A linear regression based prediction model demonstrated a good potential in estimating spatial mean soil moisture content from one representative station. The results are useful in parameterization of soil moisture variability in land surface, climatic and hydrologic models, agricultural applications and in remote sensing of soil moisture.

The Patitapu Soil Moisture Network (PTSMN) dataset and its deployment in New Zealand’s hill country

A significant portion of New Zealand’s beef and sheep pastoral farming systems are located in the East Coast hill country of the North Island. In these landscapes, one of the main drivers of pasture growth is the highly variable soil water content. Decision making about fertiliser applications, stock and feed budgeting are guided by pasture growth models which rely on soil water information. However, due to the difficulties related to conventional soil moisture data collection, soil water dynamics are still poorly understood in hill country. To capture spatial and temporal soil moisture variability on diverse terrain positions, a soil moisture monitoring network was established at the field scale. The Patitapu Soil Moisture Network (PTSMN) is composed of twenty multi-sensor probes, collecting data from four consecutive depths at 0.1 m intervals. The paper describes the PTSMN deployment and the strategic selection of sensor locations through an extensive spatial analysis and discusses the challenges associated with the network deployment in an operating hill country farm. Additionally, we demonstrate the non-normal nature of soil moisture distribution and that Year 1 and Year 2 showed similarly shaped density curves in the 0.2 − 0.4 m soil depths indicating temporal stability. Similar magnitudes of temporal stability suggested the PTMSN is a temporally stable network although stability changed with depth. Results indicated that soil moisture variability decreased with depth and that higher mean soil moisture content was associated with low variability. Descending and ascending transition stages, i.e., drying, and rewetting periods resulted in the highest spatial variability. As PTSMN is a member of the International Soil Moisture Network, the calibrated, quality checked 2-year dataset has been made accessible online. The presented soil moisture dataset is expected to contribute to the research of near-surface and root-zone soil water dynamics and to assist with the establishment of future networks.

Grid-based simulation of soil moisture in the UK: future changes in extremes and wetting and drying dates

Soil moisture, typically defined as the amount of water in the unsaturated soil layer, is a central component of the hydrological cycle. The potential impacts of climate change on soil moisture have been less specifically studied than those on river flows, despite soil moisture deficits/excesses being a factor in a range of natural hazards, as well as having obvious importance for agriculture. Here, 1 km grids of monthly mean soil moisture content are simulated using a national-scale grid-based hydrological model, more typically applied to look at changes in river flows across Britain. A comparison of the soil moisture estimates from an observation-based simulation, with soil moisture deficit data from an operational system developed by the UK Met Office (Meteorological Office Rainfall and Evaporation Calculation System; MORECS), shows relatively good correspondence in soil drying and wetting dates, and in the month when soils are driest. The UK Climate Projections 2018 Regional projections are then used to drive the hydrological model, to investigate changes in occurrence of indicative soil moisture extremes and changes in typical wetting and drying dates of soils across the country. Analyses comparing baseline (December 1981–November 2011) and future (December 2050–November 2080) time-slices suggest large increases in the spatial occurrence of low soil moisture levels, along with later soil wetting dates, although changes to soil drying dates are less clear. Such information on potential future changes in soil moisture is important to enable the development of appropriate adaptation strategies for a range of sectors vulnerable to soil moisture levels.

Greenhouse Gas Emissions Response to Fertilizer Application and Soil Moisture in Dry Agricultural Uplands of Central Kenya

In sub-Saharan Africa, agriculture can account for up to 66% of anthropogenic greenhouse gas (GHG) emissions. Unfortunately, due to the low number of studies in the region there is still much uncertainty on how management activities can affect these emissions. To help reduce this uncertainty, we measured GHG emissions from three maize (Zea mays) growing seasons in central Kenya. Treatments included: (1) a no N application control (C); (2) split (30% at planting and 70% 1 month after planting) mineral nitrogen (N) applications (Min—100 kg N ha−1); (3) split mineral N + irrigation (equivalent to 10 mm precipitation every three days—MI); (4) split mineral N + 40 kg N ha−1 added as manure (MM—total N = 140 kg ha−1); and (5) split mineral + intercropping with faba beans (Phaseolus vulgaris—MB). Soil CO2 fluxes were lower in season 1 compared to seasons 2 and 3 with fluxes highest in Min (p = 0.02) in season 2 and lowest in C (p = 0.02) in season 3. There was uptake of CH4 in these soils that decreased from season 1 to 3 as the mean soil moisture content increased. Cumulative N2O fluxes ranged from 0.25 to 2.45 kg N2O-N ha−1, with the highest fluxes from MI during season 3 (p = 0.01) and the lowest from C during season 1 (p = 0.03). The average fertilizer induced emission factor (0.36 ± 0.03%) was roughly one-third the default value of 1%. Soil moisture was a critical factor controlling GHG emissions in these central Kenya highlands. Under low soil moisture, the soils were CH4 sinks and minimal N2O sources.

Effects of conservation tillage, phosphorus and variety on selected soil physical properties and cowpea productivity at Minna in Nigeria’s Southern Guinea Savanna

This study was conducted to evaluate the influence of conservation tillage, inorganic phosphorus fertilizer and variety on soil physical properties and cowpea productivity at Minna in the Southern Guinea Savanna of Nigeria. Three tillage practices (zero, reduced and ridged), three phosphorus rates (0, 30 and 60 kg P2O5 ha-1) and three cowpea varieties (IT93K-452-1, IT99K-573-1-1 and IT90K277-2) were factorially combined and laid out in randomized complete block design with three replications. Two crops of cowpea were cultivated sequentially. Soil and crop indices used for the evaluation were soil bulk density, soil organic carbon content, mean weight diameter, soil moisture content, haulm yield and grain yield. Conservation tillage significantly affected the four soil indices while phosphorus rates significantly affected soil organic carbon content, mean weight diameter and soil moisture content. There was varietal effect on soil organic carbon content and soil moisture content. Conservation tillage methods influenced haulm yield significantly but had no significant effect on grain yield. Phosphorus application and variety, on the other hand, significantly affected both haulm and grain yields. Notably, in the early harvest, application of 60 kg P2O5 ha-1 raised haulm yield from 2,489 kg ha-1 (untreated control) to 5,482 kg ha-1 , and grain yield from 614 kg ha-1 (untreated control) to 1,440 kg ha-1 , representing 120% and 135% increments for haulm and grain yields respectively. Farmers are advised to combine either zero or reduced tillage with 60 kg P2O5 ha-1 and IT99K573-1-1 for maximum haulm and grain yields.

Effects of different tillage systems on soil properties, and yield and yield components of barley

ABSTRACT This study was carried out to assess the influence of tillage systems on soil characteristics as well as barely yield. The two-year experiment with the tillage systems (NT, no-tillage; MT, minimum-tillage; and CT, conventional-tillage) and barley cultivars was done. Vetch was pre-planting in the rotation with barley. About 30% of vetch residue remained in the NT and MT systems, but in CT, these residues were buried by moldboard. Results showed that NT was superior to MT and CT in terms of the soil properties, earthworm number and earthworm body mass. Remains of vetch, as a pre-planted crop, were effective in increasing these indicators. Also, the improvement of these indicators made the no-tillage superior to the MT and CT in terms of geometric mean diameter, mean weight diameter and soil moisture content. In contrast, soil porosity was higher in CT system. In conclusion, soil structure improved during the two years of the experiment when MT or NT was used, while CT was not effective in improving the soil structure. Grain yield (5973 kg ha−1) and NFS (5163) were higher in NT than MT and CT, suggesting that the change in soil structure has provided a better environment for the yield.

Effects of drip tape modes on soil hydrothermal conditions and cotton yield (Gossypium hirsutum L.) under machine-harvest patterns.

BackgroundThe layout of drip tapes under mulch has changed in Xinjiang, China, with the development of machine-harvest cotton (Gossypium hirsutum L.) planting technology. This study aims to demonstrate the effects of drip tape modes on soil hydrothermal conditions, cotton yield, and water use efficiency (WUE) of machine-harvest cotton under mulch in Xinjiang.MethodsA field experiment was conducted to set up two machine-harvest cotton planting patterns (T1: the cotton planting model with one film, two drip tapes and six rows; T2: the cotton planting model with one film, three drip tapes and six rows), and a conventional planting mode (T3: the cotton planting model with one film, two drip tapes and four rows) as a control.ResultsOur results showed that the heat preservation and warming effects of the cotton planting model with one film, two drip tapes and six rows and the cotton planting model with one film, three drip tapes and six rows were better than that of the conventional planting mode. Soil temperature under the mulching film quickly increased and slowly decreased, which was beneficial to the early growth and development of cotton. The mean soil moisture content of the 0–60 cm soil layer in the cotton planting model with one film, three drip tapes and six rows was significantly higher than the other two treatments at the middle and late stage of cotton growth (90 days after sowing (DAS) and 135 DAS). Moreover, the water holding capacity of the middle and upper part of the tillage layer in the cotton planting model with one film, three drip tapes and six rows was the best. At the medium cotton growth stage, the main root layer in the cotton planting model with one film, three drip tapes and six rows formed a desalination zone. At the late cotton growth stage, the soil salinity content of the 0–60 cm soil layer showed that the cotton planting model with one film, three drip tapes and six rows was the lowest, the cotton planting model with one film, two drip tapes and six rows was the highest, and the conventional planting pattern was in the middle. Among these three modes, the cotton planting model with one film, three drip tapes and six rows was more efficient in controlling soil salt accumulation. The agronomic traits and cotton quality in the cotton planting model with one film, three drip tapes and six rows were better than that for the other two treatments. Compared with the other treatments, the cotton yield in the cotton planting model with one film, three drip tapes and six rows increased by 6.15% and 11.0% and 8.1% and 12.3%, in 2017 and 2018, respectively, and WUE increased by 17.4% and 22.7% and 20.9% and 22.8%, in 2017 and 2018 respectively. In conclusion, the cotton planting model with one film, three drip tapes and six rows can be recommended for machine-harvest cotton planting for arid areas in Xinjiang, considering water conservation and improving cotton yield.

Soil moisture responses under different vegetation types to winter rainfall events in a humid karst region.

Soil moisture influences plant growth and hydrological processes. Studying the response characteristics of soil moisture to winter rainfall under different vegetation types in humid karst areas is important for optimizing the restoration patterns in these areas. To this end, we monitored the soil moisture content of arable, grassland, shrub, and forest areas in the karst of Guanling County, Guizhou Province, China, at 10-min intervals. The rainfall threshold for the soil moisture response was the smallest in grassland areas. Under different vegetation types, the soil moisture increase tended to be maximized in light-rainfall events and minimized in medium-rainfall events. Moreover, the increase in soil moisture in the profile under the different vegetation types generally decreased with increasing soil depth during light and rainstorm events, but the opposite variation pattern was observed during moderate-rainfall events. In different rainfall events, the soil moisture recharge and soil moisture decrease were greatest in grassland areas. Among the vegetation types, shrubs maintained the highest mean soil moisture content in winter, with a higher recharge and a smaller decrease in soil moisture. This suggests that shrubs can better maintain their soil moisture content in winter than other vegetation types, which has implications for the selection of regional vegetation restoration patterns.

Estimating catchment scale soil moisture at a high spatial resolution: Integrating remote sensing and machine learning

Soil moisture information is important for a wide range of applications including hydrologic modelling, climatic modelling and agriculture. L-band passive microwave satellite remote sensing is the most feasible option to estimate near-surface soil moisture (~0–5 cm soil depth) over large extents, but its coarse resolution (~10s of km) means that it is unable to capture the variability of soil moisture in detail. Therefore, different downscaling methods have been tested as a solution to meet the demand for high spatial resolution soil moisture. Downscaling algorithms based on the soil thermal inertia relationship between diurnal soil temperature difference (ΔT) and daily mean soil moisture content (μSM) have shown promising results over arid and semi-arid landscapes. However, the linearity of these algorithms is affected by factors such as vegetation, soil texture and meteorology in a complex manner. This study tested a (i) Regression Tree (RT), an Artificial Neural Network (ANN), and a Gaussian Process Regression (GPR) model based on the soil thermal inertia theory over a semi-arid agricultural landscape in Australia, given the ability of machine learning algorithms to capture complex, non-linear relationships between predictors and responses. Downscaled soil moisture from the RT, ANN and GPR models showed root mean square errors (RMSEs) of 0.03, 0.09 and 0.07 cm3/cm3 compared to airborne retrievals and unbiased RMSEs (ubRMSEs) of 0.07, 0.08 and 0.05 cm3/cm3 compared to in-situ observations, respectively. The study showed encouraging results to integrate machine learning techniques in estimating near-surface soil moisture at a high spatial resolution.

Effects of rainwater harvesting system on soil moisture in rain-fed orchards on the Chinese Loess Plateau

Rainwater is a primary water source for the hilly and gully region of the Loess Plateau where an improved efficiency of rainwater utilization is crucial for sustainable agricultural development. A new system, comprised of rainwater harvesting, concentrating infiltration with multi-holed pipe and mulching (RIM), was designed to sustain soil moisture at a proper level in rain-fed orchards in the hilly and gully loess region of China. This study monitored changes in soil moisture and distribution over soil profiles using four treatments: (a) RIM1 with two rainwater harvesting areas, two infiltration pipes and film mulching, (b) RIM2 with one rainwater harvesting area, one infiltration pipe and film mulching, (c) film mulching (FM) only and (d) traditional apple orchard as a control treatment (CK) as a baseline in this experiment. The results showed that mean soil moisture content (SMC) in a range of soil layer between 0 cm and 300 cm for RIM1 and RIM2 treatments increased by 43.01% and 34.78% in 2018 and 30.55% and 26.41% in 2019, respectively. Dividing the soil vertical profile into three layers, i.e., an easy-changing layer (0−60 cm), an increasing or decreasing layer (60−180 cm), and a relatively steady layer (180−300 cm), this study examined the vertical changes of soil moisture. The RIM1 and RIM2 treatments induced a large increase in the size and depth of wetted areas over the whole soil layers. The soil moisture was replenished to a horizontal distance of 1.5 m and 2.5 m apart from the trunk within the soil layer between 60 cm and 300 cm under the RIM1 treatment while only the horizontal distance of 1.5 m apart from the trunk under the RIM2 treatment. While the seasonal variation of SMC in the easy-changing soil layer (0−60 cm) corresponded to precipitation consistently, the SMC in the deep soil layers (60−300 cm) was not sensitive to precipitation. As a result, the treatments of RIM1, RIM2 and FM improved apple yield and crop water productivity compared with those under the control treatment. In particular, the RIM1 treatment performed the best among the treatments investigated in this study. The results highlighted the efficiency of the RIM system in enhancing the soil moisture, which may be useful to improve an orchard production for rain-fed orchards in the loess hilly and gully region of China.

Effects of soil heterogeneity on subsurface water movement in agricultural fields: A numerical study

This study aims to numerically examine the effects of soil heterogeneity on subsurface water movement in agricultural fields under wheat (Triticum aestivum L.) and rice (Oryza sativa L.) crop covers. The 3-D Richards equation that accounts for root water uptake was coupled with a random field generation method to produce realizations of soil hydraulic properties, and the effects of soil heterogeneity were analyzed under realistic atmospheric boundary conditions. Four soil types and three different soil heterogeneity levels were considered to investigate the response of soil heterogeneity on soil water dynamics. It was observed that the effect of soil heterogeneity varies across soil types and its effect was more pronounced in silty clay loam soils. Further, an increase in soil heterogeneity level can increase or decrease the mean soil moisture, hydraulic conductivity, and flow velocity based on land cover, upper boundary condition, and atmospheric demand, and its effect was higher during irrigation periods. A maximum difference of 30% in soil moisture values was observed near the surface soil layers due to an increase in soil heterogeneity on irrigation days. The mean soil moisture content under rice crop cover was always lower than that of wheat crop cover due to higher atmospheric demand in the former. Soil layering effect on soil moisture dynamics, which is related to capillary and hydraulic barrier formation, was found to depend on the layering configuration, available soil moisture, and land cover. The numerical experiments provided useful insights into the complex soil moisture dynamics in agricultural fields.

Response of Soil Moisture to Rainfall Event in Black Locust Plantations at Different Stages of Restoration in Hilly-gully Area of the Loess Plateau, China

Precipitation plays an important role in the water supplies that support ecological restoration by sustaining large-scale artificial plantations in arid and semiarid regions, especially black locust (Robinia pseudoacacia) plantations (RP plantations), which are widely planted due to R. pseudoacacia being an excellent pioneer species. Characterizing the response of soil moisture to rainfall events at different stages of restoration is important for assessing the sustainability of restoration in RP plantations. In this study, we quantified the response of soil moisture to rainfall events at different years of restoration (15, 20 and 30 yr) representing different restoration stages in RP plantations in a typical hilly-gully area, i.e., the Yangjuangou Catchment, of the Loess Plateau, China. Over the growing season (June to September) of 2017, smart probes were placed at nine depths (10, 20, 40, 60, 80, 100, 120, 150, and 180 cm below the soil surface) to obtain volumetric soil water information at 30-min intervals in the three RP plantations. The advance of the wetting front was depicted, and the total cumulative water infiltration was measured. Soil moisture was mainly replenished by eight heavy rainfall events (mean rainfall amount = 46.3 mm), accounting for 88.7% of the rainfall during the growing season. The mean soil moisture content profiles of RP plantations at the three restoration stages were ordered as 30-yr (14.07%) > 20-yr (10.12%) > 15-yr (8.03%), and this relationship displayed temporal stability. Soil moisture was primarily replenished by rainfall at the 0–60 cm soil depth, and soil moisture remained stable below the 100-cm soil depth. The rainfall regime influenced the advancement of the wetting front. Here, a single rainfall event of 30 mm was the rainfall threshold for infiltration into the 60-cm soil layer. The total infiltration time ranged from 310.5–322.0 h, but no significant differences were found among RP plantations at different restoration stages. Young and old RP plantations had more total infiltration (more than 228.2 mm) and deeper infiltration depths (80–100 cm) than middle-aged plantations. The RP plantation at the intermediate restoration stage exhibited minimal total infiltration (174.2 mm) and a shallow infiltration depth (60 cm) due to the soil physical structure of the plot, which may have limited rain infiltration. More stand conditions that may affect infiltration should be considered for priority afforestation areas.

Effect of agri-silvi-horticultural system on soil moisture content at different depths

The present study was conducted at Research Farm, Department of Forestry CCS HAU, Hisar to analyze the effect of agri-silvi-horticultural system (Kinnow +Eucalyptus+ Wheat, Kinnow+ Wheat and sole crop on soil moisture content at0-15, 15-30, 30-60 and 60-90 cm soil depths). Total five irrigations at an interval of one month were applied from sowing to harvesting stage. Soil moisture content was measured gravimetrically before each irrigation. Moisture content was increased significantly with increase in soil depth but it decreased under tree integrated system and maximum decrease was observed under Kinnow + Eucalyptus + wheat system. There was slight difference between first and second irrigation which shows more moisture content relative to succeeding 3 irrigations. During first irrigation, mean soil moisture content was significantly higher under control (12.6%) followed by Kinnow+Wheat (11.7%) and it was lowest under Kinnow+Eucalyptus+Wheat system (10.7%). Similarly at second irrigation, mean soil moisture content was significantly higher under control (11.7%) followed by Kinnow+Wheat (10.7%). Significantly lowest was under Kinnow+Eucalyptus+Wheat system (10.0%) as compared to control. In succeeding three irrigations, mean soil moisture content was statistically at par with each other in all the systems. Based on above study, results showed that there was more uptake of moisture under tree based system which is due to deep and proliferated root system of tree component as compared to sole crop.

The spatial variability of soil water content in a potato field before and after spray irrigation in arid northwestern China

Abstract Assessing the spatial variability of soil water content is important for precision agriculture. To measure the spatial variability of the soil water content and to determine the optimal number of sampling sites for predicting the mean soil water content at different stages of the irrigation cycle, field experiments were carried out in a potato field in northwestern China. The soil water content was measured in 2016 and 2017 at depths of 0–20 and 20–40 cm at 116 georeferenced locations. The average coefficient of variation of the soil water content was 20.79% before irrigation and was 16.44% after irrigation at a depth of 0–20 cm. The spatial structure of the soil water content at a depth of 20–40 cm was similar throughout the irrigation cycle, but at a depth of 0–20 cm a relatively greater portion of the variation in the soil water content was spatially structured before irrigation than after irrigation. The autocorrelation of soil water contents was influenced by irrigation only in the surface soil layer. To accurately predict mean soil moisture content, 40 and 20 random sampling sites should be chosen with errors of 5% and 10%, respectively.

Responses of soil carbon decomposition to drying-rewetting cycles: A meta-analysis

Drying-rewetting cycles (DWC) is an important climate change factor in this century. The rewetting of dry soil stimulates carbon dioxide emission into the atmosphere, which is called the Birch effect. Although a large number of studies have been conducted to quantify the effect of DWC on cumulative soil respiration (CSR), their results are often contradictory, which offers us an opportunity to explore potential influencing factors and variability among studies. Using a meta-analysis including 524 observations from studies across different ecosystems and soil types, we investigated the responses of CSR to DWC. Our results indicated that DWC led to 72% stimulation of CSR compared with lower constant-moisture control (LC), 25% inhibition compared with upper constant-moisture control (UC), but minimal difference with mean constant-moisture control (MC), respectively. The meta-regression analysis showed that the DWC effect on CSR depended on mean annual precipitation, soil properties (clay content, C/N ratio, TN, pH), and the duration of drying in the DWC treatment. In addition, the effect size of CSR relative to UC was positively correlated with the number of DWC, suggesting that the slower-cycling soil carbon may be more vulnerable to DWC than the faster-cycling soil carbon and the “physical mechanism” may play a role in substrate release and CO2 emission after multiple DWC. Overall, our study provided a comprehensive analysis of the effects of DWC on CSR and showed that frequent drying-rewetting cycles induced by climate change might stimulate the loss of soil carbon to the atmosphere. Moreover, the similar CSR between DWC and MC (which have the same mean soil moisture content) suggests that the CO2 pulse after rewetting may be compensated by the low CO2 emission during the drying phase. Further research is needed to explore the responses of SOC pools with different turnover times to DWC and to investigate the DWC effects on soil respiration by in situ experiments and long-term studies.