Influence Soil Water Research Articles

No effect of pyrolysis temperature and feedstock type on hydraulic properties of biochar and amended sandy soil

Biochar has been lauded as a cure-all for improving water availability in soils. Yet the effect of pyrolysis temperature and feedstock type on biochar hydraulic properties and its subsequent effects on soils are not well known. We therefore systematically studied water retention, saturated hydraulic conductivity (Ksat) and hydrophobicity of 12 standard biochars (six feedstocks and two pyrolysis temperatures) developed by the UK Biochar Research Centre. The hydraulic properties were determined for pure crushed biochar, as well as for a sandy soil amended with 10 t ha−1 biochar (assessed three times over a period of 15 months). For pure biochar, the effect of feedstock-temperature treatments on the water retention curve was negligible. Rice husk at a pyrolysis temperature of 700 °C had a significantly lower saturated water content, plant available water content and Ksat than all other biochar treatments. This can be attributed to its severe hydrophobicity: while all other treatments were non-hydrophobic and rice husk at 550 °C and Miscanthus straw at 550 °C were both strongly hydrophobic, rice husk at 700 °C was severely hydrophobic. Incorporation of the biochar into a sandy soil did not significantly influence soil water retention, saturated hydraulic conductivity and hydrophobicity. There were also no significant differences between the biochar treatments. These results indicate that except for rice husk at 700 °C the different biochar feedstock types and pyrolysis temperatures yield surprisingly similar material in terms of hydraulic characteristics. Improved soil hydrology should not be a main reason to apply biochar on sandy soils, but if biochar is applied differences in hydrophobicity should be considered.

Soil water dynamics under Moistube irrigation

The design and management of irrigation systems require knowledge of soil water movement. There are few studies on soil water dynamics of Moistube irrigation (MTI) since it is a relatively new type of subsurface irrigation technology. It was hypothesised that soil texture influences soil water distribution under MTI. We determined soil water distribution, experimentally and numerically, using HYDRUS 2D/3D model for two soil textures (loamy sand and sandy clay loam). The experiment consisted of a soil box filled with soil and Moistube, supplied with water under a constant pressure head of 60 kPa, placed at 20 cm below the soil surface. Soil water content (SWC) was measured using Decagon MPS-2 sensors installed at depths of 5 cm, 10 cm, 15 cm, 20 cm, 30 cm, 40 cm and 50 cm and laterally at 10 cm, 20 cm and 30 cm over a period of 72 h. Results showed that simulated SWC closely matched (R2 ≥ 0.70 and RMSE ≤ 0.045 cm3 cm−3) observed values for all depths considered for the two soil textures. The model slightly under- or over-estimated SWC (<15.6%). There was no significant difference (p > 0.05) between the soil water distribution in lateral and downward direction for both sandy clay loam soil and loamy sand. However, the SWC upward of the Moistube placement depth was significantly (p < 0.05) lower than both lateral and downward. SWC in loamy sand at 10 cm upward, downward and lateral after 24 h were 0.08 cm3 cm−3, 0.23 cm3 cm−3 and 0.20 cm3 cm−3, respectively. The corresponding values for sandy clay loam were 0.28 cm3 cm−3, 0.32 cm3 cm−3 and 0.31 cm3 cm−3 at 10 cm upward, downward and lateral, respectively. The simulations for wetted distance in both soil textures were also close to the observed values (R2 ≥ 0.97, RMSE ≤ 3.99 cm). Soil texture had a significant (p < 0.05) effect on soil water movement with upward movement faster in sandy clay loam than in loamy sand. The lateral and downward distances were 23 cm and 24.6 cm, respectively, for loamy sand after 24 h. Similarly, for sandy clay loam, the lateral and downward distance was 19 cm. These wetting distances should be considered in the design of MTI in terms of depth of placement and lateral spacing. The results of this study demonstrated the usefulness of HYDRUS-2D/3D model in the prediction of soil water movement for optimum design of MTI.

Agroforestry, grass, biofuel crop, and row‐crop management effects on soil water dynamics for claypan landscapes

AbstractSoil water use and water storage vary by vegetative management practices, and these practices affect land productivity and hydrologic processes. This study investigated the effects of agroforestry buffers (AB), grass buffers (GB), and biofuel crops (BC), relative to row crops (RC) on soil water use for a claypan soil in northern Missouri, USA. The experiment located at the Greenley Memorial Research Center included RC, AB, GB, and BC established in 1991, 1997, 1997, and 2012, respectively. Soil water reflectometer sensors installed at 5‐, 10‐, 20‐, and 40‐cm depths monitored soil water from April to November in 2017 and 2018. Results showed significant differences in weekly volumetric water content (VWC) among treatments for all four soil depths in 2017 and 2018. Treatments of AB, GB, and BC had lower VWC (16, 37, and 18% on 9 June), (31, 35, and 20% on 18 August), and (43, 49, and 35% on 29 September) in 2017 and (46, 70, and 19% on 24 August) and (31, 34, and 17% on 5 October) in 2018, respectively, in the pre‐recharge periods for the 5‐cm depth compared with the RC. In the post‐recharge period, equal or occasionally slightly higher soil water occurred in the buffer and biofuel treatments compared to the RC. During recharge, larger increases in soil water due to better infiltration were observed in the perennial vegetative practices relative to RC. The results showed that these practices could significantly influence soil water use and storage compared to RC management, especially for eroded claypan landscapes.

Water infiltration under different CaCl2 concentrations for soil with mainly permanent charges

It is well known that, electrolyte concentration can influence soil water movement through its influence on the osmotic potential of water; on the other hand, electrolytes also can influence soil water movement through its influence on the matric potential of soil water, because soil electric field is closely related to the electrolyte concentration. Therefore, the two effects arising from electrolytes on soil water movement are coupled, and the object of this study is to explore this coupling effect by adopting a 2:1 type electrolyte with different concentrations. In this study, water movement in a purple soil was evaluated through a one-dimensional vertical infiltration experiment through determining water infiltration rate and advance speed of the wetting front. The results revealed that (1) the critical electrolyte concentration of CaCl2 in soil water infiltration and migration is 10−2 mol L-1; (2) 10−2 mol L-1 CaCl2 is also the critical concentration for the relative total water potential, which is the sum of the matric potential and the osmotic potential; (3) detailed analysis of the effects of the matric potential and osmotic potential on soil water movement indicated that soil water infiltration is dominated by the matric potential when the CaCl2 concentration is lower than the critical concentration, while it is dominated by the osmotic potential when the CaCl2 concentration is higher than the critical concentration. It can be speculated that the matric potential based on an electric field dominates soil water infiltration when the soil moisture content is high, while osmotic potential dominates soil water infiltration when soil moisture content is low and that the concentration of 0.01 mol L-1 CaCl2 is the critical point at which water infiltration changes from matric potential control to osmotic potential control.

Yield and quality of sunflower oil in Ultisol and Oxisol under water regimes

ABSTRACT Extreme natural events influencing soil water availability are major factors limiting yield and oil quality in oilseed crops. The aim of the present study was to assess the effect of water deficit and surplus water on yield, oil content and on the fatty acid profile of sunflower plants sown in main and second crop seasons in two soil classes in Rio Grande do Sul State. The experiment was carried out in Santa Maria, RS (Ultisol) and Panambi, RS state, Brazil (Oxisol), Brazil, and comprised three water conditions (water deficit, water surplus and control) in a randomized block design. The hybrid Helio 250 was sown in early September (main crop season) and in early January (second crop season) in both soil classes. Yield, yield components, oil content, oil yield and fatty acid profile were herein analyzed. Yield and yield components were affected by water conditions, sowing dates and soil class. The soil class had no significant effect on oil content, yield or quality. Water deficit was more harmful to oil yield and quality than water surplus. Water deficit was responsible for increased oleic fatty acid contents and for linoleic content reduction.

Tree species and size influence soil water partitioning in coffee agroforestry

Complementary use of resources is considered a strong driver of enhanced performance in mixed-species assemblages. In income-producing agroforestry systems, economically valuable species will ideally benefit from resource partitioning. In agroforests in southern India, we assessed soil water uptake depths of coffee and different shade tree species at the end of the dry season, when water availability is regarded critical. Water isotopes ratios (δD and δ18O) from soil and plant samples were analyzed and an isotope mixing model was applied. Results suggest that coffee plants drew water mainly from the top soil (56% from 0 to 20 cm), and to a lower extent from the subsoil. Jackfruit trees had very similar uptake patterns, which suggest competition. Mango trees showed reverse patterns of water uptake with soil depth, i.e. drew more than 75% from the subsoil, which suggests spatial complementarity to coffee. Within and across shade tree species, soil water uptake from the top soil increased with increasing diameter. We suggest that shade tree species choice and diameter regulation are viable options in management for soil water use complementarity.

Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis

AimsRhizodeposits collected from hydroponic solutions with roots of maize and barley, and seed mucilage washed from chia, were added to soil to measure their impact on water retention and hysteresis in a sandy loam soil at a range of concentrations. We test the hypothesis that the effect of plant exudates and mucilages on hydraulic properties of soils depends on their physicochemical characteristics and origin.MethodsSurface tension and viscosity of the exudate solutions were measured using the Du Noüy ring method and a cone-plate rheometer, respectively. The contact angle of water on exudate treated soil was measured with the sessile drop method. Water retention and hysteresis were measured by equilibrating soil samples, treated with exudates and mucilages at 0.46 and 4.6 mg g−1 concentration, on dialysis tubing filled with polyethylene glycol (PEG) solution of known osmotic potential.ResultsSurface tension decreased and viscosity increased with increasing concentration of the exudates and mucilage in solutions. Change in surface tension and viscosity was greatest for chia seed exudate and least for barley root exudate. Contact angle increased with increasing maize root and chia seed exudate concentration in soil, but not barley root. Chia seed mucilage and maize root rhizodeposits enhanced soil water retention and increased hysteresis index, whereas barley root rhizodeposits decreased soil water retention and the hysteresis effect. The impact of exudates and mucilages on soil water retention almost ceased when approaching wilting point at −1500 kPa matric potential.ConclusionsBarley rhizodeposits behaved as surfactants, drying the rhizosphere at smaller suctions. Chia seed mucilage and maize root rhizodeposits behaved as hydrogels that hold more water in the rhizosphere, but with slower rewetting and greater hysteresis.

Variation in soil hydrological properties on shady and sunny slopes in the permafrost region, Qinghai–Tibetan Plateau

Soil hydrological properties not only directly influenced soil water content, evapotranspiration, infiltration, and runoff, but also made these factors of concern in arid and semi-arid regions. Prior research has focused on the temporal and spatial variation in soil hydrological properties and the impacts of climate change, ecosystem changes over time or human activities on soil hydrological properties. However, studies conducted on the differences in soil hydrological properties between shady and sunny slopes have seldom been conducted, especially in the permafrost region of the Qinghai–Tibetan Plateau. To investigate the variation in soil hydrological properties on shady and sunny slopes, we chose the Zuomaokongqu watershed of Fenghuo Mountain, which is located on the Qinghai–Tibetan Plateau, as the study area. Three experimental sites were selected in the study area, and the distance between experimental sites was 100 m. Based on the differences in altitude and vegetation coverage, five sunny slope sample points and three shady slope sample points were selected in each experimental site. At each of these sample points, the soil water content, soil-saturated conductivity, soil water-retention curve, soil physico-chemical properties, aboveground biomass, and underground biomass were examined in the top 0–50 cm of the active layer. The results showed that the soil hydrological properties of shady slopes differed significantly from those of sunny slopes. The soil water content of sunny slopes was 20.9% less than that of shady slopes. The soil-saturated water content of sunny slopes was 12.2% less than that of shady slopes. The soil water content of sunny slopes at − 0.3 Mpa and − 0.7 Mpa matric potential was 23.5% and 21.4% less than that of shady slopes, respectively. It was indicated that the soil water-retention capacity of sunny slopes was lower than that of shady slopes. However, the soil-saturated conductivity of sunny slopes was 84.5% larger than that of shady slopes and exceeded the range of soil-saturated conductivity, which was useful for plant growth. Meanwhile, the vegetation coverage on sunny slopes was lower than that on shady slopes, but the soil sand content showed the opposite relationship. Pearson’s coefficient analysis results showed that vegetation coverage and soil desertification, which are affected by permafrost degradation, were the main factors influencing soil hydrological properties on shady and sunny slopes. These results will help determine appropriate hydraulic parameters for hydrological models in mountain areas.

Subsoiling and Sowing Time Influence Soil Water Content, Nitrogen Translocation and Yield of Dryland Winter Wheat

Dryland winter wheat in the Loess Plateau is facing a yield reduction due to a shortage of soil moisture and delayed sowing time. The field experiment was conducted at Loess Plateau in Shanxi, China from 2012 to 2015, to study the effect of subsoiling and conventional tillage and different sowing dates on the soil water storage, Nitrogen (N) accumulation, and remobilization and yield of winter wheat. The results showed that subsoiling significantly improved the soil water storage (0–300 cm soil depth) and increased the contribution of N translocation to grain N and grain yield (17–36%). Delaying sowing time had reduced the soil water storage at sowing and winter accumulated growing degree days by about 180 °C. The contribution of N translocation to grain yield was maximum in glume + spike followed by in leaves and minimum by stem + sheath. Moreover, there was a positive relationship between the N accumulation and translocation and the soil moisture in the 20–300 cm range. Subsoiling during the fallow period and the medium sowing date was beneficial for improving the soil water storage and increased the N translocation to grain, thereby increasing the yield of wheat, especially in a dry year.

Plastic Mulch and Plant Density Influencing Soil Water Content and Yield of Rainfed Maize in North‐Eastern China

AbstractPlastic mulch, in combination with high plant density, is a common practice for rainfed maize production in north‐eastern China. However, the influence of these practices on soil water storage, maize yield and maize water productivity in different precipitation years is not well understood. In this paper, a 3‐year split‐plot field experiment was designed to compare non‐mulching and plastic film mulching in maize at 67 500 and 82 500 plants per ha in 2013, 2014 and 2015, and also 97 500 plants per ha in 2014 and 2015. Results revealed an increasing trend of precipitation in the study area from 1962 to 2015 and that the number of dry years and extreme years (including extreme dry and wet years) was increasing. In the moderately wet year 2013 and the moderately dry year 2015, the combination of 82 500 plants per ha and plastic film mulching produced the highest yield and water productivity (8.2 t ha−1, 1.7 kg m−3 and 8.3 t ha−1, 2.3 kg m−3, respectively) for maize, while in the extremely dry year 2014 the highest yield (5.6 t ha−1) occurred with 97 500 plants per ha and non‐mulching. This research might be helpful for smallholder farmers needing optimal agricultural strategies to improve maize production in rainfed areas of north‐east China. © 2018 John Wiley &amp; Sons, Ltd.

Soil water response to precipitation in different micro-topographies on the semi-arid Loess Plateau, China

Soil water is an important factor restricting afforestation on the semi-arid Loess Plateau. The micro-topography of the loess slope has changed the distribution pattern of soil water on the slope. To improve water utilization efficiency and optimize afforestation configuration patterns, the relationship between soil water and precipitation at micro-topographic scale must be studied. We used time series analysis to study the temporal variation of soil water and its response to precipitation in four kinds of micro-topographies and undisturbed slope on loess slopes. Micro-topographies significantly influenced soil water distribution and dynamics on the slopes. Soil water stored in the platform, sinkhole, and ephemeral gully influenced subsequent soil water for 4 weeks, whereas soil water stored in the scarp and undisturbed slope could influence soil water for 2 weeks. It took 12 weeks, 10 weeks, 18 weeks, 6 weeks, and 12 weeks for precipitation to reach the deeper soil layer in the platform, sinkhole, scarp, ephemeral gully, and undisturbed slope, respectively. These soil water characteristics in different micro-topographies are vital factors that should be taken into consideration when undertaking afforestation on the Loess Plateau.

Organic Amendments Influence Soil Water Depletion, Root Distribution, and Water Productivity of Summer Maize in the Guanzhong Plain of Northwest China

Organic amendments improve general soil conditions and stabilize crop production, but their effects on the soil hydrothermal regime, root distribution, and their contributions to water productivity (WP) of maize have not been fully studied. A two-year field experiment was conducted to investigate the impacts of organic amendments on soil temperature, water storage depletion (SWSD), root distribution, grain yield, and the WP of summer maize (Zea mays L.) in the Guanzhong Plain of Northwest China. The control treatment (CO) applied mineral fertilizer without amendments, and the three amended treatments applied mineral fertilizer with 20 Mg ha−1 of wheat straw (MWS), farmyard manure (MFM), and bioorganic fertilizer (MBF), respectively. Organic amendments decreased SWSD compared to CO, and the lowest value was obtained in MBF, followed by MWS and MFM. Meanwhile, the lowest mean topsoil (0–10 cm) temperature was registered in MWS. Compared to CO, organic amendments generally improved the root length density (RLD) and root weight density (RWD) of maize. MBF showed the highest RLD across the whole soil profile, while MWS yielded the greatest RWD to 20 cm soil depth. Consequently, organic amendments increased grain yield by 9.9–40.3% and WP by 8.6–47.1% compared to CO, and the best performance was attained in MWS and MBF. We suggest that MWS and MBF can benefit the maize agriculture in semi-arid regions for higher yield, and WP through regulating soil hydrothermal conditions and improving root growth.

Seasonal Wetness, Soil Organic Carbon, and Fire Influence Soil Hydrological Properties and Water Repellency in a Sagebrush‐Steppe Ecosystem

AbstractPrescribed fire is an important tool for rangeland management in sage‐steppe ecosystems, yet the long‐term effects of this practice on soil hydraulic properties are not well known. We explore interactions among site geomorphology, soil organic carbon (SOC) soil N, soil water repellency (SWR), and plant community type on infiltration properties before fire and 8 years thereafter in a semiarid research watershed. The objective was to assess the sustainability of rangeland burning in sage‐steppe ecosystems. Many types of measurements were made in three plant communities to identify how differences in soil hydraulic properties are related to differences in plant cover and soil texture and to determine relationships among SOC, SWR, soil water contact angle, and infiltration properties. Measurements were made on transects in burned and unburned catchments. We found that severity and occurrence of surface SWR were substantially reduced 8 years after a fire within the area originally covered with mountain big sagebrush, where the fire intensity was greatest. Surface SWR was lowest in the sparsely vegetated low sagebrush, where SOC was also lowest. Unsaturated hydraulic conductivity (Kh) increased in each vegetation type over the 8‐year period after burning and was not directly related to SWR. Spatial variability in Kh was primarily controlled by soil texture, whereas differences in sorptivity (S) were controlled by SWR and aridity. SOC is not well correlated to soil surface SWR. The decadal scale changes in Kh and associations between S and site characteristics indicate forms of resilience to fire across a moisture gradient.

Plant species richness and functional groups have different effects on soil water content in a decade‐long grassland experiment

Abstract The temporal and spatial dynamics of soil water are closely interlinked with terrestrial ecosystems functioning. The interaction between plant community properties such as species composition and richness and soil water mirrors fundamental ecological processes determining above‐ground–below‐ground feedbacks. Plant–water relations and water stress have attracted considerable attention in biodiversity experiments. Yet, although soil scientific research suggests an influence of ecosystem productivity on soil hydraulic properties, temporal changes of the soil water content and soil hydraulic properties remain largely understudied in biodiversity experiments. Thus, insights on how plant diversity—productivity relationships affect soil water are lacking. Here, we determine which factors related to plant community composition (species and functional group richness, presence of plant functional groups) and soil (organic carbon concentration) affect soil water in a long‐term grassland biodiversity experiment (The Jena Experiment). Both plant species richness and the presence of particular functional groups affected soil water content, while functional group richness played no role. The effect of species richness changed from positive to negative and expanded to deeper soil with time. Shortly after establishment, increased topsoil water content was related to higher leaf area index in species‐rich plots, which enhanced shading. In later years, higher species richness increased topsoil organic carbon, likely improving soil aggregation. Improved aggregation, in turn, dried topsoils in species‐rich plots due to faster drainage of rainwater. Functional groups affected soil water distribution, likely due to plant traits affecting root water uptake depths, shading, or water‐use efficiency. For instance, topsoils in plots containing grasses were generally drier, while plots with legumes were moister. Synthesis. Our decade‐long experiment reveals that the maturation of grasslands changes the effects of plant richness from influencing soil water content through shading effects to altering soil physical characteristics in addition to modification of water uptake depth. Functional groups affected the soil water distribution by characteristic shifts of root water uptake depth, but did not enhance exploitation of the overall soil water storage. Our results reconcile previous seemingly contradictory results on the relation between grassland species diversity and soil moisture and highlight the role of vegetation composition for soil processes.

Effects of Short-term Exogenous Nitrogen and Carbon Input on Soil Respiration Under Changing Precipitation Pattern

The responses of soil respiration to exogenous carbon (C) and nitrogen (N) inputs under changing precipitation patterns were explored via in-situ field experiments. In 2014, a typical temperate grassland on the Xilin River of Inner Mongolia was taken as the research site, and soil respiration was measured in the following treatments:addition of water alone (CK), addition of water + N fertilizer[CN, 2.5 g·(m2·a)-1], addition of water + labile C[CG, 24 g·(m2·a)-1], and addition of water + N fertilizer+ labile C[CNG, 2.5 g·(m2·a)-1+24 g·(m2·a) -1], and the correlations of soil respiration with soil temperature, soil moisture, soil dissolved organic C (DOC), and soil microbial biomass C (MBC) were analyzed. During the first water application event (FWE) with the frequency of natural precipitation, cumulative CO2 efflux over 168 hours significantly increased in the CG and CNG treatments, whereas there was no such change in the CN treatment. In addition, soil MBC contents in the CG and CNG treatments were significantly higher than that in the CK and CN treatments, and the correlation of average soil respiration rate with soil MBC content among these treatments was positively significant (P<0.05). In contrast with during the FWE, cumulative CO2 efflux over 168 hours and soil MBC content significantly decreased during the second water application event (SWE) with no natural precipitation (P<0.05), whereas soil DOC content significantly increased (P<0.05). The cumulative CO2 efflux over 168 hours significantly decreases in the CN and CG treatments (P<0.05).During both the water application events, soil respiration rate had a positive relationship with soil temperature and soil volume water content (P<0.05). Therefore, it is proposed that the distribution of natural precipitation influences soil water content, which controls the effects of exogenous C and N on soil respiration in semiarid grassland ecosystems.

Warming and Elevated CO2 Interact to Alter Seasonality and Reduce Variability of Soil Water in a Semiarid Grassland

Global changes that alter soil water availability may have profound effects on semiarid ecosystems. Although both elevated CO2 (eCO2) and warming can alter water availability, often in opposite ways, few studies have measured their combined influence on the amount, timing, and temporal variability of soil water. Here, we ask how free air CO2 enrichment (to 600 ppmv) and infrared warming (+ 1.5 °C day, + 3 °C night) effects on soil water vary within years and across wet-dry periods in North American mixed-grass prairie. We found that eCO2 and warming interacted to influence soil water and that those interactions varied by season. In the spring, negative effects of warming on soil water largely offset positive effects of eCO2. As the growing season progressed, however, warming reduced soil water primarily (summer) or only (autumn) in plots treated with eCO2. These interactions constrained the combined effect of eCO2 and warming on soil water, which ranged from neutral in spring to positive in autumn. Within seasons, eCO2 increased soil water under drier conditions, and warming decreased soil water under wetter conditions. By increasing soil water under dry conditions, eCO2 also reduced temporal variability in soil water. These temporal patterns explain previously observed plant responses, including reduced leaf area with warming in summer, and delayed senescence with eCO2 plus warming in autumn. They also suggest that eCO2 and warming may favor plant species that grow in autumn, including winter annuals and C3 graminoids, and species able to remain active under the dry conditions moderated by eCO2.

Cover crops mitigate direct greenhouse gases balance but reduce drainage under climate change scenarios in temperate climate with dry summers.

Cover crops provide ecosystem services such as storing atmospheric carbon in soils after incorporation of their residues. Cover crops also influence soil water balance, which can be an issue in temperate climates with dry summers as for example in southern France and Europe. As a consequence, it is necessary to understand cover crops' long-term influence on greenhouse gases (GHG) and water balances to assess their potential to mitigate climate change in arable cropping systems. We used the previously calibrated and validated soil-crop model STICS to simulate scenarios of cover crop introduction to assess their influence on rainfed and irrigated cropping systems and crop rotations distributed among five contrasted sites in southern France from 2007 to 2052. Our results showed that cover crops can improve mean direct GHG balance by 315kgCO2 eha-1 year-1 in the long term compared to that of bare soil. This was due mainly to an increase in carbon storage in the soil despite a slight increase in N2 O emissions which can be compensated by adapting fertilization. Cover crops also influence the water balance by reducing mean annual drainage by 20mm/year but increasing mean annual evapotranspiration by 20mm/year compared to those of bare soil. Using cover crops to improve the GHG balance may help to mitigate climate change by decreasing CO2 e emitted in cropping systems which can represent a decrease from 4.5% to 9% of annual GHG emissions of the French agriculture and forestry sector. However, if not well managed, they also could create water management issues in watersheds with shallow groundwater. Relationships between cover crop biomass and its influence on several variables such as drainage, carbon sequestration, and GHG emissions could be used to extend our results to other conditions to assess the cover crops' influence in a wider range of areas.

Biochar Dosage and Granulometry Influencing Soil Density and Water Retention

Biochar Dosage and Granulometry Influencing Soil Density and Water Retention

Water Movement and Finger Flow Characterization in Homogeneous Water‐Repellent Soils

Core Ideas The cumulative infiltration decreased with increasing soil water repellency. Soil water movement in higher water‐repellent levels tended to be more unstable. Finger flow occurred preferentially in the coarser, more water‐repellent soils. Strong correlations of cumulative infiltration and cumulative wetting area were shown. Soil water repellency (SWR) is a widespread property in soils around the world. It influences soil water movement and causes unstable flow. The mechanics of finger flow occurrence in water‐repellent soils are not clearly understood. Slab chamber infiltration experiments consisting of increasing SWR persistence in clay and sandy loam soils were conducted to compare wetting front advancement and mechanics of finger flow development. The temporal variation curves of cumulative infiltration (CI) decreased with an increase in SWR persistence. For wettable soils, the wetting front advanced regularly with time, but for water‐repellent soils, it became unstable and finger flow occurred as the SWR persistence increased. Water movement in soils with higher SWR persistence tended to be more unstable. Water repellency contributed to finger flow development, especially for sandy loam. There were strong correlations among CI, finger length, and the cumulative wetting area. In the strongly, severely, and extremely water‐repellent sandy loam soils, the power function relationship fit better than the linear function. The average soil water content decreased with a higher SWR persistence, which meant that less water was available in the profile. Finger flow development was related to the more severe water‐repellent conditions and tended to be more easily formed in the water‐repellent sandy loam soils than the clay loam soils due to the faster infiltration rate.

Black Film Mulching and Plant Density Influencing Soil Water Temperature Conditions and Maize Root Growth

Core Ideas Transparent film mulching increased the soil water storage more than black film mulching. The mulching treatment only markedly increased the soil temperature in the maize seeding growth stage. Higher plant density decreased the root surface area, root volume, root length, and root diameter. Plastic mulch in combination with high plant density is a common agronomic technique in rainfed maize (Zea mays L.) production. However, the effects of combining colored film mulching and plant density on soil temperature, soil water storage, the maize roots, and yield have not been thoroughly elucidated to date. Thus, a field experiment to explore the effects of colored film mulching and plant density on soil temperature and water, maize roots, and yield was conducted on main plots with three types of mulching (non‐mulching, transparent film mulching, and black plastic film mulching), which were divided into three subplots with three plant densities (60,000, 75,000, and 90,000 plants ha−1). The results were as follows: The mulching increased the soil water storage during the entire period of maize growth, and transparent film mulching increased soil water storage more than black film mulching. The mulching only markedly increased soil temperature in the maize seeding and jointing stages compared with the non‐mulching treatment, but the plant density augmented the soil temperature after the seeding stage. Compared with the non‐mulching treatment, the mulching treatments significantly increased root length, root length density, and root diameter by 17.0, 21.4, and 11.6%, respectively, during the heading stage and by 65.2, 70, and 11.6%, respectively, during the mature stage. As plant density increased, root surface area, root volume, root length, and root diameter decreased. The best combination, which attained higher yield and profit than other treatments, was the combination of a plant density of 90,000 plants ha−1 and black film mulching.