Differences In Soil Texture Research Articles

Modeling Experiments for Evaluating the Effects of Trees, Increasing Temperature, and Soil Texture on Carbon Stocks in Agroforestry Systems in Kerala, India

Research Highlights: Agroforestry systems in the humid tropics have the potential for high rates of production and large accumulations of carbon in plant biomass and soils and, thus, may play an important role in the global C cycle. Multiple factors can influence C sequestration, making it difficult to discern the effect of a single factor. We used a modeling approach to evaluate the relative effects of individual factors on C stocks in three agricultural systems in Kerala, India. Background and Objectives: Factors such as plant growth form, management, climate warming, and soil texture can drive differences in C storage among cropping systems, but the relationships among these factors and their effects are complex. Our objective was to use CENTURY, a process-based model of plant–soil nutrient cycling, in an experimental mode to evaluate the effects of individual factors on C stocks in soil and biomass in monocultures (annuals or trees) and agroforestry systems. Materials and Methods: We parameterized the model for this region, then conducted simulations to investigate the effects on C stocks of four experimental scenarios: (1) change in growth form; (2) change in tree species; (3) increase in temperature above 20-year means; and (4) differences in soil texture. We compared the models with measured changes in soil C after eight years. Results: Simulated soil C stocks were influenced by all factors: growth form; lignin in tree tissues; increasing temperature; and soil texture. However, increasing temperature and soil sand content had relatively small effects on biomass C. Conclusions: Inclusion of trees with traits that promoted C sequestration such as lignin content, along with the use of best management practices, resulted in the greatest C storage among the simulated agricultural systems. Greater use and better management of trees with high C-storage potential can thus provide a low-cost means for mitigation of climate warming.

Effects of nickel fertilization on soybean growth in tropical soils

ABSTRACT Although nickel (Ni) is recognized as plant nutrient since the turn of the 21st century, uncertainty remains about its optimum application rates and forms. This paper focuses on Ni application in soils, relating to its effect as a plant micronutrient. Specifically, the effect of Ni on the activity of urease in soybean plants is examined. The effects of applying four Ni rates in two different soil types were tested. A full factorial 2 × 4 blocked design experiment was established under controlled conditions. Ni rates (0, 0.25, 0.5 and1.0 mg of Ni·kg–1 of soil) were applied in two soils with contrasting clay contents. The addition of Ni increased the urease activity in soybean plants but was affected by soil textural differences. The highest urease activity was achieved by the application of 1.0 mg·kg–1 Ni in the sandy soil. The absorption of Ni by the plants and its availability was found to be soil texture dependent. The rate of 0.25 mg·kg–1 Ni increased the soybean dry matter production by 25% in the sandy soil. In conclusion, Ni was effective in promoting plant growth and biomass accumulation although depending on soil clay proportion. For soybean, there was no correlation between urease activity and biomass accumulation. The results of this study indicate a clear Ni effect in different type of soils in Sao Paulo state, serving as a solid initial doses indicator for soybean fertilization programs and future studies on nickel in Soybean.

Sediment transport capacity in erodible beds with reconstituted soils of different textures

Precise estimation of sediment transport capacity and wide applicability of a prediction equation could provide a positive response to increasing challenges of soil erosion. Currently, the models developed by many researchers are focused on a few or single soils. In this study, a prediction equation of sediment transport capacity was attempted to establish from the flume experiments performed on erodible beds under the experimental settings of two slopes (5.6%, 16.7%), four unit width discharges (6.67 × 10−5, 1.33 × 10−4, 2.00 × 10−4 and 2.67 × 10−4 m2 s−1) and five reconstituted soils (sand contents of 0%, 30%, 50%, 70%, 100%). Here, the sediment transport capacity under clay-sand mixture of different soil texture were analyzed, and a prediction equation for sediment transport based on soil cohesion and hydraulic variables was established. The experiments confirmed that the sediment concentration and transport capacity increased with the unit width discharge and slope gradient as a power function, and was more dependent on slope gradient. Besides, the hydrological and erosive processes on the beds with reconstituted soils varied with soil texture, the beds with a high clay content had a stable channel of sediment transport. Comparatively, unit stream power was the most suitable hydraulic variable to describe the sediment transport capacity (r = 0.951, P < 0.01). The introduction of soil cohesion of bed materials further improved the reliability of the prediction equation by combining the soil cohesion and unit stream power as a composite predictor (R2 = 0.940, NSE = 0.943, P < 0.01). The new equation could provide dependable prediction for various erodible beds with packed soils of different textures. Soil cohesion could be considered as an indicator of soil properties in prediction equation of sediment transport capacity. Given the broad range of physical properties of reconstituted soils of different textures, the results are applicable to a wide variety of soil types.

Lodgepole pine tree-ring growth, Δ13C and the inverse texture effect across a soil chronosequence in glacial till

Our goal was to better understand tree growth and photosynthetic responses to variations in plant available water and elucidate the role of the inverse texture effect in snow dominated montane forests. We measured tree ring carbon isotope composition and annual growth over a 31-year record for lodgepole pine (Pinus contorta Douglas ex Loudon) growing on three different-aged glacial till surfaces in Wyoming, USA. Soils of different ages developed on till surfaces from three separate glaciation events were significantly different in clay content and distribution with depth; maximum clay content at depth ranged from 19 to 20% on the two youngest till surfaces, but was as high as 36% on the oldest till surface. Ring growth was lowest at the youngest till sites, and only on these coarse-textured soils was growth positively correlated with annual maximum snow water equivalent (SWEmax). Δ13C was highest for trees at these young till sites, suggesting that hydraulic conductivity and stomatal conductance is comparatively high during growth periods on these coarse-textured soils. Taken together, we found that age of glacial till and related soil texture differences strongly influenced tree-ring growth and Δ13C response of lodgepole pine to interannual variation in precipitation and drought severity, but responses did not support an inverse texture effect in these semi-arid forest systems.

Seedling Emergence Patterns of Six Restoration Species in Soils from Two Big Sagebrush Plant Communities

Despite the critical need to improve degraded herbaceous understory conditions in many semiarid ecosystems, the influence of soil properties on seedling emergence of species seeded in shrubland plant communities is largely unexplored. We evaluated emergence patterns of 6 restoration species in soils from wyomingensis (i.e., Wyoming big sagebrush, Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) and vaseyana (i.e., mountain big sagebrush, A. t. ssp. vaseyana [Rydb.] Beetle) plant communities that differed in soil texture, soil organic matter content, and soil water-holding capacity. We conducted 2 separate experiments that regularly wetted soils to standardized soil water potentials (i.e., field capacity; −0.03 MPa) and allowed differences in evaporation to create distinct wet-dry watering pattern cycles over a 26–29 d period. Our objectives were to compare soil attributes of wyomingensis and vaseyana soils, evaluate whether emergence patterns of restoration species vary within these soils, and determine how these patterns are altered by soil water-content levels. We found differences in soil texture and organic matter between soils and thus soil water-holding capacity: finer-textured vaseyana soils held roughly twofold more water than coarse-textured wyomingensis soils. Seeds in vaseyana soils were exposed to fewer wet-dry cycles compared to wyomingensis soils because of the greater capacity of vaseyana soils to retain water. Restoration species also collectively exhibited greater emergence in vaseyana soils than in wyomingensis soils, yet emergence patterns were vastly different among species, and differences between soils became more pronounced under low soil water for only 2 species. We conclude that the manner in which soils and water uniquely influenced emergence patterns provides new insights into species suitability for restoration sites and how inherent soil differences may constrain seeding success.

Heterogeneidade ambiental e estrutura da vegetação arbustivo-arbórea em três áreas de Cerrado sentido restrito no Sudoeste goiano

A variação fitofisionômica do Cerrado brasileiro é intensa e estudos fitossociológicos podem fornecer subsídios sobre quais fatores são responsáveis por essa heterogeneidade ambiental. Nesse sentido, esse estudo teve o objetivo de avaliar a estrutura da vegetação lenhosa de três áreas de cerrado sentido restrito, no município de Jataí - GO, buscando discutir os achados com o histórico de perturbação de cada área e aspectos físicos dos solos. Foram alocadas dez parcelas contíguas de 20×50 m em cada área, totalizando três hectares de levantamento no total. Incluíram-se na amostragem todos os troncos com diâmetro ≥ 5 cm, medidos a 30 cm do solo. As áreas apresentaram diferenças quanto à estrutura da vegetação lenhosa com formações mais abertas e outras mais densas (densidade de 991 a 1859 ind.ha-1 e área basal de 10,85 a 17,68 m2.ha-1). A riqueza florística variou de 70 a 82 espécies. Apesar de haver uma mistura de elementos florísticos savânicos e florestais entre as áreas, detectou-se maior domínio de espécies savânicas. Os padrões florístico e estrutural indicaram heterogeneidade nas comunidades em função de diferenças texturais do solo e incêndios. Isso reforça a importância da preservação de formações savânicas no sudoeste do estado para entender variações estruturais e florísticas e, consequentemente, fornecer informações para outros estudos sobre os aspectos ecológicos relacionados a eles.

Estimating parameters for the Kostiakov-Lewis infiltration model from soil physical properties

Infiltration modeling is an important tool to describe the process of water infiltration in the soil. However, direct measurements of the parameters of infiltration models are usually time-consuming and laborious. The present study proposed an effective method to estimate parameters of the Kostiakov-Lewis model (a classical infiltration model) from soil physical properties (SPPs). Parameters k, α, and f0 of the Kostiakov-Lewis infiltration models were measured in 240 double-ring field experiments in Shanxi Province, China. SPPs at the corresponding experimental points were measured at the topsoil layer (TL, 0–20 cm) and the top-subsoil layer (TSL, 0–20 and 20–40 cm). The Kennard-Stone (KS) sampling method and principal component analysis (PCA) were used for dividing training samples and extracting principal components (PCs) of SPPs, respectively. Partial least squares (PLS), back-propagation neural networks (BPNNs), and a support vector machine (SVM) were used to establish models for estimating k, α, and f0 with the SPPs of TL and TSL as the input variables (IV). The differences in soil density (BD), texture, and moisture content (θv) were found in topsoil and subsoil, but loading distributions of SPPs on PCs present different degrees of correlation. Moreover, SVM produced the most accurate estimation among these three methods for using the SPP of TL and TSL as inputs. The highest accuracy for k estimations was obtained by SVM using the SPP of TL as IV; R and RMSE in the model test process were 0.78 and 0.3 cm min−1, respectively. However, using SPP of TSL as IV obtained the highest accuracy for both α and f0 estimations with the SVM method (R values were 0.71 and 0.82, respectively, and RMSE values were 0.03 and 0.018 cm min−1) in the model testing. The SVM method with SPPs as inputs is an effective and practical method for estimating the parameters of the Kostiakov-Lewis infiltration model.

A new empirical model for the estimation of soil thermal conductivity

Soil thermal conductivity (λ) is an important thermal property which serves as an indicator for the coupling of soil, water, heat, and solutes in a numerical model. The objective of this study is to develop a new empirical model for estimating soil thermal conductivity. There are several methods for estimating λ available, but they are complicated and can produce relatively large errors. Using published datasets, the performance of the new estimate was evaluated along with nine other normalized models, and the advantages and disadvantages of each model and its relevant soil types were analyzed and compared. The results showed that the new empirical model is suitable for studying the thermal conductivities of soils of different textures. In the comparisons, it had the best performance among the ten models considered, with a minimum standard deviation (SD) of 0.074 W m−1 K−1, the coefficient of determination (R2) from 0.929 to 0.983 with a mean of 0.964, and relative error (Re), from 5.210 to 9.900% with a mean of 7.335%. The new model has been shown to improve the reliability of estimation of soil thermal conductivity and has application in agricultural science, environmental science, earth science and engineering research.

Assessment of rainwater harvesting sites in a part of North-West Delhi, India using geomatic tools

The study was conducted with an aim to provide practical solution for the groundwater management in three villages namely Singhola, Ghoga and Dhirpur of the North-West Delhi, India. LANDSAT remote-sensing datasets for the last four decades (1977–2018) were assessed to determine changes in vegetation cover at the selected sites. The Google Earth Engine was used to determine how values of the Normalized Difference Vegetation Index (NDVI) were found to have varied spatially and over time for the selected sites. Strong correlations were found between the NDVI values of surface features including waterbodies, forest land, agricultural land and urban areas in Singhola, Ghoga and Dhirpur, respectively. The relative infiltration capacity of soils was highest (92.9%) and lowest (57%) for Singhola and Dhirpur, respectively, due to spatial differences in soil texture. In each village, locations exhibiting a higher soil infiltration capacity could be used for implementing managed aquifer recharge schemes using rainwater harvested from rooftops in the villages. This assessment indicated that the village of Ghoga has the highest potential (3,76,98,013.08 m3) for aquifer recharge through rooftop rainwater harvesting as compared to the other two villages.

Approximate nutrient flux and concentration solutions of the Nye–Tinker–Barber model by the perturbation expansion method

The Nye–Tinker–Barber model is a basic and representative one for single-ion nutrient uptake by plant root from the soil and we aim to derive its approximate analytical solutions of flux and concentration. We divide the rhizosphere into the inner and the outer fields, match the inner and the outer solutions near the root surface, and then obtain the approximate analytical solutions of nutrient uptake flux at the root surface and global nutrient concentration of the diffusion or the convection-diffusion Nye–Tinker–Barber model. The analytical and numerical fluxes of K+ and H2PO4− decay quickly to 0 in less than 3 days while NO3− and Cd2+ gradually decrease in more than 15 days; the depletion profile spread of H2PO4− is apparently narrower than NO3− and K+ in 24 days. The different flux and concentration patterns of 4 nutrients result from their mobility and solubility in the rhizosphere. In comparison with the numerical simulations and the previous analytical results, we find that the analytical flux will overestimate the numerical flux of NO3− and Cd2+ while the analytical concentration can accurately predict the numerical concentration; the flux and the concentration solutions of the convection-diffusion Nye–Tinker–Barber model can be simplified to the diffusion versions by the Péclet number, and they can more widely describe the transport of nutrients of different attributes in soils of different textures with different levels of saturation, conductivity and permeability.

Observed variation in soil properties can drive large variation in modelled forest functioning and composition during tropical forest secondary succession.

Censuses of tropical forest plots reveal large variation in biomass and plant composition. This paper evaluates whether such variation can emerge solely from realistic variation in a set of commonly measured soil chemical and physical properties. Controlled simulations were performed using a mechanistic model that includes forest dynamics, microbe-mediated biogeochemistry, and competition for nitrogen and phosphorus. Observations from 18 forest inventory plots in Guanacaste, Costa Rica were used to determine realistic variation in soil properties. In simulations of secondary succession, the across-plot range in plant biomass reached 30% of the mean and was attributable primarily to nutrient limitation and secondarily to soil texture differences that affected water availability. The contributions of different plant functional types to total biomass varied widely across plots and depended on soil nutrient status. In Central America, soil-induced variation in plant biomass increased with mean annual precipitation because of changes in nutrient limitation. In Central America, large variation in plant biomass and ecosystem composition arises mechanistically from realistic variation in soil properties. The degree of biomass and compositional variation is climate sensitive. In general, model predictions can be improved through better representation of soil nutrient processes, including their spatial variation.

Use of HYDRUS-1D–GIS tool for evaluating effects of climate changes on soil salinization and irrigation management

ABSTRACTIn this study, HYDRUS-1D model was coupled with geographic information system (GIS) for evaluating the effects of climate changes on soil salinization. The coupled HYDRUS-1D–GIS system was applied in a coastal region (Gabes Oasis) for evaluating the effects of various climate change scenarios on temporal change in soil electrical conductivity (EC) and for developing irrigation practice that desalinates soils. The climate change scenarios were selected based on the climate change projections by 2050 and increased irrigation water allocations. There were three main findings. First, HYDRUS-1D and GIS were successfully coupled and used to perform simulation with consideration of the large differences in soil texture in the studied oasis. Second, for all climate change scenarios, spatial extent of EC for 2050 is projected to reach levels (> 4 dS m−1) corresponding with being classified as saline soils. Third, with climate changing as simulated, it is recommended to increase irrigation water application with 20% or more than today to avoid further increases in soil EC. Overall, this study can be used as a guide to implement the most appropriate strategy of soil and water management.

Fertilization and Application of Different Biochar Types and their Mutual Interactions Influencing Changes of Soil Characteristics in Soils of Different Textures

Fertilization and Application of Different Biochar Types and their Mutual Interactions Influencing Changes of Soil Characteristics in Soils of Different Textures

Agro-biological and economic efficiency in a beetroot (Beta vulgaris L.) production system fertilized with hairy woodrose (Merremia aegyptia (L.) Urb.) as green manure

Beetroot (Beta vulgaris L.) is a tuberous vegetable that is under experimentation in the vegetable production system in Rio Grande do Norte state (Brazil). It is quite demanding, in nutritional terms. One of the alternatives to meet this need is green manuring using spontaneous species of the Caatinga biome. The aim of the present work was to optimize the agro-biological performance and economic profitability of the beetroot 'Early Wonder', fertilized with different doses of hairy woodrose (Merremia aegyptia (L.) Urb.) in this semi-arid environment. Hairy woodrose is a spontaneous species of the Caatinga biome that is widely distributed, being found in forests, fences, forest clearings and fields, growing in soils of different textures, producing biomass with a high content of macronutrients. This material was collected from spontaneous vegetation, native to the region, and used as green manure.The experimental design was a randomized complete block, with four treatments and five replicates. The treatments consisted of four amounts of hairy woodrose biomass incorporated into the soil (10, 25, 40 and 55 t ha-1 of dry matter). The following agronomic characteristics were evaluated in each beetroot treatment: plant height, fresh mass of shoots, number of leaves per plant, dry mass of shoots and dry mass of roots, total and commercial root productivity, and root productivity classified into scrap and extra roots, extra A roots, extra AA and great roots. Apart from these characteristics, the following economic indicators were also determined for each treatment: gross income, net income, rate of return and profit margin. The maximum agro-biological efficiency of beet root productivity (22.68 t ha-1) was obtained from 44.92 t ha-1 of hairy woodrose biomass added to the soil. The maximum economic efficiency of the yield of beet roots was achieved as a net income of AU$2,491.00 (R$6,406.36) ha-1, provided by the production of 22.04 t ha-1 of commercial roots, using 37.03 t ha-1 of hairy woodrose biomass incorporated into the soil. The use of hairy woodrose as green manure presents agro-economic feasibility in beet cultivation in this semi-arid environment.

Salt leaching and response of Dianthus chinensis L. to saline water drip-irrigation in two coastal saline soils

Using of saline water is becoming an important approach to reclaim and utilize salt-affected soil for landscaping and agricultural purposes. A three-year field experiment was conducted in Hebei Province, North China to cultivate a perennial flower, Dianthus chinensis L., on two coastal saline soils of different textures, silt (27.79 dS·m−1) and sandy loam (27.33 dS·m−1), using the drip irrigation at five levels of water salinity (ECi = 0.8, 3.1, 4.7, 6.3 and 7.8 dS·m−1). Effect of water salinity on salt distribution in soil profile and plant growth and physiological response were investigated. The irrigation water salinity tolerance threshold of D. chinensis in terms of shoot dry weight was also evaluated. Results shown that, after three growing seasons, the highly saline soils reclaimed to < 8 dS·m−1 for silt soil and < 3 dS·m−1 for sandy loam soil under ECi < 7.8 dS·m−1. The soil salinity decreased with year and increased with increasing ECi. Better salt leaching effect occurred in sandy loam soil compared with silt soil. Plant height, clump diameter, and shoot dry weight as well as survival rate declined in response to increasing ECi, and survival rate of > 80% retained for all treatments in the third year. The decline of shoot K+ concentration, excessive accumulation of Na+, and concomitant reduction of K+/Na+ ratio were observed with increasing ECi. The irrigation water salinity thresholds of D. chinensis, aimed at biological production, are 3.17 dS·m−1 for silt soil and 1.62 dS·m−1 for sandy loam soil; for landscaping purpose, the corresponding values are 5.65 and 6.98 dS·m−1.

Lindane Bioremediation in Soils of Different Textural Classes by an Actinobacteria Consortium

Lindane is a highly chlorinated and recalcitrant insecticide, capable to accumulate in soil and groundwater. Despite lindane has been banned in many countries, numerous sites still remain contaminated. The present work studies the bioremediation of soils of different textures contaminated with lindane by bioaugmentation with a quadruple Streptomyces consortium. In the three evaluated soils, silty loam soil (SLS), sandy soil (SS), and clayey soil (CS), heterotrophic microbial populations increased during the 14 days of the assay and CFU counts were higher in bioaugmented than in non-bioaugmented soils. Lindane removal was detected in all contaminated treatments, with higher removal percentages in the bioaugmented microcosms (SS 70.3%, SLS 36.3%, and CS 30.7%), than in non-bioaugmented ones (SS 40.4%, SLS 9.3%, and CS 12.2%). The pesticide half-life decreased by 77.3, 50.3, and 10.7 days, in bioaugmented SLS, CS, and SS, respectively. Lindane had an inhibitory effect on soil enzyme activities such as dehydrogenase, fluorescein diacetate hydrolysis, acid and alkaline phosphatases and increased the catalase activity, in non-bioaugmented controls; however, no effect on urease activity was observed. Bioaugmentation of soil microcosms with actinobacteria increased all enzymatic activities. Finally, the survival of the four strains of the consortium was demonstrated at the end of the bioremediation assay. Bioremediation using the Streptomyces sp. A2-A5-A11-M7 consortium represents a promising tool to restore different types of soils contaminated with organochlorine pesticides.

Shifting cultivation maintains but its conversion to mono-cropping decreases soil carbon and nitrogen stocks compared to natural forest in Western Ethiopia

This study was conducted to assess the effects of shifting cultivation and its conversion to mono-cropping on soil organic carbon (SOC) and total nitrogen (STN). We compared soil pH, texture, bulk density and SOC and STN contents and stocks (0–100 cm) in natural forest (NF), adjacent shifting cultivation (SC) areas (> 100 years old) having three (SC-3Y), five (SC-5Y) and seven (SC-7Y)-year-old fallowing, and 10 year-old mono-cropping field (MCF) converted from shifting cultivation in Western Ethiopia. There was no significant difference in soil pH in NF and all shifting cultivation areas. However, MCF had lower soil pH compared to SC-3Y and SC-5Y. There was no or very little difference in soil texture and bulk density across the study sites. Shifting cultivation did not affect SOC and STN stocks. However, conversion of shifting cultivation to mono-cropping decreased SOC (45–50% over 10 years; loss of 11.6 ± 0.2 Mg C ha−1 yr.−1) and STN stocks (18–45% over 10 years; loss of 0.6 ± 0.1 Mg N ha−1 yr.−1). While shifting cultivation maintained SOC and STN, its conversion to mono-cropping decreased them, potentially contributing to global warming and decreasing soil fertility.

Impact of an Extreme Storm Event on River Corridor Bank Erosion and Phosphorus Mobilization in a Mountainous Watershed in the Northeastern United States

AbstractMovement of sediment, and associated phosphorus, from stream banks to freshwater lakes is predicted to increase with greater frequency of extreme precipitation events. This higher phosphorus load may accelerate harmful algal blooms in affected water bodies, such as Lake Champlain in Vermont, New York, and Québec. In the Mad River, a subwatershed in central Vermont's Lake Champlain Basin, extreme flooding from Tropical Storm Irene in 2011 caused extensive erosion. We measured stream channel change along the main stem between 2008 and 2011 by digitizing available prestorm and poststorm aerial imagery. Soils were sampled post Irene at six active stream erosion sites, using an experimental design to measure differences in soil texture and phosphorus both with depth (90 cm) and distance from the stream. In addition to total phosphorus (TP), we determined bioavailable (soil test) phosphorus (STP) and the degree of phosphorus saturation (DPS). The six sites represented a 0.87‐km length of stream bank that contributed an estimated 17.6 × 103 Mg of sediment and 15.8 Mg of TP, roughly the same as average annual watershed export estimates. At four sites, the STP and DPS were low and suggested little potential for short‐term phosphorus release. At two agricultural sites where the lateral extent of erosion was high, imagery showed a clear loss of well‐established riparian buffer. Present‐day near‐stream soils were elevated in STP and DPS. An increase in these extreme events will clearly increase sediment loads. There will also be increasing concentration of sediment phosphorus if stream banks continue to erode into actively managed agricultural fields.

Soil Physical Quality in Sugarcane Field Under Cover Crop and Different Soil Tillage Systems

Currently, the management practices employed in Brazilian sugarcane plantations have contribute to soil physical degradation and, few studies considering the effect of cover crop associated with conservationist soil tillage systems to control or even reverse this process. Therefore, with the aim to assess the impact of cover crop and tillage systems on the least limiting water range (LLWR) and the S index in two soils of different textures used for sugarcane production, a fieldwork was carried out in two sugarcane plantations in the state of S&amp;atilde;o Paulo, Brazil. The experimental design is a split-plot with four repetitions. The main factor consisted of soil cover vegetation: cover crop and fallow, and the second factor, the tillage system: minimum tillage and conventional tillage. The data of this study demonstrated that clayey and medium-textured soil are sensitive to the management systems used. The use of cover crop promoted an increase of LLWR (average incremental rate of 105% for clayey and 100% for medium-textured soil) and S index (average incremental rate of 16% for clayey and 10% for medium-textured soil). The maintenance of soil under fallow represented restrictive conditions for the growth/development of the plants due to the degradation of the soil structure. In addition, conservation management systems, such as minimum tillage, resulted in better soil physical quality when associated with cover crop. Finally, the clayey and medium-textured soil, show good S index during the first cycle of sugarcane cultivation.

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.