Mean spectral reflectance from bare soil pixels along a Landsat-TM time series to increase both the prediction accuracy of soil clay content and mapping coverage

Earth Observation (EO) has an immense potential as an enabling tool for mapping the spatial variation of the topsoil layer. Additionally, machine learning based algorithms deployed on cloud computing infrastructures have a great potential to revolutionize the processing of EO data. This paper aims to present a multi-dimensional Sentinel-based Soil Monitoring Scheme (S2MoS) based on open-access Copernicus Sentinel data and the Google Earth Engine platform to map soil properties. Building on key results from existing data mining approaches to extract bare soil reflectance values the current study presents i) preliminary insights on the synergistic use of open access SAR and optical images obtained from Sentinel-1 and Sentinel-2 sensors; and ii) evaluate the efficiency of machine learning algorithms to predict soil attributes based on multi-temporal analysis. In that regard, this study evaluated, based on Sentinel images extending over a 3 years period (2017-2019), the performance of two state of the art machine learning approaches, namely random forest and neural networks. Spatial thresholds values of 0.25 and 0.075 for Normalized Difference Vegetation Index and Normalized Burn Ratio 2 indices respectively were applied to mask bare soil pixels. In this study, we used 5000 soil data belonging to cropland land use from the European LUCAS topsoil database. We calibrated the models based on 4000 soil samples and then validated this approach with the rest 1000 samples &#160;predict soil clay content. A higher prediction performance (R2=0.53) was achieved by the inclusion of both types (SAR and optical) of observations using the neural network model, demonstrating an improvement of about 5% in overall accuracy compared to the R2 using the multi-year median optical composite.

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Litter as a filter of emergence for herbaceous seedlings and sporophytes in central Amazonia

Journal of Tropical Ecology ◽

10.1017/s0266467412000491 ◽

2012 ◽

Vol 28 (5) ◽

pp. 445-452 ◽

Cited By ~ 5

Author(s):

Flávio Rogério de Oliveira Rodrigues ◽

Flávia Regina Capellotto Costa

Keyword(s):

Clay Content ◽

Dispersal Limitation ◽

Distribution Patterns ◽

Bare Soil ◽

Wet Season ◽

Litter Addition ◽

Litter Depth ◽

Central Amazonia ◽

Soil Clay ◽

Soil Clay Content

Abstract:We conducted a study in 30 plots distributed uniformly in an area of 25 km2 at Ducke Reserve, Manaus, to test the hypothesis that understorey herb richness and abundance are mediated by litter, manipulating experimentally the amount of litter in the field. Over 10 mo, we followed the emergence of herbaceous seedlings and sporophytes in control, litter-addition and litter-exclusion treatments, covering an area of 1.2 m2 per plot in each treatment. We also assessed the relationship between topography and litter depth and frequency of bare-soil patches; and the influence of density of reproductive individuals on the emergence of herbs. Litter depth decreased, and the frequency of bare-soil patches increased with terrain slope in the wet season, but were not related with the soil clay content. Neither was related to the topography in the dry season. Emergence of pteridophytes was four times higher in the litter-exclusion treatment (3.7 ± 1.1 individuals m−2) than in the litter-addition treatment (0.9 ± 0.28 indiv. m−2) and increased with soil clay content. Seedlings from monocot herbs emerged twice more frequently in the litter exclusion (0.71 ± 0.25 indiv. m−2) than in the litter-addition treatment (0.33 ± 0.11 indiv. m−2), and also more in sites with high density of fruiting plants. The results are consistent with the hypothesis that regeneration of herbs with very small propagules is strongly affected by the physical barrier imposed by litter. Given that litter is shallower on slopes during the wet season, this creates a pattern of higher density and richness of pteridophytes in these areas. Monocot herbs, although also limited by litter, were more highly limited by availability of propagules, and their distribution patterns are at least in part explained by dispersal limitation. We conclude that litter is an important causal factor behind the herb distribution patterns along topographical gradients.

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Remaining phosphorus and sodium fluoride pH in soils with different clay contents and clay mineralogies

Pesquisa Agropecuária Brasileira ◽

10.1590/s0100-204x2004000300006 ◽

2004 ◽

Vol 39 (3) ◽

pp. 241-246 ◽

Cited By ~ 6

Author(s):

Marcelo Eduardo Alves ◽

Arquimedes Lavorenti

Keyword(s):

Buffer Capacity ◽

Ammonium Oxalate ◽

Clay Mineralogy ◽

Clay Content ◽

Response Curves ◽

Solution Ph ◽

Ph Values ◽

Soil Clay ◽

Soil Clay Content ◽

Discriminatory Capacity

The remaining phosphorus (Prem) has been used for estimating the phosphorus buffer capacity (PBC) of soils of some Brazilian regions. Furthermore, the remaining phosphorus can also be used for estimating P, S and Zn soil critical levels determined with PBC-sensible extractants and for defining P and S levels to be used not only in P and S adsorption studies but also for the establishment of P and S response curves. The objective of this work was to evaluate the effects of soil clay content and clay mineralogy on Prem and its relationship with pH values measured in saturated NaF solution (pH NaF). Ammonium-oxalate-extractable aluminum exerts the major impacts on both Prem and pH NaF, which, in turn, are less dependent on soil clay content. Although Prem and pH NaF have consistent correlation, the former has a soil-PBC discriminatory capacity much greater than pH NaF.

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P-sorption and desorption in Savanna Brazilian soils as a support for phosphorus fertilizer management

Ciência e Agrotecnologia ◽

10.1590/s1413-70542013000600005 ◽

2013 ◽

Vol 37 (6) ◽

pp. 521-530 ◽

Cited By ~ 17

Author(s):

Flávio Araújo Pinto ◽

Edicarlos Damacena de Souza ◽

Helder Barbosa Paulino ◽

Nilton Curi ◽

Marco Aurélio Carbone Carneiro

Keyword(s):

Clay Content ◽

Soil Characteristics ◽

Fertilizer Management ◽

Phosphorus Fertilizer ◽

Phosphorus Adsorption ◽

P Sorption ◽

Brazilian Soils ◽

Soil Clay ◽

Sand Base ◽

Soil Clay Content

Phosphorus (P) sorption by soils is a phenomenon that varies depending on soil characteristics, influencing its intensity and magnitude, which makes it a source or drain of P. The objective of this study was to determine the Maximum Phosphorus Adsorption Capacity (MPAC) and desorption of P from soils under native Savanna Brazilian and verify the correlation between MPAC and P Capacity Factor (PCF) with the chemical and physical properties of these soils. The study was conducted in seven soils under native Savannas. The Langmuir isotherms were adjusted from the values obtained in sorption assays, being evaluated the MPAC, the energy adsorption (EA) and PCF, which was calculated according to the levels of P-adsorbed and P-sorbed. Values of MPAC were classified as high in most soils, ranging from 283 up to 2635 mg kg-1 of P in the soil and were correlated with soil organic matter, clay, silt, sand, base saturation and pH. The PCF was higher in soils where the MPAC was also higher. The use of only one attribute of soil (clay content) as a criterion for the recommendation of phosphated fertilization, as routinely done, is susceptible to errors, needing the use of more attributes for a more accurate recommendation, as a function of the complexity of the interactions involved in the process.

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Surface soil clay content mapping at large scales using multispectral (VNIR–SWIR) ASTER data

International Journal of Remote Sensing ◽

10.1080/01431161.2018.1528018 ◽

2018 ◽

Vol 40 (4) ◽

pp. 1506-1533

Author(s):

Anis Gasmi ◽

Cécile Gomez ◽

Philippe Lagacherie ◽

Hédi Zouari

Keyword(s):

Surface Soil ◽

Clay Content ◽

Aster Data ◽

Soil Clay ◽

Soil Clay Content

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Factors Affecting Microbial Formation of Nitrate-Nitrogen in Soil and Their Effects on Fertilizer Nitrogen Use Efficiency

The Scientific World JOURNAL ◽

10.1100/tsw.2001.308 ◽

2001 ◽

Vol 1 ◽

pp. 122-129 ◽

Cited By ~ 7

Author(s):

Alan Olness ◽

Dian Lopez ◽

David Archer ◽

Jason Cordes ◽

Colin Sweeney ◽

...

Keyword(s):

Organic Matter ◽

Decision Aid ◽

Pore Space ◽

Organic Matter Content ◽

Clay Content ◽

Matter Content ◽

N Fertilizer ◽

Nitrate N ◽

Soil Clay ◽

Soil Clay Content

Mineralization of soil organic matter is governed by predictable factors with nitrate-N as the end product. Crop production interrupts the natural balance, accelerates mineralization of N, and elevates levels of nitrate-N in soil. Six factors determine nitrate-N levels in soils: soil clay content, bulk density, organic matter content, pH, temperature, and rainfall. Maximal rates of N mineralization require an optimal level of air-filled pore space. Optimal air-filled pore space depends on soil clay content, soil organic matter content, soil bulk density, and rainfall. Pore space is partitioned into water- and air-filled space. A maximal rate of nitrate formation occurs at a pH of 6.7 and rather modest mineralization rates occur at pH 5.0 and 8.0. Predictions of the soil nitrate-N concentrations with a relative precision of 1 to 4 μg N g–1of soil were obtained with a computerized N fertilizer decision aid. Grain yields obtained using the N fertilizer decision aid were not measurably different from those using adjacent farmer practices, but N fertilizer use was reduced by >10%. Predicting mineralization in this manner allows optimal N applications to be determined for site-specific soil and weather conditions.

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Determination of the Environmental Factors that Affect the Growth and Survival of Greek Fir Seedlings

Land ◽

10.3390/land9040100 ◽

2020 ◽

Vol 9 (4) ◽

pp. 100

Author(s):

Vassilis Detsis ◽

Georgios Efthimiou ◽

Olga Theodoropoulou ◽

Stavroula Siorokou

Keyword(s):

Regression Model ◽

Mixed Model ◽

Linear Mixed Model ◽

Clay Content ◽

Weather Conditions ◽

Apical Growth ◽

Growth And Survival ◽

Initial Height ◽

Soil Clay ◽

Soil Clay Content

Forests in the montane-Mediterranean zone have only recently began to be affected by wildfires, therefore the knowledge necessary for restoration projects is missing. The aim of the study was to assess the effects of factors related to seedling attributes, weather conditions and site suitability on seedling performance. The characterisation of sites was based on bedrock and soil clay content as well as pre-fire vegetation. Apical growth and survival of seedlings was monitored for four years in Parnitha National Park. The parameters of a linear mixed model were estimated using annual apical growth of seedlings surviving in the end of the study as the dependent variable and type of site, rainfall, initial seedling height and age as explanatory ones. A quantile regression model using all the data available was estimated for each year of study, taking into account only initial height and site type as well as a logistic regression model of survival. The findings indicate that the growth of Greek fir seedlings depends on May rainfall mediated by soil clay content, which in turn depends on bedrock, which is consistent with the “inverse texture hypothesis”. Sites with low soil clay content were always more beneficial for survival, which was stronger affected by summer–autumn rainfall. In both contexts, drought stress due to soil clay content fades with increasing age. Sites that were not fir dominated prior to fire proved unsuitable also for planting fir seedlings. A minor part of the observed variability could be associated with the initial height of seedlings, especially for seedlings showing high rates of apical growth.

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Effects of Soil Clay Content on Water Balance and Productivity in Rainfed Lowland Rice Ecosystem in Northeast Thailand

Plant Production Science ◽

10.1626/pps.10.232 ◽

2007 ◽

Vol 10 (2) ◽

pp. 232-241 ◽

Cited By ~ 26

Author(s):

Mitsuru Tsubo ◽

Shu Fukai ◽

Jayampathi Basnayake ◽

To Phuc Tuong ◽

Bas Bouman ◽

...

Keyword(s):

Water Balance ◽

Clay Content ◽

Lowland Rice ◽

Northeast Thailand ◽

Rainfed Lowland ◽

Soil Clay ◽

Soil Clay Content ◽

Rice Ecosystem

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Soil clay content, rainfall, and toposequence positions determining spatial variation in field water availability as estimated by a water balance model for rainfed lowland rice

Crop and Pasture Science ◽

10.1071/cp12108 ◽

2012 ◽

Vol 63 (6) ◽

pp. 529 ◽

Cited By ~ 7

Author(s):

T. Inthavong ◽

M. Tsubo ◽

S. Fukai

Keyword(s):

Water Balance ◽

Water Availability ◽

Clay Content ◽

Lowland Rice ◽

Balance Model ◽

Yield Reduction ◽

Growing Period ◽

Rainfed Lowland ◽

Soil Clay ◽

Soil Clay Content

Drought is a major limiting factor for the production of rainfed rice in the Mekong Region. Thus, estimation of the length of growing period (LGP) based on estimation of the development of water deficit is essential for sound planning of agricultural development. A recently developed soil-water balance model was used to quantify the availability of water for rice crops and yield reduction due to water deficit. Field water availability is known to be largely affected by soil type and rainfall pattern, and their separate effects were investigated in this study of a spatial analysis of LGP, using inputs for rainfed lowland rice in Savannakhet province in central Laos. The analysis showed that the start of growing period (SGP) and end of growing period (EGP) were affected largely by geographical variations in rainfall and soil clay content, respectively. Also, the areas having relatively short LGP were generally associated with large yield reduction because of low water availability associated with coarse-textured soils. At local scale, field water availability varied from upper to lower positions of a sloping land (toposequence) in the rainfed lowland ecosystem of the Mekong region, causing variation in yield within the toposequence. Using the level of field water determined around flowering time at different toposequence positions in 45 farms, estimated yield reduction was compared in seven main rice-growing districts of the province. Variability of yield loss, associated with variation in water availability, was larger across the toposequence positions than across districts, showing the importance of local variability in determining yield in rainfed lowland rice. The present approach of a combination of simulation model and GIS is adopted for characterisation of the water environment for rainfed lowland rice in other parts of Laos, as well as in neighbouring Thailand and Cambodia.

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