第１報 耕土の移動割合算出のための電気伝導度法による基礎実験 ロータリ耕うんにおける耕土の移動に関する研究

We discussed two methods to calculate displacement ratio of the soil tilled by rotary tillage in our first report. The present report is concerned with the results of application for the estimation of displacement ratio of the soil tilled by down-cut and up-cut rotary tillages. This paper also deals with the distribution of electrical conductivity on the soils in various upland fields.The results are as follows.1) The electrical conductivity of soil at the upland fields under the natural condition showed the value of 74.6-399.0μS/cm and the each field differed remarkably in electrical conductivity. This result was caused by the remaining rate of electolyte produced by chemical fertilizer.2) From the comparison of electrical conductivity before tillage with one after tillage, the soil displacement in the backward and forward by rotary tillage was confirmed.3) The large variation of displace-ment ratio of the tilled soil was observed between mesuring points [b2-b4 points to stabilize originally] in up-cut rotary experiment. The variation was also remarkably larger than one of down-cut rotary tillage, because of the variation of electrical conductivity of soil mixing KCI.4) In case of the method by conditional inequality, the ratio of soil displacement is calculated with a certain range. According to the results of this experiment, its range was the value within ±1.1%. This degree of ranges are practically negligible.5) The difference of soil displace-ment ratio between the method by simultaneous equations of three unknowns and conditional inequa-lity was 0.5% at the most except one case. Therefore, we think that validity of the both methods was proved.6) Synthesizing the various experiment results of this parper, the electrical conductivity method used the mixture soil of KCI is effective as method to estimate the displacement ratio of soil tilled by rotary tillage.

Soil pH and electrical conductivity (EC) are two major chemical properties affecting nutrient availability and rice grain yield. Therefore, this study was conducted to investigate the variation of pH and EC in the topsoil layer (0-15 cm) of rice fields as affected by major water source used for rice cultivation, rice-based cropping system adopted and rice growing soil orders in different agro-climatic zones (ACZs) in Sri Lanka. A total of 998 soil samples were collected from lowland rice fields. Both pH and EC were measured in 1:5 soil: water extracts. The pH of soil samples was in the range of 3.0-7.7 with a mean value of 5.0. Moreover, 75% of the soil samples had pH values below the optimum range for rice cultivation (5.5-7.0). Values of pH observed in Dry Zone soils were higher (5.2) than those in Wet Zone (4.4). Soil EC values ranged between 1.0 - 3,100 μScm−1 with a mean value of 148.5 μScm−1. Soil EC was similar among climatic zones (P>0.05). Upcountry Intermediate zone recorded the highest soil EC than that in other ACZs (P<0.05). Moreover, 73%, 22%, 3%, 2% and 0.1% of soil samples recorded EC values in the ranges of less than 150 (non-saline), 150-400 (slightly saline), 400-800 (moderately saline), 800-2000 (highly saline) and more than 2000 (very highly saline) μScm−1, respectively. Considering micro (e.g. paddy track) and macro (e.g. ACZ) scale spatial heterogeneity in soil pH and EC, appropriate site-specific strategies need to be adopted to improve soil pH and EC to suit sustainable rice crop production.

A farm's soil moisture and soil electrical conductivity (EC)readings are extremely valuable for a farmer. They can help her reduce water use and improve productivity. However, the high cost of commercial soil moisture sensors and the inaccuracy of sub-1000 dollar EC sensors have limited their adoption. In this paper, we present the design and implementation of a system, called Strobe, that senses soil moisture and soil EC using RF propagation in existing Wi-Fi bands. Strobe overcomes the key challenge of limited bandwidth availability in the 2.4 GHz unlicensed spectrum using a novel multi-antenna technique. It maps the propagation time and amplitude of Wi-Fi signals received by different antennas to the soil permittivity and EC, which in turn depend on soil moisture and salinity. Our experiments with USRP, WARP, and commodity Wi-Fi cards show that Strobe can accurately estimate soil moisture and EC using Wi-Fi, thereby showing the potential of a future where a farmer can sense soil in their farm without investing 1000s of dollars in sensing tools.

The accurate monitoring of soil salinization plays a key role in the ecological security and sustainable agricultural development of semiarid regions. The objective of this study was to achieve the best estimation of electrical conductivity variables from salt-affected soils in a south Mediterranean region using Sentinel-2 multispectral imagery. In order to realize this goal, a test was carried out using electrical conductivity (EC) data collected in central Tunisia. Soil electrical conductivity and leaf electrical conductivity were measured in an olive orchard over two growing seasons and under three irrigation treatments. Firstly, selected spectral salinity, chlorophyll, water, and vegetation indices were tested over the experimental area to estimate both soil and leaf EC using Sentinel-2 imagery on the Google Earth Engine platform. Subsequently, estimation models of soil and leaf EC were calibrated by employing machine learning (ML) techniques using 12 spectral bands of Sentinel-2 images. The prediction accuracy of the EC estimation was assessed by using k-fold cross-validation and computing statistical metrics. The results of the study revealed that machine learning algorithms, together with multispectral data, could advance the mapping and monitoring of soil and leaf electrical conductivity.

To clarify the nutrient characteristics of 'salt island' and 'fertile island' effects in saline-alkali soil, the native Tamarix chinensis of the Yellow River Delta (YRD) was selected to measure its soil pH,electrical conductivity (EC), organic carbon (SOC),total nitrogen (N),total phosphorus (P) and their stoichiometry characteristics at different soil depths. The results showed that soil pH and EC increased with the increasing soil depth. Soil EC and P in the 0-20 cm layer decreased and increased from canopied area to interspace,respectively. SOC,N,N/P and C/P in the 20-40 cm soil layer decreased, and C/N increased from the shrub center to interspace. SOC and N contents between island and interspace both decreased but P content decreased firstly and then increased with the increasing soil depth. Soil pH correlated positively with EC. In addition, pH and EC correlated negatively with C,N,P contents and their ecological stoichiometry.

This research explores the use of soil electrical conductivity (EC) in rice cultivation, focusing on soil EC correlation with vegetation indices (NDVI, NDRE) and soil EC impact on yield. A total of 228 soil EC, NDVI, and NDRE data points were collected from an 11,000 m² field in Hau Giang and Can Tho City. Soil EC was measured at the beginning of the season, and at 39 and 49 days after sowing. NDVI was recorded on days 39, 49, 60, and 72, with initial values set to zero due to no crop presence. Results show that soil EC decreased from the start to day 49, while NDVI and NDRE increased. Spearman correlation analysis revealed strong relationships between early soil EC and NDVI at days 39 and 49 (r = 0.82, 0.71), and between soil EC at day 49 (EC 49) and NDRE at later stages (r = 0.594, 0.565). Additionally, 150 soil EC and yield samples from five Mekong Delta regions were used in an LSTM model (70% training, 30% testing), achieving high accuracy (RMSE = 0.0919, MAE = 0.0634, R2 = 0.8492). The findings suggest that soil EC is a valuable indicator for monitoring crop growth and managing rice production, particularly in areas affected by salinity due to climate change.

Electrical conductivity of some soils in Trinidad as affected by density, water and peat content

This study aimed to elucidate the response of soil microbial communities to saline soil amelioration via biological organic fertilizer. A year-long experiment was conducted on coastal saline soil, employing water and fertilizer strategies. Three treatments were compared: dry field (control, CK), paddy field (W), and combined dry and irrigated fields with biological organic fertilizer (BW). Soil DNA was extracted and sequenced using high-throughput methods, revealing significant reductions in soil electrical conductivity (EC) and pH with W and BW treatments. Moreover, the BW treatment notably increased soil organic carbon content by 17.2%, as well as soil urease and alkaline phosphatase activity. Fungal community richness increased, with the BW treatment showing a 36% rise in the ACE index and a 24% increase in the Shannon index, while the Simpson index decreased by 59%. Dominant fungal phyla were Ascomycota, Mortierellomycota, and Basidiomycota, with Basidiomycota prevailing at the genus level. Redundancy analysis (RDA) indicated that soil pH, EC, and organic carbon were key determinants of fungal community distribution, with the BW treatment correlating negatively with pH and salt and positively with soil organic carbon (SOC). Fungal functional groups varied among treatments, with saprophytic fungi predominating, but the BW treatment showed a higher relative abundance of animal pathogenic fungi. In summary, the integration of biological organic fertilizer with flooding ameliorates soil properties and influences the changes in soil fungal community structure and function in the short term. These results could enhance the scientific basis for the efficient utilization and development of saline soil resources in coastal areas.

The study’s specific objective is to identify prospective cashew nut (Anacardium occidentale) producing areas in the Bankura district based on soil availability and land suitability in red and lateritic soil. The index of crop suitability (ICS) analysis was carried out utilizing the Fuzzy-analytical hierarchy process (F-AHP) approach and 16 geo-environmental variables such as soil texture, soil organic carbon (OC), Soil electrical conductivity (EC), soil pH, slope, rainfall, etc. The criteria were also developed following FAO's crop suitability index for the distinction between S (suitable) and N (unsuitable) order. According to the cashew suitability class, 9.24% of cashew growth regions can be categorised as highly suitable, 34.57% as moderately suitable, and 19.59% as marginally suitable. The F-AHP weight shows the important factors of cashew cultivation that are soil OC and EC. The results demonstrate that cashew production is more beneficial in the red and lateritic soil.

The electrical conductivity (EC) Resistively (calculated) and salinity of some selected soil samples collected from three landforms, namely Beach Ridge Sand (BRS), coastal plain sand (CPS), sandstone/shale Hill ridges (SHR) from Akwa Ibom State of the Federal Republic of Nigeria were measured the obtained data were subjected to spearman rank order statistics and result shows that there were positive correlation of 0.20 between soil EC and salinity. The electrical conductivity of the area under study falls within the range of 0.031 ds/m for SHR 3A t0 0.200ds/m for SHR 2A while the salinities are between 0.6mg/l for BRS 3B and 0.9mg/l for SHA 2A soil samples. Soil sample SHR 3A has the highest resistivity measurement of 32.Ωm, while SHR 2A soil sample has the lowest of 6. Ωm. from the EC data the signal strength of EC measurements decreases with soil depth and most of the EC values falls within the range of 20 - 80 (µs/cm) which is the optimum level for most plants, usually indicates well - fertilized soils and salt sensitive plants may be insured.

土壤可溶性有机碳(DOC)、可溶性有机氮(DON)及其官能团特征在土壤碳、氮循环中作用非常重要。对25个不同年龄落叶松林样地、4个深度(0-20、20-40、40-60和60-80 cm)土壤DOC、DON、有机物官能团(芳香性、分子量和疏水性)特征指标(254、260、272 nm和280 nm的单位吸光度值SUVA:吸光度值/DOC含量)和土壤理化指标(土壤全碳SOC、全氮SON、pH值、电导率、容重)进行测定,旨在探究它们的时、空变化特征及与土壤理化指标相关关系。在空间尺度上,与SOC、SON一致,表层土壤DOC、DON多显著高于深层(<em>P</em><0.05),但是4个单位吸光度值SUVA₂₅₄、SUVA₂₆₀、SUVA₂₇₂和 SUVA₂₈₀均不存在差异(<em>P</em>>0.05);在时间尺度上,仅表层土壤DOC、SOC 和SON随落叶松年龄显著线性增长(<em>P</em><0.05),而深层DOC、SOC、SON、不同层土壤DON及各官能团指标均没有显著变化(<em>P</em>>0.05)。可见,土壤可溶性有机物内碳的累积(7 mg kg^-1 a^-1)是SOC累积的一部分(762 mg kg^-1 a^-1),但其DON及可溶性有机物芳香性比例、分子量大小及疏水性容量等官能团特征并未受落叶松生长时间以及土壤深度的显著影响。进一步回归分析表明这些官能团指标随土壤DOC含量增加而指数下降,深层土壤同时受DON显著影响。表层土壤DOC、DON与土壤SOC、SON、土壤电导率显著正相关(<em>P</em><0.05),深层相关不显著(<em>P</em>>0.05),而官能团指标与土壤理化性质的相关性在各个土层均不显著,显示出表层土壤可溶性有机物的量,而不是官能团组成对土壤理化性质影响显著,而深层土壤可溶性有机物量对土壤理化性质不构成显著影响。对于从可溶性组分、官能团角度,分析落叶松人工林成长过程中土壤碳、氮时空变化具有科学意义。;Soil dissolved organic carbon (DOC) and nitrogen (DON), and their composition play key roles in soil carbon sequestration and nutrient cycling. In this paper, DOC, DON and specific ultraviolet absorbance (SUVA at 254 nm, 260 nm, 272 nm and 280 nm, equaling to the measured absorbance divided by the DOC concentration) of dissolved organic matter, as well as soil physical-chemical parameters (soil organic carbon SOC, soil total nitrogen SON, pH value, electrical conductivity and bulk density) were determined in 0-20, 20-40, 40-60 and 60-80cm soil layers of 25 chronosequence larch plantations. The aim of this paper is to explore the temporal-spatial change of DOC, DON, SOC, SON and functional group (aromaticity, apparent molecular size and hydrophobic capacity) parameters, and their influences on soil physical-chemical properties. In the vertical profile, DOC, DON, SOC and SON in surface soil layer were significantly higher than those in the deep soil layers (<em>P</em><0.05), while no significant differences were found in SUVA₂₅₄, SUVA₂₆₀, SUVA₂₇₂ and SUVA₂₈₀ (<em>P</em>>0.05); During of the development larch plantation, DOC, SOC and SON at the surface soil (0-20cm) linearly increased with larch age (<em>P</em><0.05), while no significant changes were observed in deep soils. DON, aromaticity, apparent molecular size and hydrophobic capacity of all testified soil layers did not significantly change with larch age (<em>P</em>>0.05). Thus, DOC accumulation at surface 0-20cm soil (7 mg kg^-1 a^-1) should be a part of the SOC accumulation (762 mg kg^-1 a^-1), while no marked temporal changes were observed in both SON, DON and functional groups. Different from the significant space-temporal changes in total and dissolved C and N, composition of functional group relating to aromaticity, apparent molecular size and hydrophobic capacity were not affected by larch age and soil depth (<em>P</em>>0.05). A further regression analysis showed that these functional groups exponentially decreased with DOC and also significantly related to DON in the deep layer. Pearson correlations showed DOC and DON in surface soil positively correlated with SOC, SON and soil electrical conductivity (<em>P</em><0.05), while no significant relations between SUVA₂₅₄, SUVA₂₆₀, SUVA₂₇₂, SUVA₂₈₀ and soil physical-chemical properties were found in each soil layer. This indicates that quantity, rather than composition of dissolved organic matter could determine soil physical-chemical property, especially in surface soil. Our findings have scientific significance in understanding dynamics processes of soil carbon and nitrogen from the view of soluble components and functional groups during the plantation development.

Information about the nutrients distribution in sand-mulched soils is rather scarce; therefore, the aim of this experiment was to determine the spatial distribution and mobility of macronutrients in the wet bulb zone in two sand-mulched soils (a technique where manure and sand are layered over existing soil) for fertigated green bean with a drip irrigation distribution system under greenhouse conditions. The experimental design was multifactorial (4): soil type (S1 (1.0% organic matter (OM)) and S2 (2.5% OM)), time of sampling (before planting and after crop harvest) and spatial distribution: distance (0.1, 0.2, and 0.3 m) from the emitter and soil depth (0.1–0.2, 0.2–0.3 and 0.3–0.4 m) with three blocks and one replication per block. The chemical parameters (pH, electrical conductivity (EC), and macronutrients concentration) were analyzed in each soil sample. The testing crop was green bean (Phaseolous vulgaris L. c.v. Mantra RZ), lasting 90 days. The results obtained showed the highest value of EC and NO3−-N, K, and Ca concentration in the sand layer in both soils. At all soil profile depths, nutrient concentrations of NH4+-N and soil EC were lower in the high OM soil. Comparing the soil profile at the beginning and at the end of the experiment, there was a significant decrease in NO3−-N, P and Ca concentration and a significant increase in EC value and Mg concentration at the end of the crop. In distance, EC and K showed the highest concentration at 0.30 m. In depth, there was a decline in EC value and NH4+-N, P, K, Ca and Mg concentration. The comparison between the sand layer and the soil profile in both soils reported a similar trend in pH, EC, NO3−-N, P and Mg concentration. Considering the mobility of macronutrients in a sandy mulched soil, it would be recommendable to develop a sustainable and dynamic fertigation management, adjusting nutrient inputs over time.

Abstract. Salt accumulation in the root zone limits agricultural productivity and can eventually lead to land abandonment. Therefore, monitoring the spatial distribution of soil water content and solution salinity is crucial for effective land and irrigation management. However, assessing soil water content and salinity at the field scale is often challenging due to the heterogeneity of soil properties. Electromagnetic induction (EMI) offers a fast, non-invasive, in situ geophysical method to map spatial variability in soil. EMI instruments measure the apparent soil electrical conductivity (ECa), which reflects the integrated contribution of the bulk electrical conductivity (σb) of different soil layers. By inverting the measured ECa, it is possible to obtain the distribution of the σb along the soil profile, which provides indirect information on soil salinity. However, in saline soils, σb is influenced by both water content (θ) and soil solution electrical conductivity (σw) (the salinity), making it difficult to independently quantify these two variables through a single, straightforward procedure. The objective of this study is to separate the respective contributions of θ and σw to σb, as obtained from the EMI inversion. To achieve this, ECa was measured using a CMD-MiniExplorer instrument in two maize plots irrigated with saline and non-saline water, respectively, in an agricultural field in southern Italy. The dataset was then inverted in order to obtain the σb distribution. By employing a site-specific calibrated Rhoades linear model and assuming pedological homogeneity between the two plots, the spatial distribution of θ and σw in the saline plot was successfully estimated. To validate the results, independent measurements of soil water content by Time Domain Reflectometry (TDR) and direct measurement of soil solution electrical conductivity, σw, were performed. The proposed procedure enables the estimation of θ and σw with high accuracy along the soil profile, except in the soil surface, where EMI reliability is limited. These findings demonstrate that the integration of EMI with a site-specific θ–σb–σw model is a reliable and efficient in-situ approach for mapping soil salinity and water content at field scale, offering valuable insights for optimizing agricultural irrigation management in systems using saline water.

A global meta-analysis of the effects of irrigation with water containing salts on saline-alkali soils

Soil properties influencing apparent electrical conductivity: a review