Yellow River Sediment as a Soil Amendment for Amelioration of Saline Land in the Yellow River Delta

Soil salinization and sedimentation in the Yellow River Delta pose significant environmental concerns in China. This study demonstrated for the first time that the Yellow River sediment can be used as a soil amendment to remediate the salt‐affected soil. Four treatments including the control (CK), Yellow River sediment application at 70 Mg ha⁻¹ (S70) and 140 Mg ha⁻¹ (S140), and crop residue application at 3 Mg ha⁻¹ (P3) were replicated in two blocks in the field. Cotton, one of the most common crops in the Yellow River Delta, was planted. Soil physical properties and electrical conductivity (EC) were measured. The results indicated that mixing the Yellow River sediment, a poorly graded sand, with the clayed saline soil improved soil texture, macroporosity, and saturated hydraulic conductivity. Mean EC of treated soils was significantly lower than for the control. Improved cotton emergence and stand establishment were observed along with a significant treatment effect on cotton yield. The effects of S140 and P3 on soil macroporosity, hydraulic conductivity, soil EC, and cotton growth were comparable. This study concluded that applying Yellow River sediment in the saline land is a technically feasible and environmentally sustainable approach for saline soil remediation in the Yellow River Delta. Copyright © 2014 John Wiley & Sons, Ltd.     

Field calibration of an impedance soil water probe for the shallow seedbed across field topography

Impedance soil water probes enable frequent and non‐destructive determination of soil water status in situations where gravimetric soil sampling is too demanding of time and sampling space. The ThetaProbe is an impedance soil water probe requiring calibration for local soil conditions, because measurement accuracy can be affected by properties of the soil. Often, only a single calibration is performed for an experimental site. An experiment investigating the seedbed to 75‐mm depth across a field topography with variable soil properties was examined to determine which soil properties affected the calibration of the ThetaProbe, and if soil‐specific calibration was required to derive suitable estimates of the water status in the experiment. Experimental factors examined included hillslope aspect, hillslope position, crop residue and soil depth. Soil properties, other than volumetric water content, significantly affecting the probe measurements were bulk density, electrical conductivity and temperature. The probe underestimated soil water at very low water contents, and overestimated soil water at contents greater than 11 m³ m^?3, compared with gravimetric measurements. A single calibration, not corrected for hillslope position at a water content of 20 m³ m^?3, overestimated water content by 0.02 m³ m^?3 in the summit hillslope position and underestimated water content by 0.04 m³ m^?3 in the toeslope position. A single calibration, not corrected for soil depth at a water content of 20 m³ m^?3, overestimated water content by 0.02 m³ m^?3 in the 0‐ to 25‐mm soil layer and underestimated water content by 0.03 m³ m^?3 in the 50‐ to 75‐mm layer. The complexity of microsites in a shallow seedbed requires soil‐specific calibration in field experiments containing heterogeneous soil properties.     

Soil hydraulic properties of two loess soils in China measured by various field-scale and laboratory methods

Knowledge of hydraulic properties is essential for understanding water movement in soil. However, very few data on these properties are available from the Loess Plateau of China. We determined the hydraulic properties of two silty loam soils on agricultural land at sites in Mizhi and Heyang in the region. Undisturbed soil cores were collected from seven layers to one meter depth to determine saturated hydraulic conductivity, soil water retention curves and unsaturated hydraulic conductivity (by the hot-air method). Additional field methods (internal drainage and Guelph permeameter) were applied at the Heyang site to compare differences between methods. Soil water retention curves were flatter at Mizhi than at Heyang. Water contents at saturation and wilting point (1500 kPa) were higher at Heyang than at Mizhi. However, unsaturated hydraulic conductivity was lower at Heyang than at Mizhi, with maximum differences of more than six orders of magnitude. Nevertheless, the two soils had similar saturated hydraulic conductivities of about 60 cm day^− 1. Comparison between the methods showed that soil water retention curves obtained in the laboratory generally agreed well with the field data. Field-saturated conductivities had similar values to those obtained using the soil core method. Unsaturated hydraulic conductivities predicted by the Brooks–Corey model were closer to field data than corresponding values predicted by the van Genuchten model.     

Influence of growing plants and nitrogen fertilizer on saturated hydraulic conductivity

Abstract

A field experiment was conducted on a sandy loam (typic Hapludoll) to test the effect of maize (Zea mays L.) and nitrogen (N) fertilizers on soil saturated hydraulic conductivity (Ksat). Half of the plots were planted to maize and the other half were kept unplanted. All the plots were fertilized at the rate of 75 kg ha^‐1, with two fertilizers differing in their acidity index [calcium ammonium nitrate (CAN)=16 and ammonium sulphate (AS)=111]. Undisturbed topsoil samples were taken at the time of maize harvest to determine soil Ksat in the laboratory. Total organic carbon (TOC) and soluble carbon (SC), pH (1:2.5), and the electrical conductivity (EC) of soil saturated extract were determined in grounded and sieved soil samples. The Ksat reached the highest values under maize fertilized with AS. Most of the variation of soil Ksat was determined by the increment of soil salinity. So, soil permeability improvements were caused by a greater flocculation of soil colloids because of saline effects. Soil pH decrease caused by these acid N sources did not provoke the dissolution of organic matter because none of the carbon (C)‐forms measured in the experiment were affected by the fertilization. Thus, other C‐compounds different from those here measured might be improving soil permeability.     

Time‐lapse monitoring of soil water content using electromagnetic conductivity imaging

The volumetric soil water content (θ) is fundamental to agriculture because its spatiotemporal variation in soil affects the growth of plants. Unfortunately, the universally accepted thermogravimetric method for estimating volumetric soil water content is very labour intensive and time‐consuming for use in field‐scale monitoring. Electromagnetic (EM) induction instruments have proven to be useful in mapping the spatiotemporal variation of θ. However, depth‐specific variation in θ, which is important for irrigation management, has been little explored. The objective of this study was to develop a relationship between θ and estimates of true electrical conductivity (σ) and to use this relationship to develop time‐lapse images of soil θ beneath a centre‐pivot irrigated alfalfa (Medicago sativa L.) crop in San Jacinto, California, USA. We first measured the bulk apparent electrical conductivity (EC_a – mS/m) using a DUALEM‐421 over a period of 12 days after an irrigation event (i.e. days 1, 2, 3, 4, 6, 8 and 12). We used EM4Soil to generate EM conductivity images (EMCIs). We used a physical model to estimate θ from σ, accounting for soil tortuosity and pore water salinity, with a cross‐validation RMSE of 0.04 cm³/cm³. Testing the scenario where no soil information is available, we used a three‐parameter exponential model to relate θ to σ and then to map θ along the transect on different days. The results allowed us to monitor the spatiotemporal variations of θ across the surveyed area, over the 12‐day period. In this regard, we were able to map the soil close to field capacity (0.27 cm³/cm³) and approaching permanent wilting point (0.03 cm³/cm³). The time‐lapse θ monitoring approach, developed using EMCI, has implications for soil and water use and management and will potentially allow farmers and consultants to identify inefficiencies in water application rates and use. It can also be used as a research tool to potentially assist precision irrigation practices and to test the efficacy of different methods of irrigation in terms of water delivery and efficiency in water use in near real time.     

Models relating soil pH measurements in water and calcium chloride that incorporate electrolyte concentration

Soil pH is the most routinely measured soil property for assessing plant nutrient availability. Nevertheless, there are various techniques for soil pH measurement, which vary with regard to the solution used and the soil‐to‐solution ratio. Soil pH is commonly measured in water or 0.01 m CaC1₂. Soil pH in CaCl₂ is usually preferred as it is less affected by soil electrolyte concentration and provides a more consistent measurement. Therefore there is a need to convert measurement values between the two methods. Previous models reported linear and curvilinear relationships between the two measurements. However, the pH difference between measurements in water and CaCl₂ is related to the soil solution electrolyte concentration. We observed that the pH difference between the two methods became smaller with increasing soil electrical conductivity (EC). We therefore developed models that relate pH in CaCl₂ and water and incorporate EC values. We calibrated a linear and a non‐linear model (artificial neural networks, ANN) using 9817 soil samples from Queensland, Australia. Soil pH in water and CaCl₂ and EC were measured with a 1:5 soil‐to‐solution ratio. The results show that incorporating EC in the prediction model improves the prediction of pH in CaCl₂ significantly. We validated these models using 4576 independent samples obtained from a diverse range of soils across Australia. Although the linear and ANN models performed similarly, the ANN (which has a curvilinear relationship) provided a better prediction and aligns with the theory that for acid and alkaline pH values, the difference between pH in water and CaCl₂ is less than that for pHs between 4.5 and 7.     

Salinity and sodicity induced changes in dispersible clay and saturated hydraulic conductivity in sulfatic soils

Abstract

Irrigation is becoming a more commonly used practice on glacially derived soils of the Northern Great Plains. Threshold salinity and sodicity water quality criteria for soil‐water compatibility in these sulfatic soils are not well defined. This study was conducted to relate soil salinity and sodicity to clay dispersion and saturated hydraulic conductivity (K_sat) in four representative soils. Soil salinity (EC treatment levels of 0.1 and 0.4 S m^‐1) and sodicity (SAR treatment levels of 3, 9, and 15) levels were established to produce a range of conditions similar to those that might be found under irrigation. The response of each soil to changes in salinity and sodicity was unique. In general, as sodicity increased clay dispersion also increase, but the magnitude of the increase varied among the soils. In two of the soils, clay dispersion across a range of sodicity levels was lower under the 0.4 S m^‐1 treatment than under the 0.1 S m^‐1 treatment and in the other two soils, clay dispersion across a range of sodicity levels was similar between the two salinity treatments. Changes in K_sat were greatest in the finer textured soil (decreasing an order of magnitude across the range of sodicity levels), but was unchanged in the coarse textured soils. Results suggest that these sulfatic soils are more susceptible to sodicity induced deterioration than chloridic soils. These results and earlier field observations suggest that sustainable irrigation may be limited to sites with a water source having a SAR <5 and an EC not exceeding 0.3 S m^‐1 for these sulfatic glacially derived soils.     

Effects of consecutive applications of gypsum in equal,increasing, and decreasing quantities on soil hydraulic conductivity of a saline‐sodic soil

The objective of this study was to determine the effects of consecutive application of gypsum dissolved in leaching water on hydraulic conductivity of a saline‐sodic soil. Drainage type plastic columns with a 10 cm diameter were used in this laboratory experiment. Soil depth within columns was 30 cm with an average bulk density of 1.38 g cm^–3. Leaching water was applied in six equal portions. Total gypsum was applied at 1, 3, and 5 portions after dissolving in leaching water. In dissolution, equal (1.273 + 1.273 + 1.273 Mg ha^–1), increasing (0.637 + 1.273 + 1.910 Mg ha^–1) and decreasing (1.910 + 1.273 + 0.637 Mg ha^–1) quantities of gypsum were used. Results were compared with the control treatment, in which total amount of gypsum were mixed with surface layer of soil column before leaching. Hydraulic conductivity of soil increased in all treatments. The maximum hydraulic conductivity value was obtained at consecutive application of gypsum at decreasing quantities.     

Tillage Effects on Soil Quality Indicators and Nematode Abundance in Loessial Soil under Long‐Term No‐Till Production

Abstract: Soil quality indicators and nematode abundance were characterized in a loessial soil under long‐term conservation tillage to evaluate the effects of no‐till, double‐disk, chisel, and moldboard plow treatments. Indicators included soil electrical conductivity (EC), soil texture, soil organic matter (SOM), and total particulate organic matter (tPOM). Nematode abundance was positively correlated with EC, silt content, and total POM and negatively correlated with clay content. Clay content was the main source of variation among soil quality indicators and was negatively correlated with nematode abundance and most indicators. The gain in SOM in the no‐till system amounted to 10887 kg over the 24 years or 454 kg ha^?1 year^?1, about half of this difference (45%) resulting from soil erosion in plowed soils. The balance of gain in SOM with no till (249 kg ha^?1 year^?1) was due to SOM sequestration with no till. No‐till management reduced soil erosion, increased SOM, and enhanced soil physical characteristics.     

不同灌水水平下一膜两年覆盖间作农田 耗水特征及经济效益研究

以河西走廊区主导间作模式玉米|豌豆间作系统为研究对象,在高(7 200 m3·hm-2)、中(6 450 m3·hm-2)、低(5 700 m3·hm-2)3种灌水水平下,研究了一膜两年覆盖、秋免耕春覆膜和传统耕作覆膜对间作群体耗水量和棵间蒸发的影响,以期为间作种植模式的优化耕作措施、地膜再利用、提高水分利用效率等提供理论依据。结果表明,不同灌水水平对间作群体生育期棵间蒸发量存在显著影响,随灌水水平的提高棵间蒸发量增大;但在相同灌水水平下不同覆膜方式间差异不明显,且互作效应不显著;不同处理豌豆收获前、后,间作农田棵间蒸发在玉米带和豌豆带存在显著差异,不同处理收获前、后豌豆带棵间蒸发量平均值较玉米带分别高68.51%和69.30%;豌豆带是造成间作农田系统蒸发耗水大的主要因素,占地60%的玉米带棵间蒸发量只占农田蒸发总量的44.47%,而占地仅为40%的豌豆带蒸发量却占55.53%;玉米间作豌豆农田棵间蒸发主要发生在豌豆收获以后,豌豆收获前的棵间蒸发仅占总蒸发量的26.98%。一膜两年覆盖可显著提高单方水效益,不同灌水处理平均值较秋免耕春覆膜和传统耕作覆膜方式分别提高7.39%和31.33%,且在中等灌水条件下一膜两年覆盖的单方水效益最高,达2.51元·m-3。研究结果表明相同灌水水平下一膜两年覆盖玉米带抑制农田棵间蒸发、减少水分无效损失的效果与传统覆膜方式相当;农田棵间蒸发量、耗水结构(E/ET)与灌水水平间呈正相关关系;在中等灌水水平下一膜两年覆盖可获得较高的经济效益。     

Influences of nitrogen treatments and irrigation methods on soil chemical properties

Abstract

Changes in soil chemical properties were investigated in conjunction with an ongoing study of fertility and irrigation relationships of cotton. Four irrigation methods and five nitrogen fertilization rates were the primary focus of the study. The four irrigation regimes studied were: high frequency center pivot, low frequency center pivot, furrow irrigated, and unirrigated. Nitrogen rates were 0, 30, 60, 90, and 120 lb N/A. Soil samples were collected from each plot in 6‐in‐ increments to a depth of 24 in. in 1982 and again in 1986 after four years of continuous cotton production. The soil samples were analyzed for pH, organic matter (OM), P, K, electrical conductivity (EC), and NO₃ ^‐‐N. All background soil characteristics were found to vary with depth with the exception of NO₃ ^‐‐N. The follow‐up sampling and testing in 1986 showed significant differences in soil properties as a function of irrigation, N‐fertilization, depth, and their interactions. Nitrates were accumulated in the 18 to 24‐in. depth under high (120 lb N/A) fertilization, and in the 0 to 6‐in. depth under the four lower treatments (0, 30, 60, and 90 lb N/A). Soil pH was highest in the furrow and high frequency center pivot irrigated regimes and lowest in the unirrigated regime. Soil pH also decreased with depth. Electrical conductivity of the soil was highest in the high frequency regime and not significantly different among the other three irrigation methods. The 0M content of the soil was greatest in the high frequency regime but not significantly different in the low frequency, furrow, or unirrigated blocks. Soil 0M was found to decrease with depth through 18 in. in all cases. The P and K status of the soil was not changed as a result of the N fertilization or irrigation treatments.     

土壤盐分的原位测定方法

在干旱半干旱地区,土壤盐溃化是制约农业生产的重要因素.土壤盐分的测定和诊断是土壤盐渍化研究工作中的重要内容,传统上一般通过测定土壤浸提液电导率来测定土壤盐分,过程繁琐,费时费事,不可避免地要破坏原土样.在提倡精准农业的今天,土壤盐分的快速、有效和可靠的原位测定显得非常重要.土壤盐分原位测量方法有多种,在原理上可分为土壤...     

Field and laboratory approaches for determining sodicity effects on saturated soil hydraulic conductivity

Dilution of high-sodicity soil water by low-sodicity rainfall or irrigation water can cause declining soil hydraulic conductivity (K) by inducing swelling, aggregate slaking and clay particle dispersion. Investigations of sodicity-induced reduction in K are generally restricted to repacked laboratory cores of air-dried and sieved soil that are saturated and equilibrated with sodic solution before tests are conducted. This approach may not yield a complete picture of sodicity effects in the field, however, because of loss of antecedent soil structure, small sample size, detachment of the sample from the soil profile, reliance on chemical equilibrium, and differing time scales between laboratory and field processes. The objectives of this study were to: (i) compare the electrical conductivity (EC), exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) in laboratory cores of intact field soil that had, or had not, undergone prior saturation and equilibration with sodic solution; (ii) compare the pressure infiltrometer (PI) field method with the intact laboratory soil core (SC) method for assessing sodicity effects on saturated soil hydraulic conductivity; and (iii) characterize hydraulic conductivity reduction in a salt-affected sandy loam soil and a salt-affected clay soil in Sicily as a result of diluting high-sodicity soil water with low-sodicity water.In terms of EC, ESP and SAR, quasi-equilibrium between soil and infiltrating solution was attainable in 0.08 m diameter by 0.05 m long laboratory cores of intact clay soil, regardless of whether or not the cores were previously saturated and equilibrated with solutions of SAR=0 or 30. In the sandy loam soil, the PI and SC methods produced statistically equivalent linear reductions in K as a result of diluting increasingly sodic soil water (SAR=0, 10, 20, 30) with deionised water. In the clay soil, the PI method produced no significant correlation between initial soil water SAR and K reduction, while the SC method produced a significant log-linear decline in K with increasing soil water SAR. Sodicity-induced reductions in K ranged from 3–8% (initial soil water SAR=0) to 85–94% (initial soil water SAR=30) in the sandy loam, and from 9–13% (initial soil water SAR=0) to 42–98% (initial soil water SAR=30) in the clay. The reductions in K were caused by aggregate slaking and partial blocking of soil pores by dispersed clay particles, as evidenced by the appearance of suspended clay in the SC effluent during infiltration of deionised water. As a result, maintenance of K in these two salt-affected soils will likely require procedures to prevent or control the build-up of sodicity.     

Response of Corn Growth in Salt‐Affected Soils of Northeast China to Flue‐Gas Desulfurization By‐product

Abstract

In semiarid and arid regions, plant growth is limited by high pH, salinity, and poor physical properties of salt‐affected soils. A field experiment was conducted in the semiarid region of Kangping in northeast China (42°70′ N, 123°50′ E) to evaluate a soil‐management system that utilized a by‐product of flue‐gas desulfurization (FGD). Soil was treated with 23,100 kg ha^?1 of the by‐product. Results of corn growth were grouped into three grades (GD) according to stages of corn growth: GD1, seeds did not germinate; GD2, seeds germinated but corn was not harvested; and GD3, plants grew well and corn was harvested. The pH, electrical conductivity (EC), bicarbonate (HCO₃ ^?), carbonate (CO₃ ^2?), exchangeable and soluble calcium (Ca²⁺), chloride (Cl), and sulfate (SO₄ ^2?) in surface soils of the three grades (>20 cm) was measured to assess the correlation between corn growth and soil properties. Vertical differences in subsoil properties (0‐100 cm) between GD1 and GD3 were compared to known benchmark soil profiles. The FGD by‐product significantly increased EC, exchangeable and soluble Ca²⁺, and SO₄ ^2? and decreased CO₃ ^2?, exchangeable sodium (Na⁺), and soluble Na⁺. pH, EC, HCO₃ ^?, CO₃ ^2?, and Cl^? were higher in surface soils of GD1 than GD3. Soil hardness, soil moisture content, Cl^?, and calcium carbonate (CaCO₃) were higher in GD1 than in GD3, whereas the amount of available P was lower in GD1. Interestingly, the concentration of Cl^?, a toxic element for plant growth, was 2.5 and 1.5 times higher in GD1 than in GD3 and control soil, respectively. In the comparison study of subsoils, GD1 and GD3 were classified as having typical characteristics of saline‐alkali soil (pH>8.5; exchangeable‐sodium‐percentage [ESP]>15; EC>4.0) and alkali soil (pH>8.5; ESP>15; EC<4.0), respectively.     

Structural disruption of arable soils under laboratory conditions causes minor respiration increases

Previous field studies in N Europe have shown that the impact of soil tillage on soil respiration is mostly indirect, caused by altered distribution of plant residues in soil affecting decomposition of residues. Tillage operations alter soil moisture and temperature conditions in soil, which control decomposition dynamics. Experiments under laboratory conditions allow indirect effects of altered residue decomposition to be distinguished from direct effects of mechanical disruption, i.e., the increased exposure of substrates within aggregates and micropores upon tillage. This study examined the effects of physical disruption of soils with different soil texture, land‐use history, and soil organic C content on soil respiration under controlled abiotic conditions. Undisturbed soil samples from 7 sites (arable land and grassland) were incubated at 20°C and three different water potentials (–1, –10, and –30 kPa). Soil respiration was measured before and after physical disruption with laboratory homogenizer, using an automated respiration apparatus. Soil organic C, water content, and bulk density explained 67% of the variation in base respiration. In half of the disrupted samples, bulk density was re‐adjusted by re‐compaction to conditions prevailing before disruption. Disruption and re‐compaction generally resulted in higher respiration flushes than disruption alone. Respiration peaks increased with water content. However, total C losses were small and corresponded to < 0.1 Mg C ha^?1. Overall, physical soil disruption increased decomposition of soil organic matter only marginally and temporarily. It would be difficult to detect an effect of tillage on soil organic matter decomposition under field conditions.     

Movement of nitrogen‐15 labeled nitrate in large undisturbed columns of poorly drained soil

Abstract

A laboratory study was conducted with large (20‐cm i.d., 110‐cm long PVC pipe) intact soil columns to determine the movement of fertilizer NO₃ ^‐ in poorly drained, conventionally tilled soil under simulated low (7.6 cm) and heavy (15.2 cm) rainfall. Soil in the columns was brought to near‐maximum water‐holding capacity (9 kPa) to simulate the typical field soil moisture regime during the spring. A constant‐level water table was imposed at the base of the column to further simulate field conditions of the Drummer silty clay loam (mixed, mesic, Typic Haplaquoll) soil used. Fertilizer was applied in solution at a rate equivalent to 168 kg N ha^‐1 as ¹⁵N‐labeled KNO₃. Water was then applied in three applications, spaced one wk apart. To minimize the movement of water along the soil‐pipe interface, a 3 mm‐wide band of air‐dried disturbed soil was packed around the core to ensure a seal along the interface. Recovery of fertilizer NO₃ ^‐‐N below the water table at the end of the 28‐d study was < 0.06% (0.1 kg N ha^‐1) and 0.5% (0.9 kg N ha^‐1) of that applied for the low and high treatments, respectively. Denitrification losses were negligible for both water treatments (≤ 1 kg N ha^‐1). Fertilizer N distribution in the columns indicated significant movement of N beyond estimated water‐displacement depths, apparently caused by preferential flow. However, the majority of the N was restricted to the upper portions of the columns. The results indicate that preferential flow of water in poorly drained, conventionally tilled soils during high rainfall periods can lead to the movement of fertilizer N to shallow ground water, but that the amounts are apparently very small.     

Potential to predict depth‐specific soil–water content beneath an olive tree using electromagnetic conductivity imaging

Efficient monitoring of soil moisture is becoming increasingly important. To understand soil–plant–water dynamics, we evaluate the potential of using a multiple‐coil‐array electromagnetic induction instrument and inversion software to map soil moisture beneath an olive tree. On twelve different days, we collected apparent electrical conductivity (EC _a) data using a DUALEM ‐21S and the volumetric soil moisture (θ ) using a bank of soil moisture sensors on opposite sides of the tree. Using EM 4Soil, we inverted the EC _a data on five of the days and established a site‐specific calibration between estimates of true electrical conductivity (σ ) and θ . The strongest calibration relationship between σ and θ (R ² = 0.65) was obtained for a full‐solution, S2 algorithm and damping factor of 1.2. A leave one out cross‐validation (LOOCV ) showed the calibration was robust, with a root mean square error (RMSE ) of 0.046 m³/m³, a mean error (ME ) of 0.001 m³/m³ and a Lin's concordance of 0.72. We subsequently evaluated the calibration relationship on the seven remaining days and over a drying period of 120 days. This approach provides information about the temporal evolution of θ by a LOOCV of validation with a RMSE of 0.037, ME of −0.003 and a Lin's concordance of 0.54. Improvement could be achieved by aligning the DUALEM ‐21S in the same orientation as the sensors, with time‐lapse inversion also being advantageous.     

A Comparative Study of Different Amendments on Amelioration of Saline-Sodic Soils Irrigated with Water Having Different EC: SAR Ratios

Soil degradation affects soil properties such as structure, water retention, porosity, electrical conductivity (EC), sodium adsorption ratio (SAR), and soil flora and fauna. This study was conducted to evaluate the response of contrasting textured soils irrigated with water having different EC:SAR ratios along with amendments: gypsum (G), farm manure (FM), and mulch (M). Water of different qualities viz. EC 0.6 + SAR 6, EC 1.0 + SAR 12, EC 2.0 + SAR 18, and EC 4.0 + SAR 30 was used in different textured soils with G at 100% soil gypsum requirement, FM at 10 Mg ha^?1, and M as wheat straw was added on surface soil at 10 Mg ha^?1. Results revealed that the applied amendments in soils significantly decreased pH_s and electrical conductivity (EC_e) of saturated paste and SAR. Four pore volumes of applied water with leaching fraction 0.75, 0.77, and 0.78 removed salts 3008, 4965, and 5048 kg ha^?1 in loamy sand, silty clay loam, and sandy clay loam soils, respectively. First four irrigations with LF of 0.82, 0.79, 0.75, and 0.71, removed 5682, 5000, 3967, and 2941 kg ha^?1 salts, respectively. The decreasing order for salt removal with amendments was FM > G > M > C with LF = 0.85, 0.84, 0.71, and 0.68, respectively. This study highlights a potential role of soil textures to initiate any mega program for reclamation of saline-sodic soils in the perspective of national development strategies.     

Effects of soil compaction and water‐filled pore space on soil microbial activity and N losses

Abstract

Soil compaction is a significant production problem for agriculture because of its negative impact on plant growth, which in many cases has been attributed to changes in soil N transformations. A laboratory experiment was conducted to study the effect of soil compaction and water‐filled pore space on soil microbial activity and N losses. A hydraulic soil compaction device was used to evenly compress a Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudults) soil into 50 mm diameter by 127 mm long cores. A factorial arrangement of three bulk density levels (1.4, 1.6, and 1.8 Mg/m³) and four water‐filled pore space levels (60, 65, 70, 75%) was used. Fertilizer application of 168 kg N/ha was made as 1.0 atom % ¹⁵N as NH₄NO₃. Soil cores were incubated at 25°C for 21 d. Microbial activity decreased with both increasing water‐filled pore space and soil bulk density as measured by CO₂‐C entrapment. Nitrogen loss increased with increasing bulk density from 92.8 to 334.4 g N/m³ soil at 60% water‐filled pore space, for 1.4 and 1.8 Mg/m³, respectively. These data indicate that N loss and soil microbial activity depends not only on the pore space occupied by water, but also on structure and size of soil pores which are altered by compaction.     

基于Android的车载式土壤电导率和光谱反射率检测系统

This paper aims to develop a vehicular integrated system collecting soil electrical conductivity(EC) and spectral reflectance.The system could collect soil EC and spectral reflectance automatically when the vehicle moves and save these measurement results with GPS.The information could reflect the characteristics of soil parameters such as soil salinity and water content.Hence, an Android-based vehicular detection system for soil conductivity and spectral reflectance information was developed.Soil electrical conductivity measurement was performed based on improved "current-voltage" four-terminal method.A STS-NIR spectrometer was used for collecting near-infrared spectral reflectance.The system collected the information of soil electrical conductivity and soil spectral reflectance while collecting GPS, which could be used for precision agriculture.The system was tested in a farm of Beijing on March 25, 2014.Soil electrical conductivity of the farmland was measured and soil samples were collected.Water content and soil electrical conductivity were measured in the laboratory.The result of these experiments showed that the system could work stably in farmland and had good prospects.