Soil Testing Laboratories Research Articles

Evaluación de diferentes agentes de extracción del suelo para estimar la disponibilidad de B para maíz (Zea mays L.)

A greenhouse experiment was conducted with twenty surface (0-15 cm) soil samples using maize (cv. Pragati) as a test crop to estimate the critical limits of B in soil and plant. Five soil extractants used in the study varied in their B extraction capacity and could be arranged in the order: Mehlich 3 (pH 2.0) > 0.005 M DTPA + 1 M ammonium bicarbonate (pH 7.6) > 1 M MgCl 2 (pH 6.0) > 0.01 M CaCl 2 > Hot water. All B extractants employed in the present investigation showed highly significant relationships with Bray’s percent yield of maize. The critical limits of B in soil for maize were 0.61 mg hot water soluble B, 2.06 mg AB-DTPA extractable B, 1.03 mg 0.01 M CaCl 2 extractable B, 2.20 mg 1 M MgCl 2 extractable B and 2.56 mg Mehlich 3 extractable B kg -1 soil. The critical limit of B in maize (cv. Pragati) plants of 30 d age was found to be 11.2 mg B kg -1 dry plant tissue. The dry matter yields of maize plants related significantly to AB-DTPA (pH 7.6), 1 M MgCl 2 (pH 6.0) and Mehlich 3 (pH 2.0). Boron concentration and total B uptake by maize plants related significantly to extractable soil B estimated by only AB-DTPA (pH 7.6), 0.01 M CaCl 2 , 1 M MgCl 2 (pH 6.0) and Mehlich 3 (pH 2.0). Among soil extractants examined in the present study, Mehlich 3, a multi-nutrient extractant, appeared to be more suitable for predicting B deficiency in soils as this method had easy adoptability in soil testing laboratories owing short extraction time requirement.

EXTRACTION METHODS AND POTASSIUM AVAILABILITY FOR SOYBEAN IN THE PARANA STATE’S SOILS, BRAZIL

Evaluating the potassium (K) availability to the plants can be performed by different methods. In general, multielement methods are employed and they are used for K due to increase operational of soil testing laboratory. T he efficacy of ammonium acetate, Mehlich-1, Mehlich-3 and ion exchange resin soil K extractantsin determining the K availability for soybean [ Glycine max L. (Merrill) ], in different Parana’s soils, were investigated in this study. Twelve soil samples, collected from the upper layer 0–0.20 m, were cultivated with soybean for 42 days in greenhouse conditions. The average amount of available soil K extracted in test soils was found, displayed in decreasing order: ammonium acetate > Mehlich-3 > Mehlich-1 = ion exchange resin. The correlation coefficients between the K extracted content by ammonium acetate, Mehlich -1, Mehlich-3 and ion exchange resin and the K accumulated amount in the plants were, respectively, 0. 90, 0.77, 0.88 and 0.89 . The efficacy of ammonium acetate, Mehlich-3 and ion exchange resin extractants in assessing plant-available K in soils from Parana State were similar. The Mehlich-1 was the least efficient in estimating plant-available K in Parana’s soils. Normal 0 21 false false false PT-BR X-NONE X-NONE

Kansas Fertilizer Research 2013

The 2013 edition of the Kansas Fertilizer Research Report of Progress is a compilation of data collected by researchers across Kansas. Information was contributed by faculty and staff from the Department of Agronomy, Kansas agronomy experiment fields, and Agricultural Research Southeast Agricultural Research Center and research-extension centers. We greatly appreciate the cooperation of many K-State Research and Extension agents, farmers, fertilizer dealers, fertilizer equipment manufacturers, agricultural chemical manufacturers, and representatives of various firms who contributed time, effort, land, machinery, materials, and laboratory analyses. Without their support, much of the research in this report would not have been possible. Among companies and agencies providing materials, equipment, laboratory analyses, and financial support were Agrium, Inc.; Cargill, Inc.; Deere and Company; U.S. Environmental Protection Agency; FMC Corporation; Fluid Fertilizer Foundation; Foundation for Agronomic Research; Honeywell, Inc.; Hydro Agri North America, Inc.; IMC-Global Co.; IMC Kalium, Inc.; Kansas Agricultural Experiment Station; Kansas Conservation Commission; Kansas Corn Commission; Kansas Department of Health and Environment; Kansas Fertilizer Research Fund; Kansas Grain Sorghum Commission; Kansas Soybean Commission; Kansas Wheat Commission; Iogen Corporation; MK Minerals, Inc.; Nutra-flo; Monsanto; Pioneer Hi-Bred International; International Plant Nutrition Institute; Pursell Technology, Inc.; Servi-Tech, Inc; The Sulphur Institute; Winfield Solutions; and U.S. Department of Agriculture-Agricultural Research Southeast Agricultural Research Center Service. Special recognition and thanks are extended to Troy Lynn Eckart of Extension Agronomy for help with preparation of the manuscript; Kathy Lowe and Melissa Pierce, the lab technicians and students of the Soil Testing Lab, for their help with soil and plant analyses; and Mary Knapp of the Weather Data Library for preparation of precipitation data. Contributors A.R. Asebedo, Graduate Student, Dept. of Agronomy, K-State, Manhattan L.M. Bastos, Graduate Student, Dept. of Agronomy, K-State, Manhattan H.D. Bond, Assistant Scientist, Southwest Research-Extension Center, Tribune C.L. Edwards, Graduate Student, Dept. of Agronomy, K-State, Manhattan R. Florence, Research Assistant, Dept. of Agronomy, K-State, Manhattan T.J. Foster, Graduate Student, Dept. of Agronomy, K-State, Manhattan G. Hettiarachchi, Associate Professor, Soil and Environmental Chemistry, Dept. of Agronomy, K-State, Manhattan D.B. Mengel, Professor, Soil Fertility and Nutrient Management, Dept. of Agronomy, K-State, Manhattan C.W. Rice, Professor, Soil Microbiology, Dept. of Agronomy, K-State, Manhattan D.A. Ruiz Diaz, Assistant Professor, Soil Fertility and Nutrient Management, Dept. of Agronomy, K-State, Manhattan A.J. Schlegel, Agronomist, Southwest Research-Extension Center, Tribune D.W. Sweeney, Soil and Water Management Agronomist, Southeast Agricultural Research Southeast Agricultural Research Center Center, Parsons

Strength and deformation properties of Norwegian clays from laboratory tests on high-quality block samples

It has for a long time been a challenge for the geotechnical profession to determine the true behaviour of clays based on soil sampling and laboratory testing. The main difficulty has been to retrieve sufficiently undisturbed samples that maintain the clay structure and correctly depict the in situ stress–strain and strength behaviour of the clay under any kind of imposed drained or undrained loading conditions. The extent and impact of the disturbance caused by sampling depends on a number of factors, such as the specific sampling equipment and sampling procedures that are used, index properties of the clay (sensitivity and plasticity index in particular), and sampling depth. Experience with laboratory tests on conventional piston samples shows that sample disturbance commonly affects the test results. In the mid 1970s, the University of Sherbrooke developed a special block sampler that was shown to give samples of very high quality. Between 1982 and 2010, the Norwegian Geotechnical Institute (NGI) has used the Sherbrooke block sampler at 22 different sites in Norway and one site in the UK. Two to five block samples were collected at each site, on which oedometer, undrained triaxial, and direct simple shear (DSS) tests were carried out in the laboratory. Essentially all samples tested showed far superior quality as compared to conventional piston samples. It was therefore considered to be valuable to summarize test results obtained on such high-quality samples, as presented herein. Deformation and strength parameters from individual tests are summarized and compared against index data for the different clays tested. This has resulted in a series of correlation diagrams. The index parameters found of most relevance to use as correlation parameters are the natural water content and clay sensitivity. The latter is expressed in two categories: medium to low sensitivity (St< 15) and high sensitivity (St> 15). The overconsolidation ratio is another key parameter. The correlation diagrams presented include the following: (i) pre-consolidation pressure, compressibility, permeability, and permeability change index as derived from oedometer tests; (ii) normalized peak and post-peak shear strength, peak effective friction angle, stiffness, and strain at failure from undrained triaxial and DSS tests. When design analyses are to be based on the results of tests on high-quality block samples, as compared to conventional piston samples of poorer quality, it is important to ensure that the end result complies with past semi-empirical experiences.

Engineering Assessment of South-Eastern Niger Delta Soils Utilized for Highway Pavement

Engineering properties of soils recovered along a road alignment route (right-of-way) and borrow pits of a 30 km road in the South-Eastern Niger Delta area, Nigeria were assessed for utilization as highway pavement earth materials. Laboratory soil tests conducted included the natural moisture content, grain size distribution analysis, consistency limits, standard proctor compaction and California bearing ratio (CBR). About thirty-five (35) soil samples were retrieved from the fifteen (15) boreholes and examined. Results show that all identified and examined soil samples from the borings along the road route and the borrow pits classified as A- 3, A-2-4 and A-2-6 are excellent sub-grade, good fill and sub-base materials. However, none of the soil types meet the engineering requirements for use as base course. Earth materials comprising overburden of clayey sands, silty sands and sandfills (previously used as sub-grades) along the Ahoada-Upatabo-Oyigba-Ebiriba-Ombor 30 km. road in South-eastern Niger Delta were evaluated for highway pavement construction. The results are presented in this paper. The objective of the study was to examine the appropriateness of these soils for the purpose of pavement design and construction as sub-grades, sub-base and base course materials. Previous related studies in the area include works by (1-5).

Decision support system for soil and water analysis and fertiliser recommendation for flue-cured Virginia (FCV) tobacco

Soil fertility and water quality play an important role on the productivity of any crop. Soil and water test based fertilizer recommendation will help the farmers to optimize the resources and to improve the productivity. Decision Support System (DSS) was developed for calculating the instrument reading into final value of the test parameters of soil (pH, EC, organic carbon, available nitrogen, phosphorous, potassium and chloride) and water (pH, EC, chloride), to suggest the recommended doses of fertilizers for Flue-Cured Virginia (FCV) tobacco crop and to test their suitability for tobacco cultivation. DSS on soil and water analysis for tobacco crop was developed with Visual Basic. Net as Front-end and MS-Access as Back-end. In this system, by entering instrument reading, it will be transformed into soil / water testing value of the concerned parameter which will be compared with recommended values and finally suitability of soil and water for tobacco cultivation will be judged and recommended fertilizer doses for different tobacco zones will be prepared and printed in the prescribed format. This software will be helpful to the researchers / technical personnel in reducing time for preparation of reports, minimizing the errors in manual calculation and improves the precision. This system can be applicable to any soil testing laboratories, where recommendations are given to different crops based on soil and water test values with suitable modifications. Key words: Decision support system, flue cured tobacco, irrigation water quality, soil testing.

Comparison of Copper, Manganese, and Zinc Extraction with Mehlich 1, Mehlich 3, and DTPA Solutions for Soils of the Brazilian Coastal Tablelands

Deficiency of micronutrients is increasing in crop plants in recent years in Oxisols and Ultisols in the tropics. The predominant soils in the coastal tablelands of Brazil are Ultisols and Oxisols, with low cation exchange capacity and kaolinitic clay mineralogy. Soil copper (Cu), manganese (Mn), and zinc (Zn) extracted by the Mehlich 1 solution, currently used in the regional soil-testing laboratories, were compared with those extracted by the Mehlich 3 and diethylenetriaminepentaacetic acid (DTPA) solutions in a greenhouse experiment with 10 soil samples (0–20 cm deep) collected from representative Ultisols and Oxisols from various locations in the region. Corn was grown as a test crop, and its dry matter and micronutrient uptake was measured at 30 days of growth. Soil Cu, Mn, and Zn extracted with the three solutions were significantly correlated (0.65–0.95 range for r values), with the Mehlich 3 solution extracting greater quantities than the Mehlich 1 and DTPA solutions. Zinc and Cu taken up by corn plants were significantly related to their soil-extractable levels measured at harvest with all three of the solutions, except for Zn DTPA. However, similar relations between plant uptake and soil extractable Mn were poor, except for DTPA extracting solution.

Experimental Research of Soft Soil Ground Treatment in Yangpu Port by Static-Dynamic Drainage Consolidation

Yangpu Port has inhomogeneous soft soil with the properties of high water content, high void ratio, high compressibility and low shear strength. Based on soft soil ground treatment engineering practice, the geological characteristics are summarized, the ground treatment methods are comparatively analyzed, static-dynamic drainage consolidation method is chosen to treat the soft soil ground, the reinforcing mechanism of vertical and horizontal drainage system are discussed, the design of drainage system, preloading and dynamic consolidation are researched and the surface settlement monitoring, pore water pressure monitoring, side piling displacement monitoring, laboratory soil test and plate loading tests are carried out. The results show that average surface settlement is 1170.8 mm, the physical and mechanical properties of soft soil are improved and the characteristic value of foundation bearing capacity is greater than 120kPa.

Experimental Study on Expansion Characteristics, Frost Heaving Characteristics of EPS Beads Improved Expansive Soils

Proposed EPS beads for the improvement of expansive soil in cold regions. Based on laboratory soil test study the feasibility and mechanism of the EPS beads improving expansive soils. Through four sets of comparative test with different contents of the EPS beads, the result indicates: The expansion rate of the soil, frost heave amount decreases with the increase in EPS beads content, EPS beads can effectively inhibit the expansion of expansive soil and frost heaving, proposed the optimal dosage.

Role of suction in sandy beach habitats and the distributions of three amphipod and isopod species

Sandy beach ecology has progressed rapidly with the emergence of several theories developed on the basis of understanding of hydrodynamic and morphodynamic processes on sandy beach habitats. However, the possible role of dynamic geophysical processes in the sediments remains poorly understood. The present study aims to explore the role of such geophysical processes in the sediments in forming the habitat environment and how they influence the species distributions. We conducted sets of integrated observations and surveys on intertidal and supratidal geophysical environments and the distributions of three amphipod and isopod species at four exposed sandy beaches located on the Japan Sea coast of Niigata Prefecture, Japan. The field results combined with a series of laboratory soil tests demonstrate that suction governed the variability of habitat environments observed, involving the degree of saturation, density, and hardness of the cross-shore intertidal and supratidal sediments, depending on the severity of the suction-dynamics-induced sediment compaction. While the observed species abundances were consistent with existing theories relating to intertidal and supratidal species, the observed magnitudes of suction were responsible for the distribution limits of the amphipods Haustorioides japonicus and Talorchestia brito and the isopod Excirolana chiltoni manifested consistently throughout the different beaches. The results of controlled laboratory experiments and field tests further revealed three distinctive suction-induced mechanisms, associated with their burrowing and physiology and the stability of the burrows. The novel role of such suction-induced geophysical processes in forming the habitat environment and influencing the species distributions may advance our understanding of sandy beach ecology in intertidal and supratidal zones.

Seasonal effects of rainfall on the shallow pyroclastic deposits of the Campania region (southern Italy)

The shallow deposits of unsaturated pyroclastic soils covering the slopes in the Campania region (southern Italy) are systematically affected by various rainfall-induced slope instabilities. The type and triggering of these instabilities depend on several factors, among which in situ soil suction—as an initial condition—and rainfall—as a boundary condition—play a fundamental role. Based on the available database—which includes a comprehensive catalogue of historical data, in situ soil suction measurements and soil laboratory tests along with the results of geomechanical analyses—this paper discusses the relationships among in situ soil suction and rainfall conditions and induced slope instability types. The goal is to reach a better understanding of past events and gain further insight into the analysis and forecasting of future events. In particular, the paper outlines how the season strongly affects the spatial distribution and the type of slope instability likely to develop. For example, erosion phenomena essentially occur at the end of the dry season and originate hyperconcentrated flows while first-time shallow slides prevail in the rainy season and later propagate as debris flows or as debris avalanches.

Measured effects on engineering properties of clayey subgrade using lime–Homra stabiliser

The engineering properties of clayey subgrade soils may need to be improved for suitability in construction using appropriate stabilisation methods. Stabilisation of pavement subgrade soils has traditionally relied on treatment with lime, cement and sometimes special additives, which are regarded as waste materials. Alternatively, the Egyptian bricks/ceramic industry generates large amount of calcined-clay waste or crushed clay bricks (known as Homra). In this study, standard laboratory soil tests were conducted to measure changes in the engineering properties of clayey soils when treated with a lime+Homra (L+H) blend. Tests were conducted on untreated control soil samples and on varieties of treated samples with L+H ranging from 1% to 11% for lime and 5% to 15% for Homra. The results showed that the L+H clay samples exhibit low plasticity, swelling, maximum dry density and consolidation settlement. On the other hand, results showed a significant increase in California Bearing Ration, soil cohesion and soil strength. The internal friction angle concerning shear strength parameters is also enhanced. It can be summarised that engineering properties of clayey soils can be enhanced using lime and Homra. This is advantageous for work construction in the civil engineering field.

해양플랜트 설치를 위한 해양물리탐사 기법 제안

Abstract: Recently, while global concern over offshore resources exploration and development is being increased rap-idly, offshore plant industry is highlighted as an industry of high added value. Along with this global trend, domes-tic concern over offshore plant development is being increased as well. In the overseas case, a marine geotechnical survey guideline for confirming characteristics of seabed sediments is available at the time of installation of offshore plant but such guideline is not available in our country. In this study, survey techniques fit for domestic marine en-vironment was applied according to overseas guideline at southern coastal area, Korea. Among the marine geo-physical survey techniques being proposed abroad, magnetic survey and seabed photograph were excluded. However, highly reliable data analysis was enabled for marine geophysical survey, which includes in-situ coring investigation and laboratory soil test. In addition, continuous ocean current survey was included to find scour potential due to the current around the offshore plant. Although coring depth is not so deep, we predicted geological structure through the analysis of amplitude features of seismic data. Characteristics of seabed sediments cold be obtained regionally and directly through combined analysis of marine geophysical survey data and coring data.

Comparison of plant nutrient and environmental soil tests to predict Pb in urban soils

Most urban soils are not tested for Pb because of the high costs associated with sampling and laboratory analysis of soil contaminants. However, soil testing for plant nutrients is inexpensive and routinely performed for agricultural soils used for food production. The objectives of this study are to determine the ability of 1M HNO3, Mehlich 3, and Modified Morgan soil tests to predict total Pb and other contaminants in urban soils. Total Pb was determined from 65 urban vacant residential lots being considered for urban gardens and food production in Cleveland, OH. Extractable Pb was determined using common soil nutrient test methods Mehlich 3 and Modified Morgan extraction, and a 1M HNO3 extraction. Significant linear regressions between total Pb and Mehlich 3 (r2=0.83), 1M HNO3 (r2=0.92), and Modified Morgan (r2=0.77) in study soils were found. Most commercial and university soil testing labs use Mehlich 3 which could be implemented as a screening tool for soil Pb, Cu, and Zn. The Mehlich 3 soil test is widely used and is relatively inexpensive (<$15). Our results show that total Pb can be conservatively estimated by the following equation Total Pb (mgkg−1)=Mehlich 3 Pb (mgkg−1)×2.

BHE logging and cement hydration heat analyses for the determination of thermo-physical parameters

To design an efficient and cost effective borehole heat exchanger (BHE), it is necessary to know the thermo-physical parameters of the subsurface at the project location. The quality management and the examination of existing BHEs are becoming particularly important with the increasing application of ground coupled heat pumps. The analysis of data collected from a BHE-logger (temperature-depth-measuring system) in a water-filled BHE allowed several geothermal parameters to be determined. A comparison of measurements obtained from the BHE-logs, geothermal response tests and laboratory soil tests indicated a good correlation. In addition to detecting hydraulic short circuits due to defects in the pipe system or backfill material, being relatively quick and easy to use, the BHE-logger can be a valuable tool in the long-term monitoring system and quality control of BHEs.

Estimating subsoil resistance to nitrate leaching from easily measurable pedological properties

Leaching of nitrate (NO3-) can increase the groundwater concentration of this anion and reduce the agronomical effectiveness of nitrogen fertilizers. The main soil property inversely related to NO3- leaching is the anion exchange capacity (AEC), whose determination is however too time-consuming for being carried out in soil testing laboratories. For this reason, this study evaluated if more easily measurable soil properties could be used to estimate the resistance of subsoils to NO3- leaching. Samples from the subsurface layer (20-40 cm) of 24 representative soils of São Paulo State were characterized for particle-size distribution and for chemical and electrochemical properties. The subsoil content of adsorbed NO3- was calculated from the difference between the NO3- contents extracted with 1 mol L-1 KCl and with water; furthermore, NO3- leaching was studied in miscible displacement experiments. The results of both adsorption and leaching experiments were consistent with the well-known role exerted by AEC on the nitrate behavior in weathered soils. Multiple regression analysis indicated that in subsoils with (i) low values of remaining phosphorus (Prem), (ii) low soil pH values measured in water (pH H2O), and (iii) high pH values measured in 1 moL L-1 KCl (pH KCl), the amounts of surface positive charges tend to be greater. For this reason, NO3- leaching tends to be slower in these subsoils, even under saturated flow condition.

Manual of Soil Laboratory Testing—Volume 1: Soil Classification and Compaction Tests, 3rd editionManual of Soil Laboratory Testing—Volume 1: Soil Classification and Compaction Tests, 3rd edition, by HeadK. H.. Whittles Publishing, Caithness, UK, 2006 (reprinted 2009), £90.00, hardback, c . 416pp., ISBN: 1-904445-36-5

Manual of Soil Laboratory Testing—Volume 1: Soil Classification and Compaction Tests, 3rd editionManual of Soil Laboratory Testing—Volume 1: Soil Classification and Compaction Tests, 3rd edition, by HeadK. H.. Whittles Publishing, Caithness, UK, 2006 (reprinted 2009), £90.00, hardback, <i>c</i> . 416pp., ISBN: 1-904445-36-5

A Comparison of Screening Tests for Soil Pb

Soil has been identified as a significant source of lead (Pb) exposure for both children and adults. Therefore, identifying possibly contaminated soils by soil testing is important to protect public health. Soil Pb test results are usually reported as total Pb (mg kg(-1)), carried out using a concentrated nitric acid digestion procedure by hot plate (EPA method 3050) or microwave (EPA method 3051) followed by inductively coupled plasma atomic emission spectrometry to determine total Pb in the digest. However, this procedure is both time-consuming and expensive, sometimes costing homeowners and gardeners over $50 per sample. To make soil Pb testing more economically accessible to homeowners and gardeners, several university soil-testing laboratories offer less expensive screening tests designed to estimate total soil Pb. The first objective of this study was to compare three commonly used screening tests, modified Morgan (MM), Mehlich 3 (M3), and 1 M nitric acid (HNO(3)), to the standard total Pb testing method (EPA method 3051) to find which extractant is the most reliable predictor of total Pb. The second objective was to investigate the effect that different degrees of soil grinding have on the total Pb test and the extracted Pb concentration measured from the 1 M HNO(3) test. Results indicate that the strongest predictor of total Pb is 1 M HNO(3), followed by M3, and MM, and that thorough grinding is necessary if using less than five grams of soil in a Pb test, in order to adequately homogenize Pb-contaminated samples and achieve acceptable testing reproducibility.

Interlaboratory and Intralaboratory Testing of Soil Sulfate Analysis in Mollisols of the Pampas

Sulfur (S) deficiencies in grain and forage crops have been detected in many agricultural regions of the world, but soil tests are not commonly used as the basis for S fertilizer recommendation programs. Errors of measurements of soil sulfate were determined to assess whether the variation among and within soil-testing laboratories could be a factor that prevent the adoption of soil testing to assess soil sulfate availability. Subsamples of 10 selected soils (Mollisols) from the Pampas (Argentina) were sent in two batches to five soil-testing laboratories. Laboratories were unaware of the existence of subsamples and performed routine sulfate analysis as if these soils came from 60 different fields. Soil sulfate ranged from 3.3 to 20.6 mg kg−1. One laboratory reported sulfate values greater than the other ones, having a mean bias of 4.1 mg kg−1 S sulfate (SO4). The other four laboratories reported similar sulfate values when soils had low sulfate availability (less than 10 mg S kg−1), even when they used different extractants. Considering only these four laboratories, average interlaboratory coefficients of variations ranged from 6 to 24% for the 10 soils. Within-laboratory mean coefficients of variation (CVs) ranged from 12 to 22%. However, mean absolute errors of all laboratories were less than 1.2 mg kg−1 S-SO4. Two laboratories reported different sulfate values for the two batches of shipment (an average difference of 4.7 and 3.8 mg kg−1 of S-SO4). Laboratories using different extractants obtained similar results, suggesting that using the same extractant is not a prerequisite to standardize laboratory results in these soils. Differences between laboratories in our study were smaller than in other interlaboratory comparisons for soil sulfate. These differences could be easily detected and corrected if laboratories participate in an interlaboratory control system. The observed low mean absolute errors suggested that, in general, all laboratories achieve acceptable precision when evaluating within the same batch of determinations. Differences between batches of shipment (within laboratory error) stressed the importance of using reference material for internal quality control.

Can a Labile Carbon Test be Used to Predict Crop Responses to Improve Soil Organic Matter Management?

Permanganate (KMnO4) oxidizable C (POXC), an estimate of labile soil C, was evaluated for use as a soil test to identify soils that may respond positively to soil organic matter (SOM) management. We hypothesized that soils lower in POXC would be more likely than soils higher in POXC to show increased crop productivity in response to practices that increase SOM. At four sites, paired fields of the same soil but contrasting management history (cropping vs. sod) were studied. Fields with sod history tested higher in total organic C (TOC) and POXC than fields with cropped history. Permanganate‐oxidizable C was strongly related to TOC (r = 0.94). We examined crop stover, grain, and biomass responses to two cover crop treatments within each field: winter rye (Secale cereale L.) or no rye. After at least 1 yr of treatment, there was a significant negative correlation between relative stover response to rye and POXC (r = –0.60) at sites with finer textured soils. After at least 2 yr of treatment, crop responses to rye showed a significant negative correlation with POXC and TOC. The strongest relationships to POXC occurred in the stover response at two sites with finer textured soils (Keedysville: r = –0.74; Holtwood: r = –0.84). Permanganate‐oxidizable C was comparable to TOC at predicting crop responses to rye. These results suggest that POXC may be a useful test for identifying soils where improved SOM management is likely to improve productivity. The rapid, simple POXC methodology enables on‐site or laboratory soil testing.