Higher Soil Organic Matter Content Research Articles

Comparison of alternative farming systems. III. Soil aggregate stability

AbstractQuantitative studies are needed to separate the real and supposed benefits of alternative farming practices. Our objective was to learn how conventional and alternative practices on adjacent farms in central Iowa affected the water stability of soil aggregates. We collected samples of Clarion loam (fine-loamy, mixed, mesic Typic Hapludoll) from adjacent 16 ha fields in fall 1990 and spring 1991. Aggregate stability was determined by wet-sieving and by measuring turbidity of soil-water suspensions. The combined effects of alternative practices resulted in greater water stability of soil aggregates, higher soil organic matter content, and lower bulk density compared with conventional practices. The components of the alternative system that were mainly responsible for these differences were: rotations that included oat and hay crops; ridge-tillage; and additions of 45 Mg/ha of a mixture of animal manure and municipal sludge during the first 3 years of each 5 year rotation. The more favorable soil physical conditions, shown by increased water stability of soil aggregates, presumably will improve soil water regimes and reduce long-term soil erosion losses from the alternatively managed fields.

Automatic, real‐time monitoring of soil moisture in a remote field area with time domain reflectometry

A multiplexing time domain reflectoinetry (TDR) system for real‐time monitoring of volumetric soil moisture content was developed. The system was tested at a remote field site in the Hubbard Brook Experimental Forest in New Hampshire. The average value of soil moisture content in the top 500 mm of soil was measured every 4 hours for 1 year at 12 locations within a 12‐ by 18‐m plot. The system functioned well except when the air temperature dropped below −15°C, which caused the data logger tape recorder to stop. Calibrations run on undisturbed soil cores did not compare well with published curves developed for mineral soils, probably because of high soil organic matter content. The standard error of estimate of soil moisture content, indicated by the calibrations, was 0.02 cm3/cm3. The standard deviation of repeated moisture content measurements made in the field was 0.003 cm3/cm3. The effect of cable length on the TDR signal was investigated. It was found that long cables tend to attenuate the signal, ultimately making the measurement impractical. However, cable length had little effect on the calibration up to a length of 27 m. The coefficient of variation of the moisture content measurements taken at any given time ranged from 0.12 to 0.21 during the test period. As predicted by a stochastic analysis of soil moisture flow in heterogeneous soil, the spatial variability of the measurements decreased as average soil moisture increased.

Accumulation of heavy metals from polluted soils by the earthworm, Lumbricus rubellus: Can laboratory exposure of ‘control’ worms reduce biomonitoring problems?

This paper compares the patterns of metal (Pb, Zn, Cd, Cu) accumulation in nine populations of the epigeic earthworm, Lumbricus rubellus, native on metalliferous soils, with the patterns of metal accumulation in batches of L. rubellus sampled from an uncontaminated site and maintained on the nine contaminated soils for 31 days under laboratory conditions. The primary findings were: (1) the Pb, Zn and Cd concentrations in the ‘native’ worms were significantly higher in most cases than in the ‘introduced’ worms; (2) multiple regression analyses indicated that the relationships between tissue and soil metal concentrations were similar for ‘native’ and ‘introduced’ worms; (3) high soil organic matter content reduced the bioavailability of Pb, but low pH increased Pb bioavailability. It was concluded that, although no phenotypic evidence of metal-tolerant ecotypes was obtained, the exposure of earthworms from uncontaminated soils to contaminated soils under laboratory conditions can provide meaningful integrative data concerning metal bioavailability in soils which, for biomonitoring purposes, often present formidable sampling problems.

Persistence of Norflurazon in Five Georgia Soils

Norflurazon [4-chloro-5-(methylamino)-2-(3-(trifluoromethyl)phenyl)-3(2H)-pyridazinone] persistence in five Georgia soils after application to the same plots in 1982 and 1983 was characterized by rapid initial degradation followed by slow loss of the herbicide. The rate of norflurazon loss at each location for each year was not affected by application rate (1.7 or 3.4 kg ai/ha). Relative rates of norflurazon loss were Dothan loamy sand ≥ Greenville sandy clay loam ≥ Rome gravelly clay loam = Appling coarse sanely loam > Bradson clay loam. The rate of dissipation was slower in 1983 than 1982 in the Greenville and Appling soils. Cool and/or dry environmental conditions combined with higher soil organic matter content caused slower herbicide loss. Norflurazon residue 1 yr after treatment in all soils was greater in 1983 than in 1982. Significant injury to grain sorghum [Sorghum bicolor(L.) Moench. ‘BR 64’) was observed in the spring of 1984 at all locations in all plots that were treated with norflurazon for the previous two seasons. The degree of injury corresponded to the concentration of norflurazon detected at that sampling date. Leaching did not appear to be an important method of norflurazon loss.

Application of Sewage Sludge to Soils High in Organic Matter

AbstractIn a greenhouse study corn (Zea mays L.) was grown in four soils (1.4, 19, 38, and 72% organic matter) that received sewage sludge from Philadelphia, Pa., (PS) at rates to supply 0, 2, 4, and 8 kg Cd/ha. Corn and soybeans (Glycine max. L.) were grown in 1.4 and 19% organic matter (OM) soils that received sewage sludge from Wilmington, N.C., (WS) at rates to supply 0, 2, 4, and 6 kg Cd/ha. The pH of the 1.4% OM soil was adjusted to 6.5 with CaCO3. The higher OM‐content soils received recommended rates of CaCO3 to increase the pH to 5.0–5.5, the desired range for crop production on these soils. Actual resulting pH values were 5.5, 4.9, and 4.6 for the 19, 38, and 72% OM soils respectively.Corn yields were depressed by PS but enhanced by WS. Soybean yield was enhanced by WS on the 19% OM soil but depressed on the 1.4% OM soils. Both sludges caused increases in concentrations of Cd, Cu, and Zn in the plant tissue, but concentrations were not high enough to be responsible for the observed yield depressions. The PS was more effective in raising Cd and Zn concentrations in plant tissues than was WS. The type of soil had a varying effect on metal concentrations in the plants. The expected reduction in heavy metal uptake with higher soil OM content was confounded by the low pH of the soils with high OM content. The large quantity of OM added via WS masked the effect of soil OM.Since the bulk densities of the soils varied from 0.45 to 1.35 g/cm3, regression equations describing Cd concentration in corn stover as a function of OM and cation exchange capacity (CEC) were more precise when OM and CEC were expressed on a volume basis and when OM was determined by a procedure designed to estimate humus rather than total oxidizable OM.

Organic Carbon and Oxygen Demand Relationships in Stormflow from Southern Pine Watersheds1

Total organic carbon (TOC) and chemical oxygen demand (COD) of stormflow from five undisturbed pine watersheds (1.5 to 2.8 ha) in northern Mississippi were determined during the 1976, 1977, and 1978 water years on both the solution and suspended sediment phases. Stormflow was measured in 0.9-m H-flumes and sampled with a Coshocton wheel. For the five watersheds, discharge-weighted solution TOC concentrations ranged from 6 to 16 mg/liter and solution COD concentrations ranged from 20 to 45 mg/liter. Watersheds with higher soil organic matter contents had higher solution and sediment TOC and COD concentrations in stormflow. Suspended sediment TOC concentrations indicated enrichment ratios (TOC sediment ÷ TOC soil) of 3.5 to 10.1 relative to their respective watershed soils. Presumably this TOC enrichment is related to an organo-clay enrichment of the suspended sediments. The discharge-weighted five-day biochemical oxygen demand in stormflow was low, ranging from 6 to 11 mg O2/liter. Mean solution plus sediment TOC yields ranged from 7.8 to 28.4 kg ha-1 year-1 of which 60 to 77% was transported vi the solution phase; the rest, in association with the sediment. Thus, the solution phase dominated the transport of TOC and COD from these watersheds. Rainfall input of TOC to the watersheds ranged from 38 to 49 kg ha-1 year-1 which exceeded solution plus sediment TOC yields.

Cumulative Effects of Nitrogen, Phosphorus, and Potassium Fertilizer Additions on Soil Respiration, pH, and Organic Matter Content

AbstractCumulative effects of annual additions of NH4NO3 (111 kg/ha N), treble superphosphate (55 kg/ha P), and KCl (111 kg/ha K) on aspen (Populus tremuloides Michx.) soil respiration, pH, and soil organic matter content were examined. Total fertilizer additions from fall 1969 through spring 1975 were 777 kg/ha N and K and 385 kg/ha P.The main effect of N and P additions was to increase soil biological activity by up to 42% and 33%, respectively, with the greatest increases occurring at the 15‐ to 30‐cm soil depth. For K, a 21% reduction in soil biological activity occurred at 0‐ to 15‐cm, while a 20% increase was found at 15‐ to 30‐cm. Fertilization with N and P increased but K showed no effect on surface soil organic matter content. Subsurface soil (15‐ to 30‐cm) organic matter content was not affected by any treatment. Higher soil organic matter content probably resulted largely from greater aspen growth response to N. Increased soil biological activity was attributed to a combination of increased soil organic matter content and improved levels of soil N and P.Treatment with N, K, or N + K reduced soil pH, possibly because of microbial nitrification of NH4+ associated with uptake by aspen of NH4+ and K+ with replacement of H+ in the soil.

Fractionation, Characterization and Speciation of Lead in the Industrially Polluted Soils of Tejgaon Area of Bangladesh and Lead Pollution of Associated Plants and Water

The Tejgaon industrial area is located within the Dhaka Municipality area and about 5 km north of the city centre. At Tejgaon soil pH was around neutrality (mean 6.73) although the minimum value was 5.3 and the maximum 7.6. High buffering capacity resulting from high soil organic matter content (4.87-11.55%) probably influenced soil pH to a neutral value. Electrical conductivity (EC) (25-551 μS), organic matter (OM) (4.87-11.55%) and nitrogen (N) contents were also influenced by the industrial wastes and effluents of the factories. The average Pb concentrations (mg/kg) in different soil fractions were 7.80, 21.85, 56.15 and 130.29 and 11.42, 20.27, 40.33 and 95.08 in water-soluble, NH4OAc extractable, DTPA ( Dietheline-Triamine-Penta-Acetic acid) extractable and total fractions during dry (January) and rainy seasons (September) respectively. Comparing 1st (rainy season) and 2nd (dry season) sampling data, Pb concentrations in different soil fractions were higher in the 2nd sampling data. Concentration of total Pb in soils during 1st sampling were found above the natural background level with few exceptions. Only 4% of total Pb (=20 mg kg-1) samples were in the normal range during wet season. Lead concentration in the group of tolerable level was 58% (>20-<=100 mg kg-1) and 38% (>=100 mg kg-1) were found in the group of in excess of tolerable level during 1st sampling. On the other hand 62.5% (>=100 mg kg-1) were found in the group of in excess of tolerable level (0.01 mg kg-1 Pb) during dry season. In case of water samples, total Pb concentration in the rainy season, all samples were found in the group of in excess of tolerable level during 1st sampling. Plant samples were found to contain untolerable total Pb (>20 mg kg-1) during rainy and dry seasons, respectively. Key words: Speciation; Tejgaon soil; Industrial area; Lead. DOI: http://dx.doi.org/10.3329/bjsir.v46i3.9032 BJSIR 2011; 46(3): 277-290

Speciation Analysis of Nickel in the Soils of Tejgaon Industrial Area of Bangladesh

The main focus of the study is Tejgaon industrial area which is located within the Dhaka City Corporation and about 5 km north of the city centre. The industries around the study area like battery, chemical manufacturing, electrical and electronic, metal finishing, mining, paint and dye, textiles, pharmaceuticals, pesticides, etc, discharge heavy metals like Ni with their effluents and wastes. At Tejgaon soil the minimum pH value was 5.3 and the maximum 7.6 (at 26°C). High buffering capacity resulting from high soil organic matter content (4.87-11.55%) probably influenced soil pH. Electrical conductivity (EC) (25-551 μS/cm) and organic matter (OM) (4.87-11.55%) contents were also influenced by the industrial wastes and effluents of the factories. In the wet season, the average Ni concentration in different soil fractions was 1.69, 4.16, 13.21 and 93.12 mg kg-1 in water-soluble, NH4OAc extractable, DTPAextractable and total fractions respectively. Comparing wet season and dry season sampling data, total Ni concentrations in different locations were higher in the dry season and the mean concentration of total Ni was 223.89 mg kg-1, which was more than 4 times higher than the tolerable limit. Concentrations of total Ni in different locations during wet season were found above the natural background level with few exceptions. Ni concentration in the group of tolerable level was 21% (>022-=50 mg kg-1) and 75% (=50 mg kg-1) soil samples were found in the group of in excess of tolerable level during wet season. During dry season, 11% of Ni (=50 mg kg-1) samples were in the normal range and 89% (>50 mg kg-1) soil samples were found in the group of in excess of tolerable level. Ni concentration during dry season samples in different extraction i.e in NH4OAc extractable, DTPA extractable and in total fraction was found to decrease with distance away from the disposal point source due to dilution of the effluent and water. The decreasing tendency with distance indicates the accumulation of metals by the industrial operations. Key words: Speciation,Tejgaon soil, Industrial area, Nickel. doi: 10.3329/bjsir.v44i1.2717 Bangladesh J. Sci. Ind. Res. 44(1), 87-108, 2009