CaCO3 Treatments Research Articles

Valorization of red macroalgae biomass via hydrothermal liquefaction using homogeneous catalysts

Hydrothermal liquefaction of red macroalgae species, Kappaphycus alvarezii (KA) and Eucheuma denticulatum (ED), was performed at 350 °C in the presence of 5 wt% neutral and alkali catalysts like Na2CO3, K2CO3, CaCO3, Na2SO4, NaOH, and KOH. The maximum bio-crude yield of 26.7 wt% and 18.5 wt%, on a dry ash-free basis, was obtained from Na2CO3 treatment of KA and KOH treatment of ED, respectively. The bio-crude from both feedstocks mainly consisted of cyclic oxygenates, whose selectivities were maximum in K2CO3 and CaCO3 treatments. The calorific value of the bio-crude was 38.5 MJ/kg from KA and 30.8 MJ/kg from ED, while that of biochars was 20–24 MJ/kg. A high degree of deoxygenation (64.2%) was observed in bio-crude produced from Na2SO4 treatment of KA biomass. Salts of Cl–, SO42– and K+ constituted the major inorganic portion of the aqueous phase. Maximum energy recovery (99%) was observed from the Na2CO3 treatment of ED.

Attenuation of negative effects of saline stress in wheat plant by chitosan and calcium carbonate

BackgroundChitosan and Ca+ are natural signal molecules that can be used in agriculture as biostimulants and elicitors. They enhance different physiological responses and mitigate the negative effects of salinity. So, this investigation was done to study the effect of soaking wheat grains in chitosan and CaCO3 (20 and 40 mg/L) on alleviating the adverse effect of salinity stress (0.0 and 5000 mg/L) on growth, some biochemical and physiological and yields of wheat plant.ResultsShoot length (cm), leaves no/tiller, shoot dry weight (g), root fresh weight (g) and root dry weight (g) were significantly decreased as a result of salt stress. Soaking wheat grains in Chitosan or CaCO3 significantly promoted plant growth under normal and stressed conditions. Irrigation of wheat plants with saline water significantly decreased photosynthetic pigments (Chlo-a, Chlo-b, carotenoids and total pigments) in addition to Chlo-a/Chlo-b ratio, indole acetic acid content in the plant leaves. Meanwhile, saline water significantly increased phenolics, total soluble sugars (TSS) and proline content. H2O2 and lipid peroxidation expressed by malondialdehyde (MDA) content clearly showed significant increases under salinity stress compared with untreated control. Soaking wheat grains in chitosan or CaCO3 before sawing significantly increased the accumulation of H2O2 and MDA in the leaves of wheat plants. Treatment of wheat grains with chitosan or CaCO3 significantly promoted the activity of various antioxidant enzymes (SOD and POX) as compared to the control. CAT activity was significantly decreased as a result of chitosan or CaCO3 treatments. The highest CAT activity was recorded in plants irrigated with 5000 mg/L saline water followed by control plants which recoded 36.40 and 24.82 U/min/g FW, respectively. On the other hand, irrigation of wheat plants with 5000 mg/L saline water significantly decreased spike length (cm), spikelets no/spike, grains wt/plant (g), 1000-grains wt (g), yield and biomass/plant (g) as well as, carbohydrate % and protein % compared with the control. However, treating wheat plants either with Chitosan or calcium carbonate resulted in obvious significant increases in carbohydrates and protein contents, especially in plants treated with 40 mg/L chitosan followed by 40 mg/L calcium carbonate. Soaking wheat grains in chitosan, especially at 40 mg/L, exhibited the strongest scavenging potential (2,2-diphenyl-1-picryl-hydrazyl-hydrate assay (DPPH%) followed by treatment with 40 mg/L CaCO3.ConclusionIn conclusion, the used treatment enhanced the protective parameters such as antioxidant enzymes, total phenols and free radical scavengers and consequently helped the plants to decrease lipid peroxidation, increased their tolerance and improved yield and spike quality. Application of 40 mg/L chitosan recorded the highest increment in the scavenging ability of the natural antioxidants of the plant extract toward the stable free radical DPPH.

Investigation of differential levels of phosphorus fixation in dolomite and calcium carbonate amended red soil.

The pH adjustment of acidic red soils with lime materials is beneficial for the reduction of phosphorus (P) fixation. However, the reasons for varying levels of P activation after adding different lime materials have not been fully investigated. Therefore, this study examined changes in soil labile P and P forms after phosphate application to calcium carbonate (CaCO3 ) and dolomite amended red soil during a 120-day incubation period. Also change of P sorption properties in the amended soil samples from day 120 were examined through a sorption-desorption experiment. The increase of soil H2 O-P and NaHCO3 -P in the CaCO3 and dolomite amended soil treatments was mainly ascribed to the decline of the NaOH-P. However, when compared with the control treatment after 120 days, soil Olsen-P significantly increased by 34% and 66% in the CaCO3 and dolomite treatments. The Hedley P fractionation results demonstrated that the CaCO3 application caused a notable increase of HCl-P (stable Ca-P), which was 88.4% higher than that in the dolomite treatment. However, the formation of stable P was strongly suppressed in the dolomite treatment due to the presence of magnesium (Mg), which was identified by the negative relationship between M3-Mg and HCl-P. In line with these findings, P sorption-desorption work showed weaker P binding energy in the dolomite treatment relative to the CaCO3 treatment. In terms of increasing P availability in red soil, this study suggests that dolomite should be used to substitute CaCO3 in order to reduce the soil P fixation. © 2021 Society of Chemical Industry.

Treatment with nano-silica and bacteria to restore the reduced bond strength between concrete and repair mortar caused by aggressive removal techniques

Removal of degraded concrete during repair activities might have a detrimental impact on the bond strength between the concrete and the repair mortar. This research aims to improve the bonding strength in case aggressive removal techniques were used, by the singular and combined application of bacterially induced CaCO3 and colloidal nano-silica (CNS) treatments. Water jetting (WJ) and jackhammering (JH) were compared and the treatments were performed on the substrates prepared with the technique causing the lowest bonding. Pull-off test results on crushed stone concrete (CC) substrates showed that JH substrates possessed the lowest bond strength compared to WJ and unprepared substrates. To assure that reported results are reproducible, pull-off tests were also performed on another type of concrete, gravel concrete (GC). The results showed that in both cases JH-substrates achieved a lower bond strength than unprepared- and WJ-substrates. The reduced bond strength by JH was restored by the CNS treatment irrespective of the concrete composition. Regarding the biodeposition treatment, the spraying technique showed to be superior to the pouring technique. Microstructural analysis confirmed the survival of the bacteria and carbonate precipitation. Porosity of the prepared substrate surfaces was studied by capillary absorption, water absorption (including the gravity effect) and vacuum absorption tests. The reduction in the initial water uptake of CNS-treated samples was evidenced by the precipitation of the silica gel at the superficial layer of the substrate. The efficacy of Energy Dispersive X-Ray Analysis (EDX) to recognize the interlayer of layered composites with a monolithic structure was observed.

Lipopeptide production by Bacillus atrophaeus strain B44 and its biocontrol efficacy against cotton rhizoctoniosis.

An assay was conducted to show the comparisons the effects of nine metal ions on antagonistic metabolites (lipopeptides, siderophores and gibberellins) by Bacillus atrophaeus strain B44 using well-diffusion assays, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis, chrome azurol S plus mannitol salt agar (CAS-MSA) tests, and reversed-phase high-performance liquid chromatography (RP-HPLC) analysis. This assay is also designed to demonstrate the biocontrol efficacy of B44 against cotton rhizoctoniosis using pot culture tests. Both the lipopeptide yield and the antimicrobial activity of B44 increase with the MnSO4, MgSO4, CaCO3, and CuSO4 treatments and either have no effect or decreased lipopeptide yield and antimicrobial activity with the FeSO4, K2HPO4, KCl, KH2PO4 and ZnSO4 treatments. The medium containing MgSO4 has no significant effect on either the lipopeptide yield or antimicrobial activity. MALDI-TOF-MS analysis shows a broad range of m/z peaks, indicating that strain B44 produces a complex mixture of iturin, surfactin, and fengycin lipopeptides. Gibberellin production by strain B44 varies greatly depending on the culture medium, and the siderophore production is not significantly affected by the culture medium. Pot tests show that lipopeptide production affects the disease control efficacy of strain B44. The biocontrol efficacy of B. atrophaeus strain B44 is related to the lipopeptide yield. Moreover, B. atrophaeus strain B44 significantly increases the size of cotton seedlings, which is related to the GA3 concentration.

An optimised low‐salinity seawater decolourising method produces decolourised seaweed (Kappaphycuz alvarezii) as semi‐refined carrageenan raw material:

AbstractSemi‐refined carrageenan (SRC) production from decolourised Kappaphycuz alvarezii treated by chemicals (CaCO3) drives the search for ‘greener’ decolourisation methods to sustainably supply cheaper and energy efficient products. Therefore, a decolourisation method of low‐salinity seawater (LSS) (3, 9 and 15 g/L) was investigated to replace CaCO3. In addition, decolourised seaweed colour powder (DSP) and SRC colour, yield, viscosity and gel strength were used to screen the salinity treatments. SRC prepared from LSS (3 g/L) treatment demonstrated similar colour and physical properties to CaCO3 treatments, which indicated low‐salinity seawater (3 g/L) could replace CaCO3 as a decolourising agent. Moreover, purity of SRC (3 g/L salinity) were confirmed by x‐ray diffraction (XRD), scanning electron microscopy‐energy‐dispersive x‐ray (SEM‐EDX), and its functional group by fourier transform infrared (FTIR). In this study, waste seawater from LSS (3 g/L) exhibited radical scavenging properties. This decolourising method could be easily adopted by smallholder seaweed farmers in low‐ and middle‐income countries.

Calcium carbonate alters the functional response of coastal sediments to eutrophication-induced acidification

Coastal ocean acidification research is dominated by laboratory-based studies that cannot necessarily predict real-world ecosystem response given its complexity. We enriched coastal sediments with increasing quantities of organic matter in the field to identify the effects of eutrophication-induced acidification on benthic structure and function, and assess whether biogenic calcium carbonate (CaCO3) would alter the response. Along the eutrophication gradient we observed declines in macrofauna biodiversity and impaired benthic net primary productivity and sediment nutrient cycling. CaCO3 addition did not alter the macrofauna community response, but significantly dampened negative effects on function (e.g. net autotrophy occurred at higher levels of organic matter enrichment in +CaCO3 treatments than −CaCO3 (1400 vs 950 g dw m−2)). By identifying the links between eutrophication, sediment biogeochemistry and benthic ecosystem structure and function in situ, our study represents a crucial step forward in understanding the ecological effects of coastal acidification and the role of biogenic CaCO3 in moderating responses.

Role of Foliar Applications by some Safety Compounds and Shading in Alleviating the Harmful Impacts of High Temperature on Tomato

In Egypt, a large number of tomato varieties are grown but most of them lost their potential mainly because of the biotic and abiotic factors. Among these factors, heat stress that is one of the most important determinants of the continuity of the production in the late summer period. The aim of the current study was to assay the role of some treatments in lessening the harmful impacts of high temperatures on production of two commercial hyrids Alisa F1 and 888 hybrid. The study was elaborated in the open field at El-Baramoun farm, Mansoura Horticulture Research Station, Dakahlia governorate during two successive late summer seasons of 2014 and 2015. The experimental design was in split plot included six treatments i.e., naphthaline acetic acid (NAA) at 2.5 ppm, Purshade (CaCO3) 1%, Kaoline (Aluminum silicate) 2.5% as foliar spray and intercropping with maize through two levels of shading; shade 2 (intercropping with maize at two meters apart at the same side of ridge planted with tomato; shade 3 (intercropping at three meters apart at the same side of ridge planted with tomato). Significant differences were observed between Alissa F1 and 888 hybrid tomato hybrids for the majority of studied traits. In general, the mean performance of 888 hybrid grown under high temperature was better and more tolerant than Alissa F1. In regard to effect of the treatments, both treatments of shade 2 and NAA gave the highest plant height without significant differences between them. Furthermore, NAA at 2.5 ppm gave the great number of branches per plant over the two seasons. In addition, expressive increase in the leaf area was recorded for all treatments in the second season comparing with the first one, however, the shade 3 treatment gave the highest leaf area over the two seasons estimated by 730.87 cm and 772.8 cm, respectively. The treatment of NAA caused a high and significant increase in the total chlorophyll content over the control during the two seasons estimated by 1.15 and 1.72 mg/g, respectively followed by Kaoline treatment. In contrast, a great accumulation of dry weight was observed with the shade 3 treatment that gave 30.03 % and 30.22%, for the first and second season, respectively followed by NAA treatment. Kaoline caused a significant increase in TSS % compared with the control. High vitamin C content was recorded by the NAA treatment with significant differences comparing with the control. Concerning fruit firmness, shade 3 has a significant effect on firmness over the two seasons that estimated by 30.55 and 30.98 inch/cm2, for the first and second season, respectively followed by Kaoline and CaCO3 treatments. In addition, the foliar application by NAA increased significantly fruit set % that estimated by 13.10 % and 8.83 % for 888 hybrid and Alissa F1, respectively over the control. Concerning the total fruit yield, the shade 3 treatment recorded an increase estimated by 10.45 and 10.68 ton/fed over the control for 888 hybrid and Alissa F1, respectively as a mean performance of the two years followed by NAA treatment. According to the previous results, it can recommended under high temperature spraying tomato plants by NAA at 2.5 ppm combined with intercropping with maize at three meters apart at the same side of ridge planted with tomato which enhanced different vegetative growth parameters as well as the quantity and quality of fruit yield.

Early-stage changes in chemical phosphorus speciation induced by liming deforested soils

A hypothesis of whether an increase in Ca2+ due to liming acid soils causes an increase in Ca-phosphates with a concomitant decrease in Al- and Fe-phosphates was tested on a relatively short-term time frame, as observed in the investigations of chemical phosphorus (P) speciation. Soil samples were taken at a deforested site and split into three treatment groups: a control and two CaCO3 treatments (0.1 and 0.4 g CaCO3 in 100 g soil). Each soil was incubated at 25±2°C for 40 days. Inorganic-P was partitioned into three fractions: Fraction-A (Al- and occluded Fe-P), Fraction-B (non-occluded Fe- and adsorbed-P), and Fraction-C (Ca-P). The pH of CaCO3-treated soils decreased right after liming, indicating a probable formation of solid phosphate compounds. Available P in CaCO3-treated soils decreased from 0.67 mg kg-1 to control levels at the end of incubation. Total-P and organic-P of CaCO3-treated soils were virtually the same as those of control soils, while inorganic-P varied. Fraction-A in both CaCO3-treated soils peaked at 10 days of incubation, and then decreased below control levels, while Fraction-B decreased abruptly right after liming, and thereafter gradually decreased. Liming decreased Fraction-C, and caused an increase in Al- and Fe-P due to an increase in exchangeable Al3+ and Fe3+. Our results challenge the hypothesis by showing the unexpected opposite data for Al-, Fe- and Ca-P compounds at least in the early stage of equilibrium disturbances due to liming an acidic soil.

Savrun Ispanak (Spinacia oleracea L.) Çeşidinin Bazı Abiyotik Stres Faktörlerine Tepkisi

Bu çalışmada Savrun ıspanak (Spinacea oleracea L.) çeşidinde tuz, ağır metal, kuraklık ve kireç stresine dayanıklık mekanizması araştırılmıştır. Bu amaçla kontrollü koşullarda iklim dobında yetiştirilen, 5-6 yapraklı fideler dört hafta süresince tuz (75, 150 ve 225 mM NaCl), ağır metal (%0,2 FeCl3, NiCl2 ve ZnCl2), kurak (%50) ve kireç (%0,2 CaCO3) stres uygulamalarına maruz bırakılmıştır. Çalışma sonucunda Savrun ıspanak çeşidinde klorofil a, b, toplam klorofil ve karotenoit, β-karoten ve likopen içeriği kuraklık ve CaCO3 stres uygulamalarında artış göstermiştir. Toplam çözünür protein ve GuPX tüm stres uygulamalarında, prolin NiCl2, 75 ve 150 mM NaCl uygulamalarında yüksektir. APX aktivitesi 75 mM NaCl ve ZnCl2; CAT 150 mM NaCl ve kuraklık hariç diğer stres uygulamalarda; SOD aktivitesi ise kuraklık, CaCO3 ve 225 mM NaCl stres uygulamalarında yüksek bulunmuştur. MDA içeriği ise FeCl3 hariç diğer uygulamalarda düşük ve H2O2 ise 225 mM NaCl ve kuraklık uygulamasında düşük diğer uygulamalarda yüksektir. Sonuç olarak Savrun ıspanak çeşidinin CaCO3 ve kuraklık uygulamalarına toleransı yüksek, 225 mM NaCl, ZnCl2 ve FeCl3 uygulamalarına ise duyarlığı yüksek bulunmuştur. Çeşidin NiCl2 ve 75 mM NaCl uygulamalarına ise orta derecede toleranslı olduğu tespit edilmiştir. Bununla birlikte strese tolerans parametreleri oldukça değişkenlik göstermiştir.

Application of eggshell waste for the immobilization of cadmium and lead in a contaminated soil

Liming materials have been used to immobilize heavy metals in contaminated soils. However, no studies have evaluated the use of eggshell waste as a source of calcium carbonate (CaCO₃) to immobilize both cadmium (Cd) and lead (Pb) in soils. This study was conducted to evaluate the effectiveness of eggshell waste on the immobilization of Cd and Pb and to determine the metal availability following various single extraction techniques. Incubation experiments were conducted by mixing 0-5% powdered eggshell waste and curing the soil (1,246 mg Pb kg⁻¹ soil and 17 mg Cd kg⁻¹ soil) for 30 days. Five extractants, 0.01 M calcium chloride (CaCl₂), 1 M CaCl₂, 0.1 M hydrochloric acid (HCl), 0.43 M acetic acid (CH₃COOH), and 0.05 M ethylendiaminetetraacetic acid (EDTA), were used to determine the extractability of Cd and Pb following treatments with CaCO₃ and eggshell waste. Generally, the extractability of Cd and Pb in the soils decreased in response to treatments with CaCO₃ and eggshell waste, regardless of extractant. Using CaCl₂ extraction, the lowest Cd concentration was achieved upon both CaCO₃ and eggshell waste treatments, while the lowest Pb concentration was observed using HCl extraction. The highest amount of immobilized Cd and Pb was extracted by CH₃COOH or EDTA in soils treated with CaCO₃ and eggshell waste, indicating that remobilization of Cd and Pb may occur under acidic conditions. Based on the findings obtained, eggshell waste can be used as an alternative to CaCO₃ for the immobilization of heavy metals in soils.

Effects of Nitrogen and Calcium Carbonate on Growth, Rosmarinic Acid Content and Yield of Satureja hortensis L.

Because of the presence of free phenolic acids, especially rosmarinic acid, extracts of Satureja hortensis L.possess antioxidant and antimicrobial activity. The production of rosmarinic acid by plant cells can be modifiedby many factors. In the present study, the changes induced by calcium carbonate and nitrogen application onrosmarinic acid content, plant growth, and yield of S. hortensis cv. Saturn were investigated. Nitrogenfertilization significantly increased plant height, fresh and dry weights of herb as well as rosmarinic acid contentand yield. CaCO3 treatments did not affect rosmarinic acid content or yield, while the fresh and dry weights ofherb were increased by applying 5 t ha-1 CaCO3.

Effect of Phosphate Rocks on Spring Barley Shoot Yield and Phosphorus Uptake in a Pot Trial

The effect of five rock phosphates (from Algeria, Florida, North Carolina, Senegal, and Morocco) and hyperphosphate on the shoot yield, phosphorus (P) concentration, and P uptake of spring barley was studied in a pot experiment on acidic sandy soil (Nyírlugos) and acidic clay loam soil (Ragály), with superphosphate as the standard P source. The effect of adding calcium carbonate (CaCO3) in combination with superphosphate (SSP) was also investigated. Averaged over the whole experiment, the shoot yield of barley was almost twice as high (3.69 g pot−1) on the clay loam soil from Ragály, which was rich in colloids, than on the colloid‐poor sandy soil from Nyírlugos (1.90 g pot−1). The P uptake, however, was only 25% higher (13.0 mg P pot−1) on the clay loam soil, averaged over the whole experiment, than on the sandy soil (10.4 mg P pot−1). This could be attributed to the fact that the P concentration of barley at tillering was almost 0.1% higher on average in the rock phosphate treatments and 0.2–0.3% higher in the SSP and SSP + CaCO3 treatments on the acidic sandy soil. On both soils, diverse P effects were observed in response to rates of 0–100–400–1600 mg total phosphorus pentoxide (P2O5) kg−1 of the different rock phosphates, adjusted on the active agent equivalence principle. The differences between the P effects, in terms of both biomass surplus and P uptake, exhibited a close correlation with the differences in the P solubility of the rock phosphates. On both soils the greatest biomass surplus and P uptake were recorded for the Algerian rock phosphate, which had excellent natural solubility. Hyperphosphate and the rock phosphates from Morocco and North Carolina were also efficient, whereas the other extreme was represented by the rock phosphates from Senegal and Florida, which had low specific surfaces, P solubility, and lime content. The differences between the rock phosphates could also be expressed in terms of relative agronomic efficiency (RAE %), when the effect of the rock phosphate was compared to that of water‐soluble P fertilizer, in the case of SSP. Averaged over the two soils and over the RAE% calculated on the basis of shoot yield or P uptake, the order obtained for the relative agronomic efficiency of the rock phosphates was the same as that observed for the solubility of the rock phosphates in neutral ammonium citrate. On both soils, the loosest correlation between rock phosphate solubility and either the shoot yield of spring barley at tillering or the P uptake was obtained when the P rates were calculated on the basis of total P content, and the closest correlation was obtained when they were calculated on the basis of the P fraction soluble in neutral ammonium citrate. This, together with the ranking of the rock phosphates on the basis of relative agronomic efficiency, suggests that under conditions similar to those of the present experiment, neutral ammonium citrate is the best solvent for determining the relative P solubility of the rock phosphates. When the effects of the various rock phosphates on the P uptake of spring barley were investigated, a close correlation was detected on both soils between differences in P effects and differences in various properties of the rock phosphates (P solubility, specific surface, CaCO3 content).

Amelioration of Cadmium Polluted Paddy Soils by Porous Hydrated Calcium Silicate

Porous hydrated calcium silicate (PS) is a by-product of autoclave light weight concrete and is being used as a silicon fertilizer in Japan. The impacts of this amendment on the yield and cadmium content of rice (Orzya sativa L. var. Kokoromachi), soil pH and the extractability of soil cadmium assessed by 1 M NH4OAc were compared with those of silica gel and CaCO3 by pot experiments. The application of PS at the rate of 2.0% and silica gel at the rate of 1.0% in Andosol and PS at the rate of 0.75% in Alluvial soil significantly increased the grain weight of rice. PS and CaCO3 treatment significantly increased soil pH, decreased the 1 M NH4OAc extractability of cadmium and reduced cadmium content in straw and brown rice in the two soils. However, cadmium content of rice of PS treatments was not significantly different from that of CaCO3 treatments in Andosol, while was significantly lower than that of CaCO3 treatments in Alluvial soil. Soil analysis showed that it was less effective in increasing soil pH and decreasing the extractability of cadmium by 1 M NH4OAc than CaCO3 at the same application rate in Andosol. Soil pH and 1 M NH4OAc extractability of cadmium were not significantly different between 2.0% of PS and CaCO3 treatments in Alluvial soil. The application of silica gel did not improve soil pH nor decrease the extractability of soil cadmium, but resulted in a significant decline of cadmium content in brown rice. These results demonstrate that the supply of silicon together with an increase in soil pH, as obtained by PS application, shows potential to reduce the cadmium content of rice.

Combined Effects on Nitrogen Fertilization and Soil of CaCO3 Contents on Corn Performance in Al-Marj Soil, Libya

A two-year field trial was conducted at Al-Marj Research Center, northeast Libya, during the summers of 1996 and 1997 to examine the effect of nitrogen (N) fertilizers on corn (Zea mays L.) growth in a Libyan soil (fine mixed thermic, Typic Haploxerolls) amended with different calcium carbonate (CaCO3) levels. Two N fertilizer sources (urea and diammonium phosphate, or DAP) were used at three application rates (0, 80, and 160 kg N/ha). The CaCO3 treatments were 1%, 6%, and 12% based on the soil weight of a 15 cm furrow slice. A basal phosphorus (P) dose of 46 kg P2O5/ha as triple superphosphate was applied to all experimental plots before planting. The experimental plots were arranged in a randomized split-split plot design with three replications. The parameters measured included corn grain weight, plant dry-matter content, leaf contents of N, P, potassium (K), calcium (Ca), and magnesium (Mg). The plant dry matter and corn-grain yield were significantly decreased by CaCO3, but were significantly increased by N fertilizer rates. Average grain yield dropped from 8 to 3 Mg/ha at 1% and 12% soil CaCO3 content, respectively. Generally, the N source did not have a significant effect on dry matter or on grain yield. The negative effect of CaCO3 on yield was associated with concomitant significant reduction in leaf N, P, K, and Mg contents, and an increase in Ca content. However, the leaf levels of these nutrients were considered sufficient for corn growth. Therefore, the reduction of leaf-N by CaCO3 in fertilized soils might have been the major cause of corn dry-matter and grain-yield reductions.

Amendment of drilling fluid-affected soils with calcium salts

Land disposal of waste drilling fluid is an environmental concern because of the high salt content and the presence of potential toxic elements. A water-based drilling fluid was tested in a laboratory column study to determine the feasibility of leaching excessive salt without mobilizing chromium (Cr). The drilling fluid-affected two Alfisols with similar mineralogy, acidity, and texture were treated with gypsum (CaSO4 · 2H2O), calcium carbonate (CaCO3), or calcium phosphate (CaHPO4) (0 to 2% of weight). The electrical conductivity (EC) increased and the sodium adsorption ratio (SAR) decreased with increasing Ca-salt concentration. The pH did not vary significantly with the changes in the concentrations of gypsum and calcium phosphate. The pH of the mixtures increased in proportion to the concentration of added calcium carbonate. The hydraulic conductivity increased and the mobility of the soil particles decreased with increasing Ca-salt concentration. The Cr mobility decreased by gypsum and CaCO3 treatments but it increased by calcium phosphate treatment. The soil with a higher content of organic matter and cation exchange capacity (CEC) showed a higher hydraulic conductivity and lower Cr mobility than the other soils at the same levels of the treatment. The results of this study suggest that the amendment of drilling fluid-affected soils with CaCO3 and gypsum can enhance the leaching of excessive salt and reduce the Cr mobility. Among loamy soil, those with a higher CEC and organic matter content are more suitable for land disposal of drilling fluid.

Technical note: using calcium carbonate as an osmolar control treatment for acid-base studies in horses.

The efficacy of using calcium carbonate as an osmolar control treatment for acid-base studies in horses receiving alkalizing compounds was evaluated. Six mares were nasogastrically intubated with isomolar quantities of sodium or calcium as sodium bicarbonate or calcium carbonate or with water during three treatment periods. Doses of the carbonic acid salts were 500 mg/kg sodium bicarbonate mixed with 4 L of distilled water (positive control) and 595 mg/kg calcium carbonate mixed with 2 L of distilled water to yield isoosmolar treatments. Four liters of distilled water served as the negative control. Jugular venous blood samples were drawn before intubation and at hourly intervals for 6 h after intubation. The serum electrolytes Na+ and K+, blood pH, and HCO3- were determined. The sodium bicarbonate treatment increased blood pH and HCO3- (P < 0.01) above both the water and CaCO3 treatments. No differences (P > 0.05) were found between the water and CaCO3 treatments. These data indicate that calcium carbonate may serve as a suitable osmolar control treatment for studying the effects of treatments that affect acid-base status of horses.

Manganese Toxicity in a Hawaiian Oxisol Affected by Soil pH and Organic Amendments

Manganese toxicity is a serious constraint to many crops grown on acid soils in Hawaii. To develop management strategies to deal with the Mn problem, four experiments were conducted. First, to study soil pH effect, a pH gradient from 4.7 (unamended) to 6.0 was established in a high-Mn Oxisol (Wahiawa series), using combinations of Ca(OH)2 (lime) and CaSO4 · 2H2O (gypsum); soybean [Glycine max (L.) Merr. cv. Kahala] was grown as a test crop. Second, effects of Ca, and particularly SO4, on ameliorating Mn toxicity to soybean were subsequently evaluated. Third, soil Mn solubility by organic molecules was studied in the laboratory as a function of chemical structure, pH, and equilibration time. Fourth, soybean responses to green manure and biosolids applied at 5 and 10 g kg−1 to the Wahiawa soil were compared with those of the unamended control and CaCO3 treatments. Manganese concentration in the saturated paste extract of the first experiment increased 100-fold for each pH unit decrease. A combination of gypsum and lime was more effective in correcting Mn toxicity than either amendment alone. Soybean growth was better correlated with leaf Ca/Mn ratio than with leaf Mn concentration. Increased SO4 concentration alleviated Mn toxicity. Organic molecules or ions containing OH-OH in the ortho position or SH groups, such as catechol, tannic acid, and cysteine, were more effective in dissolving soil Mn than molecules or ions not containing these functional groups. Application of green manure and biosolids generally increased Mn toxicity.

Efeito do fluoreto de cálcio e do carbonato de cálcio na composição química da solução percolada de um solo ácido

Durante oito meses, foram estudados, em casa de vegetação, os efeitos da aplicação de CaF2 (p.a.) e de CaCO3 (p.a.) sobre a concentração de Al e de outros elementos químicos na solução percolada de amostras de um solo ácido, coletado na região de Piracicaba, SP. Os valores de pH aumentaram na solução percolada de amostras de solos que receberam tanto CaCO3 como CaF2. Os tratamentos com CaF2 foram mais eficientes na retirada de Al do solo do que os tratamentos com CaCO3. Na testemunha e nos tratamentos com CaCO3, a maior parte do Al estava, respectivamente, na forma livre Al3+ ou formando complexos Al-OH, ao passo que, nos tratamentos com CaF2 , mais de 99,5% do Al estava complexado com o fluoreto.

Separation of Manure Solids from Simulated Flushed Manures by Screening or Sedimentation

Feces and urine were collected separately from individual cows fed corn silage-based (50% of dry matter) diets which were supplemented with distillers dried grains plus solubles or soybean meal to be 14 or 18% crude protein (CP). Fecal samples from 30 cows were screened using wet sieving and vibrating screens (nested in series); sizes were 3.35, 2.00, 1.40, 1.00, and 0.50 mm. Effluent passing the screens contained 60.2% of total solids (TS), 86.3% of nitrogen (N), and 94.3% of phosphorus (P). Solids caught on the five screens (largest to smallest) accounted for the following percentages of materials: 14.6, 9.4, 2.8, 4.3, 8.6% of TS; 5.7, 3.1, 0.8, 1.3, 2.8% of N; 2.2, 1.2, 0.3, 0.6, 1.5% of P. In another study, a 100 g composite sample of urine and feces from each of 44 cows, mixed in proportion to the amount excreted, was diluted to 1 L with water and allowed to settle for 1 h in a graduated cylinder. Supernatant and sediment were separated by decanting. Supernatants were analyzed for N content, sediments for TS content, and these amounts were subtracted from analyzed contents of samples to obtain reciprocal fractions. Overall, the sediment contained 66% of TS and 45% of N. Estimates of sediment amount made at 5, 10, 20, 40, and 60 min by recording best-defined line between supernatant and sediment suggested sedimentation was 89% completed by 5 min. In a second sedimentation study, simulated manure flushwaters (0.5, 1.0, and 1.5% TS) were treated with additives as follows: (1) 0.75 g of CaC03 plus 0.50 mL Fe2(SO4)3 solution/L, (2) 0.75 g of Ca0 plus 0.50 mL Fe2(SO4)3 solution/L, (3) 0.50 mL Fe2(SO4)3 solution/L plus five drops of a commercial polymer, and (4) control (no additives). Precipitates with CaCO3 and CaO treatments contained 92% of the TS, 69% of the N, and 31% of the total potassium (K); the CaO treatment precipitated appreciably more P (93% of total) than other treatments; and treatment with Fe2(SO4)3 plus polymer precipitated the least TS and N. These data indicated a potential to remove more manure solids and N from flushed manure by sedimentation than by screening.