Use of flue gas desulfurization (FGD) by‐product gypsum on alfalfa

Abstract

Subsoil acidity in northeast United States has been associated with decreased yield and decreased water and fertilizer nitrogen (N) utilization by forages. Surface applications of gypsiferious products has been shown to reduce subsoil acidity largely caused by high levels of soluble aluminum (Al). Our objective was to test the effectiveness and safety of using FGD gypsum to increase dry matter (DM) yields of alfalfa (Medicago sativa L.). Four and one‐half, 9, and 18 mt/ha of either commercially available agricultural gypsum or two gypsum by‐products were applied to a Rayne soil (Fine‐loamy, mixed, mesic Typic Hapludult) with a strongly acid subsoil. Agricultural and FGD gypsum increased alfalfa DM yields by as much as 21 and 14%, respectively. Correspondingly, in the subsoil, soluble Al decreased and calcium (Ca) content and Ca:Al ratio increased. Heavy metal concentrations in either the alfalfa or soils were not increased by any treatment. However, S in the alfalfa grown at the highest treatments approached concentrations that are considered to be toxic to grazing animals.     

Sorption of calcium and sulfate by sandy soils from flue‐gas desulfurization gypsum and phosphogypsum

Abstract

Increasing concern on sulfur dioxide (SO₂) pollution has prompted many coal‐fired electric power generating plants to install SO₂ scrubbing units which generate large amounts of flue‐gas desulfurization gypsum (FGDG). This source of gypsum can be an excellent amendment to supply calcium (Ca) and/or sulfate (SO₄) to sandy soils which are deficient in these nutrients. In this study, reactions of FGDG, phosphogypsum (PG), reagent grade calcium sulfate (CaSO₄), and calcium chloride (CaCl₂) were investigated using a Candler fine sand (uncoated, hyperthermic, Typic Quartzipsamment), a typical well‐drained deep sand, and a Pineda fine sand (loamy, siliceous, hyperthermic, Arenic Glossaqualf), a typical shallow poorly drained sand. Concentrations of various water‐soluble elements were similar in FGDG as well as PG, except the latter contained 11 and 15 g/kg phosphate (PO₄) and fluoride (F), respectively, while these ions were undetectable in the former. In batch‐equilibration (4 h) technique using soilrsolution ratio of 1:2, pH of equilibrium solution decreased by 0.2 and 0.8 units, while ionic strength increased by 5‐ and 15‐fold in the Pineda and Candler sand, respectively, when using FGDG or PG solution as compared to using water for equilibration. Sorption of Ca by the two soils varied from 0.56 to 0.71 Cmolc/kg regardless of source of gypsum. As compared to sorption of SO₄, that of Ca was greater by 2.5‐ and 2.6 to 4.3‐fold by the Candler and Pineda sand, respectively. With the exception of SO4 sorption by the Pineda sand, this study demonstrated that the reactions of FGDG with these sandy soils were very similar to those of PG or reagent grade CaSO4. Since much of the past research on agricultural use of gypsum was done using PG and CaSCU, we could conclude that similar response could be expected with use of FGDG.     

Chemical properties of acid soil treated with coal combustion by‐products and leached

Abstract

Application of coal combustion by‐products (CCBs) to acid soils can have beneficial or detrimental effects. A column study was conducted to determine the effects of CCBs on mitigating acid soil properties after leaching with 138 cm deionized water. Columns containing 105 cm acidic Lily soil (Typic Hapludult) had mixed in the top 15 cm the following treatments (g/kg soil): no CCB or limestone (check); dolomitic limestone (lime) at 3.98; high‐calcium sulfate (CaSO₄) flue gas desulfurization (FGD) by‐product (BP) at 15.88; combination of lime+FGD at rates given; high‐CaSO₄ FGD BP enriched with Mg (FGD+Mg) at 15.88; and fluidized bed combustion (FBC) BP at 6.45. After being leached for 39 days, the columns of acid soil treated with high‐CaSO₄ by‐products showed higher subsurface pH, calcium (Ca), and sulfur (S) and lower aluminum (AI) and manganese (Mn). In contrast, the lime alone treatment had little effect on subsurface soil properties. Use of dolomitic limestone to supply magnesium (Mg) in conjunction with the CaSO₄ treatments was more effective than supplementation with Mg(OH)₂, where97% of the added Mg leached from the top layer. Substances leached from the CCBs studied were effective in reducing problems associated with subsurface soil acidity.     

Effects of flue gas desulfurization gypsum by-products on microbial biomass and community structure in alkaline–saline soils

Purpose

For an alkaline?Csaline region in Northwest China, we examined the responses of soil microbial communities to flue gas desulfurization gypsum by-products (FGDB), a new ameliorant for alkaline?Csaline soils. In 2009 and 2010, we collected soils from 0?C20?cm and 20?C40?cm depths along an experimental FGDB gradient (0, 0.74, 1.49, 2.25, and 3.00?kg FGDB m^?2).

Materials and methods

As a measure of microbial community composition and biomass, we analyzed phospholipid fatty acids (PLFAs). We used real-time quantitative polymerase chain reaction (qPCR) to measure abundance of bacterial 16?S rRNA copy numbers. Additionally, physicochemical soil parameters were measured by common laboratory methods.

Results and discussion

Microbial community composition differed along the FGDB gradient; however, the microbial parameters did not follow a linear response. We found that, in 2009, total PLFA concentrations, and concentrations of total bacterial and Gram-negative bacterial PLFAs were slightly higher at intermediate FGDB concentrations. In 2010, total PLFA concentrations, and concentrations of total bacterial, Gram-positive bacterial, Gram-negative bacterial, and fungal PLFAs as well as the fungal:bacterial PLFA ratio were highest at 1.49?kg FGDB m^?2 and 3.00?kg FGDB m^?2. PLFA concentrations often differed between 2009 and 2010; however, the patterns varied across the gradient and across microbial groups. For both years, PLFA concentrations were generally higher at 0?C20?cm depth than at 20?C40?cm depth. Similar results were obtained for the 16?S rRNA copy numbers of bacteria at 0?C20?cm depth. FGDB addition resulted in an increase in soil Ca²⁺ and NO ₃ ^? ?CN and a decrease in pH and electrical conductivity (EC). Shifts in PLFA-based microbial community composition and biomass could partly be explained by pH, soil organic carbon, total nitrogen (TN), soil moisture, EC, inorganic nitrogen, C/N, and Ca²⁺. Indirect effects via shifts in abiotic soil properties, therefore, seem to be an important pathway through which FGDB affect soil microbial communities.

Conclusions

Our results demonstrate that addition of FGDB leads to significant changes in soil physicochemical and microbial parameters. As such, addition of FGDB can have large impacts on the functioning of soil ecosystems, such as carbon and nitrogen cycling processes.     

Acid‐soil‐stress influence on mineral‐ion contents of sorghum leaves and juvenile panicles

Sorghum [Sorghum bicolor (L.) Moench cv RTX430, SC214, SC574, SC599, TAM428, and SC326xSC103] were grown on soils of pH 4.2 or 6.2–6.5. Leaf and nonexserted juvenile panicle tissues were collected at 75 days after planting. Fresh and dry weights were measured and element contents [sulfur (S), phosphorus (P), magnesium (Mg), calcium (Ca), potassium (K), zinc (Zn), iron (Fe), and copper (Cu)] were measured by atomic absorption. Significant cultivar differences in ion concentration (μmol/g dry weight) were found. Juvenile panicles had higher ion concentration (μmol/g dry weight) [S, P, Mg, Ca, K, Zn, and Cu) than leaves. Within leaf tissue, ion concentration (μmol/g dry weight) was correlated with tissue water content (g water/g dry weight).     

Relationship of ryegrass growth to extractable phosphorus in acidic soil amended with phosphate rock,coal combustion by‐product,limestone, and cellulose

Abstract

An improved management of phosphorus (P) is crucial for increasing crop production and improving environmental quality of acid infertile soils. Laboratory analyses and greenhouse experiments were conducted to evaluate effects of phosphate rock (PR), coal combustion by‐product (BP), limestone, and cellulose application on the relationship between soil test P and crop growth in acidic soil. Application of PR, BP, limestone, and cellulose increased soil pH, exchangeable calcium (Ca) and magnesium (Mg), and extractable P, and decreased free aluminum (Al) ion in the acid soil. Addition of BP or limestone increased P availability efficiency [PAE, mg dry matter yield (DMY) of plant per mg soil extractable P by Olsen‐P procedure] and P utilization efficiency (PUE, mg DMY of plant per mg P in the plant). There was significant positive correlation between the PAE and BP rates applied alone (r²=O.979, p<0.01) or with either PR (r²=0.972, p<0.01) or PR plus cellulose (r²=0.985, p<0.01). The PUE of ryegrass was significantly correlated with BP rates alone (r²=O.957, p<0.01) or with either PR (r²=0.906, p<0.01) or PR plus limestone (r²=O.699). The increase in PAE and PUE of ryegrass caused by BP and limestone reflected more plant root growth from increased availability of Ca and Mg and higher soil pH.     

Zinc,copper, and nickel availabilities as determined by soil solution and DTPA extraction of a sludge‐amended soil

Abstract

Extracting sludge‐amended soil with DTPA does not always give a reliable measure of plant‐available heavy metals. The major purpose of this greenhouse pot study was to help explain why. Two anaerobically digested sludges from sewages treated with either Ca(OH)₂or FeCl₃were applied to 3‐kg samples of a Mollic Albaqualf previously limed with Ca(OH)₂rates of 0, 2.5, and 10g/pot that resulted in pHs in the check pots of 5.4, 6.2, or 7.7 after the first harvest. Sludge rates provided 0, 200, 40, 800, and 1600 mg Zn kg^‐1of soil. Two consecutive crops of soybeans (Glycine MaxL.) were grown for 42 d each in the greenhouse. DTPA‐extractable, soil‐solution, and plant concentrations of Cu²⁺, Ni²⁺, and Zn²⁺were measured.

Dry matter yields were depressed due to salt toxicity, while DTPA‐extracted Cu²⁺correlated with plant uptake of Cu²⁺for both sludges. DTPA‐extracted Ni²⁺also correlated with plant Ni²⁺from the Ca(OH)₂‐sludge‐amended soil, although DTPA‐extracted Ni²⁺did not correlate with plant uptake of Ni²⁺from the FeCl₃‐sludge‐amended soil, DTPA‐extracted Zn did not correlate with plant uptake of Zn²⁺from any sludge‐amended soil. Soil‐solution composition correlated with plant uptake of Cu²⁺and Ni²⁺in both sludges; it also correlated with plant uptake of Zn²⁺from FeCl₃‐sludge‐amended soil but not from Ca(OH)₂‐sludge‐amended soil. DTPA extraction probably failed with Ni²⁺and Zn²⁺because of (i) its ineffectiveness at low pH, (ii) the inability of DTPA to buffer each soil extract near pH 7.3, and (iii) increased amounts of soluble chelated micronutrients at higher sludge rates and higher soil pHs. Soil‐solution composition seemed to fail only where micronutrient cations in solution probably were present largely as organic chelates     

Effect of two soil moisture levels and wetting‐drying cycles on manganese release in NaCl‐amended soils

Abstract

Effect of two moisture levels (22.5 and 13.5%, w/w) and wetting‐drying cycles on manganese solubility was studied in NaCl‐amended soil. During 6 d incubation, higher moisture level released 40‐fold more water‐soluble Mn and 60‐fold more NH₄OAc‐exchangeable‐Mn in non‐salinized soil. In NaCl‐treated soil, 50 to over 200% greater soluble and exchangeable Mn was recovered from samples incubated at 22.5% compared to 13.5% water levels. Wetting‐drying cycles significantly (P≤0.05) decreased water‐soluble Mn, which accounted for 50 to 60% increases in the exchange‐able Mn. Since other non‐oxidizing/reducing cations (Ca, Mg, Na, K) also demonstrated similar behavior, it is proposed that in addition to oxidation upon drying and reduction upon wetting, the increases in exchangeable Mn and simultaneous decreases in soluble Mn concentration are due to sorption processes. These results suggest that under field conditions, the insolubility of Mn due to continued wetting‐drying cycles may eventually lead to Mn deficiency in soils low in Mn.     

The nature of humic acid‐apatite interaction products and their availability to plant growth

Abstract

An investigation was conducted to determine the nature of decomposition products resulting from the interaction between humic acid and apatite and assess their availability to plant growth. Interaction analyses were performed by shaking 200 mg apatite with 0 to 800 mg/L HA or FA solutions at pH 5 or 7 for 0 to 12 hr. Phosphorus concentrations were determined in the supernatants by spectrophotometry. The nature of P‐humic acid complexes was determined by ³¹P NMR analysis. Availability of these dissolution products was studied by growing corn plants in aerated hydroponics to which 200 mg apatite and 0 to 800 mg/L HA were added at pH 5 or 7. The results indicated that the rate of dissolution of apatite was parabolic in regression with time, and increased by increasing the amounts of HA or FA applied from 100 to 800 mg/L The dissolution reaction was influenced by pH, because larger amounts of PO₄ ³‐ions were detected at pH 5 than at pH 7. ³¹P NMR spectroscopy indicated the presence of P‐humic acid complexes, previously believed to be humophosphate esters. The PO₄ ^3‐ ion was complexed by HA at pH 7 or above, but PO₄ ^3‐ appeared to be released again as adsorbed and free ions at pH <5.0. Plant performance corresponded with increased PO₄ ^3‐concentrations at pH 5.0. No significant improvement over the control was observed in the growth of corn plants by apatite + HA treatments at pH 7. However, plant growth was increased significantly over the control by apatite + HA treatments at pH 5.0. Better growth performance of corn plants were noticed by apatite + HA than by KH₂PO₄ treatments at pH 5.0.     

Effects of coalbed methane‐produced water on sorghum‐sudangrass growth and soil chemical properties

Abstract

Production of methane gas from coal seams generates well water that is slightly to moderately saline. Since land application is a potential method of disposal for this water, a greenhouse study was conducted to evaluate plant response and changes in soil chemical properties resulting from irrigation with coalbed methane‐produced water. The soil was a Montevallo (Typic Dystrochrepts)‐Nauvoo (Typic Hapludults) association located in northern Alabama. Two irrigation methods used in the initial greenhouse test were 1) continuous, irrigation 24 h d^‐1 and 2) intermittent, irrigation for 12 h and off for 24 h. In a second greenhouse test, three irrigation methods were used: 1) continuous, irrigation for 24 h d^‐1, 2) intermittent, irrigation for 12 h and off for 48 h, and 3) irrigation to maintain field capacity, by daily additions of the respective irrigation water. The flow rate for continuous and intermittent irrigation treatments was 3.75 mm h^‐1. In each greenhouse test, 5 levels of salinity were generated by mixing well‐produced water with deionized water to give solutions containing 0, 10, 20, 40, and 100% well‐produced water (specific conductance (second greenhouse test) of 0.2, 1.4, 2.2, 4.4, and 9.3 dS m^‐1, respectively). Corresponding sodium adsorption ratios were 0.1, 27, 36, 55, and 81, respectively. Sorghum‐sudangrass [Sorghum bicolor (L.) Monech] was harvested for forage yields and chemical analysis at 14–30 days after initiation of irrigation treatments. Results from these preliminary short term, greenhouse studies show that coalbed methane produced water that is typical for Alabama (total dissolved solids ≤2000 mg L^‐1) can be applied to highly weathered soils. The results indicate that plant growth of summer annual grasses will be optimized if an irrigation system is used to apply produced water at a rate to maintain soil moisture at or near field capacity.     

Effects of mes [2(n‐morpholino)‐ethanesulfonic acid] and ph on mineral nutrient uptake by mycor‐rhizal and nonmycorrhizal maize

Mycorrhizal (+VAM) and nonmycorrhizal (‐VAM) maize (Zea mays L.) plants were grown in sand culture in a greenhouse to determine effects of MES [2(N‐morpholino)‐ethanesulfonic acid] (2.0 mM) and pH (4.0, 5.0, 6.0, and 7.0) on mineral nutrient uptake. Plants were inoculated with the vesicular‐arbuscular mycorrhizal (VAM) isolate Glomus intraradices UT143. Shoot and root dry matter yields were lower in plants grown with MES (+MES) than without MES (‐MES), and decreased as pH increased. Shoot concentrations of N, Ca, Mg, Mn, and Zn were generally higher in +MES than in ‐MES plants, and nutrient contents of most nutrients were generally higher in + MES than in ‐MES plants. Concentrations of N, Ca, Mg, and Mn increased and P, S, and Fe decreased, while contents of all measured nutrients except Mn and Zn decreased as pH increased. Concentrations of Mn, Fe, Zn, and Cu were higher in +VAM than in ‐VAM plants, and contents of P and Ca were higher in ‐VAM than in +VAM plants and Zn content was higher in +VAM than in ‐VAM plants. MES had marked effects on mineral nutrient uptake which should be considered when MES is used to control pH of nutrient solutions for growth of maize.     

Lettuce plant growth with the use of soil conditioner and slow‐release fertilizers

Abstract

In two pot experiments, lettuce plant growth under different soil‐water conditions was examined. In the first experiment, the effect of soil conditioner in combination with slow‐release and water‐soluble fertilizers was considered. In the second experiment, lettuce plant resistance in moisture stress with the use of a soil conditioner was evaluated. The first experiment showed that the use of soil conditioner with slow‐release fertilizers gives greater yield than the use of water‐soluble fertilizers alone. The second experiment showed that there is no difference on the yield and quality of lettuce plants between the trials until the irrigation time of twenty days.     

Influence of air drying and soil gas‐phase carbon dioxide on DTPA‐extractable iron in calcareous soils

Abstract

The extraction of a field‐moist soil with DTPA will result in a level of extractable iron (Fe) lower than that of the air‐dried soil. Soil gas‐phase carbon dioxide (CO₂) levels may be considerably higher than ambient atmospheric levels, especially in wet soils in the field. This study was undertaken to determine whether gas‐phase CO₂ level influences the quantity of Fe extracted by DTPA. Three moist calcareous soils were incubated for 21 days, each at three different partial pressures of CO₂, after which the moist soils were extracted with DTPA. A sample of each soil was also air dried, and was subsequently extracted with DTPA. In each case, DTPA‐extractable Fe from the moist sample was lower than that from the air‐dried sample; however, DTPA‐extractable Fe increased with increasing CO₂ partial pressure of in the moist soils. DTPA‐extractable Fe concentration for a given soil following air drying was not significantly influenced by the CO₂ partial pressure during incubation of the originally field‐moist soil. DTPA‐extract pH of the moist soils followed the same trend as soil‐solution pH (i.e., as CO₂ concentration of the soil gas‐phase increased, soil solution pH and DTPA extract pH both decreased); however, the slope of the pH versus log P_CO2 curve was less pronounced in the DTPA extract due to the buffering capacity of the triethanolamine. From this study, it is concluded that elevated soil gas‐phase CO₂ partial pressure does not contribute to the lower level of DTPA‐extractable Fe observed when the extraction is performed on a field‐moist versus an air‐dried soil; increased CO₂ partial pressure actually resulted in a slight increase in concentration of DTPA‐extractable Fe obtained from a field‐moist soil.     

The influence of solid urban waste compost and nitrogen‐mineral fertilizer on growth and productivity in potatoes

Abstract

The influence of solid urban waste (SUW) compost and nitrogen (N)‐mineral fertilizer on the growth and productivity in semi‐early harvest potatoes (Solanum tuberosum L, var. ‘Edzina') was studied over a period of three years. Nine treatments derived from a factorial combination of 3 levels of SUW compost (0, 18, 36 T#lbha^‐1) and 3 levels of N‐mineral fertilizer (0, 125, 250 Kg N ha^‐1) were carried out on a sandy, moderately fertile plot. The applications of SUW compost and N‐mineral fertilizer showed a stimulation in plant development with respect to the non‐treated controls. The mineral fertilizer treatment gave markedly higher results. Plant response to the combined mineral fertilizer‐compost treatments demonstrated a tendency towards saturation within each level of application. Potato productivity results indicated that this crop reacts strongly and positively to an application of N‐mineral fertilizer, but only slightly to the treatment levels of compost considered in the study. As a consequence of the application of SUW compost, the application‐response graphs reveal a reduction in the optimal levels of N‐mineral fertilizer application and an increase in the efficacy of the mineral fertilizer.     

Changes in organic matter and enzymatic activity of an agricultural soil amended with metal‐contaminated sewage sludge compost

Abstract

The effect of organic amendment with sewage sludge composts of varying heavy metal content on the organic matter content and enzymatic activity of an agricultural soil supporting barley (Hordeum vulgare L.) or lettuce (Lactuca sativa L.) crops was studied. The organic amendments did not improved lettuce growth, the contaminated composts having a negative effect on yield. However, all organic amendments improved barley straw yields although they did not affect grain yields. The addition of the organic materials increased the total carbohydrate content of the soil although this content decreased with cultivation. There was a clearly observed effect of crop type and the degree of heavy metal contamination of the amendment on the most labile carbon (C) fractions (water‐soluble C, carbohydrates, and polyphenolics). In general, soil enzymatic activities were stimulated by addition of sewage sludge compost with low heavy metal content. The compost containing high level of cadmium (Cd), copper (Cu), nickel (Ni), and zinc (Zn) inhibited protease‐BAA activity with respect to the other composts. After cultivation, urease activity increased in soil amended with the high dose of composts, regardless their degree of metallic contamination. Both crop type and metallic contamination contained in the organic materials added influenced phosphatase and ß‐glucosidase activity.     

Effects of soil type,mineral nutrition and salinity on greenhouse‐grown muskmelon in winter 1

Greenhouse experiments under winter conditions were conducted to examine the effects of soil type, mineral nutrition and salinity on vegetative growth and. fruit yield of ‘Galia’ muskmelon (Cucumis melo L.). Growth in a calcareous soil or in sand, under low nutrition level or with 200 mM NaCl added during fruit maturation, imposed significant stresses on the plants expressed by (a) a decrease in dry matter accumulation in vegetative organs, in fruit number and size, and (b) an increase in dry matter percentage in leaf blades and stems. Despite the significant differences in vegetative growth of plants grown in heavy soil vs sandy soil, and in high nutrition vs low nutrition levels, the distribution of dry matter among vegetative organs (leaves, stems and roots) was affected only slightly. Sandy soil, low nutrition and high salinity decreased branching, and thus the distribution of dry matter between the main shoot and the branches. Dry matter percentage in leaf blades and stems was a sensitive parameter which increased under soil, nutrition or salinity stresses. Fruit netting and total soluble solids (TSS) content were significantly decreased by sandy soil and low nutrition level. Application of salinity during fruit growth increased both netting and TSS.     

Localized root growth in soil induced by controlled‐release urea granule and barley nitrogen uptake

Controlled‐release urea is a fertilizer which meters out urea over a long period of time. It can provide a favorable nitrogen (N) concentration for root growth, especially at the early stage of plant development. The objective of this study was to determine the interactions of urea or controlled‐release urea granules with barley roots and the resultant N uptake by plants. Two experiments (Experiment I and Experiment II) with treatments of Nil, non‐coated urea, Coated I and Coated II (Coated I and Coated II are controlled‐release urea products) were conducted in a greenhouse at 23±5°C. In both experiments, one barley (Hordeum vulgare L. cv. Duke) seed and one granule of urea or controlled‐release urea were placed in a pot (5.2‐cm height and 8‐cm diameter) containing soil low in mineral N. In Experiment I, shoot and soil samples were taken at 14, 28, and 46 days after seeding. Roots and fertilizer interaction were visually examined and photographed. In Experiment II, root samples both around the fertilizer granule and away from the granule were taken only at 28 days after seeding. In both experiments, dry matter mass and total N content of shoot and root, and mineral N in soil were determined. In Experiment I, at the 28‐day sampling roots proliferated around the controlled‐release urea granule but not around the urea granule. Shoot N uptake since the 28 days was higher with controlled‐release urea than with urea because of the root proliferation. In Experiment II, root dry mass and N content around the granule was higher with controlled‐release urea than with urea. In the controlled‐release urea treatments, root mass and N content away from the granule were also increased in comparison to the Nil. This shows a stimulus relationship between the two portions of the roots in the same plant, i.e., the roots being accessed to the N source increased growth of the other roots with no access to the source. Because only a small portion of roots was involved in N uptake in the controlled‐release urea treatments, the intensity of N uptake per unit of root mass was much higher with controlled‐release urea as compared to urea. In conclusion, root growth was enhanced around controlled‐release urea granule, and that portion of roots around the fertilizer granule played a major role in absorbing N. In addition, a stimulus relationship existed between roots grown around the granule and those grown away from the granule.     

Extraction Methods for Phosphorus and Their Relationship with Soils Phosphorus‐Buffer Capacity Estimated by the Remaining‐Phosphorus Methodology‐A Pot Study with Maize

Abstract

This work aimed to calibrate Mehlich 1, Mehlich 3, Bray 1, Olsen, and ion‐exchange resin extraction methods with maize phosphorus (P) responses in a pot study with lowland and upland soils with different P‐buffer capacities and to evaluate whether the calibration can be enhanced through the knowledge of remaining P. The experimental design was completely randomized with four replications in a factorial arrangement involving five P concentrations and four lowland or seven upland soils. The remaining P for each soil was determined, P‐buffer capacity was estimated, and the soils were grouped according to the results. Correlation coefficients showed that the remaining P is strongly dependent on clay and soil organic‐matter content, and its determination was useful to the evaluation of the extractants. The classification and grouping of soils according to their P‐buffer capacity improved the correlations between extracted P and plant response for Mehlich 1 and Bray 1 extractants. The Mehlich 3, Olsen, and resin methods presented better performances, independent of soil grouping.     

Effect of fused magnesium phosphate on paddy grown on “akiochi” soil with particular reference to phosphorus and silicon

In order to increase the p:tady prodution of our country, a better fertilizer practice is needed Particularly in the low productive areas known as “akiochi” fields which are now said to occupy about one fifth of the whole paddy areas in Japan.     

The influence of soil aeration on growth and elemental absorption of greenhouse‐grown seedling pecan trees

Abstract

‘Dodd’ pecan seedlings were exposed to 3 levels of soil aeration for 30 days; 100%, 5%, and 0% of the container surface exposed to the atmosphere. These treatments resulted in about 21%, 13.5%, and 3% soil O₂and 0.3%, 5%, and 13% soil CO₂for 100%, 5%, and 0% of the container surface exposed, respectively. Restricting soil aeration induced partial stomatal closure, and decreased leaf number, leaf area, and leaf, trunk and root dry weights. The decrease in root dry weight associated with reduced soil aeration exceeded the decrease in top dry weight by about 50%. Translocation of N and P to the leaves was reduced when soil aeration was restricted, but root N and P concentrations were increased compared to trees grown in well aerated soil. Leaf elemental concentrations of Ca, Mg, and Mn were lower when trees were exposed to reduced soil aeration. Zinc and Fe concentrations were greater in the roots of trees with low aeration, but leaf and trunk concentrations of Zn and Fe were not affected