摘要:

We studied the efficacy of two nitrification inhibitors, nitrapyrin (NPY) and potassium trithiocarbonate (PTC), applied to two Iowa soils and incubated at high temperature. Samples from a Canisteo soil (fine-loamy, mixed (calcareous), mesic Typic Haplaquoll; 2.6% CaCO3, pH 7.8) and a Nicollet soil (fine-loamy, mixed, mesic Aquic Hapludoll; 0% CaCO3, pH 7.0) were treated with NH4OH (28% NH3), NH4OH plus K2S3C, and NH4OH plus nitrapyrin, applied at rates of 5.7 μg g−1soil (as CS2) and 0.5 μg g−1soil, respectively. The samples were incubated at 65% of field capacity for 2, 4, 8, 16, 32, and 64 d in a greenhouse. Daily temperatures fluctuated between 21.7 and 26.7°C. Recovery of NH4+-N was approximately the same in all treatments and decreased over time at about the same rate in the calcareous Canisteo soil. The percentage of recovery of NH4+-N was highest in the samples treated with inhibitors in the noncalcareous Nicollet soil, 57.6, 36.2, and 13.6% at 16 d for the NH4OH + NPY, NH4OH + PTC, and NH4OH treatments, respectively. pH decreased less sharply in the Canisteo soil than in the Nicollet soil. The rate of decrease of pH was similar in all treatments within soils. Estimates of NH4-N half-life ranged from 15.1 to 16.1 d in the Canisteo soil and from 17.3 to 20.3 d in the Nicollet soil. Results from this study indicate that more research is needed on the fate and action of nitrification inhibitors applied at agronomically recommended rates under relatively high temperatures and in the presence of CaCO3

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Manganese and copper were found in the iron oxide plaque on roots ofPhragmites australiscollected at six sampling sites in southern Quebec and Ontario, Canada. Manganese concentration in the plaque, like that of Fe, is correlated with the Mn-bound-to-carbonates fraction of the soil/sediment. The Fe:Mn ratio of the plaque resembles the same ratio of Fe:Mn-bound-to-carbonates in the substrate. The ratio changes with environmental conditions, increasing with percentage of water and decreasing with pH. Plants located near flowing water accumulate more Mn (and Fe) in the plaque than plants in other habitats through the summer. Copper concentration in the plaque is pH-dependent and is positively correlated with the amount of Fe and Mn of the plaque, but appears to be related more closely to Mn.

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

In the Punjab territory of the Indo-Gangetic plains, calcite nodules commonly are found in soils on older stream terraces composed of calcareous silt. For this paper, we studied the morphology, mineralogy, and isotope chemistry of pedogenic calcite at Harappa, Pakistan, to determine the process by which they form and the climatic conditions under which they developed. A well-developed soil (fine-silty, mixed, hyperthermic Aridic Haplustalf) showed greatest nodule complexity in the calcic horizon by x-ray diffraction and thin section analysis; inner portions of these nodules had a radiocarbon age of 7080 +/- 120 yr BP Inner portions of nodules, which are presumed to have formed in equilibrium with soil CO2, reflect a large influence of atmospheric CO2and a very low soil respiration rate. Delta13C values indicated that a maximum of 71% of the disseminated calcite was pedogenic in origin. Oxygen isotope ratios of disseminated and nodular calcite indicate calcite precipitation in equilibrium with soil water, with δ18O values similar to that of modern precipitation. A shallower water table at some time in the past may have influenced calcite deposition deep in the profile.

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

An adequate balance of Ca to other ions in the soil solution is required to ameliorate toxicities of specific ions in the root environment or to prevent salinity-induced Ca deficiency in crops. Field and pot culture studies were conducted to evaluate use of the Ca-to-total-cation ratio (Ca:TC), in the saturation paste extract, for predicting plant-available Ca and Ca accumulation in barley (Hordeum vulgareL.) and wheat (Triticum aestivumL.). The soils used in the study were several closely associated salt-affected and nonsaline soils (Natriborolls and Agriborolls) from the Canadian prairie.Regression analysis indicated that the Ca:TC ratio in the saturation paste extract was closely related (r2= 0.656) to soluble Na, the dominant cation, but not to soluble Ca (r2= 0.326). Low Ca:TC ratios (<0.10) in the soil saturation extract were found in 32 and 57% of the A and B horizons, respectively. The proportion of total variation accounted for between Ca concentration in the plant tissue and the Ca:TC ratio of the soil extract was 75% in pot culture and 58% in the field. In contrast, the association between plant Ca and soluble Ca in the soil extract was very low (3%). Critical plant tissue levels of Ca in barley and wheat (0.25%) and alfalfa (Medicago sativaL.) (1.0%) corresponded to a Ca:TC ratio of 0.10 in the soil extract.The study demonstrated that Ca:TC ratios in saturation extracts could serve as an index for plant-available Ca and characterize the Ca status in a range of salt-affected and nonsaline soils under field conditions.

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

An experimental laboratory simulation was used to test a new concept for the amelioration of solonetzic and other sodic clay soils. In this concept a solution of a calcium salt is injected into the open cracks at the end of a dry season. The purpose of this is to stabilize the soil material in the exteriors of the soil aggregates, thus causing incomplete and retarded closing of the cracks in the subsequent wet season. As a result of this, the downward transport of water and the leaching of salts are promoted, the aeration of the topsoil is improved, and the vertical extension of roots is facilitated.The favorable effects of the treatment on the morphology and water-transmission properties of the cracks and on the desalinization and desodication of the soil increase with an increase of the Ca concentration in the amendment solution.The results of the laboratory simulation indicate that it is worthwhile to try the new method of sodic clay soil amelioration on a field scale. On calcareous soils and soils containing soluble carbonates, strong acids or aluminum salts may be used instead of calcium salts. Also with these electrolytes, however, the success of the treatment depends on the concentration of the amendment solution used. As gypsum has only a limited solubility and more soluble calcium or aluminum salts are expensive, waste acids may have to be used.

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Costs of sodic soil reclamation can be reduced when coarse-grade gypsum is used, as the production and transport prices of this gypsum are much lower than of agricultural-grade gypsum. In a feasibility study laboratory experiments were conducted to evaluate the leaching water requirements for five gypsum grades with different particle size distributions. Results indicated that the leaching water requirements do not differ significantly for the mixtures studied, provided that the percolation rates are low. The total time of reclamation appears to increase with increasing particle size. Different methods of application of gypsum were tested. The largest efficiency was obtained when an amount equal to the gypsum requirement was partly mixed with the soil and partly applied onto the soil surface.

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Drainage water that would pass through successively deeper soil layers was estimated at selected weather stations. Monthly Thornthwaite potential evapotranspiration amounts were subtracted from the precipitation amounts to calculate the yearly net soil water addition, or loss if the soil lost plant-available water. Surplus plant-available water at year's end was the initial amount in the next year's calculation. With each monthly addition, the total depth of water penetration was calculated. For fine-textured clay soils, water drainage does not occur below 1 m in the northwestern quarter of the state, but in the southeastern corner, a total of 3.5 m of water drains below 1 m during 10 or 11 yr in a 100-yr period. For sandy soils, drainage does not occur below 3.0 m in the northwestern quarter, but in the southeastern corner up to a total of 4 m of water drains below 3.0 m during 10 to 13 yr in 100 yr. Plants with deep root systems, such as alfalfa, could remove subsoil water to this depth. Drainage of water from the soil profile is unlikely on nearly level upland areas that were originally prairie and that do not receive run-in water.Semiarid, northwestern South Dakota has high evapotranspiration and low precipitation, so that drainage through the subsoil is at least low if not negligible on nearly level upland landscapes. Precipitation and probably subsoil drainage increase southeast across South Dakota. The drainage would be used by plants if it were not deeper than the rooting zone. To assess leaching potential, weather and soil data were used to calculate the volume of drainage water that would pass through successively deeper soil layers in South Dakota.

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Condensed inorganic phosphates, including pyrophosphate (PP), are of interest in soil fertility because of their water solubility and high P content. However, phosphate (P) is largely taken up by plants as orthophosphate (OP). Plant uptake, therefore, requires PP hydrolysis.Hydrolysis of pyrophosphate (PP) was studied in autoclaved and nonautoclaved soils from Quebec. The samples studied were two surface soils from cultivated fields of St. Bernard (Typic Hapludoll) and Dalhousie (Mollic Haplaquept) and three minerals: goethite, kaolinite, and montmorillonite. Soil and mineral samples were fractionated into two separates. Each soil and mineral fraction was treated with PP and incubated under anaerobic conditions at 10, 20, and 30°C for periods ranging from 1 to 28 d.The percentage of PP hydrolyzed was significantly lower in goethite samples than in soil, kaolinite, and montmorillonite samples. There was less PP hydrolysis in fine fractions (2 to 0.2 μm) than coarser fractions (20 to 2.0 μm) in both autoclaved and nonautoclaved fractions regardless of soil or mineral type. Rates of PP hydrolysis were 2 to 5 times greater in nonautoclaved than autoclaved soil fractions, and rates of PP hydrolysis increased with increased temperature from 10 to 30°C. The effect of temperature on hydrolysis rates, however, was more obvious in the autoclaved than nonautoclaved samples.Added orthophosphate (OP) prior to PP addition reduced the amount of PP remaining nonhydrolyzed, probably due to reduced PP sorption. Increasing the level of PP applied to soil reduced the percentage of PP hydrolysis regardless of the level of OP in the OP-amended soils.

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0038-075X    

出版商:OVID    

年代:1990

数据来源: OVID