摘要:

Extraction steps of the DTPA procedure for copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) determinations were tested in four representative soils from the State of São Paulo (Brazil), namely Red‐Yellow Latosol (LV), Red‐Yellow Podzolic (PV), Dusk‐Red Latosol (LR), and Sand Soil (AQ). The results indicated that the use of volume sampling, although possible, may cause biased results. Thus, direct soil sampling in terms of mass is recommended. Variations in the pH of the extraction solution from 7.1 to 7.5 can be critical for acid soils, but the best results for the soils tested were observed by keeping the extraction solution pH at 7.3. Some sort of equilibrium seems to be reached after a soil/extraction solution shaking time of 150 min for all soils tested. No significant changes in the micronutrient concentrations are observed if the soil suspension is filtered up to 120 min after shaking, but changes may occur upon storing the filtrate for more than 7 days at temperatures of 25°C‐30°C.

ISSN:0010-3624    

DOI:10.1080/00103629709369767

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Vitis viniferaL. cvs. Pinot blanc and Sauvignon blanc, grafted on the hybrid rootstockV. BerlandieriPlanch, xV. ripariaMichx. ‘S.O.4’ (intermediate tolerance to lime‐induced chlorosis), were grown in pots with a calcareous soil. At fruit set and at the beginning of ripening stage ('veraison') of the third growing year, leaf blades, petioles, and fruit (berries) were analyzed for macronutrient and trace element composition, and plants were scored for chlorosis symptoms. No significant variations in the mineral composition of leaf blades and petioles were found between chlorotic and non‐chlorotic plants. Chlorotic plants (at ‘veraison') had higher nitrogen (N), phosphorus (P), calcium (Ca), and magnesium (Mg) berry concentrations and total contents (per cluster) than non‐chlorotic vines. Total iron (Fe) concentration in the tissues tested was not directly related to lime‐induced chlorosis of the two cultivars tested.

ISSN:0010-3624    

DOI:10.1080/00103629709369768

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In research on selecting rice (Oryza sativaL.) cultivars that are resistant to metal toxicity, an experiment was carried out with the objective of determining the effects of rice cultivars with differing oxidizing powers on the forms of metals in the rhizosphere soil. Four rice varieties were grown for 40 d in 3 soils which had differing amounts of iron (Fe) and manganese (Mn) oxides. The rhizosphere soil was kept separate from the non‐rhizosphere using nylon mesh “rhizobags”;. The soils were treated with either 5 mg/kg cadmium (Cd) or 20 mg/kg zinc (Zn). At the end of the experiment the soils were analyzed using a sequential fractionation scheme for five forms of Cd, Zn, Fe, and Mn. The rhizosphere soil was lower in pH (p=0.14) and P (p=0.05) than the non‐rhizosphere soil. Iron in the Mn oxide fraction was ten times higher in the rhizosphere as opposed to the non‐rhizosphere soil while the rhizosphere soil Mn was lower in this fraction. Cadmium in the rhizosphere soil was increased in both the exchangeable and organic matter fractions. Rice with higher oxidizing power decreased the Mn in the Mn oxide fraction, since the Mn reduced by submergence was oxidized by the oxygen supplied by the roots. Rhizosphere soil Zn increased in the Mn oxide fraction indicating that it may have been adsorbed or occluded by the oxides freshly precipitated by the roots. This increase coincided with a decrease of Zn in the exchangeable fraction. The increase in Zn in the Mn oxide fraction coupled with a decrease in more plant‐available fractions indicated that rice cultivars with high oxidizing power can alter the rhizosphere forms of metals so as to decrease their plant availability.

ISSN:0010-3624    

DOI:10.1080/00103629709369769

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The states of Mato Grosso and Mato Grosso do Sul of Brazil have large lowland soils, locally known as “Varzea”;, and the major part of this area is not used for agricultural purposes. The present study was undertaken at the National Rice and Bean Research Center, Goiânia‐Goiás, to characterize the fertility and particle size of lowland soils of these states. Soil samples were collected at depth intervals of 0–20 cm, 20–40 cm, 40–60 cm, and 60–80 cm at 14 locations in the two states. Organic matter contents and pH averaged 46 g/kg and 5.2 in the surface 20 cm of soil. Phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn) contents were adequate for annual crop production in the 20‐cm soil layer. However, iron (Fe) content in some of the samples was high and manganese (Mn) content was lower than critical level under well‐drained soil conditions. In almost all soil samples analyzed, aluminum (Al) content was higher than 1 cmol/kg, and Al saturation was also higher, especially for legume crops. In general, base saturation was lower in these soils. A large part of these samples has clay loam texture which is considered appropriate for annual crop production.

ISSN:0010-3624    

DOI:10.1080/00103629709369770

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A constraint to plants grown on acid soils is commonly aluminum (Al) toxicity. Plants grown with excess Al normally have imbalanced minerals compared to plants grown without Al. This study was conducted to determine differences among 25 sorghum [Sorghum bicolor(L.) Moench] genotypes with broad genetic backgrounds for Al, phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), iron (Fe), zinc (Zn), and copper (Cu) acquisition when grown with 0, 200, 400, 600, and 800 μM Al in nutrient solutions (pH 4.0). Genotypes were categorized into “Al tolerant”;, “Al sensitive”;, “intermediate Al tolerant”;, and SC 283 (an Al‐tolerant standard) according to net main axis root length (NMARL) of plants grown with 400 UM Al. Shoot and root concentrations of minerals were generally lower as Al increased, and some minerals changed more than others. The Al‐tolerant genotypes generally had higher concentrations of Mn in shoots and K in roots, lower concentrations of Ca in shoots and roots, and lower concentrations of P, Mg, and Mn in roots than Al‐sensitive genotypes. Except for Zn concentrations in shoots, concentrations of minerals in the intermediate Al‐tolerant group generally appeared between the Al‐tolerant and Al‐sensitive groups. Mineral concentrations in SC 283 generally followed the Al‐tolerant group, except for shoot P concentration (lower) and root S concentration (higher) than the other genotypic groups. Mineral acquisition in shoots and roots of the sorghum genotypes used was not a good indicator for distinguishing tolerance to Al toxicity.

ISSN:0010-3624    

DOI:10.1080/00103629709369771

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Soil and water conserving practices must be used to sustain dryland crop production in semiarid regions. In this 1994 study, we evaluated the effects of different cropping system and tillage method treatments on surface residue cover, organic matter content, aggregation, and water infiltration for a soil used for grain sorghum [Sorghum bicolor(L.) Moench] production in the United States Southern Great Plains from 1982 to 1994. Cropping systems were continuous sorghum (CS) and winter wheat (Triticum aestivumL.)— fallow—grain sorghum—fallow (designated WSF) and tillage methods were no‐tillage (NT) and stubble mulch tillage (SMT). Treatments were CS‐NT, CS‐SMT, WSF‐NT, and WSF‐SMT. Surface residue cover before planting sorghum was >70% with CS‐NT and WSF‐NT, 29% with CS‐SMT, and 12% with WSF‐SMT. Surface cover after planting was =50% with both NT treatments, whereas amounts with other treatments were similar to those before planting. Soil organic matter contents (0‐ to 10‐cm depth) were greater on CS than on WSF plots, but were not affected by tillage method in either cropping system. Water stable aggregation (0‐ to 2‐cm depth) was greater with SMT than with NT in both cropping systems, but differences between cropping systems were not significant. Dry aggregates were smaller with NT than with SMT. Water infiltration was or tended to be greater on CS than on WSF plots, apparently because the WSF plots contained more water when infiltration was measured. Infiltration was not affected by tillage method, apparently because the greater amount of surface residues on NT plots counteracted the less water stable aggregates and smaller dry aggregates that had potential for reducing infiltration on the NT plots. This study indicates that no cropping system‐tillage method combination treatment had a consistently beneficial or detrimental effect on soil conditions. In conclusion, both cropping systems (CS and WSF) and both tillage methods (NT and SMT) are suitable for conserving soil and water resources and, therefore, for sustaining dryland crop production in the semiarid United States Southern Great Plains.

ISSN:0010-3624    

DOI:10.1080/00103629709369772

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A long‐term soil incubation and column nutrient leaching study was conducted to determine nitrogen (N)‐mineralization rates of selected Florida Histosols with drained and intermittent‐flooded conditions. Five surface soils from the Everglades Agricultural Area (EAA) were packed in columns (5‐cm i.d. containing the 0‐ to 15‐cm depth of each soil) and leached with 0.01M CaC12 followed by distilled water every 25 d for 1 yr. Drained columns were treated with a minus‐nitrogen‐phosphorus (NP) solution followed by applying ‐0.97 MPa tension to remove excess solution. Flooded columns received the same minus‐NP solution, but were flooded to a depth of 3 cm. Both treatments were incubated for 25‐d periods, solution sampled, and treatments reapplied. Because flooding conditions could not be maintained during the sampling period, this treatment is referred to as intermittent flooded. The ammonium‐nitrogen (NH4+‐N) released from drained soils accounted for less than 6% of the total soluble N released from all soils, compared to more than 30% released from flooded soils. There were no differences in the amounts of soluble organic N from drained and intermittent flooded soils. Total soluble N from the surface 15‐cm of drained soils ranged from 217 to 509 kg‐ha‐1yr‐1, with 50 to 67% released as nitrate‐nitrogen (NO3‐‐N). In contrast, total soluble N released from flooded soils ranged from 168 to 345 kg‐ha‐1yr‐1, with less than 3% released as NO3‐‐N.

ISSN:0010-3624    

DOI:10.1080/00103629709369773

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Tea (Camellia sinensisL.) grown in China often suffers from severe seasonal drought in the summer causing drastic effects on productivity. In a field trial, the effect of potassium (K) fertilization on summer tea yields during 1992–1994 was studied and related to the weather conditions of the respective years. Summer tea yields of 1994 (dry year) increased significantly at K2 (300 kg K2O‐ha‐1) compared to the Kl treatment (150 kg K2O ha‐1). In contrast, only marginal effects were observed by increasing K application from Kl to K2 in the years with adequate water availability (1992 and 1993). During the latter maximum tea yields were already achieved with Kl. In addition, a pot experiment was conducted in order to investigate the interaction between the soil water regime and K availability in the soil on tea biomass production. Soil moisture was maintained at 45, 55, 65, 75, and 85% of the field capacity (FC) and K levels were 0 and 500 mg K2Okg‐1. No tea plant survived at the 45% FC level whereas all tea plants survived at or above 75% FC. The survival rate increased substantially in the K treated tea plants under moderate drought stress conditions (55% and 65% FC). The dry matter production was significantly larger with increasing soil moisture and at the high K status in the soil. This observation was most pronounced under water stress conditions. The study indicates that under moisture stress, increased survival, improved dry matter production and yields of tea plants were due to improved K bioavailability following K application. Furthermore, larger amounts of K are required under moisture stress conditions compared to normal water supply.

ISSN:0010-3624    

DOI:10.1080/00103629709369774

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Low molecular weight organic acids from rhizosphere soil of durum wheat (Triticum turgidumvar.durumL.) were studied by ion exclusion high pressure liquid chromatography (HPLC) and gas chromatography (GC). Ion exclusion HPLC was found unsatisfactory for acid determination because poor peak resolution hindered acid identification, strongly ionized solutes and oxalic acid co‐eluted in the dead volume of the column, and UV detection was not sensitive for aliphatic acid determination. Excellent resolution was obtained when the same low molecular weight organic acids were analyzed by GC. Non‐volatile low molecular weight organic acids were separated as trimethylsilyl (TMS) derivatives while volatile acids were analyzed without sample derivatization. A combination of these two GC techniques allowed for separation of 16 acids. Ten low molecular weight organic acids were identified and quantified in rhizosphere soil of durum wheat grown in three different soils. Succinic and acetic acids were most abundant among acids extracted from rhizosphere soils followed by butyric, malic, propionic and tartaric acids. Malonic, fumaric, citric, and trans‐aconitic acids were found at the lowest concentrations. Very good resolution, short analysis time, and low detection limits make the GC method very suitable for routine determinations of low molecular organic acids in rhizosphere soil.

ISSN:0010-3624    

DOI:10.1080/00103629709369775

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We studied the applicability of the so‐called fumigation‐extraction method for microbial biomass carbon and ninhydrin‐reactive nitrogen to evaluate the stabilization of rewetted compost samples. Dried samples of composts of widely different composition, sampled at the initial, thermophilic, mesophilic and curing stages of composting, were remoistened to 50% of water content and incubated at 25°C for 5 days before analysis. In rewetted raw materials, microbial biomass carbon (Bc) ranged from 11,296 to 41,601 μg/g and significatively decreased in samples of increasing stabilization reaching only 2704–5837 μg/g in rewetted mature composts. The percentage of Bcwith respect to total organic carbon (C) varied from 2.5 to 9.5% in starting materials, but was lower than 1.7% in all the end products. Ninhydrin‐reactive N of the microbial biomass (BNIN) showed the same trend that Bc, ranging from 504 to 2044 μg/g in raw material samples, declining in samples of increasing composting time and achieving rather close values in the end products (from 90 to 303 μg/g). The percentage of BNINrespect to total N was higher in raw material samples (2.0–9.8%), with final values lower than 1.1%. The Bcand BNINshowed a strong correlation (r=0.99, P<0.001) with a regression coefficient (20.1) in good agreement with those found for soils. Incubation at high temperature (53 °C) negatively influenced the content of Bcand BNINat all composting stages and had little, if any, effect on the chemical composition of microbial biomass. Results of this work show that the application of methods for the measure of microbial biomass C and ninhydrin‐reactive N in soil to rewetted composts gives valuable information on the degree of stabilization achieved by the product.

ISSN:0010-3624    

DOI:10.1080/00103629709369776

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor