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1.
Sandpit lakes of Nebraska are residential developments frequently affected by excess phosphorus (P). The objectives of this study are to quantify P retention and release by sandpit lake soils and determine properties related to P retention and release. Soils were sampled at 0–15 and 15–30 cm deep from six developed and one undeveloped site. Adsorption was fit to the Langmuir isotherm and desorption was fit to the Elovich equation. Clay and organic matter contents identified some sites as amended with finer-textured soil. Iron, aluminum, and P fractions were low in all samples but greater in amended soil. Adsorption maximum was greater at 0–15 cm deep for all but the undeveloped site. Adsorption energy parameter was greater at 15–30 cm deep. Elovich slopes and intercepts were generally greater in the 0- to 15-cm samples. Slopes were positively related to soil P richness. Importing finer textured soil to lake sites increases P retention and should help preserve water quality.  相似文献   

2.
ABSTRACT

A detailed study was conducted to investigate the long-term effects of rice–wheat and poplar-based agro-forestry systems existing on a large area for last 25 years on the distribution of macro as well as micronutrients in surface soils, as well as their profiles. To achieve these objectives, profile soil samples (0–150 cm) were collected from 10 randomly scattered locations each from rice–wheat and poplar-based agro-forestry systems and analyzed for various physico-chemical properties. The results of our investigation revealed that pH, EC, OC available N, P and K reported significantly higher levels in agro-forestry as compared to rice–wheat system. On the other hand, DTPA-extractable and total Zn, Cu, Fe and Mn were significantly higher in D1 (0–15 cm), D2 (15–30 cm) and D3 (30–45 cm) depths of rice–wheat system which may be attributed to the reduced conditions prevailing during rice crop. Nutrient budgeting also assessed the impact of crop removal and fertilizer inputs along with recycling of crop residue and leaf litter. Also, the build-up of available nutrient status in surface layer (0–15 cm) and soil profiles (0–150 cm) continuously under these two systems helped in maintaining agricultural sustainability and soil fertility over a long period of time.  相似文献   

3.
The aim of this study was to analyse the soil compaction and its spatial variability on an alluvial plain in K?z?l?rmak River Delta in Turkey, which is an important agricultural area where vegetable, rice, cereals and other crops have been grown under conventional tillage and irrigation over a long period. Penetration resistance (PR) was measured at 5 cm depth intervals between 0 and 40 cm soil depth, and gravimetric water content (GWC), field capacity (FC) and texture were determined for 0–20 cm and 20–40 cm. Penetration resistance values in some parts of the area were higher than the critical value for root growth limitation, the mean PR values at all depths were considerably lower than the critical value despite a relative increase in PR with soil depth. The areas with values greater than 3.0 MPa, except for 0–5 cm, were generally located in the fields with high sand content, especially near the K?z?l?rmak River. In contrast, for 0–5 cm, the areas with PR greater than 3.0 MPa, which is the value accepted for root growth limitation, were usually located in the west and northwest of the study area and had a high clay content.  相似文献   

4.
The aim of this study was to understand impacts of long-term (43 years) fertilization on soil aggregation, N accumulation rates and δ15N in surface and deep layers in an Alfisol. Soil samples from seven treatments were analysed for N stocks, aggregate-associated N in 0–30 cm and the changes in δ15N in 0–90 cm depths. The treatments were: unfertilized control (control); recommended N dose (N); recommended N and phosphorus doses (NP); recommended N, P and potassium doses (NPK); 150% of recommended N, P and K doses (150% NPK); NPK + 10 Mg FYM ha?1 (NPK + FYM) and NPK + 0.4 Mg lime ha?1 (NPK + L). Results revealed that plots under NPK + FYM had ~39% higher total N concentrations than NPK + L in 0–30 cm soil layers. In NPK + L, macro-aggregates had 35 and 11% and microaggregates had 20 and 9% lower δ15N values than NPK + FYM in 0–15 and 15–30 cm soil layers, respectively. However, plots receiving NPK + FYM had ~39% greater deep soil (30–90 cm) N accumulation than NPK + L. These results would help understanding N supplying capacity by long-term fertilization and assist devising N management strategies in sub-tropical acidic Alfisols.  相似文献   

5.
Winter wheat (Triticum aestivum L.) production in northwestern China as a monoculture is hampered by unfertile soil and drought. With the fast-developing Chinese chemical fertilizer industry, many farmers now use more nitrogen (N) fertilizer as topdressing for winter wheat in early spring, in addition to a basal dose of N fertilizer applied in the previous autumn at seeding time. The objective of this study was to evaluate the increase in grain yield of dryland winter wheat by early spring N fertilizer topdressing, and its relationship to soil moisture, available N, phosphorus (P) and potassium (K). Field experiments with no N fertilizer topdressing (Fb) and N fertilizer topdressing (Fb+t) treatments were carried out over two growing seasons at 54 site-years to assess the relationship between increase in winter wheat grain yield by early spring N fertilizer topdressing and soil moisture, available N, P and K in Changwu county, Shaanxi province, China. Compared to Fb treatment, the Fb+t treatment produced grain yields lower at 10 site-years, and increased by <10% at 21 site-years and by >10% at 23 site-years. The results indicated that topdressing N fertilizer could increase wheat grain yield when soil nitrate-N accumulation in the 0–20, 20–40 and 40–60 cm depths was less than 121.7, 36.4 and 24.1 kg N ha?1, and soil moisture content in the 40–60, 60–80 and 80–100 cm depths was more than 15.7%, 16.7% and 16.9%, respectively. The findings also suggested that it is not necessary to analyze soil for ammonium-N, available P and K before topdressing N fertilizer. It is necessary to analyze 0–60 cm soil profile for nitrate-N and 40–100 cm depth for soil moisture before topdressing N fertilizer for winter wheat in dryland areas of northwestern China.  相似文献   

6.
More than 50% of global soil organic carbon stocks are stored below 20 cm of soil depth capable of massively altering global C cycle and climate. However, subsoil C dynamics are largely overlooked implicitly assuming that surface and subsoil C dynamics are similar. Here, we compared the soil C dynamics in surface and subsurface soil layers in response to nitrogen and maize leaf litter additions. Soils, sampled from 0 to 5, 15 to 35, 35 to 55 and 55 to 75 cm depths, were incubated at 25°C after adding litter, nitrogen (NH4NO3) or litter plus nitrogen. Soil respiration (C mineralization) was measured throughout the incubation period. Litter addition significantly increased C mineralization in all the soil layers. However, the soil CO2 release relative to control was more than twofold higher in 15–35 and 35–55 cm soil layers than the surface layer. Nitrogen additions significantly decreased C mineralization in 0–15 cm soil, increased in 35–55 cm and had minimal effects in the 15–35 and 55–75 cm layers. Different soil C dynamics in surface and subsurface soil layers found in our study contradict the general assumption that soil C dynamics may be treated similarly along different soil depths.  相似文献   

7.
Colorimetric P determination mainly reflects inorganic P, whereas inductively coupled plasma spectroscopy (ICP) measures all P in solution. We compared Morgan extractable P for ICP (MP-ICP) and colorimetry (MP-Color) using dairy farm field samples (0 to 20 cm) across northern New York (n = 250) and hayfield transect samples (0–15, 15–30, 45–50 cm; n = 164). Soil organic matter, pH, and extractable cations were also measured. Mean ratio of MP-ICP: MP-Color was 1.46 and differed significantly among Morgan P categories, ranging from 1.89 for low to 1.06 for very high. The numeric difference between MP-ICP and MP-Color ranged from 0 to 12.9 mg kg?1. Organic matter, Al, and pH jointly accounted for 55% of the variability between methods across samples. Fertilizer P recommendations differed based on the two methods, suggesting results from both methods should be reported, particularly in the responsive range.  相似文献   

8.
Abstract

Long‐term potassium (K) fertilization practices are likely to affect the K content of soils. This study assessed the effect of long‐term K fertilization strategies for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotations on extractable K in the soil profile of a major Iowa soil type at two locations. The soil type was a Webster fine‐loamy, mixed, mesic, Typic Haplaquoll at both sites. Soil samples were collected from the 0–15, 15–30, 30–60, and 60–90 cm depths after 17 years (Site 1) or 19 years (Site 2) of K fertilization with combinations of two initial rates and four annual rates. The initial rates were 0 and 1,344 or 1,120 kg K ha‐1 at Site 1 and 2, respectively, and the annual rates ranged from 0 to 100 kg K ha‐1. Samples were analyzed for ammonium acetate‐extractable K (STK) and nitric acid (HNO3)‐extractable nonexchangeable K (HNO3‐K). Concentrations of STK and HNO3‐K in the top 0–15 cm soil layer at the two sites were higher for the high initial K rates and were linearly related with the annual K rate. Results for the subsoil layers varied between sites and extractants. At Site 1, annual rates of 30 kg K ha‐1 or higher resulted in a relative accumulation of HNO3‐K in the 15–30 cm layer. At Site 2, these rates resulted in relative accumulations of STK in the 30–60 cm layer and of HNO3‐K in the 60–90 cm layer, but with relative depletions of STK in the 15–30 and 60–90 cm layers. Thus, use of one extractant may not always be sufficient to evaluate cropping and fertilization effects on subsoil K. Long‐term K fertilization of corn and soybean rotations affected extractable K of both the topsoil and subsoil. The effects on subsoil K, however, were smaller compared with effects on the topsoil and varied markedly between sites, subsoil layers, and extractants.  相似文献   

9.
Abstract

Poultry litter (PL) is a cheap alternative to conventional fertilizers. The use of PL in this way also reduces the environmental problems normally associated with its disposal. The residual effect of PL may reduce the amount of fertilizer (especially N fertilizer) required by subsequent crops. This study examines the residual effects of PL (with and without additional mineral fertilizer) on the properties of a volcanic ash soil and on silage maize (Zea mays) yields in central Chile. Poultry litter and mineral fertilizer were applied in 2002–2003 and their residual effects were determined in 2004–2006. The dry matter (DM) yield, nutrient balance and apparent nitrogen recovery efficiency (ANRE) of the silage maize were determined for each season, and the soil properties were analyzed at three depths (0–20, 20–40 and 40–60 cm) at the end of the third season. Crop yield showed a positive response to all fertilizer treatments. The residual effect, the nutrient balance, N uptake and ANRE also improved with fertilizer treatment, especially with the PL treatments. The average DM yield for the PL treatments was higher than that observed using mineral fertilizer by 2.8 and 1.2 Mg ha?1 in the third and fourth years, respectively. The ANRE was generally higher in the PL treatments, although it decreased over time (12.4 and 1.7% for the last 2 years, respectively). The mean ANREs for the mineral fertilizer treatment were 4.1 and 1.6% for the same years. The results suggest that the PL treatments had an important positive residual effect in terms of N supply. This should be taken into account when planning the next crop. After two annual applications of PL, slight increases were observed in soil NO3-N at a depth of 0–20 cm, and extractable P at depths of 20–40 cm and 40–60 cm. No other soil variables were significantly affected by any of the treatments. An additional source of K was found to be necessary to maintain an adequate soil K level.  相似文献   

10.
The distribution of Zn, Cu, Cd, Cr, Pb, Ni, and Mn in the soil, and related soil properties was studied in Abeokuta, southwestern Nigeria. Their soil pollution source was hypothesized to be automobile traffic. Consequently, their variations were assessed as a function of traffic density, distance from road and traffic, and soil depth. Soil samples were collected from the areas of high, medium, and low traffic densities at 0, 50, 100, 150, and 200 m from roadside; at depths 0–20, 20–40, 40–60, 60–80, and 80–100 cm. The potential effects of these metals on environment and agricultural activities were also assessed. Results indicated that the major sources for the metals’ contamination are emissions from vehicles. High and medium traffic volume impacted more metals of the soils. Zinc, Cu, Cd, and Cr were concentrated at depths 0–40 cm, Pb, Ni, and Mn were concentrated at 0–20 cm and appeared bound to soil organic matter (SOM). Significantly lower concentrations of metals are found at distances of 100 m and beyond. Concentrations of these metals are generally low compared with standards and their uptake by crops is not probable. However, their continuous accumulation might be a threat in the future.  相似文献   

11.
The organic carbon (OC) fractions and micronutrient status of soil under cashew (Anacardium occidentale), plantain (Musa spp), oil-palm (Elaeis guineensis) and gmelina (Gmelina arborea) plantations were studied to determine their effectiveness for managing converted forest in the derived savanna ecology of southwestern Nigeria. The control secondary forest soil had statistically similar OC (2.11%) at 0–15 cm with gmelina but significantly higher than those of the remaining plantation crops. At deeper depths, however, the OC content of the control forest was lower than those of other plantation crops. Apart from gmelina, other plantation crops had carbon enrichment ratio (CER) <1 at 0–15 cm. Only gmelina sequestered as much non-hydrolysable carbon (NHC) as the control at 0–15 cm depth. Also it was observed that plantain plantation sequestered higher NHC than the control at 15–30 cm depth. At >30 cm depth, however, none of the plantation crops sequestered as much NHC as the control. Using the average NHC at all the soil depth as a quality index, gmelina has a better potential to sequester NHC than the other plantation crops used in this study.  相似文献   

12.
Cadmium (Cd) sorption and desorption characteristics by Alfisols from different land uses were examined, and the relationships between soil and sorption/desorption characteristics were investigated. Adsorption studies were done using Cd concentrations (0–100 mg Cd kg?1) in 0.01 M CaCl2. The Cd sorbed by the soils was then subjected to two desorption runs. The soils' adsorption conformed to Freundlich and Langmuir equations. The amount of Cd sorbed by the soils varied. Two desorption runs detached more than 95% of sorbed Cd, but the first accounted for more than 80% of the total. Desorption of Cd in degraded soils was more than in soils from other land uses. The amount of Cd desorbed correlated with amount applied (r = 0.90??), solution concentration (r = 0.83??), and amount sorbed (r = 0.70??). A positive relationship exists between the adsorption maxima of the soils and soil organic matter (r = 0.13, p = 0.87). The relationship between amount of Cd desorbed and sorbed is quadratic for all the soil.  相似文献   

13.

Purpose

Land preparation (e.g., leveled ditches, leveled benches, adversely graded tableland, and fish-scale pits) is one of the most effective ecological engineering practices to reduce water erosion in the Loess Plateau, China. Land preparation greatly affects soil physicochemical properties. This study investigated the influence of different land preparation techniques during vegetation restoration on soil conditions, which remained poorly understood to date.

Materials and methods

Soil samples were collected from depths of 0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm, in the typical hilly watershed of Dingxi City, Loess Plateau. Soil bulk density (BD), soil organic matter (SOM), and total nitrogen (TN) were determined for different land preparations and vegetation type combinations. Fractal theory was used to analyze soil particle size distribution (PSD).

Results and discussion

(1) The effect of land preparation on soil properties and PSD varied with soil depth. For each land preparation category, SOM and TN values showed a significant difference between the top soil layer and the underlying soil depths. (2) The fractal dimension of PSD showed a significant positive correlation with clay and silt content, but a significant negative correlation with sand content. (3) The 20 cm soil layer was a boundary that distinguished the explanatory factors, with land preparation and vegetation type as the controlling factors in the 0–20- and 20–100-cm soil layers, respectively.

Conclusions

Land preparation and vegetation type significantly influenced soil properties, with 20 cm soil depth being the boundary for these two factors. This study provided a foundation for developing techniques for vegetation restoration in water-limited ecosystems.
  相似文献   

14.
Fertigation offers vast potential for efficient use of water and nutrients in sustainable orchard management. Beside minimizing losses, their distribution within the rhizosphere is of utmost importance. In present investigations, most of feeder roots were observed within 30 cm soil depth. Under drip fertigation, wetting front extended horizontally up to 45 cm from emitter. However, the maximum moisture content remained confined within 30 cm distance. Vertically, soil moisture also remained higher in the 0–30 cm soil layers. Under surface irrigation, deeper soil layers registered higher moisture content. Available nitrogen (N) and potassium (K) under fertigation closely followed the moisture distribution pattern. Fertigation plus mulch resulted in 20% fertilizer and 15% water savings over fertigation without mulch. Beside 33% higher fruit yield and 25% water savings, and fertigation plus mulch resulted in 20 percent fertilizer and 40% water savings over surface irrigation.  相似文献   

15.
ABSTRACT

Soil and plant samples were collected from on-going long-term experiment at Indian Agricultural Research Institute, New Delhi farm to study the distribution of various forms of copper (Cu) and their contribution to availability and plant uptake in maize (Zea mays L.)—wheat (Triticum aestivum L.) sequence. The optimum dose-based treatments selected for the study were nitrogen-phosphorus-potassium (NPK), NPK + Farmyard manure (FYM), NPK+ zinc (Zn) and control (no fertilizer or manure). Uptake of Cu by maize and wheat varied from 17.0 to 37.5 and 60.8 to 149.3 g ha?1, respectively, under different treatments. Copper uptake by wheat was significantly higher under 100% NPK + FYM than that with 100% NPK. There was no significant difference among the treatments with respect to diethylenetriaminepentaacetic acid (DTPA)-extractable Cu in 0–15, 15–30, 30–45, and 45–60 cm soil layers. However, with increasing depth of soil, it showed declining trend under all the treatments. Mean value of total Cu was 28, 32, 25, and 21 mg kg?1 in 0–15, 15–30, 30–45, and 45–60 cm depths, respectively. Major part of the total Cu was present as residual form. Sorbed copper (SORB–Cu) contributed directly towards its availability both in pre-sowing maize and post-harvest wheat soil samples. SORB–Cu and organic matter bound Cu (OM–Cu) contributed directly towards the uptake by the component crops. Copper associated with easily reducible manganese, carbonate, and iron and aluminum oxides were most recalcitrant forms present in soil and their effects on availability and crop uptake were adverse.  相似文献   

16.
Classical statistical techniques were used to evaluate the lateral and vertical variability of some nutrient constituents, viz. NO3, extractable K and Mg, and organic C, of a loess soil field. In all 50 sites at a 30m × 30m grid were selected within a 10 ha field situated about 25 km west of Hannover. Samples were taken at 0–30, 30–60 and 60–90 cm depths. Analysis based on cumulative probability density function showed that all properties except K in the 30–60 and 60–90 cm depths were normally distributed. K in these depths was lognormally distributed. Mean values of NO3 increased with depth, that of K decreased and that of Mg remained nearly constant. Comparison of coeffizients of variation (CV – % variation) indicated that organic C was least variable laterally (CV = 8.7) and K the most (CV = 43.8 for 30–60 cm depth). The CV of NO3 and Mg increased slightly with depth indicating less drastic vertical variation. The number of observations required to yield an estimate of the mean value within a prescribed accuracy and precision is shown to depend upon the nature and extent of the spatial variability of a parameter. Thus, estimated number of samples was smaller for lower CV values and vice versa. The optimum number of samples for a given property is determined by the depth in which the largest estimated number of samples is required to be taken.  相似文献   

17.
To diagnose sulfur (S) deficiency, methodologies based on soil sample analysis and simulation models have been used, all of which require determination of S availability. The objective was to evaluate the possibility of estimating sulfate concentration up to 60 cm deep, using values from soils 0–20 or 0–40 cm deep as predictive variables. A set of data from 22 fertilization experiments on winter and summer crops was used. For wheat, a close association (P < 0.0001) was determined between sulfate concentrations 0–20 and 0–60 cm deep (r2 = 0.88). When the sulfate concentration at 0–40 cm deep was used as predictive variable, the model r2 increased to 0.97. Similar results were obtained for summer crops (r2 = 0.68 and 0.94 for 0–20 and 0–40, respectively). The integration of all 22 experiments showed two linear models (P < 0.0001) to estimate sulfate concentration up to 60 cm deep (r2 = 0.79 and 0.95 for 0–20 and 0–40, respectively). These results help to simplify soil sampling and would enable more use of S diagnostic methods by producers.  相似文献   

18.
The concentrations of As and Zn in 100 georeferenced soils uniformly distributed throughout the area affected by the spill from the Aznalcóllar mine (April 1998) were analysed at three depths (0–10, 10–30, and 30–50 cm) and on four dates (autumn–winter 1998, 1999, 2001, and 2004). For an estimate of the geochemical background, 30 unaffected soils near the edge of the spill were also analysed at the same depths. The soils were contaminated before the spill and, the accident seriously increased the concentration of As and Zn in the first 10 cm of almost all the affected soils. After the enormous efforts of cleaning up the tailings, around 45% of the soils had a concentration higher than 100 mg As kg?1 dry soil, and some 35% had a concentration higher than 1,000 mg Zn kg?1 dry soil. Both As and Zn penetrated between 10 and 30 cm in 25% and 45% of the soils, respectively, but reached 30 cm in only 12% of the soils. The remediation actions, especially the tilling and homogenisation of the uppermost 25 cm of the all soils, caused the As and Zn concentrations to decline in the soils, but this change was not very effective from the standpoint of pollution. Thus, 6 years after the spill, the uppermost 10 cm of 30% of the soils continued to have an As concentration higher than 100 mg As kg?1, while the Zn concentration diminished considerably on the surface due to its greater mobility, accumulating between 10 and 30 cm in depth, where 20% of the soils continued to register more than 1,000 mg Zn kg?1 dry soil.  相似文献   

19.
The effects of drip fertigation of NPK and vermicompost extract (VCE) on soil fertility status of arecanut-only and arecanut-cocoa systems were assessed in a 4-year field study. In arecanut, soil pH was reduced over initial levels. At 0–30 cm deep, fertigation of 75 percent NPK to arecanut only and organic-matter recycling in arecanut + cocoa maintained significantly greater soil organic carbon (SOC) and soil-test phosphorus (P). At the first depth, soil potassium (K) was significantly greater with 75 percent NPK (246 mg kg?1) than other treatments. In cocoa, soil pH varied significantly due to fertigation at both depths. The SOC was reduced due to 75 percent NPK at the first depth. In cocoa, the P availability increased significantly with application of VCE at 20 percent N. Fertigation of 75 percent NPK maintained significantly greater soil K and soil Mg than other treatments. The results suggest that drip fertigation of NPK sustains the soil fertility status in arecanut and cocoa.  相似文献   

20.
The objective of this study was to quantify inherent spatial variability and spatial cross-correlation of the van Genuchten retention parameters and saturated hydraulic conductivity (Ks) of surface and subsurface layers in a calcareous Inceptisols (Khuzestan province, Iran) under sugarcane cropping. Measurements were performed on 100-cm3 undisturbed soil cores collected at 94 locations along a 30-m-long transect with horizontal sampling distance intervals of 0.3 and 1 m at soil depths of 0–40 and 40–80 cm, respectively. Spatial variability was investigated using conventional statistics and geostatistical techniques. Coefficient of variation (CV) varied from 8.2% (for shape parameter, n at 40–80 cm depth) to 256.7% (for Ks at 0–40 cm depth). The n parameter and saturated water content, θs, showed a small-scale spatial heterogeneity with a maximum CV of 11.3% for the first depth and 9.2% for the second depth. Most of the hydraulic parameters at both depths showed a spatial structure and convex experimental semivariograms with dominant spherical models with the influence range of 3.2–41 m. In most cases, the extent of spatial correlation scales of cross-semivariograms for pairs of cross-correlated hydraulic variables was found to be different with reference to those relating to the direct semivariograms of correlated variables.  相似文献   

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