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1.
Abstract. Nutrient losses from arable land are important contributors to eutrophication of surface waters, and phosphorus (P) and nitrogen (N) usually act together to regulate production of Cyanobacteria. Concentrations and losses of both nutrients in drainage water from pipe drains were studied and compared in 15 crop rotations on a clay soil in southwest Sweden. Special emphasis was placed on P and it was possible to evaluate critical components of the crop rotations by flow-proportional water sampling. Total P concentrations in drainage water were generally small (0.04–0.18 mg L−1), but during two wetter years out of six, high P concentrations were measured following certain management practices, including ploughing-in lucerne ( Medicago sativa L.) and fertilizing in advance without incorporation into the soil to meet the needs of several subsequent crops. This resulted in average flow-weighted concentrations of total P between 0.3 and 0.7 mg L−1. In crop rotations containing green manures, green fallow or leguminous leys, there was also a risk for increased P losses after these crops were ploughed in. The losses increased in the order: cash crops < dairy with grass < dairy with lucerne < monoculture with barley < organic farming with cattle slurry < stockless organic farming with green manure. P balances varied between −9 and +8 kg P ha−1 and N balances between +4 and +35 kg N ha−1. The balances were not related to actual leaching losses. Phosphorus losses in drainage from set-aside were 67–82% of those from cash crops grown in ploughed and P-fertilized soil at the same site, indicating a high background P loss from this clay soil.  相似文献   

2.
Abstract. A set of lysimeter based experiments was carried out during 2000/01 to evaluate the impact of soil type and grassland management on potassium (K) leaching. The effects of (1) four soil textures (sand, loam, loam over chalk and clay), (2) grazing and cutting (with farmyard manure application), and (3) K applied as inorganic fertilizer, dairy slurry or a mixture of both sources were tested. Total K losses in the clay soil were more than twice those in the sand soil (13 and 6 kg K ha−1, respectively) because of the development of preferential flow in the clay soil. They were also greater in the cut treatment than in the grazed treatment (82 and 51 kg K ha−1, respectively; P 0.01), associated with a 63% increase of K concentration in the leachates from the former (6.7 ± 0.28 and 4.1 ± 0.22 mg K L−1 for cut and grazed, respectively; P 0.01) because of the K input from the farmyard manure. The source of fertilizer did not affect total K losses or the average K concentration in the leachates ( P > 0.05), but it changed the pattern of these over time.  相似文献   

3.
Phosphorus (P) losses from intensively farmed dairy pastures can impair surface water quality. One of the first steps in mitigating this loss is to determine where in a field the potential for P loss is greatest. This study compared P export in overland flow from grazed pasture with areas that receive elevated P inputs and stock traffic (e.g. gateway, water trough, stream crossing and cattle lane). Intact soil blocks were removed, simulated rainfall applied and overland flow analysed for P fractions and suspended sediment (SS). Soil bulk density, hydraulic conductivity, porosity, Olsen P and water soluble P were also measured. P loss from the sites was in the order: trough > crossing > gateway > pasture. Total P losses from the trough averaged 4.20 mg P/m2 while the pasture exported 0.78 mg P/m2. In addition, runoff from lane soil was measured with total P averaging 5.98 mg P/m2, however the method used was different from the other soils. Using stepwise linear regression, Olsen P or H2O-P, % bare ground and % saturation were the most commonly occurring variables to predict P loss among the sites. This suggests that locating and minimizing the size of these areas in fields has the potential to significantly decrease P loss to surface waters.  相似文献   

4.
Abstract. The saline–sodic soils of the dryland Songnen Plain in northeast China are only slowly permeable to fresh water because of their large content of montmorillinite clay and sodium bicarbonate. Use of slightly saline groundwater containing adequate dissolved calcium and magnesium for leaching and reclamation can potentially prevent dispersion of the clay soil particles during treatment. Amelioration was evaluated using shallow, mildly saline groundwater to irrigate sorghum–corn rotations in a two-year field experiment. After two growing seasons during which a total of 400 mm of leaching water was applied, in addition to some supplemental irrigation water, the average electrical conductivity (ECe) of the top 1.2 m of the soil profile decreased from 14.5±3.5 to 2.7±0.2 dS m−1, and the sodium absorption ratio (SARe) decreased from 35.3±4.1 to 10.1±2.5 (meq L−1)0.5. The soil physical properties were improved: infiltration rate with mildly saline groundwater increased from 12.1 to 42 mm h−1. Salinity changes in the top 1.2 m of soil layers after 700 mm of leaching produced no further improvement. Crop yields produced on plots undergoing amelioration increased by 64–562% compared with the rainfed control. The improved soil conditions after leaching resulted in 59–548% greater crop yields.  相似文献   

5.
Abstract. The behaviour of potassium (K) in a range of arable soils was examined by plotting the change in exchangeable K of the topsoil (Δ Kex) at the end of a 3–5 year period against the K balance over the same period (fertilizer K applied minus offtake in crops, estimated from farmers' records of yield and straw removal). Based on the assumption that values for offtake per tonne of crop yield used for UK arable crops MAFF 2000) are valid averages, 10–50% of Δ Kex was explained by the balance, relationships being stronger on shallow/stony soils. Excess fertilizer tended to increase Kex and reduced fertilization decreased it, requiring between 1.2 and 5.4 kg K ha−1 for each mg L−1Δ Kex. However, merely to prevent Kex falling required an extra 20 kg K ha−1 yr−1 fertilizer on Chalk soils and soils formed in the overlying Tertiary and Quaternary deposits, despite clay contents >18%. Whereas, on older geological materials, medium soils needed no extra K and clays gained 17 kg K ha−1 yr−1. It is unlikely that the apparent losses on some soil types are anomalies due to greater crop K contents. Theory and the literature suggest leaching from the topsoil as a major factor; accumulation in the subsoil was not measured. Recommendations for K fertilization of UK soils might be improved by including loss or gain corrections for certain soil types.  相似文献   

6.
Phosphorus loss from agricultural soils to water is recognized as a major contributor to eutrophication of surface water bodies. There is much evidence to suggest that liming, a common agricultural practice, may decrease the risk of P loss by decreasing P solubility. An unsaturated leaching column experiment, with treatments of control and two lime rates, was carried out to investigate the effects of liming on P mobility in a low-P acid Irish soil, which was sieved and then packed in columns. Phosphorus was applied at the soil surface in the form of KH2PO4 in solution or as cow slurry. Soil solution was sampled at time intervals over depth and analysed for P fractions. Organic P (OP) was the dominant form of P mobile in soil solution. Liming increased OP mobility, probably through increased dispersion of OP with increased pH. Slurry application also increased OP mobility. Results indicated the potential for OP loss following heavy (100 m–3 ha–1) cow slurry application, even from low-P soils, and suggested that liming may increase this risk. Reactive P (RP) was sorbed strongly and rapidly by the soil and did not move substantially below 5 cm depth. As a result, Olsen-P values in the top 2 cm were greatly increased, which indicates an increased risk of RP loss in overland flow. Lime showed little potential as a soil amendment to reduce the risk of P loss.  相似文献   

7.
Abstract. A long-term lysimeter experiment with undisturbed monoliths studied leaching behaviour and balances of phosphorus (P), potassium (K) and nitrogen (N) during a seven year crop rotation on four types of soil receiving inorganic fertilizers, manure and grass compost respectively. It was shown that application of manure did not lead to any direct change in nutrient leaching, unlike the application of fertilizers to soils of normal fertility. However, soil type considerably affected the nutrient concentrations in the drainage water.
Manure applied in amounts equal to the maximum animal density allowed by Swedish legislation slightly oversupplied P and N (0.5–3.5 and 18–38 kg ha−1 y−1 respectively) compared to the crop requirement and leaching losses for most of the soils. The relationship between lactate-soluble P in the topsoil and the concentrations of dissolved P in the drainage water was very strong. However the strength of this relationship was dependent on just one or two soils. P losses from a fertile sandy soil were large (1–11 kg ha−1 y−1) throughout the crop rotation and average crop removal (13 kg ha−1 y−1) plus the leaching losses were not balanced (average deficit 3–6 kg ha−1 y−1) by the addition of fertilizer, manure or grass compost. No decreasing trend was found in the P losses during seven years. However, the K deficit (average 26 kg ha−1 y−1) led to a significant reduction in the leaching trend from this soil. The other soils that had a smaller K deficit showed no significant reduction in the leaching of K.  相似文献   

8.
Ammonia volatilization from granular urea applied at 10gNm−2 to pasture was investigated using an enclosure method. Misting 0, 4 or 16 mm of water on to the soil at field capacity within 3 h of urea application resulted in total NH3 losses of 2.81, 0.92 and 0.18 g N m−2 respectively. Further delaying the watering reduced this effect until at 48 h, volatilization was lowered from 3.33 to only 3.09gNm−2 with 16mm of water. Hydrolysis and NH3 loss were rapid. Similar trends occurred at a lower initial soil moisture content.
On air-dry soil (0.06 g H2O/g soil), hydrolysis was slow (73 ± 14% of the urea remained after 30 days) and volatilization, while gradual, accounted for 33% of applied urea-N after 30 days. Addition of 16 mm of water 48 and 96 h after urea application was followed by a period of rapid hydrolysis and volatilization, resulting in a total loss of 2.59 and 2.40gNm−2 respectively. Repeated addition of 2mm of water produced bursts of hydrolysis and NH3 loss until completion of hydrolysis when additional water had no effect. A total loss after 30 days of 3.94 g N m−2 occurred in this 2 mm treatment.  相似文献   

9.
Emissions of nitrous oxide (N2O) and nitrogen gas (N2) from denitrification were measured using the acetylene inhibition method on drained and undrained clay soil during November 1980-June 1981. Drainage limited denitrification to about 65% of losses from undrained soil. Emissions from the undrained soil were in the range 1 to 12 g N ha–1 h–1 while those from the drained soil ranged from 0.5 to 6 g N ha–1 h–1 giving estimated total losses (N2O + N2) of 14 and 9 kgN ha–1.
Drainage also changed the fraction of nitrous oxide in the total denitrification product. During December, emissions from the drained soil (1.8±0.6 gN ha–1 h–1) were composed entirely of nitrous oxide, but losses from the undrained soil (2.7 ± 1.1 g N ha–1 h–1) were almost entirely in the form of nitrogen gas (the fraction of N2O in the total loss was 0.02). In February denitrification declined in colder conditions and the emission of nitrous oxide from drained soil declined relative to nitrogen gas so that the fraction of N2O was 0.03 on both drainage treatments. The delayed onset of N2O reduction in the drained soil was related to oxygen and nitrate concentrations. Fertilizer applications in the spring gave rise to maximum rates of emission (5–12g N ha–1 h–1) with the balance shifting towards nitrous oxide production, so that the fraction of N2O was 0.2–0.8 in April and May.  相似文献   

10.
(pp. 825–831)
This study was carried out to clarify the effects of soil nitrate before cultivation and amounts of basal-dressed nitrogen on additional N application rate and yields of semi-forced tomato for three years from 1998 to 2000. The amounts and timing of additional N dressing were determined based on diagnosis of petiole sap nitrate. The top-dressing was carried out with a liquid fertilizer when the nitrate concentration of a leaflet's petiole sap of leaf beneath fruit which is 2–4 cm declined below 2000 mg L−1.
For standard yield by the method of fertilizer application based on this condition, no basal-dressed nitrogen was required when soil nitrate before cultivation was 150 mg kg−1 dry soil or higher in the 0–30 cm layer; 38 kg ha−1 of basal-dressed nitrogen, which corresponds to 25% of the standard rate of fertilizer application of Chiba Prefecture, was optimum when soil nitrate before cultivation was 100150 mg kg−1 dry soil; 75 kg ha−1 of basal-dressed nitrogen, which corresponds to 50% of the standard, was optimum when soil nitrate before cultivation was under 100 mg kg−1 dry soil. A standard yield was secured and the rate of nitrogen fertilizer application decreased by 49–76% of the standard by keeping the nitrate concentration of tomato petiole sap between 1000–2000 mg L−1 from early harvest time to topping time under these conditions.  相似文献   

11.
Characteristics of the treatment processes inside a MSL system were investigated by using a laboratory-scale MSL system, which was set up in a D 10 × W 50 × H 73 cm acrylic box enclosing "soil mixture blocks" alternating with permeable zeolite layers. For the study of the treatment processes inside the system, wastewater, with mean concentrations (mg L−1) of COD: 70, T-N: 12, T-P: 0.9, was introduced into the system at a loading rate of 1,000 L m−2 d−1. Treatment processes in the MSL system were different for the COD, P and N pollutants. Eighty percent of COD was removed in the 1st soil layer among the 6 layers, and the removal rate increased as water moved down and finally reached 90% in the last layer of the system. Phosphorus concentration was lower under the soil mixture layers than under the permeable layers, presumably because P was adsorbed mainly by soil and mixed iron particles. The P concentration in water gradually decreased in the lower layers of the system. The concentration of PO43--P was generally lower in the aerated MSL system than in the non-aerated one. NH4+-N was adsorbed and nitrified in the upper part of the system. The NO3−-N concentration was lower in water under the soil mixture layers than under the permeable layers, indicating that denitrification mainly occurred in the soil mixture layers.  相似文献   

12.
Abstract. Less Intensive Farming and Environment (LIFE) management is a form of integrated farming which aims to meet farming's economic and environmental requirements. We used a farm-scale LIFE demonstration to measure nitrogen (N) leaching losses over a 6 year period (1995–2001) using ceramic suction cups and a meteorological model to give estimates of drainage volumes. Losses from the system averaged 49 kg N ha−1, with an average drainage nitrate concentration of 15.5 mg N L−1. Rainfall and its distribution strongly influenced the loss, and drainage N concentration only fell below the nominal target of 11.3 mg N L−1 (the EU limit for potable water) in the two wettest seasons. Crop type did not have a significant effect on either postharvest mineral N (PHMN) in soil or the leaching loss in the subsequent winter. However PHMN and overwinter N leaching declined with increasing crop yield. Overwinter crop N uptake increased with early sowing: leaching loss was only 5 kg N ha−1 under grass sown in early September. Measurements of PHMN, crop sowing date and drainage data were used to construct simple equations to predict average drainage N concentration under various scenarios. The large N loss from our site is partially attributable to soil type (shallow over limestone), indeed on similar soil the loss from a conventional farm nearby was greater. The LIFE practices of postharvest harrowing and late cereal sowing will minimize the need for agrochemical use but they stimulate mineralization and reduce plant N uptake in autumn, leaving more N at risk to leaching. Some assessment of all environmental impacts is needed if the benefits of integrated practices such as those used in LIFE are to be quantified.  相似文献   

13.
Hydroponically grown barley plants ( Hordeum vulgare L. cv. Minorimugi) under iron-deficient (–Fe) and high phosphorus (P) conditions (500 µmol L−1) showed Fe chlorosis and lower growth compared with plants grown in –Fe and low P conditions (50, 5 and 0.5 µmol L−1). To understand the physiological role of P in regulating the growth of plants in –Fe medium, we carried out an Fe feeding experiment using four P levels (500, 50, 5 and 0.5 µmol L−1) and phytosiderophores (PS), mugineic acid. Our results suggest that plants grown in a high P medium had higher absorption activity of 59Fe compared with plants grown in low P media, irrespective of the presence or absence of added PS. Translocation of 59Fe from roots to shoots was not affected by the P level. The relative translocation rate of 59Fe increased with decreasing levels of P in the medium. In general, the addition of PS enhanced the absorption of 59Fe and its translocation. Taken together these results suggest that the lower relative translocation rate of Fe in high P plants may be induced by the physiological inactivation of Fe in the roots, and the higher absorption activity of Fe in high P conditions possibly results from the response of barley plants to Fe deficiency.  相似文献   

14.
Application of iron (Fe) -rich amendments to soils has been proposed as a means of decreasing phosphorus (P) losses from soils. However, anoxic conditions following soil saturation are known to increase Fe and P solubility in soils, thus cancelling out the potential benefits. Our aim was to evaluate the effects of continuous oxic, continuous anoxic and alternating anoxic/oxic conditions on P exchangeability and Fe forms in soil amended with Ca(OH)2 and FeSO4. We incubated amended and unamended soils under these conditions for 8 weeks and measured Fe forms and P exchangeability. Under oxic conditions, addition of Ca(OH)2 and FeSO4 resulted in a strong decrease in P exchangeability and an increase in oxalate-extractable Fe. Mössbauer analyses suggested that an unidentified Fe oxide (D1oxide) with a strong sorbing capacity for P was precipitated. Under continuously anoxic conditions, P exchangeability and oxalate-extractable Fe increased with or without the amendments. Mössbauer analyses suggested that there was a partial dissolution of the D1oxide phase, precipitation of another unidentified Fe oxide (S3) and a reduction of structural Fe3+ in phyllosilicate, thereby increasing soil negative charge. These transformations resulted in a strong increase in rapidly exchangeable P. Alternating anoxic and oxic periods induced the dissolution and precipitation of iron oxides and the increase and decrease in P exchangeability. Implications of the results for limiting P losses from grassland soils are discussed.  相似文献   

15.
Abstract. Nitrate nitrogen (NO3-N) leaching from animal production systems in the northeast USA is a major non-point source of pollution in the Chesapeake Bay. We conducted a study to measure NO3-N leaching from dairy slurry applied to orchardgrass ( Dactylis glomerata L., cv. Pennlate) using large drainage lysimeters to measure the direct impact of four rates of slurry (urine and faeces) N application (0, 168, 336, 672 kg N ha−1 yr−1) on NO3-N leaching on three soil types. We then used experimentally-based relationships developed earlier between stocking density and NO3-N leaching loss and leachate NO3-N concentration to estimate the added impact of animal grazing. Nitrate N leaching losses from only dairy slurry applied at the 0, 158, 336, and 672 kg N ha−1 yr−1 rates were 5.85, 8.26, 8.83, and 12.1 kg N ha−1 yr−1, respectively with corresponding NO3-N concentrations of 1.60, 2.30, 2.46, and 3.48 mg l−1. These NO3-N concentrations met the 10 mg l−1 US EPA drinking water standard. However, when a scenario was constructed to include the effect of NO3-N leaching caused by animal grazing, the NO3-N drinking water standard was calculated to be exceeded.  相似文献   

16.
Abstract. Phosphorus (P) in overland flow is mediated by soil P, added P, erosion, and hydrological processes and their interaction as affected by landscape position and length of flow. We investigated the effect of flow path length (1 to 10 m long plots) on P transport in overland flow with and without a localized dairy manure application (75 kg P ha–1 added to the upslope end [0.5 m] of each plot) and simulated rainfall (7 cm h–1), at two sites within an agricultural watershed in Pennsylvania, USA. Particulate loss in overland flow was c . 20% greater from manured than unmanured plots due to the less dense nature of manure than soil. Increased soil moisture at Site 2 contributed to a greater loss of P compared to Site 1, both with and without manure; with most occurring as particulate P (60 to 90% of total P). Further, the selective erosion of fine particulates (24 to 34% clay) and P loss increased with plot length. From a management perspective our results demonstrate that the forms and amounts of P loss are greatly influenced by flow path length and interactions among antecedent moisture, soil P, and texture.  相似文献   

17.
Amelioration of a highly alkaline soil by trees in northern India   总被引：2，自引：0，他引：2  
Abstract. A study was carried out to compare the impact of 6-year-old plantations of Prosopis juliflora (Swartz) D.C., Dalbergia sissoo Roxb. Ex. D.C. and Eucalyptus tereticornis Sm. on the physical and chemical properties of sodic soil in the Indo-Gangetic alluvial plains of Uttar Pradesh, India. Soil properties under the three tree species showed significant improvement through a reduction in the pH, electrical conductivity, exchangeable sodium percentage, CaCO3 and gypsum requirement, and by increase in organic C, total N, and available P and K. The six years of reclamation had achieved a marked reduction in exchangeable sodium (from 11.5 to 4.5 cmolc kg−1) to a depth of 1.5 m in the soil profile, whereas the levels of exchangeable calcium, magnesium and potassium had increased. There was also a significant reduction in soil bulk density (from 1.66 to 1.24 g cm−3) and increases in porosity, water holding capacity, field capacity, permeability and infiltration rate. The equilibrium infiltration rate after 455 min increased from 0.03 cm h−1 in the control to 0.13 cm h−1 under P juliflora and D. sissoo and 0.10 cm h−1 under E. tereticornis . It is concluded that salt-tolerant tree species have a significant impact on soil properties, which could help to rehabilitate the sodic wastelands in the region.  相似文献   

18.
The present study aimed to elucidate ammonia (NH3) volatilization loss following surface incorporation (0–15 cm mixing depth) of nitrogen (N) fertilizer in an upland field of light-colored Andosol in central Japan. A dynamic chamber technique was used to measure the NH3 effluxes. Poultry manure, pelleted poultry manure, cattle manure, pelleted cattle manure and ammonium sulfate were used as N fertilizers for basal fertilization to a bare soil with surface incorporation. All three experiments in summer and autumn 2007 and in summer 2008 showed negligible NH3 volatilization losses following the application of all N fertilizers with the same application rate of 120 kg N ha−1 as total N; these negligible losses were primarily ascribed to chemical properties of the soil, that is, its high cation exchange capacity (283 mmolc kg−1 dry soil) and relatively low pH(H2O) (5.9). In addition, the surface incorporation, the very small ratio of ammoniacal N to total N for the manure, and the decrease in soil pH to ≤5.5 following applications of ammonium sulfate were also advantageous to the inhibition of NH3 volatilization loss from the field-applied N fertilizers.  相似文献   

19.
Although iodine is harmful to plants, rice plants ( Oryza sativa L.) absorbed iodine more selectively than bromine. To explain this selective absorption, the authors proposed the following hypothesis based on the fact that the standard redox potential for (I2+ 2e = 2I−) is lower than that for (Br2+ 2e = 2Br−) and (Fe3++ e = Fe2+), and the roots of rice plants are able to oxidize ferrous ion (Fe2+) into ferric ion (Fe3+), namely rice plants oxidize iodide ion (I−) to form molecular iodine (I2) via the oxidizing power of their roots, and absorb the molecular iodine formed more selectively than iodide ion. Bromine, by contrast, is absorbed by rice plants only in the form of ion (Br−). According to this hypothesis, there should be a significant correlation between the oxidizing power of the rice roots and the amount of iodine absorbed. Therefore, the relationship between the oxidizing power of the roots and the concentration of iodine absorbed was studied in a water culture using 8 varieties of rice plants. Rice seedlings, 14 d after germination, were cultured in a solution containing 1 mg L−1 each of iodide and bromide ions for 3 d. The oxidizing power of the rice roots was evaluated based on the amount of 1-naphthylamine oxidized by the roots. A significant correlation (0.78, n = 16, 0.1% significant level) was found between the oxidizing power and the concentration of iodine absorbed by the roots. However, no relationship was found between the oxidizing power of the roots and the amount of bromine absorbed.  相似文献   

20.
Abstract. The effects of especially frequent nitrogen (N) additions (from 1959 to 1986, totalling 860 kg N ha−1) and liming (in 1958 and 1980, totalling 6000 kg CaCO3 ha−1) on CH4 uptake by a boreal forest soil were studied in a stand of Norway spruce. Except for a forested reference plot, the stand was clear-cut in January 1993 and the following year one-half of each clear-cut plot was prepared by mounding. Fluxes of CH4 were measured with static chambers in the autumn before clear-cutting and during the following four summers. The average CH4 uptake during 1993–96 in the forested reference plot was 82 μg CH4 m−2 h−1(ranging from 10 to 147 units). In the first summer after clear-cutting, the cleared plot showed 42% lower CH4 uptake rate than the forested reference plot, but thereafter the difference became less pronounced. The short-term decrease in CH4 consumption after clear-cutting was associated with increases in soil NH4+ and NO3−concentrations. Mounding tended at first to stimulate CH4 uptake but later to inhibit it. Neither liming nor N-fertilization had significant effects on CH4 consumption. Our results suggest that over the long term, in N-limited upland boreal forest soils, N addition does not decrease CH4 uptake by the soil.  相似文献   

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