bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil and vegetation inter‐relationships on reclaimed coal mine sites
Authors: Edwards Linnell M. , Schumacher Alexander E.
Published: February 2007

Abstract. A spoil and vegetation survey was conducted of five fields reclaimed from coal mine spoils seeded in different years at the Whitewood mines of south‐central Alberta, Canada. It aimed to understand the causes of visibly wide variations in ground cover of the seeded species which was mainly alfalfa. Sites were initially stratified into productivity classes: A (high), B (medium), and C (low) based on the seeded species, and then sampled. Cover and dry weight declined linearly with age of reclaimed field. The spoil at class‐A sites contained more clay than that of class‐C sites. It also contained more moisture and a better cover. Electrical conductivity (EC) and the concentrations of soluble B, Mg, Na, and K in the spoil were significantly greater at class‐C sites. Cover and dry weight of the seeded species were negatively correlated with EC, B, Mg, and Na in the spoil, thus implicating these factors in poor vegetative productivity, particularly in the dry conditions that typify this part of Alberta.
Amelioration on some physical properties and nutrient availability of an exposed B horizon of red‐brown earth
Authors: Greene R.S.B. , Wilson I.B.
Published: February 2007

Abstract. Following removal of the upper 40 cm of soil, the physical properties of the exposed B horizon of a red‐brown earth (Goulburn clay loam) were ameliorated using a combination of gypsum (5.4 ha−1) and rye grass. Phosphorus (P), nitrogen (N) and potassium (K) fertilizers were added to improve nutrient availability. The ameliorated properties of the exposed B horizon were compared with those of equivalent depths from an adjacent intact profile of Goulburn clay loam.

Initially, during the establishment phase of the rye grass, the gypsum increased the electrolyte concentration in the 0–10 cm layer, and stabilized the soil surface against mechanical dispersion. After 18 months all the gypsum in the 0–10 cm layer had dissolved. However, in the presence of rye grass, the soil surface was no longer susceptible to dispersion by the mechanical impact of water. The rye grass improved soil physical properties mainly in the upper 20 cm of the exposed B horizon. Water‐stable aggregation > 2000 μm and macroporosity increased, and bulk density and penetrometer resistance of the soil decreased.

Continuous applications of P, N and K fertilizers resulted in a gradual improvement in the nutritional properties of the exposed B horizon. However, because of the large phosphorus adsorption by the exposed clay, 300 kg P ha−1 was required to provide sufficient available phosphorus in the 0–10 cm layer.
Performance of low‐draft tillage implements on a hard setting Alfisol of the SAT in India
Authors: Awadhwal N.K. , Smith G.D.
Published: February 2007

Abstract. Four bullock‐drawn tillage implements (mouldboard plough, chisel plough, sweeps, and shovels) were evaluated on a hard‐setting Alfisol. Measurements included draft requirement, bulk density, cone index, soil crust strength, water content of the plough‐layer and crop yield. Changes in bulk density and cone index due to tillage decreased with time and were negligible by the end of the growing season. After tillage with a mouldboard plough the crust was stronger than after tillage with other implements. The shovel cultivator enabled the soil to store more water, and required least draft per unit effective area of cut.
Leaching of salts from saline clays by subsoiling and induced lateral drainage
Authors: Tanton T.W. , Armstrong A.S.B. , Dervis Ö.
Published: February 2007

Abstract. After restructuring of a heavy saline gypsum containing clay soil by intensive subsoiling to 0.7 m depth, it was possible to leach 60% of the leachable salts from the restructured soil in 28 days by inducing a lateral flow of leaching water through the soil profile.
Agronomic and public aspects of soil nitrogen research
Authors: Hauck R.D.
Published: February 2007

Abstract. Public perceptions of agriculture as a contributor to environmental stress are resulting in changes within agricultural production systems. Increasingly, these systems will need to be economically viable, environmentally sound, socially and politically acceptable, and conserving of natural resources‐the characteristics that describe a sustainable agriculture. Improving and maintaining agricultural production systems with these characteristics must continue to be the objectives of agricultural research. Nitrogen research has contributed markedly to meeting the production and economic goals of agriculture, but it has not yet focused enough on answering socially and politically sensitive questions. Questions are posed about the environmental effects of various nitrogen management practices and the research needed to answer them is outlined. Emphasis is put on immobilization‐mineralization as affected by use of nitrification inhibitors and split‐application, release of nitrogen from animal manures, legumes, and other crop residues, and establishing acceptable yield goals.
The chemistry of biological nitrogen fixation
Authors: Richards R.L.
Published: February 2007

Abstract. Nitrogen‐fixing micro‐organisms contain the metalloenzyme nitrogenase, which can be separated into two proteins with molecular weights of approximately 58000 and 220000. Molybdenum held with iron and sulphide atoms in the cofactor (FeMoco) cluster of the larger protein is probably responsible for binding and reduction of dinitrogen (N2). X‐ray absorption spectroscopy indicates that the moybdenum is surrounded by three oxygen (or nitrogen) atoms, three irons and three sulphurs. Synthetic clusters with similar X‐ray absorption structures to FeMoco do not, however, interact with dinitrogen. Many metal compounds, such as those with tertiary phosphines as co‐ligands, can bind dinitrogen, and some containing molybdenum can also reduce it in acidic solution to produce ammonia via several intermediate compounds. These may be developed for production of ammonia fertilizer.
Ecophysiology of the soil microbial biomass and its relation to the soil microbial N pool
Authors: Killham K. , Schimel J.P. , Wu D.
Published: February 2007

Abstract. Microbial osmoregulation as a factor regulating the nitrogen and carbon contents of soil microbial biomass was studied in two experiments. In the first the percentages of the carbon and nitrogen occurring in the cytoplasm of Aspergillus flavus and Pseudomonas sp. were shown to be strongly influenced by osmotic stress. In the second, biomass carbon and nitrogen initially increased with increasing water stress (osmotic and matric) up to −1.0 and −1.5 MPa, respectively, but declined under greater osmotic stress. As the soil microbial carbon and nitrogen pools are affected by these stresses, allowance must be made for them when interpreting biomass measurements in water‐stressed soils.
Microbiology and chemistry of nitrogen turnover in soils: workshop report
Authors: Beringer J.E.
Published: February 2007

Abstract. The workshops covered various aspects of nitrogen in the environment, with special emphasis on the problems posed by nitrogenous compounds as pollutants.
Estimating soil salinity by disjunctive kriging
Authors: Wood G. , Oliver M.A. , Webster R.
Published: February 2007

Abstract. Disjunctive kriging provides minimum variance estimates of properties from non‐linear combinations of spatially correlated sample data. In addition it can be used to estimate the conditional probability that some critical threshold is exceeded or that there is a deficit at unsampled points. The technique has been applied to estimate and map the salinity of the soil in the Bet Shean Valley of Israel from measurements of electrical conductivity. In November 1985 the estimated electrical conductivity of the soil exceeded 4 mS per centimetre throughout most of the region, and in only a small area was the probability of salinity less than 0.2. By March 1986 the electrical conductivity had declined everywhere to less than 4 mS per centimetre, and the conditional probability of exceeding this value nowhere exceeded 0.25. Despite the fluctuation in salinity farmers seem to have it under control. The results suggest that winter wheat is likely to germinate poorly in the saltier parts of the region and that lucerne (alfalfa, Medicago sativa) is unlikely to yield its maximum over most of it. Cotton, a summer crop sown in spring, should not suffer.
Evaluation of alternative land management and cropping practices for soil conservation
Authors: Edwards K. , Rosewell C.J.
Published: February 2007

Abstract. To allow land planners and managers to assess erosion under alternative management practices a model has been developed. It is based on the universal soil loss equation but uses subfactors for crop cover and management. Readily available agronomic data and field expert opinion were used in formulating the method. Locally‐derived data are used to validate the model which is then applied to agricultural systems in New South Wales, ranking the relative erosion hazard associated with crop and land management practices.
Land use, rainfall and erosion risk on the South Downs
Authors: Boardman J.
Published: February 2007

Abstract. In 1989–90 over 80% of the erosion on agricultural land in the South Downs was on ploughed or cultivated surfaces prepared for spring planting of cereals. This was in contrast to the pattern in previous years when most erosion was in winter cereal fields. An unusual late winter rainfall peak was the primary cause. Periods of erosion risk associated with other land uses on the South Downs are also discussed.
A stochastic‐empirical approach to modelling nitrate leaching
Authors: White R.E. , Magesan G.N.
Published: February 2007

Abstract. Techniques for determining the probability density function (pdf) of travel times of solute molecules through a defined volume of soil, following a pulse or step‐change input to the soil surface, are described. A stochastic transfer function model (TFM) based on the pdf of nitrate travel times works satisfactorily when the nitrate originates from a pulse input of soluble fertilizer to the soil surface. However, a TFM based on the pdf of a surface‐applied tracer, such as chloride or tritiated water, is less satisfactory for simulating the leaching of indigenous soil nitrate. The main problems seem to be the difficulty of estimating mean nitrate concentrations because of the spatial variability of nitrate in field soils, accounting for denitrification during leaching, and the uncertain reproducibility of the soil's transport characteristics, as embodied in its operationally defined fractional transport volume, θst, Nevertheless, for many practical applications, a simplified empirical model which treats the soil's transport volume as a well mixed reactor of average initial concentration C, can provide satisfactory predictions of the quantity of nitrogen leached over extended periods. Irrespective of which model is used, a comprehensive treatment of nitrate leaching, particularly for soil generated nitrate, requires a detailed knowledge of transfers of labile nitrogen within the transport volume, and across its boundaries other than those monitored at the input and output surfaces.
Soil clean‐up policies in the Federal Republic of Germany
Authors: Bachmann G.
Published: February 2007

Abstract. Soil clean‐up policies have been a major focus of environmental concern in the Federal Republic of Germany. With the unification of the two Germanies there is an increased need for these policies. The paper briefly describes the nature of the soil contamination problem, and the development of a soil clean‐up programme. Clean‐up policies are evaluated by comparison with practices in the USA.
Effects of clearfelling on microbial biomass phosphorus in the Oh horizon of an afforested podzol in Mid‐Wales
Authors: Hughes S. , Reynolds B.
Published: February 2007

Abstract. Microbial biomass C and P were monitored in the Oh horizon of an afforested podzol in Mid‐Wales before and after clearfelling. Measurements over a 2‐year period indicated that soil moisture and temperature control the seasonal fluctuations in biomass C in this soil. Clearfelling significantly increased biomass P in the Oh horizon. This was probably caused in part by increased fluxes of organic and inorganic phosphorus from the felling debris and litter horizons of the forest floor.
Deep loosening of clay loam subsoil in a moist climate and some effects of traffic management
Authors: O'Sullivan M. F.
Published: February 2007

Abstract. Two experiments on the same site in different years compared the effects of different intensities of deep loosening on soil properties and crop yield. Both experiments included subsoiling and one experiment, with potatoes, also included double digging and a comparison of conventional and zero traffic. The site was in a moist climate area (S.E. Scotland) on an imperfectly drained Gleysol with a clay loam subsoil. Cone resistance, soil water content and potential, bulk density and crop yield were measured to assess the effects of the treatments. Subsoiling did not loosen the soil very effectively because the subsoil was wetter than the plastic limit at the time of cultivation, even though the growing season prior to subsoiling was drier than average in both years. Double digging was more effective than subsoiling. Zero traffic gave a large yield benefit, especially when combined with double digging. There was no crop response to deep loosening in the presence of conventional traffic. Deep loosening had little effect on the drainage status of the topsoil.
Salinity risks on calcareous soils following pig slurry applications
Authors: Bernal M. P. , Roig A. , Madrid R. , Navarro A. F.
Published: February 2007

Abstract. The electrical conductivity of pig slurry suggests that addition of this waste to soils in arid and semi‐arid areas could cause salinization. Changes in electrical conductivity and soluble salt concentration in two calcareous soils indicated a salinity risk after 24 months of pig slurry addition at rates of 400 m2/ha/yr or more. Salinity risk increased with soil water‐holding capacity. Water‐soluble potassium concentrations showed a greater increase than other cations in the soils because of the large amount present in the slurry. The proportion of soluble potassium in the soil depended on the soil's cation exchange capacity and on the composition of the clay fraction.
Land evaluation using the FAO Framework: an example from Zambia
Authors: Chinene V. R. N.
Published: February 2007

Abstract. The suitability of the University of Zambia farm for selected crops was assessed using the principles and concepts of the FAO Framework for Land Evaluation. Moisture and nutrient availability were found to be the most limiting land qualities, but moisture availability is a more important consideration because the farm is managed with high inputs. Heavy dependence on rainfall makes the farm very vulnerable to drought which has had a devastating impact on yields in recent years.

Soyabean, potato and wheat are the best‐suited crops. Sunflower is not recommended because of the low market value. Maize is not a suitable crop because of its sensitivity to water stress and nutrient availability. Rhodes grass is recommended in mapping units where other crops have little economic value.

The FAO Framework for Land Evaluation can be used in Zambia. It can identify land utilization types that are physically and economically suitable. Based on these findings an appropriate land use plan of the University Farm has been developed and implemented.
A review of soil workability models and their limitations in temperate regions
Authors: Rounsevell M. D. A.
Published: February 2007

Abstract. Soil workability and trafficability are frequently estimated from meteorological data. This paper discusses the importance of soil workability for crop production, and reviews the limitations of various models, especially their applicability for predicting the effects of climate change. Some models calculate the number of spring or autumn work‐days by combining meteorological and soil‐related factors. Most of these determine, either empirically or deterministically, daily soil moisture budgets from which workability is inferred. A shortcoming of this approach is that it requires critical soil moisture contents or potentials. Also there are problems with the persistence of water in the profile and with the allocation of rainfall events to specific days. Determining work‐days over seasonal periods avoids these limitations, but this approach is unsuitable for short‐term planning purposes. The value of workability models is difficult to gauge as they often apply to specific soil and climatic conditions. This limitation will increase under a changing climate. For example, soil properties, previously considered as intrinsic, may alter in a manner that invalidates some models. More work on the soil processes controlling workability is needed, and on how these will be affected by a changing climate.
Use of limestone wastes from metal mining as agricultural lime: potential heavy metal limitations
Authors: Davies B. E. , Paveley C. F. , Wixson B. G.
Published: February 2007

Abstract. Finely ground limestone waste from lead mining is discarded as useless but could be a valuable alternative to agricultural limestone. A glasshouse pot experiment established that it is an effective liming material. Two kinds were used: one from north Wales (HMT) represented metal‐rich waste produced by the older water‐gravity separation of ores; the other (NLB) was a modern flotation tailings. A commercial lime (CLS) was used for comparison. The materials were applied to an acid soil in quantities sufficient to raise the pH to 7 (single liming) and at much greater rates equivalent to annual limings for 369 years. All treatments were replicated five times and the soil/lime mixtures were analysed for EDTA‐extractable lead, zinc and cadmium. Radish was grown as the test plant and hypocotyl and leaf tissue were analysed for the same metals. The larger additions of HMT and NLB caused chlorosis and decreased yields. The cadmium and lead concentrations of leaves and hypocotyls suggested that the HMT material could be safely applied to soil annually for 79 years and NLB for 277 years. It is concluded that NLB can be used as agricultural limestone.
Minimizing nitrate losses from arable soils
Authors: Shepherd M. A. , Davies D. B. , Johnson P. A.
Published: February 2007

Abstract. Recent experiments on soils overlying sand, chalk and limestone aquifers have shown that nitrate leaching losses can be decreased by modifying crop husbandry. Green cover during winter, if established early enough, can reduce nitrate loss. Cultivations can be timed to minimize leaching, and the advantages of irrigation (increased nitrogen offtake and smaller post‐harvest soil mineral nitrogen residues) outweigh the potential disadvantage of increased leaching risk during the growing season. It is important not to over‐fertilize crops. Using these techniques within farm rotations has decreased nitrate losses in small plot experiments. The next step is to measure the effects on commercial farms where the scale of operation might preclude the high level of husbandry that is required for successful nitrogen management.
Soil micromorphology of local authority cricket tables
Authors: Kemp R.A.
Published: February 2007

Abstract. Bulk and undisturbed block samples of soil were collected from beneath five cricket tables and outfields managed by a local authority and used by local league cricketers. Thin sections made from the undisturbed blocks revealed considerable differences in soil structure and composition between the cricket tables. Topdressings of varying textures have been added to all the tables over the years. Texturally‐layered profiles have built up beneath three of the tables because the topdressings have not been mixed. Horizontal organic mats often occur within and between the associated platy aggregates. Rooting is shallow under these tables, and the lower compacted layers often contain evidence for restricted drainage at certain times during the year. At one site, and to a lesser extent at another, greater mixing of the topdressings has been achieved by earthworms, but these seem to have been eradicated at the other sites. Although they create a better plant‐growing medium, the earthworms seem to have had a detrimental effect on the playing quality of the cricket table.
Estimating leaching losses from sub‐surface drained soils
Authors: Magesan G.N. , White R.E. , Scotter D.R. , Bolan N.S.
Published: February 2007

Abstract. Leaching losses of solutes can be calculated if two variables, the amount of water passing through the soil and the concentration of solute in that water (a flux concentration), are known. Two simple approaches, soil extraction and suction cup sampling, were used to estimate the concentration of solutes in the water moving through a silt loam soil. The results were compared with actual concentrations measured in the drainage water from a sub‐surface (mole‐pipe) drained soil.

Seasonal leaching losses were calculated as the sum of the products of estimated monthly drainage and the estimated average monthly solute concentration in the soil solution. These results were compared with the leaching losses measured in drainage water from the mole‐pipe system. For non‐reactive solutes such as bromide (an applied solute) and chloride (a resident solute), the suction cup data provided better estimates of the leaching losses than did the soil extraction data. The leaching losses calculated using volume‐averaged soil solution concentrations (obtained by soil extraction) overestimated the loss for the resident solute, but under‐estimated the loss for the surface‐applied solute. On the other hand, the data for non‐reactive solutes suggest that measurements on suction cup samples may be representative of the flux concentration of a solute during leaching. For nitrate, a biologically reactive solute, there was no clear pattern in the differences between the estimated and measured leaching losses. The flux‐averaged concentration in the drainage water was about midway between those measured in the suction cup samples and in the soil solution.
Prediction of water retention properties of clayey soils: validity of relationships using a single soil characteristic
Authors: Bruand A. , Baize D. , Hardy M.
Published: February 2007

Abstract. Regression equations successfully allowed the calculation of water retained at—0.3 × 105 Pa and–15 × 105 Pa matric potentials from single soil characteristics, such as bulk volume or clay content, in clayey horizons derived in similar ways from a single parent material. It is possible to use these regression equations on other soils with similar clay fabrics. The fabric is expressed numerically using the pore volume associated with clay particles.
Field moisture characteristics of two fersiallitic soils in Zimbabwe
Authors: Twomlow S.J.
Published: February 2007

Abstract. Little is known about the in situ hydrological properties of Zimbabwean soils. This paper describes the water retention and transmission properties of two agriculturally important Zimbabwean fersiallitic soils measured in situ by the instantaneous profile method. The first soil, typical of those used by small scale farmers, is a deep coarse grained granitic sand. The second is a silty clay loam derived from mafic rocks, typical of the red clays associated with Zimbabwe's commercial farming areas. The K‐θ functions for each layer of the sand were very similar and the profile could be described by a single function, with permeability increasing with depth. In contrast, the silty clay loam could not be described by a single function, as permeability decreased with depth. However, in both soils water movement became negligible below a matric potential of—0.01 MPa; this is thought to be a more appropriate field approximation of the upper limit of plant available water than—0.033 MPa which is often used for tropical soils.
Evaluation and mapping of soil erosion susceptibility: an example from Kenya
Authors: Gachene C.K.K.
Published: February 2007

Abstract. The erosion susceptibility of the Erosion Research Farm at Kabete Campus was mapped using a qualitative parametric method. A grid soil survey of the 4 ha farm was combined with a map of slope gradients, slope segments being delineated by breaks in slope. Rainfall erosivity and soil erodibility were also measured. Areas with the greatest erosion susceptibility according to this method were those occupying convex slope positions and slopes of more than 30%. Field observations and soil loss measurements generally supported the erosion susceptibility rating map produced by this method. The soil and erosion susceptibility maps were useful for planning erosion control measures and for selecting suitable sites for runoff plot experiments.
Transforming the spatial basis of agricultural census cover data
Authors: Moxey A. , McClean C. , Allanson P.
Published: February 2007

Abstract. Land cover data from the June agricultural census of England and Wales have historically been published annually at the parish level. This level of spatial resolution masks heterogeneity of land use within parishes, limiting the value of the data for detailed spatial analyses. However, variation in land characteristics across parishes can be used to model variation in land cover, thereby allowing the spatial basis of the census data to be transformed. This procedure, referred to as areal interpolation, is illustrated using two land classification systems based on soils for a study area in northern England. The results indicate that the spatially transformed data offer a better description of the distribution of land covers than that provided by the raw census data. They also demonstrate the extra value that can be obtained by combining extant data sources within a GIS framework. Potential roles for areal interpolation in environmental modelling and policy formulation are discussed briefly.
Development of a rapid field test for soil mineral nitrogen and its application to grazed grassland
Authors: Scholefield D. , Titchen N.M.
Published: February 2007

Abstract. The efficiency with which fertilizer nitrogen (N) is used in agricultural systems might be improved if the amounts applied at each top dressing were adjusted to avoid the accumulation of mineral‐N in the soil profile to levels in excess of the growth requirements of the crop. Such tactical application of fertilizer would be feasible if soil mineral‐N could be determined rapidly in the field with sufficient accuracy. This paper describes a rapid field test for both the ammonium and nitrate components of soil mineral‐N based on reading paper test strips with a reflectometer, recalibrated for use with KC1 solution. The new test is volumetric and also accounts for the effects of fluctuations in soil water content by means of a standard dilution procedure to provide an absolute measure of soil mineral‐N in about one hour. Measurements of ammonium and nitrate in a clay loam soil sampled from grazed pasture were compared with those made by conventional laboratory based methods; they generally differed by less than 5%. The proportion of mineral‐N as ammonium averaged about 50% overall and typically exceeded 70% in spring. Ammonium and nitrate were not well correlated. The use of a filter‐press to expel soil solution increased the sensitivity of the test five‐fold to enable application in studies of soil N transformations in unfertilized and semi‐natural environments.
Contrasts in the physical properties of three soils of an Alfisol catena in Sri Lanka
Authors: Mapa R.B. , Pathmarajah S.
Published: February 2007

Abstract. The agricultural implications of differences in soil physical properties along an Alfisol catena were evaluated. The properties studied were steady infiltration rate, saturated hydraulic conductivity (Ks), available water capacity, bulk density, field air capacity and soil texture. The catena consisted of Rhodustalfs, Haplustalfs and Tropaqualfs. A significant increase in clay content downslope was the major factor influencing the changes in associated soil physical properties. Steady state infiltration rate decreased significantly downslope. The Rhodustalfs occurring at the crest showed a steady infiltration rate of 1.91 cm/h which is optimum for surface irrigation. This decreased to 0.68 cm/h in the Haplustalfs and to 0.29 cm/h in the Tropaqualfs at the bottom of the catena; the last showing suitability for rice cultivation. Ks decreased downslope showing poor soil drainage and aeration in lower horizons of the Haplustalfs and Tropaqualfs. Available water increased downslope from 97 mm/m in the Rhodustalfs to 106 mm/m in the Haplustalfs and 122 mm/m in the Tropaqualfs. These results indicate the importance of the catena approach for soil characterization when planning agricultural projects.
Rock fragments IL Their impact on soil physical properties and biomass production under Mediterranean conditions
Authors: Danalatos N.G. , Kosmas C.S. , Moustakas N.C. , Yassoglou N.
Published: February 2007

Abstract. The effects of rock fragments on soil temperature, soil moisture conservation, night time water vapour absorption and wheat biomass production were investigated. Under conditions of moderate water stress, water conservation was generally greater in the stony soils. Under conditions of pronounced drought the opposite occurred, with stony soils conserving less water than soils free of stones, though soils with large cobbles on the surface conserved the most water.

Stony soils were generally warmer during daytime and cooler at night than soils free of rock fragments. In the warmest month (July) the diurnal amplitude reached 14.3 °C in the control soil and 24.1 °C in the stony soils. Night time absorption of water vapour in the upper 15–20 cm was less for the stony soil (17.8% cobble cover), than for the stone‐free soil. Cobbles on the soil surface increased biomass production by increasing moisture conservation. After removing all the stones from the surface of 16 plots, total dry matter yield of rainfed wheat was on average 20% less than from plots with stones on the surface.
An investigation of the relationship between soil mineral nitrogen in the autumn or spring and optimum nitrogen rate for winter cereals
Authors: Harrison R.
Published: February 2007

Abstract. Data from 143 nitrogen (N) response trials on winter cereals carried out at sites across England during the period 1981–1988 were reviewed. Linear regression models for the relationship between optimum N requirements and soil mineral nitrogen (SMN) were evaluated. Multiple regression analyses and F tests were used to determine whether separate regression lines for different combinations of soil group and N Index, substituting for cropping history, were justified, and whether the additional terms used to account for SMN in the 30–60 cm and 60–90 cm depth bands significantly improved the regression model used to fit the data.

The results indicated that optimum N requirement can be predicted from SMN 0–30 cm and 30–60 cm data. However, although the slope of the regression line does not change for different combinations of soil group and N Index, the intercept does. If no allowance is made for differences between sites which alter this intercept, the amount of variation in optimum N requirement accounted for by the regression models is considerably reduced. Factors which should be considered are mineralization of previous crop residues, organic manures and indigenous organic N, and the depth to which SMN is accessible by plant roots.
Validation of a FAO land evaluation method by comparison of observed and predicted yields of five food crops in Burundi
Authors: Hennebert P.A. , Tessens E. , Tourenne D. , Delvaux B.
Published: February 2007

Abstract. A land evaluation using unsophisticated data successfully predicted yield ranges of various crops in Burundi. Yields of wheat, pea, bean, maize and potato predicted from data for climate, soil and land use technology were compared with observed yields from farm trials and from seed station and research station trials. The predicted range of yield for each crop suitability class enclosed the mean farm yields 13 times out of 16 and yields on seed stations and research stations 10 times out of 15 and 14 times out of 21 respectively. The variability of the observed yields exceeded the predicted range of yields. The method is considered as validated. The method appears to be applicable for multi‐year studies at a broad scale, but yield variation according to the weather from year to year is not accounted for. The variances of the yields on farms are greater than the variances in seed station and research station trials.

Since the method predicts correctly the mean regional farm yields, it could be useful for land use planning, research into optimal regional cropping specialisation, studies on food policy, and for evaluation of economic return and sustainability of different crops.
The effects of nitrogen fertilizer rate, cultivation and straw disposal on the nitrate leaching from a shallow limestone soil cropped with winter barley
Authors: Johnson P.A. , Smith P.N.
Published: February 2007

Abstract. Monoculture winter barley was grown for 5 years with 80 or 160 kg/ha of fertilizer nitrogen (N) and established by either shallow cultivation (straw removed) or ploughing (straw incorporated) in a replicated 2 ± 2 split plot experiment. The lower N rate reduced average grain yield from 6.85 t/ha to 5.61 t/ha. The cultivation/straw disposal system had no effect on yield. Halving the N rate reduced the amount of N removed in the crop by an average of 40 kg/ha and reduced the amount of nitrogen leached by 11 kg/ha per year. Using a shallow cultivation system for crop establishment, following the removal of straw, initially reduced N leaching compared to ploughing in the straw, but in the later years of the experiment losses were similar. Over the five years the full N rate with ploughing system resulted in a small positive nitrogen balance of 66 kg/ha, but all other treatment combinations resulted in a negative balance.
Regional characterization of the long‐term change in soil organic carbon under intensive agriculture
Authors: Van Meirvenne M. , Pannier J. , Hofman G. , Louwagie G.
Published: February 2007

Abstract. To study the change in soil organic carbon (SOC) since it was recorded during the Belgian National Soil Survey some 40 years ago, we recently revisited 939 locations still under use as arable land. The study area comprised almost the entire province of West Flanders (about 3000 km2) characterized by profound changes in its arable land management.

Taking the increased ploughing depth (by 9.8 cm on average) into account, a significant (P= 0.001) increase of the SOC content by 0.2% on average was found. Expressed as an amount, the SOC in the topsoil rose by 9.3 t/ha on average, representing an increase of 25%. This is comparable with the conversion of arable land into grassland for 2 to 3 decades.

Geostatistical tools were used to map the SOC at the two times of observation. These showed that most of the spatial variation occurred within about 4 km. Since the community level is the smallest spatial resolution on which agricultural statistics are gathered officially, a detailed modelling of the change in SOC was impossible. However, by selecting communities with extreme changes in SOC, we found indications that the major source of increase in SOC was due to the large increase in pig breeding.
The spatial variability of soil nitrates in arable and pasture landscapes: implications for the development of geographical information system models of nitrate leaching
Authors: Wade S.D. , Foster I.D.L. , Baban S.M.J.
Published: February 2007

Abstract. In response to the European Community Nitrate Directive (91/676) a catchment scale Geographical Information System (GIS) model of nitrate leaching has been developed to map nitrate vulnerability and predict average weekly fluxes of nitrate from agricultural land units to surface water. This paper presents a pilot study which investigated the spatial variability of soil nitrates in order to: (1) define an appropriate pixel size for modelling N leaching; (2) quantify the within‐unit variability of soil nitrate concentrations for pasture and arable fields; and (3) assist in the design of an efficient sampling strategy for estimating mean nitrate concentrations. Soil samples, taken from two 800 m transects in early September 1994, were analysed for water soluble nitrate. The arable soils had a mean nitrate‐nitrogen concentration of 0.693 μg/g (S.E. 0.054 μg/g) and the pasture soils had a higher mean nitrate‐nitrogen concentration of 0.86 μg/g (S.E. 0.085 μg/g). Spatial variability was investigated using variograms. The pasture data had a weak spatial relationship, whereas the arable data exhibited a strong spatial relationship which fitted a spherical variogram model (r2 0.87), with a range of 40 m. A pixel size of 40 m is suggested for nitrate modelling within the GIS based on the arable variogram and an improved sampling strategy for model validation is suggested, involving bulking sub‐samples over a 40 m grid for estimating mean nitrate concentrations in combined land use and soil units.
The effects of crop husbandry and nitrogen fertilizer on nitrate leaching from a shallow limestone soil growing a five course combinable crop rotation
Authors: Johnson P. A. , Shepherd M. A. , Smith P. N.
Published: February 2007

Abstract. Nitrogen (N) leaching losses from a shallow limestone soil growing a five course combinable croprotation (oilseed rape, wheat, peas, wheat, barley) were measured from 1990 until 1995 using porous ceramic cups, at 60 cm depth, and drainage estimates. The crops were grown with three husbandry systems and two levels of N fertilizer. The husbandry systems were designed to reflect local practice (Standard), the best possible techniques to reduce N loss (Protective) and an Intermediate system which was a compromise between the two. Nitrogen was applied at full and half recommended rates. Drainage started during September in four years and November in one year, with above average drainage in three years. Losses of N were largest after peas (58 kg/ha) and oilseed rape (42 kg/ha), and least (17 kg/ha) before peas sown in spring after a cover crop. Over five years, the Protective management system, which used early sowing and shallow cultivation wherever possible, lost least N (31 kg/ha/y) and the Standard system, with conventional drilling dates and ploughing as the primary cultivation, lost most (49 kg/ha/y). Halving the N fertilizer decreased N loss by 11 kg/ha/y, averaged over the rotation. None of the treatments gave mean drainage water nitrate concentrations of less than 50 mg/l, averaged over the five years. Changes to arable cropping alone will not eliminate the need for other measures to control nitrate concen‐trations in public drinking water supplies.
Gypsum amendment improves native grass establishment on saline‐alkali soils in northeast China
Authors: Suhayda C. G. , Yin Lijuan , Redmann R. E. , Li Jiandong
Published: February 2007

Abstract. Soil salinity and alkalinity reduce plant production and alter species composition of meadow grasslands in western Jilin Province, China. This study was designed to compare the survival and growth of three grass species (Aneumlepidium chinense, Puccinellia tenuijlora and Hordeum brevisubulatum) transplanted into saline‐alkali soils in the field, and to evaluate the effects of gypsum amendments on soil properties and growth of these species. Gypsum treatments decreased soil pH, electrical conductivity, and chloride and sodium levels; water infiltration and calcium levels were increased. Survival of grass transplants was increased by gypsum treatments. Tiller number and height, and grass yields were all increased by the application of gypsum. Improvements in plant growth and survival with gypsum treatment appeared to be due to reduced chloride levels and increased Ca availability in the soil, and to changes in soil structure leading to improved infiltration rates. Revegetation of salinelalkaline soils in this region would be improved by application of gypsum in the range of 14–19 t/ha.
Developing the prerequisites for sustainable land use in Albania
Authors: Zdruli P. , Eswaran H. , Almaraz R. , Reich P.
Published: February 2007

Abstract. When Albania emerged from its seclusion in 1991, the scientific community had its first opportunity to interact with its international counterparts. Soil resource assessment was made with systems developed in the early 1950s, laboratory facilities to provide supporting data were poor, and it was recognized that a new assessment was urgently needed.

The country faces a major challenge in reforestation and soil conservation against a background of overgrazing by sheep and goats and clearing of trees and scrubs for fuelwood. Even orchard and olive trees were used as fuelwood during the winters of 1990 and 1991. Since then, gully and rill erosion has accelerated on many of the sloping lands. In addition to reforestation and conservation measures to reduce the pressures on the sloping land, it is necessary to enhance productivity on the fertile valley bottom soils where most of the agriculture is confined. In the recent past, grain yields have declined due to reduced fertilizer use (low purchasing capacity), and poor management practices. More recently productivity has slowly improved, but land degradation, particularly erosion, has visibly increased.

USDA Natural Resources Conservation Service in collaboration with the Land Resources Institute of Albania, initiated work on a new national soil map through collation of existing information and field studies. The land unit for land use planning, evaluation, and general management decisions, is the Major Land Resource Area (MLRA). Each MLRA encompasses geographically associated soils, the majority of which have broadly similar patterns ofclimate, water resources, and land uses. The MLRAs presented here are based on the soil map of Albania at 1 : 200 000 scale. The MLRA information provides an overview of the landscape and natural resources. It can be used to assess land suitability for various crops, opportunities to achieve self sufficiency in food production, selection of areas for both field crops and highvalue crops for export, and identification of appropriate farming system technologies. Each MLRA will have a set of degradation processes which can be flagged, therefore each of them becomes a unit for decision making with respect to investments in research and mitigating technologies. The task is far from complete. Appropriate databases are needed to support the decisions that are being made at national level. To complement the MLRA and related database, decision support systems are needed for the important task of developing policy options.
Resurrection of Soil Surveys: A case study of the acid sulphate soils of The Gambia. II. Added value from spatial statistics
Authors: Ahmed F. B. , Dent D. L.
Published: February 2007

Abstract. Kriging is used to provide detailed quantitative information for a range of soil characteristics across the floodplain of the River Gambia. Application of spatial statistics to a large area with a coarse grid of data points produces spurious patterns unless the area is first partitioned into soil‐geomorphic mapping units, each of which has a unique pattern of spatial variation. Even combining classical soil survey method with spatial statistics, the large short‐range variability of acid sulphate soils means that single factor maps conceal a large element of uncertainty. A more robust procedure is to map the probability of occurrence of critical values of key characteristics.
Animal manure slurries as a source of nitrogen for cereals; effect of application time on efficiency
Authors: Jackson D. R. , Smith K. A.
Published: February 2007

Abstract. Field experiments undertaken at 14 sites, on a range of soil types, in lowland England, during the cropping years 1989–1993, tested the effectiveness of cattle or pig slurry as a source of nitrogen for cereal cropping. Slurry was applied in autumn, winter and spring, to autumn and spring sown cereal crops. Assessments included slurry nitrogen efficiency relative to N in spring applied fertilizer in terms of both grain yield and grain protein production, apparent crop recovery and content of mineral nitrogen in soil profiles. Crop response to nitrogen was poor at seven sites where high residues of soil mineral nitrogen (SMN) were present. On the seven responsive sites, spring slurry applications proved more efficient (mean 40%) as a source of N than autumn (mean 24%) or winter applications (mean 32%). These differences were smaller than reported in a number of other studies, probably as a result of relatively low excess winter rainfall, resulting in less nitrate leaching during the period of the investigation. Rapid incorporation into the topsoil of slurry applied in autumn, increased (28 kgN/ha) the SMN of samples taken early in the winter. However this increase did not lead to a consistent improvement in crop N uptake. Slurry dressings, whenever applied, can be expected to make a significant contribution to the N requirement of the succeeding crop and need to be taken into account when calculating the appropriate spring fertilizer application.
Soil degradation and desertification induced by vegetation removal in a semiarid environment
Authors: Albaladejo J. , Martinez‐Mena M. , Roldan A. , Castillo V.
Published: February 2007

Abstract. The fragile soils at the transition between semiarid and arid areas are continuously threatened by human activity, which frequently involves the elimination of plant cover. We studied the impact of vegetation removal on soil characteristics in senmiarid Mediterranean Spain using two plots (15 m ± 5 m), installed on a north facing slope of 23%. Vegetation was removed from one of the plots (disturbed plot), and changes in the soil characteristics were compared with an undisturbed control plot. Fifty‐five months after vegetation removal the organic carbon content decreased by 35%, the percentage of stable aggregates by 31% and soil bulk density increased by 8%. The models that best represented the changes of these parameters with time were linear equations. There were no significant differences between the water retention capacity or saturated hydraulic conductivity of the treatments. The rapid loss of soil organic matter and the consequences in terms of physical soil properties were considered to be the main factors in soil degradation. No symptoms of natural recovery were observed in the disturbed plot and the tendency was for a steady deterioration in soil behaviour. This means that human activity or climatic change leading to less vegetation could result in irreversible soil degradation in semiarid areas.