Varying Soil Conditions Research Articles

Soil properties impacting denitrifier community size, structure, and activity in New Zealand dairy-grazed pasture

Abstract. Denitrification is an anaerobic respiration process that is the primary contributor of the nitrous oxide (N2O) produced from grassland soils. Our objective was to gain insight into the relationships between denitrifier community size, structure, and activity for a range of pasture soils. We collected 10 dairy pasture soils with contrasting soil textures, drainage classes, management strategies (effluent irrigation or non-irrigation), and geographic locations in New Zealand, and measured their physicochemical characteristics. We measured denitrifier abundance by quantitative polymerase chain reaction (qPCR) and assessed denitrifier diversity and community structure by terminal restriction fragment length polymorphism (T-RFLP) of the nitrite reductase (nirS, nirK) and N2O reductase (nosZ) genes. We quantified denitrifier enzyme activity (DEA) using an acetylene inhibition technique. We investigated whether varied soil conditions lead to different denitrifier communities in soils, and if so, whether they are associated with different denitrification activities and are likely to generate different N2O emissions. Differences in the physicochemical characteristics of the soils were driven mainly by soil mineralogy and the management practices of the farms. We found that nirS and nirK communities were strongly structured along gradients of soil water and phosphorus (P) contents. By contrast, the size and structure of the nosZ community was unrelated to any of the measured soil characteristics. In soils with high water content, the richnesses and abundances of nirS, nirK, and nosZ genes were all significantly positively correlated with DEA. Our data suggest that management strategies to limit N2O emissions through denitrification are likely to be most important for dairy farms on fertile or allophanic soils during wetter periods. Finally, our data suggest that new techniques that would selectively target nirS denitrifiers may be the most effective for limiting N2O emissions through denitrification across a wide range of soil types.

Soil rut depth prediction based on soil strength measurements on typical Estonian soils

Deep ruts in soil hinder the movement of off-road vehicles and harm drastically the soil environment. The aim of this study was to determine the most suitable cone and remoulding index based methods for rut depth estimation for single and repeated military vehicle passage in typical Estonian soils. Cone index based sinkage models – US Army ERDC, Maclaurin (1990) and Willoughby and Turnage sinkage models applicable for military vehicles were tested, using different critical layers (0–15 cm, 7.5–23 cm or 15–30 cm). The test vehicles were a 7 Mg truck and a 23 Mg armoured personnel carrier. At eight experimental sites covering mechanically very variable soil conditions (from peat to clay soil), rut depth was measured after one and ten vehicle passes, cone penetration tests were conducted in situ, and samples were collected for determination of bulk density, organic carbon content, texture, gravimetric water content, plastic and liquid limits of the topsoil and subsoil. According to average RMSD values for military truck the Willoughby and Turnage model was the most accurate prediction method. For one pass and 10 passes the rating cone index values from the 7.5–23 cm and 15–30 cm soil layer, respectively, produced the lowest RMSD values.

Microtremor exploration for shallow S-wave velocity profiles at stations in local strong motion network in Bursa, Yalova, and Kocaeli in north-western Turkey

We conducted microtremor array surveys for shallow S-wave velocity profiles at 20 sites in Bursa, Yalova and Kocaeli provinces in the north-western part of Turkey to provide fundamental data to assess the seismic hazard in the area. All of the measurement sites were positioned very close to strong motion stations belonging to the Disaster and Emergency Management Presidency of Turkey (AFAD) in order to further understand site amplification factors in strong motion records. Of the 20 study sites, two were located in Yalova, four in Bursa and 14 in Kocaeli.We temporarily installed two small arrays to obtain simultaneous records of vertical microtremors. Then, the spatial autocorrelation method was applied to retrieve Rayleigh wave phase velocity curves in a frequency range from 1 to 30 Hz from the array records. The phase velocities in the western part of the Kocaeli area are low across a wide frequency range, while relatively high phase velocities are found in the eastern part of the Kocaeli province. The phase velocities in the Yalova and Bursa provinces are widely distributed suggesting large variations in soil conditions. The observed phase velocity curve at each site was inverted to a one-dimensional (1D) S-wave velocity profile to a depth of 100 m, using a hybrid heuristic inversion method. All the S-wave velocity profiles in the eastern Kocaeli area are similar; however, the sites in the western Kocaeli and Yalova-Bursa areas have profiles with different features from the others.Finally, we discuss amplification factors for S-waves using the inverted profiles. The dominant fundamental periods of the amplification factors were distributed in a frequency range from 0.7 to 5 Hz. The profiles obtained are also used to map average S-wave velocities in the study area, with an addition of existing data at strong motion stations of the AFAD.

Comparative studies of the response of larch and birch seedlings from two origins to water deficit

BackgroundEarly developmental stages of plants are expected to be a major bottleneck to recruitment. Information on the response of seedling to anticipated water availability is urgently needed in regions where tree seedlings may experience more frequent water deficits. In this paper, we focused on the influence of water deficit on different species (larch vs. birch) and origins (xeric vs. mesic).MethodsPrince Rupprecht’s larch (Larix gmelinii var. principis-rupprechtii (Mayr) Pilg.) and white birch (Betula platyphylla Sukaczev) from northern China were selected to represent the xeric origin. Eastern larch (Larix laricina (Du Roi) K. Koch) and paper birch (Betula papyrifera Marshall) from eastern Canada were selected to represent the mesic origin. For each species, half of seedlings were assigned to a well-watered treatment (WW, 75% water holding capacity (WHC) and the other half to a low-watered treatment (LW, 35% WHC). After 20 weeks of treatment, we collected data on morphological indexes of shoot height, root collar diameter, total leaf area and total root area; measured photosynthetic rate (Asat), transpiration rate (E), photosynthetic water-use efficiency (WUE) and apparent chlorophyll concentration (Chl); harvested seedlings and measured biomass allocation of leaf, stem and root.ResultsWe found that reduced photosynthetic rate, transpiration rate and increased water-use efficiency were physiological responses of the four species to drought, and the responses varied among the species. All larch seedlings appeared no leaf shedding, survived through the drought treatment and showed a longer duration and high tolerance to drought. In low-watered conditions, survival rate, biomass, shoot height, root collar diameter, total leaf area, total root area and chlorophyll concentration of birch seedlings were significantly decreased. The response of seedlings to water deficits also differed according to the seed origins. Xeric origin of Prince Rupprecht’s larch was more affected than mesic origin of eastern larch, mainly because Prince Rupprecht’s larch originated in a narrower range of mountainous regions, resulting in lower adaptation of this species to water deficits, whereas eastern larch was distributed widely along coastal regions, contributing to higher phenotypic plasticity to variable soil conditions. Similarly, higher plasticity of paper birch may be responsible for its better performance in the low-watered treatment than white birch.ConclusionsLarch seedlings were less sensitive to water deficit than birch seedlings. Larch seedlings were characteristics of a conservative water-use strategy, whereas birch seedlings responded with a profligate water-use strategy. Plasticity or adaptation of seedlings outweighs the seed origins in determining their drought responses.

Karakter Agronomi dan Daya Hasil Tiga Klon Ubi Jalar Ungu (Ipomoea batatas) di Lahan Masam Lampung

Sweet potato is one of the alternative foods of rice that can be grown on a variety of soil conditions and almost fits on all altitude. Sweet potato clones with purple tuber contains anthocyanins which are antioxidants for our bodies. Purple sweet potato clones include: Varieties Ayamurasaki, Antin and local Purple Lampung. Ayamurasi is the introduction of the Japanese varieties, Antin was the result of the assembly and Purple Balitkabi Malang local is local varieties Lampung. To know the character of the growth and yield of sweet potato are three clones in acidic soil, it is necessary to test for these clones. This study was conducted at California State-owned plantation practices Lampung from May to November in 2011. The study used a randomized complete group (RKTL). Three clones of sweet potato used is Ayamurasaki Clones, Clone-1 and Clone Antin Local Purple Lampung, each repeated 4 times, so there are 12 experimental units. The data were analyzed by analysis of variance, and to know the difference between treatments done LSD a real level of 5% respectively. The conclusion of this research are: 1. There are differences between clones Antin agronomic character-1, Ayamurasaki, and Purple Local Lampung, 2. In acidic soil Lampung, Antin-1 clones are not resistant to stem borer attack and ladybugs (Omphisa anastomasalis), 3. Local Purple Clones Lampung has advantages in production and pest resistance, and has a good adaptation to the acidic soil Lampung, 4. Local Purple Lampung clones producing the highest production which amounted to 878.33 g per plant, followed by clones and clones Ayamurasaki Antin-1, each of which produces a production of 590 g and 166.67 g per plant Keywords: Character, Purple sweet potato, Acidic soil

Characterizing Cereal Rye Biomass and Allometric Relationships across a Range of Fall Available Nitrogen Rates in the Eastern United States

Core Ideas Cereal rye has the capacity for substantial biomass and N accumulation. Cereal rye shoots accumulated roughly 50% of the fertilizer N applied in our study. Cereal rye required 72.4 kg added N ha−1 to reach maximum biomass production. The average maximum biomass was 2853 kg ha−1 at GS25 and 9739 kg ha−1 at GS60. Cereal rye (Secale cereale L.) is widely grown due to its winter hardiness and adaptability to varied soil and environmental conditions. Fall and spring climate and available soil N drive biomass production. However, there is limited empirical information on the effects of these factors on cover crop performance. Farmers need early spring indicators of cereal rye performance to guide management. A 3‐yr experiment was initiated to test and model the effects of climate and soil N fertility on cereal rye growth and allometric relationships in Pennsylvania, Maryland, and North Carolina under five‐six fall fertilizer rates. We hypothesized that allometric relationships between early spring growth indicators can guide management decisions. Measurements included tillering, biomass, tissue N, and normalized difference vegetation index (NDVI) at Zadoks growth stages (GS) 25, 30, and 60. Nitrogen application increased biomass: maximum average biomass was 2853, 4844, and 9739 kg ha−1, respectively, at GS25, GS30, and GS60. At GS25, biomass accounted for the greatest amount of model variation and better predicted GS60 biomass than shoot density and NDVI. Variance attributed solely to GS25 and GS30 biomass constituted 38.5 to 65.2% of total model variance. Models accurately predicted biomass and N accumulation 34 to 60% of the time. This study illustrates the difficulty in predicting late season biomass and N content based on early measurements. One extension of this research would be the development of a simple protocol to accurately sample cereal rye biomass at GS25 to estimate potential N accumulation and biomass at GS60.

The bearing capacity of spudcan foundations under combined loading in spatially variable soils

Predicting the bearing capacity of a spudcan foundation under combined vertical (V), horizontal (H) and moment (M) loads is a challenging problem encountered by geotechnical engineers. In previous studies the combined VHM capacity was defined for a uniform soil profile, ignoring any variability in soil stratification and properties. In offshore conditions, however, both the soil profile and soil properties vary spatially. Therefore, it is of interest to account for the spatial variability of soil in the analysis of the bearing capacity of a spudcan. It is shown in this paper how the spatial variability of a clay affects the bearing capacity of a deeply buried spudcan foundation under combined loadings. Three-dimensional random fields are generated to model the spatial variability of undrained shear strength of clay and combined with a non-linear finite element analysis to investigate and define the VHM failure envelope of a spudcan foundation. Because of the random nature of soils VHM failure envelopes of different probability of occurrence are proposed. Results from this study provide guidance to the practical assessment of spudcan foundations in spatially varied soil conditions that can be encountered offshore.

Microtremor Array Measurements for ShallowS‐Wave Profiles at Strong‐Motion Stations in Hatay and Kahramanmaras Provinces, Southern Turkey

Abstract We conducted microtremor array exploration of shallow S ‐wave velocity profiles at 28 sites in Hatay and Kahramanmaras, in the southern part of Turkey, to provide fundamental data to assess seismic hazards in the two areas. A total of 16 and 12 sites were located in Hatay and Kahramanmaras Provinces, respectively. We temporarily installed two small arrays to obtain simultaneous records of vertical microtremors. The spatial autocorrelation method was applied to retrieve Rayleigh‐wave phase velocity in a 1–30 Hz frequency range. The phase velocities at most of the sites in Kahramanmaras Province were high in the entire frequency range, whereas those in Hatay Province were widely distributed, suggesting significant variation in soil conditions. Low‐phase velocities were identified at sites near the coast in Hatay. Subsequently, the phase velocity observed at each site was inverted to a 1D S ‐wave velocity profile to a depth of 100 m using a hybrid heuristic inversion. Most of the profiles in Kahramanmaras had very thin near‐surface layers with S ‐wave velocities of less than 300 m/s and thicknesses of less than 10 m. The top layers at the sites in Hatay showed significant variation, with different S ‐wave velocities from 110 to 760 m/s and thicknesses from 2 to 40 m. These layers were thicker at the sites near the coastal area. We finally discuss amplification factors of S waves using the inverted profiles. The fundamental predominant periods of the amplification factors distributed across a wide frequency range from 0.8 to 10 Hz in Hatay. The peak frequencies concentrated in a high‐frequency range of more than 5 Hz in Kahramanmaras. The profiles observed were used to map average S ‐wave velocities in the top 30 m at strong‐motion stations.

What is the use of the research carried out on the permanent plots in the Białowieża National Park?

Abstract The purpose of the strictly protected area of the Białowieża National Park (BNP) established in early 1900s, was to protect a compact block of the Białowieża forest from any direct human influence and activity. Its founders considered it a ‘laboratory of nature’ In 1936, five rectangular plots with a total area of 15.5 ha (ca. 0.3% of the BNP) were set up for regular monitoring of stand development with regards to the initial state and variability of soil conditions. During the first 76 years of the project, a steady increase in the proportion of hornbeam and lime tree at the expense of shade-intolerant species was observed. This trend has been interpreted by the researchers involved in the monitoring of the permanent BNP plots to constitute a biodiversitythreatening development caused by preservation efforts. Such an interpretation has been widely incorporated in the public debate by political authorities and the forestry sector. In this critical article I challenge the major arguments presented by the key expert in silviculture, Prof. B. Brzeziecki. My criticism is directed at the methodological approach as well as at the data interpretation.

Engineered metabarrier as shield from seismic surface waves

Resonant metamaterials have been proposed to reflect or redirect elastic waves at different length scales, ranging from thermal vibrations to seismic excitation. However, for seismic excitation, where energy is mostly carried by surface waves, energy reflection and redirection might lead to harming surrounding regions. Here, we propose a seismic metabarrier able to convert seismic Rayleigh waves into shear bulk waves that propagate away from the soil surface. The metabarrier is realized by burying sub-wavelength resonant structures under the soil surface. Each resonant structure consists of a cylindrical mass suspended by elastomeric springs within a concrete case and can be tuned to the resonance frequency of interest. The design allows controlling seismic waves with wavelengths from 10-to-100 m with meter-sized resonant structures. We develop an analytical model based on effective medium theory able to capture the mode conversion mechanism. The model is used to guide the design of metabarriers for varying soil conditions and validated using finite-element simulations. We investigate the shielding performance of a metabarrier in a scaled experimental model and demonstrate that surface ground motion can be reduced up to 50% in frequency regions below 10 Hz, relevant for the protection of buildings and civil infrastructures.

Yield gap analysis in oil palm: Framework development and application in commercial operations in Southeast Asia

Narrowing the gap between actual and attainable yields in existing oil palm plantations is perceived as a key to fulfill the growing global demand for vegetable oil. To assess the scope for intensification we need robust estimates of attainable yields, which has been so far rarely done for perennial crops. For this purpose, we evaluated the complexities associated with estimating yield gaps (YGs) in oil palm (i.e. carry-over effect and aging), and adapted the existing framework for YG studies in annual crops. Based on this framework, we analyzed YGs for four sites within oil palm plantations located in Sabah (Malaysia), Central Kalimantan and North Sumatra (Indonesia) using a unique commercial yield data set covering an area of 38,300ha.We assessed for each site at plantation scale water-limited potential yield using the PALMSIM simulation model, attainable yield determined by best performing blocks within the plantation as defined by 90th percentile of observed yields and actual yields (blocks representing the median yields). The water-limited potential yield did not differ very much; 35–39t fresh fruit bunch (FFB) during the plateau phase, the most productive phase in the life time of a palm. This reflected the favorable environmental conditions found in many parts of Sumatra and Borneo for oil palm. Attainable yields were in the range of 26–31tFFB/ha. The exploitable YG between attainable and actual yield ranged for the four sites from 5 to 7tFFB/ha/year. For one site (Central Kalimantan), we assessed yield variability due to varying soil conditions at the block scale according to its dominant soil type. This suggested that they were indeed exploitable by management. If the plantation could close the gap between attainable and actual yield this could give about 21,000t/yr higher FFB. This indicated the large scope for intensification oil palm offers in many parts of insular Southeast Asia.

Does P deficiency affect nodule bacterial composition and N source utilization in a legume from nutrient-poor Mediterranean-type ecosystems?

Virgilia divaricata is an indigenous forest margin legume growing in nutrient richer soils, but it is also known to invade the N and P poorer soils of the mature fynbos, a nutrient-poor ecosystem in the Cape Floristic Region of South Africa. Although this implies that the legume has a wide functional tolerance for variable soil N and P levels, it is not known how the plant utilizes inorganic N under variable P supply. The aim of this experiment was therefore to identify the nodulating bacterial species and their biological N2 fixing (BNF) efficiencies in V. divaricata during P deficiency. Furthermore, the aim was to integrate plants C and N metabolism to the N product exported via xylem to the shoots. Plants were grown at high and low P levels, both the high and low P plants were then supplied with either 500 μM NH4NO3 as soil nitrogen (N) source or exclusively relied on BNF. Although the bacterial composition of nodules remained seemingly unchanged by P and N supply, the nodule function was greatly altered. In this regard, plants reliant on only N2 at both P levels had higher and more efficient BNF, which resulted in greater plant N. This may have resulted from two physiological strategies at high and low P, when plants relied only on N2 fixation. The declines in both sugars and organic acids may imply a reduced energy supply to the bacteroid during P stress. Furthermore altered bacteroid function may be inferred from BNF, and the N compounds synthesized and exported. At high P, plants exported more amino acids relative to inorganic N and ureides in their xylem sap, whereas at low P the plants exported more ureides relative to amino acids and NH4. The bacterial tolerance for changes in P and N via nodule metabolites and xylem export might be a major factor that underpins the growth of V. divaricata under these variable soil conditions.

King Grass: A very promising material for the production of second generation ethanol in tropical countries

King Grass is a fast growing, high yield, hybrid grass that grows in a variety of soil conditions and does not compete with food crops. King Grass is perennial and can be harvested several times per year. Therefore it has a high potential for ethanol production in tropical countries. The pretreatments alkaline delignification (66.6–133 °C, 30–180 min, solid to liquid ratio 1:13.3–1:20 wt and NaOH concentration 0.7–2% wt), diluted acid hydrolysis (2% wt sulfuric acid, solid to liquid ratio of 1.0 g biomass/mL solution, stirring at 90 °C for 90 min), steam explosion (at 180 °C for 5 min, i.e., severity 3.05), alkaline peroxide (2% vol. H2O2, liquid to solid ratio of 20:1 wt, pH 11.5, stirring at 35 °C for 3 h) and aqueous ammonia soaking (15% wt ammonia solution, 8 mL of ammonia solution per gram of material, at 60 °C for 6 h) were studied. The alkaline pretreatment with NaOH led to the highest concentration of reducing sugars, i.e., 58.6 g/L, and to the highest ethanol concentration, i.e., 17.9 g/L. A more detailed study of the effect of the alkaline pretreatment conditions (temperature, solid to liquid ratio, NaOH concentration and residence time) on the production of ethanol from King Grass was carried out. Under pretreatment conditions of 120 °C for 1 h with 2% wt NaOH and a solid to liquid ratio of 1:20 the highest ethanol yield reported so far was obtained, i.e., 27.7 g/L (165.9 mg ethanol/g dry biomass, 92% of theoretical yield). Furthermore, this pretreatment allowed the removal of most of lignin present in King Grass, i.e., 94%, and allowed a high recovery of the cellulosic fraction in the solid (93–99%). Under typical growing conditions of King Grass in Colombia this maximum ethanol yield corresponds to 12,616 L/ha/year which is higher than that obtained from sugar cane bagasse (4602 L/ha/year).

Heat Recovery from Exhaust Air as a Thermal Storage Energy Source for Geothermal Energy Piles

In pursuit of EU directive 2010/31/EU energy performance targets towards design of nearly zero-energy buildings consideration of renewable energy sources in the design is expected. Application of ground-source heat pump (GSHP) and energy piles in cold climate conditions for utilization of renewable geothermal energy may results in GSHP plant high seasonal coefficient of performance (SCOP) as long as source of thermal storage is considered in plant design. This numerical study investigates exhaust air of air handling unit (AHU) as a source of thermal storage for geothermal plant with energy piles, that can be utilized via air-to-liquid heat exchanger installed at the exhaust side of AHU after the rotor heat exchanger and exhaust fan. Modelling is performed in dynamic whole year simulation environment Equa IDA-ICE, where reference commercial hall-type building model is coupled with detailed custom heat pump plant. Exhaust air thermal storage capacity in multiple energy piles field configurations with varying soil conditions, distance between piles and pile lengths is analyzed. Results revealed that exhaust air thermal storage appears to be highly cost effective solution. Graphical figures presented in this paper can be further applied for preliminary exhaust air thermal storage capacity assessment in buildings with energy piles.

Estimation of the hydraulic conductivities of lupine roots by inverse modelling of high-resolution measurements of root water uptake.

Background and Aims Radial and axial hydraulic conductivities are key parameters for proper understanding and modelling of root water uptake. Despite their importance, there is limited experimental information on how the radial and axial hydraulic conductivities vary along roots growing in soil. Here, a new approach was introduced to estimate inversely the profile of hydraulic conductivities along the roots of transpiring plants growing in soil. Methods A three-dimensional model of root water uptake was used to reproduce the measured profile of root water uptake along roots of lupine plant grown in soil. The profile of fluxes was measured using a neutron radiography technique combined with injection of deuterated water as tracer. The aim was to estimate inversely the profiles of the radial and axial hydraulic conductivities along the roots. Key Results The profile of hydraulic conductivities along the taproot and the lateral roots of lupines was calculated using three flexible scenarios. For all scenarios, it was found that the radial hydraulic conductivity increases towards the root tips, while the axial conductivity decreases. Additionally, it was found that in soil with uniform water content: (1) lateral roots were the main location of root water uptake; (2) water uptake by laterals decreased towards the root tips due to the dissipation of water potential along the root; and (3) water uptake by the taproot was higher in the distal segments and was negligible in the proximal parts, which had a low radial conductivity. Conclusions The proposed approach allows the estimation of the root hydraulic properties of plants growing in soil. This information can be used in an advanced model of water uptake to predict the water uptake of different root types or different root architectures under varying soil conditions.

A high-throughput method to quantify root hair area in digital images taken in situ

Background and aims Root hair growth and development are important features of plant response to varying soil conditions and of nutrient and water uptake. Most current methods of characterizing root hairs in the field are unreliable or inefficient. We describe a method to quantify root hair area in digital images, such as those collected in situ by minirhizotron systems.

Variation In Old-Growth Coast Redwood (Sequoia sempervirens) Reference Sites In Mendocino County, California

Abstract Restoration and management of old-growth conditions in coast redwood (Sequoia sempervirens [D. Don] Endl.) forests are traditionally based on an idealized set of characteristics that occur in productive stands. We compared three old-growth sites to quantify variability among remaining reference stands of the central coast redwood range in Mendocino County, California. Two of the sites are protected from coastal influence, have rich alluvial soils, and relatively high visitor usage. The third site is in close proximity to the coast with variable soil conditions and little visitor access. We randomly sampled twenty, 20-meter circular diameter plots in each site to evaluate basal area, tree density, species richness, canopy cover, shrub cover, and herbaceous species cover. We conducted multivariate analyses including nonmetric multidimensional scaling (NMDS), perMANOVA, and indicator species analysis (ISA) to examine the structural clustering and compositional metrics among the sites. Results indica...

Doubled-up legume rotations improve soil fertility and maintain productivity under variable conditions in maize-based cropping systems in Malawi

Smallholder farmers in Malawi must cope with small farm size, low soil fertility and production risks associated with rainfed agriculture. Integration of legumes into maize-based cropping systems is advocated as a means to increase production of diverse nutrient-dense grains and improve soil fertility. It is difficult to achieve both aims simultaneously, however. Short-duration grain legumes rarely produce enough biomass to appreciatively improve soils, and long duration pigeonpea, commonly grown in Malawi as a dual purpose crop, produces little or no edible grain as a consequence of grain-filling into the dry season. A novel technology is the doubled-up legume rotation (DLR) system in which two legumes with complementary phenology are intercropped and grown in rotation with maize. Initial performance from on-farm research is favorable; however, it is crucial to understand competition for resources in mixed cropping systems under variable soil and climate conditions. We used soil and crop yield data from farmer participatory trials to parameterize the Agricultural Production Systems Simulator (APSIM) and evaluate its performance in simulating observed treatments at three locations in central Malawi. We used the calibrated APSIM model to investigate the performance of DLR and other maize-based systems across 26 growing seasons (1979–2005) in the three agroecologies. We simulated two DLR systems (maize rotated with a groundnut/pigeonpea or soybean/pigeonpea intercrop), maize rotated with groundnut or soybean, maize intercropped with pigeonpea, and continuous maize under a range of N fertilizer inputs. We extended findings to the household level by determining calorie and protein yields of these systems, and calculating the chance that an average household could meet their food requirements by dedicating all available farmland to a given system. Simulated maize grain yields in DLR and maize-grain legume rotations were essentially equivalent, and exceeded yields in maize/pigeonpea intercrop and sole cropped maize receiving comparable fertility inputs. All rotation systems were more likely to meet household calorie and protein needs than other systems receiving equivalent inputs. DLR systems accumulated higher total soil C and N over time than traditional rotation systems in areas where pigeonpea performed well. However, the effects of improved soil fertility on maize yields were counterbalanced by factors including N immobilization and water availability. We conclude that where growing conditions allow, DLR can harness the complementary phenology of pigeonpea to build soil quality for the future without reducing maize yields or compromising household food production in the immediate term.

A role for liming as a conservation intervention? Earthworm abundance is associated with higher soil pH and foraging activity of a threatened shorebird in upland grasslands

The relationship between farmland bird populations and agricultural intensification has been well studied. However, the impact of variation in soil conditions and soil management is an exception, especially in upland (sub-alpine) farming systems. In this study, we examined the relationships between liming history, soil pH and patterns of foraging by Northern Lapwing, Vanellus vanellus, chicks in order to test the potential utility of soil amendment as a conservation intervention for shorebirds nesting in agricultural grasslands. Limed fields had higher soil pH than unlimed fields, and soil pH declined with the number of years since a field was last limed. The most important predictor of total earthworm abundance was soil organic matter with very few earthworms in peats of very high organic matter content. However, there was a marked additive effect of soil pH with earthworms more than twice as abundant at high (pH 6.0) as at the low (pH 3.5) extremes of soil pH recorded in the study. Specifically, at Lapwing chick foraging locations, the density of Allolobophora chlorotica, an acid-intolerant species of earthworm found just below the surface of the soil, was significantly higher than at randomly selected locations. These results suggest that liming helped to maintain breeding habitat quality for Lapwings and other species dependent on earthworms. This is of conservation significance in upland agricultural grasslands in the UK, where there has been a long-term reduction in agricultural lime use since the mid-20th century. Field-scale trials of liming would be valuable to test whether targetted amendment of soil pH in agriculturally improved grasslands could retain an important role in conservation management for shorebirds in upland landscapes where geology, high rainfall, and leaching tend to acidify soils over time.

Modeling of particulate matter transport in atmospheric boundary layer following dust emission from source areas

Abstract A two-dimensional model for particulate matter (PM) dispersion due to dust emission from soils is presented. Field experiments were performed at a dust source site (Negev loess soil) with a portable boundary layer wind tunnel to determine the emitted PM fluxes for different wind speeds and varying soil conditions. The numerical model is formulated using parameterizations based on the aeolian experiments. The wind velocity profiles used in the simulations were fitted from data obtained in field measurements. Size distribution of the emitted dust particles in the numerical simulations was taken into account using a Monte Carlo method. The PM concentration distributions at a distance of several kilometers from the dust source under specific shear velocities and PM fluxes from the soil were determined numerically by solving advection–diffusion equation. The obtained PM 10 concentrations under typical wind and soil conditions are supported by PM data recorded over time in a standard environmental monitoring station. The model enhances our capacity of quantification of dust processes to support climate models as well as health risk assessment.