Adverse Soil Conditions Research Articles

Site selection, site preparation, and weed control for Gmelina arborea in western Venezuela

Good site selection, site preparation, and weed control are some of the silvicultural practices that can lead to improved yields, reduced rotation lengths, and increased economic returns for plantations of Gmelina arborea Roxb. (gmelina). Site preparation is the major cost in developing a timber stand and its cost must be carried for the entire rotation. Therefore, it is important to select a cost-effective method that meets the needs of both the site and landowner. Proper site selection for field planting is important due to the influence it has on the development of the plantation. Some of the objectives of site preparation are the reduction of competition, improvement of adverse soil conditions, reduction of future fire hazard and increasing the availability of resources by improving the quality and/or quantity of soil volume exploited by tree roots. The objective of this paper is to review and summarize existing methods of site selection, site preparation and weed control for the establishment of gmelina plantations in west-central Venezuela.

Arbuscular mycorrhizae: interactions in plants, rhizosphere, and soils

Part 1 Interactions in rhizosphere: section summary mycorrhiza-microbe interactions - effect on rhizosphere interactions between arbuscular mycorrhizal fungi and non-symbiotic beneficial microbiota interaction of arbuscular mycorrhiza with nitrogen-fixing bacteria arbuscular-mycorrhiza and plant disease. Part 2 Interactions in soil: section summary influence of edaphic and enviromental factors on arbuscular mycorrhizae influence of adverse soil conditions on the formation and function of arbuscular mycorrhiza arbuscular mycorrhizae - mineral nutrient and water acquisition possible role of arbuscular mycorrhizal fungi in development of soil structure. Part 3 Interactions in plants: section summary plant and fungal responses to colonization cellular and molecular aspects specificity and compatibility in arbuscular mycorrhizal symbiosis physiology of nutrient uptake by arbuscular mycorrhizal fungi.

Mycelial colonization by bradyrhizobia and azorhizobia.

This study examines mycelial colonization of common soil fungi by bradyrhizobia and an azorhizobial strain, resulting in the forming of biofilms. The effects of the fungal exudates on a bradyrhizobial strain have also been investigated. Bradyrhizobia gradually colonized the mycelia for about 18 days, after which the biofilm structures collapsed with the release of the rhizobial cell clusters to the culture medium. The azorhizobial strain showed differential colonization of the mycelia. In general, there were no considerable mycotoxin effects of the fungal exudates on the bradyrhizobial strain used, instead the rhizobial strain utilized the exudates as a source of nutrition. This study indicates that the present microbial association with biofilm formation has important implications in the survival of rhizobia under adverse soil conditions devoid of vegetation. Further, it could have developed an as yet unidentified nitrogen fixing system that could have contributed to the nitrogen economy of soils.

Interaction of Lumbricus terrestris L. burrows with field subdrains : The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

The morphology of Lumbricus terrestris L. burrows was investigated in relation to subsurface tile drain position. The aim was to clarify the causes and consequences of higher densities of L. terrestris previously measured above the tiles at the study site. At two pairs of study pits, the plough layer was removed from a 1 m × 2 m area above the tile and at 8 m distance from it. Burrows of L. terrestris were identified at the plough pan, resident worms removed and burrows cast with dyed fibreglass resin. The resin casts were exposed in the profile, depth and length of casts measured and their connections with tiles recorded. In both above-tile pits, two cases were recorded where the cast burrow ended at the tile surface. These contacts indicate the potential importance of burrows in the conduction of water and solutes from the soil surface layers into the tiles. The mean depth of burrows was 1.0 m (se = 0.024, n = 27) above the tiles and 0.83 m (se = 0.036, n = 12) between the tiles. During adverse soil conditions such as droughts, individuals living near the tiles may gain from the shelter provided by their deeper burrows and this could partly explain the higher population densities above the tiles.

Interaction of Lumbricus terrestris L. burrows with field subdrainsThe 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Summary The morphology of Lumbricus terrestris L. burrows was investigated in relation to subsurface tile drain position. The aim was to clarify the causes and consequences of higher densities of L. terrestris previously measured above the tiles at the study site. At two pairs of study pits, the plough layer was removed from a 1 m × 2 m area above the tile and at 8 m distance from it. Burrows of L. terrestris were identified at the plough pan, resident worms removed and burrows cast with dyed fibreglass resin. The resin casts were exposed in the profile, depth and length of casts measured and their connections with tiles recorded. In both above-tile pits, two cases were recorded where the cast burrow ended at the tile surface. These contacts indicate the potential importance of burrows in the conduction of water and solutes from the soil surface layers into the tiles. The mean depth of burrows was 1.0 m (se = 0.024, n = 27) above the tiles and 0.83 m (se = 0.036, n = 12) between the tiles. During adverse soil conditions such as droughts, individuals living near the tiles may gain from the shelter provided by their deeper burrows and this could partly explain the higher population densities above the tiles.

Influence of adverse soil conditions on the formation and function of Arbuscular mycorrhizas

The majority of plants have mycorrhizal fungi associated with them. Mycorrhizal fungi are ecologically significant because they form relationships in and on the roots of a host plant in a symbiotic association. The host plant provides the fungus with soluble carbon sources, and the fungus provides the host plant with an increased capacity to absorb water and nutrients from the soil. Adverse conditions are a pervasive feature in both natural and agronomic soils. The soil environment is constantly changing with regard to moisture, temperature and nutrient availability. In addition, soil properties are often manipulated to improve crop yields. In many cases, soils may be contaminated through disposal of chemicals that are toxic to plants and microorganisms. The formation and function of mycorrhizal relationships are affected by edaphic conditions such as soil composition, moisture, temperature, pH, cation exchange capacity, and also by anthropogenic stressors including soil compaction, metals and pesticides. Arbuscular mycorrhizal fungi are of interest for their reported roles in alleviation of diverse soil-associated plant stressors, including those induced by metals and polychlorinated aliphatic and phenolic pollutants. Much mycorrhizal research has investigated the impact of extremes in water, temperature, pH and inorganic nutrient availability on mycorrhizal formation and nutrient acquisition. Evaluation of the efficacy of plant–mycorrhizal associations to remediate soils contaminated with toxic materials deserves increased attention. Before the full potential benefits of arbuscular mycorrhizal fungi to reclaim contaminated soils can be realized, research advances are needed to improve our understanding of the physiology of mycorrhizae subjected to adverse physical and chemical conditions. This paper will review literature and discuss the implications of soil contamination on formation and function of arbuscular mycorrhizal associations.

Soil and residue management effects on cropping conditions and nitrous oxide fluxes under controlled traffic in Scotland

Nitrogen from fertilisers and crop residues can be lost as nitrous oxide (N 2O), a greenhouse gas that causes an increase in global warming and also depletes stratospheric ozone. Nitrous oxide emissions, soil chemical status, temperature and N 2O concentration in the soil atmosphere were measured in a field experiment on soil compaction in loam and sandy loam (cambisols) soils in south-east Scotland. The overall objective was to discover how the intensity and distribution of soil compaction by tractor wheels or by roller just before sowing influenced crop performance, soil conditions and production and emissions of N 2O under controlled traffic conditions. Compaction treatments were zero, light compaction by roller (up to 1 Mg per metre of length) and heavy compaction by loaded tractor (up to 4.2 Mg). In this paper we report the effects on production and emissions of N 2O and relate them to soil and crop conditions. Nitrous oxide fluxes were substantial only when the soil water content was high (>27 g per 100 g). Fertiliser application stimulated emissions in the spring whereas crop residues stimulated emissions in autumn and winter. Heavy compaction increased N 2O emissions after fertiliser application or residue incorporation more than light or zero compaction. The bulk densities of the heavily and lightly compacted soils were up to 89% and 82% of the theoretical (Proctor) maxima. Higher soil cone resistances, temperatures and nitrogen availability and lower gas diffusivities and air-filled porosities combined to make the heavily compacted soil more anaerobic and likely to denitrify than the zero or lightly compacted soil. Compaction sufficient to increase N 2O emissions significantly corresponded with adverse soil conditions for winter barley ( Hordeum vulgare L.) growth. Soil tillage, which ensures that soil compaction is no greater than in our light treatment and is confined to near the soil surface, may help to mitigate both surface fluxes of N 2O and losses to the subsoil.

Surface water management under varying drainage conditions for rice on an acid sulphate soil in the Mekong Delta, Vietnam

In the period 1990–1992, three field experiments were carried out to evaluate the effects of (repeated) removal of surface water under varying drainage conditions, with the aim of alleviating suspected Fe toxicity aggravated by H 2S together with Al toxicity. The experiments were carried out on a poorly drained, heavy textured, acid sulphate soil (typic Sulfaquept) of low permeability. The results of the experiments indicate that surface water management can alleviate nutritional disorders and increase yield. These effects are, however, overruled by the influence of the general drainage condition of the land. Evaluation of agronomic and soil chemical parameters indicates that in the Hoa An conditions a percolation rate of 0.8–1.0 mm day −1 appears to be optimal to prevent most adverse soil conditions. A set of practical soil- and water-management measures is presented which can be used to improve the yield under similar hydrological and soil conditions.

Adaptation of green manure legumes to adverse conditions in rice lowlands

Poor adoption of sustainable pre-rice green manure technology by lowland farmers is frequently associated with unreliable legume performance under adverse environmental conditions such as marginal soils, short photoperiod, and unfavorable hydrology. A series of field and microplot experiments were conducted at the International Rice Research Institute (IRRI) in 1991 and 1992 to screen and evaluate 12 promising flood-tolerant legumes for adaptation (N accumulation and biological N2 fixation) to a range of environmental stresses, frequently encountered in rice lowlands. Legumes belonging to the genera Sesbania and Aeschynomene were grown for 8 weeks at 10×10 cm spacing: (1) in a fertile control soil and in four marginally productive irrigated lowland rice soils (sandy Entisol, P-deficient Inceptisol, acid Ultisol, and saline Mollisol); (2) during short- (11.7h) and long-day (12.3 h) seasons in a favorable irrigated lowland soil; and (3) in an aerobic soil (drought-prone rain-fed lowland) and a deep-flood-prone lowland soil (1 week seedling submergence). A large variability in N accumulation was obsersed among legume species and across different environments, ranging from less than 1 to over 70 mg N plant-1. The nitrogen derived from the atmosphere (Ndfa) accounted on average for 82% of total N accumulation. Sesbania virgata was least affected by unfavorable soil conditions but its Ndfa was the lowest among the tested species (less than 60%). Stem nodule formation did not convey a significant advantage to legumes grown under adverse soil conditions. However, flooding reduced N2 fixation less in stem-nodulating than in solely root-nodulating species. Most species drastically reduced N accumulation under short-day conditions. Aeschynomene afraspera and S. speciosa were least affected by photoperiod. The considerable genetic variability in the germplasm screened allows the selection of potentially appropriate legumes to most conditions studied, thus increasing N accumulation in green manures.

Effect of drought stress on survival of clover rhizobia W14-2 and its plasmid-cured derivatives in soil

Little is known on the role of plasmids in the survival of rhizobia under adverse soil conditions. Rhizobium leguminosarum bv. trifolii W14-2 contains four plasmids ranging in size from 260 to 560 MDa. We used plasmid-cured derivatives of the strain, including a plasmidless derivative, to investigate the relationship between plasmid content and survival under drought stress in sterile soil. Plasmids a (260 MDa) and c (350 MDa) contributed to the survival of W14-2 in soil under drought stress, whereas the presence of plasmid d (560 MDa; pSym) was detrimental to the strain. No plasmid-cured derivative performed better than the wild-type at a soil water potential of −7.0 MPa, suggesting that presence of plasmids may be necessary for survival in the field under drought stress.

Performance of contrasting rice cultivars selected for rainfed lowland conditions in relation to soil fertility and water availability

Rainfed lowland rice often experiences severe drought and nutritional problems, and cultivars may respond differently to these adverse growing conditions. Two experiments were conducted with very infertile, sandy soils in Northeast Thailand to determine if cultivars identified to be drought resistant under favourable soil conditions can also produce higher yield than drought susceptible cultivars under poor soil environments. Eight or six contrasting cultivars were grown with or without manure application under rainfed and irrigated lowland conditions. Leaf nitrogen concentration at flowering was mostly less than 1% even with manure application, indicating that the crops in all treatments experienced severe nitrogen deficiency during the later growth stages. Time to flowering was reduced in most cultivars when manure or irrigation was applied. When no manure was applied, grain yield was less than 800 kg ha −1 and there were no significant cultivar differences in either experiment. Application of manure at 6.25 t ha −1 increased yield by up to 900 kg ha −1, even when the plants were water stressed during later growth stages. Also, there were significant cultivar differences with early flowering cultivars producing higher yield under both rainfed and irrigated conditions when manure was applied. Irrigation increased yield by up to 500 kg ha −1, both with and without manure application. Total plant dry matter at maturity responded strongly to manure application and slightly to irrigation, but cultivar differences were rather small. Cultivar differences in grain yield were thus mostly associated with differences in harvest index. It is concluded that drought resistant cultivars may not express their potential advantages when plant growth is severely limited by adverse soil conditions and yield level is less than 1000 kg ha −1. Selection for drought resistance should be conducted in areas where soil conditions, particularly fertility are representative of the region and genotypes should be compared for drought resistance within each phenology group. Early maturing cultivars are suitable for the drought prone environments with low soil fertility particularly if the adverse effect of very low soil fertility is reduced.

THE USE OF LEGUMINOUS TREES IN RECLAMATION OF TROPICAL MINED SOILS

Characterized as vigorous pioneer species which produce large amounts of biomass, forest leguminous trees have shown promise in studies of degraded soil rehabilitation. When associated with atmospheric nitrogen-fixing bacteria and mycorrhizal fungi, these species show superior utilization of nutrients and growth under adverse soil conditions. The objective of this paper is to present the principal results obtained from the Research Program for Use of Nodulated and Mycorrhizal Tree Legume Species in Rehabilitation of Degraded Areas, developed by National Research Center for Agrobiology-CNPAB/EMBRAPA in conjunction with the Federal University of Vicosa, Brazil. The program has been developed in four subprograms: (1) Field surveys to collect and identify native leguminous tree species with potential for land reclamation; (2) Selection to identify more efficient nitrogen-fixing bacteria for each potential species; (3) Greenhouse experiments to evaluate nutritional requirements and capacity to grow in high density soils; and (4) Field experiments in lands degraded by mining.

Drainage models to predict soil water regimes in drained soils: a UK perspective

Drainage is an intervention in the natural hydrology of the soil to alter the duration of adverse (waterlogged) soil conditions. The effects of drainage can be investigated by models that predict the position of the water table at a site in the presence of drainage. An inter-related series of models, which include the van Schilfgaarde non-steady state model, that have been used in the UK for the evaluation of drainage design options, are described. A simplified form of the van Schilfgaarde equation is presented, equivalent to a standard time series model, allowing both the efficient implementation of the model, and the inverse use of the model to derive performance parameters from observational data using statistical methods. A sensitivity analysis is used to investigate the relative importance of the two soil parameters, drainable porosity and soil hydraulic conductivity, on the performance of the model. This shows a far greater effect due to the variation of hydraulic conductivity.

Leguminosas forestales: aspectos relacionados con su nutrición y uso en la recuperación de suelos degradados

Characterized as aggressive pioneer species that produce large amounts of biomass, forest legumes have shown exceptional qualities in studies of rehabilitation of degraded soils. When associated with atmospheric nitrogenfixing bacteria and mycorrhizal fungi, these species show superior nutrient utilization and growth capacity in adverse soil conditions. The objective of this paper is to present the principal results obtained in the Research Program on Use on Nodulated and Mycorrhizal association Legume Species in Rehabilitation of Degraded Areas, developed by Embrapa/CNPAB in conjunction with the Federal University of Vicosa, Brazil. Greenhouse experiments have shown that these species have great tolerance to Al 3+ toxicity and efficient use of K, Ca and Mg. On the other hand, all the evaluated species proved responsive to phosphate fertilization.

Houses with Wet Feet: Ground Water Nuisance and its Abatement in the Netherlands

Nuisance due to high groundwater levels is common in many urban areas in the Netherlands. The combination of adverse soil conditions for drainage, the wet climate and insufficient drainage facilities lead to mildew on walls, a fuggy smell, inaccessible playgrounds, weak road foundations, and so on. Insufficient preparation of the building sites is the main cause of the problems. This is a consequence of the responsibilities for the groundwater control are not clearly defined among the municipality, the inhabitants or others. Agreement on this distribution of responsibilities was recently achieved. Effective methods for designing and implementing a proper drainage system are available, although rather primitive. Data for solving the design problem with more sophisticated methods are, however, rarely available.

Effect of storage temperatures on Rhizobium meliloti survival in peat- and clay-based inoculants

Legume growers and extension agents require advice on optimum conditions under which inoculants may be stored without deterioration of rhizobia or the effectiveness of the inoculant. This study was conducted to determine effects of storage duration and temperature on survival of Rhizobium meliloti in two inoculant carriers, one with a peat base and the other with a clay base. Inoculant subsamples were placed in polyethylene bags, then packaged into plastic containers and stored in wooden boxes at either −23 °C (freezer), 4 °C (refrigerator), or room temperature (21–33 °C). Before and after storage for 0.5, 3, 6, 9, 12, 15 and 20 mo, samples were analyzed for surviving rhizobia by most probable number (MPN) plant-infection technique using plastic pouches with seedlings of alfalfa (Medicago sativa L. ’Algonquin’). These counts showed no significant reduction of rhizobial viability in either inoculant at any temperature over the 20-mo study. The surprising lack of population decreases was attributed partly to the wide span between the confidence limits of MPN estimates (at P = 0.05) and partly to the effectiveness of the protective packaging in preventing any desiccation or acidification of the inoculants. Throughout the experiment pH remained unchanged at 6.8 and 8.5 and moisture content at 12.3 and 3.0% in the peat-base and clay-base inoculants, respectively. Nodule color and size indicated that symbiotic effectiveness was not affected by storage temperature. Counts, when averaged across temperatures, showed rhizobial populations remained constant around 1.3 × 109 cells g−1 peat and 1.1 × 108 cells g−1 clay. Re-testing of R. meliloti inoculants stored for up to 10 yr at 4 °C, after earlier regulatory testing, showed no significant viability reductions in any product stored < 7 yr and in some products stored for as long as 10 yr. The results indicated that rhizobial populations could be maintained at levels much above the regulatory minimum MPN (103 seed−1), which would be of critical importance when forage legumes are grown under adverse soil conditions and inoculation is required. Key words: Rhizobium meliloti, inoculant storage, temperature effects, carrier effects, MPN plant-infection technique, inoculant quality control

Amarelecimento do arroz-de-sequeiro sob condições de encharcamento em solo de baixa fertilidade

Foi realizado um experimento em vasos visando reproduzir sintomas de amarelecimento foliar observados em arroz-de-sequeiro em condições de campo, em Assis (SP), e estudar suas possíveis causas nutricionais. Os tratamentos constituíram-se de areia quartzosa retirada da camada de 0-20 cm, submetida a dois manejos (solo original e solo calcariado e cultivado), dois tipos de irrigação (padrão e excessiva) e quatro cultivares de arroz (IAC-25, IAC-47, Araguaia e Rio Paranaíba). Foram avaliados os sintomas de amarelecimento foliar, o acúmulo de massa seca da parte aérea e de raízes, os teores de macro- e micronutrientes nas folhas e colmos, e estudou-se a anatomia de folhas e raízes. Com a irrigação padrão, praticamente não ocorreu amarelecimento, em ambos os solos. Com a irrigação excessiva do solo original, surgiram sintomas de amarelecimento e aumentos da relação entre a massa seca da parte aérea e das raízes. No solo original, o encharcamento aumentou o teor de Fe em toda a parte aérea e diminuiu os teores de Mn nas folhas e os de Mg nas folhas e nos colmos. No solo cultivado, os resultados foram semelhantes, com exceção do teor de Fe, que diminuiu nas folhas. O 'Araguaia' apresentou menores notas de amarelecimento e tendência de maiores teores de N, P e Ca e foi o único cultivar em que o excesso de irrigação não diminuiu os teores de Mn nas folhas. Observou-se, no limbo foliar das plantas submetidas ao tratamento solo original com irrigação excessiva, que os cloroplastos eram menores, distribuídos na região periférica das células do mesofilo e em menor número do que nos outros tratamentos. Concluiu-se que o amarelecimento ocorreu sob condições de encharcamento e baixa fertilidade natural do solo devido à toxicidade de Fe e à deficiência de Mg na planta, associados a um múltiplo estresse nutricional, e que o cultivar Araguaia se mostrou mais tolerante às condições adversas que induziram o aparecimento dos sintomas.

Stress tolerance in Rhizobium and Bradyrhizobium, and nodulation under adverse soil conditions

Stress tolerance in <i>Rhizobium</i> and <i>Bradyrhizobium</i>, and nodulation under adverse soil conditions

Structural and hydrological changes in a Vertisol under different fallow management techniques

Retention of crop residues (stubble) and zero (or no) tillage are accepted fallow management techniques for reducing erosion of Vertisols in northeastern Australia. However, on some Vertisols these techniques give adverse soil conditions for crop growth. The effect of different fallow management techniques on soil physical properties of one of these soils was investigated. Soil structural and hydrologic properties were determined under three tillage and two stubble fallow management treatments. Measurements were made immediately prior to planting a crop, and some were repeated after harvest. Zero tillage increased bulk density, shear strength, penetrometer resistance and aggregate size (as did stubble retention) at planting, compared with blade or disc plough tillage. These results indicate that seedbed conditions were less favourable for crop establishment under this treatment. Sorptivity, steady-state infiltration rate and curve number values, determined from infiltration of simulated rainfall, were lower in zero tillage treatments, especially where stubble was removed. Infiltration parameters determined with ponded rings and well permeameters were not as sensitive to treatments. Soil moisture characteristics were significantly affected by tillage, with the blade treatment retaining more water at all suctions. Infiltration results were consistent with previous measurements of soil water storage in stubble removed and zero tilled treatments. Macropores (soil cracks or insect and earthworm burrows) were important in infiltration of simulated rain. From the results of this experiment, the favoured fallow management practice for crop production and erosion control in this soil is blade plough tillage with stubble retained.

Effect of seedbed condition on sowing point performance

The performance of different sowing points on a hardsetting red duplex soil at Cowra, New South Wales, Australia was evaluated for a range of initial bulk density and soil strength conditions. The soil was modified by either compressing it with a rubber tyred roller, or cultivating to a depth of 180 mm with a plough fitted with rigid tines spaced 330 mm apart and followed by a light compaction with a Cambridge cultipacker roller. The bulk density of the 0–75 mm soil layer was increased from 1.55 t m −3 to 1.70 t m −3 when rolled, and decreased to 1.38 t m −3 when cultivated and lightly rolled with a cultipacker roller. At the higher bulk density, vane shear strength increased slightly from 52.7 to 58.9 kPa whereas a decrease in bulk density lowered shear strength to 13.4 kPa. Penetration resistance was decreased substantially from 1990 to 393 kPa. The penetration and draft forces of individual points were measured during the sowing operation. The high bulk density level significantly increased the vertical force required for combine sowing points to penetrate the soil surface despite only a slight increase in shear strength and penetration resistance. In contrast, the forces required for both winged and lucerne points to penetrate increased only slightly or not at all. The draft forces of all points increased with increasing bulk density. The combine points had the highest and lucerne points the lowest draft forces. Although the sowing points produced varying degreesof soil disturbance within the seed groove, cultivation of the seedbed prior to sowing was more important for high seedling vigour than the selection of a particular point for the sowing operation. However, the selection of a narrow point (lucerne or winged) under more adverse soil conditions, may improve seeder operation because of the lower penetration forces required for these points, and plant establishment because of the lower soil moisture loss from the seed groove.