Soil Physical Conditions Research Articles

The Combine Effect of Grasscutter (Thryonomys swinderianus) Manure and NPK Fertilizer on Soil Properties, Growth and Yield of Carrot (Daucus carota)

The use of inorganic fertilizer to produce most vegetables in Ghana like carrot is in ascendency in Asante Mampong and its environs and its continuous use has a rippling effect on soil health and productivity and the high cost of these fertilizers is a challenge to most poor resourced farmers in Ghana. A field experiment was conducted during the major raining season in 2010 at the University of Education Winneba, Faculty of Agriculture Education research field at Mampong in the forest-transitional zone of Ghana on the Bediase series. The objective of the study was to evaluate the effect of grasscutter manure in combination with NPK fertilizer on soil physical and chemical properties, growth and yield of carrot. The treatments were 300 kgNPK/ha, combination of half rate NPK fertilizer and different rates of grasscutter manure (GM) thus; (5tGM1/ha+150 kgNPK, 7.5tGM2/ha+150 kgNPK and 10tGM3/ha+150 kgNPK/ha) and control (without amendment) and the experiment was laid out in a randomized complete block design with 3 replications. Results indicates that application of grasscutter manure in combination with NPK fertilizer significantly improved the soil physical conditions particularly, soil bulk density, total porosity, and gravimetric moisture content than the NPK alone and the control. Compared with the control, the treatment combinations significantly increased soil organic carbon, N, organic matter concentrations and exchangeable cations. Plant height, number of leaves, tap root length and root yield of treatment combinations were higher than NPK and the control. Also the treatment combinations significantly reduced nematode presence and number of roots deformed. For good soil health, grasscutter manure in combination with NPK would be better than either manure or NPK alone.

Studi Biofisik pada Lanskap Hutan Rawa Gambut di Taman Nasional Sebangau: Kasus di Resort Mangkok

Fire and illegal logging are main causes of peat swamp forest (PSF) degradation. Degradation causes biotic and abiotic changes of PSF. This reasearch was designed to collect data on description of species composition, carbon stock, soil physical factors, and soil macrofauna as indicators of changes in land condition due to PSF degradation. This research was conducted on degraded PSF area caused by fire and illegal logging. Sample plots were located based on the distance from the river i.e., <1.5; <4; and <10 km. Parameters measured included species composition of the stands and their ecological indices, carbon stock potention, soil physical condition (density), and soil macrofauna diversity. Research results showed that all of the parameters in those three locations were not significantly different. Based on those conditions, the main causes of degradation gave the same effects (biotic and abiotic changes) in the very ranged area with 10 km distances. These results were caused by the condition that all parameters measured were very sensitive to changes occurred in all experimental location.

Effect of Soil Preparation and Layers on the Weighted Mean Diameter and Geometric Mean Diameter of a Red Distroferric Latosol

The objective of this work was to study the influence of three management systems on the physical attributes and productivity of irrigated wheat, cultivar BRS-254, in the city of Tangara da Serra, MT. The soil physical attributes were: weighted mean diameter (DMP) and geometric mean diameter (DMG). The experimental design was in randomized blocks. The treatments for weighted average diameter (WMD) and geometric mean diameter (DMG) were arranged in a subdivided plot scheme, with eight replications. The tilting preparations obtained the highest DMPs compared to SD both in the 0-10 cm layer and in the 10-20 cm layer, a result possibly related to the incorporation of residues during the soil preparation associated with higher mucilage production promoted by higher activity of the root system of the crop, which found better soil physical conditions for its development. The PC presented a reduction in DMP when comparing the value in the 0-10 cm layer with the value in the 10-20 cm layer. The significant effect of soil preparation on DMG can also be a result of the incorporation of residues during the preparation, associated to the effect of higher root volume promoted by the higher root growth of the crop in these preparations, which, in turn, guarantee greater production of mucilages promoting greater soil aggregation and higher DMG. The use of the disk grid in the PC and PM interferes with the soil attributes. Soil inversion provided higher WMD and DMG.

Limiting Water Range: A Case Study for Compacted Subsoils

There is a need for improved knowledge of the limits to the available water range for root growth in the subsoil. The objective of this study was to recalculate the upper and lower limits of the least limiting water range (LLWR) concept by using respectively the air‐filled porosity (εa) at which 0.005 of the relative gas diffusivity (Ds/Do) is reached and readily available water (RAW). The refined upper limit estimates the variation in εa related to pore connectivity and the refined lower limit expresses the boundary at which plants suffer physiological water stress. This study was based on soil sampled in compaction trials on two sandy loam soils. Soil samples were taken from plots with no compaction (Control), and compaction with 78 kN (M8) and 58 kN (M6) wheel loads with multiple wheel passes. The soil cores were analyzed for εa, Ds/Do, bulk density (ρb) and penetration resistance (PR). Heavy farm machinery impact of M8 and M6 led to subsoil compaction up to depth of 0.5 to 0.7 m for the soils under study. The subsoil structure was affected by compaction across depths with the decrease in εa (∼33–46%) and Ds/Do (∼37–61%) and increase in ρb (∼4–8%) and PR (∼40–50%, at −100 hPa at 30‐cm depth). The refined LLWR showed a wider water range compared to the original approach. We anticipate that the refined LLWR well reflects the limiting soil physical conditions for root growth for the studied soils, but validation by combined soil physical and plant growth measurements is needed.Core Ideas Heavy traffic‐induced compaction narrows LLWR in the subsoil. Air permeability at critical limit of gas diffusivity take in pore organization. Using readily available water as the lower limit represents a drought stress boundary.

Using a nitrogen mineralization index will improve soil productivity rating by artificial neural networks

ABSTRACTIn the Pampas, nitrogen fertilization rates are low and soil organic matter impacts crop yield. Wheat (Triticum aestivum L.) yield was related to total soil nitrogen (total N) and to nitrogen mineralization potential (mineralized N) to determine whether the effects of organic matter may be attributed to its capacity to act as a nitrogen source or to the improvement of the soil physical condition. Data of 386 sites from throughout the region comprised in a recent soil survey were used, in which climate and soil properties to 1 m depth were determined. Artificial neural networks were applied for total N and mineralized N estimation using climate and soil variables as inputs (R2 = 0.59–0.70). The models allowed estimating total N and mineralizable N at county scale and related them to statistical yield information. Neural networks were also used for yield prediction. The best productivity model fitted (R2 = 0.85) showed that wheat yield could be predicted by rainfall, the photothermal quotient, and mineralized N. The soil organic matter effect on crop yield seems to be mainly related to its nitrogen mineralization capacity. Using mineralized N as predictor would be a valuable tool for rating soil productivity.

Impact of soil puddling intensity on the root system architecture of rice (Oryza sativa L.) seedlings

Puddling of rice paddies is undertaken to create a soft soil bed for easy transplanting of rice seedlings, to control weeds and reduce water and nutrient leaching. There is a drive for less intense puddling because of its physical disturbance of soil, energy inputs and labour requirements, which may produce different soil physical conditions for root growth. The objective of this study was to investigate the influence of puddling intensity on soil structure and the subsequent impact on the growth of rice seedling roots. Three treatments with different puddling intensities were established: (1) No puddling; (2) Low and (3) High intensity puddling. The rice genotype, Nipponbare was grown in soil columns for 18 days. Soil bulk density, aggregate size distribution and three-dimensional (3D) macropore structure were measured. Two-dimensional root traits were determined by WinRhizo and 3D root traits were determined by X-ray Computed Tomography (CT). Our results show the percentage of large macroaggregates (> 2 mm) decreased by 69.6% (P < 0.05) for low intensity puddling and by 95.7% (P < 0.05) for high intensity puddling compared with that of no puddling. The macroporosity (> 0.03 mm) of no puddling was 2.3 times greater than low intensity puddling and 3.5 times greater than high intensity puddling. The total root lengths of no and low intensity puddling were 1.56–1.86 times greater than that of high intensity puddling. Large roots, including radicle and crown roots, were the same length regardless of puddling intensity. Our study demonstrates that intensive puddling can degrade soil structure, which consequently limits rice root growth.

Use of Maize Straw or Animal Manure as an Alternative to Gypsum to Ameliorate Saline-Sodic Soils

This work aimed to evaluate the effect of the addition of animal manure or maize straw, combined or not with gypsum, on the recovery of the productive capacity of a Fluvic Entisol affected by salts cultivated with maize (Zea mays L.). The experiment was conducted in a greenhouse, in PVC columns in a 10 x 4 factorial scheme, with ten treatments and four replicates (gypsum, 15 t ha-1 manure, 30 t ha-1 manure, 15 t ha-1 maize straw, 30 t ha-1 maize straw, 15 t ha-1 gypsum plus manure, 30 t ha-1 gypsum plus manure, 15 t ha-1 gypsum plus maize straw, 30 t ha-1 gypsum plus maize straw and control, no input) in a randomized block design. Soils that received maize straw increased both the soil water infiltration rate and the amount of salts leached at the bottom of the column compared to soils that received gypsum. However, maize straw reduced the growth of maize plants, probably due to the immobilization of nutrients. In soils that received 15 t ha-1 manure, the growth of maize plants was higher compared to soils that received gypsum, indicating that the application and organic inputs can improve soil physical conditions, reduce salinity and promote plant growth without the need for the acquisition of gypsum, which gives farmers more autonomy and reduces costs.

Effect of Soil Physical Conditions on Emission of Allyl Isothiocyanate and Subsequent Microbial Inhibition in Response to Brassicaceae Seed Meal Amendment.

Generation of allyl isothiocyanate (AITC) in soil treated with residues of specific Brassicaceae species yields direct and indirect suppression of soilborne plant pathogens. Soil physical conditions demonstrably affected the quantity of AITC generated in response to soil incorporation of a Brassica juncea/Sinapis alba seed meal (SM) formulation. The concentration of AITC generated in SM-amended soil increased with an increase in temperature from 10 to 30°C. AITC emission was also elevated with an increase in soil water potential from -1,000 kPa through -40 kPa; however, a significant decrease in AITC emission was observed in a saturated soil environment (0 kPa). Peak AITC emission was obtained 2 to 3 h after SM amendment under optimal conditions but the peak was delayed in soils incubated at low temperature or in extreme moisture environments. Although AITC production varied significantly across different orchard soils, all three orchard soils yielded the same pattern of AITC release in response to SM amendment over the spectrum of soil water potentials examined in this study. Mycelial growth inhibition in fungi and oomycetes isolated from apple roots was dependent on both AITC concentration and exposure time. Pythium ultimum exhibited sensitivity to AITC at concentrations ranging from 0.01 to 0.22 µg g-1 of soil, whereas Hypocrea lixii was insensitive to AITC. Exposure to AITC at a concentration of 0.22 µg g-1 of soil for a period of 2 h restricted hyphal growth of Rhizoctonia solani AG-5, Ilyonectria destructans, and Mortierella alpina. R. solani AG-5 exhibited significant growth inhibition when incubated at AITC concentrations of 0.008 to 0.011 µg g-1 of soil for 10 h. These findings provide information that will be useful in the management of appropriate soil variables to obtain optimal yields of AITC in response to SM soil amendments and indicate that a standard soil moisture prescription may be suitable for use when applying this SM formulation for soilborne disease control.

Resilient Modulus of Lime-Bamboo Ash Stabilized Subgrade Soil with Different Compactive Energy

The resilient modulus ( $${\text{M}}_{\text{r}}$$ ) of natural subgrade materials have been extensively studied, however, for stabilized subgrade materials, the $${\text{M}}_{\text{r}}$$ requires adequate characterization to ascertain pragmatic performance. Furthermore, the soil $${\text{M}}_{\text{r}}$$ is known to be influenced by the soil physical state. A lime-modified expansive subgrade soil, admixed with varying percentages of bamboo ash (4, 8, 12, 16, and 20%) was understudied to determine its $${\text{M}}_{\text{r}}$$ with compaction attenuation. Two compactive energies, British standard heavy and British standard light were applied for determination of the stabilized soil $${\text{M}}_{\text{r}}$$ . The $${\text{M}}_{\text{r}}$$ was determined in accordance with AASHTO T307 guide. The results clearly showed that whilst $${\text{M}}_{\text{r}}$$ improved with additive content and increased deviator and confining stresses, the values diminished with compaction attenuation. A polynomial model relationship was developed for the $${\text{M}}_{\text{r}}$$ obtained using the two compactive energies. The results of the multiple regression analysis carried out using modified stress-based models from literature demonstrated the influence of compactive energy and additive content on the stabilized soil $${\text{M}}_{\text{r}}$$ .

Soil physical and mechanical attributes in response to successive harvests under sugarcane cultivation in Northeastern Brazil

Soil degradation due to agricultural field traffic is a serious issue affecting soil functions in modern agriculture. With sugarcane cultivation, the number of harvests through successive ratoons has become a challenge for the maintenance of soil quality in the topsoil and subsoil. The objective of this study was to evaluate physical and mechanical responses of soil to successive harvests under sugarcane cultivation in an Ultisol of coastal tablelands in Northeastern Brazil. Disturbed and undisturbed soil samples were collected from five sites at depths of 0–0.20 m (topsoil) and 0.20–0.40 m (subsoil), in which one, two, three or four harvests had taken place. In addition, one site had been kept without cultivation for one year after a sugarcane crop. Organic carbon (OC), maximum soil bulk density (BDmax), critical water content (wc), degree of compaction (DC), precompression stress (σp), compression index (CI) and the angle of internal friction (φ) were measured and subjected to multivariate analyses for the different sugarcane ratoons. Soil compaction indicators and OC in the topsoil were sensitive to the number of harvests, where compaction and OC increased with each ratoon sugarcane crop. The increase in OC with successive harvests resulted in a decrease in the BDmax and an increase in the wc, which suggest that optimum water content for compaction is moved to wetter zone due organic matter effects. The DC increased considerably after the third harvest, and it was at a maximum level before the sugarcane renovation (i.e. at the harvest immediately before the new seeding). In the subsoil, immediately below the plough layers, where plough pan formation typically occurs in conventional tillage, considerable changes in the soil physical and mechanical indicators are unlikely to occur due to the persistence of compacted layers. The increase in the organic carbon content results in better soil physical condition in the soil surface, but the degree of compaction may slightly increase due to frequency of traffic caused by the increase in the number of harvests, becoming compaction more severe close to the sugarcane renovation.

Limited effects of early snowmelt on plants, decomposers, and soil nutrients in Arctic tundra soils.

In addition to warming temperatures, Arctic ecosystems are responding to climate change with earlier snowmelt and soil thaw. Earlier snowmelt has been examined infrequently in field experiments, and we lack a comprehensive look at belowground responses of the soil biogeochemical system that includes plant roots, decomposers, and soil nutrients. We experimentally advanced the timing of snowmelt in factorial combination with an open‐top chamber warming treatment over a 3‐year period and evaluated the responses of decomposers and nutrient cycling processes. We tested two alternative hypotheses: (a) Early snowmelt and warming advance the timing of root growth and nutrient uptake, altering the timing of microbial and invertebrate activity and key nutrient cycling events; and (b) loss of insulating snow cover damages plants, leading to reductions in root growth and altered biological activity. During the 3 years of our study (2010–2012), we advanced snowmelt by 4, 15, and 10 days, respectively. Despite advancing aboveground plant phenology, particularly in the year with the warmest early‐season temperatures (2012), belowground effects were primarily seen only on the first sampling date of the season or restricted to particular years or soil type. Overall, consistent and substantial responses to early snowmelt were not observed, counter to both of our hypotheses. The data on soil physical conditions, as well interannual comparisons of our results, suggest that this limited response was because of the earlier date of snowmelt that did not coincide with substantially warmer air and soil temperatures as they might in response to a natural climate event. We conclude that the interaction of snowmelt timing with soil temperatures is important to how the ecosystem will respond, but that 1‐ to 2‐week changes in timing of snowmelt alone are not enough to drive season‐long changes in soil microbial and nutrient cycling processes.

Modeling the Impact of Biopores on Root Growth and Root Water Uptake

Core Ideas A 3D soil–root model was used to investigate root–biopore interactions. Known effects of biopores on root growth, i.e., increased root length and depth were reproduced. Despite reducing root–soil contact, biopores led to increased water uptake in dry periods. Biopores had a larger impact on water uptake for more compact and less conductive soils. Roots are known to use biopores as preferential growth pathways to overcome hard soil layers and access subsoil water resources. This study evaluates root–biopore interactions at the root‐system scale under different soil physical and environmental conditions using a mechanistic simulation model and extensive experimental field data. In a field experiment, spring wheat (Triticum aestivum L.) was grown on silt loam with a large biopore density. X‐ray computed tomography scans of soil columns from the field site were used to provide a realistic biopore network as input for the three‐dimensional numerical R‐SWMS model, which was then applied to simulate root architecture as well as water flow in the root–biopore–soil continuum. The model was calibrated against observed root length densities in both the bulk soil and biopores by optimizing root growth model input parameters. By implementing known interactions between root growth and soil penetration resistance into our model, we could simulate root systems whose response to biopores in the soil corresponded well to experimental observations described in the literature, such as increased total root length and increased rooting depth. For all considered soil physical (soil texture and bulk density) and environmental conditions (years of varying dryness), we found biopores to substantially mitigate transpiration deficits in times of drought by allowing roots to take up water from wetter and deeper soil layers. This was even the case when assuming reduced root water uptake in biopores due to limited root–soil contact. The beneficial impact of biopores on root water uptake was larger for more compact and less conductive soils.

Thermo-physical-hydraulic variables in a no-tillage system related to wheeled traffic and furrow-opening mechanisms

Abstract: The objective of this work was to evaluate the impact of different furrow-opening mechanisms on soil physical characteristics, such as mobilization, porosity, bulk density, and the dynamics of water content and temperature in the sowing groove, as well as the influence of wheeled traffic and of these variables on corn (Zea mays) productivity. The experiment was conducted at the agronomic experimental station of Universidade Federal do Rio Grande do Sul on a Argissolo Vermelho (red Ultisol). Treatments consisted of three winter cover crops and of two types of furrow-opening mechanisms for fertilization (shank and disk), with or without tractor traffic. Corn was planted as the summer crop, and soil mobilization in the sowing groove, soil temperature and moisture content during the crop cycle, and soil physical conditions, such as bulk density and porosity, were evaluated. Tractor traffic and the type of furrow-opening mechanism used did not affect significantly soil temperature and moisture content during the development of the corn crop; however, significant differences were observed in grain productivity and soil mobilization, bulk density, and porosity.

Interceptación y escorrentía del bosque altoandino en la reserva forestal protectora “El Malmo”

Los bosques tropicales son importantes a nivel mundial por su biodiversidad y los servicios ecosistémicos que proveen, son claves en el ciclo global del agua. Los cambios y presiones de origen antrópico que afectan a los bosques tropicales inciden en el papel fundamental de estos en la provisión de agua. En este trabajo se evalúa la relación de las coberturas vegetales presentes en el Bosque altoandino de la Reserva Forestal Protectora “El Malmo” con la calidad y cantidad de interceptación y escorrentía; la zona de vida analizada comprende cuatro tipos de coberturas: bosque denso altoandino, vegetación secundaria baja, plantación de latifoliadas y mosaico de pastos con espacios naturales. Se instalaron ocho montajes (dos por cobertura) compuestos cada uno de una parcela de escorrentía y un medidor de precipitación bajo el dosel; el levantamiento de datos se efectúo cada ocho días durante 24 semanas. Los resultados indican que la interceptación de la precipitación no difiere en cada cubierta, mientras que si se ve afectada la escorrentía superficial y su calidad respecto a sedimentos, cambios que obedecen fuertemente a las diferencias en las condiciones físicas del suelo. La cobertura que permite las mejores dimensiones de calidad y cantidad de agua es el bosque denso altoandino. La influencia de la intervención antrópica en el área y la presencia de invasoras afectan negativamente estas variables. Este trabajo aporta conocimiento sobre el comportamiento hidrológico de la Reserva, para su uso en la gestión forestal. Así mismo, genera información, hasta el momento inexistente, sobre la relación interceptación/escorrentía en bosques de la región Cundiboyacense, convirtiéndose en punto inicial de comparación para nuevas investigaciones en ecosistemas altoandinos.

A Review on Plant Responses to Soil Salinity and Amelioration Strategies

Soil salinity is a major abiotic stress, limiting plant growth and development worldwide. Plants grown under saline soil condition experiences a significant amount of high osmotic stress, ion toxicities and nutritional disorder, and these are responsible for poor soil physical condition as well as lead to reduced plant productivity. Plants exhibit a number of responses under salt stress by affecting morphological, physiological and biochemical process. A complete understanding of how plants respond to soil salinity and comprehensive management approaches of combining physiological and biochemical attributes with molecular tools are essential for mitigating the adverse effects of salinity on plant growth and productivity. Recent reports on the plant responses due to soil salinity highlighted the importance of integration of different advanced strategies to address the problem of soil salinity. This review will focus on morphological and physiological changes of plants under saline soil and an overview of suitable strategies to regulate plant adaptation and tolerance to salinity stress.

Insights into 33phosphorus utilisation from Fe- and Al-hydroxides in Luvisol and Ferralsol subsoils

There is currently relatively little available information on subsoil phosphorus (P) use for crop production as a function of soil order. In this study, a rhizobox experiment was performed using subsoils of two reference soil groups, an Orthic Ferralsol and a Haplic Luvisol. To evaluate the immediate P uptake by wheat (Triticum aestivum L.) from different subsoil P pools during 14 days of growth, subsoil bands were spiked with KH2PO4 solution associated to Fe-hydroxide (33P-Fe), to Al-hydroxide (33P-Al), in free form (33P-OrthoP), or in trace amounts without any additional 31P (33P-NoP). At the beginning of the experiment, the soil water content was set at 75% of water-holding capacity, corresponding to an initial soil matric potential of −12 ± 1 kPa. During plant growth, soil moisture decreased in both soils, but soil matric potentials in both soils did not drop below field capacity (−33 kPa; pF 2.5). The shoot dry weights of the Ferralsol were 1.2 to 1.8 times those of the Luvisol. Despite elevated soil P availability in the Luvisol, shoot P concentrations did not differ between the two soils. The amount of 33P taken up by the shoots from the oxide phases was 15% to 40% greater in the Ferralsol treatments than in those in the Luvisol treatments. It was concluded that the more favourable physical soil conditions facilitated 33P uptake from both oxidic phases from the Ferralsol subsoil relative to the Luvisol subsoil, despite better P phytoavailability in the latter.

Soil Physics Involvement in the Germination Ecology of Buried Weed Seeds.

Trials were performed to test the germination ecology of buried weed seeds as a function of physical soil conditions such as of burial depth, texture, and compaction. Indeed, these ecological conditions, due to the adopted agronomic practices, play a crucial role in modulating the seed bank germination dynamics. Experiments were carried out in open fields in confined soils (polypropylene pipes), and in the laboratory in Petri dishes. Sowing depth strongly inhibited the seed germination of the three weed species selected. This inhibition was found to be inversely proportional to the size of the soil particles. Compaction strongly increased the depth-mediated inhibition, especially in soils that were rich in clay particles, and was inversely proportional to the seed size. The physiological nature of the dormancy imposed by burial was investigated. In addition, ungerminated seeds, re-exhumed after deep-sowing for six months, were found to be in deep dormancy, especially after burial in compacted clay soil. This dormancy induction was more pronounced in weed species characterized by small seeds. Critical issues are discussed regarding weed seed bank ecophysiology and their management in sustainable agricultural cropping systems.

Tillage effects on soil physical condition and root growth associated with sugarcane water availability

We hypothesized that in-row deep tillage (DT) may improve crop resilience during dry spells through change in the soil physical/hydraulic properties, in root system development and yield. The objective of this study was to gain insight into the influence of this management on soil physical properties and root growth associated with sugarcane water availability. A three-year experiment on a sandy-clay haplustox was used for the assessment of water retention, bulk density, porosity, pressure head, temperature and plant response (yield and root system). Soil carbon stocks were also assessed in the soil profile. The treatments compared of conventional tillage (CT), which consisted of a 0.3 m ploughing followed by two disking graders with 20″ discs and one light disking leveler grade, and DT, a subsoiler rod (0.8 m deep) with a rotary hoe with 16 knives to raise crop seedbed in rows. Our results reveal that DT resulted in lower bulk density and higher total porosity values than CT in most cases for the surface soil layers. Moreover, while the soil water relations did not show significant difference for total water availability, the soil water pressure head monitoring indicated a trend of more negative values under CT management, i.e., a drier condition. Additionally, DT resulted in better root system development referring to root density and root length density. However, DT resulted in lower sugarcane yield. The experiment was carried out under rainfed conditions, but rainfall distribution did not limit sugarcane production. Therefore, under the mild water stress conditions as observed in this study, the observed root biomass increase did not favor sugarcane yield.

Micro-aggregate Indices and Structural stability of Soils under Different Management

Low water stability of soil micro-aggregates accentuated by increased intensity of cultivation and soil degradation are among the significant issues that draw the atten- tion of Soil Scientists due to their effects on soil physical conditions. The study was carried out to quantify changes in micro-aggregate stability indices of soils on coastal plain sands under contrasting land use and management. Soil samples were collected from cassava plots, plantain, maize, rubber plantation, oil palm and 2-season fallow plots with Calapogonium mucunoides. Results revealed significant changes in micro-and macro-aggregate stability indices. Clay dispersion index (CDI) was 0.46 and 0.39 respectively in cassava and maize plots. Parameters such as aggregated silt and clay (ASC), clay flocculation index (CFI) and saturated hydraulic conductivity (Ksat) used as estimates of soil structural stability were significantly (p &lt; 0.05) increased due to 2-season fallow and 10-year oil palm plantation. Two-year fallow increased ASC and CFI by 57 % and 86.5% respectively compared with continuous maize culti- vation. Ten-year cultivation to cassava and maize increased sand content by 18 and 9% respectively and decreased the mean weight diameter (MWD) of water stable aggregates and Ksat. Relationships showed significant (p &lt; 0.05) positive correlation between ASC and CFI and Ksat. Two-year fallow with Calapogonium mucunoides and 10-year oil palm plantation improved the soil micro- and macroaggregate indices. They could be used to conserve the soil and reduce the degradation of soil resources.

Effect of different sources of potassium on yield and quality of apple (cv. Red Delicious) in temperate conditions

The present investigation was carried out to observe the effect of potassium on different parameters of apple in temperate conditions. Randomized block design experiment was adapted for an orchard of 15 years old with collection of soil samples and their analysis for physico-chemical properties under different treatments with fixed quantity of urea (1500g/tree), DAP (750g/tree) and potassium through MOP, K2SO4 and K-Schoenite (2500g/tree) in three, one and two split applications, respectively. The first application of recommended quantity of fertilizers was applied three weeks before expected bloom, Second three weeks after fruit set and third application at the end of July. Sample collection was done in the month of September followed by analysis for different parameters and results revealed that application of potassium through MOP @ 2500g/tree with two foliar applications of MOP @ 1.5 % including vermicompost @ 5kg/tree (T4) improved soil physical conditions, nutrient availability, fruit yield and quality of apple. The combined effect of chemical fertilizer, two sprays and organic fertilizer (vermicompost) showed significantly (P?0.05) higher results of nitrogen, phosphorous, potassium magnesium and sulphur but low calcium than other vermicompost added treatments. The work concluded that different potassium sources can have great impact on yield and quality of apple and respond to level of concentrations or dose as applied in current study with different split.