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Size fractionation and microbial community structure of soil aggregates  [PDF]
Jong-Shik Kim, David E. Crowley
Journal of Agricultural Chemistry and Environment (JACEN) , 2013, DOI: 10.4236/jacen.2013.24011
Abstract: The microbial community structure in various microaggregates in a loamy sand soil was investigated. The microaggregates were separated into outer and inner aggregates using a series of soil washes. Further physical fractionation of inner aggregates was achieved by separation into coarse and fine sand as macroaggregate fractions, coarse and fine silt as microaggregate fractions, and clay. Research on microbial communities and soil microaggregates can aid in our understanding of soil microhabitats and microorganisms in soil structures, with applications that may contribute to increasing crop production and maintaining sustainable agriculture. In order to study the microbial community structure of aggregates, polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) was performed using 16S rRNA genes. The PCR-DGGE of the Bacteria Actinomycetes and Archaea showed divergent results between the different aggregate fractions. The results showed that the bacterial community structure was highly similar between bulk soil and clay; the inner aggregate community structure of Actinomycetes was closely related between coarse and fine sand and coarse silt, and the Archaea community structure of outer and inner aggregates was more similar than that of total bacteria or Actinomycetes.
Allocation and Abundance of Protozoa among Soil Aggregates  [PDF]
C.R. Shalinimol,R. Arunachalam,G. Annadurai
Journal of Biological Sciences , 2009,
Abstract: In this present investigation, soil samples were collected from two different paddy fields such as Kollemcode (Tamil Nadu) and Pappanancode (Kerala) using PVC pipes. The physico-chemical characteristics of the soil sample were analyzed. Organic content, nutrient content and numbers of ciliates were high in upper segments of soil samples were recorded. The ciliates were higher amount in wet field paddy soil than flooded field paddy soil. The ciliates such as Microthorax sp., Vorticella sp., Oxytricha sp. and Euplotes sp. were identified in both field samples. In enriched culture, Microthorax sp., Vorticella sp., amoebae and some small flagellates were also observed. It was shown that the distribution of protozoan cells was not even but greatly conglomerative among soil aggregates. On the basis of data generated from this study could be exploited for wastewater treatment studies.
Tillage system effects on stability and sorptivity of soil aggregates
J. Lipiec,J. Ku?…??,A. Nosalewicz,M. Turski
International Agrophysics , 2006,
Abstract: Stability and sorptivity of soil aggregates play an important role in numerous soil processes and functions. They are largely influenced by tillage methods. We have compared the effects of long-term application of various tillage systems on aggregate bulk density, rate of wetting, sorptivity, water stability, tensile strength and bulk density of silt loam Eutric Fluvisol. Tillage treatments were: 1) ploughing to the depth of 20 cm (CT), 2) ploughing to 20 cm every 6 years and harrowing to 5 cm in the remaining years (S/CT), 3) harrowing to 5 cm each year (S), 4) sowing to uncultivated soil (NT), all in a micro-plot experiment. Bulk density of soil aggregates was determined by wax method, sorptivity – by a steady state flow, water stability – by drop impact method, and tensile strength – by crushing test. Tillage had a significant effect on the aggregate characteristics. Soil aggregate bulk density and water stability were greater and rate of wetting and sorptivity were smaller in reduced and no-tillage treatments compared with CT. Greater soil organic matter and bulk density accompanied greater water stability. Smaller rate of wetting and sorptivity can be associated with lower aggregate porosity. The differences in the rate of wetting, sorptivity, and water stability of the initially air-dry soil aggregates and bulk density between the tillage treatments were relatively greater than those in the tensile strength.
Estimating Total Nitrogen Content in Brown Soil of Orchard Based on Hyperspectrum  [PDF]
Shujing Cao, Xicun Zhu, Cheng Li, Yu Wei, Xiaoyan Guo, Xinyang Yu, Chunyan Chang
Open Journal of Soil Science (OJSS) , 2017, DOI: 10.4236/ojss.2017.79015
Abstract: The best hyperspectral estimation model of soil total nitrogen (TN) was established, which provided the basis for rapid and accurate estimation of soil total nitrogen content, scientific and rational fertilization and soil informatization management. A total of 92 brown soil samples were collected from the orchard of Qixia County, Yantai City, Shandong Province. After drying and grinding, the hyperspectrum of the soil was measured in the laboratory using ASD FieldSpec3. The TN contents of brown soil were measured by Kjeldahl method. The sensitive wavelengths were selected by multiple linear stepwise regression method. The hyperspectral estimation model of TN was established by Random Forest (RF) and Support Vector Machines (SVM). The models were validated by independent samples. The best estimation model was obtained. The sensitive wavelengths were 956 nm, 995 nm, 1020 nm, 1410 nm, 1659 nm and 2020 nm. The coefficients of determination (R2) of the two estimation models were 0.8011 and 0.8283, the root mean square errors (RMSE) were 0.022 and 0.025, and relative errors (RE) were 0.1422 and 0.1639, respectively. Random Forest model and Support Vector Machines model are feasible in estimating TN contents, but the Support Vector Machines model is better.
Selection and characterisation of high ethanol tolerant Saccharomyces yeasts from orchard soil
AN Moneke, BN Okolo, AI Nweke, LI Ezeogu, FS Ire
African Journal of Biotechnology , 2008,
Abstract: Six yeast strains with different levels of ethanol tolerance were isolated from orchard soil. Out of the six isolates, isolate Orc 6 showed the highest ethanol tolerance (20%) while isolates Orc 2 and Orc 11 had 15% ethanol tolerance. High level ethanol tolerant Saccharomyces yeast, Orc 6, was investigated for its potential application in ethanologenic fermentations. Data presented in this study revealed that Orc 6 yeast isolate tolerated osmotic stress above 12% (w/v) sorbitol and 15% (w/v) sucrose equivalent of osmotic pressure thus exhibiting superior osmotolerance than the reference production wine yeast strain. Invertase activity was also higher for Orc 6 yeast when grown in both sorbitol and sucrose media. Sorbitol increased yeast sedimentation rate in contrast to sucrose. Generally, the new yeast strain, Orc 6, showed superior fermentative performance compared to the reference production yeast strain.
Desalinization of Aggregated Saline Soil: Experiments on Columns of Spherical Aggregates  [PDF]
A.A.Siyal,A. G. Siyal,Z. A. Abro,A.W. Siyal
Journal of Applied Sciences , 2002,
Abstract: Salt affected soils may be reclaimed by leaching, but continuously pending the soil surface and allowing infiltration requires large quantities of water. During such leaching bypass flow occurs, consequently solute within the aggregates is transported much slower decreasing the overall leaching efficiency. The alternate is intermittent leaching which provides time for diffusion of solute from aggregates. Flux density and aggregate size have great effect on the leaching efficiency. Thus leaching of columns of spherical aggregates of three different sizes was carried out in the laboratory with continuous and intermittent leaching to explore the effect of aggregate size and the water flux density on the leaching efficiency. In continuous leaching the inflow of fresh water into column was set equal to outflow of leachate so that the aggregates were bathing in fresh water all the time. In case of intermittent leaching the inflow and out flow of water were regularly interrupted after certain time so as to provide time for salts in aggregates to diffuse out in the macro pores around the aggregates. Experimental results showed that leaching efficiency with intermittent leaching increased with increasing water flux density and aggregate diameter. Depending on the size of aggregate and water flux density water savings up to 65% were obtained under laboratory conditions by using intermittent leaching compared to that of continuous leaching.
Growth and yield of Kinnow (Citrus reticulata Blanco) and soil physical properties as affected by orchard floor management practices in Punjab, Pakistan
Hafeez-ur-Rahman,Ghulam Nabi, Ijaz Ali,Tauseef Tahir and Mukhtar Ahmed
Soil & Environment , 2012,
Abstract: Improvement of soil physical properties through orchard floor management is a desired option because it results in improved yields, better nutrients and water use efficiency and reduced runoff. Studies were carried out to determine effect of weed management practices on growth, fruit production and changes in soil physico-chemical parameters in a citrus orchard. Studies comprised of two orchard floor management practices i.e. cultivation and mowing. In cultivation, weeds emerging in the orchard were controlled by cultivation/ploughing to keep their growth at minimal, while in mowing, weeds were cut at about 5 cm height to keep their growth under check and the cut weeds to act as mulch. After 8 years of continuous practice, determinations were made to compare effectiveness of the management practices in terms of plant growth and yield, changes in soil physico-chemical and water retention characteristics. The data indicated that all the growth parameters responded significantly to management practices. Similarly, soil physico-chemical parameters were also affected. Shoot growth, canopy diameter, Trunk Cross-sectional Area (TCSA) and fruit yield were increased. Soil bulk density was decreased and consequently soil porosity was increased. Mowing promoted accumulation of soil organic matter and soil aggregation. The increased water retention in soil profile and enhanced saturated hydraulic conductivity were attributed to conditions conducive to organic matter accumulation in the soil profile. The results indicated superiority of mowing practice over conventional cultivation towards plant growth, yield and improvement in soil physical properties.
Determining and Mapping Soil Nutrient Content Using Geostatistical Technique in a Durian Orchard in Malaysia  [cached]
Mohd Hasmadi Ismail,Riduan Mohd Junusi
Journal of Agricultural Science , 2009, DOI: 10.5539/jas.v1n1p86
Abstract: Soil nutrient are essential for crop growth. Spatial variability of nutrient can be occurred in various scales, between region, field or within field especially in variation in soil properties. Precision farming is a technology currently available for sustainable agriculture. This technology enables farm management is based on small-scale spatial variability of soil and crop parameters in the field. This study was carried out in a Durian Orchard at Bendang Man Agrotourism Project, Sik, Kedah, Malaysia. The objectives of this study are to determine and map soil nutrient content especially Nitrogen, Phosphorus and Potassium (NPK) variability in a durian orchard using geostatistical technique. The NPK was analyzed and mapped by Geostatistic Plus (GS++) to quantify the level of spatial nutrient available and predict nutrient values at unsampled location. Results indicated that NPK ranged from < 0.1 to 1.0 % (N), < 3 to > 45 ppm (P) and 0.8 to >1.4 cmol(+)/kg (K), respectively. Nutrient map showed that the area has less sufficient of N, while P and K were sufficient. This study revealed the potential and ability of geostatistical-variogram in determining and mapping soil nutrient content in a durian orchard. Furthermore NPK map can be used to apply fertilizer to an area, where less NPK content for efficient fertilizer management.
Compressibility of Oxisol aggregates under no-till in response to soil water potential
Tavares Filho, Jo?o;Tessier, Daniel;
Revista Brasileira de Ciência do Solo , 2009, DOI: 10.1590/S0100-06832009000600002
Abstract: the system of no-till sowing stands out as being a technology that suits the objectives of more rational use of the soil and greater protection against the erosion. however, through till, any of it, occurs modifications of the soil's structure. this current work aims to study the influence of the energy state of the water and of the organic matter on the mechanism of compaction of red oxisol under no-till management system. humid and non-deformed sample were collected in horizon ap of two agricultural areas under no-till, with and without rotation of cultures. in the laboratory, these samples were broken into fragments and sifted to obtain aggregates of 4 to 5 mm sized, which were placed in equilibrium under four matrix potentials. thereafter, they were exposed to uni-dimensional compression with pressures varying from 32 to 1,000 kpa. the results in such a way show that the highest compressibility of aggregates both for the tilling with rotation of cultures as for the tilling without rotation of cultures, occurred for matrix potential -32 kpa (humidity of 0.29-0.32 kg kg-1, respectively), while the minor occurred for the potentials of -1 and -1,000 kpa (humidity of 0.35 and 0.27 kg kg-1, respectively), indicating that this soil should not be worked with humidity ranging around 0.29 to 0.32 kg kg-1 and the highest reduction of volume of aggregates was obtained for the mechanical pressures lower than 600 inferior kpa, indicating that these soils showed to be very influenced by compression, when exposed to mechanical work. also, the aggregates of soil under no-till and rotation of crops presented higher sensitivity to the compression than the aggregates of soil under no-till and without rotation of crops, possibly for having better structural conditions given to a higher content of organic matter.
Variations of soil organic matter in typical orchard regions

YANG Shi-Qi,ZHANG Ai-Ping,YANG Shu-Jing,YANG Zheng-Li,LIU Guo-Qiang,

中国生态农业学报 , 2009,
Abstract: Eleven sampling regions were selected in the Loess Plateau, Jiaodong Peninsular and Beijing suburbs, and based on orchard age, the orchards in each sampling region were devided into three groups of 5~10, 10~15 and >15 years. 99 soil samples in the 0~20 cm layer in orchards and 33 samples in the 0~20 cm layer in nearby croplands were collected. Quantitative attributes of topsoil organic matter in orchard fields, differences in soil organic matter property between the orchard and cropland, and variations in soil organic matter among different orchard age groups were statistically analyzed. The results show higher soil organic matter content in Xixia, Jiaodong Peninsular, and Beijing suburb; and lower in Baota in the Losse Plateau. Compared with croplands, over 60% orchards exhibit statistically insignificant variation in soil organic matter. In less than 30% orchard fields, soil organic matter significant increase, averagely by 0.62%; and significant decrease in less than 10% orchards, averagely by 0.20%. Significant changes in topsoil organic matter content with the orchard age are observed only in two sampling regions. In high yield and high quilty fruit-producing areas, soil organic matter is enhanced by organic fertilizer application, growing grass in orchard, returning grass or stalk into orchard soil. On the whole, soil organic matter in orchard field is not high and varies greatly. Sustainable development capacity of the fruit production is also weak.
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