Dry Matter and Minerals in Loblolly Pine Plantation on Four Arkansas Soils

Average contents of N, P, K, Ca, and Na and total above ground dry matter were determined in 19-year-old unthinned loblolly pine (Pinus taeda L.) plantations in southeastern Arkansas. Three stands were sampled on each of four sites: well and poorly drained coastal plain soils and well and poorly drained loessial soils. Total dry weights, determined from 15 felled trees on each of the 12 plots, ranged from 127,000 kg/ha on poorly drained loessial soil to 173,300 kg/ha on poorly drained coastal plain soil. Ranking of sites, in descending order of production of dry matter, P, K, and Na was: coastal plain poorly drained, coastal plain well drained, loess well drained, and loess poorly drained. Quantity of Ca in stemwood and stembark was 36% higher on well than poorly drained soils; P was 30% higher on coastal plain than loess soils. Results permit calculation of nutrient drain in timber harvests. Bark in 19-year-old plantations contained 44, 44, 25, and 50% of total N, P, K, and Ca in the stems

Unravelling upbuilding pedogenesis in tephra and loess sequences in New Zealand using tephrochronology

The genesis of soils developed in either tephra or loess on stable sites differs markedly from that of soils developed on rock because classical topdown processes operate in conjuction with geological processes whereby material is added to the land surface so that the soils form by upbuilding pedogenesis. Understanding the genesis of such soils (typically Andisols and Alfisols, respectively) often requires a stratigraphic approach combined with an appreciation of buried soil horizons and polygenesis. In New Zealand, calendrically-dated tephras provide an advantage for assessing rates of upbuilding through chronostratigraphy. Many Andisol profiles form by upbuilding pedogenesis as younger tephra materials are deposited on top of older ones. The resultant profile character reflects interplay between the rate at which tephras are added to the land surface and topdown processes that produce andic materials and horizons. In loess terrains, upbuilding pedogenesis since c. 25,000 years ago is associated with maximum rates of loess accumulation c. 3 10 mm per century, sufficiently slow for soil-forming processes to continue to operate as the land surface gradually rises. Thus, Alfisol subsoil features are only weakly developed and Bw or B(x) horizons typically are formed. In contrast, topdown pedogenesis is associated with minimal or zero loess accumulation, the land surface elevation remains essentially constant, and subsoil features become more strongly developed and Bg, Bt, or Bx horizons typically are formed

On-sample water content measurement for a complete local monitoring in triaxial testing of unsaturated soils

To provide a complete local monitoring of the state of an unsaturated soil sample during triaxial testing, a local water content measurement device was adapted to a triaxial device comprising the measurement of local displacements (Hall effect transducers) and suction (High capacity transducer). Water content was locally monitored by means of a resistivity probe. The water content/resistivity calibration curves of an intact natural unsaturated loess from Northern France extracted by block sampling at two depths (1 and 3.3 m) were carefully determined, showing good accuracy and repeatability. The validity of two models giving the resistivity of unsaturated soils with respect to their water content was examined

The influence of changes in water content on the electrical resistivity of a natural unsaturated loess

Non-destructive methods of measuring water content in soils have been extensively developed in the last decades, especially in soil science. Among these methods, the measurements based on the electrical resistivity are simple and reliable thanks to the clear relationship between the water content and the electrical resistivity of soils. In this work, a new electrical resistivity probe was developed to monitor the change in local water content in the triaxial apparatus. The probe is composed of two-pair of electrodes, and an electrical current is induced through the soil at the vicinity of the contact between the probe and the specimen. Some experimental data on the changes in resistivity with the degree of saturation were obtained in specimens of a natural unsaturated loess from Northern France. Two theoretical models of resistivity were also used to analyze the obtained data. Results are finally discussed with respect to the loess's water retention properties

Surface Water Infiltration in Loess Soils of the Lower Mississippi River Valley: An Emphasis on Land Use

The Alluvial Aquifer is the shallowest and most heavily used groundwater aquifer in the Lower Mississippi River Valley, particularly in the Delta region of eastern Arkansas. However, the Alluvial Aquifer is being depleted faster than the rate of recharge, primarily due to excessive withdrawals for irrigated crop production. Since extensive irrigation in the highly agriculturally productive Delta region of eastern Arkansas has been a main culprit in the groundwater depletion issues the region faces, a better understanding of how ecological factors and/or agricultural best management practices could possibly increase infiltration, to consequently increase recharge, are needed in order to either slow down or reverse the declining aquifer levels through the Delta region of eastern Arkansas. Therefore, the objective of this study was to evaluate the effects of landuse on surface water infiltration into alluvial and loessial soils in the Delta region of eastern Arkansas. Landuse combinations of interest included conventional and no-tillage agricultural practices, deciduous and coniferous forests, and native/natural grasslands. Replicate infiltration measurements were conducted using a double-ring infiltrometer, with a 15-cm inner-ring diameter, across multiple sites representing each of the five landuses. Despite the initial soil water content being greater (P \u3c 0.05) in the grassland than in all other ecosystems, the overall infiltration rate into the deciduous forest ecosystem (1.2 cm hr-1) was greater (P \u3c 0.05) than all other landuse types, which did not differ and averaged 0.10 cm hr-1. In addition, though the slope of the relationship between the natural logarithm of the infiltration rate versus the mid-point of time was unaffected (P \u3e 0.05) by landuse, the intercept parameter differed (P \u3c 0.05) among landuses. Results of this study demonstrated that landuse significantly affects infiltration processes in the fine-textured loessial and alluvial soils in the Delta region of eastern Arkansas; thus, further research is warranted into factors that can increase surface infiltration and potentially groundwater recharge

Delineation of major soil associations using ERTS-1 imagery

The delineation of a major soil association in the loess region of Obion County has been accomplished using ERTS-1 imagery. Channel 7 provides the clearest differentiation. The separation of other smaller soil associations in an intensive row crop agricultural area is somewhat more difficult. Soil differentiation has been accomplished visually as well as electronically using a scanning microdensitometer. Lower altitude aircraft imagery permits a more refined soil association identification and where imagery is of sufficient scale, even individual soils may be identified

Dynamics of loess mass deformations due to technogenic load

По результатам анализа энергетических и фильтрационных свойств техногенно нагруженного лессового массива определен интервал глубин, и геологические слои, характеризующиеся наиболее интенсивным развитием деформационных и суффозионных процессов. Приведенная методика оценки устойчивости массива, позволяет прогнозировать поведение склона с учетом нарушения его сплошности, произошедшего вследствие суффозионных про- цессов. Дана количественная оценка момента перехода массива в неустойчивое состояние, а также связь фильтрационных процессов с формированием оползней течения.За результатами аналізу енергетичних і фільтраційних властивостей техногенно навантаженого льосового масиву визначені інтервал глибин та геологічні шари, що характеризуються найбільш інтенсивним розвитком деформаційних та суфозійних процесів. Наведена методика оцінки стійкості масиву дозволяє прогнозувати поведінку схилу з врахуванням порушення його цілісності внаслідок суфозійних процесів. Наведена кількісна оцінка моменту переходу масиву в нестійкий стан, а також зв'язок фільтраційних процесів з формуванням зсувів течії.Analysis of energetic and filtration properties of loess with technogenic loads helps determine depth interval and geological layers characterized by maximum development of deformation processes and suffusion ones. Mass stability evaluation technique shown in the paper helps predict a slope behaviour involving its discontinuity as a result of suffusion processes. Moment of a mass transition into unstable condition is estimated quantitatively as well dependence of filtration processe on stream landslides formation

Samples from Martian craters: Origin of the Martian soil by hydrothermal alteration of impact melt deposits and atmospheric interactions with ejecta during crater formation

The origin of the Martian soil is an important question for understanding weathering processes on the Martian surface, and also for understanding the global geochemistry of Mars. Chemical analyses of the soil will provide an opportunity to examine what may be a crustal average, as studies of loess on the Earth have demonstrated. In this regard the origin of the Martian soil is also important for understanding the chemical fractionations that have affected the composition of the soil. Several processes that are likely to contribute to the Martian soil are examined

MISCANTHUS CULTIVATION IN ROCKS WITH DIFFERENT GEOLOGICAL AGE

Recently, more and more scientists give to Miscanthus the leading part on supplying cellulose-rich feedstock for energy production and the chemical industry. In particular the Miscanthus biomass can be used as animal litter, biomaterial, or bioplastic