242,176 research outputs found

    The pattern of soil water extraction by individual kiwifruit vines : a thesis presented in partial fulfillment of the requirements for the Master of Agricultural Science in Soil Science at Massey University

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    In order to efficiently design and operate irrigation systems water balance studies are needed. To date few of these studies have been carried out on kiwifruit. Detailed measurements of water extraction were made beneath two 7 year old kiwifruit vines. Under-vine covers were used on these vines to exclude rainfall and irrigation. Measurements of fruit size and leaf water potential were made on the two covered vines and on adjacent irrigated vines. In addition, solar radiation and air temperature were monitored in the orchard block. In concurrent studies, the root distribution of vines in the orchard were determined and heat pulse measurements of sapflow were made. The water extraction pattern showed little variation with depth to the maximum depth of measurement (2.2 m). There was, however, considerable variation in extraction with horizontal distance away from the vine. This variation may be explained in terms of the root distribution. The soil volume may be divided into the zone of occupation, in which the soil is completely occupied by the plant roots, and the zone of exploration, which is the volume of soil in which there are a few roots but the soil is still largely unexplored. Within the zone of occupation, water is uniformly extracted despite variation in root density. Water appears to be extracted from the zone of exploration primarily by flow of water towards the zone of occupation, where the soil water potential is lower. The fruit volume and leaf water potential measurements were used to indicate the onset of water-stress. At this time, soil water potential in the zone of occupation was between -40 and -50 kPa. The size of the reservoir of readily availible water was found to be at least 2.1 m 3 for 7 year old vines, and is projected to rise to a maximum of at least 6.5 m3 in three or so years in this orchard. Whereas the vine canopy may, by management, mature in 3 years, the root system may take 10 years to mature, so irrigation requirements of young vines will be higher than for mature vines. This is contrary to common assumptions made in standard methods for designing horticultural irrigation systems and is due to changes in the size of the reservoir rather than changes in the rate of water use. When there is radial variation in water extraction it is important to take account of the variation when calculating volumes of water extracted from the soil. The rate of water use by the vines, as estimated by the water balance method and the heat pulse technique, was found to be considerably lower than that predicted by the equilibrium evapotranspiration rate. This may be due to experimental error, and further work is required to clarify this matter

    On the time spent in the red by a refracted L\'evy risk process

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    In this paper, we introduce an insurance ruin model with adaptive premium rate, thereafter refered to as restructuring/refraction, in which classical ruin and bankruptcy are distinguished. In this model, the premium rate is increased as soon as the wealth process falls into the red zone and is brought back to its regular level when the process recovers. The analysis is mainly focused on the time a refracted L\'evy risk process spends in the red zone (analogous to the duration of the negative surplus). Building on results from Kyprianou and Loeffen (2010) and Loeffen et al. (2012), we identify the distribution of various functionals related to occupation times of refracted spectrally negative L\'evy processes. For example, these results are used to compute the probability of bankruptcy and the probability of Parisian ruin in this model with restructuring

    Analysis of the 19th Century Historic Archaeological Material Culture Remains from the Browning Site in Smith County, Texas

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    The Browning site (41SM195A) is located on a 3800 m2 alluvial terrace that overlooks the Auburn Creek floodplain in eastern Smith County, Texas. This setting is near the headwaters of a stream system in the Harris Creek drainage; Harris Creek meets the Sabine River ca. 34 km to the north. In the vicinity of the Browning site, the valley, being narrow with steep valley walls, offers few locations suitable for either prehistoric or historic occupations. Soils here arc Entisols; they vary in depth from 30-70 em across the landform, terminating at a sandstone C-horizon. These arc soils that formed mostly under forest vegetation and are dominantly sandy or loamy. The Browning site falls within the Pineywoods vegetation area and represents the western extent of the pine and deciduous forests of the Southeastern U.S. coastal plain. Archaeological investigations at the Browning site have been carried out intermittingly for several years by the junior author. That work has led to the recognition that it is a stratified site with two very distinct occupations, an early to mid-19th century assemblage of historic artifacts primarily in an upper zone (0-20 em bs) overlying a buried (20-50 em bs) Late Woodland period occupation. The historic occupation is in the center of the terrace, covering approximately 500m2• The historic artifacts arc found primarily in the upper sediments, but due probably to pedoturbations, they have been found as deep as 50 em in the underlying prehistoric archaeological deposits. Excavations at the Browning site have consisted of 41 1 x 1 m units (with a total excavated volume of 20.4 m3) and 22 shovel tests. Surface collections were obtained from the site in 1996 and 2002. The 22 shovel tests excavated at the site were conducted first to better ascertain the limits of the site and identify areas of concentrated cultural activity; ST 4, 8-9, 12, and 19 contained 19th century historic artifacts. Once a buried prehistoric occupation zone was identified, units were placed primarily in cardinal directions to better define the occupation zone\u27s boundaries and levels of occupational intensity, and also sample the overlying 19th century component. The I x 1 m units were excavated in arbitrary l 0 em levels and the soil was dry-screened for artifacts through I /4-inch hardware cloth except for a fine screen sample from Unit I that was water-screened through I /32-inch mesh. A level sheet was completed at the end of each level. Profiles were drawn of one wall of each unit or a common wall when several units were joined. The shovel tests followed the same procedures, except they were excavated in arbitrary 20 em levels. One feature had four refined earthenware sherds (as well as two prehistoric artifacts) and 15 small pieces of animal bone. This was a shallow pit with a very dark grayish-brown sandy loam fill (with charcoal flecks) and a rounded bottom that was 63 em in diameter and extended from 22-29 em bs

    Prehistoric Ceramics from the Browning Site (41SM195A)

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    Archaeological work at the Browning site (4JSM195A) in eastern Smith County, Texas, has shown that it is a stratified site with two very distinct occupations: an early nineteenth century assemblage of artifacts in the upper zone overlying a buried prehistoric occupation. This occupation appears to be confined to the Woodland time period (ca. 500 B.C. to A.D. 800) with little evidence of any earlier or later prehistoric activity. The Woodland period in East Texas is a time of important cultural changes, the most obvious (and most important?) of which is pottery-making and the bow and arrow. The main focus of the prehistoric occupation at the Browning site occurs in an organically enriched darker soil zone that is the result of either a continuous human occupation or frequent revisiting of this location, what Waters has described as archaeo-sediments resulting from human activity. This darker soil occupies the center of the landform and covers approximately 500m2 It contains charred wood, charred nut shell, lithic debris from stone tool manufacture/maintenance, and small amounts of burned and unburned animal bone. Other artifacts in this distinct soil zone include small dart points, mostly varieties of Gary; arrow points, mostly of the Friley and Steiner types; ground stone tools; and ceramics, primarily plain grog-tempered wares. Early work at the site included the excavation of 6.546 m3 of archaeological deposits from 10 1 x 1 m test units plus 22 shovel tests, resulting in the recovery of numerous historic and prehistoric artifacts, including eight Woodland period sherds. To date, excavations at the Browning site have totaled 20.4 m3 of archaeological deposits from 41 1 x 1m test units. The total amount of sherds associated with the Woodland occupation now totals 40 pieces. Those sherds, which are described in some detail and compared with other known sites, are the focus of this article. These sherds are scattered evenly across the occupation area in low densities

    Children as a Tool of Occupation in the French Zone of Occupation of Germany, from 1945 to 1949

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