Absorption of primary macronutrients and soybean growth at different compactation densities and moisture levels in a silt loam soil

ABSTRACT Soybean cultivation is increasing rapidly in the region of Alto Vale do Itajaí, State of Santa Catarina, where there is a predominance of silt soils. The objective of this work was to evaluate the content of primary macronutrients in shoots and shoot and root vegetative growth of soybean (Glicine max L. Merrill) grown in a silt-loam soil under different compactation densities and moisture levels. A randomized block design in a 4x4 factorial arrangement was used, with four compactation densities: 1.00; 1.20; 1.40 and 1.60 Mg m-3, and four soil moisture levels: 0.130; 0.160; 0.190 and 0.220 kg kg-1 and four replications. Each pot consisted of the overlapping of three 150-mm PVC rings, where soil was maintained in the higher and lower part of the pot with a density of 1.00 Mg m-3 and in the intermediate ring, the compactation densities were increased. Values of soil density higher than 120 Mg m-3 negatively affected N, P and K uptake by soybean plants, as well as the plant mass of the shoots and roots. The higher levels of soil moisture reduced the compaction effect and promoted better absorption of P and K.

Kirvoista kosmokseen - ja kaikkea siltä väliltä

TAT eli Tutka- ja avaruusteknologiaryhmä on osa Ilmatieteen laitoksen Uudet havaintomenetelmät -ohjelmaa.

Jotain siltä väliltä : sukupuolen ristiinesittäminen YouTuben meikkivideoissa

Teemanumero: Sosiaalinen media ja minäteknologiat.

OMXH 25-yhtiöiden valuuttariski ja siltä suojautuminen

Tämän kandidaatintutkielman tavoitteena on selvittää OMXH 25-yhtiöiden altistumista valuuttariskille ja kuinka nämä yhtiöt suojautuvat siltä. Tässä tutkimuksessa on lisäksi selvitetty näiden yhtiöiden tärkeimmät ulkomaanvaluutat ja yhtiöiden suojausstrategioita. Valuuttariskin suuruuden selvittämiseksi yhtiöiden vieraan valuuttaista liikevaihtoa verrattiin yhtiön kokonaisliikevaihtoon. Tutkimuksen aineistona on käytetty yhtiöiden vuosien 2013 ja 2014 tilinpäätöksiä. Aineistosta on lisäksi rajattu pois OMXH 25-yhtiöiden joukosta Nordea, Sampo, Elisa ja Telia Sonera. Nämä yhtiöt rajattiin pois, koska ne soveltuivat huonosti tämän tutkimuksen kohteiksi. Tutkimuksen teoriakehys on rakennettu keskeisten teorioiden ja käsitteiden avulla. Valuuttariski voidaan jakaa kolmeen osaan: transaktioriskiin, ekonomiseen riskiin ja translaatioriskiin. Valuuttariskin suojauksessa käytettävät instrumentit ovat termiinit, optiot, swap-sopimukset ja vieraan valuuttainen velka. Myös suojaamatta jättämisen mahdollisuutta on tutkittu. Tutkimuksessa kävi ilmi yhtiöiden merkittävä altistuminen valuuttariskille liikevaihdolla mitattuna. Yhtiöiden liikevaihdosta lähes 50% tapahtui jossain muussa valuutassa kuin euroissa. Yhtiöt käyttävät valuuttariskiltä suojautumiseen pääasiassa termiinejä, mutta myös muita instrumentteja käytetään jonkin verran. Yhtiöt keskittyvät eniten transaktioriskin suojaamiseen ekonomisen riskin ja tranlaatioriskin jäädessä pienemmälle huomiolle. Myös aikaisemmissa tutkimuksissa on saatu samankaltaisia tuloksia. Viime vuosien voimakkaat valuuttakurssimuutokset ovat vaikuttaneet yhtiöiden tuloksiin negatiivisesti ja erityisesti ruplan arvon voimakas heikentyminen suhteessa euroon aiheutti joillekkin yhtiöille merkittäviä valuuttakurssitappioita. Tärkein vieras valuutta tutkituille yhtiöille oli USA:n dollari. Korkeasta suojausasteesta huolimatta suurinosa tutkituista yhtiöistä kärsi valuuttakurssitappiota kumpanakin tarkasteltuna vuonna.

Carbon fractions associated with silt-size particles in surface and subsurface soil horizons

Information on the distribution and behavior of C fractions in soil particle sizes is crucial for understanding C dynamics in soil. At present little is known about the behavior of the C associated with silt-size particles. We quantified the concentrations, distribution, and enrichment of total C (TC), readily oxidizable C (ROC), hotwater- extractable C (HWC), and cold-water-extractable C (CWC) fractions in coarse (63–20-mm), medium (20–6.3-mm), and fine (6.3–2-mm) silt-size subfractions and in coarse (2000–250 mm) and fine (250–63 mm) sand and clay (<2-mm) soil fractions isolated from bulk soil (<2 mm), and 2- to 4-mm aggregate-size fraction of surface (0–25 cm) and subsurface (25–55 cm) soils under different land uses. All measured C fractions varied significantly across all soil particle-size fractions. The highest C concentrations were associated with the <20-mm soil fractions and peaked in the medium (20–6.3-mm) and fine (6.3–2-mm) silt subfractions in most treatments. Carbon enrichment ratios (ERC) revealed the dual behavior of the C fractions associated with the medium silt-size fraction, demonstrating the simultaneous enrichment of TC and ROC, and the depletion of HWC and CWC fractions. The medium silt (20–6.3-mm) subfraction was identified in this study as a zone where the associated C fractions exhibit transitory qualities. Our results show that investigating subfractions within the silt-size particle fraction provides better understanding of the behavior of C fractions in this soil fraction.

Is silt the most influential soil grain size fraction?

The contribution of individual grain size fractions (2000–500, 500–250, 250–63, 63–2 and < 2 μm) to bulk soil surface area and reactivity is discussed with reference to mineralogical and oxalate and dithionite extractions data. The 63–2 μm fraction contributed up to 56% and 67% of bulk soil volume and BET surface area, respectively. Consideration of these observations and the mineralogy of this fraction suggest that the 63–2 μm fraction may be the most influential for the release of elements via mineral dissolution in the bulk soil.

Laboratory and in situ studies on a compacted clayey silt fill

This paper presents laboratory and in situ studies carried out on a 200 000 m(3) large clayey silt compacted embankment. Laboratory studies carried out on undeformed block samples included index tests, strength tests and water retention curves using the filter paper technique. Grain size analyses with and without a deflocculating agent clearly showed the existence of grain clusters, which appear to be naturally formed. Field instrumentation installed at depths from 0.25 m to 1.0 m included tensiometers, equitensiometers, time domain reflectometry and geothermometers. Pluviometer data from a nearby weather station are also used to analyse the field data. The ranges of water content and suction values were measured, both of which correlated well with the pluviometer data. The water retention curves including laboratory and field data showed a bimodal shape, consistent with the presence of microand macropores shown in the grain size analysis.

The Effects Of Reinforcement Inclusions On Wear Tolerance, Playing Quality And Physical Properties In A Silt Loam And Sand Rootzone Matrix

Reinforcement inclusions have been advocated to alleviate wear, compaction, and unstable surfaces in sports fields, but little research on the effects of these materials has been conducted in the USA. Experiments were established on a native silt loam and a sand rootzone matrix, seeded with a Kentucky bluegrass (Poa pratensis L.) blend, at the Joseph Troll Turf Research Center, University of Massachusetts, Amherst, USA to determine the effects of reinforcement inclusions on wear, surface hardness, traction, ball roll, ball bounce resilience, water infiltration rate, soil bulk density, air porosity, total porosity, and root weights. Three types of reinforcement inclusions (Sportgrass, Netlon, Turfgrids) were tested along with a non-reinforced control in a three year study. The treatments were set out in a randomized complete block design with four replications in both soils. No inclusion provided less wear or greater infiltration or air-filled porosity relative to the control. Reinforcement inclusions showed significant differences, however, in surface hardness, traction, and ball roll relative to the control, although this varied with the time of year. Infiltration rates, airfilled porosity, total pore space, bulk density, hardness, traction, ball roll, and ball rebound were greater on the sand rootzone than on the silt loam. Significant correlations were present between soil bulk density, surface hardness, traction, and ball roll. Based on our study, the use of reinforcement inclusions to provide better wear tolerance for sand or native soil athletic fields is not warranted. Certain playing surface characteristics, however, may be slightly improved with the use of reinforcement inclusions. The use of sands for sports surfaces is justified based upon the improvement in playing quality characteristics and soil physical properties important to a good playing surface.