• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 51
  • 29
  • 6
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 138
  • 27
  • 27
  • 23
  • 22
  • 21
  • 17
  • 15
  • 15
  • 13
  • 12
  • 12
  • 11
  • 11
  • 11
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Morfogênese e componentes do rendimento de sementes de azevém anual cv BRS Integração em função da época de desfolha / Morphogenesis and components of seed yield of annual ryegrass “BRS Integração” according to the period of defoliation

Abib, Flávio Reina 17 December 2015 (has links)
Submitted by Maria Beatriz Vieira (mbeatriz.vieira@gmail.com) on 2017-04-26T15:11:36Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) tese_flavio_reina_abib.pdf: 2239588 bytes, checksum: 7ce416cc287034a56085359f2706a5ed (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-05-02T18:21:15Z (GMT) No. of bitstreams: 2 tese_flavio_reina_abib.pdf: 2239588 bytes, checksum: 7ce416cc287034a56085359f2706a5ed (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-05-02T18:22:27Z (GMT) No. of bitstreams: 2 tese_flavio_reina_abib.pdf: 2239588 bytes, checksum: 7ce416cc287034a56085359f2706a5ed (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-05-02T18:22:45Z (GMT). No. of bitstreams: 2 tese_flavio_reina_abib.pdf: 2239588 bytes, checksum: 7ce416cc287034a56085359f2706a5ed (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-12-17 / Sem bolsa / A integração lavoura-pecuária com a utilização de azevém anual é uma prática bastante comum no sul do Brasil. No entanto, a maioria das cultivares oficiais presentes no mercado precisam ser dessecadas antes do final do ciclo para permitir uma adequada época de semeadura para culturas de estação quente. Alguns materiais não certificados apresentam ciclos mais precoces, porém também apresentam resistência a dessecantes e rendimentos de forragem insatisfatórios. Neste sentido a Embrapa lançou a cultivar BRS Integração com a proposta de um ciclo mais precoce, todavia, sem resistência a herbicidas, bem como com elevado rendimento forrageiro. Contudo, se desconhece o efeito do manejo de desfolha nesta cultivar para a colheita de forragem e seus impactos na produção e qualidade de sementes e no comprimento do ciclo produtivo. Deste modo o objetivo do presente estudo foi avaliar o efeito da desfolha na produção de forragem e de sementes do azevém anual BRS Integração. O experimento foi realizado na Estação Experimental Terras Baixas da Embrapa Clima Temperado com delineamento de blocos ao acaso com quatro repetições. Foram testados cinco níveis de desfolha (sem, uma, duas, três e quatro desfolhas) para a verificação da produção de forragem (fração de folhas, colmos e material morto); das características morfogênicas e estruturais; dos componentes de rendimento, do rendimento e da qualidade fisiológica das sementes. Verificou-se que o número de desfolhas afetou as características morfogênicas e estruturais da cultivar BRS Integração e, por conseguinte, o rendimento e a qualidade fisiológica de sementes. A execução de três desfolhas permitiu a colheita de aproximadamente 5t de MS.ha-1 e afetou positivamente o rendimento e a qualidade fisiológica das sementes, as quais foram colhidas ainda nos primeiros dias de novembro, o que possibilita o uso da área para a adequada semeadura de cultivos de estação quente. A realização de quatro desfolhas afetou negativamente as características morfogênicas, a estrutura pré-colheita, os componentes de rendimento de sementes, bem como o rendimento real de sementes. No entanto, a ação de quatro desfolhas (colheita total de aproximadamente 7t de MS.ha-1), não afetou negativamente a qualidade fisiológica da semente e ainda possibilitou um rendimento de sementes 15 vezes superior a densidade de semeadura recomendada. / The crop-livestock integration with the use of annual ryegrass is a common practice in southern Brazil. However, most official cultivars on the market need to be desiccated before the end of the cycle to allow adequate time for sowing warm season crops. Some not certified materials present earlier cycles, but also show resistance to desiccants and poor forage yields. In this sense, Embrapa launched “BRS Integração” with the proposal of an earlier cycle, however, without herbicide resistance as well as high forage yield. However, it is unknown the effect of defoliation management in this cultivar for forage crop and its impact on production and quality of seeds and the length of the production cycle. Thus the purpose of this study was to evaluate the effect of defoliation in the production of fodder and seeds of annual ryegrass “BRS Integração”. The experiment was conducted at the Estação Experimental Terras Baixas in Embrapa Clima Temperado with randomized block design with four replications. Five levels of defoliation were tested (no, one, two, three and four defoliation) for verification of forage production (leaves fraction, stems and dead material); morphogenic and structural characteristics; the yield components, yield and seed quality. It was found that the number of defoliation affect the morphogenic and structural characteristics of the “BRS Integração”, and therefore, the yield and physiological quality of seeds. The execution of three defoliation allowed the harvest of approximately 5 tons of dry matter per hectare and positively affected the yield and seed quality, which were still harvested in early November, what allow the use of the area for proper seeding of warm season crops. The performance of four defoliation adversely affected the morphogenic characteristics, pre-harvest structure, seed yield components and the real yield seeds. However, the action of four defoliation (total harvest about 7 tons of dry matter per hectare) didn’t affect negatively the physiological quality of the seed and still allowed a yield of seeds 15 times the recommended seeding rate.
112

Multiple-resistant Italian ryegrass (Lolium perenne spp. multiflorum) populations in Oregon

Liu, Mingyang 28 February 2013 (has links)
Italian ryegrass (Lolium perenne spp. multiflorum) is a common weed management problem in turfgrasses, cereals and non-crop areas in the United States. In Oregon, the number of populations with multiple-resistance continues to increase. To manage these resistant populations, the resistance patterns must be determined. In this study, five Italian ryegrass populations (CT, R1, R2, R3 and R4) from two cropping systems were studied for resistance patterns and mechanisms. The CT population is from a Christmas tree plantation and was resistant to at least six herbicides with four different mechanisms of action: atrazine, diuron (2.4-fold), glyphosate (7.4-fold), hexazinone (3.1-fold), imazapyr (1.8-fold), and sulfometuron. The resistant indices (RI) for sulfometuron and atrazine could not be calculated because 50% growth reduction for the CT population was not reached even with the highest rates applied, 17.6 kg ai ha⁻¹and 16 kg ai ha⁻¹, respectively, which are 16 times the recommended field application rates for this two herbicides. The CT population accumulated less shikimate than the S population. There were two mutations in the CT population, Trp591 to Leu in the ALS gene and Ser264 to Gly in the psbA gene, which explain the ALS and PII cross resistance, respectively. R1, R2, R3 and R4 were collected from annual cropping systems. All four populations were resistant to flufenacet. RIs for two populations, R2 and R4, were 8.4 and 5.9, respectively. R2 and R4 also were resistant to mesosulfuron-methyl, pinoxaden, quizalofop and clethodim. R4 was resistant to diuron, but R2 was not. An Asp-2078-Gly substitution in the ACCase gene was found in both R2 and R4 populations, while another Ile-2041-Asn substitution in the ACCase gene was found in the R4 population. These mutations explain the ACCase cross resistance in the R2 and R4 populations. The mechanisms for the glyphosate resistance in the CT population and the flufenacet resistance in R1, R2, R3 and R4 populations were not identified in this study. None of the five populations were resistant to the herbicide pyroxasulfone. / Graduation date: 2013
113

Effect of Composted and Vermicomposted Cotton Residues on Nutrient Contents, Ryegrass Growth and Bacterial Blight Mitigation

Ali, Sulieman Hammad Nasser 11 November 2011 (has links)
Der Einsatz von organischen Reststoffen zum Anheben oder Stabilisieren des Humusgehaltes als auch um langfristig die Bodenfruchtbarkeit zu verbessern, hat zunehmend an Bedeutung zur Verbesserung der Gesundheit des Bodens und der Bodenproduktivität gewonnen. Die Umwandlung von Ernterückständen, um Bodeneigenschaften zu verbessern, hängt von der Qualität und dem Zustand der Stoffe ab, diese hängen wiederum von der Zusammensetzung des Ausgangsmaterials ab. In Entwicklungsländern werden die meisten Ernterückstände als Tierfutter oder auch als Baumaterial genutzt, viele werden auch als Ersatzbrennstoff für Holz genutzt; zur Vorbereitung des Bodens zur nächsten Ernte oder zur Bekämpfung von Pflanzenkrankheiten und Schadinsekten werden die Reststoffe oftmals verbrannt. Vom Brennen muss abgeraten werden, da die organische Substanz verloren geht und gleichzeitig ein Verlust der flüchtigen Elemente wie Stickstoff und Schwefel erfolgt, nur bei einer absoluten Notwendigkeit zur Schädlingsbekämpfung sollten die Reststoffe verbrannt werden. Im Sudan werden jährlich am Ende eines jeden Vegetationsperiode landwirtschaftliche Reststoffe vernichtet; insbesondere Baumwollrückstände werden jährlich verbrannt, um die Ausbreitung von Bakterien und der Knollenfäule, die 35% Verluste in der nachfolgenden Saison verursacht, zu verhindern.Diese Studie wurde in zwei Teilen durchgeführt, ein Labor- und Gewächshaus- Experiment am Department für Nutzpflanzenwissenschaften der Universität Göttingen, Deutschland, ein zweites Experiment an der Fakultät für Landwirtschaft der Universität Khartoum, Sudan. Verschiedene Versuche wurden durchgeführt: Auswertung von Kompostierungsversuchen der Baumwollrückstände, als reguläre, normale Kompostierung und als Vermikompostierung (Zusatz von Regenwürmer) und ein Phytoxizitäts-Bioassay-Test des fertigen Komposts und Vermikomposts, um ihre Eignung für landwirtschaftliche Anwendungen zu prüfen. Die Ergebnisse dieser Experimente führten zu einem Gefäßversuch, in mit Weidelgras die Nährstoffaufnahme untersucht wurde. Gleichzeitig wurde ein Stickstoff-Inkubationsexperiment durchgeführt, um die Rate des mineralisierten Stickstoffs aus Kompost und Vermikompost zu bewerten. Bei dem Versuch, eine Alternative zur Verbrennung von Baumwollstroh zu finden, wurde auch ein Experiment (Anzahl der Kolonie bildenden Einheiten von Mikroorgansimen) durchgeführt, welches die Wirksamkeit der Kompostierung und Vermikompostierung auf die bakterielle Braunfäule der Baumwolle überprüften sollte.Für diese Arbeit wurde Baumwollstroh aus den landwirtschaftlichen Betrieben der El-Gazira Bewässerungslandwirtschaft (El-Gazira State, Sudan) genommen, Bodenproben wurden aus dem Oberboden (0-30 cm) des Shambat Boden gezogen. Für die experimentellen Arbeiten im Sudan wurde Stallmist (FYM) aus einer Farm in der Nähe der Fakultät für Landwirtschaft, Universität Khartoum, Shambat, genutzt; aus dem Institut für Tierzucht, Universität Göttingen, Deutschland, wurde FYM für die Experimente in Göttingen genutzt.Eine regelmäßige Analyse der Kompostierungsvorgänge erfolgte durch Gesamt-C und Gesamt-N (trockene Verbrennung mittels einem Elementaranalysator) Bestimmungen; Ammonium- und Nitrat-Gehalte der feldfeucht gezogenen Proben erfolgte mittels Mikro-Kjeldahl Destillationsverfahren, die Summe bildete den mineralischen Stickstoff. Phosphor wurde nach der Molybdat-Blau-Komplex-Methode bestimmt und spektrophotometrisch gemessen. In einem Extrakt im Wasser-Kompost-Verhältnis 10:1 wurde die elektrische Leitfähigkeit und der pH-Wert bestimmt. Einige Makro- und Mikronährstoffe wurden in einem Verfahren unter Verwendung eines Druckaufschlusses gemessen.Verschiedene Studien wurden an der Universität Göttingen durchgeführt. Die erste Studie charakterisiert das kompostierte und vermikompostierte Baumwollstroh auf seine chemische Zusammensetzung und seinen agronomischen Wert und zielte darauf ab, (1) die chemischen Veränderungen während der Kompostierung und Vermikompostierung aus Baumwollstroh zu bestimmen; und (2) die Ergebnisse der chemischen Veränderungen mit den Daten des Bioassays-Tests zu korrelieren und (3) um die Qualität Parameter, die am besten einen fertigen Kompost und Vermikompost beschreiben, zu bestimmen.Die Ergebnisse dieses Teils zeigten, dass die Analysen des Komposts und des Vermikomposts eine breite Variation im pH-Wert, Gesamt-N, Gesamt-C, C/N-Verhältnis, elketrische Leitfähigkeit (EC) und Mineralstoffgehalt aufweisen. Der fertige Kompost und Vermikompost zeigte folgende Werte des C/N-Verhältnis: 15,4 und 15,2 für Kompost und Vermikompost; pH 6,6 für Kompost und 7,9 für Vermikompost und eine elektrische Leitfähigkeit (EC) von 2,96 dS m-1 und 1,62 dS m-1 für Kompost und Vermikompost, welches übliche Bereiche für reife Komposte sind (C/N: 15-20; pH: 5,5-8,0; EC: 4 dS m-1) mit Ausnahme der Werte NH4-N/NO3-N (1,57) der fertigen Komposte, die weit über den empfohlenen Wert (0,16) liegen, während der Wert des fertigen Vermikompost (0,1) unter dem Grenzwert liegt.Eine Korrelation zwischen NH4-N, NO3-N, EC, C:N, und pH wurde durchgeführt. Für den Vermikompost lagen die Korrelationskoeffizienten zwischen C/N-Verhältnis und      NH4-N, NO3-N, pH und EC mit r = 0,86 bei (P <0,01), -0,79 (P <0,01), 0,91 (P <0,01) und -0,77 (P <0,01). Die NH4-N-Konzentration war eng zum NO3-N korreliert (r =- 0,95, P <0,01). Die negative Korrelation zwischen NH4-N und NO3-N deutet darauf hin, dass das Material einer aktiven biologischen Zersetzung unterlag; dieses Ergebnis wurde mit dem NH4-N/NO3-N-Verhältnis bestätigt. Die signifikante negative Korrelation zwischen dem C/N-Verhältnis und dem NO3-N Wert (r =- 0,79, P <0,01), dem C/N-Verhältnis und dem NH4-N Wert gibt die Tendenz der Vermikompostierung wieder. Für den Kompost lagen die Korrelationskoeffizienten zwischen C/N-Verhältnis und NH4-N, NO3-N, pH und EC mit r = 0,88 bei (P <0,01), 0,94 (P <0,01), 0,59 (P = 0,02) und -0,72 (P <0,01). Die NH4-N-Konzentration war gut mit dem NO3-N Wert korreliert (r = 0,80, P <0,01). Diese Ergebnisse zeigen, daß die Reduktion im C/N-Verhältnis in der Zeit als ein zuverlässiger Parameter genommen werden kann, um den Fortschritt der Zersetzung darzustellen, wenn sie mit den Daten für NH4-N, NO3-N, pH und EC für den Vermikompost und mit den Daten NH4-N, pH und EC für den Kompost kombiniert werden.Organische Materialien können schädliche Auswirkungen auf Pflanzen oder keimenden Samen ausüben, daher wurde ein Phytotoxizitäts-Bioassay-Test als ein wichtiger Indikator für die Qualität durchgeführt, Ziel war es, eine Bewertung der Toxizität und eine Eignung des fertigen Komposts und Vermikomposts aus Baumwollstroh auf die Keimung von Kressesamen zu erhalten. Die Auswirkungen von Wasser-Extrakten verschiedener Substrate wurden untersucht, wobei die gekeimten Samen ausgezählt und die Länge der Hauptwurzel der Kresse (Lepidium sativum L.) gemessen wurde. Die Indizes der Keimung für Vermikompost (> 80%) sind größer als empfohlene Werte für reife Komposte (> 70%), während der Kompost (> 50%) diese Werte nicht erzielte. Die Ergebnisse dieser Arbeiten zeigten, dass fertige Vermikomposte am besten in diesem Kresse Bioassay Test abschnitten und als „reife Komposte“ betrachtet werden können, während der Kompost negative Auswirkungen auf die Keimung der Samen zeigte, also noch nicht „reif“ war.Die Bewertung der fertigen Komposte und Vermikomposte erfolgte in einem Gefäßversuch mit Weidelgras. Ein gleichzeitiges Inkubations-Experiment zur Stickstoffmineralisierung erfolgte unter Laborbedingungen, um Kompost und Vermikompost in ihrer N-Freisetzung zu bewerten und auch die langfristigen Auswirkungen ihrer Anwendung vorherzusagen. Beide Experimente dienten zur Bestimmung der Leistung von Kompost und Vermikompost auf das Pflanzenwachstum nach einmaliger Anwendung, die Prüfung der Zuverlässigkeit des N-Schicksals erfolgte durch das Inkubations-Experiment zur Beurteilung des potenziell mineralisierbaren Stickstoffs. Der Gefäßversuch erfolgte unter natürlichen Lichtbedingungen und der Umgebungstemperatur. Um dieses zu erreichen, wurde der Gefäßversuch im Gewächshaus des Departments für Nutzpflanzenwissenschaften durchgeführt. Kompost und Vermikompost entsprachen einer 4 g und 8 g N-Gabe pro Topf. Der Kompost und Vermikompost des Gefäßversuches wurde auch zur Inkubation genutzt.Daten aus dem Gefäßversuch zeigten, dass sowohl in den Kompost als auch Vermikompost gedüngten Gefässen die Biomasseerträge nach der zweiten Ernte stark zurückgingen, signifikante Unterschiede (P <0,05) wurde nur für die erste, zweite und letzte Ernte bestimmt. Die Biomasse der ersten und der letzten Ernten der Töpfe mit Vermikompost in der 4 g N/Topf Variante (VER1) entsprachen 1,4 und 0,1 g kg-1, während die Weidelgraserträge im Vermikompostversuch 8 g N/Topf (VER2) 0,8 g kg-1 für die erste Ernte und 0,2 g kg-1 ergaben., jeweils Weidelgras Biomasse auf Töpfen ausgesät mit Kompost entsprach geändert 8 g N pot-1 (CPF2) waren 1,4 g kg-1 bei der ersten Ernte und 0,3 g kg-1 für die letzte. Der beobachtete Rückgang der Biomasse in allen Töpfen mit Kompost oder Vermikompost nach 30 Tagen scheint das Ergebnis einer extremen Verknappung des verfügbaren N zum Weidelgraswuchs sein, besonders in den Gefäßen, die mit dem Vermikompost gedüngt wurden. Dieses wurde durch die sichtbaren Zeichen des N-Mangels (Chlorose) unterstützt.Die Ergebnisse zeigten auch, dass sowohl für Kompost und Vermikompost Varianten die Gesamt-N Gehalte des Weidelgrases dem Trend in der Biomasse folgten, wo die höheren N-Gehalte in ersten Ernte beobachtet wurden und die niedrigsten in der letzten. Die N-Gehalte waren je nach Kompostgaben 6,1-6,4% für die Ernte nach 10 Tagen und 2,4-2,9% für die Ernte nach 70 Tagen. Die N-Gehalte in den Vermikompost gedüngten Varianten lagen bei 3,7-4,0% für die Ernte nach 10 Tagen und 1,9-2,1% für die Ernte nach 70 Tagen. Die N-Gehalte des Weidelgrases der Kompost-Variante lag innerhalb der ausreichenden Versorgung (3-4,2%) N für ein normales Wachstum, während die Werte der Vermikompost gedüngten Varianten diesem Bereich nur zur Ernte nach 10, 60 und 70 Tagen erfüllten. Die Effizienz der N-Aufnahme war gering (>80% der N wurde nicht durch die Ernte genutzt).Die Ergebnisse des N-Inkubations-Experiment zeigte, dass die Höchst-und Mindestwerte des mineralischen N zwischen den Kompost- und Vermikompost-Aufwandmengen variierten. Dementsprechend betrugen die Werte für die 4 g N Variante VER1 9,41 bis 44 mg N kg-1; 13,2 bis 51,0 mg N kg-1 für die Vermikompost-Variante 8 g N Topf-1 (VER2), 7,2 bis 27,4 mg N kg-1 für die Kompost-Variante, entsprechend 4 g N Topf-1 (CPF1) und 4,2 bis 46,0 mg N kg-1 für die Kompost-Variante entsprechend 8 g N Topf-1 (CPF2).Die Netto-N-Mineralisierung am Ende der Inkubationszeit war signifikant (P <0,001) zwischen den Kompost- und Vermikompost – Varianten und deren Aufwandmengen. Die Böden, die mit Vermikompost entsprechend 4 g N Topf-1 (VER1), Vermikompost entsprechend 8 g N Topf-1 (VER2) und Kompost entsprechend 8 g N Topf-1 (CPF2) behandelt wurden, erfuhren eine Netto-N-Mineralisierung, die etwa doppelt so hoch war als bei Böden mit Kompost entsprechend 4 g N Topf-1 (CPF1). Allerdings gab Ergebnisse der N Inkubationsexperiment allgemeine Hinweise auf N-Verfügbarkeit für Nutzpflanzen und schlug vor, dass Anwendung von Kompost und vermicomposted Baumwolle Rückstände für einen Zeitraum von mehr als drei Wochen vor der Aussaat die nachfolgenden Kulturen unterwerfen N, um Verluste können.Um eine Alternative zum Verbrennen des Baumwollstrohs zu finden, befasste sich ein Teil dieser Arbeit mit der Wirksamkeit von Kompost und Vermikompost zur Unterdrückung der bakteriellen Braunfäule. Infizierte Baumwolle-Rückstände wurden gesammelt und einer Kompostierung und Vermikompostierung unterzogen. Proben aus den Kompostierungen wurden monatlich gesammelt und in einem semi-selektiven Medium nach der Verdünnungsreihe Methode kultiviert. Die Pathogenität wurde als „Kolonie-bildende-Einheit“ pro Gewicht der frischen Probe nach 3-4 Tagen Inkubation unter optimalen Bedingungen ausgezählt und gewertet.Die Ergebnisse zeigten, dass die Reduzierung der Erreger (berechnet als Differenz zwischen der Pathogenität in den Komposten und der Kontrolle) erheblich variierte. Für den Kompost betrugen die Werte <2% nach 30 Tagen, > 40% nach 60 Tagen und rund 38% nach 150 Tagen der Zersetzung. Während für den Vermikompost die Reduzierungen > 10% nach 30 Tagen, > 22% nach 60 und > 88% für Proben bei 150 Tagen betrugen. Die Ergebnisse zeigten auch, dass die höchste Zahl Erreger während der ersten Probenahme gefunden wurde und mit der Zeit abnahmen (r = 0,71; P ≤ 0,0001). Diese Studie ergab, dass es sowohl der Kompostierung und der Vermikompostierung gelungen ist, die Kolonie-bildenden Einheiten (CFU g frisches Material-1) der Erreger zu vermindern. Ein möglicher Prozess, um die infizierten Baumwolle-Rückstände anstelle durch Verbrennung zu behandeln.Insgesamt ergibt die Arbeit: (1) die Kompostierung und Vermikompostierung sind ein möglicher Prozess, um die infizierten Baumwoll-Rückstände zu behandeln, anstatt sie zu verbrennen, (2) die Reduktion des C/N-Verhältnisses im Laufe einer Kompostierung als einen zuverlässigen Parameter zum Fortschritt in Zersetzung zu nehmen, besonders, wenn sie mit den Daten NH4-N, NO3-N, pH und EC der Vermikompostierung kombiniert und mit den Daten NH4-N, pH und EC für die Kompostierung kombiniert wird, (3) dass 240 Tonnen ha-1 des fertigen Kompost und Vermikompost als Richtschnur für die Landwirtschaft angenommen werden können. Darüber hinaus schlug diese Arbeit einfache und praktische Verfahren für die Kompostierung und Vermikompostierung der organischen Abfälle, die aus lokalen Ernterückständen stammen, vor und Verfahren zur Regenwurmzucht für die Vermikompostierung und verschiedene andere Zwecke.
114

Milk production and nitrogen partitioning in dairy cows grazing standard and high sugar perennial ryegrass with and without white clover, during spring and autumn : a thesis presented in partial fulfilment of requirements for the degree of Master of Applied Science in Animal Production at Massey University, Palmerston North, New Zealand

Lazzarini, Maria Belen January 2010 (has links)
Two field grazing experiments were conducted in New Zealand (NZ) in spring (Experiment 1; November 2008) and autumn (Experiment 2; April 2009) to evaluate the effects of feeding a high sugar perennial ryegrass (HSG; cv. AberDart; derived in the United Kingdom; UK) versus a NZ- derived control grass (cv. Impact) on milk production and estimated nitrogen (N) partitioning within the cow. Areas of both ryegrasses were replicated and sown with or without white clover (cl) (HSG+cl, control+cl, HSG and control). A cross-over design with four 10-day periods was used in each experiment, using 15 Friesian cows per treatment per period in Experiment 1 and 5 cows per treatment per period in Experiment 2. Treatment effects upon pasture botanical and chemical composition, cows’ milk yield and composition, and estimated N partitioning were studied. Nitrogen partitioning was calculated using indirect methods. Herbage concentrations of water soluble carbohydrates (WSC) were lower in autumn than in spring whilst crude protein (CP) concentrations were higher in autumn. Organic matter digestibility (OMD) and metabolisable energy (ME) concentration was similar in both seasons. There were no differences in the concentration of CP, WSC and dry matter (DM) among treatments in Experiment 1. The HSG+cl treatment had the lowest concentrations of neutral detergent fibre (NDF, 417 g/kg DM) and the highest content of ME (12.6 MJ/kg DM) and tended to have the lowest sward dead matter content compared with the other three treatments. In Experiment 2 both HSG treatments showed higher concentrations of WSC (15 g/kg DM) compared with the control, both with and without clover; the concentrations of NDF and acid detergent fibre (ADF) were the lowest for both HSG treatments. In Experiment 1, cows grazing treatments with white clover produced more milk (1.6 kg/day) and more milk solids (MS; 0.16 kg/day) than cows grazing pure ryegrass swards ( P< 0.01), with highest milk yields being from cows grazing the HSG+cl treatment (ryegrass cultivar x white clover interaction P<0.05). No differences in milk production were found in Experiment 2. Estimated urinary N excretion (g/day) was similar for all treatments in both seasons, although N intake differed among treatments. The proportion of N intake excreted in urine or secreted in milk was similar for all treatments in both experiments. Nitrogen output (g/day) in milk was the highest for the HSG+cl treatment in Experiment 1 but no differences were found in Experiment 2. Data were combined from both experiments to study the effects of the herbage CP:WSC ratio upon estimated N partitioning between milk and urine. Mean ratios were 0.72 for spring herbage and 2.27 for autumn herbage. As the amount of WSC increased in the diet relative to the amount of CP (thus a lower CP:WSC ratio) there was a significant increase in the amount of milk N secreted per unit of N intake in spring but not in autumn. The breakpoint in the relationship between the herbage CP:WSC ratio and the nitrogen utilisation efficiency for milk production (NUEm) was 1.32, and the NUEm for that breakpoint was 14 g milk N per 100 g N intake. Ratios below this point were associated with improved efficiency of converting pasture N to milk N; ratios above this point were not correlated with changes in N conversion efficiency. It is concluded that the CP:WSC ratio in perennial ryegrass may be important in the partition of absorbed N into milk or urine. A NZ-selected HSG with a lower CP:WSC ratio is likely to have major benefits for pastoral farming in NZ. In order to be effective, a NZ-derived HSG should substantially increase WSC concentration in autumn pasture (from approximately 100 to 200 g/kg DM) whilst reducing CP content simultaneously (from 240 to 190 g/kg DM). The lower structural fibre and higher milk production for the HSG+cl treatment in both experiments suggest that under NZ conditions, best productive responses to HSG may be obtained in management systems that include white clover.
115

Forage quality, animal performance, and carcass traits of steers finished on winter annual ryegrass (Lolium multiflorum Lam.) pasture with varying levels of corn supplementation

Roberts, Sean David, Kerth, Christopher R. January 2005 (has links) (PDF)
Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.
116

Comercialização de sementes pela Cooper A1 / Marketing seeds by Cooper A1

Morandin, Winícius Assis Müller 16 May 2014 (has links)
Submitted by Maria Beatriz Vieira (mbeatriz.vieira@gmail.com) on 2017-03-03T14:00:25Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) dissertacao_winicius_assis_muller_morandin.pdf: 1347920 bytes, checksum: f9411aac4f89bd14b9c36aaee64a78f7 (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-03-09T17:53:45Z (GMT) No. of bitstreams: 2 dissertacao_winicius_assis_muller_morandin.pdf: 1347920 bytes, checksum: f9411aac4f89bd14b9c36aaee64a78f7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-03-09T17:54:51Z (GMT) No. of bitstreams: 2 dissertacao_winicius_assis_muller_morandin.pdf: 1347920 bytes, checksum: f9411aac4f89bd14b9c36aaee64a78f7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-03-09T17:55:02Z (GMT). No. of bitstreams: 2 dissertacao_winicius_assis_muller_morandin.pdf: 1347920 bytes, checksum: f9411aac4f89bd14b9c36aaee64a78f7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2014-05-16 / Sem bolsa / A empresa Cooper A1 tem sua matriz localizada na cidade de Palmitos – SC, atua com 16 filiais no Oeste de Santa Catarina e Noroeste do Rio Grande do Sul. Iniciou a atividade na década de 1930, onde conseguiu despertar o interesse dos primeiros 18 agricultores em investir no negócio. A Cooper A1 é a cooperativa de produção mais antiga do Estado de Santa Catarina de funcionamento ininterrupto. Recebe uma média anual superior a 167 mil toneladas de milho, mais de 20 mil toneladas de soja e mais três mil toneladas de trigo. A maior parte da produção recebida é dos associados, sendo que a cooperativa também adquire grãos de outros mercados para suprir a demanda de matéria prima para fabricação e formulação de rações em suas fábricas. Atualmente, a capacidade estática de armazenamento de grãos da Cooper A1 é superior a 1,3 milhões de sacas. Já a capacidade de secagem foi expandida para mais de 60 mil sacas/dia. Esta grande capacidade, permite que o associado decida quanto tempo seu produto fica armazenado, podendo escolher a melhor época para comercializar sua produção. O trabalho objetivou uma avaliação técnica e comercial da empresa Cooper A1 com ênfase na comercialização de sementes de Soja, Aveia, Trigo, Azevém e Capim-Sudão. Coletaram-se dados da comercialização dessas culturas, dos anos de 2007 à 2011, formando um banco de dados que auxilia nas decisões futuras para implantação de uma Unidade de Beneficiamento de Sementes. No decorrer desses anos, a venda de sementes aumentou gradativamente, e a perspectiva de aumento da área de abrangência de atuação da Cooper A1, principalmente no estado do Rio Grande do Sul, verificam-se reais possibilidades de aumento na comercialização de sementes, caracterizando um forte indicador da possibilidade de entrada da empresa no negócio de produção de sementes. / The company Cooper A1 has its matrix located in the city of Palmitos – SC, operates with 16 branches in the West of Santa Catarina and Northwest of Rio Grande do Sul states. Started the activity in the 1930 s, where managed to arouse interest of the first 18 farmers to invest in the business. The Cooper A1 is the oldest cooperative production of the State of Santa Catarina uninterrupted operation. Receive an annual average of more than 167 thousand tons of corn, more than 20 thousand tons of soy and more three thousand tons of wheat. The greater part of the production received is of the Associates, being that the cooperative also acquire grain from other markets to supply the demand of raw material for manufacture and formulation of ration in its factories. Currently, the static capacity of grain storage of Cooper A1 is greater than 1.3 million bags. Already drying capacity was expanded to more than 60 thousand bags/day. This large capacity allows the associated decide how long your product is stored, choosing the best time to market their production. The work aimed to evaluate the technical and commercial company Cooper A1 with emphasis on commercialization of seeds of soy, oats, wheat, ryegrass and Sudão grass. Data were collected on the marketing of these crops the years from 2007 to 2011, forming a database that helps future decisions for implantation of a Unit of Seed Processing. During those years, the sale of seeds increased gradually, and the prospect of increasing area of operation of the Cooper A1, mainly in the state of Rio Grande do Sul, real possibilities of increase commercialization of seeds, characterizing a strong indicator of the possibility of entry of the company in the business of producing seeds.
117

Introdução de uma mistura de três espécies forrageiras de inverno em pastagem irrigada de capim-aruana. / Introduction of a mixture of three winter forage species in an irrigated aruanagrass pasture.

Luciana Gerdes 13 November 2003 (has links)
No Instituto de Zootecnia, Nova Odessa, SP, em uma pastagem de capim-aruana (Panicum maximum Jacq. cv. Aruana) utilizada com ovinos em sistema intensivo de produção (irrigação, adubação e lotação rotacionada), foram sobre-semeadas as espécies forrageiras de inverno: aveia preta (Avena strigosa Schreb cv. Comum), azevém anual (Lolium multiflorum Lam. cv. Comum) e trevo branco (Trifolium repens L. cv. Zapicán) com o objetivo de suprir o déficit e melhorar o valor nutritivo da forragem no período crítico do ano. A sobre-semeadura foi efetuada em 14/04/00 e 07/06/01 no primeiro e segundo anos do experimento, respectivamente. Nos dois anos (14/04/00 a 18/01/01 e 07/06/01 a 22/02/02) foram avaliados, em seis períodos de pastejo: massa total de forragem pré-pastejo, sua composição botânica e porcentagem de lâminas foliares, massa de forragem pós-pastejo, acúmulo de forragem (AF) e taxa média diária de acúmulo de forragem (TMDAF) em cada período de rebrotação, altura do dossel forrageiro pré e pós-pastejo, características químicas: proteína bruta (PB), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), lignina e digestibilidade “in vitro” da matéria seca (DIVMS), nas amostras da massa total de forragem e nas dos componentes botânicos (aruana, aveia preta e azevém) pré-pastejo. O delineamento experimental foi o de blocos completos casualizados (quatro), com duas repetições dentro do bloco e dois tratamentos: 1) capim-aruana exclusivo (AE) e 2) sobre-semeadura da mistura das três espécies forrageiras de inverno (MFI). Os blocos eram pastejados pelo mesmo lote de animais, em sequência, por dois a três dias, até atingir 10 a 15 cm. O trevo-branco não se estabeleceu em ambos os anos. No primeiro ano, a pastagem MFI apresentou maior massa total de forragem do que a pastagem AE no segundo período e na média dos seis períodos. A aveia apresentou a maior contribuição no segundo período e o azevém no terceiro. As pastagens com a MFI apresentaram maiores AF e TMDAF que as pastagens de AE no segundo, quinto e na média dos seis períodos. A PB da forragem na pastagem de capim-aruana exclusivo foi maior em relação à sobre-semeada no terceiro período de pastejo e semelhante nos demais. A PB dos componentes aveia e azevém, no terceiro período, foi menor em relação aos do primeiro e segundo. FDN, FDA e lignina da forragem no tratamento exclusivo foram mais elevados em relação aos do tratamento sobre-semeado, na média dos seis períodos. Aveia e azevém apresentaram FDN mais baixos nos períodos iniciais de crescimento, com aumento no último. A digestibilidade da forragem foi semelhante nos dois tratamentos, em todos os períodos de avaliação. No segundo ano, a massa total de forragem apresentou quantidades semelhantes entre as duas pastagens ao longo dos seis períodos e na sua média. A aveia esteve mais presente no primeiro período e o azevém no terceiro. Não houve diferença entre tipos de pastagem para AF e TMDAF em nenhum dos seis períodos, nem na sua média. Para o componente aruana a porcentagem de lâminas foi semelhante entre os dois tipos de pastagem e para a aveia e azevém, as menores porcentagens ocorreram no período final dos seus ciclos vegetativos, em ambos os anos. O teor de PB da massa total de forragem da pastagem de capim-aruana exclusivo foi maior que o da pastagem sobre-semeada, no quarto período mas semelhante nos demais e na média dos períodos. Os teores de PB da aveia e do azevém decresceram ao longo dos períodos de pastejo. Os teores de FDN, FDA, lignina e DIVMS da forragem foram semelhantes entre as duas pastagens na média e ao longo dos seis períodos, exceto para FDN no segundo período. A aveia e o azevém apresentaram os maiores teores de FDN, FDA e lignina no último período de pastejo. A DIVMS do azevém manteve-se constante nos dois primeiros períodos de pastejo diminuindo no último. Pastos de capim-aruana convenientemente adubados e irrigados, que recebam sobre-semeadura com espécies forrageiras de inverno, produzem mais forragem no período crítico mas com valor nutritivo semelhante em relação a pastos não sobre-semeados, nas condições do Estado de São Paulo. Pastos deste capim, não sobre-semeados, mas que recebam adubação e irrigação também apresentam boa produção e valor nutritivo nesta época. / At Instituto de Zootecnia, Nova Odessa, SP, in a pasture of aruanagrass (Panicum maximum Jacq. cv. Aruana), grazed by sheep in an intensive production system (irrigation, fertilization and rotational stocking), it was introduced a three winter forage species: black oat (Avena strigosa Schreb. cv. Common), italian ryegrass (Lolium multiflorum Lam. cv. Common) and white clover (Trifolium repens L. cv. Zapican) with the objective of increasing the forage supply and its nutritive value during the dry winter period. The mixture was broadcasted sown over the grass on 04-14-00 and 06-07-01 in two years of experiment. From 04-14-00 to 01-18-01 and 06-07-01 to 02-22-02 it was evaluated, in six annual grazing periods, the forage mass, its botanical composition and leaf blades percentage pre grazing, residual mass post grazing, forage accumulation (FA) and mean forage accumulation daily rate (MFADR) in each regrowth period and sward heigth pre and post grazing, the chemical characteristics: crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin and in vitro dry matter digestibility (IVDMD) in the forage on offer and in its botanical components. The experimental design was a completely randomized block (four) with two replications within the block. The treatments were: 1) grass alone and 2) the grass oversown with the mixture of the winter forages. The blocks were grazed by the same group of sheep in sequence for two or three days until the sward height reached to 10-15 cm. The white clover did not establish. In the first year the oversown treatment presented higher total forage mass than the control in the second periods and in the mean of the six periods. The black oat presented higher contribution in the second period and italian ryegrass in the third. The oversown pastures presented higher FA and MFADR than the single aruanagrass pastures, in the second, fifth and in the mean of the six periods. The CP in the forage from the grass pasture alone was greater than the one of the oversown pasture in the third period, and similar in the others. Oat and ryegrass CP was lower in the third period than the ones of the first and second ones. NDF, ADF and lignin in the forage from the grass pasture alone were greater than the ones of the oversown pasture. Oat and ryegrass NDF was lowest in the initial growth periods, increasing in the final. Forage IVDMD from the two treatments were similar in all evaluation periods. In the second year, the total forage mass was similar in the two pasture treatments in all grazing periods and in their means. The black oat contribution was higher in the first period and the one of italian ryegrass in the third. The FA and the MFADR were similar in the two pasture systems. The leaf blades percentage of aruanagrass was similar in the two pastures in all periods and the ones of black oat and italian ryegrass were lower in the final period compared to the preceeding ones, in the two years. The CP in the forage from the grass pasture alone was greater than the one of the oversown pasture in the fourth period, and similar in the others. Oat and ryegrass CP decreased along the grazing periods. NDF, ADF, lignin and IVDMD of the forage from the two treatments were similar in all evaluation periods. Oat and ryegrass NDF, ADF and lignin were greater in the last grazing period. Ryegrass IVDMD from the first two periods were similar and decreased in the final. For the São Paulo State conditions, adequately fertilized and irrigated aruanagrass pastures, when oversown with winter annual forages, yield more than single aruanagrass ones during the dry winter period but with similar nutritive value. Single aruanagrass pastures when fertilized and irrigated present also good forage yields with good nutritive value during this time.
118

Plant Fungal Endosymbionts Alter Host-Parasite Relationships Between Generalist Herbivores (Lepidoptera: Noctuidae) and An Entomopathogenic Nematode

Kunkel, Brian A. 19 March 2003 (has links)
No description available.
119

<b>SUPPLEMENTAL IRRIGATION PROGRAM EFFECTS ON VARIOUS LAWN GRASSES IN THE COOL-HUMID ZONE</b>

Antonio Verzotto (18429612) 23 April 2024 (has links)
<p dir="ltr">Water scarcity and acute drought continue to be serious concerns, even in humid climates where precipitation normally exceeds evapotranspiration (ET), highlighting the need for improved landscape water conservation practices. Lawns represent the largest area in most managed landscapes and require regular mowing, feeding and sometimes supplemental summer irrigation to persist. A general historical guideline for lawn irrigation is to supply 25-38 mm per growing wk-1 in the absence of rainfall. This fixed volume is often applied on a programmatic “set and forget” three times per week schedule (e.g. M-W-F). This application guideline often results in excess irrigation as it does not take into account plant need or prevailing environmental conditions. Further, in times of acute summer drought policymakers may restrict irrigation to once or twice weekly to conserve water. The effects of these regulations on turf health and potential water savings are unclear. Thus, two multi-year summer field studies were conducted to identify opportunities for improved lawn water conservation. Study one evaluated the effect of varying weekly irrigation volume and frequency on mature Kentucky bluegrass (Poa pratensis L.:KBG) located under a fixed-roof rainout structure. Turfgrass response was measured as visual turf quality (TQ), digital green color (DGC), volumetric soil water content (VWC) and area under the curve for each response variable. In year one, KBG was subject to six irrigation programs and compared to a high deficit control for 49 days. The programs were: 25 mm total water wk-1 applied either three times (M-W-F) or twice (M and F) weekly, 19 mm total wk-1 twice weekly (M and F), 13 mm total wk-1 once weekly and 60 or 80% accumulated ETo three times weekly. Due to poor performance, the high deficit control and 60% ETo were excluded from further evaluation. In year two, seven programs were evaluated: 33 mm total water wk-1 applied once, twice, or three times weekly, or every-other-day, 25 mm total wk-1 applied twice or three times weekly and 80% ETo twice weekly for 63 days. In both years, generally, 25-33 mm wk-1 applied two or three times wk-1 produced the most consistent TQ, DGC and highest VWC. Study two compared three supplemental irrigation programs to a natural rainfall control for six widely planted cool-season lawn grasses for 70 days. The six lawn grasses were: a KBG sod, seeded drought tolerant and susceptible KBG cultivars, a turf-type tall fescue (Schedonorus arundinaceus (Schreb.) Durmort.: TTTF) blend and two KBG and perennial ryegrass (Lolium perenne L.:PRG) mixtures. In Study two, highly significant differences p < .001 occurred for irrigation program and lawn grasses. While supplemental irrigation aided all grasses, rainfall in year one and two measured 119 mm and 343 mm, respectively, affecting data in each study year. Area under the turfgrass quality curve (AUTQC) was lowest for the rainfall control (339 and 425) and highest for 33 mm wk-1 applied three times (507 and 526) and 80% ETo programs (508 and 535) in year one and two, respectively. Annual responses for DGC and VWC generally followed TQ trends. For grasses subject only to natural rainfall, TTTF, and the KBGs were generally superior to the KBG:PRG mixtures, thus emphasizing the importance of species selection. In summary, these studies compared a traditional “set and forget” irrigation program to a range of alternative programs and different lawn grasses. These data provide evidence for irrigation savings by employing a combination of planting drought tolerant lawn species and adopting a more limited irrigation program. Future field studies should include the evaluation of adaptive, data-driven programs based on forecast environmental conditions and threshold responses like DGC or predetermined VWC set points calibrated for varying soil types and growing environments.</p>
120

Contamination atmosphérique par les hydrocarbures aromatiques polycycliques : toxicité et devenir du phénanthrène dans des systèmes sol-plante-microorganismes / Atmospheric contamination bu polycyclic aromatic hydrocarbons : toxicity and fate of phenanthrene in soil-plant-microorganism systems

Desalme, Dorine 22 June 2011 (has links)
Les hydrocarbures aromatiques polycycliques (HAP) sont des polluants organiques persistants potentiellement mutagènes et cancérigènes. Leur transfert de l’atmosphère vers les écosystèmes, notamment vers les plantes, conditionne leur entrée dans les chaines alimentaires mais les modalités de ce transfert restent encore mal connues. L’objectif de ce travail était donc de caractériser le transfert et d’identifier les effets biologiques des HAP atmosphériques sur un système sol-plante-microorganismes symbiotiques.Un dispositif expérimental a été conçu afin de recréer en laboratoire une pollution atmosphérique par les HAP avec comme HAP modèle le phénanthrène (PHE). Le dispositif a fait l’objet d’une validation et d’une calibration élaborée de manière originale par une double approche mêlant l’expérimental à la simulation mathématique. Les niveaux d’exposition en polluant (150 µg m-3), contrôlés par des échantillonneurs passifs, se sont avérés pertinents par rapport aux conditions in situ. Ce dispositif a donc été utilisé pour exposer durant un mois des microsystèmes sol-plante-microorganismes au PHE par voie atmosphérique.Les différentes études ont mis en évidence un transfert du PHE depuis l’atmosphère vers tous les compartiments du microsystème, avec une accumulation majeure vers les feuilles de trèfle ou de ray-grass (respectivement 170 et 70 µg g־ ¹MS) et un transfert phloémien vers les racines est suggéré. Chez le trèfle, la mycorhization n’a pas été affectée, tandis que le nombre de nodules actifs a diminué de manière significative. Contrairement aux racines, la biomasse aérienne du trèfle a été significativement affectée (environ – 25%) par l’exposition au PHE atmosphérique, suggérant un impact sur le métabolisme carboné de la plante. Une expérience de marquage des trèfles au ¹³C-CO2 a effectivement montré un impact négatif du PHE atmosphérique sur la croissance, l’allocation de biomasse et l’allocation carbonée. Pour conclure, ces études ont permis non seulement de caractériser les effets biologiques et physiologiques des HAP atmosphériques sur les végétaux mais également de proposer l’utilisation du potentiel mycorhizien comme indicateur de pollution atmosphérique par les HAP. / Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants potentially mutagenic and carcinogenic. Transfer from the atmosphere to ecosystems, especially to plants, conditioning their entry into food chains, but the terms of this transfer are still poorly understood. The aim of this study was to characterize the transfer and identify the biological effects of atmospheric PAHs on soil-plant-symbiotic microorganisms.An experimental device was designed to recreate in the laboratory air pollution with phenanthrene (PHE) as a model PAH. The device was been validated and a calibration developed in an original way by a dual approach combining the experimental mathematical simulation. The levels of exposure to pollutant (150 mg m־³), controlled by passive samplers, were relevant with field conditions. This device has been used to expose a month of the soil-plant micro-organisms in the PHE through the air.Various studies have demonstrated a transfer of PHE from the atmosphere to all compartments of the microsystem, with a major accumulation to leaves in clover or ryegrass (respectively 170 and 70 µg g ־¹ dry weight) and a phloemic transfer to the roots is suggested. In clover, mycorrhization was not affected, while the number of active nodules decreased significantly. Unlike roots, aboveground biomass of clover was significantly affected (approximately – 25%) by exposure to air PHE, suggesting an impact on the carbon metabolism of the plant. A labelling experiment with ¹³C- CO2 in clover has actually shown a negative impact of PHE air on growth, biomass and carbon allocation.In conclusion, these studies have not only characterized the biological and physiological effects of atmospheric PAHs on plants but also proposed the use of mycorrhizal potential as an indicator of air pollution by PAHs.

Page generated in 0.0587 seconds