Développement et validation du Terra-22, un système d’échantillonnage de sol aéroporté

L’échantillonnage de sol est utilisé en agriculture pour suivre les besoins en nutriments et planiőer l’application d’engrais. Cette tâche est généralement effectuée manuellement, mais des robots terrestres ont récemment été introduits pour cette tâche. Cependant, ces robots sont souvent lents et lourds, ce qui contribue au compactage du sol. Les drones pourraient constituer une alternative intéressante aux robots terrestres en raison de leur vitesse et manœuvrabilité élevée. Toutefois, les drones sont sévèrement limités dans leur charge utile et dans les forces qu’ils peuvent appliquer au sol. Ce mémoire présente le Terra 22, le premier système aéroporté capable d’échantillonner des sols agricoles densément compactés. Pour ce faire, de nombreux déős ont été relevés, notamment le développement (i) d’un système de forage à haute densité de puissance qui surpasse de 39 % celle des assemblages moteurs/boîte de réduction à courant continu classique, (ii) d’une mèche 48 % plus légère que les mèches en acier traditionnelles et qui maintient la contamination croisée en dessous de 4 %, et (iii) un contrôleur de vitesse de pénétration de forage qui réduit le couple requis de 33 % et la force axiale requise par un facteur huit par rapport à un contrôleur de vitesse de pénétration constante. Des tests d’échantillonnage de sol en extérieur dans un champ de maïs (sol limono-sableux, compactage entre 0,8 MPa et 2 MPa) ont démontré un taux de réussite de 94 % sur terrain plat et une durée d’échantillonnage inférieure à une minute, permettant la collecte de plusieurs échantillons par vol

Developmental aspects of Gigaspora rosea and Glomus etunicatum, alone or in association with Alnus glutinosa

Attempts were conducted to establish in vitro vesicular-arbuscular mycorrhizal (VAM) associations under gnotobiotic conditions. Alnus glutinosa (L.) Gaertn. served as the host in the form of whole plants, root organs, and undifferentiated callus. Spores of Gigaspora rosea Nicolson and Schenck or Glomus etunicatum Becker and Gerdemann were utilized as VAM fungus (VAMF) inoculum. Limited VAM associations were attained within certain in vitro culture systems that contained intact seedlings or root organs. In addition, whole seedling cultures exhibited occasional sporulation by Gl. etunicatum;The influences of chloramphenicol (150, 75, and 35 ppm), gentamicin sulfate (100 and 50 ppm), streptomycin sulfate (50 and 25 ppm), and penicillin G potassium (50,000 and 25,000 units/L) upon spore germination and hyphal growth by the two VAMF species also were evaluated in 1% water agar. Germination of Gl. etunicatum chlamydospores was inhibited by gentamicin, and hyphal growth was sensitive to higher concentrations of chloramphenicol and gentamicin. Higher levels of chloramphenicol also reduced germination and hyphal growth of Gi. rosea. Effects of other antibiotics were dependent upon their concentration and VAMF species. No significant correlation was found between spore diameter and hyphal growth for either VAMF species. Hyphal growth by Gi. rosea was, however, highly correlated with the number of extra-matrical vesicle clusters that were produced upon each hypha. When extra-matrical vesicle clusters became separated by a septum from the parental hypha, they occasionally generated a new radial mass of thin hyphae. Chlamydospores of Gl. etunicatum occasionally germinated directly through the spore wall, and hyphae from separate spores in close proximity frequently anastomosed;Light and scanning electron microscopy were utilized to observe various anatomical aspects in the development of Gi. rosea and Gl. etunicatum. These VA mycobionts were examined in an independent state and in association with roots of A. glutinosa

Tree Growth and Cattle Weight Gain in a Ponderosa Pine System

Integrated timber and livestock systems (silvopastoral) are common in several regions of the United States. Grazing of three timber stands in eastern Nebraska showed no signs of tree damage due to rubbing or soil compaction. Steer gains were lower under the silvopastoral system compared to a typical pasture system (1.05 lb/day versus 1.70 lb/day). Growth of timber in silvopastoral stands was reduced (35.0 cubic feet per year versus 37.8 cubic feet per year); however, total productivity of the silvopastoral system (timber plus livestock) was greater ($20.98/acre) than with traditional timber systems

Registration of ‘Bonanza’ Big Bluestem

‘Bonanza’ big bluestem (Andropogon gerardii Vitman.) (Reg. no. CV-13, PI 641701) was released in May 2004 by the USDA-ARS and the Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska. It is a broadly adapted perennial warm-season grass cultivar that produces forage with high in vitro dry matter digestibility (IVDMD) and improved animal gains in comparison to its parent cultivar when utilized by beef cattle in well-managed grazing systems. Bonanza was tested as Pawnee C3

Registration of ‘Goldmine’ Big Bluestem

‘Goldmine’ big bluestem [Andropogon gerardii Vitman.] (Reg. no. CV-14, PI 641702) was released in May 2004 by the USDA-ARS and the Agricultural ResearchDivision, Institute of Agriculture and Natural Resources, University of Nebraska. Goldmine is a perennial warm-season grass cultivar that produces forage with moderately improved in vitro dry matter digestibility (IVDMD), protein concentration, and improved forage yields in some hay management systems. Animal gains from Goldmine were greater than its parent cultivar when utilized by beef cattle in well-managed grazing systems. Goldmine was tested as Kaw C3

Grazing Evaluation of Big Bluestems Bred for Improved Forage Yield and Digestibility

Two big bluestem (Andropogon gerardii Vitman) strains (Pawnee C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were compared with the base populations of \u27Pawnee\u27 and \u27Kaw\u27 in a 3-yr grazing trial. Pastures were seeded in May 1998 near Mead, NE. Experimental units were three 0.4-ha pastures of each strain or cultivar in a randomized complete block design. Pastures were burned and fertilized with ammonium nitrate at 112 kg N ha-1 in the spring of 2000, 2001, and 2002 before grazing. Each pasture was continuously stocked with three crossbred yearling steers (Bos taurus) (380 +/- 38 kg) in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 steers ha-1. Pawnee C3 and Kaw C3 produced 16 and 7% more average daily gain (ADG), respectively, than the base populations during the 3-yr study. Additionally, Pawnee C3 and Kaw C3 produced 14 and 5% more total body weight (BW) gain ha-1, respectively, than the base populations. Pawnee C3 ADG was 1.30 kg hd-1 and produced greater than 455 kg total BW gain ha-1 during a drought period in eastern Nebraska. Pawnee C3 pastures produced more available forage with higher IVDMD, cell soluble, cell wall digestibility, and lower lignin concentration than forages from Pawnee pastures. Kaw C3 pastures differed from Kaw pastures by producing forage with greater crude protein concentration. These results demonstrate the productivity of big bluestem pastures in the eastern Great Plains and document the positive livestock response to moderate increases in forage IVDMD. The strains bred for increased yield and IVDMD provided as much as 26% more total BW gain ha-1 at no additional cost. Pawnee C3 was released as the cultivar Bonanza and Kaw C3 was released as \u27Goldmine\u27

Impact of Cleaning Frequency on Nitrogen Balance in Open Feedlot Pens

Pen cleaning frequency of feedlot pens was evaluated during the summer of 2001 and 2002. Dry matter, organic matter and nitrogen recoveries were evaluated on a per head basis. Cleaning pens monthly compared to cleaning at the end of the feeding period resulted in significantly more DM, OM and N recovered. Cleaning pens every month increased N removal by 7.0 lb per steer (49.9% increase) above manure N removed at the end of the feeding period

Grazing Evaluation of Big Bluestems Bred for Improved Forage Yield and Digestibility

Two big bluestem (Andropogon gerardii Vitman) strains (Pawnee C3 and Kaw C3) developed by three breeding cycles for increased forage yield and in vitro dry matter digestibility (IVDMD) were compared with the base populations of \u27Pawnee\u27 and \u27Kaw\u27 in a 3-yr grazing trial. Pastures were seeded in May 1998 near Mead, NE. Experimental units were three 0.4-ha pastures of each strain or cultivar in a randomized complete block design. Pastures were burned and fertilized with ammonium nitrate at 112 kg N ha-1 in the spring of 2000, 2001, and 2002 before grazing. Each pasture was continuously stocked with three crossbred yearling steers (Bos taurus) (380 +/- 38 kg) in mid-June 2000, 2001, and 2002 to provide a stock density of 7.5 steers ha-1. Pawnee C3 and Kaw C3 produced 16 and 7% more average daily gain (ADG), respectively, than the base populations during the 3-yr study. Additionally, Pawnee C3 and Kaw C3 produced 14 and 5% more total body weight (BW) gain ha-1, respectively, than the base populations. Pawnee C3 ADG was 1.30 kg hd-1 and produced greater than 455 kg total BW gain ha-1 during a drought period in eastern Nebraska. Pawnee C3 pastures produced more available forage with higher IVDMD, cell soluble, cell wall digestibility, and lower lignin concentration than forages from Pawnee pastures. Kaw C3 pastures differed from Kaw pastures by producing forage with greater crude protein concentration. These results demonstrate the productivity of big bluestem pastures in the eastern Great Plains and document the positive livestock response to moderate increases in forage IVDMD. The strains bred for increased yield and IVDMD provided as much as 26% more total BW gain ha-1 at no additional cost. Pawnee C3 was released as the cultivar Bonanza and Kaw C3 was released as \u27Goldmine\u27

Undegradable Intake Protein Supplementation of Compensating Spring-Born Steers and Summer-Born Steers During Summer Grazing

Three trials were conducted to determine the effects of previous winter gain (Trials 1 and 3) and age of calf (Trials 1 and 2) on response to undegradable intake protein (UIP) supplementation during summer grazing. In Trial 1, 48 spring-born steers (243 kg) were used in a 4 &#;&#;2 factorial arrangement. Steers were wintered at four rates of gain: 0.65 (FAST), 0.24 (SLOW), 0.38 (S/F), and 0.38 (F/S) kg/d. The intermediate rates of gain (S/F and F/S) were created by switching steers from slow to fast or fast to slow midway through the wintering period. Following winter treatments, steers were assigned to one of two summer treatments: supplemented (S) or nonsupplemented (NS). In Trial 2, 32 summer-born steers were wintered at an ADG of 0.25 kg/d and allotted to the same summer treatments as Trial 1. The supplement was formulated to supply 200 g/d of UIP. Steers from both trials grazed upland Sandhills range from May to September 1998. In Trial 3, 49 spring-born steers (228 kg) were used in a 2 &#;&#;7 factorial arrangement of treatments. Steers were wintered at two rates of gain, 0.71 (FAST) and 0.24 kg/d (SLOW) and then assigned randomly to one of six levels of UIP supplementation or an energy control. Protein supplements were formulated to deliver 75, 112.5, 150, 187.5 225, or 262.5 g/d of UIP. Sources of UIP for all trials were treated soybean meal and feather meal. In Trial 1, there were no (P \u3e 0.05) winter by summer treatment interactions, and UIP supplementation increased (P = 0.0001) pasture gains over NS steers. In Trial 2, supplementation increased (P = 0.001) pasture ADG of summer-born steers by 0.15 kg/d compared with NS steers. In Trial 3, a winter gain by UIP supplementation interaction was observed (P = 0.09). Gain of FAST steers responded quadratically (P = 0.09) across UIP levels, with the maximum gain occurring at the 150 g/ d UIP level. The SLOW steers responded linearly (P = 0.02) to increasing UIP levels; however, the response was negative. Levels of UIP above 150 g/d reduced steers gains; therefore, the data were reanalyzed excluding these levels. These new analyses showed that FAST steers responded linearly (P = 0.08; 0.2 kg/d) to increasing UIP, whereas the SLOW steers had no response to UIP. In Trials 1 and 3, SLOW steers experienced compensatory gain and had higher gains overall. We concluded that previous winter gain affected the response to UIP supplementation with the FAST winter gain group having a greater response

Relationship Between Morbidity and Performance in Feedlot Cattle

Five datasets from Canada, Oklahoma, Illinois, and Nebraska were used to determine the impact of bovine respiratory disease (BRD) on performance, with emphasis on dry matter intake (DMI) and feed to gain ratio (F:G). Data included pens and individually fed cattle. In general, cattle treated for BRD had lower DMI and average daily gain (ADG) with little to no effect on F:G. When BRD occured early in the feeding period (days), little change in performance was observed