Farmers' irrigation practices in a high rainfall area

Recent droughts in the humid southeastern United States have focused attention on the need for and use of supplemental irrigation. Total annual rainfall amounts are sufficient for most crops in the region. However, erratic distribution of rainfall and the low water-holding capacities of most soils in the region cause frequent drought stresses in many crops. An on-farm study was conducted in southeastern Alabama to evaluate the effects of farmers' irrigation scheduling decisions on soil moisture variations in peanut fields irrigated with center-pivot irrigation systems. The study showed that the way irrigation was practiced in this high rainfall area often caused soil moisture deficit (SMD) level higher than the desired SMD limit during over 20% of the 140-day growing season. This is partially due to farmers' tendency to delay irrigation in anticipation of rainfall which may or may not occur, as rainfall during the growing season is often erratic and local. In contrast SMD in non-irrigated fields was higher than the SMD limit for half of the growing season.Abbreviations SMD soil moisture deficit - ET evapotranspiration - R_eff effective rainfall - WHC water holding capacity     

Presence and viability of Ceratocystis lukuohia in ambrosia beetle frass from Rapid ʻŌhiʻa Death‐affected Metrosideros polymorpha trees on Hawaiʻi Island

Rapid ?ōhi?a Death (ROD) is a fungal disease of ?ōhi?a lehua (Myrtaceae: Metrosideros polymorpha) caused by Ceratocystis lukuohia and C. huliohia. ROD is the aetiological agent of widespread mortality of this important tree on Hawai?i Island, but its epidemiology remains unclear. We investigated the prevalence and viability of C. lukuohia in ambrosia beetle frass in ROD‐affected ?ōhi?a trees. A total of 200 frass traps were placed onto C. lukuohia‐infected ?ōhi?a at four locations on the east side of Hawai?i Island. Frass was collected and screened for the presence of C. lukuohia DNA using a diagnostic qPCR assay. In addition, frass samples were screened for viability by carrot baiting. All trapped beetles were of the genus Xyleborus, with the majority being the non‐native X. ferrugineus. Of the frass samples tested, 62% contained C. lukuohia DNA and 17% of carrot baits were positive for the fungus. These results indicate that ambrosia beetle frass releases C. lukuohia into the environment. We discuss the potential role infested frass could play in the ROD pathosystem.     

The effect of multi-nutrient fertilization on understory vegetation nutrient concentrations in inland Northwest conifer stands

This study looked at the effects that multi-nutrient fertilization had on understory vegetation nutrient concentrations at four conifer forested locations in the inland Northwest. Multi-nutrient fertilization of conifer stands cannot only enhance the overstory species in the inland Northwest but also the understory vegetation. Determination of nutrient concentration response to fertilization treatments can provide managers the ability to better manipulate their forests for grazing and wildlife habitat. We grouped the understory vegetation into three general life forms: forbs, grasses and grass-likes, and shrubs. Multi-nutrient fertilization had little effect on nitrogen concentration across all life forms. Potassium and sulfur generally increased in concentration. Micronutrients as a whole showed less variability in response to multi-nutrient fertilization. Boron, copper, molybdenum, and zinc generally showed increases in concentrations across all life forms. We were able to conduct analyses on a selected number of understory vegetation species. Individual species showed variability in nutrient concentration response to multi-nutrient fertilization. Wildlife habitat and grazing quality were both increased and decreased following multi-nutrient fertilization. Increases in nutrient concentrations will provide more nutritious vegetation to these animals and vice versa for decreases in concentrations.     

Effect of restricted postweaning growth resulting from reduced floor and feeder-trough space on pig growth performance to slaughter weight in a wean-to-finish production system

The effect of reduced pig growth rate postweaning as a result of restricted floor space and feeder trough space on subsequent growth to slaughter was investigated in a wean-to-finish system. Crossbred pigs (n = 1,728) were used in a randomized block design with a 2 x 2 x 2 factorial arrangement of treatments: 1) floor space (high [0.630 m2/pig] vs. low floor space [0.315 m2/pig]), 2) feeder trough space (unrestricted [4 cm/pig] vs. restricted feeder trough space [2 cm/pig]), and 3) period of imposing floor- and feeder-trough-space treatments (12 vs. 14 wk postweaning). Growth performance was measured from weaning (5.5 +/- 0.01 kg of BW; 17 d of age) to slaughter (the end of wk 25 postweaning). From the end of the treatment period to the end of wk 25, pigs on all treatments had the same floor and feeder trough space. Pigs with low floor space had lower (P < 0.01) ADG, ADFI, and gain:feed ratio than those with high floor space, and were therefore lighter (P < 0.05) at the end of the postweaning treatment period. Pigs given the restricted feeder trough space had lower (P < 0.05) ADFI, similar (P > 0.05) ADG, and higher (P < 0.01) gain:feed ratio than those with unrestricted feeder trough space during the treatment period. Pigs in the 14-wk treatment period had higher (P < 0.01) ADG and ADFI, but lower gain:feed than those in the 12-wk treatment during that period. In the subsequent period, from the end of treatment to wk 25, there was an interaction (P < 0.05) between floor space and treatment period; the difference in ADG and gain:feed for pigs on low vs. high floor space was greater for the 14-wk than the 12-wk treatment period. However, low-floor-space pigs tended (P = 0.06) to be lighter than high-floor-space pigs at the end of wk 25 postweaning. Neither feeder trough space nor treatment period affected pig growth performance during the period from the end of treatment to wk 25. Carcass backfat and longissimus depths at the end of wk 25 were not influenced (P > 0.05) by treatment. In summary, pigs with restricted growth due to low floor space until either 12 or 14 wk postweaning had increased growth and feed efficiency in the subsequent period to wk 25 postweaning, with only a slight effect on BW and no effect on carcass measures.     

Dinitrogen and N2O emissions in arable soils: Effect of tillage, N source and soil moisture

A laboratory investigation was performed to compare the fluxes of dinitrogen (N₂), N₂O and carbon dioxide (CO₂) from no-till (NT) and conventional till (CT) soils under the same water, mineral nitrogen and temperature status. Intact soil cores (0-10 cm) were incubated for 2 weeks at 25 °C at either 75% or 60% water-filled pore space (WFPS) with ¹⁵N-labeled fertilizers (100 mg N kg⁻¹ soil). Gas and soil samples were collected at 1-4 day intervals during the incubation period. The N₂O and CO₂ fluxes were measured by a gas chromatography (GC) system while total N₂ and N₂O losses and their ¹⁵N mole fractions in the soil mineral N pool were determined by a mass spectrometer. The daily accumulative fluxes of N₂ and N₂O were significantly affected by tillage, N source and soil moisture. We observed higher (P<0.05) fluxes of N₂+N₂O, N₂O and CO₂ from the NT soils than from the CT soils. Compared with the addition of nitrate (NO₃⁻), the addition of ammonium (NH₄⁺) enhanced the emissions of these N and C gases in the CT and NT soils, but the effect of NH₄⁺ on the N₂ and/or N₂O fluxes was evident only at 60% WFPS, indicating that nitrification and subsequent denitrification contributed largely to the gaseous N losses and N₂O emission under the lower moisture condition. Total and fertilizer-induced emissions of N₂ and/or N₂O were higher (P<0.05) at 75% WFPS than with 60% WFPS, while CO₂ fluxes were not influenced by the two moisture levels. These laboratory results indicate that there is greater potential for N₂O loss from NT soils than CT soils. Avoiding wet soil conditions (>60% WFPS) and applying a NO₃⁻ form of N fertilizer would reduce potential N₂O emissions from arable soils.     

Death from anthropogenic causes is partially compensatory in recovering wolf populations

There is substantial interest in how mortality rates affect animal populations, but mechanisms explaining when and under what circumstances particular causes of death incur demographic responses are far from clear. In theory, small or expanding populations should experience additive mortality from anthropogenic causes of death, but whether such effects are homogenous across a population or expressed only in certain high-risk individuals is open for debate. We used competing risks models to analyze mortality patterns among radio-collared wolves (Canis lupus, n = 711) from three populations in northwestern United States (1982-2004), and evaluated the degree to which anthropogenic mortality was additive vs. compensatory to natural demographic processes. Almost 80% (n = 320) of wolves dying of known fates were killed by anthropogenic causes (legal control, illegal killing, harvest in Canada, vehicle collision), and additive effects of anthropogenic mortality were most pronounced in northwestern Montana where wolf exposure to humans and livestock was high compared to either the Greater Yellowstone Area or central Idaho, where anthropogenic risk was lower. In contrast, risk from natural hazards was lower in northwestern Montana than in the other areas, implying some degree of compensatory mortality from anthropogenic risk. Animals recruited to the study following human-wolf conflict had markedly higher anthropogenic risk than those recruited for standard monitoring purposes, and juvenile wolves as well as dispersers, succumbed to higher anthropogenic risk. Multivariate models revealed that increasing wolf population density promoted higher anthropogenic risk and reduced natural risk, indicating that partially-compensatory effects of anthropogenic mortality actually became increasingly additive with population density. The observed compensatory mortality and hazard heterogeneity in our study implies that demographic responses to mortality risk may be complex and more subtle than previously thought; the density-dependent effect of anthropogenic mortality portends a stabilizing influence of humans on recovering wolf populations. We conclude that future assessment of the role of anthropogenic mortality should include individual-based hazard estimation as a complement to traditional population-level approaches.     

How important is N2O production in removing atmospherically deposited nitrogen from UK moorland catchments?

Nitrate (NO₃⁻) leaching due to anthropogenic nitrogen (N) deposition is an environmental problem in many parts of the UK uplands, associated with surface water acidification and affecting lake nutrient balances. It is often assumed that gaseous return of deposited N to the atmosphere as N₂O through denitrification may provide an important sink for N. This assumption was tested for four moorland catchments (Allt a’Mharcaidh in the Cairngorms, Afon Gwy in mid-Wales, Scoat Tarn in the English Lake District and River Etherow in the southern Pennines), covering gradients of atmospheric N deposition and surface water NO₃⁻ leaching, through a combination of field and laboratory experiments. Field measurements of N₂O fluxes from static chambers with and without additions of NH₄NO₃ solution were carried out every 4 weeks over 1 yr. Wetted soil cores from the same field plots were used in experimental laboratory incubations at 5 and 15 °C with and without additions of NH₄NO₃ solution, followed by measurement of N₂O fluxes. Field measurements showed that significant N₂O fluxes occurred in only a very small number of plots with most showing zero values for much of the year. The maximum fluxes were 0.24 kg-N/ha/yr from unamended plots at the River Etherow and 0.49 kg-N/ha/yr from plots with NH₄NO₃ additions at the Allt a’Mharcaidh. Laboratory incubation experiments demonstrated that large N₂O fluxes could be induced by warming and NH₄NO₃ additions, with the top 5 cm of soil cores responsible for the largest fluxes, reaching 11.8 kg-N/ha/yr from a podsol at Scoat Tarn. Acetylene block experiments showed that while N₂ was not likely to be a significant denitrification product in these soils, reduced N₂O fluxes indicated that nitrification was an important source of N₂O in many cases. A simple model of denitrification suggesting that 10-80% of net N inputs may be denitrified from non-agricultural soils was found to greatly over-estimate fluxes in the UK uplands. The proportion of deposition denitrified was found to be much closer to the IPCC suggested value of 1% with an upper limit of 10%. Interception of N deposition by vegetation may greatly reduce the net supply of N from this source, while soil acidification or other factors limiting carbon supply to soil microbes may prevent large denitrification fluxes even where NO₃⁻ supply is not limiting.     

Survey of the health and husbandry of small poultry flocks in Great Britain

An investigation into the health and husbandry of 15 small poultry flocks was undertaken. Each flock was visited in July and a questionnaire on management practices and disease history was completed. The flocks were clinically examined and serological tests for Salmonella pullorum, Mycoplasma gallisepticum, M synoviae, M meleagridis, Newcastle disease, infectious bursal disease, infectious bronchitis, eggdrop syndrome 76, adenoviruses and reoviruses were carried out. Oesophageal and cloacal swabs were cultured for mycoplasma and pullorum reactors were cultured. M gallisepticum, M synoviae, M meleagridis and M gallinarum infections were detected and serological reactions for all the viral diseases, except egg drop syndrome 76, were found. Evidence of Newcastle disease and pullorum disease was encountered. Lice were present in five flocks and mites in four flocks. Welfare standards varied.