Factors influencing decline in soil pH in Hawaiian Eucalyptus and Albizia plantations

Soil pH declined from 5.9 to 5.0 in 8 years beneath plantations of Eucalyptus saligna (Sm.) in Hawaii. In stands of Albizia falcataria, (L.) Fosberg, the soil pH change was more dramatic, declining from 5.9 to 4.6. We measured several components of soil acidity beneath four mixtures of the two tree species to gain insight on the processes responsible for the decline in soil pH. These components were studied using an empirical method of comparing acid quantity, degree of neutralization (depletion of base cations), and acid strength. The decline in soil pH differed between species as a result of differences in the degree of neutralization of the soil exchange complex; the larger decrease in soil pH under Albizia was produced by greater acidification of the exchange complex. Empirical titration curves suggested that differences in acid strength moderated the divergence in soil pH beneath the species. Had the acids accumulating in the soil under Albizia been as strong as those in the Eucalyptus soil, the difference in soil pH would have been greater. Though the two species had contrasting effects on soil pH, the differences in degree of neutralization, responsible for the pH decline, were small compared with differences in the amount of cations stored in tree biomass. Continued supply of nutrient cations (from weathering or fertilization) will ultimately control both the extent of soil pH decline and the level of productivity sustained by the forest.     

Irrigated land retirement

Land retirement is ceasing irrigation withthe goal of reducing load, in general, ofdissolved constituents and, in particular,of trace elements, present in subsurfacedrainage generated from irrigated lands. Retirement is achieved through a process ofgoal setting, strategy development anddetermining effects, developing landselection criteria, implementation, andmonitoring. In this study, effects of landretirement are evaluated using hydrologic,soil and economic models as well as resultsfrom a field demonstration study. From themodeling and field monitoring, a process isdeveloped to meet the goals of a landretirement program in the San JoaquinValley of California.Potential negative effects listed for landretirement included loss of agriculturalproductivity, perhaps permanently, and lossof revenue to surrounding communities. Uncertainties included those associatedwith reuse of retired lands as wildlifehabitat, with retired-land maintenanceincluding dust control, with potentialpreservation of retired lands in reservefor future re-introduction to irrigated ordry-land agriculture, and withinstitutional changes concerning repaymentof federal and state water contracts. Benefits would accrue from economic returnto the landowner from the sale of property,the sale or lease of irrigation watersupply, the reduced cost of handlingdrainage, and allocation of freed-up waterto beneficial uses, and the reduced risk ofselenium exposure to fish and wildlife.A recommended sequential approach to selectand manage retired land is to identifyprimary objectives; formulate and implementarea-specific land retirement scenarios;measure biologic, hydrologic, soils andeconomic consequences in the short term andthe long term and manage and monitorretired lands based on dynamic biologic,hydrologic and soil conditions.     

Airsacculitis in turkeys exposed to Mycoplasma synoviae membranes

In studies to investigate the pathogenesis of mycoplasmal airsacculitis, exudative lesions were produced in turkeys by intra-air-sac inoculation with Mycoplasma synoviae cell membranes and viable organisms. Membrane inocula containing 5 mg of protein produced more severe lesions than inocula containing either 2.5 mg or 1 mg protein. Turkeys exposed to 5 mg of membrane protein developed moderately severe airsacculitis; those exposed to viable organisms developed markedly severe airsacculitis. Microscopic examinations revealed that membrane-induced lesions were generally similar to those resulting from infection but were less severe. At the termination of the study, 8 days after exposure, M. synoviae was isolated from respiratory tract tissues of all turkeys exposed to live organisms, but it was not isolated from any of those exposed to membranes or from unexposed control turkeys. Antibody against M. synoviae was demonstrated with the tube agglutination test in sera from turkeys exposed to membranes and those exposed to live organisms, but it was not demonstrated in sera from unexposed control turkeys.     

Hemorrhagic septicemia: naturally acquired antibodies against Pasteurella multocida types B and E in calves in the United States

Antibodies against Pasteurella multocida capsular types B and E, which cause hemorrhagic septicemia, were demonstrated in a high percentage of sera from domestic feeder calves. Since the calves had not been vaccinated with any Pasteurella organisms, the antibodies were considered to be naturally acquired. The antibodies were demonstrated by passively immunizing mice and by indirect hemagglutination and agglutination tests. Sera from 81% (44 of 54) of the calves protected mice that were challenge exposed with a capsular type B organism, and sera from 91% (49 of 54) of the calves protected mice that were challenge exposed with a capsular type E organism. Indirect hemagglutination and agglutination tests demonstrated antibody in nearly all sera. Since capsular type E organisms have been isolated only in Africa and there is only 1 report of capsular type B isolation from cattle in the United States, these organisms were not considered likely sources of the antigenic stimulation that provoked production of these antibodies.     

Selection and comparison of Mycoplasma synoviae hemagglutinating and nonhemagglutinating variants

Hemagglutinating (HA) and nonhemagglutinating (NHA) variants were selected from each of two strains of Mycoplasma synoviae, WVU-1853 and Neb-3S. The HA titers of antigens prepared by 100-fold concentration of broth cultures were 1:2560 and 1:5120 for the HA variants and less than 1:5 for the NHA variants. Adsorption of erythrocytes to colonies of the variants was directly correlated with HA activity. The HA and NHA characteristics were stable in vitro, and there was no change in HA titers after repeated transfers in broth medium. Comparisons of pathogenicity indicated differences between strains but not between variants of each strain. Air-sac lesions resulting from exposure to variants of strain Neb-3S were marked, whereas those resulting from exposure to variants of WVU-1853 were slight. The HA titers of isolates recovered from turkey air sacs exposed to the Neb-3S variants varied considerably, suggesting in vivo instability of the HA characteristic.     

Seasonal pattern of nitrogen mineralization and soil moisture beneath Faidherbia albida (synAcacia albida) in central malawi

On fertile alluvial soils on the lakeshore plain of Malawi, maize (Zea mays L.) yields beneath canopies of large Faidherbia albida (synAcacia albida) trees greatly exceed those found beyound tree canopies, yet there is little difference in soil nutrients or organic matter. To investigate the possibility that soil nutrient dynamics contribute to increased maize yields, this study focused on the impact of Faidherbia albida on nitrogen mineralization and soil moisture from the time of crop planting until harvest. Both large and small trees were studied to consider whether tree effects change as trees mature.During the first month of the rainy season, a seven-fold difference in net N mineralization was recorded beneath large tree canopies compared to rates measured in open sites. The initial pulse beneath the trees was 60 g N g^–1 in the top 15 cm of soil. During the rest of the cropping cycle, N availability was 1.5 to 3 times higher beneath tree canopies than in open sites. The total production of N for the 4-month study period was 112 g N g^–1 below tree canopies compared to 42 g N g^–1 beyond the canopies. Soil moisture in the 0–15 cm soil layer was higher under the influence of the tree canopies. The canopy versus open site difference grew from 4% at the beginning of the season to 50% at the end of the cropping season.Both N mineralization and soil moisture were decreased below young trees. Hence, the impact of F. albida on these soil properties changes with tree age and size. While maize yields were not depressed beneath young F. albida, it is important to realize that the full benefits of this traditional agroforestry system may require decades to develop.     

Effect of dietary energy source on in vitro substrate utilization and insulin sensitivity of muscle and adipose tissues of Angus and Wagyu steers

Angus (n = 8; 210 kg of BW) and 7/8 Wagyu (n = 8; 174 kg of BW) steers were used to evaluate the effects of dietary energy source on muscle and adipose tissue metabolism and insulin sensitivity. Steers were assigned to either a grain-based (corn) or hay-based (hay) diet and fed to similar final BW. At slaughter, LM and s.c. and i.m. adipose tissue samples were collected. Portions of the LM and adipose tissues were placed immediately in liquid N for later measurement of glycolytic intermediates. Fresh LM and s.c. and i.m. adipose tissues were incubated with [U-(14)C]glucose to assess glucose metabolism in vitro. All in vitro measures were in the presence of 0 or 500 ng/mL of insulin. Also, s.c. and i.m. adipose tissues were incubated with [1-(14)C]acetate to quantify lipid synthesis in vitro. Glucose-6-phosphate and fructose-6-phosphate concentrations were 12.6- and 2.4-fold greater in muscle than in s.c. and i.m. adipose tissues, respectively. Diet did not affect acetate incorporation into fatty acids (P = 0.86). Insulin did not increase conversion of glucose to CO(2), lactate, or total lipid in steers fed hay but caused an increase (per cell) of 97 to 110% in glucose conversion to CO(2), 46 to 54% in glucose conversion to lactate, and 65 to 160% in glucose conversion to total lipid content in adipose tissue from steers fed corn. On a per-cell basis, s.c. adipose tissue had 37% greater glucose oxidation than i.m. adipose (P = 0.04) and 290% greater acetate incorporation into fatty acids than i.m. adipose (P = 0.04). Insulin addition to s.c. adipose tissue from corn-fed steers failed to stimulate glucose incorporation into fatty acids, but exposing i.m. adipose tissue from corn-fed steers to insulin resulted in a 165% increase in glucose incorporation into fatty acids. These results suggest that feeding hay limited both glucose supply and tissue capacity to increase glucose utilization in response to insulin without altering acetate conversion to fatty acids. Because s.c. adipose tissue consistently utilized more acetate and oxidized more glucose than did i.m. adipose, these results suggest that hay-based diets may alter i.m. adipose tissue metabolism with less effect on s.c. adipose tissue.