A decision support framework for identifying soil constraints to the agricultural productivity of tropical upland soils

Sustainable agricultural systems are based on managing soils according to their capabilities and constraints. To facilitate the identification of constraints and appropriate management strategies for upland soils, a decision support framework ‘Soil Constraints and Management Package’ (SCAMP) has been developed. Basic soil data (both field and laboratory) are entered into an Access database and are processed to output reports that identify soil constraints to productivity and that tabulate appropriate management strategies. Where spatially referenced soil data are available, maps of constraints can be readily produced in a Geographic Information System. To demonstrate the ability of SCAMP to identify soil constraints at plot scale, it was applied to soil data sets from the two major soil types (Ferralsols and Acrisols) of Gia Lai Province, Vietnam. Phosphorus (P) fixation, aluminium toxicity and low cation exchange capacity (CEC) were identified as common constraints to productivity on Ferralsols, and low plant available water capacity, compaction and low K status as common constraints to productivity on Acrisols. Field experiments were undertaken on a Ferralsol and an Acrisol to assess management strategies for minimizing these constraints in the presence of adequate N, P and K. Maize (Zea mays) yields from the Ferralsol were increased by applying a plant amendment (Tithonia diversifolia) (selected to increase soil pH and decrease P fixation) and high activity clay (selected to increase CEC). Water‐soluble P fertiliser recovery was increased in this high P‐fixing soil by placing the fertiliser in a sub‐surface band. For the Acrisol, maize was grown in mounded rows and yields were maximized by applying a super‐absorbent material (selected to increase soil water holding capacity) or a high activity clay (selected to increase the low CEC of this soil). To demonstrate the usefulness of SCAMP on a catchment/regional scale, spatially referenced soil survey data of the Herbert River catchment, Queensland, Australia, were used to produce a map identifying areas of low pH, high acidification hazard and low CEC. These applications demonstrate the usefulness of SCAMP for linking soil data to management strategies for sustainable productivity at both plot and catchment scale.     

Differentiation of porcine dendritic cells by granulocyte-macrophage colony-stimulating factor expressed in Pichia pastoris

Dendritic cells (DC) are potent inducers of acquired immunity due to their ability to present antigens in the context of a costimulatory environment and consequently serve an essential role in vaccine efficacy. Strategies to enhance their function, such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 treatment to induce DC differentiation from peripheral blood monocytes, may therefore be useful as vaccine adjuvants. We now have evaluated the effect of recombinant GM-CSF on the differentiation of DC in swine. GM-CSF mRNA was readily detected in porcine splenocytes, with increased levels following treatment of the cells with ConA and LPS. Porcine GM-CSF was cloned and expressed in the methylotrophic yeast, Pichia pastoris, as a glycosylated protein that induced proliferation of porcine bone marrow cells. P. pastoris-derived GM-CSF induced expression of antigen presenting (MHC class II) and costimulatory (CD80-CD86) molecules and enhanced antigen presenting cell (APC) function consistent with the induction of functional DC. Thus, recombinant GM-CSF produced by P. pastoris may be a potent adjuvant for swine vaccines.     

Weeds and Shifting Cultivation

Abstract

Traditional labour-intensive methods of weed control which are normally associated with shifting cultivation are evaluated and compared with the use of herbicides and improved cultural practices. Problems occurring in shifting cultivation, such as weed seed dormancy, erosion and changing weed population; and methods of reducing the weed problem are discussed.     

Interlobular distribution of hepatic xenobiotic-metabolizing enzyme activities in cattle, goats and sheep

Microsomal and cytosolic enzymes that metabolize xenobiotics were measured in composite samples representing entire livers and in samples from three lobes, using livers of cattle, goats and sheep. Within individual species, concentrations of cytochrome P-450 and b5 and activities of NADPH cytochrome c reductase, aldrin epoxidase, aminopyrine N-demethylase, ethoxycoumarin O-deethylase, microsomal and cytosolic stilbene oxide (epoxide) hydrolase and glutathione S-transferase were not different (P greater than .05) among the various hepatic lobes. Among species, several activities differed (P less than .05), with cattle livers generally having lower values than sheep or goats.     

Taxonomic and geographic gaps in understanding the functional effects of imperilled fishes on freshwater ecosystems

The effects that fishes have on rates of one or more ecosystem processes (hereafter referred to as functional effects) are often invoked as an important reason for imperilled species conservation. However, the degree to which we understand these effects is rarely evaluated for most groups of fishes. We assessed how well the functional effects of freshwater and diadromous fishes, one of the most imperilled groups of animals, are quantified to date. We found that 88% of studies considering the functional effects of imperilled North American fishes were conducted on one family, Salmonidae. Studies of the functional effects of fishes were also concentrated in Pacific drainages of North America, with few studies in hotspots of imperilled fish diversity such as the Southeastern United States, the arid Southwest and central Mexico. Our results demonstrate the vast taxonomic and geographic gaps in our functional understanding of imperilled fishes and highlight the need to broaden this work to justify the argument that they are functionally important in the ecosystems they inhabit.     

Decomposition dynamics of plant materials in relation to nitrogen availability and biochemistry determined by NMR and wet-chemical analysis

Improved understanding of the interactive relationships of plant material decomposition kinetics to biochemical characteristics and nitrogen availability is required for terrestrial C accounting and sustainable land management. In this study, 15 typical and/or native Australian plant materials were finely ground and incubated with a sandy soil at 25 °C and 55% water holding capacity without nitrogen (−N) or with nitrogen (+N) addition (77 mg N kg⁻¹ soil as KNO₃). The C mineralisation dynamics were monitored for 356 days and the initial biochemical characteristics of the plant materials were determined by NMR and wet-chemical analyses.Under the −N treatment, C mineralisation rates of the plant materials were positively correlated with their initial N contents during the first several weeks, and then negatively correlated with lignin and polyphenols contents during the late stages of incubation. Thus the ratios of lignin/N, polyphenols/N and (lignin+polyphenols)/N had more consistent correlation with the cumulative amounts of C mineralised throughout the incubation than did any single component. In terms of the C types determined by NMR analysis, the C mineralisation rates were initially related positively to carbonyl C contents, and then negatively to aryl and O-aryl C contents from day 3 onwards.Addition of NO₃⁻-N accelerated C mineralisation during the early stages, but resulted in lower cumulative C mineralisation at the end of the incubation for most plant materials. Under the +N treatment, the decomposition rates were correlated with the contents of lignin and the sum of cellulose+acid detergent-extractable non-phenolic compounds, or with aryl, O-aryl and N-alkyl+methoxyl C contents. Regardless of the N treatment, the ratios of aryl/carbonyl, O-aryl/carbonyl and (aryl+O-aryl)/carbonyl C had the closest and most consistent correlations with the cumulative C mineralisation among all biochemical indices examined.A double exponential model with defined mineralisation rate constants for the active and slow pools was used to describe the C mineralisation dynamics. The biological meanings of the kinetically estimated active and slow pool sizes are interpreted and their relationships to the initial chemical/biochemical composition of the plant materials are explored.     

Comparative analysis of cholinesterase activities in food animals using modified Ellman and Michel assays

This study investigated correlations between modified Ellman and Michel assay methods for measuring cholinesterase (ChE) activities. It also established a foundation for the applicability of measuring ChE activities in food animal species as biochemical biomarkers for evaluating exposure to and effects of organophosphorus and carbamate pesticides. Measuring ChE activities in blood and tissue is currently the most important method of confirming the diagnosis of such exposure. The study also characterized the level of ChE activity in the selected organs/tissues of these animals and determined the best organ/tissue in which to measure ChE activity. The ChE activities were found to be higher in cattle than in sheep and higher in erythrocytes than in plasma and serum. The anticoagulant heparin significantly affects AChE activity in plasma compared with ethylenediamine tetra-acetic acid (EDTA). Of the different tissues tested, the mean of ChE activities was found to be highest in tissue from liver, followed by lung, muscle, kidney, and heart for sheep and cattle. In pigs, the ChE activities tested higher in kidney, liver, lung, muscle, and heart. The highest activities of ChE were found in pigs, followed by cattle and sheep. There was no significant difference between the modified Ellman and Michel method, but the percentage coefficient of variance (%CV) values were higher when the Michel method was used.     

Increasing Gliricidia sepium and Cassia spectabilis biomass production

This paper examines the impact of spacing on biomass production of monocropped and mixed hedgerows of seedlings and cutting of Gliricidia sepium and Cassia spectabilis. The impact of lime on G. sepium biomass production was also evaluated. Seedlings survived better than cuttings; and no differences were observed between seedlings in either pattern at the highest density tested. Although spacing reduced inter-and intra-specific competition, total biomass production was greatest at higher densities. Mixing hedgerow species reduced intraspecific competition within C. spectabilis, resulting in increased biomass production. Six, 8 and 12 tons of lime per hectare significantly increased fresh G. sepium biomass production at all harvest dates except the first. Extrapolated to an alley cropping system, applying 6 t/ha of lime increased fresh cumulative G. sepium biomass production by almost 39 t/ha over the no lime treatment representing more than 200 kg N/ha.