Factors controlling carbon dioxide and methane production in acid sulfate soils

Methane and C02 production in flooded acid sulfate soils of Thailand were governed primarily by soil oxidation-reduction potential (Eh) and pH. The critical Eh and pH levels at which CH₄ emission began was Eh-150 mV, and pH 6.1. Low soil pH limited soil reduction and subsequently CH₄ production. Soil respiration (C02 production) was influenced by Eh-pH levels and organic matter content. Soils with higher C02 production rates produced greater amounts of CH₄. Soil pH, however, was the dominant variable which influenced organic matter decomposition, low soil Eh conditions and subsequent CH₄ and CO₂ production. Curvilinear or log transformations of pH, Eh and organic matter content (OM) were used in explaining variables controlling CH₄ and CO₂ production; CH₄ = ?2.359 ? 0.0001 Eh + 2.047 pH ? 3.019 (In pH)² CO₂ = ?5210 ? 1.6 Eh + 3144 (In pH) + 1011 (In OM).     

Nitrification and Denitrification Estimates in a Louisiana Swamp Forest Soil as Assessed by 15N Isotope Dilution and Direct Gaseous Measurements

The transformations of applied (100 kg N ha^-1)¹⁵ N labelled NO₃ and NH₄ in Mississippi River deltaic plain swamp forest soil which receives agriculture run-off from adjacent sugarcane fields were determined. Using an isotopic dilution technique, the rates of NO³ production (nitrification) and reduction in the ¹⁵NO₃ treated soil-water-columns were approximately 240 and 2,320 g N ha^-1 d^-1, whereas NH₄ production (mineralization) and removal rates in the ¹⁵NH₄ treated soil-water-columns were 270 and 2160 g N ha^-1 d^-1, respectively. It was shown that if nitrification and NH₄ assimilation were the primary processes responsible for NH₄ removal, average NH₄ assimilation would be 145 g N ha-1 d^-1. Based on labelled N₂-emission, denitrification was 3 fold greater in the NO₃ treatment compared to the NH₄ treated soil water-columns with rates of 818 and 266 g N ha^-1 d^-1 respectively. Even though the rate was lower in the NH₄ treatment, results show that nitrification-denitrification of NH₄ is a significant process. Nitrogen losses determined by¹⁵ N₂ emissions were 20.4 and 6.4% and N₂O emissions were 0.10 and 0.03% of the applied NO₃-N and NH₄-N, respectively, over 32 days of incubation. Fertilizer loss through N₂O emission was only of minor significance compared to the fertilizer loss through N₂ evolution. Nitrous oxide fluxes from the control soil-water-columns averaged 9.4 g N ha^-1 d^-1. Addition of NO₃-N to the columns increased N₂O production 56% as compared to a 15% increase from the NH₄-N addition. Results show that this wetland soil has a large capacity to process inorganic nitrogen entering the system as a result of agriculture run-off.     

Assessing the effect of resistant-susceptible associations and determining thresholds for associations in suppressing leaf and neck blast of rice

Blast has become a major problem in the upland rice of Indonesia, as the improved resistant varieties with high yield performances released in the 90's became susceptible only a few years after their release. The present study investigated the efficiency of association of susceptible and resistant varieties in reducing leaf and neck blast and increasing yield. Two sets of experiments were conducted in fields with associations through using different proportions of resistant variety, and two types of susceptible variety (moderately and very susceptible) in the association. The efficiency of the association was measured by comparing disease intensity and yield in the variety when grown in association and when grown as a pure stand. ANOVAs and logistic regressions indicated that resistant-susceptible variety association was more efficient in reducing neck blast than leaf blast. Associations were more efficient (1) when the proportion of resistant variety was increased, (2) when a moderately susceptible variety was used instead of a very susceptible variety, and (3) when disease level in the pure stand was higher. Associations did not penalize the performances of the resistant variety, neither in terms of disease intensity, nor yield. Logistic regressions allowed to estimate the probability of a given association to reduce disease (or to increase yield) above a preset threshold, according to the proportion of resistant variety and to the type of susceptible variety.     

Effect of Dietary Estradiol‐17β on the Feminization of Silver Perch,Bidyanus bidyanus (Mitchell, 1838)

The silver perch, Bidyanus bidyanus (Mitchell 1838), displays sexual dimorphism in size, with females reaching larger maximum size than males. In an attempt to produce all‐female populations, larvae at 30 d posthatching were fed an estradiol‐17β (E2) diet at dosages of 0, 60, and 120 mg/kg for 30 d. Histological examination of gonads revealed that all E2‐supplemented diets resulted in significantly higher (P < 0.05) feminization rates (97.22–100%) than did the control (39.69%) but with no difference between the two E2 diets (P > 0.05). Female and male gonads were observed in fish fed the 60 mg E2/kg diet. No significant differences were observed in the survival rate, weight gain, gonad weight and length, specific growth rate (SGR), or gonadosomatic indexes, except for gonad length and SGR at the end of the experiment. Although the ovary length of fish fed the 60 mg E2/kg diet was significantly shorter than that of the control groups, no abnormalities were detected. In contrast, fish fed 120 mg E2/kg grew faster than the other fish and showed sexual dimorphism. Our results suggest that supplementation of E2 at 60–120 mg/kg diet could be applied to establish all‐female populations of silver perch.     

Characterization of major,unused, and unvalued Indonesian wood species I. Dependencies of mechanical properties in transverse direction on the changes of moisture content and/or temperature

Mechanical property changes due to the moisture content (MC) and/or temperature changes were examined for 15 Indonesian wood species. A static bending test was carried out at 20°C, 65% relative humidity (air-dry), and water-saturated at 20°C (wet-20) and 80°C (wet-80). For individual test conditions, modulus of elasticity (MOE) and modulus of rupture (MOR) increased linearly with specific gravity regardless of wood species; however, maximum deflection did not correlate with specific gravity for any MC or temperature conditions. The relative values of MOE and MOR measured in wet-20 to air-dry conditions were variously affected from slightly to strongly depending on the wood species. However, the relative values always decreased markedly when saturated in water at 80°C, regardless of wood species. The relative MOE, MOR, and maximum deflection values due to the change in MC or MC and temperature combined were independent of specific gravity but may be dependent on wood type: softwood or hardwood.     

Carotenoid content, physicochemical, and sensory qualities of deep-fried carrot chips as affected by dehydration/rehydration, antioxidant, and fermentation.

Carrot slices were subjected to one of the following experiments prior to deep-frying: (A) dehydration/rehydration, (B) soaking in different antioxidants, and (C) fermentation with/without blanching. There were no significant differences (P > or = 0.05) in carotenoid contents among carrot chips treated with/without dehydration. Soaking in sodium metabisulfite resulted in the highest carotenoid content and lightness (L), redness (a), and yellowness (b) values among the antioxidant treatments. Fermentation without blanching significantly decreased (P < 0.05) carotenoid content, vitamin A activity, and fat content. Dehydration and fermentation with blanching significantly increased (P < 0.05) the lightness (L), redness (a), and yellowness (b) values of the chips. Dehydration/rehydration, but not antioxidant and fermentation, significantly decreased (P < 0.05) the water activity of the chips. The textural values of carrot chips prepared using sodium metabisulfite, without dehydration and without fermentation, were the lowest among other treatments which suggests the crispiest. Carrot chips prepared using sodium metabisulfite, without dehydration and without fermentation, had the highest carotenoid content and retention, and the highest overall acceptability score.     

Liquid penetration of precompressed wood VII: combined treatment of precompression and extraction in hot water on the liquid penetration of wood

The object of this study was to determine the cause of differences in the improvement in liquid penetration of precompressed wood species. The maximum amount of water uptake by the capillary rise method and changes in the aspirated pits seen with scanning electron microscopy before and after of preextraction and precompression were investigated using heartwood samples of four softwoods. The height of penetration and the weight by the capillary rise method for preextractive wood powders are discussed. Three wood species andLarix leptolepis showed marked increases in the amount of solution uptake after precompressed treatment only.Larix leptolepis wood required compression after extraction by boiling in water. These differences among wood species were caused by the accumulation of extractive material. It was also recognized that the accumulative material inLarix wood has plasticity and that inPseudotsuga is brittle. Based on these results it was found that it is difficult to destroy aspirated pits in the former and easy in the latter. On the other hand, the difference in penetration of each wood species was caused by the quantity and quality of the extraction material in addition to the extent of the wettability of the surface of the cell cavity as well as aspirated pit.Part of this report was presented at the 46th annual meeting of the Japan Wood Research Society, Kumamoto, April 1996     

Yolk utilization and growth during the early larval life of the Silver Perch,Bidyanus bidyanus (Mitchell, 1838)

The aim of this research was to investigate the yolk sac and oil globule utilization by silver perch (Bidyanus bidyanus) larvae produced from domesticated broodfish. The larvae were kept unfed in the holding tank, sampled, and investigated by image analysis software to determine various characteristics, such as the diameters of ova, water-hardened eggs, yolk-sac, oil globules, and the total length of larvae. The research illustrated that, with the exception of oil globule diameter, all other morphometric parameters were significantly lower (P < 0.05) when compared to the larvae from the wild broodfish. The yolk sac was completely absorbed at 96 h post-hatching (hph) and the oil globule was visible until 240 hph. The larvae exhibited predatory movements and tried to catch rotifer at 4 days post hatching (dph). However, the onset of feeding took place at 5 dph, while 100% of feeding occurred at 6 dph. During the first 96 h (h), larvae grew significantly faster than the next 144 h. Larvae encountered low mortalities (<10%) during the first 96 hph, before increasing significantly in the next 24 h and no unfed larvae survived post 240 h. The results also suggested that the exogenous feed should be available at 96 hph, which is well after the yolk sac is completely depleted. In addition, although most of eggs and larval performance from domesticated broodfish were inferior compared to the wild one, it has larger oil globule that could make longer of its mixed feeding period and therefore could have better in viability.