Influence of phosphate sorption on dispersion of a Ferralsol

Abstract

Soil dispersion induces soil erosion and colloidal leaching. Nutrients are lost at the same time and this causes water contamination. Phosphate is an essential element for living organisms. Because phosphate influences soil dispersion and it is an important limited resource, this influence must be evaluated well in order to diminish negative effects on soil structure. In this paper, we firstly evaluated the influence of phosphate sorption on soil dispersion by calculating repulsive potential energy between soil particles. Ferralsol, which is a typical soil in rainy tropical regions, was used as the material. The dispersion-flocculation phenomena were investigated with absorbance of soil suspension under different pH, phosphate adsorption and electrolyte concentration in an Na-NO₃-PO₄ system. The repulsive potential energy was calculated based on the diffuse double layer theory and the measured zeta potential. We indicated that the measured absorbance increased with the increase of the repulsive potential energy. The repulsive potential energy increased with increasing phosphate sorption up to about 5 to 20 mmol kg^?1 at all pH, and it induced the soil dispersion, because phosphate sorption increased the negative charge of the soil. After its peak, it decreased with increasing phosphate sorption because the electrolyte concentration increased and the electrolyte screened the electric field near the soil surface. The repulsive potential energy also increased with increasing pH because of the increase of the negative charge of the soil. Even at low pH, after a certain amount of phosphate sorption, the soil dispersed due to the increase of repulsive potential energy, although the soil flocculated before phosphate application. Because the soil dispersion causes soil and phosphorus loss, the influence of soil pH and phosphate sorption on the soil dispersion should be considered for good soil management.     

Bacteriological studies on the mineralization of soil organic nitrogen in paddy soils

Anaerobes were isolated from both disrupted and undisrupted soil samples incubated under submerged condition. All isolates were divided into 9 groups based on their gram stain and morphological characteristics. Correlation coefficients between the amount of nitrogen mineralized and the number of each group were calculated. A significant correlation was observed only between the amount of nitrogen mineralized and the number of gram positive-rod shaped anaerobic microorganisms (r=0.768 at P=0.05). This result indicates that in this study system, sorne particular anaerobes may play an important role in the mineralization of soil organic nitrogen.     

Bacteriological studies on the mineralization of organic nitrogen in paddy soils

In this report we studied the effects of mechanical grinding of paddy soils on nitrogen mineralization and bacterial number when soils were incubated under a submerged condition after grinding.

Nitrogen mineralization was increased by grinding soil samples as compared with those without grinding. The value of (Nd-Nu)/Nu, where Nd is the amount of ammonia-nitrogen formed by incubation of disrupted samples and Nu those of the undisrupted soils, was in good correlation with clay/humus ratio.

Although significant difference was not observed between the number of aerobic bacteria with undisrupted and disrupted soil samples, higher anaerobic bacterial numbers were found with disrupted than with undisrupted ones.

A significant correlation was also obtained between the amounts of nitrogen mineralization increased by the grinding of soil and the numbers of anaerobic bacteria.     

Effects of topography and planted trees on the distribution of naturally regenerated broad-leaved trees in a 140-year-old <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> plantation in northern Kyushu,Japan

We investigated factors affecting the distribution of naturally regenerated broad-leaved trees in a 140-year-old Cryptomeria japonica plantation. We used path analysis to examine the relationship among microtopography, the biomass of planted trees, and the biomasses of canopy and subcanopy trees of broad-leaved species. The study plot was divided into three topographic types (ridge, slope, and valley), and we discuss how the different topographic types are affected. For all topographic types, the biomass of canopy trees of broad-leaved species decreased with convexity. For slope and valley topographies, the biomass of subcanopy trees of broad-leaved species also decreased with convexity. For ridge topography, the biomass of subcanopy trees of broad-leaved species increased with the biomass of planted trees, and decreased with the biomass of canopy trees of broad-leaved species. These results suggest the effects of microtopography on the biomass of subcanopy trees were much larger than the effects of canopy trees for slope and valley topographies, while the effects of microtopography were smaller for ridge topography.     

Contribution of a liana species, <Emphasis Type="Italic">Mucuna macrocarpa</Emphasis> Wall., to litterfall production and nitrogen input in a subtropical evergreen broad-leaved forest

Annual amounts of litterfall and nitrogen input by litterfall were measured in a subtropical evergreen broad-leaved forest to examine the contribution of a liana species, Mucuna macrocarpa Wall., to the spatial heterogeneity of litterfall production and nitrogen input. The total litterfall in the study plot was 7.1 t ha⁻¹ year⁻¹. The amount of litterfall varied with topography and was greatest at the valley bottom and decreased toward the ridges. Macuna macrocarpa litterfall was absent on the ridges although it accounted for the largest percentage, 32%, of total leaf litter production in the valley. Nitrogen input by litterfall was 69 kg ha⁻¹ year⁻¹ in the plot. Nitrogen input by litterfall was also largest at the valley bottom and decreased toward the ridges. Leaf litter of M. macrocarpa had approximately twice the nitrogen concentration of litterfall of other species. Macuna macrocarpa accounted for 42% of nitrogen input by leaf litter in the valley. The abundance and the high nitrogen concentration of M. macrocarpa intensified differences in the amount of litterfall and nitrogen input by litterfall between valleys and ridges. It was concluded that a liana species, M. macrocarpa, can contribute to the spatial heterogeneity of litterfall and may subsequently affect nutrient cycling in a subtropical evergreen broad-leaved forest on Okinawa Island.     

Physiological characteristics of blue sac disease in chum salmon alevins

Fisheries Science - Blue sac disease (BSD) in salmonids results in the abnormal accumulation of ascites fluid and can often lead to mass mortality. However, the symptoms and causes of BSD remain...     

Inhibition by pulp juice and enhancement by ingestion on germination of bird-dispersedPrunus seeds

To evaluate what prevents seed germination and why ingestion by birds enhances germination, we carried out germination experiments using bird-dispersed seeds of twoPrunus species (Prunus sargentii andP. ssiori) in the laboratory. Germination of seeds with following four treatments was compared: “Ingested seeds” excreted after feeding of fruits to birds; “Extracted seeds” deliberately extracted from the fruit pulp; “Juiced seeds” which were supplemented with the juice of the pulp after seeds had been deliberately extracted from the pulp; and “Intact seeds” in untreated whole fruits. Many ingested (27%, 23% inP. sargentii, 18% inP. ssiori) and extracted seeds (24% inP. sargentii, 17% inP. ssiori) germinated, and difference in germination percentages between ingested and extracted seeds were not significant, for eitherPrunus species. The Juiced seeds rarely germinated (2% inP. sargentii, 6% inP. ssiori), and seeds within intact fruits did not germinate. These results suggest that the fruit pulp and the juice of the pulp inhibit germination and the seeds could germinate without ingestion by birds once they had been manually extracted from pulp. Therefore, it is considered that bird ingestion enahnces germination by removing pulp, especially juice of the pulp, in these twoPrunus species.     

Evaluation of nutritive value and palatability by goats and sheep of selected browse foliages from semiarid area of Kenya

The feeding value of five browse foliages (Acacia brevispica, Acacia mellifera, Berchemia discolor, Zizyphus mucronata and Maerua angolensis) grown in semiarid area of Kenya were evaluated. Their chemical composition including polyphenolics and in vitro gas production characteristics were determined. The biological activity of the polyphenolics was assessed as the increases in gas production profiles and in vitro true dry matter (DM) and organic matter (OM) digestibility after in vitro incubation with or without addition of polyethylene glycol (PEG) as a tannin binding reagent. The intake and palatability ranking of the browse foliages by goats and sheep were also investigated. The browse foliages had variable crude protein content (149.5–248.6 g/kg DM) and variable content of neutral detergent fiber (205.1–424.0 g/kg DM). The content of total extractable tannins was generally low (2.4–34.8 g/kg DM). At 24 h of incubation, Z. mucronata produced the highest gas volume, while after 48 h of incubation, B. discolor produced the highest gas volume. M. angolensis had the least gas production potential within the browse foliages. Addition of PEG increased gas production except in A. mellifera and M. angolensis. However, PEG addition did not have any significant effect on in vitro true DM and OM digestibility except in B. discolor, which decreased. The rank order of preference (highest to least) for goats was A. brevispica, Z. mucronata, B. discolor, A. mellifera and M. angolensis while the rank order of preference for sheep was A. brevispica, B. discolor, A. mellifera, Z. mucronata and M. angolensis. The goats had higher intakes of all the browse foliages than sheep. The result of this study highlights the higher feeding value of the browse species as supplemental feed with low quality basal diet with both of animal species except M. angolensis.     

Treatment with a High Dose Combination of PMSG/hCG Preparation of Mares Clinically Diagnosed with Ovarian Quiescence during the Breeding Season (Investigation from 1975 to 2000)

A total of 88 thoroughbred mares were diagnosed with clinical ovarian quiescence and subjected to four treatment regimens. Using PMSG, hCG or combinations of both. A high dose combination of 5,000IU PMSG with 5,000IU hCG showed significantly higher rates of marked estrus and ovulation induction (P<0.01) as well as conception rates (P<0.05). In the present study, the administration of a high-dose combination of PMSG with hCG was shown to be an effective treatment of ovarian quiescence in light mares.