Yoshihiro Tokashiki

Sewage sludge sugarcane trash based compost and synthetic aggregates as peat substitutes in containerized media for crop production

Effect of partial substitution of peat in growth media by sewage sludge sugarcane trash based compost (SSC) and synthetic aggregates (SA) on the physical and chemical characteristics of the growth media and on the growth and nutrition of lettuce (Lactuca sativa L.) grown in the substituted media was investigated under this study. SSC was produced from sugarcane trash and sewage sludge. Unconventional SA were produced by low productive acidic red soil with paper waste and starch waste. The treatments assayed were: SSC (40%)+Peat (60%), SA (40%)+Peat (60%), SSC (60%)+SA (40%), SSC (40%)+SA (20%)+Peat (40%) and SSC (40%)+SA (40%)+Peat (20%). Peat only was used as the control. The physical and chemical properties of all growing media were analyzed. SSC-SA based substrates showed adequate physical and chemical properties compared to peat for their use as growing media in horticulture. In relation to the plant growth in peat control, plants grown in the SSC-SA based substrates reached better growth and nutrition. The concentration of trace elements in plant tissues was far lower than the ranges considered phytotoxic for plants. Utilization of SSC and SA can be considered as an alternative media component to substitute the widely using expensive peat in horticulture.

Leaf litter decomposition and nutrient dynamics in a subtropical forest after typhoon disturbance

Decomposition of typhoon-generated and normal leaf litter and their release patterns for eight nutrient elements were investigated over 3 yr using the litterbag technique in a subtropical evergreen broad-leaved forest on Okinawa Island, Japan. Two common tree species, Castanopsis sieboldii and Schima wallichii, representative of the vegetation and differing in their foliar traits, were selected. The elements analyzed were N, P, K, Ca, Mg, Na, Al, Fe and Mn. Dry mass loss at the end of study varied in the order: typhoon green leaves > typhoon yellow leaves > normal leaves falling for both species. For the same litter type, Schima decomposed faster than Castanopsis. Dry mass remaining after 2 yr of decomposition was positively correlated with initial C:N and C:P ratios. There was a wide range in patterns of nutrient concentration, from a net accumulation to a rapid loss in decomposition. Leaf litter generated by typhoons decomposed more rapidly than did the normal litter, with rapid losses for N and P. Analysis of initial quality for the different litter types showed that the C:P ratios were extremely high (range 896 − 2467) but the P:N ratios were < 0.05 (range 0.02 − 0.04), indicating a likely P-limitation for this forest. On average 32% less N and 60% less P was retranslocated from the typhoon-generated green leaves than from the normal litter for the two species, Castanopsis and Schima. An estimated 2.13 g m–2 yr–1 more N and 0.07 g m–2 yr–1 more P was transferred to the soil as result of typhoon disturbances, which were as high as 52% of N and 74% of P inputted from leaf litter annually in a normal year. Typhoon-driven maintenance of rapid P cycling appears to be an important mechanism by which growth of this Okinawan subtropical forest is maintained.

Ecological studies on subtropical evergreen broad-leaved forest in Okinawa, Japan: Litter production and nutrient input

Patterns of litterfall and nutrient input in a subtropical evergreen broad-leaved forest in northern Okinawa, Japan, were studied during May, 1996–April, 1999. The mean annual rate of litterfall in the five sampling plots ranged from 6.84 to 8.93 Mg ha−1 yr−1, of which 63.3–68.5% were leaves; 22.4–29.1% woody parts (including branches < 5.0 cm in diameter and bark); 2.8–5.0% sexual organs and 4.6–6.3% miscellaneous material. Significant differences were found among plots and among years. Significantly monthly differences pronounced seasonal patterns in litterfall were observed. Total litterfall and leaf litter showed negative correlations with relative basal area of the dominant species,Castanopsis sieboldii; and showed positive correlations with mean height of the stands. The dominant species,C. sieboldii produced an average of 2.36 Mg ha−1 yr−1 of leaf litter, which covered 30.5% of the annual litter production, and the nutrient input from those litterfall contributed 32.3, 28.3, 30.2, 22.2, 32.5, and 30.5% of total N, P, K, Ca, Mg, and Na, respectively. Nutrient use efficiency in litter production was high, especially for P and K compared with other broad-leaved forests in Japan indicating that P and K may be limiting in Okinawan evergreen broad-leaved forest.

Structure and Species Diversity of Subtropical Evergreen Broad-leaved Forest in Northern Okinawa Island, Japan

The structure and tree species diversity of a subtropical evergreen broad-leaved forest in northern Okinawa Island, Japan, were studied. Enumeration of the six sampling plots revealed an average density of 5,580 individuals with DBH≧3.0 cm/ha, having an average basal area of 55 m2. The large-size trees of DBH≧20 cm contributed 10% of the total individuals, and 49% of the total basal area. The forest showed a high diversity of tree species, which is comparable to some tropical rain forests. A total of 54 over-story species of 24 families and a total of 63 understory species of 26 families were identified in the six sampling plots. Fagaceae and Theaceae were the most important families;Castanopsis sieboldii, Schima wallichii andDistylium racemosum were the most important species. The diversity index and equitability index of species were 4.15 and 0.72 for the overstory plots, and 4.72 and 0.79 for the understory subplots, respectively. The diversity index for the overstory was significantly correlated to the total basal area of trees over 20 cm DBH (p<0.05) and the importance value ofC. sieboldii (p<0.001), while for understory, the diversity index was not correlated to the structural parameters (allp>0.16). The size distribution pattern and age structure indicated differences in regeneration strategies for canopy dominants. In population dynamics of the succession process,C. sieboldii andD. racemosum were self-maintaining types, andS. wallichii was a gap- or opening-dependent type.

Characteristics of synthetic soil aggregates produced by mixing acidic “Kunigami Mahji” soil with coal fly ash and their utilization as a medium for crop growth

Abstract This study was carried out to examine the characteristics and potential utilization of synthetic soil aggregates (SSA) produced by mixing acidic “Kunigami Mahji” soil in Okinawa, Japan, with waste materials, such as coal fly ash, used paper and starch, as media for crop growth. A series of different SSA were produced by incorporating various percentages (i.e. 0, 20, 40, 60, 80 and 100%) of coal fly ash into the “Kunigami Mahji” soil with used paper and starch. The particle density and bulk density of the original “Kunigami Mahji” soil were 2.67 and 1.23 g cm−3, respectively. The increased percentages of added coal fly ash, used paper and starch significantly decreased the particle and bulk densities of SSA compared with the original “Kunigami Mahji” soil because of the low particle and bulk densities of the coal fly ash (2.10 and 0.96 g cm−3, respectively). The SSA particle density varied between 2.39 and 2.14 g cm−3, and bulk density varied between 0.72 and 0.81 g cm−3, depending on the additional percentages of coal ash from 20–100%. Maximum water-holding capacity and saturated hydraulic conductivity were increased with the formation of SSA with coal fly ash, used paper and starch binder compared with the original “Kunigami Mahji” soil. The saturated hydraulic conductivity values of the SSA increased because of their low bulk density compared with the original soil. The addition of coal fly ash, used paper and starch to the acidic (pH = 4.62) “Kunigami Mahji” soil to form SSA increased the pH (6.70–9.96), electrical conductivity, exchangeable cation concentration and cation exchange capacity. The addition of coal fly ash up to 60% increased the aggregate strength. The growth and yield of komatsuna and soybean crops with SSA as a crop growth medium was assessed. Both crops showed the highest growth and yield when grown with SSA containing 20% of coal fly ash. Synthetic soil aggregates containing more than 20% of coal fly ash reduced plant growth and yield. Therefore, SSA produced from “Kunigami Mahji” soil with 20% of coal fly ash, used paper and starch can be successfully used as a medium for crop growth.

Use of synthetic soil aggregates as a containerized growth medium component to substitute peat in the ornamental plant production

This study investigates characteristics and utilization of synthetic soil aggregates (SA) formed by low productive acidic soil with paper and starch waste for production of French marigold (Tagetes patula) as a partial peat substitution in growing substrate. Five different growth substrates utilized in this study were: (i) Peat only, (ii) peat 75%: SA 25%, (iii) peat 50%: SA 50%, (iv) peat 25%: SA 75%, and (v) SA only. Peat 75%: SA 25% enhanced substrate physical and chemical properties into the established ideal substrate range. Plant height, numbers of flowers, fresh shoot weight, dry shoot weight, root length, fresh root weight and dry root weight of French marigold grown in the substrate of peat 75%: SA 25% increased by 13.28, 23.07, 28.51, 27.41, 6.66, 68.33 and 7.40%, respectively, compared with peat substrate. Peat 50%: SA50% gave similar growth parameters to peat only substrate. Nitrogen (N) content of plants grown in peat 75%: SA25% was higher than peat substrate. Cu, Fe, Mn and Zn concentrations in all plant shoots were in the normal range and well below the phytotoxic range. Therefore, growth substrates with 25% and 50% SA can be recommended as the most effective substrates to substitute expensive and less available peat from an environmental point of view.

Mineralogical characteristics and micromorphological observations of brittle/soft Fe/Mn concretions from Okinawan soils

Manganese minerals are not common and the distinction of poorly crystalline Mn minerals from other associated minerals is important. For many years, the crystal structures of poorly crystalline Mn minerals in Fe/Mn concretions have been the subject of considerable conjecture and controversy. This study reports the micromorphological and mineralogical characteristics, and the chemical composition of Fe/Mn minerals in soft Fe/Mn concretions formed in Shimajiri Mahji soils (Typic Hapludalfs) that developed from Ryukyu limestone on Okinawa Island, Japan. The Fe/Mn minerals in brittle/soft Fe/Mn concretions were characterized using a sequential selective dissolution procedure (SSDP) by treatments with NaOH, hydroxylamine hydrochloride (HAHC) at 25°C and 60°C, and dithionite-citrate-bicarbonate (DCB) in combination with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The HAHC treatment at 25°C dissolved birnessite, but not lithiophorite and goethite. A subsequent extraction with HAHC at 60°C dissolved lithiophorite but not goethite. Finally, the DCB treatment was able to dissolve goethite. The SEM images show that birnessite crystals, with a blade- or plate-like habit, form globular aggregates inside veins and cavities. Pseudo-hexagonal crystals of lithiophorite have produced thread-ball structures with crystal shape similar to birnessite and birnessite crystals are closely associated with lithiophorite. Well developed hexagonal plates of gibbsite crystals are clustered in different directions to make foliated vermiform structures. Aggregates of goethite crystals are acicular and are arranged into stars. The supplementary SSDP, in combination with XRD and SEM techniques, provides methods to distinguish and partly quantify birnessite and lithiophorite in the presence of layer silicate and Fe oxide minerals and confirm their own morphological features.

Effect of Synthetic Soil Aggregates as a Soil Ameliorant to Enhance Properties of Problematic Gray (“Jahgaru”) Soils in Okinawa, Japan

Synthetic aggregates (SA) were developed using low productive red soil, paper, and starch waste and then utilized as a soil ameliorant to improve poor physical and chemical properties of a gray soil (“Jahgaru”). The gray soil was amended with SA at 10, 20, 30, 40, and 50% and then used for the cultivation of French marigold (Tagetes patula). The SA addition enhanced bulk density, porosity, water‐holding capacity, hydraulic conductivity, pH, organic matter, and carbon (C) content of original gray soil. Plant height, number of flowers per plant, shoot fresh weight, shoot dry weight, root length, root fresh weight, and root dry weight in 30% of SA addition were the greatest and were increased by 1.5, 2.9, 3.5, 4.7, 3.4, 4.3, and 9 times, respectively, compared to gray soil. It can be concluded that developed SA can be utilized as a soil ameliorant to improve poor physical and chemical properties of gray soil.

Pattern and chemical composition of fine litterfall in a subtropical forest in northern Okinawa Island, Japan

Abstract The aim of this work was to analyze the pattern and chemical composition of litterfall and to investigate relationships between the contents of nutrient elements in senescent and fresh mature leaves of two dominant species: Castanopsis sieboldii and Schima wallichii , in two forest sites differing in edaphic condition on the northern Okinawa Island, Japan. In this subtropical forest, the mean annual rates of litterfall (including premature litter generated by windstorm) were 684 and 737 g m −2 yr −1 at site A and B, respectively. The leaf litter contributed 67% of annual total litterfall. The peak leaf fall occurred in March. Woody litter showed no particular pattern, and its peak fall varied with windstorm. The mean annual nutrient inputs by fine litterfall were, respectively, N 80.1, P 3.2, K 25.8, Ca 58.6 and Mg 17.1 kg ha −2 yr −1 at site A; and N 80.6, P 2.9, K 20.7, Ca 65.9 and Mg 17.8kg ha −2 yr −1 at site B. A marked seasonal variability was observed in the concentrations of N, P and K, with no important differences for Ca and Mg, in leaf litter for the two dominants. N, P and K were retranslocated to other tree organs and Ca, Mg, Mn and Al were accumulated in mature leaves. The comparison between leaf litter and fresh mature leaves suggests that the analysis of leaf litter cannot substitute for that of living leaves to evaluate the nutritional status of the species studied for essential elements N, P and K. However, the index of nutrient use efficiency in litterfall can be used as an indicator of soil nutrient conditions. We found site-dependent and between-species differences in nutrient content and nutrient remobilization. The nutrient cycling in this subtropical forest follows a pattern similar to tropical forests, with inefficient within-stand use of N and more efficient cycling of P. Es war Ziel dieser Arbeit das Muster und die chemische Zusammensetzung der Blattstreu zu analysieren, sowie die Beziehungen zwischen den Nahrstoffinhalten in seneszenten und frischen, voll entwickelten Blattern von zwei dominanten Arten zu untersuchen: Castanopsis sieboldii und Schima wallichii in zwei Waldarealen der nordlichen Okinawa Insel, Japan, die sich in den edaphischen Bedingungen unterschieden. In dem subtropischen Wald betrugen die jahrlichen Streufallraten 684 g m −2 a −2 auf der Flache A und 737 g m −2 a −2 auf der Flache B. Die Blattstreu stellte einen Anteil von 67% des gesamten jahrlichen Streufalls. Das Maximum des Blattfalls fand im Marz statt. Die verholzte Streu folgte keinem bestimmten Muster und ihr maximaler Fall variierte mit dem Wind. Der mittlere jahrliche Nahrstoffeintrag durch feine Streu betrug fur N 80.1, P 3.2, K 25.8, Ca 58.6 und Mg 17,1 kg ha −2 a −1 auf der Flache A und fur N 80.6, P 2.9, K 20.7, Ca 65.9 und Mg 17.8 kg ha −2 a −1 auf der Flache B. Bei der Blattstreu der beiden Dominanten wurde eine bedeutende, saisonale Variabilitat in den Konzentrationen von N, P und K beobachtet, wahrend Ca und Mg keine wichtigen Unterschiede aufwiesen. N, P und K wurden in andere Baumorgane verlagert und Ca, Mg, Mn und Al wurden in den voll entwickelten Blattern akkumuliert. Der Vergleich zwischen Blattstreu und frischen, voll entwickelten Blattern legt die Vermutung nahe, dass die Analyse der Blattstreu die der lebenden Blatter nicht ersetzen kann, um den Nahrstoffstatus der untersuchten Arten bezuglich der essenziellen Elemente N, P und K zu bewerten. Der Index der Nahrstoffnutzungseffektivitat im Streufall kann als Indikator fur die Bodennahrstoffbedingungen genutzt werden. Wir fanden probeflachenabhangige und interspezifische Unterschiede im Nahrstoffgehalt und in der Nahrstoffremobilisierung. Der Nahrstoffzyklus folgt einem Muster, das dem tropischer Walder gleicht, mit ineffizienter Nutzung von N und effizienterem Kreislauf des P innerhalb des Bestandes.

EVALUATION OF THE USE OF SYNTHETIC RED SOIL AGGREGATES (SRA) AND ZEOLITE AS SUBSTRATE FOR ORNAMENTAL PLANT PRODUCTION

This research was undertaken to evaluate the influence of zeolite and synthetic aggregates (SRA) produced with acidic red soil and paper waste, on the growth of French marigold (Tagetes patula), which is a popular ornamental plant in Japan. Five different media were studied: SRA only, SRA:Zeolite 3:1, SRA:zeolite 1:1, SRA: zeolite 1:3 and zeolite only. Mixing SRA with zeolite improved the physical and chemical properties of the media such as particle size distribution, bulk density, total porosity, water holding capacity, and pH compared to zeolite. SRA and zeolite at 1:1 gave the best maximum growth parameters of French marigold. Zeolite based mixtures increased the nitrogen (N), potassium (K), magnesium (Mg), and calcium (Ca) concentrations in plant tissues compared to SRA medium. Addition of zeolite led to reduce K leaching from the substrate compared to SRA. SRA and Zeolite at 1:1 can be recommended as a better substrate for French marigold cultivation.