Fuminori Komai

CIELAB color variables as indicators of compost stability

The composting process of different organic wastes both in laboratory and on a large-scale was characterized using CIELAB color variables to evaluate compost stability for the better application in agriculture. The time courses of the CIELAB variables of composting materials were determined directly from the bottom of a glass petri dish filled with dried and ground samples using a Minolta Color Reader (CR-13) calibrated with clean empty petri dishes placed on a white tile. To compare the proposed method with conventional methods, the same materials were also evaluated using commonly used compost stability evaluation indices. Most of the CIELAB variables of a compost made from a mixture of green tea waste and rice bran reached a plateau after 84 days of composting and showed strong relationships with the commonly used compost stability evaluation indices. The time needed for CIELAB variables, especially the L*and b* values, to stabilize at large-scale composting plants of cattle litter, farmyard manure, kitchen garbage and bark compost, were more or less similar to the times of maturation evaluated by the respective compost producers. The CIELAB color variable offers a new, simple, rapid and inexpensive means of evaluating compost stability and its quality prior to agricultural use.

Evaluation of the Physio-Chemical and Microbial Properties of Green Tea Waste-Rice Bran Compost and the Effect of the Compost on Spinach Production

Abstract To study the physio-chemical and microbial properties of green tea waste-rice bran compost (GRC), and feasibility of GRC as the alternative of agrochemicals for quality spinach production, five types of compost were prepared by mixing green tea waste and rice bran. The compost temperature was increased by adding rice bran to the green tea waste. The compost GC made from green tea waste alone contained a relatively large amount of nitrogen (7.55%). On the other hand, the compost RC made from rice bran alone contained a relatively large amount of minerals, such as phosphorus (0.49%), potassium (4.96%) and magnesium (2.28%). Addition of rice bran increased the total number of bacteria, viable bacteria and organic matter decomposing bacteria as well as actinomycetes population in the mature compost. The frequency of organic matter decomposing bacteria in GRC was in the following order: cellulolytic bacteria < pectolytic bacteria < lipolytic bacteria < amilolytic bacteria except RC. The growth of spinach was significantly increased over the untreated control (only soil) when GRC was applied in the field and growth pattern was depended on the nature of the composting materials. The highest fresh weight of 27.5 g plant-1 and 45.4 g plant-1 were obtained by applying the compost with 30% green tea waste + 70% rice bran (GRC-3) under field condition in autumn of 2004 and 2005, respectively. The highest growth enhance effect was also obtained from GRC-3 when three spinach varieties were grown with GRC under greenhouse condition. The amount of nitrate and oxalate in the spinach grown with GRC were ranged from 114.0 to 146.0 mg 100 g-1 and 612.0 to 748.0 mg 100 g-1 fresh weight, respectively. These values were below from the safety standard of health level of nitrate and oxalate for spinach. The amount of ascorbic acid, glutamic acid and iron in the spinach were increased by applying the compost. Among the five combinations of GRC, GRC-3 provided the best results in spinach production.

Plasticity in sex expression of spinach (Spinacia oleracea) regenerated from root tissues

The sex expression of spinach (Spinacia oleracea L.) was modified by a procedure where plants were regenerated from root callus of spinach over three successive generations. Somatic embryos obtained from the root callus of female or male plants were grown in vitro under long day conditions until flowering. Although the regenerants derived from somatic embryos derived from female plants were all female at the first generation, few progenies produced male flower organs and expressed gynomonoecy in subsequent generations. Once the female plants regenerated into gynomonoecy, they never expressed complete femaleness at post generation. However, the male plants easily altered into andromonoecy at subsequent generations, and several andromonoecious plants showed the sex reversion at post generation, although this phenomenon did not occur in the female progenies. No absolute sex conversion was found in both female and male progenies. The plasticity of the sex expressions of spinach indicates that female and male individuals might essentially be capable of generating both flower organs.