DRY MATTER PRODUCTION AND LEAF ELEMENTAL CONCENTRATIONS OF RAMBUTAN GROWN ON AN ACID ULTISOL

Little is known about the adaptability of rambutan (Nephelium lappaceum) to highly acidic soils rich in aluminum (Al). A 2-yr field study was conducted to determine the effects of various levels of soil Al on dry matter production, plant growth, and nutrient concentration in the leaves of four cultivars of rambutan. Cultivars and the cultivar x year interaction were not statistically significant for most variables measured in the study. Total, leaf, petiole, stem and root dry weights significantly increased at soil Al concentrations ranging from 0.67 cmol kg^?1 to 11.0 cmol kg^?1. At this range of soil Al, the concentrations of Al and manganese (Mn) in leaf tissue declined sharply. The results of this study demonstrate that rambutan is highly tolerant to acid soils and that tolerance may involve an Al- and Mn- exclusion mechanism.     

Physicochemical properties of the soils associated with shifting cultivation in Northern Thailand with special reference to factors determining soil fertility

Abstract

Recently agricultural activity in the mountainous area of northern Thailand has increased and problems relating to soil fertility have arisen. In order to gain basic information about the soil properties associated with shifting cultivation, physicochemical properties of the surface soils (0–10 cm) and subsoils (30–40 cm) were investigated in selected villages in the area. The physicochemical properties of the soils studied are summarized as follows: 1) The soils were rich in organic matter, content of which ranged from 11.4 to 63.3 g C kg^?1 in the surface soil. 2) The pH(H₂O) of the soils mostly ranged from 5 to 7 and soil acidity was more pronounced in the deeper horizons. In the surface soils, exchangeable Ca and Mg were generally dominant, whereas exchangeable Al was often predominant in the subsoils. 3) Most of the soils showed a medium to fine texture with more than 30% clay. The clay mineral composition was characterized by various degrees of mixture of kaolin minerals and clay mica with, in some cases, a certain amount of 2:1-2:1:1 intergrades. 4) According to the ion adsorption curves, most of the B horizon soils were characterized by the predominance of permanent negative charges. On the other hand, organic matter contributed to the increase of variable negative charges in the surface soils. The content of organic matter and the percentage of the clay fraction were essential for determining the CEC of the soils of the surface 10 and 30–40 cm depths, respectively. Under the field conditions, the composition of exchangeable cations largely reflected the soil acidity. In addition, the content of organic matter also showed a significant correlation with that of available N in the surface soils. Thus, soil acidity both in the surface soils and subsoils, organic matter content in the surface soils, and clay content in the subsoils were considered to be the main factors that affected soil chemical fertility in the area.     

Sugars of the unfermented sap and the wine from the oil palm,Elaeis guinensis,tree

The sugar composition of the unfermented sap from oil palm (Elaeis guinensis) trees growing in the plantations of the Nigerian Institute for Oil Palm Research, Benin City, has been determined. While sucrose concentration ranges from 9.59 to 10.59% (w/v) in the pure unfermented sap, that of either glucose or fructose is much less than 1% (w/v) (0.13–0.73% w/v). Raffinose occurs in traces only (0.13–0.35 w/v). These results were derived from our improved methods which eliminate completely, or reduce to a bare minimum, fermentation of the sap during collection. The variation with time of storage of the individual sugars in the sap during fermentation to form palm wine reveals that, as sucrose steadily decreases, fructose reaches a peak at 1.51% (w/v) at the 9th hour, and thereafter declines, while glucose and raffinose remain continuously low; all sugars disappear beyond the 33rd hour. Concomittantly, pH decreases from pH 6.60 at zero time and stabilizes at pH 3.30 after 48 h, while titrable acidity increases continuously up until the 96th hour. These changes account for the variations in the quality of palm wine during storages.     

Contribution of anecic earthworms to biopore formation during cultivation of perennial ley crops

Large sized biopores (diameter >2 mm) in the subsoil can be created by tap roots, which leave voids after their decay, or by the burrowing activity of anecic earthworms which may benefit from the temporary lack in tillage in perennial cropping systems. However, the interactions between root growth and earthworm activity in the process of biopore formation during perennial ley cropping are not well understood. The aim of this field study was to quantify the development of the abundance of the anecic earthworm Lumbricus terrestris and the biopore density during the cultivation of lucerne (Medicago sativa L.), chicory (Cichorium intybus L.) and tall fescue (Festuca arundinacea Schreb.) grown for either one, two or three years. An increased abundance of L. terrestris was already recorded after two years of continuous ley when compared with one year cultivation. The ley crop species had only minor influence on the abundance of L. terrestris. Biopore densities of both diameter classes under study (2–5 mm and >5 mm) were not significantly affected by the duration of ley cropping. In contrast, biopore densities were influenced by ley crop species. More biopores of diameter class 2–5 mm were recorded after chicory than after fescue. Lucerne cropping resulted in intermediate biopore density. Additionally, in an incubation experiment under field conditions, we quantified whether L. terrestris preferentially created new biopores or colonized abandoned, previously existing ones. After three weeks of incubation, one third of the adult individuals incubated in the experimental area created new biopores at 0.4 m soil depth. A similar percentage of individuals colonized previously existing biopores, partially widening the lumen of smaller sized biopores. The remaining individuals remained in the topsoil. Sub-adult individuals rarely formed new pores. Half of the introduced sub-adults remained in the topsoil. We conclude that in crop rotations new biopores can be generated during perennial ley cropping by taproot systems of ley crops, but that a two to three- year period without tillage is not sufficient for populations of anecic earthworms to make a marked contribution to biopore density in the subsoil. The relevance of anecic earthworms for altering physical and chemical properties of biopores during ley cropping still needs further investigation.     

施用不同土壤改良剂对砖红壤酸度的影响

对砖红壤施用不同的改良剂,经一年的大田试验,测定土壤的活性酸与交换酸研究不同土壤改良剂对酸性土壤酸度的影响。试验结果表明：滤泥单施与石灰单施处理能有效降低土壤的活性酸以及交换性酸的含量,有较好的降低土壤酸度的效果,而施用绿肥、甘蔗渣、羊粪以及羊粪与膨润土混施均不能有效降低土壤的酸度。     

Optimization of Fermentation Condition of Yeast Culture

Culture condition of every phase for fermentation of yeast culture was studied, and its solid and liquid conditions of elaboration were optimized to improve the total counts of living cells. Results showed that microzyme grew best at 30℃ when solid fermented, and the count of the living cells reached the tiptop with pH 5.5. The count of Candida tropicalis could reach 137.96× 10^9 cfu·g^-1, the count of Saccharomyces cerevisia could reach 134.62× 10^9 cfu·g^-1 the best liquid fermentation condition for cell-wall broken was 50℃ for 28 h, the rate of cell-wall broken could reach 80% at least; the rate of vitamin loss in yeast could be the minimun, the loss rate of vitamin B6 in Candida tropicalis and Saccharomyces cerevisiae was 8.71% and 19.54% respectively, the loss rate of vitamin B2 was 19.39% and 13.18%, respectively, and the loss rate of vitamin B6 was 6.3% and 3.04%, respectively.     

Instrumental and sensory quality characteristics of blueberry fruit from twelve cultivars

We compared the instrumental and sensory quality characteristics of blueberry fruit from ten highbush (Vaccinium corymbosum L.) cultivars, Chanticleer, Weymouth, Hannah's Choice, Duke, Bluecrop, Coville, Berkeley, Bluegold, Elliott and Lateblue and two rabbiteye (Vaccinium virgatum Aiton) cultivars, Coastal and Montgomery, grown in New Jersey. Cultivars varied in sensory intensity and acceptability scores. Highbush cultivars, Coville and Hannah's Choice, scored highest among the cultivars in sensory scores for intensity of blue color, juiciness, sweetness and blueberry-like flavor and for acceptability of appearance, color, fruit size, sweet/tart balance, flavor and overall eating quality. In contrast, rabbiteye cultivars, Coastal and Montgomery, and the highbush cultivars, Elliott and Weymouth, scored lowest among the cultivars in sensory scores for intensity of bursting energy, skin toughness, texture during chewing, juiciness, and blueberry-like flavor and for acceptability of appearance, color, fruit size, flavor and overall eating quality. Analytical quality characteristics of surface color, size, compression firmness, soluble solids content (SSC), pH, titratable acidity (TA), SSC/TA ratio, and aromatic volatile concentration also varied among cultivars, but no instrumental measurement adequately predicted consumer acceptability scores. The overall eating quality of blueberry fruit was best correlated with flavor scores followed by sensory scores for intensity of juiciness, bursting energy and sweetness and for acceptability of appearance.     

茶树叶和刺槐叶对茶园土壤酸度的改良效果

通过培养实验,比较研究了茶树老叶和刺槐叶对2种酸化茶园土壤的改良效果.结果表明,在酸性茶园土壤中分别加入5、10和20g·kg-1茶树老叶和刺槐叶培养35 d后,相对于对照,土壤pH值有不同程度的提高,土壤交换性酸减小,土壤交换性钙和镁等交换性盐基离子数量有所提高,土壤毒性铝离子的数量减少.2种树叶对土壤酸度的改良效果随其加入量的增加而增加,刺槐叶的改良效果好于茶树老叶,2种树叶对红壤的改良效果优于其对黄棕壤的改良效果.植物物料所含的灰化碱及豆科植物所含大量有机氮的矿化是导致土壤酸度下降的主要原因.     

红壤交换性碱和交换性酸的研究Ⅰ.与中性盐(Na2SO4, NaClO4和KClO4)的关系

用自动控制pH的装置定量研究了两种红壤类土壤胶体在三种中性盐溶液中的交换性碱和交换性酸的变化.发现在Na2SO4溶液中在pH低时出现交换性碱,pH高时出现交换性酸.砖红壤胶体的交换性碱比红壤胶体的大,并且在pH5.6附近还出现不受Na2SO4浓度影响的交换中性点.NaClO4和KClO4溶液中,在测定pH范围内只出现交换性酸,红壤胶体的数量比砖红壤胶体的大.同一土壤胶体在KClO4中的数量比NaClO4中的多.二者都有一峰值,对于砖红壤胶体前者在pH4.3,后者在pH5.8.提出了测定SO2-4-交换性碱的方法.