Short Root Densities and Surface Phosphatase Activities of Ectomycorrhizal Morphotypes in a Slash Pine Plantation

Abstract

Mineralization is the dominant process controlling soil-solution P in the Spodosols of the southeastern United States. Pine trees growing in these soils are typically colonized by ectomycorrhizal (EM) fungi that are known to produce phosphatases. Little, however, is known of the dynamics of EM short roots or phosphatase activity in tree plantations. To address this question, short root densities, EM morphotypes, and associated surface acid phosphomonoesterase in a 12-year-old Pinus elliottii plantation in northern Florida were evaluated. The density of total (living and dead) short roots changed little from February through June, with a mean of 7.6 cm³ soil. The majority of the short roots, however, were inactive or dead with only 14 to 38% appearing viable upon visual inspection. The majority of the viable short roots were mycorrhizal. The most abundant morphotypes were formed by Cenococcum and Thelephora but these had low phosphatase activity. In contrast, less frequently observed morphotypes had substantially higher rates of enzyme production and these may play an important role in sustainable P nutrition of plantation trees.     

Phosphorus and aluminium solubility relationships in acidic lowbush blueberry barren soils in Maine

Lowbush blueberry (Vaccinium angustifolium) is a native plant that is not cultivated, but managed in areas of sufficient plant density to provide commercial yields. A cropping systems study was initiated to compare how organic and three levels of conventional (low, medium and high input) management practices affected soil properties at 12 grower fields in the lowbush blueberry barrens of Maine. The fields under organic and low‐conventional treatments did not receive any fertilizer inputs. The high and medium conventional treatment fields received optimal and reduced diammonium phosphate inputs, respectively. Three measurements of soil P (modified‐Morgan soil test, oxalate extractable and total P) showed no significant effect of management treatment on the phosphorus status of the soils. This suggests that soil P may be leaching below the 0–10 cm rooting zone which was investigated in this study. Equilibrium chemical speciation of soil/water extracts showed that gibbsite was controlling the solubility of Al in these barren soils and that P was undersaturated with respect to amorphous Al(OH)₂PO₄. A laboratory one‐point P sorption study showed that dissolved organic matter derived from the organic pad sampled from the study sites did not inhibit the adsorption of the added P. This suggests that addition of carbon‐rich soil amendments such as compost may not increase P bioavailability of these acidic soils with high Al (oxy)hydroxide (gibbsite) mineral content.     

Response of rice to sulphur application under upland conditions

Abstract

A greenhouse experiment was carried out to determine the S response and the plant S content of rice (Oryza sativa L.) cultivars OS‐6 and IR‐20 grown in sandy Apomu soil series under upland conditions.

Sulphur application increased growth and dry matter yield. At low S rates OS‐6 gave higher grain yield than IR‐20. With high S rates, OS‐6 responded more in straw production. The leaf S content was highest during early growth and decreased with plant age. At flower emergence, the blade of the Y‐leaf appeared to be a suitable index for measuring the S status of the plant. The critical S level was estimated at 0.15%. The critical S levels in the grain and straw at harvest were estimated respectively at 0.12%, and 0.10%. The N/S ratios for the grain and straw at harvest appeared not to be a useful index for determining the critical S status of the plant.     

Corn (Zea mays L.) Grain and Stover Yield as Affected by Soil Residual Mineral Nitrogen

Evaluation of nitrogen (N) dynamic in soil using regression equations is important for proper determination of N fertilization. A 3-year field experiment was conducted to (1) develop the best-fitted regression model relating corn grain and stover yield to soil residual ammonium (NH₄)-N and nitrate (NO₃)-N for corn yield prediction and (2) evaluate how such a model can be beneficial to the health of ecosystem by predicting the appropriate rates of N fertilization for corn production. Soil NH₄-N and NO₃-N were determined at corn harvest at the depths of 0–30 and 30–60 cm. Nitrogen fertilizer rates and soil mineral N accounted for a maximum of 93% variation in corn grain yield. Soil mineral N enhanced corn yield more than N fertilizer. Totals of 63.1 and 14.1 kg/ha of soil residual NO₃-N and NH₄-N were found in the 0- to 60-cm depth, indicating the importance of performing soil N tests.     

Effects of Organic Calcium Made by Bamboo Vinegar on Growth of Cymbidium ensifolium and Soil Property

The bamboo vinegar was used to produce organic calcium,and different concentrations of NaCl,CaCb and organic calcium solutions as deicer were sprayed evenly on the potted Cymbidium ensifoiium and collected soil, and the growth of C.ensifoiium was observed everyday,and the physical and chemical properties of soil were analyzed.The results indicate that all the 3 types of salt solutions had certain influence on C.ensifolium,while the organic calcium had less effect on C.ensifolium than NaCl and CaCl₂,and both of NaCl and CaCl₂ had little effect on the pH of soil while organic calcium increased greatly the pH of soil,and the organic matter and cationic exchange capacity of soil reduced,and the content of total N, P in soil also reduced while the apparent content of total K in soil increased.By above comparison,the effect of organic calcium made by bamboo vinegar on C.ensifolium and soil was less than that of NaCl and CaCl₂,in addition smaller the concentration of salt solution was,less the effect of salt solution on C.ensifoliumand soil was.     

有机黄瓜生产中霜霉病的防控技术

根据防治黄瓜霜霉病的实践经验,系统总结有机黄瓜霜霉病综合防控技术,解决有机黄瓜生产中遇到的首要问题,助推有机农业的健康发展。     

柿子发酵酒酯的生成规律初探

分析了不同柿子发酵酒样品中的主要有机酸和主要酯香成分，结果表明，柿子发酵酒中主要有机酸有酒石酸和乳酸，主要挥发酯是乳酸乙酯和乙酸乙酯。自然老熟的柿酒中乳酸乙酯含量高于乙酸乙酯，采用冷热处理方法老熟的柿酒中乙酸乙酯的含量高于乳酸乙酯。     

Effect of GRAS compounds on mycelial growth, pectic enzyme activity and disease severity of postharvest pathogens on rambutan (Nephelium lappaceum)

The GRAS compounds cinnamaldehyde (at 30 ppm), acetaldehyde (at 70 ppm), benzalde-hyde (at 50 ppm) and potassium metabisulphite (at 250 ppm) either completely inhibited or significantly reduced thein vitro mycelial growth ofGliocephalotrichum microchlamydosponim,Colletotrichum gloeosporioides andBotryodiplodia theobromae, the causative fungi of brown spot, anthracnose and stem end rot, respectively, of rambutan fruits,Nephelium lappaceum. The four compounds also significantly reduced the severity of all three diseases and the activity of pectic lyase and polygalacturonase enzymes secreted by the three fungi.     

Effect of temperature,organic amendment rate and moisture content on the degradation of 1,3‐dichloropropene in soil

1,3‐Dichloropropene (1,3‐D), which consists of two isomers, (Z)‐ and (E)‐1,3‐D, is considered to be a viable alternative to methyl bromide, but atmospheric emission of 1,3‐D is often associated with deterioration of air quality. To minimize environmental impacts of 1,3‐D, emission control strategies are in need of investigation. One approach to reduce 1,3‐D emissions is to accelerate its degradation by incorporating organic amendments into the soil surface. In this study, we investigated the ability of four organic amendments to enhance the rate of degradation of (Z)‐ and (E)‐1,3‐D in a sandy loam soil. Degradation of (Z)‐ and (E)‐1,3‐D was well described by first‐order kinetics, and rates of degradation for the two isomers were similar. Composted steer manure (SM) was the most reactive of the organic amendments tested. The half‐life of both the (Z)‐ and (E)‐isomers in unamended soil at 20 °C was 6.3 days; those in 5% SM‐amended soil were 1.8 and 1.9 days, respectively. At 40 °C, the half‐life of both isomers in 5% SM‐amended soil was 0.5 day. Activation energy values for amended soil at 2, 5 and 10% SM were 56.5, 53.4 and 64.5 kJ mol^?1, respectively. At 20 °C, the contribution of degradation from biological mechanisms was largest in soil amended with SM, but chemical mechanisms still accounted for more than 58% of the (Z)‐ and (E)‐1,3‐D degradation. The effect of temperature and amendment rate upon degradation should be considered when describing the fate and transport of 1,3‐D isomers in soil. Use of organic soil amendments appears to be a promising method to enhance fumigant degradation and reduce volatile emissions. Published in 2001 for SCI by John Wiley & Sons, Ltd     

Identification and properties of a deviant isolate of the broad bean yellow band serotype of pea early-browning virus from faba bean (Vicia faba) in Algeria

A virus, isolated from faba bean (Vicia faba) obtained from Algeria, was readily recognized as a tobravirus by its particle sizes and morphology. Pea (Pisum sativum) and French bean (Phaseolus vulgaris) characteristically reacted to the isolate like pea early-browning virus (PEBV), but faba bean,Antirrhinum majus, Nicotiana rustica, andN. tabacum reacted with line-pattern symptoms which were unusually brilliant on theNicotiana species. In electronmicroscope decoration tests, the isolate did not react with an antiserum to the Dutch type strain of PEBV, but with one to the broad bean yellow band (BBYB) serotype from Italy. It resembles this serotype in reaction on faba bean, but seems to differ appreciably onN. rustica, N. tabacum, andPetunia hybrida. It is described as a deviant isolate of the BBYB serotype of PEBV.All thirteen faba-bean genotypes tested were found to be susceptible to the Algerian isolate and two Dutch type strain isolates of the virus, and to react with erratic line-pattern symptoms to the Algerian isolate only. All ten genotypes of chickpea (Cicer arietinum) tested reacted hypersensitively, and four out of ten genotypes of lentil (Lens culinaris) were susceptible to the virus but reacted differentially to the three isolates. Seed transmission of PEBV, including the new isolate, in faba bean is confirmed (9% for the Algerian isolate, and over 45% for one of the Dutch type strain isolates), and seed transmission of the virus in a non-legume (N. rustica, 4%) is herewith first reported. This is the first report on the occurrence of the BBYB serotype of PEBV outside Italy, and of PEBV outside Morocco in North Africa.