Decomposition of algal cells and components and their stabilization through complexing with model humic acid-type phenolic polymers

Axenic cultures of Anacystis, Microcoleus, Plectonema and Synechococcus isolated from Greenfield sandy loam and of Anabaena flos-aquae, Nostoc muscorum and Chlorella pyrenoidosa from other sources were cultured under light and constant aeration and with [U-¹⁴C]-glucose in the nutrient medium. Whole cells, cell walls, cytoplasm and extracellular polysaccharides of selected species readily decomposed in the soil and after 22 weeks between 61 and 81% of the added C had evolved as CO₂. Complexing of cell wall and cytoplasmic preparations from A. flos-aquae and N. muscorum with model humic acid-type phenolic polymers reduced decomposition of the cell walls by 40% and of the cytoplasm by 70%. Over 50% of the residual 14C activity in the soil amended with whole algal cells remained in the 0.5% NaOH-extracted soil. With exception of Microcoleus sp. more of the residual ¹⁴C from cell walls, cytoplasm and polysaccharide fractions was present in the humic acid or fulvic acid fractions.     

Studies on soil fumigation—III: Effects on enzyme activities,bacterial numbers and extractable ninhydrin reactive compounds

Fumigation of a field soil with chloropicrin and methyl bromide, either singly or in combination, differentially decreased soil enzyme activities and viable bacterial numbers and increased the amounts of ninhydrin reactive compounds extractable with acidified Tris buffer. Chloropicrin treatment was more effective than methyl bromide.The rates of hydrolysis of both an amide and a peptide derivative were decreased by chloropicrin treatment and remained relatively low despite changes in activities over 325 days. By contrast, caseinase activity initially was decreased by both chloropicrin and methyl bromide fumigation, but activities of the fumigated soils recovered to exceed those of untreated soils. Thereafter, caseinase activities of fumigated and untreated soils exhibited relatively large fluctuations, which were partly associated with seasonal drying of the soils in the field.Chloropicrin but not methyl bromide fumigation markedly depressed the viable bacterial populations, which subsequently increased to be above those of the untreated soils. There was no consistent relationship between the release of ninhydrin reactive compounds following fumigation and changes in bacterial numbers or changes in enzyme activity. Autolytic reactions are probably important in the early stages of amino-nitrogen release in fumigated soils. Net gains in caseinase activity may be partly due to the production de novo of extracellular proteases by microorganisms or to the release of intracellular proteases from killed cells.     

Pathogens occurring on ten varieties of ryegrass at Rothamsted in 1973–74

Six varieties oi Loliumperenne, three of L. multiflorum and one hybrid (L. multiflorum × L. perenne) were assessed for diseases over two harvest years. Crown rust (Puccinia coronata) and mildew (Erysiphe graminis) occurred on some varieties in 1973. Leaf spotting (Drechslera spp.) was common, but slight on most varieties, in both years. Ryegrass mosaic virus (RMV) and its mite vector, Abacarus hystrix were present on all varieties in the second year. The relative susceptibility of varieties to RMV was similar in the field and in glasshouse tests.     

The effect of delayed autumn harvest on the survival of varieties of perennial ryegrass

The reactions of five early and five late varieties of perennial ryegrass to stimulation of bulky autumn growth and deferment of harvesting were compared in terms of spring growth and subsequent recovery during three winters. Winterkill was marked in 1971–72, particularly when harvesting was deferred to late November, in early varieties S24 and Presto Pajbjerg and in the late variety S23. Least affected among early varieties were Premo and Barvestra (tetraploid) and among late varieties, Perma and Barpastra (tetraploid). All varieties showed rapid recovery. The results are discussed in terms of the significance of winterkill, and the effects of age of sward, variety susceptibility and deferment of autumn defoliation. It is concluded that the form of winterkill which occurs in the west of Scotland can have serious consequences to farm productivity in severe winters. Autumn growth left standing into November can also lead to winterkill. Under good management, varietal differences are unimportant. In a severe winter, no varieties of perennial ryegrass are reliable.     

Removal of mineral nutrients by red clover varieties

K, P, Ca and Mg contents and uptakes are reported from total herbage of plots sown with six varieties of red clover harvested three times a year for 3 years. K, P and Mg contents were above those reported as critical for growth; values for Ca were lower than quoted ranges which suggested that growth might have been affected by either deficiency of Ca or low pH. Hungaropoly was characterized by relatively low K and P and high Ca contents. Maximum uptakes in red clover total herbages over 3 years were 1198 kg ha^?1 K (Hera), 112 kg ha^?1 P (Hera), 494 kg ha^?1 Ca (Hungaropoly) and 104 kg ha^?1 Mg (Mars). Results were compared with those found for S101 perennial ryegrass, harvested on a similar system and receiving similar fertilization with uptakes of 759 kg ha^?1 K, 100 kg ha^?1 P, 200 kg ha^?1 Ca and 46 kg ha^?1 Mg, by expressing accumulating uptakes and inputs as linear regression equations. The better varieties of red clover, Hera, Hungaropoly, Mars and S123 show rates of DM accumulation similar to S101 perennial ryegrass and similar uptake rates of K and P but higher rates of uptake of Ca and Mg. The levels of application of K and P used in the experiment seem to be more than adequate but attention to the Ca status may be required to sustain high-yielding red clover swards.     

An Experiment to Control Fomes annosus in Second Rotation Pine Crops

Stump removal was found to singnificantly reduce killing byFomes annosus in second rotation crops of pine. Poisoning andgirdling of trees prior to felling and also stump poisoningfailed to control the disease. In this experiment no significantdifferences were detected in the susceptibility of Scots andCorsican pine to attack. Increasing periods of delay beforereplanting resulted in less mortality. An equation is presented,based on factors of the first rotation crop which may be usedto predict losses likely to occur when a site is replanted.Root attack by F. annosus results in reduced growth and yieldas well as mortality. The results from the experiment are discussed in trems of themangement of pine crops attacted by F. annosus in Theford Chase.     

Automated high-pressure liquid chromatographic assay of robenidine hydrochloride.

High-pressure liquid chromatography has been applied to the separation and analysis of robenidine hydrochloride in the presence of its chemical precursors. It provides a rapid and specific method for the analysis of robenidine in technical material as well as feed premixes and is capable of distinguishing the intact drug from its degradation products. The chromatographic system employs a mixture of methanol, acetic acid, and methylene chloride as the mobile phase and a controlled pore glass as the stationary phase. Sample manipulation has been automated in 2 ways. In the first, manually prepared samples are automatically injected onto the column for separation and quantitation. In the second, a totally automated sample handling system, weighed samples are extracted, diluted, filtered, and then injected onto the column, all in a sequential manner. These procedures are capable of giving quantitative results at a rate of 10 samples/hr with a relative standard deviation of 1.13%.     

A comparison of some red and yellow earths in tropical queensland and northeast Brazil

Red and yellow earths are kaolinitic and generally sesquioxidic soils having massive B horizons with porous, earthy fabrics and weak profile differentiation but usually displaying a gradual increase in clay content with depth. They are widespread in tropical Queensland and northeast Brazil where comparable climates prevail although the vegetation is markedly different. Their parent materials are mostly quartzitic sedimentary rocks or unconsolidated sediments and the soils occur in a wide variety of topographic and geomorphic situations. In both regions it is probable that many of the soils have not formed under the present climatic conditions.Profile morphology, drainage, silt and clay contents, clay mineralogy, and soil chemistry have been compared and contrasted between the red and yellow earths within and between the two regions. Canonical variate analysis has shown that, on the basis of surface soil chemical attributes, the red earths can be separated from the yellow earths within each region and that the Queensland soils can be separated from the Brazilian soils.