Preliminary evaluation of pineapple mixed-cropping systems for protecting reclaimed gulleys in the tropics: An experiment in Southeast Nigeria

This paper reports on research into the effectiveness of pineapple monocropping or intercropping systems (with cowpeas or egusi-melon) for reestablishing vegetative cover to check soil erosion on a reclaimed gulley in the tropical rainforest of southeastern Nigeria. High-density pineapple planting, intercropped with egusi-melon, was found to promote rapid vegetative cover, checked soil loss, improved soil structural stability and produced a high crop yield. Soil loss was moderate in pineapple plots intercropped with cowpeas and least in pineapple plots intercropped with egusi-melon. Increasing pineapple density enhanced the field establishment of cowpea and egusi-melon respectively.     

Concentrations and depositions of SO2, SO4 2− etc. in a Chongqing suburban forested area

During the period from 25 May 1991 to 30 May 1992 the atmospheric concentrations and depositions of oxides of sulfur were continuously measured in a suburban masson pine forest which is currently experiencing severe dieback, in Chongqing, China. The annual mean concentrations of SO₂ and particulate SO₄ ^2? were 220 μ g/m³ (77 ppbv) and 32 μ g/m³ respectively. The atmospheric concentrations of these sulfur compounds were high in late autumn and winter. The annual wet and dry depositions of sulfur to the forest as measured by throughfall and stemflow were 93.1 and 46.6 kgSha^?1a^?1 respectively. These depositions are among the highest level ever reported in the world. Althogh the cause of the dieback of the masson pine trees has not been unequivocally determined, it is probable that the direct impact of SO₂ is more likely the cause than acid deposition.     

Effect of tillage and residue management on properties of two coarse-textured soils and on yield of irrigated wheat and groundnut

Changes in soil properties and yield response in relation to tillage and residue management treatments in an irrigated groundnut (Arachis hypogea L.)—wheat (Triticum aestivum, L.) rotation on a sandy soil (1972–1974) and on a sandy loam soil (1974–1976) were evaluated. Tillage treatments (T₁ and T₂) did not cause significant changes in soil properties. Incorporation of crop residues (5 t residue per ha per crop, T₃) caused a substantial increase in organic C, available N, and NaHCO₃ -extractable P contents in the top 15 cm of both soils. Residue management treatments (T₃, T₄ and T₅) showed no significant effect on soil bulk density and exchangeable K. Crop yields under no-tillage (T₁) and conventional tillage (control, T₂) were comparable on sandy soil but on the sandy loam soil, no-tillage yielded significantly lower than conventional tillage. Compared with the control, incorporation of crop residues (T₃) caused higher yields on sandy soil for groundnut and wheat by 34.1 and 47.4%, respectively, and on sandy loam by 17.1 and 7.2%, respectively. Mulching with crop residues conserved soil moisture and reduced maximum soil temperature (1.5–5.3°C in groundnut and 1.5–2.9°C in wheat) but other measured soil properties were not significantly affected. Significant yield increase due to residue mulching (T₄) was observed in sandy soil but it was significantly less than when total crop residue was incorporated (T₃). Increased wheat root-weight density in the top 15 cm soil with residue mulching was not reflected in grain yield. Compared with the incorporation of the total amount of crop residue (T₃), incorporation of half the amount and application of the other half as mulch (T₅) caused lower yields — on sandy soil for groundnut and wheat by 31.5 and 15.7%, respectively, and on sandy loam by 4.8 and 3.6%, respectively.     

Problems of official methods and new techniques for analysis of foods and feeds for vitamin A

The official methods for measuring vitamin A and carotene in foods and feeds have evolved over several decades. New procedures are needed to permit the use of modern analytical techniques such as liquid chromatography (LC), and to expand the application of official methods to a wide variety of foods. Recent improvements in methodology are reviewed. Emphasis is often placed on the separations achieved by LC, but all factors that affect quantitation, such as sampling, preparation of standards, and protection of the vitamin against oxidation, must be considered in the development of new methods. Many approaches to analysis are possible because of the versatility of LC but not all of them can be used in official methods. Methods for milk, margarine, and feeds can be prepared now for collaborative assays. Although straightforward methods can be developed for the measurement of beta-carotene in certain foods, a full examination of provitamins will probably continue to require a flexible approach and special expertise.     

Influence of carbon substrates and moisture regime on nitrogen fixation in paddy soils

The influence of several carbon sources on heterotrophic N₂ fixation in four paddy soils under flooded and nonflooded conditions was investigated by ¹⁵N-tracer technique. Greater N₂ fixation occurred in submerged soils amended with cellulose and rice straw, the former being superior. Addition of sucrose, glucose and malate in that order stimulated N₂ fixation in submerged alluvial soil, while sucrose alone enhanced N₃ fixation in laterite soil. In submerged acid soils none of these C sources stimulated N₂ fixation. Nonflooded conditions favoured N₂ fixation in alluvial and acid saline soils amended with cellulose, sucrose and glucose.     

Schwefeldioxid,Schwefelwasserstoff, nitrose Gase und Ammoniak als ausschließliche S- bzw. N-Quellen der höheren Pflanze

Sulphur dioxid, hydrogen sulphate, nitrous gases, and ammonia as sole source of S and N for higher plants Long duration gasing experiments using SO₂, H₂S, nitrous gases and NH₃, showed, that higher plants can use these gases as only source of S or N respectively, without affecting their normal growth during the whole vegetation period. The sulphur and nitrogen of these high oxidized or high reduced gas forms were taken up by the plants and were also translocated to the roots. The assimilation of sulphur, given as SO₂, was more intensive than that given as H₂S. The uptake of nitrogen, given as ammonia, was higher than that given as nitrous gases.     

The effects of time of incubation on the relation between charge and pH of soil

Samples of two Andisols and two Ultisols from southern Chile were incubated with acid or with lime for up to 60 d at 25°C or for 1 day at 40°C or at 60°C. The changes in positive and negative charge were measured. The Andisols reacted slowly at 25°C. They lost protons to the solution at high _pH, thus increasing the negative charge on the soils and decreasing the pH of the solution. They gained protons at low _pH, thus increasing the positive charge on the soils and increasing the _pH of the solution. The Ultisols reacted more quickly but again charge and _pH changed through time. For all samples, the rate of reaction was increased by incubating at 60°C. Brief incubation at 60°C produces a similar relation to that obtained after longer incubation at 25°C. This provides a convenient means by which measurements can be made more quickly.     

Population densities of clover rhizobia in Texas pastures and response to liming

Summary Clovers are widely used forage legumes on acidic soils in Texas and need inoculation with appropriate rhizobia when first introduced. Acidic soils are not conducive to survival of clover rhizobia. A survey of pastures was undertaken to determine the number of rhizobia present. The effect of liming acidic soils on the survival of clover rhizobia was also evaluated in the laboratory. The number of clover rhizobia was more than 100 cells g^-1 soil in 70% of the pastures surveyed but populations within pastures varied by more than two orders of magnitude. The number of years of clover production beyond 1 year did not affect the rhizobial population density. The soil pH of twelve samples was below 5.0 and six samples had populations of rhizobial lower than 100 g^-1 soil. Eleven out of sixteen samples from fields that had grown clover and had pH values above 6.0 had populations exceeding 1000 g^-1 soil and only three samples had populations lower than 100 g^-1 soil. Incubating indigenous or inoculated rhizobia in well-mixed soils having pH values of 5.1 or below resulted in populations declining to below 10 g^-1 soil in 6 weeks. Mixing of soils with pH values of up to 5.4 induced reduction of rhizobial numbers, possibly by destroying microsites. Liming of soils to increase pH values above 5.5 improved survival of native or inoculated rhizobia in most cases.     

Growth,physiology, and nutrition of loblolly pine seedlings stressed by ozone and acidic precipitation: A summary of the ropis-south project

Previously published results from a multidisciplinary research program, Response of Plants to Interacting Stress (ROPIS), initiated by the Electric Power Research Insitute are summarized here. The overall objective of the ROPIS program was to develop a general mechanistic theory of plant response to air pollutants and other stresses. Direct and indirect phytotoxic impacts of O₃ combined with induced deficiencies of key nutrients as a consequence of acidic deposition are important components in many of the hypotheses used to explain reported declines in forest growth. In order to address these concerns as they relate to loblolly pine (Pinus taeda L.) growth and develop a greater level of mechanistic understanding of stress response, a study was formulated with two major objectives: (i) over a multi-yr period evaluate the role of loblolly pine genotype in governing loblolly growth response to O₃; and (ii) determine the underlying physiological and edaphic basis for loblolly growth response to O₃, acidic precipitation, and soil Mg status. An open-top chamber facility located at Oak Ridge, TN provided controlled O₃ exposure for the genotype screening study (1986–88) and controlled O₃ exposure and rainfall exclusion and addition for the O₃-rainfall acidity-soil Mg interaction study (1987–89). A variety of experimental techniques, measurements, and statistical procedures were used over a 4-yr period to quantify various aspects of plant growth, physiology, and soil-plant relationships. Results from the genotype screening study indicate that although family-specific O₃ effects were observed at the end of the first year, no statistically significant O₃ effects on diameter, height, or total biomass were evident at the end of three growing seasons; nor were any significant O₃-family interactions found. In the interaction study, rainfall acidity and soil Mg level had only minimal affects on seedling growth and physiology. Ozone exposure produced significant changes in many variables, the most important being a net retention of carbon in above-ground biomass and a subsequent reduction in carbon allocation to the root system. This change could have important longterm implications for the tree's ability to obtain water and nutrients, maintain important rhizosphere organisms, and achieve a level of vigor that protects against disease and insect attack.