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21.
Antonio RUIZ-NAVARRO Manuel DELGADO-BAQUERIZO Concha CANO-D&#;AZ Carlos GARC&#;A Felipe BASTIDA 《土壤圈》2023,(6):828-837
Phosphorus (P) limitation in the coming decades calls for the utilization of alternative fertilizers in agriculture. Struvite is a promising P source, but its potential role as a fertilizer is dependent on different physical, chemical, and biological properties, which are very heterogeneous in soil, complicating the prediction of the best soil conditions for its application. Here, we evaluated the solubility of struvite in soil, its redistribution into P fractions, and its potential abiotic and biotic drivers in 62 globally distributed soils with contrasting properties through an incubation assay. We found that after 40 d, about 35% of struvite P was redistributed into soil fractions more accessible to plants and microbes. Phosphorus redistribution from struvite was driven by a complex suite of soil physical, chemical, and microbial properties as well as environmental factors that varied across soils. Soil texture played a critical role in determining the redistribution of P in struvite-amended soils in soluble (H2O extraction), labile (NaHCO3 extraction), and moderately labile (NaOH extraction) fractions. In addition, the soil solution cation concentration was one of the most important drivers of available struvite-derived P fractions. The great importance of texture and cations in determining struvite-derived P fractions in soil was contrasted with the relatively minor role of pH. At the microbial level, the number of bacterial operational taxonomic units (OTUs) from the unfertilized soils that correlated with struvite-derived P fractions was higher than that of fungi. The number of OTUs that correlated with the struvite-derived soluble P fraction was dominated by fungi, whereas the number of OTUs that correlated with the struvite-derived labile P fraction was dominated by bacteria. Overall, this study provided a predictive framework for the potential use of struvite as a P fertilizer in contrasting soils. 相似文献
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Maintaining soil phosphorus(P) at adequate levels for plant growth requires assessing how the long-term P balance(viz., the difference between P inputs and outputs) results in changes in soil test P. The hypothesis that routinely measured soil properties can help predict the conversion factor of P balance into Olsen P was tested at 39 sites in agricultural areas of the Mediterranean region in Spain. A set of soil samples from each site was analyzed for Olsen P, inorganic P(P extracted using 0.5 mol L~(-1) H_2SO_4), pseudototal P(P extracted using 0.5 mol L~(-1) H_2SO_4 following ignition at 550℃), and organic P(the difference between pseudototal P and inorganic P). Organic and Olsen P were uncorrelated in most of the 39 soil sets, which suggests that organic P content changed little with P inputs and outputs. The slopes of the regression lines of Olsen P against pseudototal and inorganic P, which were used as two different measures of the conversion factor, ranged widely(from 0.03 to 0.25 approximately), with their average values(about 0.10) being similar to those found in long-term experiments conducted in temperate areas. Neither conversion factor was significantly correlated with any routinely measured soil property; however, the conversion factor for inorganic P was significantly lower for calcareous soils than for noncalcareous soils. Our negative results suggest the need to isolate the influence of soil properties from that of management systems and environmental factors relating to P dynamics in future studies. 相似文献
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The phenology of Verticillium albo-atrum ( Vaa) sporulation on infected tissues and the presence of Vaa in the air were investigated in alfalfa fields affected by verticillium wilt (VW) during the 1983/84 growing season. Few and scattered Verticillium conidiophores developed on stubble by the end of May, but abundant Verticillium sporulation was found on necrotic leaflets and petioles by the beginning of June at the first appearance of symptoms. Abundant conidiophores developed also on necrotic stems and leaf tissues sampled later. Sporulation was never found on entirely green stems. Concentration of airborne colony-forming units (cfu) of Vaa ranged from 0.0 to 15.3 cfu/m3 above fields with a VW incidence of 2.2-33.0% in June and August, and from 5.9-25.9 cfu/m3 during mowing of the crop in August. The ratio of Vaa to other airborne fungi above sampled fields was less than 5 x 10-3 , Airborne fungi were even more abundant at the time of mowing. Our results suggest that airborne V. albo-atrum may not play an important role in the epidemiology of VW of alfalfa. 相似文献
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The results of the screening for antibacterial activity of 30 medicinal plants from north, east and central Sudan are reported. 相似文献
25.
J. BEJARANO-ALCÁZAR M. A. BLANCO-LÓPEZ J. M. MELERO-VARA & R. M. JIMÉNEZ-DÍAZ 《Plant pathology》1997,46(2):168-178
Experiments were conducted in the Guadalquivir Valley of Andalucía, southern Spain, in 1986 and 1987, using field plots naturally infested with different inoculum densities of the defoliating and nondefoliating pathotypes of Verticillium dahliae to determine the influence of verticillium wilt epidemics on yield of cotton cultivar Coker 310. The total number of bolls, the number of open bolls, and seed cotton yield were related to the growth stage of plants at first appearance of foliar symptoms, and to inoculum density and virulence of the V. dahliae pathotype prevailing in the soil. For the three yield components, the greatest reduction was observed in plants showing symptoms before opening of first flowers (about 650 degree-days after sowing). Yield increased with delay in the development of foliar symptoms during the crop season, and the effect of the wilt epidemics on yield was small or nil for plants that developed symptoms after opening of the first bolls (1400–1500 degree-days after sowing). A multiple regression equation was derived that related yield reduction to the physiological time accumulated from the time of sowing until the appearance of foliar symptoms and to the rate of disease intensity increase over physiological time. This multiple point model explained about 70% of the variation in cotton yield loss due to verticillium wilt. 相似文献
26.
Miguel Avendaño DÍAZ Marcela Cantillánez Silva Juan Peña Forner 《Aquaculture International》2006,14(3):267-283
A pilot program to evaluate the feasibility of collecting juvenile (seed) scallops using Japanese technology was carried out from October 2001 to April 2002 in the Marine Reserve at La Rinconada, Antofagasta, Chile. The continuous presence of larvae in waters in the reserve allowed for collection of 400–15,340 spat per collector and showed the high reproductive capability of local scallops and the relationship between numbers of larvae in the water and amount of spatfall. Highest rates of settlement were proportional to high numbers of umbone larvae in the water at >5000 larvae m−3 when collectors were first immersed. Absence of a relationship between larval numbers and postlarval settlement with trophic factors such as chlorophyll and particulate organic matter in the water suggests that productivity was not limited by these factors. Harvest of spat from collectors immersed for four and five months had recovery efficiencies of 5.5% and 59.4% compared with settlement in collectors after immersion for one month. Cohort analyses of recovered spat suggested that settlement occurred over the lengthy immersion period and was due to the continuous presence of larvae in the water. The loss of a high percentage of spat over the 4–5 immersion period compared with settlement in the first month can be attributed to intraspecific competition of spat density and growth as well as clogging of the collectors by sediment and marine fouling that impeded a flow of water through the nets. 相似文献
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