Phenolic acid content of soils from wheat-no till, wheat-conventional till, and fallow-conventional till soybean cropping systems

Abstract

Soil core (0-2.5 and/or 0-10 cm) samples were taken from wheat no till, wheat-conventional till, and fallow-conventional till soybean cropping systems from July to October of 1989 and extracted with water in an autoclave. The soil extracts were analyzed for seven common phenolic acids (p-coumaric, vanillic,p-hydroxybenzoic, syringic, caffeic, ferulic, and sinapic; in order of importance) by high-performance liquid chromatography. The highest concentration observed was 4 μg/g soil forp-coumaric acid. Folin & Ciocalteu's phenol reagent was used to determine total phenolic acid content. Total phenolic acid content of 0- to 2.5-cm core samples was approximately 34% higher than that of the 0- to 10-cm core samples. Phenolic acid content of 0- to 2.5-cm core samples from wheat-no till systems was significantly higher than those from all other cropping systems. Individual phenolic acids and total phenolic acid content of soils were highly correlated. The last two observations were confirmed by principal component analysis. The concentrations were confirmed by principal component analysis, tions of individual phenolic acids extracted from soil samples were related to soil pH, water content of soil samples, total soil carbon, and total soil nitrogen. Indirect evidence suggested that phenolic acids recovered by the water-autoclave procedure used came primarily from bound forms in the soil samples.

Estudo fitoquímico e alelopático do extrato de caule de sucupira-branca (Pterodon emarginatus)

“…Há várias suspeitas de que substâncias da classe dos flavonóides possuam propriedades alelopáticas, mas poucas delas foram identificadas. Uma delas é a florizina, encontrada nas raízes da macieira, que causa a inibição do crescimento das plântulas da própria espé-cie, e alguns de seus derivados são tóxicos para outras plantas (Blum et al, 1991;Boufalis & Pellissier, 1994).…”

Influence of wheat straw and rhizosphere on seed germination, early seedling growth and bio-chemical attributes of Trianthema portulacastrum

“…Total phenolic content of soil from non-till wheat field were significantly higher than that from other systems ( Table 7). Most of the phenolic acids appeared to be accumulated in the top 2.5 cm of the soil and occurred in bound forms in the soil (Blum et al, 1991). Rhizosphere is an active zone where most of the bio-chemical interactions take place and it acts as reservoir of most of the active inhibitory compounds that accumulate by root exudation, leaching and/or microbial degradation.…”

“…The allelopathic activity of wheat has been attributed to hydroxamic acids and related compounds (Blum et al, 1991;Wu et al, 2000a) and phenolic acids (Copaja et al, 1999;Wu et al, 2001). Wheat seedlings, straw, aqueous extracts of residues and root exudates exerted allelopathic effects on a number of agricultural weeds (Steinsiek et al, 1982;Shilling et al, 1985;Muminovic, 1991;Wu et al, 2000a, b).…”

Hypothetical Standard Screening Bioassays

“…The F-C reactive compounds are surrogates for the promoter/modifier/inhibitor complex in leachates. The Folin-Ciocalteau reagent is reduced by substances with phenolic hydroxyl groups (e.g., cinnamic acids, hydroxybenzoic acids, gallic acid, tannic acids, and tyrosine), some substances without phenolic hydroxyl groups (e.g., pyridines, purines, alanine, cysteine, tryptophan, ascorbic acid, fructose, and proteins), some inorganic substances [e.g., iron sulphate, manganese sulphate, and potassium nitrate], and some other compounds (Anderson and Todd 1968;McAllister 1969;Box 1983;Ikawa et al 1988;Blum et al 1991Blum et al , 1992. F-C equivalent values could be expressed in terms of any of these compounds although substances with phenolic hydroxyl groups have been the primary reference compound used in the literature.…”