11 research outputs found
Effects of cyanobacteria strains selected for their bioconditioning and biofertilization potential on maize dry matter and soil nitrogen status in a South African soil
Some cyanobacteria strains have biofertilization and/or bioconditioning effects in soils as a result of their ability to fix dinitrogen or produce exocellular polysaccharides. The objective of the present study was to screen indigenous cyanobacteria strains with the potential to improve the N fertility and structural stability of degraded soils, and evaluate their ameliorative effectiveness in semiarid soils of the Eastern Cape, South Africa. Soils from Guquka, Hertzog and Qunu villages, and Fort Cox College were used in the screening study. The results showed that only three cyanobacteria strains (3g, 3v and 7e) out of 97 isolated strains were heterocystous, with appreciable nitrogenase activity and the ability to produce exocellular polysaccharides. Nostoc strains 3g and 3v had a greater ability to produce exocellular polysaccharides, but low potential to fix dinitrogen (4.7 and 1.3 nmol C2H4 μg-1 chl h-1, respectively). Strain 7e had the greatest ability to fix dinitrogen (16.1 nmol C2H4 μg-1 chl h-1), but produced fewer exocellular polysaccharides. The ability of strains 3g and 7e to influence maize dry matter (DM) and soil C and N contents was tested in a nitrogen-poor soil with Nostoc strain 9v as a reference strain. Potted soils with and without growing maize plants were inoculated with the different cyanobacteria strains in a glasshouse at a rate of 6 g m-2 soon after maize emergence. Harvesting and soil sampling were done 6 weeks after inoculation. Inoculation with strains 3g and 7e increased maize DM and N uptake significantly, on par with the reference strain. These increases were consistent with increases in nitrate-N observed at harvest time in inoculated cropped and non-cropped soils. Strain 7e resulted in greater increases in soil nitrate-N, tissue N and uptake than strain 3g, perhaps because of its greater ability to fix dinitrogen. Cropping with maize reduced soil total C and N, possibly owing to its negative effects on cyanobacteria establishment. These results suggest that indigenous cyanobacteria strains screened for greater N2-fixing ability have the potential to improve the productivity of N-poor soils in semiarid regions in South Africa. © 2010 Japanese Society of Soil Science and Plant Nutrition.This work was part of a European Union INCO-DEV funded research programme in Southern Africa (CYANOSOILS), Project ICA4-CT-2001-10058. The National Research Foundation of South Africa granted a fellowship to the first author to undertake the study at the University of Fort Hare. We thank Antonia Herrero and José Enrique Frías of Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas, Sevilla, Spain, for their assistance with the isolation and characterization of the cyanobacteria strains
Nostoc cyanobacterial inoculation in South African agricultural soils enhances soil structure, fertility, and maize growth
13 pages, figures, and tables statistics.Many soils in South Africa have low nutrient
supply, poor structural stability and are prone to soil
erosion due to susceptibility to surface sealing and
crusting. Two crusting soils from the Eastern Cape
Province, South Africa were used to evaluate the effects
of inoculation with a strain of Nostoc on soil structure,
fertility and maize growth. The Nostoc suspension was
uniformly applied over potted soils at a rate of 6g (dry
weight) per square meter soon after maize germination.
Nostoc inoculation increased soil N by 17% and 40%
in Hertzog and Guquka soils, respectively. Soil C was
also increased significantly and this increase was
strongly associated with that of soil N (R2 = 0.838).
The highest contents of soil C, soil N and mineral N,
however, were found in non-cropped Nostoc inoculated
soils. Nostoc inoculation increased maize dry matter
yields by 49% and 40% in Hertzog and Guquka soils,
respectively. Corresponding increases in maize tissue
N were 23% and 14%, respectively. Scanning electron
microscopy (SEM) revealed that soil particles and
fragments of non-cropped inoculated soils had coatings
of extracellular polymeric substances (EPS) with other
particles enmeshed in networks of filaments, whilst by
contrast little or no EPS and/or filaments were observed
on cropped and/or non-inoculated soils. This
was consistent with chemical analysis which showed
that Nostoc caused significant increases in the EPS and
soil C contents of non-cropped soils. The proportion of
very stable aggregates was increased by inoculation
with Nostoc possibly due to the greater quantities of
soil C and EPS observed in inoculated soils. Inoculated
soils cropped with maize had a lower proportion of
stable aggregates presumably due to their low soil C
and EPS contents compared to non-cropped soils. The
results suggested that Nostoc could improve the fertility
and structural stability of the studied degraded soils.This work was part of an EU, INCODEV funded research programme in Southern Africa (Cyanosoils),
Project ICA4-CT-2001-10058.Peer reviewe
Algae and Cyanobacteria as Biocontrol Agents of Fungal Plant Pathogens
none2noAbstract: Since long time, algae are used in agriculture as soil amendment for their
beneficial effects on plant health and productivity. In fact, algae contain several
molecules such as plant growth hormones (cytokinins, auxins, abscisic and
gibberellic acid), polysaccharides, betaines and micronutrients. The research on
algae, their compounds and their effects on plants have started in the middle 1950s
and brought to the formulations of liquid products containing extracts with compounds
readily available for plants. The algae extracts, besides having effects on
plant growth, have demonstrated to improve plant resistance to both abiotic and
biotic stresses. Among biotic stresses, algae showed antifungal activity against
different pathogens especially of horticultural plants. From the middle of last
century, plant management has always been dependent from the market demand
that required growing quantity of ‘perfect’ fruits and vegetables over the year. In this
scenario, the chemical industry of fertilizers and pesticides developed new products
that have been used for years. In particular, pesticides have represented the base of
the management of fungal plant pathogens. During the last decades, the use of both
pesticides and chemical fertilizers has represented a serious risk for human health
and brought disorder of ecosystem equilibrium. Consequently, algae for their
biostimulant and antifungal effects may be considered useful tools to reduce the
input of chemicals in integrated pest management strategies. In line with these
strategies, the European Regulation EC 1107/2009, concerning the placing of
plant protection products on the market and repealing Council Directives 79/117/
EEC and 91/414/EEC, recommends that priority should be given to non-chemical
and natural alternatives wherever possible.mixedHillary Righini; Roberta RobertiHillary Righini; Roberta Robert