Effects of Drought on Microbial Activity in Rhizosphere, Soil Hydrophobicity and Leaching of Mineral Nitrogen from Arable Soil Depending on Method of Fertilization

This work presents the first results from the long-term laboratory experiment dealing with impact of drought on soil properties. Three groups of the treatment (A, B and C) with different regime of irrigation were prepared. The soil water content was maintained at 70 % of soil water holding capacity in group A, at 40 % in group B. In group C, soil water regime was maintained in the range of wilting point. Each group of the experiment was divided into three variants (A1 = B1, C1; A2 = B2, C2 etc.) with three repetitions: Variants A1 (B1, C1) were controls without addition of another fertilizer. Variants A2 (B2, C2) were fertilized with mineral nitrogen fertilizer DAM 390 (0.140 Mg of N per ha) and variants A3 (B3, C3) contained 45 g of Cp per a pot. The significant differences (ANOVA, P<0.05) in the leaching of mineral nitrogen and values of saturated hydraulic conductivity (Ksat) were found. The highest values of Ksat were found in variants (within each group) with addition of compost (A3, B3, C3). Conversely, the lowest values of Ksat were found in variants with addition of mineral nitrogen. Low values of Ksat indicate an increased level of hydrophobicity in individual groups of the experiment. Moreover, all variants with compost addition showed lower amount of mineral nitrogen leaching and high level of microbial activity than variants without. This decrease of mineral nitrogen leaching was about 200 % in comparison with the control variant and about 300 % with variant, where mineral nitrogen was added. Based on these results, we can conclude that changes of soil water content directly have impact on microbial activity, soil hydrophobicity and loss of mineral nitrogen from the soil

Vplyv vermikompostu na zmeny bakteriálneho spoločenstva v rizosfére kukurice

The aim of the study was to observe changes in the diversity of bacterial community in maize rhizosphere influenced by organic and mineral fertilization. Four variants of fertilization were tested - vermicompost (VC) at recommended annual dose 40t*ha-1, doubled annual dose of VC, recommended dose of ammonium saltpeter with dolomite (LAD 27) and combination of VC and LAD 27. Experiment was conducted with potted maize plants in controlled conditions of greenhouse during 74 days. Using PCR-DGGE method, we investigated differences in total bacteria community as well as in community of ammonia oxidizing bacteria. Based on occurrence of operative taxonomic units (OTU) we found differences in bacterial species spectra among fertilization variants. The highest Shannon´s biodiversity index was observed in variant with VC addition in dose 80 t*ha-1.The fertilizers effect on diversity of ammonia oxidizing bacteria was not significant however in each variant with vermicompost addition was the occurrence of new specific OTU observed. This OTU was identified as Nitrosospira sp. It was proven that some bacterial species introduced to soil with vermicompost addition can survive for at least 74 days and these bacteria can influence basic functions of soil microbiocenosis in nitrogen cycle.Cieľom štúdie bolo sledovať zmeny diverzity bakteriálneho spoločenstva v rizosfére kukurice vplyvom organického a minerálneho hnojenia. Boli testované štyri varianty hnojenia – vermikompost (VC) v odporúčanej ročnej dávke 40t*ha-1, dvojitá ročná dávka VC, odporúčaná dávka liadku amónneho s dolomitom (LAD 27) a kombinácia VC a LAD 27. Experiment bol realizovaný na nádobách s rastlinami kukurice v kontrolovaných podmienkach skleníka počas 74 dní. Využitím metódy PCR – DGGE sme skúmali rozdiely v celkovej komunite baktérií ako aj komunite nitrifikačných baktérií. Na základe prítomnosti operatívnych taxonomických jednotiek (OTU) sme zistili rozdiely v spektrách bakteriálnych druhov v závislosti od variantov hnojenia. Najvyšší Shannonov index biodiverzity bol zaznamenaný vo variante s prídavkom VC v dávke 80 t*ha-1. Vplyv hnojenia na diverzitu nitrifikačných baktérií nebol preukazný, avšak v každom variante s prídavkom vermikompostu bol zaznamenaný výskyt nového špecifického OTU. Tento OTU bol identifikovaný ako Nitrosospira sp. Dokázalo sa, že niektoré druhy baktérií dodané do pôdy prídavkom vermikompostu sú schopné prežívať po dobu najmenej 74 dní a môžu ovplyvňovať základné funkcie pôdnej mikrobiocenózy v cykle dusíka

Effect of vermicompost on changes in the bacterial community in maize rhizosphere

The aim of the study was to observe changes in the diversity of bacterial community in maize rhizosphere influenced by organic and mineral fertilization. Four variants of fertilization were tested - vermicompost (VC) at recommended annual dose 40t*ha-1, doubled annual dose of VC, recommended dose of ammonium saltpeter with dolomite (LAD 27) and combination of VC and LAD 27. Experiment was conducted with potted maize plants in controlled conditions of greenhouse during 74 days. Using PCR-DGGE method, we investigated differences in total bacteria community as well as in community of ammonia oxidizing bacteria. Based on occurrence of operative taxonomic units (OTU) we found differences in bacterial species spectra among fertilization variants. The highest Shannon´s biodiversity index was observed in variant with VC addition in dose 80 t*ha-1.The fertilizers effect on diversity of ammonia oxidizing bacteria was not significant however in each variant with vermicompost addition was the occurrence of new specific OTU observed. This OTU was identified as Nitrosospira sp. It was proven that some bacterial species introduced to soil with vermicompost addition can survive for at least 74 days and these bacteria can influence basic functions of soil microbiocenosis in nitrogen cycle.Cieľom štúdie bolo sledovať zmeny diverzity bakteriálneho spoločenstva v rizosfére kukurice vplyvom organického a minerálneho hnojenia. Boli testované štyri varianty hnojenia – vermikompost (VC) v odporúčanej ročnej dávke 40t*ha-1, dvojitá ročná dávka VC, odporúčaná dávka liadku amónneho s dolomitom (LAD 27) a kombinácia VC a LAD 27. Experiment bol realizovaný na nádobách s rastlinami kukurice v kontrolovaných podmienkach skleníka počas 74 dní. Využitím metódy PCR – DGGE sme skúmali rozdiely v celkovej komunite baktérií ako aj komunite nitrifikačných baktérií. Na základe prítomnosti operatívnych taxonomických jednotiek (OTU) sme zistili rozdiely v spektrách bakteriálnych druhov v závislosti od variantov hnojenia. Najvyšší Shannonov index biodiverzity bol zaznamenaný vo variante s prídavkom VC v dávke 80 t*ha-1. Vplyv hnojenia na diverzitu nitrifikačných baktérií nebol preukazný, avšak v každom variante s prídavkom vermikompostu bol zaznamenaný výskyt nového špecifického OTU. Tento OTU bol identifikovaný ako Nitrosospira sp. Dokázalo sa, že niektoré druhy baktérií dodané do pôdy prídavkom vermikompostu sú schopné prežívať po dobu najmenej 74 dní a môžu ovplyvňovať základné funkcie pôdnej mikrobiocenózy v cykle dusíka

A miragem da miscigenação

Neste artigo abordamos alguns aspectos da natureza da sociedade escravista - na África e no Brasil - especialmente os significados da liberdade, cor, protesto entre os séculos XVII a XIX. Partimos de um diálogo crítico sobre as perspectivas de miscigenação, políticas de domínio e dinâmicas sociais nas sociedades escravistas e os desdobramentos para o seu funcionamento e mudança.<br>This article aims to focus some aspects concerning slave societies in Brazil and in Africa. In special, those related to the meanings of freedom, color, and protest between the eighteenth and nineteenth centuries. These issues are discussed from a critical dialogue on the perspectives about miscegenation, domination politics, social dynamics, and change in the slave societies