Diego Lang Burak

Phytomass production and nutrient accumulation by green manure species

Green manuring is recognized as a viable alternative to improve nutrient cycling in soils. The aim of this study was to evaluate the phytomass production and nutrient accumulation in shoots of the summer green manures jack bean [Canavalia ensiformis (L.) DC.], dwarf pigeon pea (Cajanus cajanvar var. Flavus DC.), dwarf mucuna [Mucuna deeringiana (Bort) Merr] and sunn hemp (Crotalaria juncea L.), under nitrogen fertilization and/or inoculation with N-fixing bacteria. A split plot design was arranged with the four Fabaceae species as main plots and nitrogen fertilization (with and without) and inoculation with diazotrophic bacteria (with and without) as the subplots, in a 2 2 factorial. The experiment was arranged as a randomized complete block design with four replications. In the conditions of this trial, the sunn hemp had the highest production of shoot phytomass (12.4 Mg ha -1 ) and nutrient accumulation, while the dwarf mucuna had the lowest production of shoot phytomass (3.9 Mg ha -1 ) and nutrient accumulation. The results showed no effect of nitrogen fertilization or inoculation with N-fixing bacteria on the production of shoot phytomass and nutrient accumulation, except for inoculation without nitrogen fertilization, resulting in greater P accumulation (p <0.05) in the sunn hemp and greater Zn and Mn accumulation in the dwarf mucuna. These findings indicate that N fertilization or inoculation with N2-fixing bacteria for Fabaceae are low efficiency practices in the edaphoclimatic conditions of this study.

Variabilidade espacial de atributos químicos do solo sob cafeeiro Conilon: relação com textura, matéria orgânica e relevo

Chemical properties are related to other soil attributes, including geomorphology, and constitute one of the factors that control spatial variability. The objective of this work was to evaluate the variability of soil chemistry and how it is interrelated with granulometric size fractions and organic soil components. Geostatistics and Principal Component Analysis (PCA) were used to describe the influence of topography. Spatial variability was more influenced by topography at lower depths. The PCA technique showed that attributes associated with soil reactions (pH, Ca, Mg, Al, V and m) contributed to the first prin cipal component (PC1) at the two studied depths. Only PC1 at the 0.0–0.1 m depth was, however, correlated to topography; higher altitudes and smaller slopes favored higher clay content and lower coarse sand proportion, thus resulting in increased retention of cations in the soil. The humic substances of organic matter have low influence on the variability of the chemical attributes, with the exception of Ca and Mg that are well related to humic acids in sites that are richer in sand. Homogeneous areas correlated with geomorphologic attributes was been describe for the K concentrations compared to other attributes at both depths. Thus, the use of spatial analysis for landscape stratification in homogeneous regions for the purpose of fertilizer management depends not only on topography, but on the chemical attributes evaluated and on sample depth.

Visual assessment of pasture degradation: validation by ground cover and seasonal variation

Visual assessments of pasture degradation levels are widespread because they are rapid, practical and inexpensive. However, they can be subjective, making it difficult to distinguish between degradation levels to establish management practices. This fact, in association with the lack of standardization of the number of levels and the assessment periods, suggests a need for further studies. The objective of this study was to evaluate the relation between the degradation levels of visually evaluated pastures and the soil cover measured in fields in summer and winter. Percentages of Brachiaria grass, bare soil, spontaneous vegetation (broad and narrow leaf) and mulch were evaluated in 35 areas with different levels of visual degradation. Canonical discriminant analysis showed that a reduction in the visually assessed degradation level correlates better with the field-measured soil cover in summer. Visual distinctions between the degradation levels were difficult by the visual ambiguity between spontaneous vegetation and pasture in both assessment periods and the visual ambiguity between bare soil and mulch in winter. Visual assessments of pasture degradation should be standardized in the summer period and simplified to two degradation levels, making them more accurate and better related to the vegetation cover measured directly on the field.

Biomassa e o teor de nutrientes em diferentes compartimentos acima do solo de Mimosa velloziana Mart e Tephrosia candida D.C.

A Recuperacao de uma area consiste em torna-la novamente produtiva, seja para fins de conservacao ou producao. E necessario assim, gerar conhecimento sobre tecnicas para adequar procedimentos e tecnicas para esta finalidade. Diante disso, este estudo teve por objetivo avaliar a biomassa e o teor de nutrientes em diferentes compartimentos acima do solo em duas especies de leguminosas ( Mimosa velloziana Mart e Tephrosia candida D.C.) e uma Floresta de Tabuleiros. As leguminosas e a Floresta de Tabuleiro estao estabelecidas sob Argissolo Amarelo Distrocoeso em Linhares, ES. A biomassa acima do solo das leguminosas foi compartimentalizada em: folhas, ramos e ramos secos para Mimosa e folhas, galhos com diâmetro superior e inferior a 2 cm, e galhos secos, para a Tefrosia. Avaliou-se ainda a serapilheira acumulada nas leguminosas e na Floresta de Tabuleiros e seus nutrientes, na estacao chuvosa e seca. Verificou-se que a Tefrosia apresentou a maior producao de biomassa acima do solo, sendo compartimentalizado nas folhas, os maiores teores de nutrientes. A biomassa da serapilheira acumulada nao foi influenciada pelas estacoes de seca e chuva, sendo encontrado maior valor na area com Mimosa. O nitrogenio foi o nutriente com maior teor na serapilheira, seguido por calcio > magnesio > potassio > fosforo > manganes > boro > zinco > cobre.