Igor Rodrigues de Assis

Microalgae biofilm in soil: Greenhouse gas emissions, ammonia volatilization and plant growth

Microalgal biofilm in soils represents an alternative fertilization method for agricultural sustainability. In the present study, greenhouse gas emission, soil ammonia volatilization, and the growth of Pennisetum glaucum were evaluated under the effect of a microalgal biofilm, commercial urea, and a control (without application of a nitrogen source). CH4 emissions were equal for the three treatments (p>0.05). CO2 emissions significantly increased in microalgal biofilm treatment (p<0.01), which was also responsible for the highest N2O emissions (p<0.01). The ammonia (NNH3) volatilization losses were 4.63%, 18.98%, and 0.82% for the microalgal biofilm, urea, and control treatments, respectively. The main differences in soil characteristics were an increase in nitrogen and an increase in cation exchange capacity (p<0.01) caused by the algal biomass application to the soil. The soil organic matter content significantly differed (p<0.05) among the three treatments, with the microalgal biofilm treatment having the greatest increase in soil organic matter. Significant differences were observed for shoot dry matter mass and nitrogen content in the plants from both treatments where nitrogen sources were applied. All treatments differed from each other in leaf dry matter mass, with the urea treatment increasing the most. Chlorella vulgaris was the dominant microalgal specie in the soil.

Cover layers to the growth of trees and shrobs over a sulfide spoil from gold mining

This work was done at a gold mine company in Paracatu, MG, Brazil, and was conducted from March 2000 to November 2005. The substrate (spoil) studied was a phillite rock which contains sulfides such as pyrite and arsenopyrite. This study aimed to evaluate the survival and growth of plant species on different combinations of substrate layers over the spoil. These layers were a cover layer and a sealing layer, both deposited over the spoil. The treatment 1 had saprolite (B1) in the sealing layer (SL) and B1 with liming (B1L) in the cover layer (CL). The treatment 2 had B1 in SL and B1L + soil with liming (SoL) in the CL. The treatment 3 had B1 + SoL in the SL and B1L in the CL. The treatment 4 had B1 + SoL in the SL and B1L + SoL in the CL. The plant species used were Acacia farnesiana, A. holosericea, A. polyphylla, Albizia lebbeck, Clitoria fairchildiana, Flemingia sp., Mimosa artemisiana, M. bimucronata e Enterolobium contortisiliquum. Forty and 57 months after planting, collardiameter, height, and living plants were evaluated. The greatest survival rate was oobservedintreatmentwith B horizon of an Oxisoil in both layers, with 80 %. In general, M. bimucronata and A. farnesiana species showed the highest survival rate. The arsenic-content by Mehlich 3 in the cover layer ranged from 0.00 to 14.69 mg dm -3 among treatments. The experimental results suggest that layers combinations above the sulfide substrate allow the rapid revegetation of the spoil.

Níveis críticos foliares de nutrientes de três cultivares de batata-doce, selecionados para a produção de etanol

Foliar nutrient critical levels in three cultivars of sweet potato selected for ethanol production In the past 12 years, research undertaken at Tocantins State, Brazil, resulted in ten new sweet potato cultivars with high starch content, suitable for ethanol production. However , little is known about their nutritional requirements and nutrient content. Thus, this study aimed to evaluate the uptake and exportation of nutrients and determine the leaf critical levels of N, P and K for the sweet potato cultivars ‘Amanda’, ‘Carolina Victoria’ and ‘Duda’, due to different doses of N, P and K applied to soil. The experiment comprised 33 treatments arranged in a completely randomized block design with four replications. Foliar concentrations of N, S, Cu and Zn varied among cultivars, while P and K varied due to P 2 O 5 and K 2 O levels, respectively. The N, P and K content in storage roots varied significantly depending on the doses of these nutrients in the soil, where K is the nutrient that has accumulated in greater quantity , followed by N, and this one by Ca, P, Mg and S, which accumulated amounts were about 10 times lower than the observed for N. According

REVEGETATION OF ACID FORMING MINE SPOILS IN PARACATU, MINAS GERAIS STATE, BRAZIL 1

Paracatu is located in northwest Minas Gerais State, 230 kilometers from Brasilia, the capital of Brazil, and for the last two centuries has been an important gold mining site. With more of 600 ha of acid-sulfate soils across the open cut mine to be revegetated, the company is working to develop a method to reliably establish sustainable vegetation and minimize acid drainage. With this goal, we established a field experiment to evaluate five soil placement combinations to isolate (saddle) and/or cover the acid substrate. We also evaluated five plant species and three combinations to revegetate the materials. The five cover treatments were composed of three layers to: 1) isolate/saddle the substrate; 2) break capillarity and, 3) form a suitable surface material for plant growth. Ore (from mining zone B1) or clay was used as the saddle layer and sand, lime gravel, and sand plus oxalic acid were tested as capillary barriers. Then KCl and NaCl were also added to induce jarosite formation (geochemical barrier) to reduce availability of Fe and As in the drainage. As a cover layer, we tested B1 and local B horizon clay. Each (3) experimental block was comprised of five plots (to test the layers materials) with eight split sub-plots to evaluate the species and combinations. Ten months after establishment, we took samples of the layers to evaluate density and porosity, and the revegetation species were sown. Preliminary results showed that the saddle layer with clay resulted in higher density/less porosity. Non-compacted clay, when used to form the third layer, had higher water retention than B1 ore. This characteristic is very important to reduce water movement into underlying acid-sulfate materials. Among the evaluated species, Crotalaria juncea performed best followed by Melinis minutiflora. For most tested plant species and mixtures, the use of clay as the first and third layer coupled with sand plus KCl and NaCl as the capillary barrier resulted in optimal biomass production.

Use of PVC pipes to determine bulk density for irrigation management

Irrigation has a great importance in the production of food, and it is responsible for consuming a large part of the water used by human activities. This makes the rational management of water use fundamental for sustainable food production. For this purpose, the determination of bulk density is important and needs to be obtained with the simplest, least onerous methods possible, while maintaining precision and accuracy. Therefore, the objective of this work was to evaluate the use of PVC pipes of different dimensions to determine bulk density. For comparison purposes, the volumetric ring, paraffin clod, beaker and excavation methods were also used. Deformed and undisturbed soil samples of different granulometries were collected at the depths of 0.025-0.075, 0.050-0.100, 0.075-0.125 and 0.100-0.150 m. The PVC pipes had diameters of 0.040, 0.050, 0.060 and 0.075 m and heights of 0.10, 0.15, 0.20 and 0.25 m. The bulk density results for each PVC pipe dimension were compared with those of the traditional methods by the unpaired t-test at 5% significance. For soils with a clayey or very clayey texture, the 0.040 m diameter and 0.15 m high PVC pipe presented the best results, with values closer to those of the standard method. For soils with a medium and sandy texture, the best results were found when a PVC pipe with a diameter of 0.060 m and a height of 0.15 m was used.

Physical quality of bauxite tailing after a decade of environmental recovery

Tailings from bauxite washing produced in Porto Trombetas, Para state, a Brazilian Amazon region, have chemical and physical characteristics limiting the development of plants, which hinders to revegetate the tanks where they are deposited. This study was carried out under field conditions, and aimed to assess the physical quality of these tailings after a decade of recovery practices. Three treatments were assessed: no application of inputs and planting of seedlings (T1) and two levels of fertilization, one with lower (T2) and other with higher (T3) doses of limestone and fertilizers associated with planting tree seedlings. After ten years of experimentation, penetration resistance (PR) and substrate moisture up to 60 cm depth were assessed and the least limiting water range (LLWR), water retention curve (WRC), and pore size distribution were determined and calculated. After a decade of environmental recovery, differences in physical characteristics were observed in the tailings due to different revegetation modes. Moisture in the substrate profile, LLWR, WRC, and pore size distribution were sensitive indicators to variations in substrate physical quality. Liming, fertilization, and planting of seedlings are necessary for revegetation and improvement of the physical quality of tailings. Treatment T3 was the best intervention identified so far for tank revegetation. The absence of fertilization and planting precludes revegetation even with sources of propagules nearby.

Apparent soil electrical conductivity in two different soil types

Mapping the apparent soil electrical conductivity (EC a ) has become important for the characterization of the soil variability in precision agriculture systems. The problem regarding the use of this soil attribute is that EC a occurs due to the interaction of a large number of factors, difficulting interpret the causes of its variability. The objective of this work was to examine the relations between EC a and soil attributes in two fields presenting different soil textures. In each field, 50 sampling points were chosen using a path that presented a high variability of EC a obtained from a preliminary EC a map. At each sampling point, the EC a was measured in soil depths of 0-20, 0-40 and 0-60 cm. In addition, at each point, soil samples were collected for the determination of physical and chemical attributes in the laboratory. The EC a data obtained for different soil depths was very similar. A large number of significant correlations between EC a and the soil attributes were found. In one of the fields, there was no correlation between EC a and organic matter or between EC a and soil clay and sand content. However, a significant positive correlation was shown for the remaining phosphorus. In the other field the EC a had a significant positive correlation with clay content and a significant negative correlation with sand content. The results suggest that the mapping of apparent soil electrical conductivity does not replace traditional soil sampling, however, it can be used as information to delimit regions in a field that have similar soil attributes.

LEAF RESIDUE DECOMPOSITION OF SELECTED ATLANTIC FOREST TREE SPECIES

1 Received on 19.10.2015 accepted for publication on 14.08.2017. 2 Universidade Federal de Viçosa, Mestrado em Agronomia, Viçosa, Minas Gerais, Brasil. E-mail: <helgadias@yahoo.com>. 3 Universidade Federal de Viçosa, Departamento de Solos, Viçosa, Minas Gerais, Brasil. E-mail: <ledias@ufv.br>, <igor.assis@ufv.br>, <julio_n2003@yahoo.com.br>, <nfbarros@ufv.br> and <carlos.schaefer@ufv.br> *Corresponding author.

Morpho-physiological characteristics by sweet potato cultivars as function of irrigation depth

The sweet potato is an alternative energy source, but its sustainability depends on efficient water use. The objective of this study was to evaluate sweet potato morpho-physiological characteristics, and water use efficiency (WUE). Irrigation depths of 50, 75, 100, and 125% of crop evapotranspiration (ETc) were applied. The morpho-physiological indicators, WUE, leaf area index (LAI), leaf water potential, leaf temperature, and leaf chlorophyll index (ICF), were evaluated. The WUE of the sweet potato cultivars increased until the 75% water depth of the ETc. The LAI of these cultivars increased with irrigation depth, with higher values at 100% of the ETc. The leaf water potential of the two sweet potato cultivars was lowest with the lower irrigation depth. Leaf temperature was closer to that of ambient temperatures in treatments with greater irrigation depth. The increase of the WUE with the greater accumulation of dry biomass is due to greater CO2 diffusion by stomata. The reduction in the growth of these plants is due to water stress limiting stomatal conductance, transpiration, leaf growth (LAI) and chlorophyll concentration, proportional to soil moisture conditions. The functional relationship between soil moisture and growth is essential to optimize irrigation management at different growth stages.

Least limiting water range of Udox soil under degraded pastures on different sun-exposed faces

Abstract The efficient use of water is increasingly important and proper soil management, within the specificities of each region of the country, allows achieving greater efficiency. The South and Caparaó regions of Espírito Santo, Brazil are characterized by relief of ‘hill seas’ with differences in the degree of pasture degradation due to sun exposure. The objective of this study was to evaluate the least limiting water range in Udox soil under degraded pastures with two faces of exposure to the sun and three pedoenvironments. In each pedoenvironment, namely Alegre, Celina, and Café, two areas were selected, one with exposure on the North/West face and the other on the South/East face. In each of these areas, undisturbed soil samples were collected at 0-10 cm depth to determine the least limiting water range. The exposed face of the pasture that received the highest solar incidence (North/West) presented the lowest values in least limiting water range. The least limiting water range proved to be a physical quality indicator for Udox soil under degraded pastures.