Alexander Silva de Resende

Nitrogen-fixing legume tree species for the reclamation of severely degraded lands in Brazil.

The main challenges faced in the reclamation of severely degraded lands are in the management of the systems and finding plant species that will grow under the harsh conditions common in degraded soils. This is especially important in extremely adverse situations found in some substrates from mining activities or soils that have lost their upper horizons. Under these conditions, recolonization of the area by native vegetation through natural succession processes may be extremely limited. Once the main physical and chemical factors restrictive to plant growth are corrected or attenuated, the introduction of leguminous trees able to form symbioses with nodulating N₂-fixing bacteria and arbuscular mycorrhizal fungi constitutes an efficient strategy to accelerate soil reclamation and initiate natural succession. These symbioses give the legume species a superior capacity to grow quickly in poor substrates and to withstand the harsh conditions presented in degraded soils. In this article we describe several successful results in Brazil using N₂-fixing legume tree species for reclamation of areas degraded by soil erosion, construction and mining activities, emphasizing the potential of the technique to recover soil organic matter levels and restore ecosystem biodiversity and other environmental functions.

Soil carbon and nitrogen in pasture soil reforested with eucalyptus and guachapele

Apesar de os teores de materia orgânica serem normalmente baixos em solos arenosos, ela e responsavel por quase a totalidade da CTC, armazenamento de agua e disponibilidade de nutrientes desses solos. A avaliacao de sistemas de exploracao florestais alternativos, com vistas em incrementar a acumulacao de C e N, devem ser incentivados. Este estudo compara plantios puros e mistos de Eucalyptus grandis e Pseudosamanea guachapele, leguminosa fixadora de N2, em relacao os estoques de C e N do solo. Os plantios foram realizados em areas anteriormente manejadas com Panicum maximum num Planossolo, que, por pelo menos dez anos, nao recebeu qualquer fertilizante. Para estimar o C e o N estocado, foram retiradas amostras das camadas de 0-2,5; 2,5-5,0; 5,0-7,5; 7,5-10,0; 10,0-20,0 e 20,0-40,0 cm tanto nos plantios puros e mistos, quanto na area de pasto. A tecnica da abundância natural do 13C foi utilizada na estimativa do C originado das arvores nos 10 cm superficiais. Os estoques de C e N, no plantio misto atingiu valores de 23,83 e 1,74 Mg ha-1, respectivamente. Nos puros, de guachapele e eucalipto, e no pasto os estoques de C estimados foram de 14,20; 17,19 e 24,24 Mg ha-1, respectivamente. Para os mesmos tratamentos, os estoques de N foram estimados em 0,83; 0,99 e 1,71 Mg ha-1, respectivamente. Mais de 40 % do C do solo sob o plantio misto foram estimados como sendo derivados das arvores, enquanto nos plantios puros de eucalipto e guachapele, a contribuicao do C das arvores ficou em 19 e 27 %, respectivamente. Esses resultados evidenciam que a presenca da leguminosa no plantio consorciado aumenta os estoques de C e N do solo.

Efeito da queima da palhada da cana-de-açúcar e de aplicações de vinhaça e adubo nitrogenado em características tecnológicas da cultura

Practices of pre-harvest burning and the application of vinasse and N fertilizer are common in sugarcane cultivation. However, results of few long-term studies have been published. This study carried in sugarcane plantations of Cruangi sugar mill, Timbauba, state of Pernambuco, Brazil, located in the semi-arid-wet transition region of the State aimed at studying the effects of vinasse (80 m3 ha-1) and nitrogen fertilizer (N - 80 kg ha-1) and two harvesting systems (with or without pre-harvest burning) on sugarcane yield and industrial parameters in a long-term study (1983 to 1999). The experiment was set up in a 2 x 2 x 2 factorial design in complete randomized blocks with four replicates and had two phases (1983 - 1992 and 1992 - 1999). Nitrogen application negatively affected the technical characteristics of sugarcane, although the yield gain proportioned by this practice favoured the overall sugar yield and compensated the such negative effects. The application of vinasse and the maintenance of cane trash in the system had no consistent effect on the industrial sugarcane parameters, although once again there was an overall gain in sugar production due to the higher yields.

Chemical composition and decomposition rate of plants used as green manure

Productive systems in which green manure is the source of nutrients must develop more efficient ways to improve soil nutrient dynamics. A well-synchronized balance must be established between specific crop demands and supply of nutrients from decomposition. However, scientific data and information to help improve green manure management in Brazil is still insufficient. For that reason, a number of arboreal species was first chemically characterized and then subjected to decomposition analysis in order to establish a correlation between some parameters. Species were grouped together based on the similarity of chemical composition and decomposition rate. The lignin:N and (lignin+polyphenol):N ratios were found to have the greatest correlation coefficient with the dry matter decomposition rate and nitrogen release.

Rapid and sensitive determination of nitrate in plant tissue using flow injection analysis.

Abstract The determination of nitrate in waters and soil extracts by the reduction of nitrate to nitrite by metallic or liquid reductants followed by the colorimetric determination of NO2 ‐using the Griess‐Ilosvay reaction has been automated for use with air‐segmented auto‐analyzers or flow injection techniques. However, this technique is not applicable to plant extracts as organic species in the extracts inactivate the reduction columns. The objective of this study was to develop an automated procedure that would allow the determination of NO3 ‐in plant extracts without the necessity of prior manual treatment. A flow injection technique was developed that successively traps and releases NO3in an anion exchange column thereby removing pigments and other non‐ionic and cationic species that otherwise interfere with conversion of NO3 ‐ to NO2 ‐on a copperized cadmium column. This reduction step is subsequently followed by standard Griess‐Ilosvay colorimetric detection of this ion at a wavelength of 530 nm. The technique uses relatively simple and inexpensive equipment, principally a spectrophotometer equipped with a flow‐through cell and a pen recorder output, a 6‐channel peristaltic pump with accompanying tubing and a Perspex injector/commutator valve made in a laboratory workshop. The technique was found to avoid any significant interference of pigments or other organic compounds in the plant extracts, and the results compared favorably with those obtained using the manual transnitration technique. Analysis time was approximately 1.5 min per sample and could detect NO3’ concentration as low as 0.1 ug NO3’‐N ml/1 in plant extracts (10 ug NO3’‐N g‘1of plant material).

Estimation of N2 fixation in Desmodium ovalifolium from the relative ureide abundance of stem solutes: Comparison with the 15N-dilution and an in situ soil core technique

Many, but not all, legumes of tropical origin, transport fixed N from the nodules to the shoot tissue in the form of ureides, and the mineral N absorbed from the soil is principally transported in the form of nitrate. The analysis of stem xylem sap, or hot-water extracts of stem tissue, for ureide and nitrate has been used successfully to quantify BNF contributions to several grain legumes and more recently to some shrub and forage legumes. The objective of this study was to investigate the application of this technique to the quantification of the contribution of BNF to the forage legume Desmodium ovalifolium by comparing the relative ureide abundance (RUA) of stem extracts of this plant with simultaneous estimates of BNF obtained using the 15N isotope dilution technique. The first experiment was performed in pots of soil, taken from a grazing study, amended with 15N-labelled organic matter at four different application rates. The ureide concentration in the stem extracts reflected the changes in BNF activity during plant growth and the RUA was closely correlated with the proportion of N derived from BNF as determined from the 15N technique (r2 = 0.86 and 0.88 for inoculated and non-inoculated plants, respectively). The use of a calibration curve derived from a previous study where the same legume was fed increasing concentrations of 15N labelled nitrate in sand/vermiculite culture, resulted in an over-estimation of the BNF contribution which may have been due to a significant uptake of ammonium from this acidic soil. The second experiment was performed in field plots and a good agreement was found between the estimates of BNF derived from using the ureide and 15N dilution techniques at two harvests six months apart. The uptake of soil N by the D. ovalifoliumand two forage grasses (Brachiaria humidicola and Panicum maximum) was estimated using an in situ soil core technique, and, while the uptake of N by the grasses was successfully estimated, this technique underestimated the N derived from the soil by the legume as determined by the ureide and 15N dilution techniques.

FAUNA EDÁFICA COMO BIOINDICADORA DA RECUPERAÇÃO DE ÁREAS DEGRADADAS NO BIOMA CAATINGA

Information on the recovering of areas of gravel extraction of the Caatinga biome are scarce. Thus, the objective of this work was to assess the soil fauna as bioindicator of soil quality, evaluating areas with addition of topsoil (WAT) and control areas (CWT) without the addition of topsoil used for forest plantations, which were implemented for recovering gravel extraction areas. A native forest of the Caatinga biome (NFC) was taken as a reference. Ten traps with three replicates were installed in each area, which were evaluated in a randomized block design in split-plot arrangement at the end of the rainy season of different years, 0, 1, 3 and 6 years after the experiment implementation. A total of 45,740 specimens were captured. These specimens were from 36 taxonomic groups. The Acari, Diptera, Entomobryomorpha, Formicidae, Poduromorpha and Symphypleona were the predominant groups in all areas (WAT, CWT and NFC). Nine groups (25% of the total) had restricted occurrence. The fauna richness and diversity were higher in the NFC, followed by the WAT and CWT. The uniformity and total abundance of the soil fauna community showed no defined patterns. The abundance of most groups was inhibited in the treatments evaluated, compared with NFC, however, this adverse effect was more significant in CWT compared with WAT. The CWT and WAT had high similarity and both had very low similarity with NFC. The ecological complexity of soil fauna community was higher in NFC. The soil fauna was efficient as a bioindicator of soil quality, which was higher in WAT, compared with CWT.

DECOMPOSIÇÃO DAS PODAS DAS LEGUMINOSAS ARBÓREAS Gliricidia sepium E Acacia angustissima EM UM SISTEMA AGROFLORESTAL

The Agroforestry Systems (SAFs) bring multiple benefits and they are an alternative to minimize environmental degradation, and to achieve a sustainable development, due to greatest diversity of species. This study evaluated the contribution of the leguminous trees, gliricidia sepium and Acacia angustissima , grown in alley cropping of banana ( Musa sp.) and “acai” palm ( Euterpe oleraceae ) used as green manure in the implantation of an Agroforestry Systems. They were compared the production of biomass, nutrients cycling, nitrogen intake, activity and diversity of soil fauna, and banana productivity in the SAF, and with the usage of the legume Pueraria phaseoloides and nitrogen fertilization. The SAF implantation occurred in May 2004, at the Research Center of Embrapa Agrobiologia, in Seropedica, Rio de Janeiro State. The following year it was planted the forest African mahogany specie ( Kaya senegalensis ), at the centre of the legumes alleys. The experimental design was of randomized blocks with five treatments and four repetitions. The treatments consisted of the leguminous trees arranged between the lines of bananas and the “acai” palm, and they were: acacia angustissima ( Acacia angustissima ), tropical kudzu ( Pueraria phaseoloides ), and gliricidia (G liricidia sepium ); besides application of nitrogen as urea and spontaneous vegetation. To quantify the production of biomass, and the release of N, P, Ca, Mg and K, the legumes branches were cut and the kudzu tropical and spontaneous vegetation were mowed, in the rainy and dry seasons. The determination of remaining dry matter, releasing of nutrients, decomposition rates, and half life time of plant residues were held to 50 grams of fresh material from litterbags, placed on the soil surface, sampled at 0, 5, 10, 15, 20, 25, 30, 40, 60 and 75 days after the installation of the experiment. Acacia angustissima and kudzu tropical showed higher dry biomass, 9.5 and 10.8 Mg ha -1 , respectively. The gliricidia residues showed the highest decomposition rates, in the two year seasons.

Use of Cardboard Disks for Crowning Seedlings in Reforestation

The present study aimed to evaluate the effect of chemopreventive or water-repellent substances on the durability of cardboard disks used to crown forest tree species. The experiment presented a randomized block design with four repetitions and four sampling times (63, 133, 260 and 365 days) and was installed in Seropedica, RJ, in an area with Urochloa humidicola. Bamboo poles were used to simulate seedlings in the field and define the position of the experimental units. The treatments consisted of in natura cardboard, or treated with CuSO4 solution, pinus shellac, CuSO4 + pinus shellac, CuSO4 + Sika , pinus shellac + Sika, and a second control with manual crowning. The cardboard crowning was effective at suppressing grass growth over all periods evaluated, independent of the treatment. After a year in the field, the cardboard disks treated with CuSO4 solution presented higher physical integrity with only 25% mass loss, against 60% mass loss in the control. The cardboard crowning also reduced soil temperature at the crown area by up to 15 °C in the 0 to 10 cm layer, in comparison with manual crowning. The results of this study indicate that the cardboard crowning method is efficient and has the potential to reduce the cost of weed control in reforestation.