Mario Andrade Lira Junior

Deposição e acúmulo de matéria seca e nutrientes em serapilheira em um bosque de sabiá (Mimosa caesalpiniifolia Benth.)

n Quantification of litter deposition and organic mantle accumulation are important steps on nutrient cycling studies. This study aimed to quantify litter deposition and organic mantle in a sabiAE (Mimosa caesalpiniifolia Benth) woodlot in an experimental farm in the Brazilian northeast region. Twenty 0.50 x 0.50 x 0.15 m wood collectors, to quantify litter deposition, were systematically distributed over the area elevated 30 cm above the soil. Deposited material was collected monthly from October 2000 to September 2001, and separated into leaves, twigs, flowers, pods and mixed portions. Undecomposed organic mantle was randomly sampled nearby collector boxes, to a total of 20 monthly samples, from which a 0.30 x 0.30 m composed sample was collected. The collected material was also hand separated into leaves, twigs, flowers,

Distribuição de biomassa e nutrientes na parte aérea de Mimosa caesalpiniaefolia Benth

This work was carried out at Itambe Experimental Station, in the State of Pernambuco, Brazil, to study biomass and nutrient distribution in stands of Mimosa caesalpiniaefolia Benth. Two stands with similar soil and topographical conditions were studied, involving plants eight and eleven years old, at 3.0 x 3.0 m and 4.5 x 4.5 m spacing, respectively. The biomass of each tree component was determined. Samples of leaves, branches, bark and stem were collected and chemically analyzed. Total biomass was 66.22 and 80.78 t/ha in stands I and II, respectively. Biomass distribution in stands I and II was: branches (44.99 and 53.40%), wood (51.53 and 44.58%), bark (2.39 and 1.40%) and leaves (1.10 and 0.62%). Nutrients of the components for both stands showed the following concentration trend: Nitrogen > Calcium > Potassium > Magnesium > Sulfur > Phosphorus.

Estoque de serapilheira e fertilidade do solo em pastagem degradada de Brachiaria decumbens após implantação de leguminosas arbustivas e arbóreas forrageiras

Pastures are the fodder supply of Brazilian livestock, and are exhaustively degraded by nitrogen (N) deficiency. Intercropping with legumes, aside from nitrogen fixation, may have secondary effects on soil fertility, such as acidification or nutrient movement from deeper to the surface soil layers. This study evaluated the soil litter stock and fertility of degraded Brachiaria decumbens pastures after planting leguminous shrubs and forage trees. For this purpose, we sampled (March 2010) degraded Brachiaria decumbens pasture planted in July 2008 in an intercropping experiment with sabia (Mimosa caesalpiniaefolia), leucaena (Leucaena leucocephala), mororo (Bauhinia cheilantha) and gliricidia (Gliricidia sepium), as well as N-fertilized and unfertilized brachiaria. Soil and litter was sampled (layers 0-10, 10-20 and 20-40 cm) in three transects, at alternating points covered by grasses and by legumes, totaling seven composite samples per plot to determine soil pH, P, K , Ca, Mg, and Al and calculate sum of bases, effective cation exchange capacity and aluminum saturation. Litter was visually separated in legumes, grasses and unidentified material to quantify dry matter, organic matter, N, P, C, acid-detergent fiber, and lignin. The use of legumes increased the levels of total N in litter and reduced the C: N ratios, especially of gliricidia and sabia, although the lignin levels in the latter were high. There was a significant effect of legume soil cover, with no differences between them, on pH and K (layer 0-10 cm) and on pH, K and Al (layer 10-20 cm).

Symbiotic capability of calopo rhizobia from an agrisoil with different crops in Pernambuco

Biological nitrogen fixation by rhizobium-legume symbiosis represents one of the most important nitrogen sources for plants and depends strongly on the symbiotic efficiency of the rhizobium strain. This study evaluated the symbiotic capacity of rhizobial isolates from calopo (CALOPOGONIUM MUCUNOIDES) taken from an agrisoil under BRACHIARIA DECUMBENS pasture, sabia (MIMOSA CAESALPINIIFOLIA) plantations and Atlantic Forest areas of the Dry Forest Zone of Pernambuco. A total of 1,575 isolates were obtained from 398 groups. A single random isolate of each group was authenticated, in randomized blocks with two replications. Each plant was inoculated with 1 mL of a bacterial broth, containing an estimated population of 108 rhizobial cells mL-1. Forty-five days after inoculation, the plants were harvested, separated into shoots, roots and nodules, oven-dried to constant mass, and weighed. Next, the symbiotic capability was tested with 1.5 kg of an autoclaved sand:vermiculite (1:1) mixture in polyethylene bags. The treatments consisted of 122 authenticated isolates, selected based on the shoot dry matter, five uninoculated controls (treated with 0, 50, 100, 150, or 200 kg ha-1 N) and a control inoculated with SEMIA 6152 (=BR1602), a strain of BRADYRHIZOBIUM JAPONICUM The test was performed as described above. The shoot dry matter of the plants inoculated with the most effective isolates did not differ from that of plants treated with 150 kg ha-1 N. Shoot dry matter was positively correlated with all other variables. The proportion of effective isolates was highest among isolates from SABIA forests. There was great variation in nodule dry weight, as well as in N contents and total N.

Chemical attributes of an Argisoil of the Vale do São Francisco after melon growth with phosphate and potash rocks biofertilizers

Fertilizer application may promote significant changes in soil reaction and on the availability of important nutrients for plants. The utilization of rock biofertilizers is a practical process that reduces energy consumption and increases nutrient availability in soils. In a field experiment, the effect of biofertilizers produced with phosphate and potash rocks plus Acidithiobacillus inoculation were evaluated on the chemical attributes of an Argisoil from the Sao Francisco Valley, Pernambuco State, Brazil, after melon cultivation. The experiment was arranged in a factorial 32+2 scheme in randomized block design, with four replicates. Two sources of P biofertilizer (PB) and K biofertilizer (KB) were applied in the same doses recommended for simple superphosphate (SS) and potassium chloride (KCl), and in doses which corresponded to two and three times the recommended ones. Additional treatments were carried out (soluble fertilizers (SS) and potassium chloride KCl), applied in the recommended dose, and control treatment with no addition of P and K (P0+K0)). Biofertilizers reduced soil pH and higher available P and K values were obtained when higher doses of biofertilizers (PB and KB) were applied. Mg content increased when KB biofertilizers were applied in higher rates, probably due to the solubilization of Mg present in the biotite. The rock biofertilizers with Acidithiobacillus may be recommended as an alternative to soluble fertilizers by the residual effect in nutrient availability, especially in sodic soils or in limed acid soils.

Isolamento e prospecção de bactérias endofíticas e epifíticas na cana-de-açúcar em áreas com e sem cupinicida

The exploration and knowledge of bacteria-plant interaction mechanisms may be used for a more sustainable production of several crops, e.g., of sugarcane. The objective of this paper was to isolate bacteria associated with sugarcane with the ability to fix nitrogen and solubilize inorganic phosphate in areas with and without the application of termiticide. Endophytic bacteria were isolated from leaves and roots and from the rhizoplane, four months after planting of three commercial sugarcane varieties (RB 92579, RB 867515 and RB 863129), in the Northeast of Brazil. Altogether, 272 isolates were obtained and selected for their capacity to solubilize inorganic phosphate and fix nitrogen. Termiticide application induced no changes in the endophytic microbial communities of leaf and root and the epiphytic bacteria of the rhizoplane. A bacterial community associated with the studied sugarcane varieties was identified, which could be applied for plant growth promotion, since it can fix N2 and solubilize inorganic phosphate.

Azospirillum sp. as a Challenge for Agriculture

Several processes mediated by soil microorganisms play an important role in nutrient cycling. One such process is biological nitrogen fixation (BNF) by representatives of various bacterial phylogenetic groups, which are called diazotrophs. Most studies of the Azospirillum-plant association have been conducted on cereals and grasses. Currently, 17 species of Azospirillum have been described. However, a great diversity of these bacteria continues to be revealed, and little is known of the potential applications of the many species that have been described. The Azospirillum-plant association begins with the adsorption and adherence process of these bacteria in roots. Involved in these processes is the recognition of bacterial polysaccharides by the host plant, a step that is necessary in successfully forming a positive relationship between roots and Azospirillum. The presence of Azospirillum in the rhizosphere can minimize the susceptibility to diseases caused by plant pathogens. Furthermore, the ability to produce phytohormones, mainly auxins (indole-3-acetic acid) and other molecules from secondary metabolism has been suggested to underlie the growth response to inoculation by Azospirillum species. These positive aspects of Azospirillum colonization in the roots are also responsible for the alleviation of plant stress. For all of the above-mentioned reasons, Azospirillum are also widely used as commercial inoculants, resulting in a significant economic impact in crop yields in many countries. In fact, solid and liquid formulations containing Azospirillum are marketed in various countries, such as Brazil, Argentina, Mexico, Italy, France, Belgium, Africa, Germany, Pakistan, Uruguay, India and the USA. In addition, new formulations containing Azospirillum, such as polymeric inoculants (alginate, agar, chitosan and gum), are already used for the improvement of many crops. This chapter summarizes the positive effects of Azospirillum-plant interactions and their biological importance for the improvement of agriculture worldwide.

Feasibility of rhizobia conservation by liquid conditioners

This paper evaluates the possible use of liquid preservation methods for rhizobia long term conservation under ambient temperature conditions. Saline solution (sterile distilled water + NaCl), glycerol and carboxymethycellulose (CMC) were evaluated for preservation of Rhizobium tropici and Bradyrhizobium japonicum cultures up to 180 days and regarding their capacity to promote common bean (Phaseolus vulgaris (L.)) and soybean (Glycine max (L.)) nodulation. The total population was determined after 0; 1; 7; 15; 21; 30; 60; 90; 120; 150 and 180 days of conservation and conserved bacteria were evaluated for symbiotic characteristics after 15, 60 and 120 days of conservation. Although there were significant species x conservation method interactions, both saline solution and CMC may be used for short storage terms, allowing the production of inoculant for field experiments, and its test for purity and concentration before field establishment. The utilized techniques have low cost and easier usage as inoculants, compared to the traditional turf-based products, and if determined feasible by further research it could be a low cost addition to the standard microbiological techniques, particularly as working culture preservation media.

Biological Nitrogen Fixation: Importance, Associated Diversity, and Estimates

Several processes mediated by soil microorganisms play an important role in nutrient cycling. One such process is biological nitrogen fixation (BNF) by representatives of various bacterial phylogenetic groups, which are called diazotrophs. These bacteria can be free-living, associate with plant species, or even establish symbiosis with legumes. Studies with diazotrophic organisms are of great importance due to their contribution to the nitrogen supply in different ecosystems, including natural and managed systems. It is estimated that global BNF adds 122 Tg of N yearly with cultivated agricultural systems fixing from 33 to 43 Tg, which occurs mostly by legume-rhizobia symbiosis. There is a large potential of BNF contribution by associative systems with tropical grasses, but there is uncertainty in these estimates due to several assumptions in the estimation process and fewer studies with this system when compared to the legume-rhizobia symbiosis. Recent progress in the understanding of diversity, colonization ability, action mechanisms, formulation, and application of these biological systems should facilitate their development as reliable components in the management of sustainable agricultural systems. Several efforts have been made to develop commercial inoculants using these organisms. The current progress in using microorganisms that fix nitrogen in a variety of applications is summarized and discussed herein.

Efeito da fertilização fosfatada na produção de raízes, liteira e nodulação de Mimosa caesalpiniifolia benth

This work aimed to evaluate the effect of phosphorus fertilization on nodulation, litter deposition and root system development of M. caesalpiniifolia Benth, before and after pruning, at the Itambe Experimental Station of Pernambuco Agronomical Institute - IPA in Pernambuco, Brazil. Treatments were levels of phosphorus fertilization (0, 100 and 200 kg.ha-1 of P2O5) arranged in a randomized block design with six replicates in block I and seven in block II, with the criterion for block formation being uniformization cut date. Samplings were taken before and after pruning of the aerial part Root length and root, nodule and litter dry matter had similar results before and after pruning. Nodule numbers before pruning were 2, 15 and 6 for 0, 100 and 200 kg.ha-1 of P2O5, respectively, and 1, 6 and 7 after pruning. Average root lengths ranged from 552 to 734 cm before and from 389 to 455 cm after pruning. The number of nodules presented variation only from August to November 2005, with values from 2 to 15 and from 1 to 7 nodules, before and after pruning, respectively.