Cesar H. B. Miranda

Selection of ecotypes of Panicum maximum for associated biological nitrogen fixation using the 15N isotope dilution technique

Ecotypcs of the tropical pasture grass, Panicum maximum, were screened by means of the 15N isotope dilution technique for their ability to support associated biological nitrogen fixation (BNF). The ecotypes were planted in pots containing 3kg of a purple latosol (allic rhodalf) mixed with 1.5g pot−1 of 15N-labelled organic matter (compost). The experiment consisted of 26 treatments (25 ecotypes and the non-N2-fixing control plant, Brachiaria arrecta, IRI 442) with four replicates and was laid out in a randomized complete-block design. B. arrecta and P. maximum ecotype KK. 16 accumulated more N than most other ecotypes at the first two harvests (high soil N availability), but recovered the least N at the final two harvests (low soil N availability). At the last two harvests these two grasses had the highest 15N enrichment. The uptake pattern of labelled N of ecotype KK 16 was similar to that of the other P. maximum ecotypes, but distinctly different from that of B. arrecta, and for this reason KK16 was considered to be a better control plant and capable of obtaining little or no N from associated BNF. The other P. maximum ecotypes derived between 16 and 39% of their total N from BNF at the final two harvests.

Does phosphorus supply enhance soil-N mineralization in Brazilian pastures?

Two Brachiaria decumbens paddocks on a sandy Entisol soil were compared to investigate whether degradation of tropical pastures may be due to phosphorus deficiency limiting plant growth and/or soil N mineralization processes. Grass dry matter (168 vs. 130 kg ha−1 week−1, wet season) and litter production (130 vs. 86 kg ha−1 week−1) as well as standing root biomass (3744 vs. 1683 kg ha−1, 0-60 cm) were considerably greater in the P fertilized (100 kg P2O5 ha−1) plot. In situ soil N mineralization measurements indicated substantially greater rates of N release under the P fertilized pasture only at the beginning of the dry season. Soil mineral N amounts present during the wet season were greater in the unfertilized plot, presumably due to the smaller N demand of P deficient plants. In a laboratory incubation experiment testing three acidic soils of varying texture, P supply increased the amount of soil-N mineralized with time especially in the more clayey, P-fixing soils. The effect was associated with slight increases in soil pH, probably due to a decrease in charge of (Al- and Fe-) hydroxide complexes. Biomass N was not significantly affected by P supply but biomass efficiency for N mineralization (mineralized N per unit biomass N) increased with P supply in the clayey soils. Our results suggest that in poor tropical sandy soils under grass pastures, the addition of P stimulated plant N uptake primarily by alleviation of plant P deficiency and more efficient N cycling rather than by a direct effect on soil N mineralization.

Determinação da fixação biológica de nitrogênio no amendoim forrageiro (Arachis spp.) por intermédio da abundância natural de 15N

The biological nitrogen fixation (BNF) of five Arachis pintoi (BRA31534, BRA31828, BRA31796, BRA15121 E BRA30333) and two A. repens (BRA31801 e BRA31861) accessions, grown in a Dark Red Latosol prone to seasonal flooding was evaluated using the 15N natural abundance method (d15N). Stolons of each accession were planted in November 1999, in plots of 2.0 m by 2.0 m, with four replications allotted to randomized blocks. Plant mass above five cm was harvested in January 2000. There were significant differences among the tested accessions for dry matter (DM) production and total N content, with BRA31534 and BRA31828 producing 4.2 t/ha of DM, and 102 and 110 kg N/ha respectively. BRA3033 and BRA31861 produced only 2.6 t DM/ha and 59 and 65 kg/ha of total N, respectively. The proportion of N derived from N2 fixation, estimated by comparison of the d15N of Arachis accessions with non N-fixing plants growing in the same area, ranged from 36% (BRA15121) to 90% (BRA31128), equivalent to 26 and 99 kg N/ha, respectively. There was a positive and significant correlation (r = 0.92, p<0.05) between plant total N content and N derived from BNF, but a negative and significant correlation (r = -0.93, p<0.001) was found between plant total N and N derived from soil. It was concluded that plant production by the most promising accessions was the result of an efficient symbiosis with soil Bradyrhizobium native strains, with BNF supplying plant N nutritional requirements.

Carbon and nitrogen mineralization in soils under agro-pastoral systems in subtropical Central Brazil

Abstract Agro-pastoral systems that combine soybean and grasses in crop rotation have been recommended to sustain grassland productivity in the subtropical soils of Central Brazil (Cerrados forest area) with a low-fertility. In 1999, soil samples were taken during a field experiment on agro-pastoral system initiated in 1993 in a Purple Red Latosol in Campo Grande, MS, Brazil, from 1) a field with continuous soybean cropping; 2) a field with soybean cultivation after 4 years of use as a grassland (rotational soybean); 3) continuous grassland; 4) grassland planted after 4 years of soybean cultivation (rotational grassland), 5) degraded grassland; and 6) original Cerrados forest. Total carbon (C) and nitrogen (N) contents and mineralization potentials were determined. The results indicated that replacement of the Cerrados forest by a pure grassland and exploitation without proper cattle management and fertilizer application led to a decrease in both total C and N contents. Continuous cultivation of soybean on such a degraded grassland area induced a further decrease, which could be alleviated by rotation with a grassland. On the other hand, soil C and N mineralization potentials were not appreciably affected, indicating that grassland degradation did not affect these parameters. C and N mineralization showed a seasonal pattern, being higher in the rainy season (November) than in the dry season (April). Overall, it can be concluded that a grass-soybean rotation (agro-pastoral system) may benefit agricultural exploitation in the Brazilian Cerrados area, as both complement each other in maintaining a suitable soil C balance.

Mineral nitrogen in an oxisol from the Brazilian cerrados in the presence of Brachiaria spp.

Abstract The effects of commercial cultivars of Brachiaria decumbens , B. humidicola , and B. brizantha on nitrogen mineralization and nitrification were examined in a Dark Red Latosol from the Cerrados region of Central Brazil. B. decumbens responded most rapidly to the addition of fertilizer N. B. brizantha also absorbed the fertilizer N rapidly but grew more slowly. By contrast, B. humidicola showed a slower response to the fertilizer addition, both in N uptake and growth. The concentrations of mineral N in the soil under both B. decumbens and B. brizantha indicated that most of the fertilizer N remaining in the soil was quickly immobilized, as also indicated by the results of incubated soil samples. On the other hand, the soil under B. humidicola showed strong mineralization of native organic N between three and six days after the addition of N in the presence of the plants, but not during the incubation. In this species there was also a clear indication of early nitrification, whereas in the soil under the other two species the build up of the nitrifier population seemed to be delayed. It is concluded that the species studied had different rates of N uptake and assimilation and stimulated microorganisms differently in their rhizosphere, which lead to contrasting transformations on the soil mineral N pool. The observed patterns of mineralization/immobilization and nitrification changed so quickly that analysis of the effects of plants on soil N transformations based on a few harvests or over long time intervals could be misleading.

Characterization of Nitrogen Utilization by Brachiaria Grasses in Brazilian Savannas (Cerrados)

Brachiaria species are widely cultivated and the low nitrogen (N) fertility of soils is one of the limiting factors for grass production in the Brazilian savannas (Cerrados). In the present study, we compared the characteristics of N utilization in Brachiaria brizantha (BB), B. decumbens (BD), and B. humidicola (BH), which are common species in these areas. In a soil culture experiment, BB, BD, and BH were grown under 3 levels of N, equivalent to 0 application (ON), 0.1 (1N), and 0.3 (2N) g N pot−1, with N as ammonium sulfate. The plant dry weight of BB and BD increased with the increase of N levels, whereas BH showed a weaker growth response to N application and the plant dry weight of BH was lower than that of BB and BD. The amount of N accumulated in plant increased with the increase of N levels in BB and BD. The amount of N accumulated in plant in BH was slightly lower than or almost comparable to that in BB and BD. The plant N concentration was higher in BH than in BB and BD. The stronger growth response of BB and BD resulted in a higher fertilizer use efficiency (FUE) and a N use efficiency in fertilizer application (NUEF). The N absorption efficiency (NAE) of BH was higher than that of the other two grasses for 1N and 2N. In the absence of N treatment (hereafter refferred to as “ON treatment”), the specific N absorption rate in the roots (SAR) was higher in BH than in BB and BD throughout the growth period. These data suggested that the N absorption ability in roots would be higher in BH than in the other 2 tested grasses, as confirmed by the Michaelis-Menten kinetic analysis. In a nitrate absorption experiment, the K m value of BH was lower than that of BB and BD. As BH showed a higher affinity for nitrate absorption, it could maintain a higher N absorption rate. Therefore, it was considered that the performance of N accumulation of BH would be slightly lower than or almost comparable to that of BB and BD because of the high ability of BH to absorb N, although dry matter production of BH was lower than that of BB and BD.

Preparation and characterization of baru (Dipteryx alata Vog) nut protein isolate and comparison of its physicochemical properties with commercial animal and plant protein isolates.

BACKGROUND The Brazilian leguminous tree locally known in the Cerrado Biome as baru (Dipteryx alata Vog), provides a healthy edible oil source. The proteinaceous cake remaining after oil extraction could be transformed into new products to foodstuff development, such as protein concentrates and isolates, adding value to the production chain. In this study, it is described the preparation and characterization of baru nut protein isolate (BPI) from deffated baru flour, and measurements of its functional, nutritional, and thermal properties, in comparison to the more common vegetable (soybeans) and animal (casein and albumin) protein sources of the food industry. RESULTS BPI presented higher protein content than soybean, casein and albumin commercial protein isolates, despite losses of albumins and low molecular weight globulins during the isolation procedure. Thermodynamics studies suggested that BPI has a well-conserved protein arrangement and lower thermostability than the other protein sources. BPI showed high in vitro digestibility and suitable and desirable functional properties such as water and oil absorption capacity, emulsifying activity, and foam formation and stability at mild and neutral pH. CONCLUSION BPI could be used either as a substitute ingredient in oily food formulations or in the development of new products of its own.

COWPEA (VIGNA UNGUICULATA) CROPS IN AFRICA CAN RESPOND TO INOCULATION WITH RHIZOBIUM

Cowpea (Vigna unguiculata L. Walp) is the most important food grain legume in Africa. Cowpea is nodulated by rhizobium bacteria in almost all soils of the tropics, but studies performed in the 1970s and 1980s in Nigeria suggested only modest responses of grain yield in the field to inoculation of selected rhizobium strains. More recently, experiments performed in Brazil have shown that cowpea responded to inoculation of rhizobium selected locally and grain yields increased by up to 30%. We tested some of the Brazilian strains on cowpea at a site in northern Mozambique and at several sites in Northern Ghana. At all sites phosphorus fertilizer (26 kg P ha⁻¹) was added to all plots. At the site in Mozambique despite considerable damage to the crop by the parasitic yellow witchweed (Alectra vogelii), grain yields were more than doubled by inoculation of one of the Brazilian strains and reached 1.4 Mg ha⁻¹. In on-station experiments conducted in 2012 in June and August in northern Ghana using the local cowpea variety Padi-Tuya as the test crop, nodule weight at 35 days after planting (dap) tripled with rhizobium strain BR 3299 (530 mg plant⁻¹) in August with the other inoculants (BR 3267 and a mixture of BR 3267 and BR 3299) also increased nodule weight to over 300 mg plant⁻¹. In the first on-station experiment, grain yields were doubled by the inoculation of any of the three rhizobium strains, and in the second experiment, significant increases in grain yield ranged from 39% to 57% and reached over 2.0 Mg ha⁻¹. Similar increases in nodulation and grain yield due to inoculation were observed in 22 on-farm trials. Nitrogen fertilizer application promoted vegetative growth but did not increase grain yield and nodulation. Inoculating cowpea with highly effective rhizobium strains can therefore enhance grain yield of smallholder farmers in Africa.

Oleaginous Biomass for Biofuels, Biomaterials, and Chemicals

Concerns about negative environmental impacts and questions of future availability surrounding the long-term use of fossil sources as a basis for production of fuels, and a plethora of derivatives, are matters of increasing importance. Consequently, plant biomass sources capable of efficiently replacing fossil fuel resources are gaining relevance as biofuels and in the oleochemical industry. The array of chemical compositions of vegetable oils and fats, the possibility of producing biomass in a sustainable way, and the development of routes for their transformation are the main drivers of this growing demand. This chapter covers topics of global production and consumption of the principal vegetable oil commodities, the comparative chemical composition of oils and fats, the potential use of the biological storage structures of oils and fats, the main processes of transforming oils into biofuels, and the production of bio-based polymers. Also, mechanisms of the functionalization of vegetable oils are stressed.

Macauba ( Acrocomia aculeata ) pulp oil quality is negatively affected by drying fruits at 60 ºC

This study aimed to determine if the quality of macauba pulp oil is affected by drying the whole fruits at 60 oC. Mature fruits were collected at every five days on the ground under 10 palm trees. A mixed batch of 3 kg of whole fruits, with three replications each, was dried in an oven with air circulation for 0, 12, 24, 36 and 48 h at 60 oC. After every drying time, dried fruits were pulped using an automated device, followed by oil extraction with hexane. Moisture and oil content were determined in the pulp, and the pulp oil quality was analyzed for fatty acid composition, free fatty acids content, peroxide value, molar absorptivity at 232 and 270 nm, refractive index, and total carotene content. The tested temperature was sufficient to decrease moisture to a range suitable for automated pulping, with the best combination and easier pulping being reached after 24 h of drying. In the first 12 h there was an apparent synthesis of unsaturated fatty acids and carotenes. The tested temperature was insufficient to avoid the enhancement of acidity since the beginning and throughout the drying period, nor the degradation of polyunsaturated fatty acids. Thus, it is concluded that drying of fresh fruits of macauba palm at 60 oC is not appropriate to obtain an overall good quality pulp oil for industrial purposes.