Semi-arid Northeast Brazil Research Articles

Genetic control of cowpea seed sizes

Cowpea [Vigna unguiculata (L.) Walp.] is one of the most widely adapted grain legumes in hot regions of Africa, Asia and the Americas. In the semiarid Northeast of Brazil, it is the main subsistence crop, an excellent protein source of low cost, for the poor population. The objective of this work was to estimate genetic parameters to understand the inheritance of seed sizes in cowpea. The parents P1 and P2 and the generations, F1, F2, BC1 and BC2 of the cross TVx5058-09C X Manteiguinha formed the genetic material for this study. These six generates (P1, P2, F1, F2, BC1 and BC) were evaluated in a completely randomized block-design with six replications, in Teresina - PI, Brazil, in 1998. The genetic parameters estimated were: phenotypic and total genetic variance, additive and dominance genetic components of variance and the variance attributed to the environment, heritability in the broad and narrow senses, average degree of dominance and the number of genes controlling the character. The additive - dominance model fitted the data for 100-seeds weight in as much as the midparental value and the additive effect were the more important genetic parameters for the determination of this character. The number of genes that control its expression is five. The occurrence of high values for narrow sense heritability indicates that the selection for seed size can be made in early generations.

Integrated modelling of water availability and water use in the semi-arid Northeast of Brazil

Scarcity of water resources is a. major constraint for development in the semi-arid Northeast of Brazil. Quantification of natural water availability and of water use are key issues within a comprehensive Brazilian-German research project. This paper gives an overview of the integrated hydrological and water use modelling for the federal Brazilian states of Ceará and Piaui covering an area of over 470 000 km2. The model subdivides the area into administrative sub-units (municipalities) of in average about 1000 km2. and uses daily time-steps. The hydrological module is designed to account for: water availability (in terms of river runoff, reservoir storage, groundwater recharge and soil moisture), influence of climate and land-use changes on water balance, large spatial scale (acknowledging the uncertainty of model results in view of scarce data), and specific semi-arid hydroclimatological conditions. This version of the water use module includes domestic, animal and irrigation water uses. The withdrawal water use and consumptive water use can approximately be calculated for the present situation of the municipalities. First results of the two modules and the effects of their interlinkages are presented.

Dispersion of gold and associated elements in stream sediments under semi-arid conditions, northeast Brazil

A stream sediment orientation survey was carried out for gold mineralization in the semi-arid northeast of Brazil. Eleven stations were sampled in duplicate along a 3000-m stream. The stream is ∼1.5 m wide at the upper station and ∼8 m wide at the lower station. Estimated overall stream gradient is 2%. Mineralization at the headwaters occurs as centimeter- to meter-thick gold-sulfide-bearing quartz veins located in a NNE–SSW shear zone and hosted by sillimanite–garnet–biotite schists. Sampling was carried out in summer when the stream was dry. Sediments were dry-sieved on site to collect two 12-l samples of −2 mm material, composited from three to five high-energy sites at each station. In the laboratory samples were dry-sieved to obtain the −2+0.500 mm, −0.500+0.180 mm, −0.180+0.106 mm, −0.106+0.063 mm and −0.063 mm fractions. All fractions less than 500 mm were analyzed for Au, As, Hg, Sb, Cd, Co, Cu, Fe, Pb and Zn. Cursory evaluation indicates that sampling and analytical variabilities are negligible compared to between-station variability. The Au anomaly, which was only consistently detected in the two finest fractions, shows a downstream decay pattern with a decrease of Au values from 40–55 ppb to <5 ppb over a distance of ∼1.3 km. Erratic high and low values are superimposed on this trend. Anomalous downstream dispersion patterns are observed for As, Cu, Pb, Zn, Co and Cd in all size fractions analyzed. These are less erratic than for gold and extend ∼3 km downstream to the limit of the study. Sediment size fraction data show that distribution of gold is closely related to sediment texture, with gold concentrations decreasing as the abundance of −0.063 mm material increases. This relation is observed between adjoining stations but, insofar as abundance of the −0.063 mm increases down the stream, has probably also magnified the anomaly in the headwaters while diluting it further downstream. We attribute the relation between gold and sediment texture, which is not shown by any of the base metals, to gold behaving as a heavy mineral that is concentrated on the streambed by washing away of fine sediments, or diluted by their deposition. Based on the results reported here, it seems possible that in arid regions the limited development of deeply weathered regolith and retention of fines within the drainage basins can hinder development of long dispersion trains for gold. In such situations the importance of pan concentrates and pathfinder elements may be increased.

Caatinga Vegetation Dynamics under Various Grazing Intensities by Steers in the Semi-Arid Northeast, Brazil

The effects of cattle grazing were evaluated on range dynamics of the Caatinga which is a deciduous dry woodland, covering most of the semi-arid Brazilian Northeast. Three stocking rates (SR) were studied (heavy, 1 steer 6.7 ha(-1); moderate 1 steer 10 ha(-1); light, 1 steer 13.3 ha(-1)), in addition to an ungrazed exclosure (zero stocking). In the first phase (1978-81) each stocking rate was tested under continuous and deferred grazing. In the second phase (1981-84), deferred grazing was eliminated, so that pastures became replications of continous grazing. Six steers per pasture were used, and pasture size was used to vary stocking rate. There was no effect of stocking rate or grazing system period on the frequency of the herbaceous species. They were, however, influenced by rainfall in the period, and could be divided into 3 groups. Sixteen species increased with increasing rainfall during the last months of the rainy season, and reached the highest frequency in 1984. Eleven species also increased with increasing rainfall but reached the highest frequency in 1983. Rainfall had no effect on the frequency of 2 important species. Herissantia crispa (L.) Briz. and Selaginella convoluta Spring. Death rate of 5 shrubs (Lippia microphylla Cham., Croton rhamnifolius (Kunth em.) Mull. Arg. Calliandra depauperata Benth. Cordia leucocephala Moric., and Bauhinia cheilantha (Bong.) Steud.) decreased with decreasing stocking rate, 11.7, 9.3, 7.7. and 4.5%, respectively on heavy, moderate, light, and zero stocking. Death rates were higher in easily broken shrub species. L. microphylla and C. leucocephala. Stocking rate also influenced the height growth rate of the tagged shrubs, being respectively -2.7 and 9.8% for heavy and zero stocking. Mean density of shrubs and trees, determined by the Point-Centered Quarter Method, was respectively 21,109, and 447 plants ha(-1) in 1982, and 13,230 and 401 plants in 1984; the main cause of the high shrub death (37.3%) was probably the 1982 drought. Density was not affected by stocking rate. Considering the 7 experimental areas separately, there was no regression between 1982 and 1984 shrub densities. There was, however, regression between 1982 density and the difference between 1982 and 1984 densities.

Fine root mineralization, soil organic matter and exchangeable cation dynamics in slash and burn agriculture in the semi-arid northeast of Brazil

The objective of this study was to understand the causes of crop productivity decline on a soil cultivated by the slash and burn method. The contribution of ashes, fine roots, and soil organic matter (SOM) mineralization to the pool of available nutrients of a nutrient-poor Haplustox of the semi-arid zone of northeastern Brazil was documented. Ashes were the most important input of nutrients to the soil. The burning of the vegetation debris produced 11 Mg ha −1 of ash containing considerable quantities of Ca and K, and some N, Mg and P. The ashes, in general, contained more Ca and Mg, and less N and K, than the estimated requirements of the cassava ( Manihot esculenta) crop during the cultivation cycle, whereas the P in ashes was equivalent to the crop P uptake. About 65% of the fine roots from the native vegetation decomposed in the soil during the first rainy season after the slash and burn, contributing Ca, N, and Mg to stores of available nutrients, with limited supply of K and P. The SOM content decreased with cultivation. The losses ranged from 4 to 16%, 6–18%, and 10–20%, for C, N and organic P, respectively. The sum of exchangeable cations, base saturation and pH increased after the burn, whereas the exchangeable Al and Al saturation strongly decreased, promoting better growing conditions for the cassava crop, particularly during the first years of the cultivation cycle. The soil properties reverted to pre-burn conditions within two or three crop years, productivity declined and the field was abandoned to natural fallow.

Future biomass-based electricity supply in Northeast Brazil

Hydroelectric resources in the semi-arid Northeast of Brazil will be exhausted about the year 2000. Unless viable alternatives can be found, relatively high-cost hydroelectric resources in the environmentally-sensitive North (Amazon) region will be tapped after 2000 to meet electricity demands in the Northeast. The Hydroelectric Company of Sao Francisco (CHESF), the federally-owned utility responsible for generation and transmission of bulk electricity in the Northeast, initiated studies in 1982 to quantify the potential for establishing a widespread biomass-based electricity generating system in its service territory as an alternative to hydro expansion. The analysis here builds on these studies, and includes the possibility of converting biomass into electricity using advanced gas-turbine technologies that are now the focus of commercial demonstration projects in Brazil and elsewhere. Existing sugarcane residues and future potential production of wood on dedicated plantations in the Northeast could be used to generate annually up to 41 TWh and 1400 TWh of electricity, respectively, compared to CHESF's present total annual generation of about 30 TWh. The cost of most of the biomass-derived electricity would be under 4.5 cents kWh −1, which compares favorably with marginal costs projected for hydroelectric projects in the Amazon region and would involve lower capital investment. Expansion of the CHESF system based on biomass rather than hydropower would also bring social benefits, including greater job creation.

Abscesses and caseous lymphadenitis in goats in tropical semi-arid north-east Brazil

This study reports the incidence of abscesses in relation to Corynebacterium pseudotuberculosis infection in goats in north-east Brazil. Among 656 goats examined periodically over almost two years 41.6% were found with superficially palpable abscesses. Most of the infected areas were in the anterior half of the body in front of the pre-scapular region; the inguinal region formed the other prominent area. Among 486 dead or slaughtered goats, 56 (11.5%) revealed abscesses in the internal organs. Lungs and epididymis were affected most, liver, spleen, udder and lateropharyngeal nodes were next in order and kidneys and mediastinal nodes were least affected. Thus the overall incidence of external and internal abscesses was 28.8%; of all the abscesses 27.7% were due to C. pseudotuberculosis and the rest due to infections of Corynebacterium pyogenes and several species of streptococci or staphylococci. The growth of C. pseudotuberculosis-infected and non-infected goats was of the same order and it seems that caseous lymphadenitis is not the cause of much financial loss in north-east Brazil but in view of its high incidence remedial measures should be considered necessary in regions where the goat meat industry is likely to become more intensive and important.

Evaluation of sheep breeds for early growth in tropical north-east Brazil.

Three breeds of sheep, Brazilian Somali, Morada Nova and Santa Inês which are indigenous to hot tropical semi-arid north-east Brazil were studied for their early growth. There were large breed differences in size at birth, at the 86th day and at 6 months. The Santa Inês was the largest and the Brazilian Somali the smallest. The type of birth (single vs. multiple) had a profound effect on weight at virtually all stages of growth which was similar for male and female lambs. Sex effects tended to become significant at around the 86th day, female lambs slightly outweighing males but marked sex differences appeared around 6 months when males outweighed females. The 7-day variation in age of lambs when the weights were taken around the 15th day had a marked effect on weight and correction for age would be necessary in future studies. However, the 7-day variation in age around the 86th day and thereafter did not affect the weights. The birth weight and weights at the 15th, 86th and 112 days and at 6 months were significantly correlated.

Ex Ante Appraisal of New Technology: Sorghum in Northeast Brazil

Policy instruments used to stimulate agricultural output without penalizing the urban consumer are examined. Three categories of instrument variables are considered: a traditional instrument, credit policy; policies to affect risk through reduction in the income variance; and, finally, increased information to improve perception of the distribution of returns from new technology. A model of adoption of sorghum varieties is used to analyze the relative importance of these instruments on the decisions of small farmers in N.E. Brazil. The model indicates that new technology, appropriate for the farmers and the region, should be adopted by farmers highly averse to risk even with an overestimation of the variance of the returns. For nonadopters, improved estimates of the distribution of returns will occur over time as their neighbours adopt and they obtain more information on the new technology. Crop research programmes may need to consider several alternative technologies, as the model results for the sorghum technology adopted were highly influenced by the farmer's risk-aversion coefficient.ADDITIONAL ABSTRACT:Of the several methods which may be used in aiming agricultural development at the small farmers, three factors are examined: credit policy; development and adoption of new technology; and increased information available to the small farmer. A model was constructed using these three factors, and data from semi-arid northeast Brazil was tested. The object was to introduce climatically better suited sorghum into the region in which corn is presently the main crop. The model findings, which were not field tested, show that the new sorghum technology will be adopted partially by a limited number of farmers who are least averse to risk-taking. Credit policy had little to do with the decisions. It is expected that from this foothold, sorghum cropping would spread as other farmers became convinced by the successful adoption of sorghum by their neighbors.