Comunidades zooplanctônicas como bioindicadoras da qualidade da água de quatro reservatórios da região semi-árida do Rio Grande do Norte

The response of zooplankton assemblages to variations in the water quality of four man-made lakes, caused by eutrophication and siltation, was investigated by means of canonical correspondence analysis. Monte Carlo simulations using the CCA eingenvalues as test statistics revealed that changes in zooplankton species composition along the environmental gradients of trophic state and abiogenic turbidity were highly significant. The species Brachionus calyciflorus, Thermocyclops sp. and Argyrodiaptomus sp. were good indicators of eutrophic conditions while the species Brachionus dolabratus, Keratella tropica and Hexarthra sp. were good indicators of high turbidity due to suspended sediments. The rotifer genus Brachionus was the most species-rich taxon, comprising five species which were associated with different environmental conditions. Therefore, we tested whether this genus alone could potentially be a better biological indicator of these environmental gradients than the entire zooplankton assemblages or any other random set of five species. The ordination results show that the five Brachionus species alone did not explain better the observed pattern of environmental variation than most random sets of five species. Therefore, this genus could not be selected as a target taxon for more intensive environmental monitoring as has been previously suggested by Attayde and Bozelli (1998). Overall, our results show that changes in the water quality of man-made lakes in a tropical semi-arid region have significant effects on the structure of zooplankton assemblages that can potentially affect the functioning of these ecosystems

Práticas agroecológicas para o cultivo do gergelim (Sesamum indicum L.)

The exceeded use of the natural resources required by the modern agriculture has been caused soil impoverishment, soil salinization and soil compaction. The unreasonable use of chemical fertilizers and pesticides causes chemical imbalances in the plant tissues, nutritional losses, taste chances and human health problems. The monocrops are more vulnerable to the pest and disease attacks. The aim of this work were to indicate the better relative planting time of the cowpea bean for the sesame/cowpea bean intercropping based on the evaluation of agronomic, economic, ecological and physiological parameters and to evaluate the viability of the cow urine and cassava wastewater use as alternative fertilizers on the sesame cultivation. In a field essay, when the sesame/cowpea bean was evaluate, the mainly treatments were the single planting of the two cultures and the multiple cropping, with the cowpea bean being planted on the same time, 7, 14 and 21 days after the sesame. The mainly treatments of the second essay were the combined doses of the cow urine (0 and 50 ml) and cassava wastewater (0, 500 and 1000 mL). In the intercrop evaluation significant differences were found between the treatments for the most of the parameters. It was verified that as the sowing of the cowpea bean was retarded in relation to the sesame sowing, the sesame performance increased when the cowpea bean performance decreased. The treatment 7 days balanced the competition relations that occurred between the two crops in the intercrop. The sesame presented little pronounced responses to the different doses of cassava wastewater. The cow urine affected the sesame growth and the growth rates increased with the increasing of the application of the product. The responses of the sesame growth to the cow urine application must be related both the nutritional richness of the product and the presence of growth stimulating substances. The obtained results indicated that in the sesame/cowpea bean intercropping, when the sesame is planted 7 days after the sesame, there is a higher possibility of the net gains to the farmer. Cow urine and cassava wastewater may be used as additional organic fertilizers

Crescimento inicial e morfologia foliar em plantas de Mimosa caesalpiniaefolia Benth. Em função do manejo microbiano, sob estresse salino

The sabiá (Mimosa caesalpiniaefolia Benth.) is an endemic species of the Caatinga biome, considered tolerant to salt and water stress. The process of salinization of soil and groundwater and surface water is one of the most important problems of environmental degradation, with its harmful effects being more pronounced in the areas of arid and semiarid regions, and rapidly growing in many parts of the globe, causing problems of the major crop yield. Organic conditioners as barnyard manure, and rice hulls can contribute to reducing the PST, possibly due to the release of CO2 and the production of organic acids during the decomposition of organic matter, and act as sources of calcium and magnesium and inhibit the availability sodium. The intimate association of mycorrhizae and beneficial to plants results in increased uptake of water and nutrients by plants, especially phosphorus, due to their low mobility in soil. The objective of this study was to evaluate the initial growth of thrush seedlings under inoculation with mycorrhizal fungi and fertilized with manure corral and irrigated with water of different salinity levels. The experiment was conducted in greenhouse conditions of vegetation on the premises of the Agricultural School of Jundiaí - UFRN, Campus Macaíba. The adopted statistical design was randomized composed of twelve treatments - three substrates (sterile soil, manure and FMA), four salinity levels (0.2, 1.5, 3.0 and 4.5 dS m-1 ) and five repetitions, totaling sixty experimental units. The results indicate that inoculation with mycorrhizal fungi own contributions to the growth of plants, especially in roots and shoots, which suggests that its application is beneficial in establishing thrush plants in natural conditions, with poor soil in P. Levels salinity caused no effects with statistical significance in plant development, indicating Sabia resistance to it.

Comunidades zooplanctônicas como bioindicadoras da qualidade da água de quatro reservatórios da região semi-árida do Rio Grande do Norte

The response of zooplankton assemblages to variations in the water quality of four man-made lakes, caused by eutrophication and siltation, was investigated by means of canonical correspondence analysis. Monte Carlo simulations using the CCA eingenvalues as test statistics revealed that changes in zooplankton species composition along the environmental gradients of trophic state and abiogenic turbidity were highly significant. The species Brachionus calyciflorus, Thermocyclops sp. and Argyrodiaptomus sp. were good indicators of eutrophic conditions while the species Brachionus dolabratus, Keratella tropica and Hexarthra sp. were good indicators of high turbidity due to suspended sediments. The rotifer genus Brachionus was the most species-rich taxon, comprising five species which were associated with different environmental conditions. Therefore, we tested whether this genus alone could potentially be a better biological indicator of these environmental gradients than the entire zooplankton assemblages or any other random set of five species. The ordination results show that the five Brachionus species alone did not explain better the observed pattern of environmental variation than most random sets of five species. Therefore, this genus could not be selected as a target taxon for more intensive environmental monitoring as has been previously suggested by Attayde and Bozelli (1998). Overall, our results show that changes in the water quality of man-made lakes in a tropical semi-arid region have significant effects on the structure of zooplankton assemblages that can potentially affect the functioning of these ecosystems