The number of studies on plant compounds with insecticidal activity has increased in recent years, and one of the primary targets of these compounds is leaf-cutter ants, which are considered the most important pests in Brazilian plantations, especially ants of the genus Atta. The objective of this study was to evaluate the toxic activity of the crude extract and fractions of the leaves of Esenbeckia pumila Pohl (Rutaceae) on Artemia salina and Atta sexdens rubropilosa and to perform a phytochemical study of this plant species. The toxicity of the extract and fractions was evaluated by determining the mean lethal concentration (LC50) on A. salina. The insecticidal activity was evaluated by feeding the ants an artificial diet containing the crude extract or fractions, and the results were analyzed using the log-rank test. The substances were isolated by chromatography, and the molecular structure was determined by spectroscopy. In the bioassay with A. salina, the ethanol extract and dichloromethane and ethyl acetate fractions were highly toxic. The analysis of survival curves indicated that the mortality rate of A. sexdens rubropilosa workers fed different fractions was higher than that of ants fed the control diet, especially the ethyl acetate fraction, with a mean survival time of 3 days and cumulative mortality of 100% on day 21 (p<0.05). The phytochemical study of this plant species allowed isolating the flavonoid rutin and a mixture of the triterpenes α-amyrin, β-amyrin, and lupeol. These results suggest the insecticidal potential of E. pumila on Atta sexdens rubropilosa.

Intercropping system and the use of green manure with spontaneous species has been an alternative farming method applied to the productive sector of vegetables in the northeastern semi-arid region. The objective of this work was to determine which amount of Calotropis procera must be incorporated into the soil to provide the highest productive performance of the component crops and increase the profitability of the carrot and cowpea intercropping. The experimental design used was randomized complete blocks with five replicates. The treatments consisted of four amounts of C. procera incorporated into the soil: 10, 25, 40 and 55 t ha-1 on a dry basis. The characteristics evaluated in this intercropping system were: commercial productivity of carrot roots, yield of cowpea green grains, land equivalent ratios for component crops and for the intercropped system, score of the canonical variable of the association, and the economic indicators of gross income, net income, rate of return, and net profit margin. The maximum agronomic efficiency of the carrot x cowpea intercropping was reached at the land equivalent ratio of 1.12, using 43.39 t ha-1 of C. procera biomass incorporated in the soil, while the maximum economic efficiency of the carrot and cowpea crops association was obtained at the net income of R$ 17,856.43 ha-1, in the amount of 40.60 t ha-1 of C. procera biomass added to the soil.

The aim of this study was to evaluate the chemical composition of swine wastewater (SW), and its effect on the chemical attributes of soil and plants in a long-term experiment. The area was designed for an 8-year hay production, using Tifton 85 grass (Cynodon spp.), with an average annual application of 360 m3 ha-1, divided into 6 applications. Also, soil chemical composition was evaluated at 0.0-0.20 and 0.20-0.40 m of depth, and the chemical composition of plant and vegetable materials on the ground were evaluated for two months (November and June). Concentrations of N, Ca, and Cu in SW did not decrease from the affluent to the storage lagoon. It was observed that the content of Cu, Zn, and Mn was classified as in excess in soil that could be a consequence of high levels of these micronutrients utilized in rations of swine in the SW supplier farm, mainly in the rations of piglets combined with a low extraction of these nutrients by plants. In relation to micronutrients and P (46.08 mg dm-3) in the soil, these should be evaluated in greater depth than performed in the present study, because the concentrations did not vary considerably among depths and were high. The concentrations of Cu and Zn were high in shoot plants with an average of 133.0 and 139.30 mg kg-1, respectively. The continuous use of SW should be monitored continuously through analyses of soil and waste, and alternatives must be researched to reduce the concentration of micronutrients and P in SW.

Dwarf coconut tree is the main variety for commercial use in Brazil, which ranks fourth in world coconut production. However, the genotypes used still have limitations and genetic variability is required. The aim of this study was to estimate the genetic variability in dwarf coconut accessions preserved at the Germplasm Bank of Brazil at different harvesting times and using agronomic descriptors of plant and fruits. The accessions Brazilian Green Dwarf-Jiqui, Cameroon Red Dwarf, Malayan Red Dwarf, Brazilian Red Dwarf-Gramame, Brazilian Yellow Dwarf-Gramame, and Malayan Yellow Dwarf were assessed by means of 30 descriptors Variance analysis was performed and the genetic diversity was quantified by using the Mahalanobis’ generalized distance and expressed by means of UPGMA clusters, Tocher optimization, and canonical variables. The maximum likelihood analysis was used to estimate the components of variance with the data of each plant in a sample of 11 descriptors of great importance for the genetic improvement of the coconut tree. A phenotypic divergence was found among the accessions using the UPGMA clusters, Tocher optimization and graphic dispersion obtained with canonical variables. The use of the maximum likelihood analysis confirms the existence of genetic variability in the accessions for the descriptors fruit polar and equatorial diameter, nut polar diameter, total fruit weight, and epicarp thickness, which presented a heritability varying from 0.17 to 0.39. There is a possibility of genetic gains with the selection of these traits for use of accessions in breeding programs.

Determining the effects of using wastewater as fertilizer on soil chemical properties allows a safe reuse of this effluent in agriculture. This study evaluated the effects of fertigation with tertiary treated wastewater (TTW) from the Janaúba sewage treatment plant on chemical properties of a Latosol (Oxisol) with banana crops of the Prata-Anã cultivar in the semiarid region of Brazil. A randomized complete block design with four replications was used to test four TTW rates (70%, 130%, 170%, and 200% of the limit of 150 kg ha-1 year-1 of Na that can be applied to the soil) and compare them to a control without TTW. Soil samples from the 0.0-0.2, 0.2-0.4, 0.4-0.6, and 0.6-0.8 m layers were collected at the end of the first crop cycle to evaluate soil chemical properties-pH, soil organic matter (SOM), P, K, Na, Ca, Mg, Al, potential acidity (H+Al), base saturation, B, Cu, Fe, Mn, Zn, remaining P, and electrical conductivity (EC). The use of TTW increases soil pH and decreases exchangeable Al content, thus, reduces the need for liming. However, Na contents increased faster than EC in the soil, indicating that the use of TTW tends to alter soil physical properties over time. The use of TTW had no effect on the soil OM, P, Ca, Mg, and micronutrients contents, potential acidity, and base saturation. The changes in soil chemical attributes observed at the end of the first crop cycle were not limiting to the banana crop.

The use of mycorrhiza is a promising biotechnology that makes coffee cultivation sustainable in the use of fertilizers. In this sense, plant growth and phosphorus contents were assessed in coffee inoculated with Rhizophagus clarus, Claroideoglomus etunicatum and Dentiscutata heterogama in soil fertilized with 0, 0.74, 1.48 and 2.96 g P2O5 kg-1. The experimental design was a randomized block design in a 4 × 4 factorial scheme with four replications. The mycorrhizal seedlings were previously produced and later transplanted to pots, simulating the field planting. The assessments were performed 150 days after transplanting. All variables were influenced by inoculation, but the effects were dependent on P doses. P doses higher than 50% of the recommended dose (0.74 g P2O5 kg-1) decreased the benefit of mycorrhiza. The fungi Rhizophagus clarus and Claroideoglomus etunicatum promoted a higher growth of coffee plants when compared to non-inoculated plants in non-sterilized soils and with a reduction in the applied P.

Soil is a dynamic and complex system that requires a considerable number of samples for analysis and research purposes. Using multivariate statistical methods, favorable conditions can be created by analyzing the samples, i.e., structural reduction and simplification of the data. The objective of this study was to use multivariate statistical analysis, including factorial analysis (FA) and hierarchical groupings, for the environmental characterization of soils in semiarid regions, considering anthropic (land use and occupation) and topographic aspects (altitude, moisture, granulometry, PR, and organic-matter content). As a case study, the São José Hydrographic Microbasin, which is located in the Cariri region of Ceará, was considered. An FA was performed using the principal component method, with normalized varimax rotation. In hierarchical grouping analysis, the “farthest neighbor” method was used as the hierarchical criterion for grouping, with the measure of dissimilarity given by the “square Euclidean distance.” The FA indicated that two factors explain 75.76% of the total data variance. In the analysis of hierarchical groupings, the samples were agglomerated in three groups with similar characteristics: one with samples collected in an area of the preserved forest and two with samples collected in areas with more anthropized soils. This indicates that the statistical tool used showed sensitivity to distinguish the most conserved soils and soils with different levels of anthropization.

Swine wastewater can be used as a biofertilizer and promote significant improvements in soil physical-chemical attributes and yield. The objective of this study was to evaluate the effects of swine wastewater application on soil and maize yield. The experiment was conducted at the Agricultural Sciences Center of the Federal University of Piauí, in Teresina, Piauí, Brazil, from August to November 2015. The experimental design used completely randomized blocks in split-plot scheme, with five doses of swine wastewater (0, 25, 50, 75 and 100 m3 ha-1) in the plots and two soil depths (0.20 and 0.40 m) in the subplots, with four replications. Exchangeable contents of calcium, magnesium, phosphorus, potassium and sodium, electrical conductivity, pH, sum of bases, base saturation, potential acidity and cation exchange capacity, and crop yield were evaluated. Results showed calcium, magnesium, sum of bases and cation exchange capacity increased with elevated levels of swine wastewater. Potassium and sodium contents however decreased with doses of 51.58 and 52.28 m3 ha-1, respectively. Except for potassium and potential acidity, variables showed higher values at the 0-0.20 m depth.

Spain contains a third the entire irrigated area of Europe, accounting for 15% of the cultivated area of the country and almost 60% of the national agricultural production. Knowledge of the spatial and temporal variability of reference evapotranspiration (ETo) and the probabilistic theory of extreme events is crucial for the elaboration of sustainable irrigation projects. The objective of this work was to define the frequency distribution that best describes ETo for the design of irrigation systems in the region of Andalusia. We used ETo data for the period 2001 to 2015 from 56 meteorological stations. The values were accumulated over three consecutive days. For all accumulated periods, nine probability distributions were adjusted. The probability distribution that best described ETo for the design of irrigation systems in the region was the Gumbel II distribution. The maximum daily ETo to be considered in irrigation projects in this region is, on average, 10 mm. The accumulated ETo for periods of 5, 10, and 30 days that should be considered are, on average, 42 mm, 78, mm and 224 mm, respectively.

Many watermelon (Citrullus lanatus) diseases are caused by soilborne pathogens in Brazil and worldwide. The goal of this study was to identify and quantify the frequency of phytopathogenic fungi associated with watermelon root rot and vine decline that were also present in the roots of weeds in the major watermelon production regions in the state of Rio Grande do Norte, Brazil. We collected root samples from 10 of the most prevalent weed species in 16 watermelon producing areas. The plants were identified and their frequencies in the fields were calculated. The fungi found in the weed roots were isolated and the main genera associated with watermelon vine decline were identified. We identified 13 weed species belonging to nine botanical families. The weed species with the highest frequencies found in the field were Amaranthus spinosus (25.0%), Trianthema portulacastrum (18.8%), Commelina sp. (18.8%), and Boerhavia diffusa (12.5%). The fungi Macrophomina, Rhizoctonia, and Monosporascus were isolated from the roots of the weed plants. While Macrophomina was isolated from 12 different types of plants, Rhizoctonia and Monosporascus were isolated from four and two different plant species, respectively.