Food webs include complex ecological interactions that define the flow of matter and energy, and are fundamental in understanding the functioning of an ecosystem. Temporal variations in the densities of communities belonging to the planktonic food web (i.e., microbial: bacteria, flagellate, and ciliate; and grazing: zooplankton and phytoplankton) were investigated, aiming to clarify the interactions between these organisms and the dynamics of the planktonic food web in a floodplain lake. We hypothesized that hydrological pulse determines the path of matter and energy flow through the planktonic food web of this floodplain lake. Data were collected monthly from March 2007 to February 2008 at three different sites in Guaraná Lake (Mato Grosso do Sul State, Brazil). The path analysis provided evidence that the dynamics of the planktonic food web was strongly influenced by the hydrological pulse. The high-water period favored interactions among the organisms of the microbial loop, rather than their relationships with zooplankton and phytoplankton. Therefore, in this period, the strong interaction among the organisms of the grazing food chain suggests that the microbial loop functions as a sink of matter and energy. In turn, in the low-water period, higher primary productivity appeared to favor different interactions between the components of the grazing food chain and microorganisms, which would function as a link to the higher trophic levels.

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Aspects related to micronutrients management are still poorly studied and need to be clarified to guarantee sustainable production. In this way, the study aimed to evaluate boron (B) fertilization effects on nutrition and production of common beans. The parameters measured were relative chlorophyll index, dry mass, boron transport, utilization and absorption efficiencies, B content, and B accumulation in plant tissues. The study showed that the dry mass production was negatively affected by B application, with linear dry mass decrease following the increase of B doses. Accordingly, it was found that the common bean cultivar Esplendor presented high absorption capacity of boron, and can reach 175 mg kg −1. However, the high absorption caused phytotoxicity and reduced dry matter production by up to 30%, reflecting the efficiency of boron use by the plant, which was reduced in up to 75%.

One of the potential alternatives to improve the use of water resources is the use of hydro retainer polymer applied to the soil. The objective of this study was to evaluate how irrigation levels and doses of hydro retainer polymer interfere in the production of ’Vanda’ lettuce. The experiment was carried out from December 2017 to January 2018 under protected environment in the Instituto Federal Goiano, Urutaí Campus, Goiás State, GO, Brazil (17º 29’ 10” S of latitude, 48º 12’ 38” W of longitude and 697 m of altitude). The work tested four irrigation levels of 50, 75, 100 and 125% of the evaporation obtained daily by the hook micrometer and five doses of hydrogel polymer (0, 50, 100, 150 and 200 g plant-1). The experimental design was a randomized block design in a scheme of split-plot and four blocks. Canopy fresh and dry mass, plant height, number of leaves and productivity were evaluated. There was 29.24% increase in the dry mass comparing the hydro retainer polymer doses of 0 and 169.28 g and an increase of 14.36% of the height of plants when compared with the irrigation levels of 50 and 125%. The use of a hydro retainer polymer provided a significant increase in all the evaluated productive variables. The irrigation levels influence the fresh mass from aerial part, plant height and productivity. The productivity increased 18.42% for the irrigation levels used and the highest estimated values were presented in the dose of 157.49 g (14.46 t ha-1) hydro retainer polymer.

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Maize is the main crop of Paraná State second season, however the heterogeneity of the environmental conditions creates a challenge for the selection of adapted superior genotypes. The objective of this study was to stratify the environments of the Western and Mid-western mesoregions, to identify the environments that are essential for the selection of genotypes to ensure yield and crop moisture. Data sets regarding the yield and crop moisture of 16 commercial hybrids were used, sourced from Cooperativa Central de Pesquisa Agrícola (COODETEC) Value for Cultivation and Use ("VCU"), testing in a randomized complete block design with two replicates, of crops grown in the interim-harvests of 2014 and 2015 in the west of Paraná, in the Cascavel, Toledo and Foz do Iguaçu microregions, the Mid-western Campo Mourão microregion and Mariluz, constituting the Caiuá sandstone formation. The evaluation of the representativeness of the environments was carried out over one year of study, through environmental stratification analysis, using the factor analysis methodology. The results of the environmental stratification demonstrated that trials in the same environment provide redundant results, both for yield and for crop moisture. There were no gains for the selection of superior genotypes and the positioning in the different microregions yielded complementary data, aiding the selection.