Due to the low natural availability of phosphorus (P) in tropical soils and the plant’s need for P, the use of phosphorus fertilizers of increased efficiency is an important tool for achieving high yields. The aims of this study were to evaluate plant growth, foliar P content and yield of soybean and corn crops in different seasons and places in response to P rates and sources. The sources of P were monoammonium phosphate (MAP) and Policote coated MAP (Policote+MAP). Field experiments were carried out comparing MAP performance compared to Policote coated MAP (MAP+Policote), an additive based on water soluble polymers. Experiments formed by P sources (MAP including 11% N, 52% P2O5 and MAP+Policote including 10% N, 49% P2O5) and rates were carried out in soybean and corn crops in different dates and sites. In the soybean crop, a (2x4) +1 factorial was used, comprising of two sources such as MAP and MAP+Policote and four rates of P (30, 60, 90 and 120 kg ha-1 of P2O5), besides the control. For corn, a (2x5) factorial was used, including two sources and five rates of P (0, 40, 80, 120 and 160 kg ha-1 of P2O5). The results showed that phosphorus fertilization would increase soybean and corn plant heights and yields in different seasons and places. Soybean and corn yield and agronomic phosphorus use efficiency were higher with Policote coated phosphorus fertilizer than with conventional phosphorus fertilizer. Policote coated phosphorus fertilizer can be used as an enhanced efficiency fertilizer because it increased soybean and corn yields in different seasons and places.

The intense agricultural machinery traffic over the plantation ground can lead the erosion and growth difficulty. The goal of this study was to evaluate the soya bean yield after the implantation of species named “recoverable”, of soil structure. The experiment was developed in plots of 20 m × 25 m, located in the Agronomic Institute of Parana (IAPAR), in Santa Tereza do Oeste, Paraná. The plots were cultivated by direct sowing of the following species, considered as treatments: sunn hemp (Crotalaria juncea), rattlebox (Crotalaria spectabilis), velvet bean (Mucuna aterrima), pearl millet (Pennisetum glaucum), pigeon pea (Cajanus cajan), dwarf pigeon pea (Cajanus cajan) beside them no-tillage and no-cover crop planting traditional system (control). Soil samples were collected from 0-10 cm, 10-20 cm, and 20-30 cm-layers with 4 repetitions on each treatment. Soil density and porous soil space were also determined. The plot yield of soybean grains was evaluated over an area of 4.5 m2 for each treatment and grain moisture corrected to 13%. The treatments’ mean yields were compared using the Tukey test at 5% probability. The dwarf pigeon pea and the rattlebox were the most efficient cover crops in the reduction of soil bulk density in 0-10 and 10-20 cm depths. The soybean grain yield did not differ between the evaluated treatments, possibly due to the good precipitation conditions during the soybean growing cycle.

Leakage of transformer dielectric fluids is a concern because it may pose a risk of environmental contamination. In this study, the deleterious effects of vegetable and mineral dielectric fluids in water bodies were investigated using biodegradability and acute toxicity tests with Danio rerio and Artemia salina. Regarding biodegradability, all four tested vegetable oils (soy, canola, sunflower and crambe) were considered as easily biodegradable, presenting degradation rates significantly higher than the Lubrax-type mineral fluid. Acute toxicity tests were performed in two separate experiments without solution renewal. In the first experiment, the organisms were exposed in direct contact to different concentrations of vegetable (soy) and mineral (Lubrax) oils. Total soy-type vegetable oil has a higher toxic effect than Lubrax-type mineral oil. In the second experiment, the organisms were exposed to increasing percentages of the water-soluble fraction (WSF) of both types of tested oils. The LC values for the water-soluble fraction of the Lubrax-type mineral oil were about 5 and 8% for the Danio rerio and Artemia salina bioindicators, respectively, whereas the vegetable oil did not present toxic effect, regardless of its WSF. These results have shown that a strict selection of dielectric fluids and monitoring the leakage from power transformers is a serious duty of environmental protection agencies.

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This work aimed to evaluate the dynamics of physical and hydric attributes of a clayey Latosol cultivated with different cover species. The experimental area was located in the Agronomic Institute of Paraná (IAPAR), in the regional hub of Santa Tereza do Oeste, Paraná, Brazil. The experiment was comprised of seven cover species also called treatments is the course of this work. Three of them were isolated summer species notably Crotalaria juncea, Crotalaria spectabilis, Cajanus cajan (pigeon pea), and the other four treatments winter species cultivated individually or in association including Avena strigosa (Black oat), + (Avena stirgosa + Raphamus sativus (radish), Avena strigosa + Lupinus albus (Lupin bean), and (Avena strigosa + Pisum sativum (pea). The treatments were distributed on a completely random plots of 20 m × 25 m without replication. Soil density, macroporosity, and saturated hydraulic conductivity were measured to follow the changes of the soil structure. Statistical analyses showed that cover crops species did not lead to a significant improvement in soil structural status. Soil density varied between 1.08 and 1.12 Mg m-3, macroporosity from 15.22 and 16.90%, and saturated hydraulic conductivity ranged from 28.83 to 45.07 mm h-1. Soybean grain yield were considered satisfactory in 2016 (mean = 1909.68 kg ha-1) and in 2017 (mean = 3355.30 kg ha-1) most probably due to the good initial structural conditions of the soil, alongside with the good climatic conditions during the two campaigns. Furthermore, the soybean grain yield was positively influenced by Ds which ranged from 1.0 to 1.17 Mg m-3.