Aims: The research was carried out to evaluate the agronomic performance of corn cultivars in contrasting phosphorus environments in the state of Pará, Brazil. Study Design: The experimental design was randomized blocks with ten treatments and three replications. The treatments were composed of ten cultivars: AG 1051, AG 8088PRO2, BR 206, BRS 3046, PR 27D28, 2B655PW, AL BANDEIRANTE, ANHEMBI, CATIVERDE 02 and ORION Place and Duration of Study: In the 2017/18 crop, two competition trials of corn cultivars were carried out at Sítio Vitória, municipality of Santa Maria das Barreiras, state Pará, Brazil. Methodology: Two competition trials of corn (Zea mays L.) cultivars were carried out under contracting conditions of phosphorus: high P (100 kg ha-1 of P2O5) and low P (50 kg ha-1 of P2O5), using simple superphosphate (18% P2O5) as the source. The agronomic efficiency of phosphorus use was obtained by the difference between grain yield in both levels, divided by the difference between doses. The variables evaluated were: ear height, plant height, ear diameter, number of rows per year, number of grains per rows and grain yield. Results: The mean grain yield of the cultivars ranged from 5,446 kg ha-1 (low P) to 11,486 kg ha-1 (high P), and the means of all cultivars were higher in high P. The means agronomic efficiency ranged from 25.1 kg kg-1 (AL BANDEIRANTE) to 96.6 kg kg-1 (AG 1051). Conclusion: The highest phosphorus dose (100 kg ha-1 of P2O5) resulted in higher values in the variables studied. The cultivars that stood out the most, under high and low phosphorus, were AG 8088PRO2, AG 1051 and BRS 3046, the last two being agronomically efficient.

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Soybean is the major crop in the Brazilian Cerrado region. Tocantins state has been increasing soybean production mostly into degraded pasture. However, cover crops such as forages crops are important to implement in regional soybean agricultural systems to increase systems resilience due to climate variability. There is a lack of information regarding to agronomic performance of soybean intercropped with cover crops under no-tillage. The experimental design was randomized complete blocks with four replications in factorial 7 × 2. Seven soybean cultivation systems were tested: 1) soybean intercropped with Urochloa brizantha cv. Marandu; 2) soybean intercropped with Urochloa ruziziensis; 3) soybean intercropped with Panicum maximum cv. Mombaça; 4) soybean intercropped with Panicum infestans cv. Massai; 5) soybean intercropped with Pennisetum americanum; 6) soybean followed by Pennisetum americanum; and 7) soybean and fallow. Two soil acidity and amelioration were tested: 1) with lime and gypsum application; 2) without lime and gypsum application. Soybean grain yield, plant height and number of pods per plant were different. Soybean grain yield were higher with lime ad gypsum application. The highest soybean plants height were observed in the treatments where lime and gypsum were applied, and with soybean intercropped with P. maximun and Millet. Soybean number of pods was positively affected P. infestans intercropped with soybean. There was no significant difference among treatments for mass per 100 seeds. Cover crops showed suitable to increase agronomic performance of soybean.

We discuss strange stars admixed with fermionic dark matter in the presence of a strong magnetic field using the two-fluid Tolman-Oppenheimer-Volkov equations. We describe strange quark matter using the MIT bag model and consider magnetic fields in the range ∼ 1017 - 1018 G. For the fermionic dark matter, we consider the cases of free particles and strongly self-interacting particles, with dark fermion masses m = 5, 100, 500 GeV. We discuss the effects of dark matter and a strong magnetic field on the masses and radii of the stars, as well as on its tidal deformability. Even though strong magnetic fields contribute to decreasing the total mass of the star, they attenuate the rate of decrease in the maximum mass brought about by increasing the dark matter fraction in the admixed system. The most intensely affected observable, however, is the tidal deformability, with variations on the range of 70%-90% for reasonable values of the magnetic field or dark matter central energy density.

Aims: The present study evaluated the efficiency and response to phosphorus (P) use of corn cultivars in the tropical climate in southern Para State, Brazil. Study Design: Two experiments were carried out, in low P (50 kg ha-1) and high P (200 kg ha-1) applications in Randomized block design (RBD), three replicates, and fourteen cultivars were used for the experiment. Place and Duration of Study: The experiment was carried out in the 2019-20 harvest at Sitio Vitoria (8º18'32" S, 50º36'58" W), located in the municipality of Santa Maria das Barreiras, a southern region of Para state, Brazil. Methodology: Phosphate fertilization was used in the sowing groove. In low P, 50 kg ha-1 of P2O5 were applied, and in high P were 200 kg ha-1 of P2O5. The source was simple superphosphate (18% P2O5). The dose in high P was defined to achieve high yields and considering the nutrient content in the soil, in low P the dose was well below. Nitrogen and potassium fertilization in cover were divided: 50% in V4 and 50% in V8. Doses of 150 kg ha-1 of N and 90 kg ha-1 of K2O were used, and fertilizers were used: urea (43% N) and potassium chloride (60% K2O). Results: The highest means were: 8,710 kg ha-1 efficiency and 29.78 kg kg-1 response. The efficient cultivars were: ORION, BR 2022, CR 120, AL BANDEIRANTE, M 274, BRS 3046, and AG 8088. And those considered responsive were: BM 3061, BR206, CATIVERDE 02, BR 205, ANHEMBI, BR 2022, and BRS 3046. Conclusion: The cultivar BR 2022 and BRS3046 showed high efficiency and also a response to phosphorus use.

Aims: This study aimed to select efficient and responsive maize genotypes to the use of nitrogen for silage. Study Design: The experimental design was randomized blocks in a 2 x 11 factorial scheme, the first factor being two nitrogen levels: 165 kg ha-1 of N and 15 kg ha-1 of N, and second factor eleven maize genotypes: BRS 3046, M 274, AG 8088PRO2, ANHEMBI, PR 27D28, AG 1051, P33-16, P33-11, P29-M12, P36-19, and P40-8. Place and Duration of Study: The experiment was carried out in the 2017/18 harvest at Sítio Vitória (8º18'32" S, 50º36'58" W), located in the municipality of Santa Maria das Barreiras, southern region of Pará state, Brazil. Methodology: Sowing fertilization was performed in the furrow with 300 kg ha-1 of NPK 5-25-15. Topdressing nitrogen fertilization was performed only at high N, having as source urea (45% N) at a dose of 150 kg ha-1 of N. Parceled in stages V4 and V8. The shoot fresh mass was evaluated at stages R4 and R5, with the cut performed 20 cm from the soil. Results: The highest shoots fresh masses were obtained in treatments with high use of N, with a general mean of 628 g plant-1. The mean response of 1.87 g of plants per kg of N applied. Genotypes M 274, AG 8088PRO2, PR 27D28, AG 1051 and P 36-19 were efficient to use N. Genotypes AG 8088PRO2, PR 27D28, P29-M12, and P 36-19 were classified as responsive to N application. Conclusion: Genotypes AG 8088PRO2, PR 27D28 and P36-19 were efficient in use and responsive to nitrogen application. And they are recommended for cultivation with low and high technological level.

O fósforo (P) é um importante nutriente para a produtividade da cultura do arroz. No entanto, ocorre baixa eficiência da adubação nos solos do Tocantins, e o aumento nos custos de insumos torna os fosfatos naturais uma alternativa econômica. O objetivo deste trabalho foi avaliar características agronômicas na cultura do arroz (Oryza sativa) sob efeito de doses de fosfato natural reativo. O experimento foi realizado em casa de vegetação entre os meses de janeiro e abril de 2020. Os tratamentos consistiram em quatro doses de rocha fosfatada + dois controles adicionais (Phosactiv® e superfosfato triplo), conduzido em delineamento experimental inteiramente casualizado, com quatro repetições. As unidades experimentais foram compostas por vasos com capacidade para 10 dm-3, onde foram semeadas cinco sementes de arroz por vaso, cultivar IRGA-424, efetuando-se o desbaste para obter duas plantas por vaso. Foram avaliadas a altura de planta; a massa de grãos por planta; o número de panículas por planta, o número de perfilho por planta e o número de grãos por panícula. Além disso, foi avaliado o teor de P pelos métodos Mehlich (P-meh) e resina (P-res), além do pH e o teor de cálcio (Ca). Verificou-se que a rocha fosfatada exerceu maior influência na altura de plantas e número de grão por panícula no arroz nas doses de 295, 62 e 300 kg ha-1 comparado ao fosfato natural comercial. O fosfato natural reativo incrementou mais P no solo do que o superfosfato simples na mesma dose testada.

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