Influência De Níveis De Potássio No Crescimento Radicular E Na Absorção De Nutrientes Em Cultivares De Arroz De Terras Altas

Potassium (K) is an essential nutrient for upland rice growth, but little information on the effects of K on root growth and nutrient uptake capacity of upland rice is found. Therefore, an experiment was conducted under greenhouse conditions to evaluate the influence of soil K levels on root growth and nutrient uptake of four upland rice cultivars. A completely randomized experimental design, in a 4x4 factorial scheme (4 levels of K: 20, 40, 80, and 160 mg dm-3; 4 cultivars: Caiapó, BRS-Primavera, IAC-202, and Maravilha) was used, with four replications. Based on regression equations, the highest values of root length density would be found with 136 mg dm-3 of K. The root diameter and dry matter, shoot dry matter and shoot K concentration increased linearly with the increasing K rates. The shoot K concentration of the upland rice cultivars did not differ. The increased level of K in the soil reduced the shoot Ca concentration of intermediate and modern cultivars, and the shoot Mg concentration of all cultivars. The potassium fertilization increased the plant growth, but the magnitude of this effect varied according to the cultivar. © 2017, Universidade Federal Rural do Semi-Arid. All Rights Reserved.301324

Upland rice yield as affected by previous summer crop rotation (soybean or upland rice) and glyphosate management on cover crops

O correto manejo químico das plantas de cobertura visa obter maiores benefícios com a sua introdução nos sistemas agrícolas. O objetivo deste estudo foi avaliar como a produção do arroz de terras altas é afetada pela safra de verão anterior, pela espécie e pela época de dessecação das plantas de cobertura por glifosato. Foram semeadas plantas de cobertura (novembro de 2007), seguidas pelo arroz em metade da área experimental e soja na outra metade (novembro de 2008); após a colheita dessas culturas, as mesmas plantas de cobertura foram semeadas novamente (março de 2009), seguidas pela semeadura do arroz de terras altas (novembro de 2009) em toda a área experimental. Assim, o experimento consistiu na combinação de cinco plantas de cobertura (pousio, Panicum maximum, Brachiaria ruziziensis, B. brizantha e Pennisetum glaucum) x quatro épocas de dessecação (30, 20, 10 e 0 dias antes da semeadura do arroz) e dois antecedentes da safra de verão (arroz ou soja) no sistema plantio direto (SPD), mais dois tratamentos controle no sistema convencional (SC). As culturas de cobertura alteram significativamente a produtividade de grãos do arroz de terras altas e seus componentes. Há tendência significativa de se obter maior produtividade do arroz quando a dessecação das culturas de cobertura é feita mais distante da época de semeadura de arroz (de 2.577,1 kg ha-1, dessecação realizada no dia da semeadura, para 3.115,3 kg ha-1, dessecação realizada 30 dias antes da semeadura do arroz). Soja como safra de verão anterior permite maior produção de arroz de terras altas (3.754 kg ha-1) do que arroz como antecedente de safra de verão (2.635 kg ha-1). Rotação pousio/soja/pousio (4,507 kg ha-1) e milheto/soja/milheto (4,765 kg ha-1) no plantio direto e pousio incorporado/soja/pousio incorporado (4,427 kg ha-1) no sistema de plantio convencional permitiram maior produção de arroz; a produtividade do arroz é semelhante em plantio direto (3,194 kg ha-1) e em plantio convencional (2,878 kg ha-1).The appropriate chemical management of cover crops in no-tillage aims to obtain greater benefits with its employment in agricultural systems. The objective of this study was to assess upland rice yield as affected by the previous summer crop, species and desiccation timing of cover crops by glyphosate. Sown cover crops were sown (November 2007), followed by rice in half of the experimental area and soybean in the other half (November 2008). After the harvesting of these crops, the same cover crops were sown again (March 2009) and followed by upland rice in the total area (November 2009). The experiment consisted of the combination of five cover crops (fallow, Panicum maximum, Brachiaria ruziziensis, B. brizantha and Pennisetum glaucum), four desiccation timings (30, 20, 10 and 0 days before rice sowing), and two antecedents of the summer crop (rice or soybean) under no-tillage system (NTS), plus two control treatments at conventional tillage system (CTS). Cover crops significantly affect rice grain yield and its components. There is a significant tendency to highest yield when cover crop desiccation is conducted farther from the rice sowing date (from 2,577.1 kg ha-1 - desiccation at rice sowing to 3,115.30 kg ha-1 - desiccation 30 days before rice sowing). Soybean as an antecedent of summer crop allows better upland rice yield (3,754 kg ha-1) than rice as an antecedent of summer crop (2,635 kg ha-1); fallow/soybean/fallow (4,507 kg ha-1) and millet/soybean/millet (4,765 kg ha-1) rotation at no-tillage system, and incorporated fallow /soybean/ incorporated fallow (4,427 kg ha-1) at conventional tillage system allow the highest rice yield; upland rice yield is similar at no-till (3,194 kg ha-1) and till system (2,878 kg ha-1).Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq