João de Deus Gomes dos Santos Junior

Análise de crescimento do capim-marandu submetido a doses de nitrogênio

This research was conducted with the objective of determining growth of Brachiaria brizantha (A. Rich.) Stapf. cv. Marandu under nitrogen (N) rates (28, 112, 210, 294 and 378 mg/L, where N-NO3- : N-NH4+ of 70%:30% proportion was kept constant) and growth ages (21, 28, 35, 42, 49 and 56 days after seedling emergence). The experiment was carried out in greenhouse conditions, with nutrient solution and using ground quartz as substrate. The experimental design used was a complete randomized block design, with treatments arranged in a 5x6 factorial, with four replications. Nitrogen rates and growth ages interaction was significant for all growth attributes of Marandugrass, except for the mean net assimilation rate (NAR). The results showed that the maximum values for the relative growth rate (RGR) and absolute growth rate (AGR) were 0.25 g/g.day and that was observed at 28 days with N rate at 378 mg/L, and 3.68 g/day at 56 days associated to N rate at 378 mg/L, respectively. At 21 days of growth, occurred maximum values of 2.16 dm2/g at the highest N rate for leaf area ratio (LAR), of 0.48 g/g with N rate at 294 mg/L for leaf weight ratio (LWR), and of 5.14 dm2/g for specific leaf area (SLA) at N rate of 378 mg/L.

Minipenetrômetro dinâmico para determinação da resistência à penetração em amostras de solo indeformadas

O objetivo deste trabalho foi descrever e testar um minipenetrometro dinâmico para a determinacao da resistencia do solo a penetracao, em amostras indeformadas. Foram construidas quatro pecas de diferentes massas, para a mensuracao da resistencia a penetracao em solos com conteudos variaveis de agua. Para o teste, foram utilizadas amostras de um Latossolo Vermelho, sob sistemas de plantio convencional e direto. Avaliaram-se o indice de cone, a densidade do solo e os conteudos gravimetrico e volumetrico de agua do solo. O equipamento avaliado e confiavel, preciso, de baixo custo e tem potencial para promover mais estudos sobre intervalo hidrico otimo do solo.