Neyton de Oliveira Miranda

Causas da variação em produtividade e qualidade do melão em um Latossolo Vermelho-Amarelo fertirrigado

This work was carried out in Mossoro, RN, Brazil, with the objective of identifying soil and fertirrigation variables influencing melon yield and quality. Variables determinated were: yield (export and marketable type); quality (total soluble solids content and pulp firmness); fertirrigation (emitter discharge rate, elevation, distance to water inlet and fertilizer amount); soil chemical properties (pH, organic matter, Ca, Mg, K, Na, potential acidity, P, Cu, Zn, Fe and Mn) and physical properties (contents of clay, sand and silt, soil density and soil moisture). Descriptive statistics, Spearmans correlation and multiple regressions were used for data analysis. Fertirrigation and variables related to a higher water availability improved melon yield and decreased quality. A higher availability of P increased melon yield, while higher soil pH improved fruit quality. Levels of micronutrients Fe and Mn were harmful to the crop, however higher contents of Cu increased export type yield and total soluble solids content.

CARVÃO VEGETAL COMO CONDICIONADOR DE SOLO NA SUCESSÃO ARROZ E FEIJÃO-CAUPI ADUBADOS COM NITROGÊNIO

The effects of biochar and nitrogen application on yields of upland rice and cowpea and on soil fertility were determined in a greenhouse in Macaíba, RN, Brazil. The trial consisted of the succession of two crops in a completely randomized design and a factorial scheme, with four replicates. Initially, four doses of biochar and four doses of nitrogen were tested for cultivation of rice. Subsequently, four doses of biochar and two doses of nitrogen were tested in half of the pots maintained for planting cowpea. Soil was sampled after rice harvest for half of the pots and at end of the trial for the remaining pots. We evaluated the following parameters: mass of hundred grains of rice, dry shoot mass, panicle number, number of filled spikelets and of empty spikelets, and grain production. Determinations for cowpea were: pod number per pot, grain number per pod, and grain production per pot. Measured soil parameters were: pH, contents of organic carbon, P, K, Ca, Mg, Na, cation exchange capacity, and exchangeable sodium percentage. Biochar addition did not influence yield components of upland rice and cowpea, but resulted in increased soil N retention, which influenced rice dry shoot mass, spikelets sterility, panicle number, and grain mass. Biochar also promoted increased soil pH, potassium content, and exchangeable sodium percentage and decreased calcium and magnesium concentrations.