Abstract
Zinc (Zn) is an essential micronutrient for plants, due to its role as a functional, structural, or regulatory cofactor in a large number of enzymes. The element is necessary for the synthesis of tryptophan, which is a precursor of indoleacetic acid. The aim of this study was to evaluate the behavior of two cowpea cultivars fertilized with four doses of Zn (0.0, 2.0, 4.0, and 6.0 kg of Zn ha-1) regarding dry grain yield (PGS), in addition to quantifying leaf and grain Zn content and grain crude protein. The experiment was conducted in the town of Brejo, in the state of Maranhao, Brazil. A 4 x 2 factorial scheme was used with four replications. Response functions were adjusted by calculating the Zn doses which provided a maximum technical efficiency for each genotype. The tested cultivars of cowpea showed no great difference regarding Zn demand applied to the soil, ranging from 3.2 to 3.4 kg of Zn ha-1 for BRS Tumucumaque and BRS Guariba, respectively. Concerning Zn use efficiency, BRS Guariba was more responsive than was BRS Tumucumaque, i.e. the same dose of Zn produced 70 kg grain and 2.1 kg crude protein per hectare.
Highlights
The cowpea presents high contents of proteins, fibers, minerals such as iron, zinc, potassium, magnesium, and phosphorus, in its chemical composition, as well as low lipid content (FROTA et al, 2008)
Concerning Zn use efficiency, BRS Guariba was more responsive than was BRS Tumucumaque, i.e. the same dose of Zn produced 70 kg grain and 2.1 kg crude protein per hectare
For Zn concentration in the cowpea plant tissue, a significant effect (p
Summary
The cowpea presents high contents of proteins, fibers, minerals such as iron, zinc, potassium, magnesium, and phosphorus, in its chemical composition, as well as low lipid content (FROTA et al, 2008). The global food demand will continue to grow and, as estimated, there will be a need to double global agricultural production for the period of 19902030, increasing by two and a half to three times in developing countries (GRAHAM; WELCH, BOUIS, 2001). A recent study by Garvin, Welch, and Finley (2006) shows that the increase in productivity obtained through plant breeding has an inverse relation to grain micronutrient content over the years. This is a negative aspect since human wellbeing requires at least 22 mineral elements. There is a need to associate the quality of agricultural and livestock production with health and nutrition, and the industry will be pressured to provide foods with greater nutritional quality
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