The agronomy of Andropogon gayanus | [Agronomia de Andropogon gayanus]

This paper reviews studies conducted on the agronomy of Andropogon gayanus Kunth, mainly in West Africa, tropical South America, and northern Australia. Most of the data from tropical America were recorded in the savannas of Colombia and Brazil, almost exclusively on one accession, A. gayanus var. bisquamulatus CIAT 621. This accession has now been released in Brazil, Colombia, Mexico, Panama, Peru, and Venezuela. A cultivar, Kent, also exists in Australia. Andropogon gayanus is a short-day plant with a critical daylength for flowering between 12 and 14 hours. Flowering is optimal at about 25oC. In Colombia, at latitude 3oN, plants flower several times over a 2-year period. In Bolivia and Brazil, between latitudes 16oS and 19oS, flowering is well synchronized and occurs once a year. Variation in flowering time occurs among different accessions. Significant quantities of seed can be produced. Andropogon gayanus is well adapted to the acid-soil savannas and cleared-forest ecosystems of tropical America, the monsoonal tropics of northern Australia, and the low-rainfall areas of India. The species grows best on well-drained sandy clay soils of medium to high fertility. Andropogon gayanus shows excellent tolerance of low soil pH, high aluminum saturation, and nutrient stress. However, responses have been recorded to applications of nutrients, including nitrogen, phosphorus, and potassium. The species shows good drought tolerance and is well adapted to burning. No serious fungal diseases or pests have been recorded in tropical South America. Large amounts of dry matter can be produced. Yields obtained from A. gayanus in many trials in tropical America generally were higher than those reported for most trials in the African savannas. Variations in yield are related to differences in cutting or grazing regimes, fertilizer application, duration of experiment, and climatic and edaphic conditions; Stable associations have been formed with a number of legumes but, under certain conditions, its height and vigorous growth can result in, competition and reduced legume contents.