Effects of irrigation and nitrogen fertilization rates on yield, agronomic efficiency and morphophysiology in Tithonia diversifolia

Abstract

Abstract Tithonia diversifolia (Tithonia) is performed as an invasive species with a high adaptive potential that can be used for several purposes, including an alternative source of forage for different animal categories. The use of Tithonia is growing rapidly as farmers recognize its high accumulation of biomass, good nutritional value and adaptation to tropical environments. However, the effects of irrigation and nitrogen on the characteristics of Tithonia have been poorly studied. In this context, the objective of this study was to identify changes in the productive characteristics and morphophysiology of Tithonia under different irrigation simulations and nitrogen fertilization rates, seeking to understand its adaptive potential in different water and nutritional scenarios, improvements in the efficiency of the use of water and nitrogen and its potential for use in a global context. Field trials was a split-plot design with three replicates. Whole plots were irrigation rate (0%, 25%, 50%, 75% and 100% of crop evapotranspiration - ETc) and the subplots were the nitrogen fertilizer rate (0, 50, 100 and 150\xa0kg\xa0ha−1). There were significant effects of irrigation, nitrogen, and their interaction on dry biomass accumulation, nitrogen- and water-use efficiency, plant height, chlorophyll index, and photosynthetic rate. Irrigation and nitrogen rates increased the dry biomass accumulation. The highest dry biomass accumulation was 7.32\xa0Mg\xa0ha−1 in cycle I and 10.4\xa0Mg\xa0ha−1 in cycle II. The greatest nitrogen-use efficiency was observed at a rate of 100\xa0kg of nitrogen\xa0ha−1, and the greatest water-use efficiency was observed at irrigation 75% ETc. Irrigation and nitrogen also increased plant height, chlorophyll index, and photosynthetic rate. Tithonia proved to be a plant adapted to the humid temperate climate and sandy-loam texture soil, presenting great dry biomass accumulation potential even without irrigation and nitrogen fertilization. However, the greatest dry biomass accumulation was obtained with water replacement of 100% of ETc, the crop evapotranspiration, and nitrogen fertilization of 150\xa0kg\xa0ha−1.