Plant Growth, Mycorrhizal Association, Nutrient Uptake and Phosphorus Dynamics in a Volcanic-Ash Soil in Colombia as Affected by the Establishment of Tithonia diversifolia

Abstract

ABSTRACT Tithonia diversifolia has the ability to sequester nutrients from soil in its tissues, including P, and has been shown to be useful for cycling nutrients via biomass transfer and improved fallow. We investigated the effects of its establishment from bare root seedlings (plantlets) and vegetative stem cuttings (stakes) on shoot and root growth characteristics, arbuscular-mycorrhizae (AM) associations, nutrient acquisition and utilization, and P dynamics in a fine-textured volcanic-ash soil (Oxic Dystropept) of a mid-altitude hillside in southwestern Colombia. One year after establishment, the following determinations were made: leaf area index; shoot and root N, P, K, Ca, and Mg acquisition; AM root infection; AM fungal spores per 100 g soil; soil chemical characteristics; and P fractionation into inorganic (Pi) and organic (Po) pools. AM root infection in both coarse and fine roots was significantly greater in plants established from plantlets than those established from stakes with differences of 21 and 31%, respectively. Nutrient uptake efficiency (μg of shoot nutrient uptake per m of root length) and use efficiency (g of shoot biomass produced per g of shoot nutrient uptake) for N, P, K, Ca, and Mg were also greater with plants established from plantlets than those established from stakes. Improved nutrient acquisition could be attributed to relief from P stress and possibly uptake of some essential micronutrients resulting from AM association. High soil variability masked the effect of the establishment method on phosphorus pools, and neither the biologically available P (H2O-Po, resin-Pi, and NaHCO3-Pi and -Po) nor the moderately resistant P (NaOH-extractable P) was significantly affected, although plantlets had higher values. This study has shown that on this soil when Tithonia is to be used as a fallow species, the use of plantlets as compared to the stake method of establishment is better for nutrient acquisition and recycling.