Soil Phosphorus Uptake by Continuously Cropped Lupinus albus: A New Microcosm Design

Abstract

When grown in soils with sparingly available phosphorus (P), white lupin (Lupinus albus L.) forms special root structures, called cluster roots, which secrete large amounts of organic acids and concomitantly acidify the rhizosphere. Many studies dealing with the understanding of this P acquisition strategy have been performed in short time experiments either in hydroponic cultures or in small microcosm designs with sand or sand:soil mixtures. In the present study, we applied an experimental design which came nearer to the natural field conditions: we performed a one-year experiment on large microcosms containing 7 kg of soil and allowing separation of rhizosphere soil and bulk soil. We planted six successive generations of lupins and analysed P uptake, organic P desorption, phosphatase activities and organic acid concentrations in different soil samples along a spatio-temporal gradient. We compared the rhizosphere soil samples of cluster (RSC) and non-cluster roots (RSNC) as well as the bulk soil (BS) samples. A total shoot biomass of 55.69 ± 1.51 g (d.w.) y )1 was produced and P uptake reached 220.59 ± 5.99 mg y )1 . More P was desorbed from RSC than from RSNC or BS (P < 0.05). RSC and RSNC showed a higher activity of acid and alkaline phosphatases than BS samples and a higher acid phosphatase activity was observed in RSC than in RSNC throughout the one-year experiment. Fumarate was the most abundant organic acid in all rhizosphere soil samples. Citrate was only present in detectable amounts in RSC while malate and fumarate were recovered from both RSC and RSNC. Almost no organic acids could be detected in the BS samples. Our results demonstrated that over a one-year cultivation period in the absence of an external P supply, white lupin was able to acquire phosphate from the soil and that the processes leading to this P uptake took place preferentially in the rhizosphere of cluster roots.

Long-term effect of different soil management systems and winter crops on soil acidity and vertical distribution of nutrients in a Brazilian Oxisol

“…patterns of cation uptake and ability of plants to accumulate carboxylic acids in root tissue. The acquisition of P of low lability due to exudation of organic acids has been observed in lupin (Lupinus albus L.) by several researchers (Bais, 2006;Bayon et al, 2006;Shane et al, 2008;Wang et al, 2008). Therefore, based on the above results, it can be expected that cultivating crops with different strategies to access soil nutrients over time may alter soil nutrients and acidity attributes, especially under NT system.…”

“…Thus, these residues probably cycled a larger amount of P, resulting in the higher content of soil available P, especially under NT system. Lupine is well known for excreting large amounts of organic acids such as citrate, malate and fumarate, even under relatively high P availability (Bayon et al, 2006), which promotes the mobilization of P by ligand exchange and/or by dissolving and occupying the adsorption sites. Du to this higher excretion of organic acid, lupine possible accessed some soil P forms that are inaccessible to the other winter species.…”

“…Many factors contribute to this pH change, including the imbalance in cation-anion uptake, particularly affected by nitrogen sources, and increased efflux of protons as a result of P deficiency (Gahoonia and Nielsen, 2004). Besides this, the exudation of organic acids like citrate, malate, fumarate etc., can promote the P mobilization by ligand exchange and by occupying or dissolution of P adsorption sites (Bayon et al, 2006). Neumann and Rö mheld (1999) found that metabolic changes related to exudation of carboxylic acids and protons by plant roots are induced due to P deficiency which depend on multiple factors, i.e.…”

Spatio-temporal dynamics of bacterial communities associated with two plant species differing in organic acid secretion: A one-year microcosm study on lupin and wheat

“…Organic acids were extracted and quantified according to Le Bayon et al (2006b). In brief, soil and root samples were extracted in sterile water by shaking at 1400 rpm for 30 min (Thermomixer compact, Eppendorf, Huber, Rheinach, Switzerland).…”

Phosphorus in Forage Production

“…For P, they use different mechanisms to access the less labile soil P forms and favor the cycling of P in the system as: increase in root/shoot ratio, root surface or increase in absorption rate per root unit [62]; increase in the number, shape, and thickness of the root hairs [63]; root phosphatases exudation [64] or organic compounds capable of complex metals phosphate associated [65]; by mycorrhizal association in which the fungal hyphae extend the root area [66] or with other microorganisms capable of favoring the cleavage or breaking of organic compounds with the consequent release of the phosphate anion [62,67].…”