Phosphorus Mobilisation and Immobilisation Vary in the Root Environment of Different Barley Genotypes with Different Phosphate Sources

Abstract

A method was developed to estimate root efficiency of barley (Hordeum vulgare L.) in making available phosphorus (P) from vatious unlabelled, spatingly-soluble compounds containing P. The post-treatment method is based on axenic germination on a P-free medium, removing the seedling from the medium and incubating the P substance to be tested in situ in the medium, followed by soluble P determination. Seven lines oflandrace barley were tested with 8 day old seedlings. CaHPO, was found to be dissolved by five of the lines, while two of them on average immobilized phosphate (dissolved less than in controls without a plant) with significant differences between the lines (p < 0.01). The acidification of the medium by the barley con·elated significantly (r = 0.727; p < 0.001) with the dissolved level ofP from CaHP0 4 • On average, FePO, was immobilized by all the barley lines though with significant differences (p < 0.01), and showed a significant negative cotTelation with the acidification of the medium ( r, = -0.306; p = 0.011). One barley line showed wide variation towards FeP0 4 having both mobilizing and immobilizing plants in the sample, either meaning a temporary change in capability or genetic heterogeneity within the line. The immobilization of FeP0 4 is in accordance with the observed accumulation of FeP0 4 in soils also frequently sown with barley. P of Siilinjarvi Apatite was immobilized by all the barley lines without significant differences, but showed a minor negative con·elation between P dissolving and acidification (r, = -0.168; p = 0.108). These results coiToborate the poor capability of apatite dust to serve as a source of P for barley observed in published field ttials in organic farming, and cast doubts on the usefulness of apatite as a direct fertilizer of slowly soluble P for barley. The polymorphic properties of the landrace barleys with regard toP acquisition are considered against the prescribed fire practices on soil preceding sowing and use of top mulch of manure on sown barley fields in the past. The introduced post-treatment method revealed several statistically significant differences. It can be applied to other sources of P avoiding the use of labelled compounds and as a cheap test extended to various substances, which can then be studied as to their changes by roots of different species.

Pea roots affect immobilisation and solubilisation of phosphorus depending on genotype, stage and phosphorous source

“…In the case of apatite as fertilizer, including Siilinjärvi Apatite, the field trials with annual barley in organic farming (Seuri et al 2001) corroborate the finding that P of apatite is unavailable or poor available to barley. This was confirmed with 7 other barley genotypes with an in vitro method (Ahokas et al 2007). In soil, the tested compounds would be subjected to biological leaching.…”

“…The six pea genotypes did not differ in their ability to solubilise phosphate from CaP significantly (Table 3, 4) even though Ahokas et al (2007) found differences among the barley genotypes. Iron phosphate is one of the major deposited forms of P in peat soils in Finland (Valmari 1970; Nieminen and Jarva 1996) and in field soils that have been fertilized (Hartikainen 1989) with a surplus of P since the 1940s (Saarela et al 2003).…”

“…This study is an extension of the previous one on barley (Ahokas et al 2007). The aim of the study was to assess genetic variation using different putative phosphorus sources with pea.…”

“…To reduce possible genetic variation within the accessions, single plant origins were used. The seeds were usually picked from mature pods stored unopened with sterile forceps, pencil‐marked, weighed and surface sterilized and washed in sterile water series as described (Ahokas and Manninen 2001; Ahokas et al 2007), however, using the vacuum treatment only in the Linie von Nord series, because the germination in some of the pea lines appeared to be impaired by the vacuum step during the sterilisation in 0.01% HgCl 2 . The plants, single per a 14‐ml polypropylene tube (Falcon 2059, USA), were grown for 1 to 15 days on about 7 ml of medium made semisolid with 0.6% agar or about 42 mg per tube (Plant Cell Culture Reagents, A–1296, Sigma, USA) having the inorganic constituents of Barley Medium II (Norstog 1973) but lacking phosphate the plants being subjected to P starvation but supplied with other macro and micro minerals of Barley Medium II.…”

Improving crop nutrient efficiency through root architecture modifications

“…In recent years, considerable research has shown that variation in root system architecture plays a key role in crop nutrient efficiency (Lynch ). Correspondingly, root architecture also can be significantly influenced by nutrient availability, heterogeneity of nutrient supply and symbiotic microorganisms (Williamson et al ; Linkohr et al ; He et al ; Yano and Kume ; Walch‐Liu et al ; Ahokas et al ; Wang et al ; Wu et al ).…”