Ann-Mari Fransson

Effects of hardened wood ash on microbial activity, plant growth and nutrient uptake by ectomycorrhizal spruce seedlings

Abstract Plant growth, nutrient uptake, microbial biomass and activity were studied in pot systems containing spruce seedlings colonised with different ectomycorrhizal fungi from an ash-fertilised forest. The seedling root systems were enclosed in mesh bags inside an outer compartment containing crushed, hardened wood ash. Three different species of mycorrhizal fungi and a non-mycorrhizal control were exposed to factorial combinations of ash and N addition. Ash treatment had a highly significant, positive effect on plant growth and on shoot and root concentrations of K, Ca and P, irrespective of mycorrhizal status. Mycorrhizal inoculation had a significant effect on plant growth, which was proportionally greater in the absence of ash. N addition had a significant positive effect on plant biomass in mycorrhizal treatments with ash, but no effect in non-mycorrhizal treatments or most of the mycorrhizal treatments without ash. Piloderma sp. 1, which was earlier found to colonise wood ash granules in field studies, appeared to accumulate Ca from ash in the mycorrhizal roots. 5-6.7% of the total P in the ash was solubilised, with 0.9-1.5% in solution, 3.6-4.6% in the plants and 0.5-1.5% in microbial biomass. Bacterial activity as determined by [(3)H]-thymidine and [(14)C]-leucine incorporation was significantly greater in ash treatments than in controls with no ash addition. Principal component analysis (PCA) of phospholipid fatty acids (PLFAs) showed a clear difference in bacterial community structure between samples collected from ash-treated pots and controls without ash.

Phosphorus Nutrition: Rhizosphere Processes, Plant Response and Adaptations

Management of soil phosphorus (P) remains a crucial issue for the economic and environmental sustainability of agriculture and natural ecosystems globally. It is therefore essential that we have appropriate understanding of the mechanisms by which plants are able to acquire P from soil. In this chapter, various processes and physiological traits of plants that facilitate the availability and acquisition of P from soil are outlined, and some possibilities for deploying these traits into agricultural germplasm discussed. Better understanding of these processes and the development of improved germplasm may ultimately improve the P-use efficiency of agricultural systems and provide valuable information for wider-scale land and resource management. However, at present it is evident that the full extent of the complexity of the gene-by-gene and gene-by-environment interactions that are associated with plant P nutrition are not well appreciated. It is therefore important that a systems approach to P management continues to be developed for a more sustainable agriculture.

Plantago lanceolata L. and Rumex acetosella L. differ in their utilisation of soil phosphorus fractions

To establish relationships between soil phosphorus (P) fractions and leaf P, a mycorrhizal species (Plantago lanceolata L.) was compared with a typically non-mycorrhizal species (Rumex acetosella L.) in a glasshouse experiment. The plants were grown in 40 soils from non-fertilised, abandoned pastures or abandoned arable fields and leaf P concentration were found to be related to various soil P fractions after six weeks of growth. The differences in the P fractions in soil can account for a large share of the variation in leaf P concentration in both species, but the two species differed in their utilisation of P fractions. Leaf P concentration of R. acetosella was more related to extractable soil P than that of P. lanceolata. Rumex acetosella showed a higher maximum P concentration. The P fractions accounting for the largest share of the variation in leaf P concentration was the Bray 1 extractable and the weak oxalate (1 mM) extractable P, and for P. lanceolata also the Na2SO4+NaF extractable P fraction. P extracted with these methods accounted for up to 80% of the variation in P concentration in leaves of R. acetosella and 65% of the variation in leaves of P. lanceolata. More P extractable with weak oxalate, Na2SO4+NaF and strong oxalate (50 mM) was released from the soil than was taken up by the plants during the experimental period. The Bray 1 extractable P fraction, however, decreased in both unplanted and planted soils. Phosphatase release was not induced in any of the plants during the experimental period, indicating that they were not mobilising soil organic P. However, some of the methods extracted a large share of the organic P and still explained much of the variation in leaf P concentration. Mycorrhizal colonisation of P. lanceolata was inversely related to the extractable soil P. The consistently fast P uptake of R. acetosella indicates that this species have a high demand for P. The differences in P utilisation between R. acetosella and P. lanceolata could be caused by their different mycorrhizal status.

Phosphorus fertilisation causes durable enhancement of phosphorus concentrations in forest soil.

The duration of P fertiliser in acid forest soil was investigated in a Norway spruce (Picea abies Karst.) forest in southcentral Sweden. The fertilisation of the soil started in 1967, but no P has been applied since 1988. The N fertilisation is still continuing. Totally, 300 kg P per hectare, as superphosphate, and/or 1090 kg N per hectare, as ammonium nitrate, was applied. Concentrations of both 0.05M Na2SO4 + 0.02M NaF extractable P and 0.5M H2SO4 extractable P in the Of, Oh, E and top B horizons of fertilised soils were elevated compared to the control. The P fractions considered to be extracted are adsorbed and some Al-bound phosphate, in the case of Na2SO4 + NaF, and Ca phosphates, in the case of H2SO4. 3-4% of the added P was recovered as Na2SO4 + NaF extractable P, and 10-22% was recovered as H2SO4 extractable P in the soil profile down through the first 5 cm of the B horizon. Still continuing ammonium nitrate fertilisation has decreased the H2SO4 extractable P concentration in this soil. Cumulative P fertiliser application of 300 kg P per hectare has counteracted this decrease

Phosphorus Solubility in an Acid Forest Soil as Influenced by Form of Applied Phosphorus and Liming

Abstract Sedimentary phosphorus, superphosphate, and wood-ash, as well as either sedimentary phosphorus, superphosphate or ash combined with lime, were distributed in selected plots in an 80-yr-old Norway spruce forest [Picea abies (L.) Karst], After 2 yrs, the sedimentary phosphorus had increased the oxalate/oxalic acid-extractable P in the O-horizon, and the superphosphate had increased the oxalate/oxalic acid-extractable P in the E-horizon. At first, the percolation water from the superphosphate treatment showed high P concentrations. It soon returned to control levels, however. The percolation water from the sedimentary phosphorus treatment gradually showed increased phosphate concentrations. The wood-ash increased neither the amount of extractable P nor the P concentration in the percolation water. The oxalate/oxalic acid-extractable P from the sedimentary P treatment was reduced by liming. The P concentration in the percolation water also tended to be reduced. This was perhaps due to formation of Ca...

Evaluation of oxalate/oxalic acid for extracting plant available phosphorus in unfertilized acid soils

The extractability of phosphorus (P) was studied in an acid, unfertilized soil at an abandoned farm and in 40 different soils from former agricultural fields and pastures. Oxalate/Oxalic acid extraction was compared with a number of other methods in order to evaluate the suitability of oxalate/oxalic acid as a method for extracting P from soil. The extracting efficiency and a rough estimate of the origin of the extracted P was also investigated. Total and molybdate reactive P extracted with weak (1 mM), acid (9.35 mM, pH 2.3), and strong (50 mM) oxalate correlated well with Na2SO4 + NaF, Olsen P, and Bray 1 extractable P (0.96 > r > 0.77). Total and molybdate reactive P fractions determined by different oxalate methods were also closely correlated (0.99 > r > 0.84). Only total organic P did not correlate with the other P fractions extracted. However, the large strong oxal extractable P fraction was correlated to many of the weaker extractable fractions. A large share of this fraction is probably organic. The Na2SO4 + NaF extraction, Olsen P, and Bray 1 were also closely correlated. The more loosely adsorbed fractions are possibly replenished to some extent when the soluble phosphate is consumed by plant uptake. A large share of total P extracted with acid (9.35 mM) and strong (50 mM) oxal was organic. The molybdate reactive fraction, however, was fairly constant up to 9.35 mM oxalate in the solution, neither depending on solution concentration nor on pH. Total P extracted with oxalate was related to the logarithm of the extractant concentration. The advantage of the oxal method is that the pH can be adjusted to fit a desired soil pH, and both extractant concentration and analytical method could be chosen to determine either loosely bound P or a substantial amount of total P that might be potentially available.