Two-way NxP fertilisation experiment on barley (Hordeum vulgare) reveals shift from additive to synergistic N-P interactions at critical phosphorus fertilisation level

Abstract

In a pot experiment, we investigated synergistic interaction of N and P fertilisation on barley biomass (Hordeum vulgare) on both shoot and root level with the aim to determine whether N-P interaction would be the same for all levels of N and P fertilisation. We further aimed to determine whether there was a critical level of N and/or P fertilisation rate, above which, a decrease in resource allocation to roots (as nutrient availability increased) could be demonstrated. Barley plants were grown from seed on a nutrient poor substrate and subjected to a two-way NxP fertilisation gradient using a modified Hoagland fertilisation solution. We observed N-P interactions in shoot and root biomass, and N and P use-efficiencies. A synergistic response in biomass was observed only above a critical level of P fertilisation when P was not limiting growth. Furthermore, we found that the same incremental increase in N:P ratio of applied fertiliser elicited different responses in shoot and root biomass depending on P treatment and concluded that barley plants were less able to cope with increasing stoichiometric imbalance when P was deficient. We provide, for the first time, stoichiometric evidence that critical levels for synergistic interactions between N-P may exist in crop plants.

Phosphorus Supply to Plants of Vaccinium L. Genus: Proven Patterns and Unexplored Issues

“…This picture was formed based on studies of a certain set of model plant species, such as Arabidopsis, rice, tomato, and potato. Currently, it continues to be replenished with information obtained from studies of these species, as well as other species [4][5][6]. However, the features of phosphorus metabolism in plants of the Vaccinium L. genus differ from the above-mentioned plants by being confined to acidic soils with low phosphorus availability; the absence of root hairs, which, in model plants, are involved in phosphorus uptake from soil; and the formation of ericoid mycorrhiza, which is a type of symbiosis, inherent only in plants of the Ericaceae family [7,8].…”