Above- and below-ground interactions of grass and pasture legume species when grown together under drought and low phosphorus availability

Abstract

Interactions between annual grass and perennial legume species when they are grown together under drought and limited phosphorus (P) availability are likely to be very important for pasture productivity, but are not well understood. Therefore, the objective of this study was to compare the interactions of drought and species combination on growth, nutrition, hydraulic lift and photosynthesis of the Australian native legume Cullen australasicum and the exotic legume Medicago sativa when grown with the exotic annual ryegrass (Lolium rigidum) with poorly soluble FePO 4 as the source of P. Plants were grown for 22 weeks in monoculture and in legumegrass mixtures in 1-m tall pots filled with river sand. Two moisture treatments were applied, drought (top 70 cm of soil allowed to dry after 16 weeks of establishment) and control (field capacity). In monoculture, shoot dry weight (DW) pot -1 of L. rigidum was higher than that of C. australasicum and M. sativa. In the mixtures, compared with the monocultures, an increase in shoot DW pot -1 for L. rigidum and a decrease for both C. australasicum and M. sativa resulted in a relative yield total >1. Citrate was the main carboxylate in the rhizosphere of all species, except for the drought-treated L. rigidum in monoculture and mixtures, for which malate was the main constituent. Both C. australasicum and M. sativa had higher concentrations of Ca, Mg, S, Cu, Zn, Mn and Mo in their leaves than did L. rigidum. Hydraulic lift was not detected in M. sativa and C. australasicum; likely reasons are discussed. Photosynthetic rate was similar for all species, but L. rigidum had tighter stomatal control. C. australasicum survived longer under drought than did M. sativa. In conclusion, L. rigidum out-competed the legumes. The legumes provided benefits to the growth of L. rigidum through solubilising P, but not through hydraulic lift. In addition, L. rigidum conserved moisture through tight stomatal control and produced an extensive root system to take up water and nutrients efficiently.

Effect of nitrogen, phosphorus and potassium availability on emergence, nodulation and growth of Trifolium medium L. in alkaline soil

“…; Suriyagoda et al . ). A positive effect of P supply on growth of aboveground organs was also observed here, but was most positive when P was applied simultaneously with N and K, supporting the findings of Zhao et al .…”

The Role of Plants in the Effects of Global Change on Nutrient Availability and Stoichiometry in the Plant-Soil System

“…N 2 -fixing plants can have an advantage in N-poor soils dominated by nonfixing plants (Londsdale et al, 1989;Yelenik et al, 2004;Hughes and Denslow, 2005;Morris et al, 2011). Communities dominated by legumes growing in soils with limited availabilities of soil P or water, however, are vulnerable to competition by nonfixing plants with high capacities of P uptake or stomatal control (Suriyagoda et al, 2011), and low availabilities of P reduce the chances of successful invasion by N 2 -fixing plants (Haubensak and D'Antonio, 2011). The success of alien nonfixing plants in native communities dominated by N 2 -fixing plants is reduced when P is added (Brewer and Cralle, 2003).…”

Effects of phosphorus application on photosynthetic carbon and nitrogen metabolism, water use efficiency and growth of dwarf bamboo ( Fargesia rufa ) subjected to water deficit

“…In general, more than 80% of the total amount of P in the soil is immobile and unavailable (e.g. CaeP, FeeP, MgeP, AleP and organic-P) (Suriyagoda et al, 2011). P can be readily absorbed by plants in the orthophosphate (P i ) forms (HPO 4 2À and H 2 PO 4 À ), which occur in soil solutions at very low concentrations (<10 mM).…”

“…P can be readily absorbed by plants in the orthophosphate (P i ) forms (HPO 4 2À and H 2 PO 4 À ), which occur in soil solutions at very low concentrations (<10 mM). Most soils, even fertile types, are deficient in P i as its uptake via root absorption is faster than its replenishment in soil solutions (Suriyagoda et al, 2011). Recent studies have demonstrated that P deficiency inhibits processes related to energy metabolism and biochemical synthesis, such as photosynthesis, respiration (especially the glycolytic pathway) and N fixation; P deficiency also reduces the activities of key enzymes involved in C and N metabolism dos Santos et al, 2004;Burman et al, 2009).…”