Effect of basal and side-dressed phosphorus on the achene yield and pyrethrins concentration in the achenes of pyrethrum (Tanacetum cinerariifolium) and on soil and plant phosphorus

Abstract

Field experiments were conducted for two years on a krasnozem at Devonport and on an alluvial soil at Ouse in Tasmania to investigate the effect of basal and side-dressed phosphorus (P) on the yield (achene yield) and pyrethrins (Py) concentration in dry achenes, on tissue P concentrations of pyrethrum and on soil Colwell P (Pc). At both sites, 0, 50, 100, 200 and 300 kg P ha-1 was band-placed at planting (basal P) in May 1990. In September 1991, plots were subdivided and 0, 75, 150 and 200 kg P ha-1 was side-dressed. Application of up to 100 kg basal P ha-' increased achene and Py yield by > 50% in the 1990 crop at both sites. Residual P from the 1990 application tended to reduce the 1991 achene yield, Py concentration and Py yield at both sites (P = 0.09). Side-dressing of P in spring 1991 did not influenced the achene and Py yield at either site. The maximum of combined 1990 and 1991 achene and Py yield was attained with 50 kg P ha-1 and no side-dressed P. Top-soil Pc in 1990 was highly correlated with rates of both basal and side-dressed P, achene yield and P concentration in plant tissues. The concentration of P in shoots, apical tissues and youngest fully expanded leaves of the 1990 crop was highly correlated with the rate of basal P and achene yield. The apical tissues were more suitable for diagnostic work because of the ease and speed of sampling.