Published online by Cambridge University Press: 27 March 2009
In two field experiments, ground limestone (2·5–20 t/ha), dolomite (4·25 t/ha) and gypsum (3·75 t/ha) were applied to acid krasnozems (Forthside, pH 5·6 and Elliott, pH 5·1), and poppy capsule and morphine yields, leaf nutrient contents and soil chemical properties were measured.
Capsule and morphine yield increased more than two-fold at Forthside as the pH in the surface soil (0–150 mm) increased from 5·6 to 6·1, and by 30-fold at Elliott where the pH increased from 5·1 to 6·0. Capsule morphine concentration was depressed by high rates of ground limestone at both sites but maximum morphine yields of 15·7 kg/ha at Forthside and 11·3 kg/ha at Elliott occurred at the highest rate of ground limestone. Gypsum did not increase yield at Elliott, but at Forthside the gypsum and ground limestone treatment of equivalent calcium content increased yields to the same extent.
The lowest yields at each site were associated with calcium concentration in the leaves at flowering of less than 1% and marginal or high amounts of extractable soil Al at Forthside and Elliott respectively. Concentrations of Ca, P and Mo in leaves were increased by lime applications but leaf concentrations of N, P, Mn, B and Mo on low yielding plots were considered to be in the normal range.
Poppy yield responses to liming were attributed primarily to alleviation of aluminium toxicity but the effects on yield of reductions in soluble Al and increases in available Ca were confounded by application of ground limestone.