Relative agronomic merit of fused calcium phosphate. II. Dry matter production and P yields of ryegrass (Lolium perenne L.) and barley (Hordeum vulgare L.) in pot experiments
1992
Otabbong, E. | Persson, J.
Three consecutive yields of dry matter (DM) and P in rye-grass and one of DM and P in barley sown after ryegrass were harvested from acid silt loam, clay, sandy loam and sandy clay soils that had been mixed with fused Ca phosphate (FP) or single superphosphate (SP) at the start of the trial. The relative agronomic merit (RAM) of FP was defined as an increase in the overall DM or P yield induced by FP and expressed as a percentage of the increase in overall DM or P yield induced by SP. The RAM values varied with soils and fertilizer rates. They were usually higher for DM yields than for the corresponding P yields. On average, RAM values were 56, 106 and 193% for DM yields and 31, 65 and 82% for P yields at P rates of 12, 36 and 108 mg P kg-1 soil dry wt, respectively. Hence, FP was a better fertilizer than SP in terms of promoting plant growth, whereas SP was superior to FP at increasing P yields. Both barley DM and P yields were significantly and positively correlated (P = 0.05, n = 64) with soil levels of resin-P, inorganic NaHCO3-P, organic and inorganic NaOH-P fractions extracted in sequence from samples taken before barley was sown.
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