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Effect of plant age on the critical inorganic and total phosphorus concentrations in selected tissues of subterranean clover (cv. Trikkala)

1992; CSIRO Publishing; Volume: 43; Issue: 1 Linguagem: Inglês

10.1071/ar9920215

1444-9838

DC Lewis,

Plant nutrient uptake and metabolism

Subterranean clover (cv. Trikkala) was grown in field and glasshouse experiments to calibrate the critical concentrations of inorganic P in selected plant tissues, for maximizing vegetative growth. Critical concentrations of total P in the various tissues were also calibrated from the field experiment. Critical concentrations of inorganic P derived in the glasshouse, for both youngest open leaf (YOL) and next oldest leaf (YOL+1), were similar at any one sampling time, but declined markedly with plant age, i.e. critical concentrations for YOL declined from 196 mg kg-1 at the first sampling to 96 mg kg-1 1 month later. Similarly, critical inorganic P concentrations for YOL derived in the field declined with time, i.e. from 187 mg kg-1 to 124 mg kg-1 from the first to second sampling. Critical inorganic P concentrations for YOL+1 were less age dependent, though much lower at any one sampling time. As such, inorganic P is not recommended for diagnostic laboratory use. Critical concentrations of total P for YOL and YOL+1 did not decline significantly over the sampling period, while those for whole plant tops (WT) declined from 0.35 to 0.30% over the same period. In the YOL tissue, the proposed critical nutrient range for total P is 0.40-0.45% while that for WT, sampled early in the growing season, is 0.35-0.40%. Results from this study support the use of total P in diagnostic plant testing services.