Tissue testing for assessing the phosphorus status of green panic, buffel grass and setaria

Abstract

The possibility of using phosphorus concentrations in different parts of pasture grasses for diagnosing their phosphorus status was studied. Critical phosphorus concentrations using youngest expanded leaves of green panic (Panicum maximum var. trichoglume cv. Petrie), buffel grass (Cenchrus ciliaris cv. Biloela), or setaria (Setaria sphacelata cv. Nandi) were found to be almost identical to those assessed from the whole tops. Critical phosphorus concentrations in green panic and setaria decreased with age of plant, and for whole tops of green panic were : 0.55 per cent in plants with three to four leaves on the primary shoot, 0.32 per cent in plants with four to five leaves on the primary shoot and 0.1 5 per cent in plants with six to seven leaves on the primary shoot. Values in the whole tops of setaria were: 0.46 per cent (four leaves), 0.36 per cent (five leaves), 0.24 per cent (six leaves) and 0.14 per cent (seven leaves). A similar decline with stage of growth was observed when youngest expanded leaves were used to estimate critical phosohorus concentrations in setaria