FACTORS ASSOCIATED WITH THE CRITICAL LEVELS OF PHOSPHORUS FOR THE ESTABLISHMENT OF FORAGE GRASSES: I. GREENHOUSE TRIALThe trial was carried out to study the growth of Andropogongrass (Andropogon gayanus var. bisquamulatus), and Guineagrass (Panicum maximum) grown in plastic pots, 5,5 dm3 in a greenhouse. The soil was a Red Yellow Latosol, a clay textured soil. Eight plants were grown in each pot. The factors evaluated were: soil fertility levels, time of phosphorus and lime application in relation to sowing, methods of single superphosphate application: incorporated into the soil or in bands. Six phosphorus levels: 0, 15, 30, 60, 90 and 150 mg dm-3 as band application and 0, 45, 90, 180, 270 and 450 mg dm-3 for incorporation into the soil were used. Soil samples were collected from the 5 cm top layer for analysis of available P, after harvesting the forages. Cutting was taken 41 to 54 days after sowing. Soil-P critical values for andropogongrass and guineagrass were 18 and 14 mg dm-3 for the band application or 70 and 43 mg dm-3 for the incorporation of the fertilizer into the soil. Soil liming and phosphorus application before sowing brought about higher critical level values. Soil fertility levels had no effect on critical levels.
Index terms
Andropogongrass; Andropogon gayanus; Guineagrass; Panicum maximum; forages; phosphorus; critical levels