Effect of seed source and seed phosphorus concentration on the yield response of yellow serradella to superphosphate applications

Abstract

A field experiment at Medina, Western Australia, was designed to test whether seed produced at different locations and containing different phosphorus (P) concentration in the seed would change the relationship between yield and the level of superphosphate drilled with the seed. To produce the seed for the experiment, subsamples of the same source of seed of yellow serradella (Ornithopus compressus cv. Madeira) were grown at Medina and Esperance, Western Australia. Seed of the same size produced at each location, and containing 3 different P concentrations, was sown in the experiment at Medina. Three levels of superphosphate were drilled with the seed. Yields (of dried herbage and seed) were increased 2- to 4-fold as the amount of P drilled with the seed was increased from 5 to 40 kg P/ha. Although the Medina seed contained >0.40% P and the Esperance seed contained <0.40% P, plants grown from Esperance seed produced larger yields than plants grown from Medina seed for each of the 3 levels of P drilled with the seed; yield difference increased from about 14 to 70% as the level of P drilled with the seed increased from 5 to 40 kg P/ha. Higher P concentration in the sown seed increased herbage and seed yields by 35-70% when 5 kg P/ha superphosphate was drilled with the seed, and by about 616% when 40 kg P/ha was P drilled with the seed. Seed grown at Esperance produced larger yields for each seed P concentration than Medina seed; yield differences were about 30-90%. The P concentration measured in dried herbage and seed depended only on the amount of P drilled with the seed. It was unaffected by the P concentration in the seed sown, and for dried herbage, it was unaffected by where the seed sown was produced. However, for seed production, the relationship between yield and P concentration in the seed differed depending on where the seed was grown.