High phosphorus concentration in Trifolium balansae and Medicago polymorpha seed increases in herbage and seed yields in the field

摘要

Seed of Trifolium balansae and Medicago polymorpha, of the same size (mean ± s.d., T. balansae 0.8 ± 0.01 mglseed, M. polymorpha 3.6 ± 0.05 mg/seed) but with increasing phosphorus (P) concentration in the seed (T. balansae 0.34 to 0.63% P, M. polymorpha 0.40 to 0.64% P), were sown in field experiments as singlestrain, dense, ungrazed swards on 2 different soil types (a sand and a lateritic gravel sand) in south-western Australia. Different amounts of superphosphate were drilled with the seed (5-40 kg P/ha for the sand, and 15-100 kg P/ha for the lateritic gravel sand). Increasing P concentration in seed increased yields of dried herbage measured at each harvest, and also increased seed yields (measured for M. polymorpha only). Increasing P concentration in the seed increased the effectiveness of superphosphate drilled with the seed, so that less fertiliser was required to produce the same yield as P concentration in the seed increased.