Megan H. Ryan1, Daniel Kidd1, Hayley Norman2, Kevin Foster1, Hans Lambers1, Dion Nicol1,3
1 The University of Western Australia, 35 Stirling Hwy, Crawley (Perth), Western Australia, 6009, email@example.com
2 CSIRO, Underwood Ave, Floreat (Perth), Western Australia, 6014
2 Department of Food and Agriculture Western Australia, Merredin, Western Australia, 6415
Pasture soils of the Peel Harvey coastal plain of Western Australia have been greatly enriched in phosphorus (P), but less so in nitrogen (N), sulphur (S) and potassium (K). To determine whether pasture legume cultivars differ in susceptibility to deficiencies of N, S and K when grown on soils high in P, we grew six annual and one perennial pasture legume cultivar, as well as annual ryegrass (Lolium rigidum), on a dairy farm. Six nutrient treatments were established (Nil, +P, +N, +SK, +NSK, All). Shoot dry weights (DWs) did not differ between the Nil treatment and the +P, +N, and +SK treatments for any cultivar. However, while shoot DWs of Trifolium cultivars were 2–3 fold higher in the +NSK and All treatments compared with the Nil treatment, shoot DWs of Ornithopus cultivars did not differ among treatments, despite having similar DWs to the highest yielding treatments for the Trifolium cultivars. Forage quality parameters (dry matter digestibility and crude protein) were high for all legume cultivars and were slightly improved in the All treatment compared with the Nil treatment. We conclude that many pastures in the Peel Harvey region may not require P fertiliser to maximise yields, but instead may respond to the addition together of N, S and K. Further, we suggest that the root systems of Ornithopus genoptypes are better at accessing limiting soil nutrients than current commonly grown pasture legumes, likely due to a greater ability to explore soil.