Critical P, K and S Concentrations in Soil and Shoot Samples for Optimal Tedera Productivity and Nodulation

Tedera is a forage legume that can provide out-of-season green feed in Mediterranean climates. To date, growers have had no comprehensive soil nutrition guidelines to optimise tedera production. We undertook field and glasshouse studies to understand tedera's macronutrient requirements. Three field experiments were sown with tedera cv. Lanza (R) at Cunderdin, Dandaragan and Three Springs in Western Australia. These experiments evaluated seven levels of phosphorus (P) (0-30 kg ha(-1)) and potassium (K) (0-80 kg ha(-1)) and two combined treatments with P and K. Glasshouse pot experiments were conducted using tedera cultivars Lanza (R) and Palma and lucerne cultivar SARDI Grazer. Ten concentrations of added P (0-256 mg kg(-1)), ten of K (0-256 mg kg(-1)) and ten of sulphur (S) (0-16 mg kg(-1)) were tested. There was no significant response to P or K in field soils at Cunderdin or Three Springs. There was no response to K at Dandaragan, but P produced a positive response in the July and October growing season cuts. In the glasshouse, tedera cultivars reached peak productivity at lower soil Colwell P (7.6 to 12 mg kg(-1)) than lucerne (22 mg kg(-1)). Lanza (R) had a moderate biomass response, and Palma did not show a significant response to Colwell K (0.8 to 142 mg kg(-1)) or soil S (1.3 to 12.5 mg kg(-1)). Nodulation was greatly reduced at the extremes in P and K treatments. For the first time, these field and glasshouse results have allowed us to establish guidelines for optimal soil nutrition for tedera that growers can use to benchmark the soil or shoot nutrient status of their tedera pastures and assess the economic benefit of correcting deficiencies.