Second year yield and composition of pastures sown on four dates with five rates of ryegrass: A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science with Honours at Lincoln University

High animal productivity is associated with pastures that contain at least 30% dicotyledonous species. In this study the effects of sowing date (4/2, 24/2, 19/3 and 9/4/97) and ryegrass sowing rate (0, 4, 8, 12, 16 kg ha⁻¹) on the total dry matter and botanical composition of a two year old pasture were examined. The total dry matter produced from 13/10/97 to 28/8/98 was similar regardless of sowing date (16640 kg DM ha⁻¹), but highest from the 4 kg ha⁻¹ sowing rate (18460 kg DM ha⁻¹), and lowest from the no ryegrass sowing rate (14720 kg DM ha⁻¹). A pasture containing 30% or more chicory/white clover was only achieved in summer from sowing on 4 February with 4 kg ha-1 of perennial ryegrass. Ryegrass sowing rates greater than 8 kg ha⁻¹ produced a maximum of 15% chicory/white clover in the pasture and generally, this declined for the later sowing dates. The lack of dicotyledonous species in this second year was related to 1.) poor initial establishment because of a high base temperature of chicory (measured at 5.2 °Cd) and poor maximum germination at low temperature; and 2.) low root reserves of the chicory plants that were either sown late or with more than 8 kg ha⁻¹ of ryegrass. To maximise the chicory/white clover content in the first year of autumn sown pastures, sowing before soil temperatures drop below 14 °C, with less than 8 kg ha⁻¹ of perennial ryegrass is recommended.