A comparison of establishment methods of permanent pasture into an undeveloped depleted tussock grassland : a dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Agricultural Science with Honours, Lincoln University

This research compared pasture establishment, with or without cultivation, with two drill types, Cross Slot or triple disc and with 0, 2 or 6 t ha ⁻¹ of lime in an herbicided, undeveloped depleted tussock grassland, at Lees Valley, Canterbury in autumn 2007. The objective was to identify the most cost-effective method of establishment. On the 2nd October, the cultivated treatment had total green dry matter production of 656 kg DM ha⁻¹, which was 2.25 times greater than the non-cultivated treatment of 292 kg DM ha⁻¹. Cultivation physically removed competing resident vegetation and resulted in greater mineralisation of nitrogen. The Cross Slot drill had total green dry matter of 542 kg DM ha⁻¹, which was 1.34 times greater than the triple disc drill of 406 kg DM ha⁻¹. The Cross Slot drill resulted in improved uptake efficiency of nutrients due to fertiliser placement. Total green dry matter production was 555 kg DM ha⁻¹ for 6 t of lime ha ⁻¹ and ~430 kg DM ha⁻¹ for 0 and 2 t of lime ha⁻¹. The application of 6 t lime ha⁻¹ increased soil pH by ~ 0.4 units. Pasture response was due to alleviation of A1 toxicity, increased plant availability of N and possibly Mo or a combination of these. Drill type and the rate of lime had no effect on plant population. By the 29th August ryegrass plant population in the cultivated treatment was 346 plants per m² which was 1.25 times greater than the non-cultivated treatment of 278 plants per m². Subterranean clover plant population was 66 plants per m². Ryegrass made up 40-67% of total green dry matter, subterranean clover 21-33%, white clover 3-6% and cocksfoot > 1.5%. The cultivated, the Cross Slot drill and the application of 6 t lime ha⁻¹ treatments compared with the non-cultivated, triple disc drill and 0 t lime ha⁻¹ treatments respectively reduced clover content due to an increase in ryegrass yield rather than a decrease in clover yield. Cultivation treatment and drill type affected the rate of ryegrass tiller appearance and therefore, tiller number per plant and per unit area. For the cultivated treatment, ryegrass tiller appearance between 500 and 1430 °C d averaged every 39 °C d compared with every 76 °C d for the non-cultivated treatment. For the Cross Slot treatment, ryegrass tiller appearance averaged every 44 °C d compared with every 63 °C d for the triple disc treatment. Increased tiller number plant⁻¹ possibly increased radiation interception, the driver of crop yield. The cultivation treatment had the greatest cost benefit due to the highest increase in production. The difference between cultivation treatments is likely to increase due to restricted growth in the non-cultivated treatment with weed invasion. The Cross Slot drill, while more expensive than the triple disc, was cost effective due to the greater production.