Grazing Management of Subterranean Clover (Trifolium subterraneum L. ) in South Island (New Zealand) Summer Dry Pastures A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University by Serkan Ates Lincoln University 2009 Abstract of a thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy Abstract Grazing management of subterranean clover (Trifolium subterraneum L. ) in South Island (New Zealand) summer dry pastures by Serkan Ates This study consisted of two sheep grazed dryland pasture experiments. Experiment l compared sheep production from 3-year-old cocksfoot based pastures grown in combination with white, Caucasian, subterranean or balansa clover with a ryegrass-white clover pasture and a pure lucerne forage. Sheep liveweight gain per head from each pasture treatment and the pure lucerne stand was recorded in the 2006/07 and 2007/08 seasons. The cocksfoot- subterranean clover pasture provided equal (381 kg LW/ha in 2006) or higher (476 kg LW/ha in 2007) animal production in spring and gave the highest total animal production (646 kg LW/ha) averaged across years of the five grass based pastures. However, total annual liveweight production from lucerne was higher than any grass based pasture mainly due to superior animal production during summer when lucerne provided 42-85% higher animal production than any of the grass based pastures. In Experiment 2, the effect of stocking rate (8.3 (low) and 13.9 (high) ewes + twin lambs/ha) and time of closing in spring on lamb liveweight gain, pasture production and subterranean clover seedling populations was monitored over 2 years for a dryland cocksfoot-subterranean clover and ryegrass-subterranean clover pasture in Canterbury. In both years, twin lambs grew ii faster (g/head/d) in spring at low (327; 385) than high (253; 285) stocking rate but total liveweight gain/ha (kg/ha/d) was greater at high (7.26; 7.91) than low (5.43; 6.38) stocking rate. Ewes also gained 0.5 and 1.5 kg/head at the low stocking rate in 2006 and 2007 respectively but lost 0.2 kg/head in 2006 and gained 0.3 kg/head at high stocking rate in 2007. Mean subterranean clover seedling populations (per m 2) measured in autumn after grazing treatments in the first spring were similar at both low (2850) and high (2500) stocking rate but declined with later closing dates in spring (3850, 2950, 2100 and 1700 at 2, 4, 6, 8 weeks after first visible flower). Seedling populations measured in autumn after grazing treatments in the second spring were also unaffected by stocking rate (low 1290, high 1190) but declined with later closing dates in spring (1470, 1320 and 940 at 3, 5 and 8 weeks after first flowering, respectively). The effect of stocking rate and closing dates in spring on pasture and clover production in the following autumn was similar to the effects on seedling numbers in both years. However, clover production in the following spring was unaffected by stocking rate or closing date in the previous year at the relatively high seedling populations generated by the treatments. This was presumably due to runner growth compensating for lower plant populations in pastures that were closed later in spring. Subterranean clover runner growth in spring may not compensate in a similar manner if seedling numbers in autumn fall below 500/m 2. Mean annual dry matter production from cocksfoot and ryegrass pastures grown with and without annual clovers pasture production ranged from 6.4 to 12.4 t DM/ha/y but stocking rate (8.3 vs. 13.9 ewes/ha) during spring did not affect annual pasture production. Pastures overdrilled with annual clovers yielded 23-45% more dry matter production than pastures grown without annual clovers. iii The study confirms the important role of subterranean clover in improving pasture production and liveweight gains of sheep in dryland cocksfoot and ryegrass pastures. Lowering stocking rate from 13.9 to 8.3 ewes/ha was a less effective method of increasing seed production of subterranean clover in dryland pastures although it did lead to increased liveweight gain per head. Keywords: cocksfoot, Dactylis glomerata , closing date, liveweight gain, Lolium perenne L., Medicago sativa L, seedling population, sheep grazing, stocking rate, subterranean clover, Trifolium repens, Trifolium subterraneum, Trifolium ambiguum L, Trifolium michelianum L. iv Acknowledgements From poultry to pasture, after studying a wide range of agricultural subjects for 14 years at four different universities, I am now finalizing my PhD thesis with this acknowledgement section with a grateful heart. Who would guess that I would meet with the Turkish Prime Minister at Lincoln University, get married to an Indonesian girl that I met at Christchurch Airport and become a father? First of all, I wish to extend my gratitude to New Zealand Education for funding my PhD study at Lincoln University. I sincerely thank Camilla Swan for her encouragement and support and Jane Edwards, the ‘magical touch’ who solved every problem with a smile on her face. I would like to express my gratitude to my supervisors Prof. Grant Edwards and Prof. Derrick Moot for their patience, encouragement, wisdom and guidance. Your names in this thesis make me so proud. It has been a privilege to be a student of yours. I humbly offer my deepest respect and appreciation to Mr. Dick Lucas who was able to convert a chook student to a pastoral scientist in only 12 months with his exceptional teaching ability and enthusiasm. I appreciate your guidance, friendship, encouragement and your input in this thesis. Special thanks to Malcolm Smith and Colin Pettigrew for offering their help beyond their duties. Your frindship is deeply appreciated and your professionalism is quiet inspiring. I would like to acknowledge the Field Service Centre staff, Keith Pollock, Kim Barnes, Alan Marshall, Don Heffer, Dave Jack, Dan Dash, Vonny Fasi, Merv Spurvay and Jenny Lawrance for their assistance. I am also grateful to Dr. Annamaria Mills, Dr. Hamish Brown, M. Ozgur Tongel, Dr. Racheal Bryants and Dr. Edmar Teixeira for their assistance and friendship. v To my fellow student mates Mike Cripps, Dave Monks, Tom Maxwell, Tomohiro Muraki, Shokri Jusoh, Martini Mohammad Yusoff, Tony Butler, Sideth Kang, Fiona Sinclair, Anthony Kellman, Zachariah Munakamwe, Mariana Pares Andreucci, Jens Richardon and James Kosgey, for the discussions and assistance. I would like to offer special thanks to George and Roberta Hill for their frienship and wonderful tea-time stories. To my friends Ugur Cam, Dr. Cihan Demirbas, Kerem Caliskan, Taner Basar, Dr. Leonardo Sambodo, Dewi Krisnayanti, Doris Klug, Eylem Kaya, Dr. Hamish and Mika Brown, Dr. Annamaria Mills, Rob and Yanti Dewhurst, Julian and Jeanny Idle, Aynur and Tony Rider, Iylia Yazmin, Nourah Riad and Saliha Akbas for never leaving me alone. To my parents and my siblings for the love in their heart and their unconditional support. To my beautiful wife, Yuana Parisia and my daughter Dilara Afife, for making me the happiest man in ‘Walnut Grove’. Finally, I humbly dedicate this thesis to the fallen heroes in Gallipoli (Gelibolu) and I thank God, the Almighty for everything that he granted to me. vi List of Abbreviations Abbreviation Description Units LTM long term mean PET potential evapotranspiration mm TDR time domain reflectometry LAI leaf area index dimensionless PSWD potential soil water deficit mm 2 R coefficient of determination SWC soil water content mm SWD soil water deficit mm Tb base temperature °C Tm maximum temperature °C To optimum temperature °C Tt thermal time °Cd SEM standard error of the mean LSD least significant difference SD standard deviation LW liveweight kg/head LWG liveweight gain g/head/d NIRS near infra-red spectroscopy CP crude protein g DM dry matter kg/ha ME metabolisable energy MJ/kg NDF neutral detergent fibre % DMD dry matter digestibility % ADF acid detergent fibre % DOMD digestible organic matter in dry matter % ASW argentine stem weevil vii Table of Contents Abstract ................................................................................................................................ii Acknowledgements .............................................................................................................. v Table of Contents..............................................................................................................viii List of Tables......................................................................................................................xii List of Figures ................................................................................................................... xiv List of Plates..................................................................................................................... xvii Chapter 1 General Introduction..........................................................................................1 1.1 Background Information ............................................................................................... 1 1.2 Research aim and objectives ......................................................................................... 3 1.3 Thesis structure............................................................................................................. 4 Chapter 2 Literature Review...............................................................................................6 2.1 Subterranean clover .....................................................................................................