Response of 12 pasture legumes to phosphorus and lime additions when grown in a high country soil under glasshouse conditions : a dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Agricultural Science with Honours at Lincoln University

Abstract

Legumes are the main source of plant available nitrogen in high country pastures through nitrogen fixation. High country soils are typically acidic and have low fertility compared with intensive high fertility low land systems. Therefore the legumes commonly used in New Zealand perform poorly in these high country environments. The optimum P and pH status for growth of many potential alternative legume species for this environment are unknown. Twelve novel legume species were grown for a period of 42 weeks under glasshouse conditions at Lincoln University in an acidic high country soil (Ashwick stoney / bolder silt loam) from the Lees Valley (North Canterbury). Phosphorus was applied at eight rates (0, 10, 30, 60, 100, 250, 500, 1500 mg P kg⁻¹ soil) while lime (100% CaCO₃) was applied at five rates (0, 2, 5, 8, 15 t ha⁻¹ equivalent). Plants were harvested monthly post establishment and the yield was determined. Annual species grew on average for 25 weeks, while perennial species grew for 42 weeks. Herbage was analysed for macro and micro element content and uptake. Soils were analysed for available P content and pH at the end of the experiment. The optimum Olsen P and pH level for maximum yield has been identified for these 12 legume species. For many species examined in this experiment, this represents new and valuable information. The practical implications of the results are discussed. Further research using field trials is required to confirm these results under natural climatic and physical conditions.