Phosphorus response and efficiency of 12 novel dryland legume species on an acid high country soil

Abstract

High country soils are typically acidic and have low fertility compared with intensive high fertility low land systems. Pasture legumes commonly used in New Zealand perform poorly in these environments. The optimum soil P status for growth of many potential alternative legume species for this environment is unknown.

Twelve legume species were grown under glasshouse conditions at Lincoln University in an acidic high country soil (Ashwick stoney / boldery 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). Plants were harvested monthly post establishment and the yield 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 at the end of the experiment.

Phosphorus increased the yield of both annual and perennial legume species through the increase in plant available P. Optimum Olsen P for maximum yield differed between species as did P use efficiency. Persian clover was the highest yielding annual species (13.6 g DM pot⁻¹ ) followed by subterranean clover > arrowleaf clover > balansa clover, while gland clover was the lowest yielding annual species (1.2 g DM pot⁻¹ ). Lotus was the highest yielding perennial species (15.0 g DM pot⁻¹ ) followed by tagasaste > lucerne > Caucasian clover > falcata lucerne > strawberry clover, while white clover was the lowest yielding perennial species (8.2 g DM pot⁻¹ ). As a measure of P use efficiency, the Olsen P at which biological optimum (97%) yields were achieved varied between species, ranging from 21 mg L⁻¹ (tagasaste) to 174 mg L ⁻¹ (gland clover). Gland, balansa and arrowleaf clovers had the lowest P use efficiency, while tagasaste, white and Persian clovers had the highest. Arrowleaf, subterranean and balansa clovers gave the greatest increase in yield at low P inputs (100 mg P kg⁻¹ ). Further research using field trials is required to confirm these results under natural climatic and physical conditions.