Fertiliser management for higher productivity of established lucerne pasture

Abstract

Lucerne (Medicago sativa L.), a deep-rooted perennial legume forage, is a significant part of pastures, and is also grown in rotation with wheat to improve the yield and protein content of grains. Adequate supply of key nutrients is one of the important factors in higher productivity and sustainability of lucerne pastures. However, farmers mostly overlook the importance of nutrient management of established lucerne pastures, resulting in poor persistence, low productivity and weed invasion. The aim of this on-farm field study was to investigate the effects of the combined use of P, K, S and Zn and different sources of Zn on herbage yield, crude protein, nutrient composition, nitrogen fixation, weed invasion and persistence of an established (2 years old) stand of ‘Aurora’ lucerne pasture. A randomised block design was used to test ten fertiliser treatments. The combined use of P, K, S and Zn significantly (P<0.05) increased herbage yield (139% increase) over 2 years, nitrogen fixation, leaf-to-stem ratio, crude protein, nutrient composition (P, K, Ca, S, Zn concentrations), persistence and groundcover, and also led to significant weed suppression (weed biomass decreased from 53 to 69%). Of the three forms of zinc tested, zinc sulphate and zinc-coated single superphosphate proved superior to zinc oxide. The results suggest that nutrient management is essential for improved persistence, reduced weed invasion and higher sustainable productivity of established lucerne pastures, which is important for livestock production systems and overall profitability of farming systems.

Keywords:

• lucerne
• herbage yield
• nitrogen fixation
• nutrient composition
• persistence
• weeds invasion

Acknowledgements

This research was partly supported by Grains Research and Development Corporation of Australia. The author thanks Stan Lee (Farmer), Bill Davidson and John Paul (Technical Officers) and Rex Williams (Lucerne Breeder) for their help with this trial.