Increasing home-grown forage consumption and profit in non-irrigated dairy systems. 2. Forage harvested

Abstract

A dairy farmlet experiment was conducted at Terang in south-west Victoria, Australia, over 4 years to test the hypothesis that a 30% increase in forage harvested per ha could be achieved in a production system that incorporated a range of Complementary Forages with perennial ryegrass (CF) compared with a well managed perennial ryegrass-only farmlet (‘Ryegrass Max’, RM). The CF farmlet included perennial ryegrass pasture (44% of the farmlet area on average over 4 years), but also incorporated oversowing perennial ryegrass with short-term ryegrasses (average 16% of farmlet area) to increase winter growth, tall fescue-based pasture (average 20% of farmlet area) to increase production in the late spring–summer period, a double cropping rotation (15% of farmlet area) based on winter cereal for silage production followed by summer brassica crops for grazing, and summer crops used in the pasture renovation process (average 5% of farmlet area). The RM and CF farmlets were stocked at 2.2 and 2.82 June-calving cows/ha, respectively and average annual nitrogen (N) fertiliser application rates (pasture only) were 141 and 153 kg N/ha, respectively. The total amount of forage harvested per year was generally less than predicted from pre-experimental modelling of both farmlets. However, the proposed target of a 30% increase in home-grown forage harvest per ha in the CF system compared with RM was exceeded in 2005–06 (+33%), with 21, 16 and 11% higher forage harvest achieved in CF in 2006–07, 2007–08 and 2008–09, respectively (average for all 4 years = 20%). Annual forage harvested in RM ranged between 6.5 and 8.9 t DM/ha compared with 7.9–10.3 t DM/ha in CF. Approximately two-thirds of the increased forage harvest in CF came from higher rates of pasture consumption per ha and one-third from the double cropping component of the system, although the performance of the double crop (mean annual production of 11.5 t DM/ha) was well below the expected 20 t DM/ha based on pre-experimental modelling. The higher per-hectare pasture harvest rates in CF were primarily due to increased perennial ryegrass pasture consumption achieved through higher stocking rates and efficient responses to higher N inputs from both higher fertiliser rates and additional supplementary feeding. In CF, the DM harvested from pastures oversown with short-term ryegrasses was lower than perennial ryegrass, while tall fescue-based pastures were similar to perennial ryegrass. Poor spring rainfall in 2006–07 and 2008–09 likely contributed to the lower than expected DM yields of tall fescue-based pasture and the summer crops within the double cropping component. Home-grown forage harvest rates can be increased by 11–33% above what is currently achieved by best industry practice with perennial ryegrass-only pastures using complementary forages but perennial ryegrass will remain a key component of the forage base for dairy production in southern Australia.