Summer forage options trialled

C4Milk works closely with Queensland and NSW dairy farmers on implementing various management strategies aimed at reducing feed-related costs while optimising feed quality and quantity.

As an extension of the successful Winter Forage Combination trial in 2019, the summer combination trial also looked to improve the protein value of starch-based silages and to find improved sorghum varieties for silage to reduce producer reliance on purchased concentrates.

Collaborating with a number of seed companies, C4Milk presented the large-scale demonstration site at an industry field day during March.

There were 45 plots planted comprising of various summer legumes and legume/cereal combinations, forage sorghums and specific grain sorghum varieties selected as potential silage alternatives to white grain sorghum.

The trial plots were grown under both irrigated and dryland conditions to demonstrate relevant results across industry and varying seasonal conditions.

The day attracted more than 60 attendees and more than half of the farmers attending reported they learnt a lot regarding sorghum varieties and are now considering grain sorghum as an alternative option for silage.

Under irrigated conditions, the Graze-n-Sile forage sorghum and Ebony cowpea combination achieved the highest yield from a single harvest (17.8 tonnes dry matter/hectare) closely followed by white grain sorghum (Liberty)/Ebony cow pea (17t DM/ha) and the forage sorghum/lablab (16.9t DM/ha) combinations.

Although the white grain sorghum combination had a slightly lower yield, it showed improved quality and comparable cost of production, as outlined in Table 1.

Unfortunately, all cereal combinations containing soybeans and burgundy beans performed poorly (not reported) due to nutrient toxicity issues with the irrigation water, an outcome suggesting they are nutrient-sensitive.

Monocultures were also investigated under irrigated and dryland conditions, where numerous varieties of grain and forage sorghums were compared.

Previous years of C4Milk research has found despite most red varieties containing higher overall starch concentrations, white sorghum has the highest amount of starch digested at seven hours (20 gram/hour).

However, with high demand and variable seed production, C4Milk continues to investigate other red and pink varieties that may be just as digestible as the white varieties (results yet to be published).

Interestingly, the irrigated Liberty (white grain sorghum) out yielded the Graze-n-sile (forage sorghum) crop by 20 per cent with a second and possibly third cut still to be taken.

Further, a NuSeeds grain sorghum variety that has a pink grain was found to have significantly higher quality than Liberty and will be further investigated in relation to its digestibility factors.

A key message to farmers and industry from the irrigated results is that grain sorghum silage can be a cheaper alternative to corn silage with similar nutritive value and yields, particularly in times of reduced rainfall and irrigation supply.

As expected, the dryland plots showed lower quality across all blocks, however, there were still some surprising findings.

Table 2 outlines the yield and quality of some of the combinations, where many individual varieties showed higher yields.

Interestingly, the grain sorghum Liberty/cowpeas and the forage sorghum Megasweet/cowpeas combinations yielded 7.5 -8t DM/ha both achieving 2t DM more than the single crop of the grain or forage varieties.

The dryland combinations were also better suited to direct chopping for silage, showing higher dry matters ranging from 31.5pc to 37.3pc, than the irrigated combinations showing a lower range of 25.6pc to 35.2pc.

Table 1 and 2 also highlights the increased expense of dryland crops due to the lower yields - however reasonable yields and costs can still be achieved across multiple harvests.

Of the monoculture plots comparing grain sorghums, Pacific Seeds red grain sorghum, Sentinal, yielded well at 12.3t DM/ha with NuSeeds pink grain sorghum also yielding highly with 10.4t DM/ha from single cuts.

Not only can legume and cereal combinations as well as alternative or new monoculture varieties improve feed quality and yields reducing MOFC, there are other flow-on benefits.

Homegrown legumes can be a low-cost addition of protein to all classes of stocks diets, as well as the soil health benefits that can be achieved.

As feed-related costs remain the single largest expense for dairy farmers, C4Milk will continue to investigate and refine low cost, high-quality feeding strategies to help improve farm profitability and resilience.