Cover cropping - the way forward for horticulture

By: Anthony Wingard

Presented by

One cucumber grower saw a five-fold increase in yield value per hectare after taking on a practice from grain-growers, and new research from Hort Innovation says the change could transform the sector. Anthony Wingard reports.

Ryegrass cover cropping led to an increase in crop yield

Cover cropping is nothing new in the realm of agriculture.

But new research from grower-owned research and development corporation Hort Innovation suggests that what has been standard practice in grain production could lead to fresh results for fruit and vegetable growers.

Cover cropping is the act of growing a crop for the soil, rather than for harvest. In Australia, these crops might be barley or ryegrass, legumes such as alfalfa or broadleaf plants such as spinach.

These crops are allowed to grow to a point before being mulched and reincorporated into the soil between the planting and growing of harvest crops.

Horticulture, like most forms of farming, relies heavily on healthy soils to maintain sustainable operations and the increasing intensity and pressures of contemporary farming has placed pressure on soil integrity to keep the $3.8 billion vegetable market afloat.

In some ways, cover crops are enjoying a renaissance, with farmers across Australia rediscovering just how beneficial they can be – one grower saying ‘the advancements in cover cropping have been the most advanced single change in farming that I’ve seen in 30 years’.

For this reason, Hort Innovation supported a three-year study by Applied Horticultural Research into cover cropping in agriculture, assessing how the practice might improve soil health and make vegetable growing more efficient.

The study found several benefits for the process, including improvements to soil health and structure, controlling of soilborne diseases, reducing the risk of erosion and economically, provide a cost-effective alternative for farmers.

Looking at 14 different sites across six different states, the study found the abundance of biology in the soil increased, although results varied with regard to location, climate and species of crop.

Research scientist with Applied Horticultural Research Kelvin Montagu says cover crops will be highly beneficial to vegetable growers.

"Cover crops were a forgotten practice which is now being rediscovered," he says.

"What you can see is around a 27 per cent increase in the size or the abundance of soil biology. In terms of activity, we see different enzymes plus Co2 and there is a 20 per cent increase in activity [compared to tillage soil]."

The study indicated that two of the cover crops tested – ryegrass and Caliente Mustard, provided several benefits to the soil over a long-term trial and also resulted in a slight increase in yield.

Often, the best formula for cover cropping is a combination of cover cropping and rolled crimper as opposed to single tillaging.

In one instance, the yield of cucumbers which were grown following ryegrass cover cropping and without the use of herbicide resulted in nearly 19 tonnes per hectare of cucumbers and a gross income of $28,391/ha – compared to the same cucumber crop planted in a tilled field which yielded just 4t/ha and approximately $5500/ha.

 

Alfalfa was one of the cover crops tested, which adds nitrogen back into the soil

MG Farm Produce manager Darren Long says the change in practice has paid off.

"With controlled traffic farming, cover cropping and minimum tillage, we have seen our soil water infiltration and holding capacity increase, the soil becomes less compacted and more friable and yield increase, with plants showing more resilience to weather extremes," he says.

The benefits of cover cropping, it seems, aren’t just seen in the improved yields and subsequent gross income for farmers but also in the costs saved on fuel and machinery for tillaging, as Premium Fresh Tasmania farm manager, Deon Gibson, says.

"After crop covering, our horsepower, fuel and irrigation requirements are all reduced and our soil isn’t as tight and bashed down as we’re not trying to turn it into a plant crop in the next day," Gibson says.

"Your soil is a living organism, and you don’t want it to die, so you want to something growing in there and even if it’s a short-term cover crop you are still protecting it.

"Doing so in summer means you’re also not getting extremes with a 30-degree sun hitting the bare soil," he says.

Cover Cropping tips

Farmers opting to use cover crops should note different types of cover crops perform better in different regions of Australia’s varying climate, To maximise the benefits of the crop and reduce potential diseases, they should also consider whether cover crops are suited to cool or warm seasons.

Ryegrass – a cool weather crop – is perhaps the most common cover crop given its cheap price and the quick time it takes to establish ground cover. Rye performs well in terms of recovering nutrients, suppressing weeds and can add between 3-10t/ha of biomass to the soil.

Summer grass crops such as Sorghum, Sudan grass, or a combination of both, also recover nutrients and supress weeds but given their ability to thrive in the heat, can tolerate extreme heat and drought as well.

Legumes such as the faba bean (cool) and lablab (warm), unlike grass cover crops, are extremely beneficial in adding nitrogen levels to the soil but often are slow to establish themselves in achieving ground cover – a problem when trying to outcompete weeds in the field.

Broadleaf cover crops such as buckwheat (warm), fodder mustard and oilseed radish (both cool), add high levels of biomass to the soil and like grass crops, also recover nutrients and supress weeds.

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