New Thinking

FARMERS WEEKLY – farmersweekly.co.nz – March 22, 2021 29

Natives could boost crop yields

Plant & Food Research scientists have come up with some practical planting options to help farmers boost farm biodiversity and crop yields, proving that when it comes to pollination all the work does not have to be left just to the bees. Richard Rennie reports.

MODERN farming methods often look to reduce the number of insect populations in crops.

But a five-year trial in Canterbury has shown that greater numbers of certain insects not only control pests but deliver better pollination, and can be the key to higher crop yields.

Plant & Food Research scientist Dr Brad Howlett says their work on three farms found intensifying the level of certain native plantings could deliver improved pollination levels, with specific types of native plantings aiding specific crop types.

He and his research partner Dr Melanie Davidson were invited to submit their innovative work to the prestigious journal Advances in Ecological Research as part of the issue The Future of Agricultural Landscapes.

The issue showcases cuttingedge approaches to improving global agricultural systems into the future.

“There has been a lot of interest among farmers for quite a while on the role of different insects in crop pollination and pest control. We think our approach will allow them to better harness them,” Howlett said.

He says concerns NZ crops are not always hitting their full yield potential, despite apparently ideal conditions at times, have often been linked to lower than ideal pollination levels.

He believes that the incorporation of the correct native plants into farming systems could be worth at least $38.1 million a year to Canterbury farms alone.

“Carrots and white clover are two typical crops where yields can vary significantly year to year and be inadequate,” he said.

Research has shown white clover on average has the potential to double its yield if full pollination can be achieved.

White clover can earn $5-$7/ kg and carrot seed $10-$90/kg for high grade hybrid seed, making consistently high yields worth locking in.

Despite their well-earned reputation for hard work, bees are not always the ideal pollinators for some crops.

In the case of kiwifruit, the flower is second choice to more appealing options like white clover, while in some crops their movement may not be an ideal match because of the shape of the flower they are pollinating.

NZ doesn’t have the diversity of pollinating species, compared to countries like the United States and Australia.

But over the five-year trial the scientists identified 20 pollinating species out of 21 anticipated, confirming how effective the trial plantings were in attracting other pollinating players.

Perhaps surprisingly, a humble native fly can be particularly invaluable for some crops, even more so than wild bee populations.

Carrot fields, for example, benefited from the presence of fly populations.

“In the past, the numbers have been highly variable and pretty unpredictable. You may have planted a carrot crop and happened to have a population of native flies nearby, but not known that was what contributed to your good yield that year,” he said.

“On hybrid carrot plantings with rows of sterile and fertile male plants, bees learn to just stick largely to the fertile carrots, reducing the potential crosspollination.

“In contrast, the native drone flies were a lot more random in their movement, and made up for what the honeybees were not doing, almost an insurance.”

Attracting this particular species benefits from plantings that include cabbage trees, hebes, manuka and kanuka.

In contrast, a specific native Leioproctus bee species can be a good white clover crop pollinator, being able to open the closed petals of the flower.

It also moves more frequently between the flowers of plants than honeybees, which benefits pollination and seed yield.

The numbers of these bees were supported by plantings of a native broom species that exhibits a flower shape similar to that of the clover flower.

“This all proves very useful, practical information for farmers wanting to plant out what parts of the farm they can, or maybe intensify the plantings in areas they have done already,” he said.

The researchers are conscious their work has so far only focused upon Canterbury and even within that region, the blend of plantings could vary between the coast and the foothills, and the predominant crops grown on individual farms.

As the focus on high-value horticultural and seed crops grows, the scientists are anticipating increased interest in the work from growers across the country, and are keen to explore planting options in other parts of NZ.

“Avocados, for example, can have huge variations in pollination by bees,” he said.

“We have had a huge level of interest from across the community too, from farmers, conservationists and restoration trusts.

“This is a way to bring different land-users together and increase farm biodiversity to deliver better crop yields, and enhance New Zealand’s sustainable story at the same time.”

FERTILE: Plant & Food Research scientist Dr Brad Howlett says greater plantings of native species could be worth $38 million a year to Canterbury farms alone.

This all proves very useful, practical information for farmers wanting to plant out what parts of the farm they can, or maybe intensify the plantings in areas they have done already.

Dr Brad Howlett Plant & Food Research

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