Seeding in Tight Grid Pattern Better than Rows?

Posted in: Farming     

A new agricultural study out of the University of Copenhagen is getting attention for its possibly game-changing implication: the planting system we’ve used since the Neolithic Revolution — that is, lining up seeds in rows — may be the wrong way to suppress weeds and maximize crop yields. 

According to the study published in Weed Research in January, in test-field experiments conducted in Colombia, planting corn crops in a tight grid pattern can allow plants to outmuscle even fast-growing intruders far more effectively. 

The study’s co-author, Jacob Weiner of the university’s Department of Plant and Environmental Sciences, believes large-scale implementation of such a system could dramatically reduce the need for herbicides in crops such as corn, grains and beans. His previous research has included a similar study on cereals.

For this latest experiment, conducted in 2012 and 2013, scientists compared three varieties of corn sown at three densities in two spatial patterns, a grid and in rows. The test fields were infested with Brachiaria brizantha, a loosely tufted perennial grass with short rhizomes used as feed but is a common weed of disturbed areas in the humid tropics and subtropics. According to the study’s abstract, researchers measured weed biomass one month after sowing and at harvest, and looked at grain yield at
harvest time. 

What they found was that on average, weed biomass was reduced by 72 percent in the first year and 58 percent in the second year — and grain yield was up, by 48 and 44 percent at the highest density in the grid pattern compared to standard sowing practices. 

In an email to AgAdvance, Weiner said he views the results as more evidence of the benefits of so-called High-Density Cropping Systems, “in which high yields in the short term are maintained, while sustainability — long term yield and or reduction in inputs — is greatly improved.”

He continued, “It doesn’t work for all crops,” he said, “but it works for the big important global ones.”

There are caveats, of course. For one thing, water is an issue. Weiner’s research has found that cereals can suppress weeds only when given enough water. (Fertilizer levels “seem less important.”) The second consideration is cost. Weiner’s suggested matrix requires additional seed at planting. In Denmark, however, farmers already pay a tax for using pesticides. He feels that in countries where cutting back on pesticide use is a policy goal, the cost of compliance may eventually make reconfiguring one’s planting pattern cost-effective. 

The same may be true as more weeds become resistant to herbicides. Indeed, spending more to implement a grid system could soon outweigh the benefits of using or developing more toxic herbicides. As well, organic farmers who currently rely on mechanical methods to control weeds might find less need for heavy machinery and fuel — at least in theory.

“I have seen a huge response to this research from all over the world,” Weiner reports. “Several farmers from the U.S. have written to me [to say ] that they would like to try it out. The challenge here is that some changes in machinery may be needed.” 

Specifically, coulters would need to be tweaked to reduce row spacing significantly — from 13 cm to around 5 cm for wheat, for example — something already possible with many machines. 

The way seeds are distributed within a row would also require upgrades, which would not be an issue with corn, but is an obstacle for wheat. However, Weiner says he’s spoken to agricultural engineers who assure him that the technology would not be difficult to create.

In the face of these considerations, Weiner emphasizes that the reward goes beyond just reducing herbicide use: “I am convinced that if the idea is further developed and combined with the appropriate crop rotations, herbicide application in cereals could be eliminated in many regions.”

Now that’s a trend worth following.

About the Author
Lila MacLellan

Lila MacLellan is a freelance writer and editor based in New York City. She is originally from Toronto and has lived in Vancouver, Sapporo, and Montreal.

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