New guidelines reflect benefits of no-till farming

Soil fertility | North Dakota university is the first in the U.S. to adopt new corn recommendations

A quiet agricultural revolution is underway in North Dakota.

The change is hard to detect because it’s happening in the specialized field of soil fertility.

This summer, North Dakota State University unveiled new soil fertility recommendations for corn, which is planted on 3.85 million acres across the state.

The 11-page guide makes it clear that no-till soil is distinct from tilled soil. NDSU experts say farmers with fields dedicated to continuous no-till, for six years or longer, need 40 to 50 pounds less nitrogen per acre to grow corn than producers with tilled fields.

The recommendation is revolutionary because NDSU is the only land grant university in the U.S. that has adjusted its corn fertility recommendations to account for the benefits of zero tillage and conservation agriculture.

The corn guidelines echo an earlier NDSU recommendation for spring wheat and durum, which gave a 50 lb. nitrogen credit for long-term no till practices.

Jill Clapperton, a soil consultant in Montana and former Agriculture Canada scientist in Lethbridge, said what’s happening in North Dakota is unprecedented.

“That is a really huge deal,” said Clapperton, who’s known for her expertise in the rhizosphere, which is the region where the plant roots interact with the soil.

U.S. land grant universities have developed soil nutrient recommendations in their individual states for decades. The guidelines aren’t etched on tablets but many U.S. farmers believe they are gospel, Clapperton said.

“When you get your soil test results and you’re in Idaho, it’s based on the recommendations set by the land grant universities. And nobody goes against them.”

Kristine Nichols, chief scientist with the Rodale Institute, an organic agriculture research centre in Pennsylvania, agreed the new NDSU guidelines are significant.

“It’s fallen on the land grant universities to provide new (soil fertility) standards based on conservation agriculture practices,” said Nichols, who was a U.S. Department of Agriculture soil microbiologist in North Dakota.

“It was a very big step NDSU (took), in making those recommendations.”

Dave Franzen, NDSU extension soil science specialist, led the effort to develop the new recommendations. Instead of simply telling no-till farmers to use less nitrogen, Franzen has created tables according to the price of nitrogen and the market price of corn. He has developed tables for conventionally farmed soil and others for long term no-till soil, depending on geography and soil productivity.

Franzen said the recommendations are based on analysis of no-till data in North Dakota that goes back to the 1970s.

“I started working on it in 2005 and we gathered another 50 to 60 sites,” he said.

“No preconceived ideas. I just divided the sites into those that I knew were on a long-term no-till and those that I knew were conventional.”

Franzen was surprised by the results.

“If you look at a certain yield and the nitrogen it took to produce it in a no-till (system) … it took about 50 lb. of less N with the long-term no-till.”

Franzen said zero till combined with a diverse crop rotation enhances soil biology, which might explain the need for less nitrogen on no-tilled fields.

Clapperton was more absolute. She said improved soil biology is definitely the reason why no-till fields require less nitrogen.

“It’s very clear from NDSU’s data and data from various universities that work on no-till … showing we’ve got a lot more nutrients in the no-till soils,” she said.

Zero tillage and the associated increase in biological activity boosts the amount of nitrogen stored in the soil, she added.

“It’s like putting fertilizer in the bank because it (nitrogen) is bound in this organic form, which can be released later … which means (it) can then be turned into, through a process of mineralization, to an inorganic form that the plant can take up.”

Clapperton said the same process occurs in tilled fields, but there is significantly more biological activity in no-till soil. As a result, no-tilled soil can supply more nitrogen to the crop.

“With this much microbial activity in your soil and this much organic carbon … this is the potential of your soil to supply X amount of nitrogen.”

Nichols said the recommendations are an endorsement of a burgeoning agricultural movement in North Dakota, where zero tillage, cover crops and diverse rotations have become cornerstone values on many farms.

“There are people who are really excited … that (NDSU) has come out with these recommendations,” she said.

“Having worked with Manitoba-North Dakota Zero Tillage Association … it’s always been a big part of their meetings to (see) how can we get new standards. They (the recommendations) weren’t keeping up with what we’re seeing in our systems.”

Nichols said it’s difficult to know if other land grant universities will follow North Dakota’s lead. Change is often slow at such institutions, and conducting the necessary studies may not be a priority.

“I think that’s been one of the biggest impediments to getting new fertility standards,” Nichols said.

“We don’t have the funding and capital to re-evaluate for conservation agriculture.”

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