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Manure is a great source of nutrients, but recent studies show there is something even more magical about it. Read on to learn more about the importance of soil health to yield, the ways that manure can influence this and how the Nutrient Management Spear Program (NMSP) is investigating the relationship between microbial health, yield and climate resilience.

Soil is its own ecosystem, hosting numerous micro- and macro-organisms. For farmers, these organisms are very important because of their role in nutrient cycling in the soil. 

Microbial health has already been found to be tightly linked to soil health, but at NMSP, PhD student Gurpreet Kaur is going beyond the soil health measurements themselves, investigating the relationship between yield, climate resilience and soil health indicators. Kaur hopes her work will lead to a better understanding of how soil-health indicators can help farmers more effectively manage crucial nutrients, such as nitrogen, and identify barriers to production.

NMSP began the soil health project with two primary goals in mind. First, to help farmers and researchers get a clearer picture of what is happening below the ground. Second, to assist farmers in creating a diverse and active microbial environment — which supports the ecosystem above the soil. 

One of Kaur’s projects studies the effects of different levels of manure and nitrogen (N) fertilizer applied between rows of crops — known as sidedress application — on corn yield, forage quality, major soil health indicators and microbial biodiversity. 

In 2023, Kaur and her team collected soil samples from three different corn field trials in New York. The treatments in the trial included plots with and without spring manure application and plots with varying rates of sidedress N, as part of the New York Value of Manure Project. Samples were collected from two different depths — 0-4 inches and 0-8 inches — at three different points in the growing season: when the corn was planted, mid-season (pre-sidedress), and at harvest.

“We often see not just the nutrient benefits of manure but also a yield increase that cannot be explained by the nutrient content of the manure alone,” explained Quirine Ketterings, professor of nutrient management in agricultural ecosystems and NMSP leader. “Our focus with this project is to better understand how soil microbial communities are impacted by manure. We are also hoping to find soil microbial health indicators that can be connected to management practices such a decisions about nitrogen sidedress needs.”

“We often see not just the nutrient benefits of manure but also a yield increase that cannot be explained by the nutrient content of the manure alone.”

The first depth, 0-4 inches, was analyzed for microbial biomass using the microBIOMETER® soil testing kit, as well as for moisture, total carbon, ammonium and nitrate, and soil respiration. Kaur also collected subsamples and stored them in the freezer to be tested later for deoxyribonucleic acid (DNA) extraction and sequencing. In the future, Kaur and her team will analyze the samples from the second depth, 0-8 inches, for soil fertility parameters.

The microBIOMETER test kit allows Kaur to evaluate microbial biomass and fungal to bacterial ratios.  “Preliminary results for liquid manure showed microbial biomass reflected the manure history of the fields,” said Kaur. “We also found an increase from planting, to sidedress, to harvest for fields with no or less intense manure history.”

This project will continue in 2024 with the same overall objectives, while also studying the residual effects of prior manure application on yield, nitrogen needs and soil microbial health indicators. The study is funded by the Towards Sustainability Foundation, New York Farm Viability Institute, Hatch Grant, New York State Agriculture and Markets, New York State Department of Environmental Conservation, and Graduate Teaching Assistantship from the Department of Animal Science.

Madeline Hanscom is a writer for the Nutrient Management Spear Program.

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