About This Project

This is a follow-up project to our first experiment.com project "How much fertilizer do we really need?" where it was difficult to find any response to phosphorus (P) or potash (K) fertilizer inputs, suggesting that, in a healthy, cover cropped soil, legacy P and K may be untapped resources, while economic nitrogen rates seemed to be lower than initially thought. Soil test P in our 40 plots is in the "High" range, so we will concentrate on the effect of nitrogen and potassium in this research.

Ask the Scientists

What is the context of this research?

In the last 3 years, we have observed “strange” behavior in the cover cropped fields we are monitoring. We see increases in pH where no lime is added and steady concentrations of soil test phosphorus (P) and potassium (K) where no commercial P and K were added (this includes other macro-and micronutrients). This is really exciting to us (but especially to our farmers!) it seems (1) that healthy soils and cover crops are excellent at recycling nutrients and that (2) there is an untapped resource of legacy P and K (and other nutrients) that farmers may be able to tap into. In addition, we see an increases in soil organic matter which portends increasing quantities of mineralizable nitrogen (Nmin) over time.

What is the significance of this project?

The production agronomy narrative says that only the chemical component of the top 6" of soil is relevant to the farmer (and that the farmer must accept low fertilizer use efficiencies). We have now believe that for healthy soils, this is an incomplete story that works to the farmer’s financial detriment. We want to have a visible, replicated experiment over the entire corn-wheat-soybean rotation (2 years) that takes a more holistic view of the resource (soils 0-24” and above-ground biomass). Our previous Experiment.com project’s lab notes support our other observations and we would like to build on that experience of understanding how a healthy soils perform. We hope to use these data to help farmers better understand their systems, bottom line - help farmers save big on fertilizer.

What are the goals of the project?

Our central goal is to see if we can economically grow corn, wheat and soybeans in a healthy soil with lower nitrogen, less (or even no) potassium and no additional phosphorus. We’ll measure this directly by monitoring yields and comparing fertilizer input costs and soil test data. We’ll try to explain our economic performance by measuring , plant (cash and cover crop) tissue biomass and concentrations, and our soil properties (soil respiration, organic matter, macro and micronutrients) at 0-6” but also between 6 and 24” over the course of these three growing seasons. We are also hoping to use these data to try to understand the magnitude of our legacy phosphorus and potassium resources and whether/how long farmers can tap into these in the future.