Preliminary Results From Reduced Tillage Experiment

Written by Abbe Hamilton- Research Project Manager, Wallace Weed Lab Department of Plant Science, The Pennsylvania State University

How do you reduce tillage in an organic grain rotation? And why would you want to? Penn State researchers are exploring the tradeoffs of tillage frequency and intensity on grain yields, soil health, soil fertility, and weed and pest pressure as they analyze the results of their most recent organic cropping systems experiment, which ran from 2020 to 2024.

The project expanded on reduced tillage research conducted at the Russell E. Larson Agricultural Research Center in Centre County, PA over the previous decade. The latest three-year systems experiment sought to compare three corn-soy-wheat rotations: one which minimized tillage in the cover crop phase of the rotation using relay cropping practices, one that minimized tillage in the cash crop phase using a rotational no-till soybean sequence, and one that employed shallow, non-inversion primary tillage with a compact, high-speed disk prior to cash and cover crops (Fig 1). The study measured the different tillage regimes' impacts on yield and income, weed and pest pressure, and soil health. The research team, led by Mary Barbercheck and John Wallace, investigates reduced tillage practices in organic systems due to the potential for improved soil health and labor savings. Here are a few key findings.

Fig 1. The three corn-soy-wheat rotations trialed, with some overlapping cover crops displayed as blended colors. The numbers below the crop indicate the STIR value, a metric of tillage intensity for that segment of the rotation.

Many organic producers are interested in the use of a compact high-speed disk to incorporate residues, control weeds, and prepare seed beds. Our results indicate that use of the high-speed disk as the primary tillage tool led to a compaction layer 2-4 inches below the soil surface and heavier weed pressure compared to other systems. Corn yields in this system underperformed due to these factors, as well as partly due to a lower-biomass pre-corn cover crop (oat/winter pea/radish) that was chosen to ensure the high speed disk could terminate it. In the other treatments, a moldboard plow was used to incorporate a red clover/cereal rye cover crop prior to corn. Looking forward, the high speed disk may have a good fit as the primary tillage tool for establishing cover crops or small grains.

Fig 2. Yields in bushels per acre for each treatment and each crop in the study. Yellow bars are the no-till cover crop rotation, green bars are the no-till soybean rotation, and brown bars are the shallow till, high-speed disk-dominated rotation.

No-till soybean (rotational no-till, achieved by no-till planting soybean into roll-crimp cereal rye, and cultivating as-needed with a high residue cultivator) delivered similar yields to the other treatments, with substantially lower soil disturbance and labor costs. However, peak weed pressure was significantly higher than soybean tilled with a moldboard plow. The no-till soybean also required a later harvest and a later planting of winter wheat than its tilled counterparts, which led to a lower-yielding, weedier wheat crop in the following year. Identifying economically viable cash crops that can follow no-till soybean will be a critical step for more widespread adoption of rotational no-till soybean.

Fig 3. A ryegrass, crimson clover, and radish cover crop mix interseeded into grain corn at its last cultivation. Photo credit John Wallace.

The rotation that minimized tillage in its cover crop phases did so by interseeding an annual ryegrass/crimson clover/radish mix at the last corn cultivation and frost-seeding medium red clover into wheat and drill seeding cereal rye into red clover in late fall. This system had the lowest weed pressure of all three experimal systems, the highest yields across the rotation, but did not increase profits relative to other systems.

The research team will present results from this study at the PASA conference on February 5th, 2025, and will provide further content via Penn State Extension as they continue their analysis. Stay tuned for results comparing the long-term impacts of continuous annual crops with up to three years of a perennial (alfalfa/orchardgrass hay) crop.

The project was funded by a federal OREI grant.

Abbe Hamilton is a Research Project Manager at the Wallace Weed Lab in the Department of Plant Science at Penn State University. Email: avh111@psu.edu