May 24, 2011

For more than four decades, researchers from UNL and other institutions have studied the long-term effects of tillage on soil at the High Plains Ag Lab near Sidney.

Scientists with USDA’s Agricultural Research Service (USDA ARS) in Lincoln, Fort Collins, Colo., Akron, Colo., and Ames, Iowa, have worked on these plots, as have university scientists and graduate students from UNL, Colorado State University, Kansas State University, and Michigan State University. More than 45 scientific journal articles, nine book chapters, a research bulletin, and numerous scientific abstracts have been published from work conducted at these plots.

Now, a new chapter in long-term soil research is about to begin in these plots.

The plots are being transitioned to an intermittent tillage study, which will examine the effect of tillage on soil quality changes every six years. All treatments will be no-tilled in the years between plowing. In the year of plowing, half of each previous tillage treatment plot will be plowed and the other half will remain no-till.

Previously, the plots were cropped in alternate years to reflect the wheat-fallow rotation commonly used by farmers. The fallow plots received one of three treatments: plow, stubble-mulch, or no-till.

The new study will provide information on the long-term effects that occasional or intermittent tillage has on the soil.

USDA-ARS soil scientists are sampling the soil prior to initiating these changes. This will allow a summary of the effects of the last 40 years on soil quality while establishing initial soil conditions for the new study.

It will likely be 12 to 18 years before significant soil quality changes become evident. Long-term field studies, such as these, have provided valuable information on the long-term effects of agricultural practices on soil condition and function, as influenced by the ever-changing conditions of climate, weather, biological adaptation, and environmental, social, cultural, and technological considerations with time.

This information cannot be obtained from two- or three-year experiments, yet most research reported today consists of these short-term experiments.

Visionaries Establish Long-term Plots

The new long-term research project will be conducted on land that Charlie Fenster, retired extension dryland crops specialist, and Dr. Gary Peterson, a former soil scientist at UNL, used to study what happened when a native grass site was converted to cultivated land in a wheat-fallow system with conventional tillage. They were interested in following changes in total soil nitrogen when tillage is introduced.

These plots were established in 1970, and a sod treatment was maintained in each of three replicates to serve as a control. The sod treatment was not hayed or grazed, but grass was burned occasionally to reduce residue accumulation and promote growth of warm-season species. No fertilizer has been applied to these plots. Native fertility is still sufficient to support winter wheat yields 40 years after the plots were initiated.

Resources for Long-term Research Diminish

Funding long-term experiments has grown more difficult in recent years, leading to the closure of many long-term field experiments and preventing the establishment of new long-term experiments. The long-term tillage plots at the High Plains Ag Lab are a valuable resource that are growing increasingly unique. The vision and dedication of people like Charlie Fenster and Gary Peterson have paid rich research dividends for many researchers and farmers in the High Plains.

Drew Lyon
Extension Dryland Cropping Systems Specialist, Panhandle REC, Scottsbluff