Using Forage Quality Testing to Predict Nitrogen Replacement Value of Cover Crops
This work is being done in four studies; they are summarized below.
Work completed includes a study that examined the rates of nitrogen mineralization from five plant residues of varying fiber contents. This experiment was carried out at four temperatures (35, 55, 75 and 95 degrees F) under controlled conditions in a laboratory setting. Soil was mixed with the plant residues, maintained in a temperature-controlled chamber, and sampled at regular intervals to determine rates of N mineralization.
Also completed is a replicated field study near White Lake, SD that looked at the effects of cover crops planted after wheat on the following year’s corn yield in a no-till management situation. Treatments were five cover crops, one treatment of vertical tillage, and one control.
Work in progress includes a mesh bag study in which five plant residues of varying fiber contents were put in mesh bags, left on the surface of a field, and collected at two week intervals. This is being done to measure the rates of decomposition of the plant residues and relate these rates to the fiber contents of the materials used. Two replications of this study have been completed with the third replication still ongoing.
Also in progress is a bioassay in which grass is grown in pots containing soil and five plant residues of varying fiber contents. The growth of the grass is monitored for the duration of the experiment. This work is in its second replication.
The objective of the temperature study is to establish decomposition rates over a range of temperatures.
The objective of the White Lake study is to determine the amount of N that the cover crops supply to the following corn crop.
The mesh bag study is intended to provide data about the breakdown of plant material under field conditions.
The bioassay uses growing grass to capture N that is mineralizing from the plant residue. The amount of grass growth is an indicator of how much N is available for uptake.
Impacts and Contributions/Outcomes
South Dakota State University
Brookings, SD 57007