Soil Organic Matter Changes Over Twenty Years in a No-till Soybean-Winter Wheat-Grain Sorghum Rotation.

The predominant cropping systems in South Central Kansas have been continuous wheat and wheat-grain sorghum-fallow.  With either system tillage is usually preformed to control diseases and weeds.  In the wheat- sorghum-fallow system only two crops are produced every three years.  Other crops (corn, soybean, sunflower, winter cover crops and canola) can be placed in the above cropping systems.  For this research, soybean was added in the fallow year in the in the wheat grain sorghum fallow system. The research was conducted at the KSU South Central Experiment Field, Hutchinson on a Ost Loam Soil. The sites had been in conventionally tilled wheat for two years prior to starting the rotation.  The research utilized a randomized block design with a split plot arrangement with five replications.  The main plot was crop (soybean, winter wheat, and grain sorghum and the subplot six N levels (0, 28, 60, 84, 112, and 140 kg/ha).   Nitrogen treatments were broadcast applied as NH₄NO₃ prior to planting.  Soil test were taken at the onset of the research and throughout the research.   The data collected showed increases in organic matter over the years.