The resource gradient experiment is a long-term study to investigate nitrogen and water constraints on crop yield. Main Cropping System Experiment (MCSE) annual crops (corn, soybean, or wheat) are nitrogen-fertilized at 9 different rates and either irrigated or rainfed. Corn was grown from 2000-2005 and subsequently the crop rotation (wheat, corn, soybean) followed the crop of the LTER main site. Fertilizer rates differ by crop; for corn the range has been 0 to 292 kg N ha-1 and for wheat 0 to 180. Soybeans are normally not fertilized; in 2012 (only) soybeans were fertilized at 0 to 146 kg N ha-1.
Irrigation applied is sufficient to meet plant water needs as predicted by weather and a crop growth model that estimates evapotranspiration. A linear move irrigation system applies water 0–3 times per week during the growing season depending on recent rainfall and crop need.
The experiment was moved to its current location on the LTER main site in 2005.
Download experiment location history map.
Lysimeters (soil water samplers) are installed in various plots. Download lysimeter locations.