Integration of Tillage, Fertility, and Crop Rotation in a Cropping System.

Production agriculture in North Dakota has a strong characteristic if diversified crops.  Diversified cropping systems could minimize farming risk, provide sustainable production, and increase environmental conservation.  To examine the benefits of cropping systems the North Dakota State University Carrington Research Extension Center initiated a long-term cropping system in 1987.  The goal of the study is to determine the effects of tillage system, N fertility level, and crop rotation on crop yield and quality, biomass production, and changes in soil quality.  Hard red spring wheat, soybean, sunflower, barley, field pea, canola and corn were planted in three different four-year crop rotation in conventional-, minimum-, and no-tillage systems.  This report is an overview of the fifth cycle of the study which occurred from 2003 through 2006.

Grain production of all crops was greatly influenced by year, which provided significantly different environments including precipitation, temperature, and diseases pressure, except sunflower and field pea which had relatively consistent yields through out the study period.  Oil content ingrain tended to be affected by year more than grain protein content.  The year affect had a similar pattern on all crops biomass production as well.

Tillage system had a significant impact on grain yield, but not grain quality.  In general, grain yields of all crops were significantly lower in the no-till system than the conventional- and minimum-tillage systems. The exception was soybean which had a significantly higher yield in no the no-tillage system than the conventional- and minimum-tillage systems.  Biomass production had a similar pattern to grain yield and grain quality was not affected by tillage system.

Grain and biomass yields of non-legume crops responded to increased N fertilization up to 90 kg/ha except hard red spring wheat, which had the highest yield at 45 kg/ha and manure application had similar affects as chemical nitrogen fertilizer application on grain and biomass yield.

Soil quality parameters were significantly changed by tillage systems and fertilization.  This study shows that crop rotations with more three or more different crop types did not have a negative impact on soil quality.  Soil organic matter and phosphorous at the 0 to 15.24 cm depth was highest in the not-till system and soil nitrogen at the 0 to 15.24 cm depth was not different among tillage systems.  However, soil nitrogen at the 30.48 to 60.96 cm and 60.96 to 121.92 cm depths were significantly lower in the no-till system.  Higher soil nitrogen in the subsurface soil was associated with increased nitrogen fertilization.  These results show the potential for nitrogen leaching with increased fertilization and tillage.  Manure application based on N rate increased both soil organic matter and phosphorous in the soil surface.