Changes in mouldboard plough draught and tractor fuel consumption on continuous corn after 18 years of organic and inorganic N amendments

It is well documented that organic N amendments helps to increase soil organic carbon and improve other soil properties, and some reports also show an accompanying reduction in energy for tillage for short term application of organic N amendments. The influence of soil inorganic and organic N amendments on soil organic carbon is complex and long-term effects on energy for tillage are unknown. A field experiment was conducted where inorganic and organic soil N amendments consisting of none, inorganic fertilizer at 100 and 200 kg ha−1 N, and stockpiled manure (SM) and rotted manure (RM) each at 50 and 100 Mg ha−1 (wet weight) were applied annually to continuous corn for 18 years. Mouldboard plough draught and tractor fuel consumption measurements were made during annual fall tillage in selected years. The organic amendments significantly reduced both mouldboard plough draught and tractor fuel consumption compared to inorganic N fertilizer or no amendment with the rotted manure showing larger reduction than stockpiled manure at the same rate, and higher manure rates showing greater difference than lower manure rates. There was a general trend for an increase in the difference with time. After 18 years, plough draught and tractor fuel consumption for the 100 Mg ha−1 RM treatment were 41 and 22 percent respectively less than the no amendment treatment. Decaying exponential models predict that about 80–94% of the maximum change in draught has occurred after 18 years of annual N amendment application.

► The organic amendments significantly reduced tillage energy.
► Rotted manure had a larger effect than stockpiled manure.
► The difference in tillage energy among amendments increased with time.