Eight years of crop rotation and tillage effects on crop production and N fertilizer use

Although tillage systems and crop rotations can affect crop production and uptake of nutrients, their long-term effects, particularly their interactions, are not well-documented. Therefore, we measured the N, P, and K contents and yields of crops through two rotation cycles, especially wheat (Triticum aestivum L.), of four crop rotations managed under conventional tillage (CT) and no-tillage (NT) systems. The study was conducted 1993 through 2000 on a sandy loam soil in northwestern Alberta, Canada. The four-course crop rotations were: (i) field pea (Pisum sativum L.)-wheat-canola (Brassica rapa L.)-wheat; (ii) red clover (Trifolium pratense L.) green manure-wheat-canola-wheat; (iii) fallow-wheat-canola-wheat, and (iv) continuous wheat (CW). The crops were fertilized using regional recommendations based on soil test results. Previous crop effect on wheat yield was in the order: field pea = red clover green manure > fallow > canola > wheat (CW); it had little influence on N, P or K content in wheat grain o...