Agronomy Library > Soil Conservation

Crop Rotation and Tillage Effect After 20 Years of Sod (Wheat)
Author: M. A. Arshad, K. S. Gill, and R. E. Izaurraldne
Date Created: February 11, 1998
Last Reviewed: February 28, 2007

Document Source: Journal of Sustainable Agriculture. 12(2 - 3): 131 - 154

Summary
Soil properties of a silt loam (Dark Gray Luvisol), weed populations, and wheat (Triticum aestivum) production were compared under conventional tillage (CT) and no-till (NT) in field trials near Beaverlodge, Alberta, Canada. 
     
      Cropping systems studied were:
Canola (B. campestris) - wheat-wheat (C)
Fallow-wheat-wheat (F)
Field pea (Pisum sativum) -wheat-wheat (P)
Continuous wheat (W)

- Percentage of water stable aggregates (WSA) was reduced after a fallow season.
- Soil NO3-N was similar among cropped plots which was significantly lower than fallow plots in two of the three years. 
- Ammonium-N, extractable P and penetration resistance (PR) of soil was not affected by crop rotation.

- The W rotation plots tended to have more weeds than the both the first (W1) and second (W2) year wheat plots in other rotations.
- Wheat appeared to suppress weeds better than canola, field pea or fallow.

- Average annual production of 3.5 t/ha as grain and 10.7 t/ha as above round dry matter (AGDM) in W1 were significantly greater than the corresponding production in W2 and W.

- Two-year Wheat grain and AGDM production from C, F, P and W systems were not significantly different in most cases. However, cumulative yields in C, P and W systems for three years of rotation were greater than the corresponding grain (1.10 - 4.19 t/ha) and AGDM (4.3 - 8.7 t/ha) yields from system F.

- Tillage did not affect NO3-N, NH4-N, P and WSA in soil but reduced its PR.

- The NT system provided better control of annual broadleaf weeds whereas perennial weeds were better controlled by CT.
- The CT system produced more grain (average 0.42/t.ha per year) than NT system.
- Crop rotation by tillage interaction effects on soil properties, weed populations and crop yields were not significant, which indicated that crop rotations were equally effective under both tillage systems.

Benefits of crop rotation over monoculture in this study were of similar nature as in earlier studies conducted on fields already under annual cropping systems. Canola and field pea were more beneficial than wheat as previous-crop for wheat production. Replacing fallow with a crop increased crop production and straw returned to soil, reduced potential for leaching of NO3-N, and improved water stable aggregation of soil.