Agronomy Library > Soil Conservation

Crop Rotation and Tillage Effects (Quackgrass control; soil quality; crop nutrition)
Author: Y. K. Soon, and A. L. Darwent
Date Created: February 10, 1998
Last Reviewed: February 28, 2007

Document Source: Journal of Agricultural Science. 130(3): 323-328

Summary
The effects of suppressing couchgrass [Elytrigia repens (Elymus repens)] through integrated management, on soil biological quality and N and P nutrition of barley were evaluated in a field experiment (1987 - 92) on a dark grey soil in Alberta, Canada.

The management practices (treatments) were combinations of:
- herbicide applications (0.45 or 0.9 kg/ha glyphosate or 0.1 kg quizalofop)
- crop rotations
- tillage treatments

The 3-year crop sequences were:
- continuous barley
- canola - barley - barley
- fallow -barley - barley
- barley or canola undersown with red clover (Trifolium pratense) - red clover green manure - barley

 In 1992, the sixth year of the experiment, soil and plant samples were analysed for nutrient content.

Treatments that consisted of spring and fall tillage only did not suppress couch grass and produced low barley yields and N and P uptake. More N was immobilized in couch grass shoots and rhizomes and soil microbial biomass with these treatments than with similar herbicide-treated crop rotations. Tillage-plus-herbicide treatments effectively suppressed couch grass and enabled the barley crop to compete for soil N, but both spring and fall tillage were required for weed control.

The fallow treatment impaired soil quality by reducing soil and microbial C and N, but produced similar barley yields as continuous cropping with tillage-plus-chemical control.

Red clover (ploughed in for green manure) enhanced soil quality indicators such as soil and microbial biomass C (carbon sequestration), total and mineralizable soil N, and microbial N, but did not increase barley yield compared to continuous grain cropping.