Soil aggregate stability increased with a self-regenerating legume cover crop in low-nitrogen, no-till agroecosystems of Saskatchewan, Canada

Abstract

Black medic (Medicago lupulina L.) is a self-regenerating cover crop which was tested for its ability to improve soil physical properties. Soil aggregate stability was assessed in plots that included a black medic cover crop in a no-till grain rotation, which was fertilized with two levels of nitrogen (N), for 15 yr. In the wheat phase of the rotation, the medic cover crop increased mean weight diameter by 21% in the reduced N fertilizer treatment but not in the recommended N treatment. Generally, the addition of medic reduced the proportion of small aggregates and increased the proportion of large aggregates. This pattern was stronger in reduced N compared with recommended N fertilizer levels. This study provided evidence for medic to increase aggregate stability under low external N input grain production.

Effects of Different Intercropping Methods on Soil Organic Carbon and Aggregate Stability in Sugarcane Field

“…Legumes such as soybeans and mucuna pruriens have well-developed root systems which can fix plants to absorb nutrients and water through soybeans. In the study of April Stainsby et al [38], legumes improved the stability of aggregates, which is consistent with the results of this study. In OW //M treatment, compared with legumes, watermelon has a weaker role of plant roots and a greater damage to soil stability.…”

Self‐regenerating black medic cover crop provides agronomic benefits at low nitrogen

“…This indicates a benefit of the self‐regenerating cover crop in terms of the water economy of the cropping system. Possible reasons for the increase in WUE with medic at the low N rate include greater grain yield (i.e., an increase in the numerator of the WUE equation; Table 11), less water loss to evaporation because of an increased thickness in soil surface residue with a cover crop (Thapa et al., 2021), and improvements in soil physical properties (Stainsby et al., 2020),…”

“…Another possibility is improvements in soil physical properties from the medic. For example, Stainsby et al (2020) observed an increase in macroaggregates in these medic plots and greater macroag- .…”

“…(2018) observed a significantly more diverse soil microbiome in the medic vs. the system without medic, while Stainsby et al. (2020) observed significantly greater soil aggregate stability with medic in the low‐N treatment with no effect at the higher‐N fertilizer rates. Turmel et al.…”

“…cropping system. Possible reasons for the increase in WUE with medic at the low N rate include greater grain yield (i.e., an increase in the numerator of the WUE equation; Table 11), less water loss to evaporation because of an increased thickness in soil surface residue with a cover crop (Thapa et al, 2021), and improvements in soil physical properties (Stainsby et al, 2020), The year × medic × crop interaction had a significant effect on WUE and accounted for 14% of the variance attributed to random effects (Table 9). The WUE of the crops tended to vary in a similar manner from year to year (Table 11), but the differences between medic and nonmedic was varied among the crops.…”