Crop‐Pasture Rotation for Sustaining the Quality and Productivity of a Typic Argiudoll

Abstract

Inclusion of pastures in a rotation may reverse the effects of conventional cropping and tillage on soil degradation. We hypothesized that crop‐pasture rotations could be defined with a minimum pasture component and a maximum conventional cropping component to accomplish sustainable management. Soil organic carbon (SOC), light‐fraction carbon (LFC), microbial biomass nitrogen (MBN), and aggregate stability index (ASI) were measured in the surface 0 to 0.15 m of a fine, mixed, thermic Typic Argiudoll with 2% slope under a long‐term crop rotation experiment at Balcarce, Argentina. Treatments were continuous cropping and crop‐pasture (50:50 and 75:25) rotations. All seedbeds were prepared with conventional tillage. All soil quality indicators decreased with cropping and increased with pasture. Data for each variable were fitted to an exponential model to describe their variation in time. Soil organic C decreased 4.4 g kg⁻¹ in 6 to 7 yr under cropping and rose to the original level (37.2 g kg⁻¹) after 3 to 4 yr under pasture. Light‐fraction C, MBN, and ASI fell 0.9 g kg⁻¹, 39.0 mg kg⁻¹, and 43.9, respectively (97–100% of the estimated decline), after 7 yr under cropping, while they recovered to the values at the beginning of the cropping period (1.8 g kg⁻¹, 99.5 mg kg⁻¹, and 76.7, respectively) in a few years under pasture. Rotations including a maximum of 7 yr of conventional cropping alternated with a minimum of 3 yr of pasture would maintain soil properties within acceptable limits and meet the goals of sustainable agriculture under conditions similar to this experiment.