Long-term observations in contrasting crop-pasture rotations over half a century: Statistical analysis of chemical soil properties and implications for soil sampling frequency

摘要

Continuous agriculture (CA) has led to sustainability problems linked with production decreases, environmental contamination, crop failure and soil degradation in many regions of the world. Crop-pasture rotations (CPR) are management alternatives that contribute to environmental sustainability and productive diversification. Long-term experiments (LTE) play a major role in evaluations of the impact of different management practices on soil quality. However, the results can be misleading if the data are not adequately analyzed. A unique dataset of annual soil samples from a 55-year-old LTE was used 1) to evaluate the effects of a crop-pasture rotation on soil quality and crop productivity and 2) to provide robust statistical models to measure long-term changes in chemical soil quality parameters. Treatments were seven rotations, including CA or CPR with different proportions of pasture in the system (33%, 50%, or 66%). Soil organic carbon (SOC), total nitrogen (N-tot), exchangeable potassium (K) and soil pH have been determined annually since 1964, and the cumulative treatment effects were analyzed. Correlation structures showing the variance heterogeneity for the study years were tested for each parameter and condition. The longer the duration was of the pasture in the rotation, the slower the degradation was in the chemical soil quality. The CPR made a key contribution to sustainable agricultural diversification and intensification, leading to 30% higher crop yields and 19% and 14% greater SOC and N-tot concentrations, respectively, compared with CA. This LTE played a major role in the identification of strategies to increase soil fertility with diversified crop rotations through pasture integration, and statistically robust results were obtained that demonstrate the significance of frequent soil surveying over the long run.