Soil Aggregates Are Governed by Spacing Configurations in Alfalfa-Jujube Tree Intercropping Systems

Abstract

Soil aggregates play an important role in affecting the structural stability of the soil, and it is important to understand the relationship between soil aggregate stability and crop yield in herbage-fruit tree intercropping systems. In this study, we determined the optimal spacing configurations for improving aggregate stability while increasing crop yields in alfalfa-jujube intercropping systems. The treatments included three intercropping patterns, i.e., the distances between alfalfa and jujube at 0.5 m (IP0.5m), 1 m (IP1m), and 1.45 m (IP1.45m), along with monoculture alfalfa (CKAL) and jujube (CKJU). The results showed that IP0.5m, IP1m, IP1.45m, and CKJU effectively improved soil aggregate structure compared to CKAL. The IP1m spacing significantly increased the amounts of macro-aggregates (8.2%), and improved soil mechanical properties and aggregate stability among the other treatments, which was partly attributable to increased mean weight diameter (13.6%) and decreased soil aggregate destruction rate of water-stable aggregates (2.9%). The results of the principal component analysis showed that IP1m treatments had a positive effect on PC1. The one-meter spacing of jujube-to-alfalfa intercropping optimized the soil structure while improving the yield (8.3%); thus, it can be considered the most suitable intercropping spacing configuration for growing alfalfa in jujube plantations.

Keywords

• soil aggregates
• intercropping
• spacing configurations
• soil water-stable aggregates
• <i>ziziphus jujuba</i>
• <i>medicago sativa</i>