Soil Compaction Depth on the Nodule Distribution and Biological Nitrogen Fixation of Vigna angularis

Abstract

Soil compaction is a major constraint affecting root development, nodulation, and biological nitrogen fixation in leguminous crops. This study assesses the impact of soil compaction depth on nodule distribution and nitrogen fixation efficiency in Vigna angularis under field conditions. Experimental plots were established with varying compaction depths to evaluate their effects on root growth, nodulation patterns, and nitrogen assimilation. The results indicated that increased compaction depth significantly restricted root penetration and reduced the spatial distribution of nodules, particularly in deeper soil layers. This limitation adversely affected symbiotic nitrogen fixation, leading to reduced nitrogen availability and overall plant performance. In contrast, shallow or reduced compaction treatments facilitated better root proliferation and more uniform nodule distribution, enhancing nitrogen fixation efficiency and plant growth. Compaction-induced changes in soil physical properties, such as increased bulk density and reduced porosity, were found to negatively influence rhizobial activity and oxygen availability within the root zone. Consequently, plants grown under lower compaction levels exhibited improved biomass accumulation and higher yield potential. While analytical methods were employed to assess nodulation and nitrogen dynamics, the primary focus remained on soil management and crop physiological responses. The findings highlight the importance of minimizing soil compaction to optimize root–soil interactions and enhance biological nitrogen fixation in Vigna angularis. This study contributes to sustainable agricultural practices by providing insights into soil physical management strategies that improve nutrient cycling, crop productivity, and soil health.