Weed Diversity and Seedbank Composition in Long-Term Fallow vs. Cropped Fields in Semi-Arid Agricultural Zones

Abstract

Weed community composition and soil seedbank dynamics were investigated in long-term fallow and continuously cropped fields located in semi-arid agricultural zones to evaluate the influence of land-use history on weed diversity and population persistence. Field surveys and soil sampling were conducted across representative sites to assess aboveground weed flora and buried seed reserves under contrasting management systems. Weed species were identified and analyzed using phytosociological parameters including density, frequency, abundance, and relative importance values. Soil seedbank composition was determined through seed extraction and greenhouse emergence methods from different soil depths. Results revealed substantial differences in weed diversity and species dominance between fallow and cultivated fields. Long-term fallow areas supported greater species richness and higher abundance of perennial and drought-tolerant weeds, whereas cropped fields were dominated primarily by annual species adapted to repeated disturbance and agricultural management practices. Seedbank density and species composition varied significantly according to soil depth and management history. Surface soil layers contained the highest concentration of viable weed seeds, particularly in cropped fields subjected to regular tillage operations. Certain invasive and stress-adapted weed species exhibited persistent seedbanks capable of surviving prolonged dry conditions typical of semi-arid environments. Seasonal rainfall variability strongly influenced weed emergence patterns and community structure across both land-use systems. Continuous cultivation and weed control practices reduced the prevalence of some perennial species but promoted dominance of fast-emerging opportunistic weeds with high reproductive capacity. The findings demonstrate that land-use patterns and agricultural disturbance significantly shape weed population dynamics and seedbank persistence in semi-arid agroecosystems.