Monitoring root length density and root biomass in asparagus (Asparagus officinalis) with soil cores

Abstract

Soil type, crop management practices, annual plant growth patterns, and seasonal changes in the soil environment all influence asparagus (Asparagus officinalis) roots. This study describes the dynamic changes in root growth that occur during the annual growth cycle of asparagus grown in two contrasting soil types and crop management systems. Root length density and biomass were estimated from soil cores (55 mm diam. × 0.2 m long) collected to 1 m in three locations adjacent to the row (0.15, 0.3, and 0.6 m from row centre). Samples were collected on six dates (early, or postharvest at early, mid, or late fern growth, and dormant period) between October 1999 and June 2000. Test sites varied with soil type (sandy loam or silt loam) and crop management system (normal 12‐week harvest or extended 15‐week harvest). Fleshy and fibrous roots were collected, root length density determined, and dry weights measured. Fleshy asparagus roots grew deeper in a sandy soil than in a silt soil, had higher dry matter content in silt than in sandy soil, and greater root length in a silt compared to a sandy soil. Fibrous root length density was greater during fern growth than during harvest, in a sandy versus a silt soil and at shallow versus deep sampling depths. Sampling date, soil depth, and sample location all significantly influenced asparagus fleshy and fibrous root biomass. Soil cores accurately estimated both total fleshy root length density and dry matter content when compared to the more time‐consuming complete root excavation. Results can be used to improve crop management practices, predict root biomass, and increase our understanding of the dynamics of root development in asparagus.