Tillage alters root distribution in a mature asparagus planting

Only a limited number of studies have been conducted on the root growth of asparagus. Soil cores from six sample depths (0.15, 0.3, 0.45, 0.6, 0.75, a nd 0.9 m) in two tillage systems (till and no-till) were separated into fib rous (Fi) and fleshy (F1) roots and root length density (RLD) determined. H arvest dates for roots began on 22 March and continued at three-week interv als until 8 November. Since analysis of variance was unable to identify sig nificant tillage system by harvest date by sample depth interaction, the da ta were re-analyzed using the additive main effects and multiplicative inte ractions (AMMI) statistical model. AMMI identified significant interactions between tillage dates (tillage systems by harvest dates) and sample depth for Fi-RLD and F1-RLD. Fi- and F1-RLD increased in all depths before spear harvest in March and April, decreased during the spear harvest period of Ma y to June, then increased after fern establishment in July before declining late in the growing season. Regardless of sample depth or harvest date, RL D for fibrous and fleshy roots were greater in no-till than till. RLD were greatest in the 0.3 and 0.45 m depths and tended to decrease as depth incre ased for both tillage systems. In general, RLD were greater for fibrous com pared to fleshy roots in all depths. A better understanding of the changes in root growth may be useful for improving asparagus yields through better crop management. (C) 2000 Elsevier Science B.V. All rights reserved.