Sieve size effects on root length and biomass measurements of maize (Zea mays) and Grevillea robusta

The purpose of this study was to investigate the effects of different mesh sizes on the recovery of root length and biomass and to determine whether t he degree of recovery was influenced by plant species and sample location. Sieves of 2.0, 1.0, 0.5 and 0.25 mm (4.0, 1.0, 0.25 and 0.06 mm(2)) mesh si zes were used to recover and measure the root length and biomass of Zea may s L. (maize) at 0-15 cm and 30-45 cm depths and of Grevillea robusta A. Cun n. ex R. Br. (grevillea) at the same depths 1.0 m and 4.5 m from a line of grevillea trees. At 0-15 cm, the coarser sieves (sum collected with 2.0 and 1.0 mm sieves) recovered approximately 80% of the total root biomass measu red, but only 60% of the root length. The proportion of total maize root le ngth and biomass recovered by the coarser sieves decreased with soil depth. The proportion of total grevillea root length recovered by the coarser sie ves was similar at the two soil depths, but increased slightly with distanc e from the tree line. The greater than or equal to 0.5 mm sieves recovered between 93 and 96% of grevillea and maize root biomass and between 73 and 9 8% of their root length, depending on the sample location. Roots passing th rough the 0.5 mm sieve, but recovered by the 0.25 mm sieve were about 20% o f total maize root length and grevillea root length at 1.0 m from the tree line but < 5% of the total grevillea root length at 4.5 m from the tree. Ro ots passing through the 0.5 mm sieve but recovered by the 0.25 mm sieve con tributed only slightly to root biomass. Although the greater than or equal to 0.5 mm sieves provided adequate measurements of root biomass, the greate r than or equal to 0.25 mm sieves were required for accurate measurement of fine root length. There was no universal correction for root length and bi omass underestimation when large sieve sizes were used because the proporti ons of length and biomass recovered depended on the plant species and on so il depth and distance from the plant.