Al. Smit et al., THE WAGENINGEN RHIZOLAB - A FACILITY TO STUDY SOIL-ROOT-SHOOT-ATMOSPHERE INTERACTIONS IN CROPS .2. METHODS OF ROOT OBSERVATIONS, Plant and soil, 161(2), 1994, pp. 289-298
Roots in the Wageningen Rhizolab are observed using two methods: (i) n
on-destructively, using horizontal, glass minirhizotrons at intervals
of 14 days between observations; (ii) with destructive sampling using
augers on three dates in the season. This paper reports changes with d
epth and time in root numbers per unit interface area of the minirhizo
tron tube (number of intersections) of four crop species (wheat, Bruss
els sprouts, leek and potato). The number of root intersections of Bru
ssels sprouts, wheat and potato declined with depth at any time, where
as leek showed a different pattern because maximum root growth was obs
erved at a depth of 10-20 cm. Root density generally decreased in the
following order: Brussels sprouts, wheat, potato and leek. Plots of ro
ot length densities, L(IV)(cm. cm(-3)), obtained by auger sampling, ve
rsus the number of intersections showed considerable variation in slop
e with species, time in the season and year, implying that a single, u
niversal equation to convert minirhizotron observations into volumetri
c root densities does not exist. Causes of variation in the slopes are
discussed. It is concluded that limited auger sampling combined with
minirhizotron observations yield adequate quantitative estimates of re
levant root properties.