The effect of soil physical conditions produced by various cultivation systems on the root development of winter wheat

Abstract

The results of a field experiment on winter wheat are presented in which the effects of the soil physical properties produced by different cultivation systems were studied in relation to root development.The extension rate of the seminal root axes was slower in undisturbed or shallow (5 cm) cultivated soil than in ploughed or deep (20 cm) cultivated soil leading to earlier lateral branching and the production of an effectively shallower seminal root system which persisted throughout the season. During the first four weeks after drilling the soil in the ploughed and the deeper cultivated plots was of lower bulk density and there were more pores of a diameter suitable for unimpeded root extension. It is suggested that seminal root development in uncultivated soils, which are less readily deformed than cultivated ones, is related to the probability of the extending seminal axes contacting pores of suitable dimensions.The implications of shallower rooting are discussed and related to field experience with cereal crops drilled directly into uncultivated soils where success has consistently been achieved on free-draining, open-textured soils.

Pore Characteristics of Soils From Two Cultivation Experiments as Shown by Gas Diffusivities and Permeabilities and Air‐filled Porosities

“…1) mainly because drainage between saturation and -2 kPa and hence the volume of pores >75 pm radius were greater in the ploughed soil ( Fig. 2), as was also observed by Finney and Knight (1973). However, more water was lost between -20 and -100 kPa in the direct drilled than in the ploughed soil ( Fig.…”

Crop root system response to irrigation

“…When they do penetrate soil, they must compress the soil (Dexter 1987) so that the elastic modulus or compressibility of the soil is an important controlling factor (Rickman et al 1991). In many irrigated situations, high soil strength can be encountered by roots in plow pans or traffic pans (Finney and Knight 1973) and deep tillage may improve root growth and nutrient uptake (Ide et al 1984). Thus, the volume of soil for root extraction of water may be limited.…”

Oxygen Concentrations in a Clay Soil After Ploughing or Direct Drilling

“…T H E movement of oxygen into soil may be affected in different ways by changes in soil porosity which result when conventional cultivation (ploughmg followed by secondary tillage) is replaced by direct drilling, the most extreme form of minimum cultivation. More restricted aeration might be expected in untilled soil than in cultivated soil due to the higher bulk density (Triplett et al, 1968;Soane et al, 1975; see also Cannell and Finney, 1973) and lower volume of pores with a diameter greater than 3 0 p m (Baeumer, 1970;Ehlers, 1973;Finney and Knight, 1973). On the other hand, aeration may be promoted in untilled soil as the continuous channels and pores created by growth of roots, earthworm activity or cracking of the soil in dry weather have not been destroyed by deep cultivation of the soil (Ehlers, 1975;Ellis et al, 1979).…”