Non-inversion tillage effects on soil mechanical properties of a humid sandy loam

Optimisation of soil tilth is of paramount importance in organic plant prod uction in order to enhance crop growth. Noninversion and reduced tillage sy stems are often claimed to be preferable for organic farming. The purpose o f this study was to evaluate the early stage effects of converting a mouldb oard-ploughed soil to a non-inversion tillage system. A multi-level experim ental strategy including in situ, on-site and laboratory methods was follow ed in order to relate quantitative measures of soil physical properties dir ectly to soil behaviour in the field. A non-inversion deep soil loosening ( 0-35 cm) tillage system (NINV) was compared to a conventional mouldboard pl oughing and harrowing tillage system (CONV). The experimental site was loca ted on an organically managed sandy loam soil. The tillage treatments were applied to plots in two fields (B-3 and B-4) at the experimental site. Limi ted numbers of measurements were performed in the B3 field during the 1997- 1999 growing seasons. A more comprehensive programme was carried out in the B4 field in May and September 1998. A root-restricting plough pan was dete cted in the CONV treated soil. The NINV treatment effectively loosened the plough pan resulting in a visibly improved soil structure and a decrease in soil strength. The penetration resistance in the plough pan was reduced fr om about 1800 kPa in CONV to less than 1000 kPa in NINV when measured at fi eld capacity. The loosening of the plough pan was still evident after 2 yea rs without tillage operations in a perennial grass/clover crop. The topsoil of the CONV treatment had a more desirable tilth than that of the NINV tre atment, which had higher soil strength at the 7-14 cm depth. In accordance with this, the CONV treated topsoil fragmented more readily than the NINV s oil in the field. The laboratory measurements on soil from the September sa mpling showed that the NINV treatment had lower friability index (i.e., fri ability index of 0.16 and 0.22 for NINV and CONV, respectively) and higher tensile strength of air-dry aggregates. The differences in topsoil tilth we re not eliminated by natural soil meliorating processes during the growing season. This paper discusses the early stage effects of converting to non-i nversion tillage. A number of years of continued treatment may be required before beneficial effects of noninversion tillage are manifested in improve d topsoil tilth. (C) 2001 Elsevier Science B.V. All rights reserved.