BJ Scott1,2, MK Conyers1, HM Burns3, CM Evans4 and NA Fettell4,5
1 Formerly: NSW Dept of Primary Industries, Wagga Wagga Agricultural Institute, Private Mail Bag, Wagga Wagga NSW 2650
2 Currently: Graham Centre for Agricultural Innovation (Charles Sturt University and NSW Dept of Primary Industries). Locked Bag 588 Boorooma St, Wagga Wagga NSW 2678
3 NSW Dept of Primary Industries, Wagga Wagga Agricultural Institute, Private Mail Bag, Wagga Wagga NSW 2650, www.dpi.nsw.gov.au, Email; firstname.lastname@example.org
4 Formerly: NSW Dept of Primary Industries, Condobolin Agricultural Research and Advisory Station, PO Box 300, Condobolin NSW 2877
5 Currently: School of Rural Science and Agriculture, University of New England, Armidale, NSW 2351
We examined two long term experiments and two paddock surveys and identified large changes in soil pHCa within the surface 20 or 30 cm of soil. The 5-15 cm was the most acidic layer in most soils; this suggests that soil sampling in the 0-10 cm and 10-20 cm depths is inadequate to describe what the plant may experience. The sharp pHCa changes within the 0-10 cm layer were modified by surface application of some N fertilisers, which acidified the normally less acidic 0-5 cm soil. Liming in a no-till system increased the soil pHCa in the shallow surface and the decrease in soil pH from 0-5 cm to 5-10 cm was even greater than in an unlimed soil. Initially, soil pH testing in finer depth layers in some paddocks should be informative. A regular liming program, with strategic cultivation to incorporate lime more deeply and thoroughly, could be considered.