The present study shows that differences in soil disturbance, caused by various seeding openers, significantly affected lime response; higher disturbance openers accelerated the liming effect, making earlier economic gains possible. However, even with low-disturbance openers, surface-applied lime no-till systems significantly increased pH in sandy-surfaced texture-contrast soils down to at least 20 cm, and that the effect was greater with increasing rates of lime. The liming effect is more rapid with higher-disturbance seeding methods, even at 10–20 cm soil depth. Nonetheless, the effect of seeding method diminished with time and was not detected in the subsoil after four years.
Seeding method had no consistent effect on the yield of the cereals which is important, because ZT disc openers can handle higher levels of crop residue at seeding and farmers may be encouraged to retain this residue, rather than burn it. In contrast, both canola and lupin yields were lower with low-disturbance ZT than with NT, possibly due to the influence of high levels of residue on canola establishment and disease, and from shallow seeding on lupin establishment. Nonetheless, residue managers and coulters can be attached to the seeding machinery, ahead of the disc openers, to create a residue-free seed row and increase seeding depth for canola and lupins. Additional research is required to assess this and the optimum seeding machinery setup.
There was a significant positive linear relationship between yield of wheat and barley and soil pH and a negative relationship for lupin. The regressions explained up to 34% of the variation in yield; other factors such as exchangeable Al concentration and seasonal variation most likely account for some of the remaining variation. Yield of canola was not related to soil pH, probably because of the major influence that seeding method had on canola establishment and yield and because soil pH was > 4.5, where yield responses are less likely (Gazey and Carmody, 2001).