Current soil amelioration options, including liming, deep ripping, deep soil mixing, and soil inversion, address one or more soil constraints to provide grain yield increases of 30 percent or more. Prior research had not determined the best combination of multiple amelioration practices to optimise yield response and longevity for sandy soil. The intent of this research was to provide growers with an understanding of how to prioritise soil amelioration practices to profitably manage coarse deep sandy soil in northern wheatbelt and assess value of amelioration treatments applied over time. Our measure of success was cumulative return ($/ha) over four years.
This four year experiment used grower machinery to implement tillage and surface lime/gypsum treatments in a replicated, non-factorial, strip plot design in a coarse, acidic, deep sand. Year of tillage application was part of treatment structure applying different techniques in different combinations over three separate seasons. Tillage treatments consisted of deep ripping to a depth of 500 mm, rotary spading with an Imants 58 series to 350mm or a combination of the two separated by season.
For rotary spading there is a large, up to 78 precent, grain yield response during implementation year, and up to 45 percent the following year. Spading this soil, while profitable, is risky as yield response beyond second year proved variable in this trial.
Using net present value, accumulated over four years to rank the treatments had deep ripping to 500 mm conducted in year 1 as best option, with a cumulative return of $1477/ha. The Nil treatment had the lowest cumulative return of $665/ha nearly $200/ha below next lowest treatment.
The benefit of this trial was that treatments were implemented across multiple season types. During low rainfall seasons low yield improvements from tillage did not outweigh the high implementation cost.