Trenching and compost sustain grain yield increases over nine years on deep sands but at a cost

Authors

David J.M. Hall, Department of Primary Industries and Regional Development, Esperance, Western AustraliaFollow
Tom J. Edwards, Department of Primary Industries and Regional Development, Esperance, Western AustraliaFollow

Document Type

Article

Publication Date

4-22-2025

Journal Title

Soil Research

ISSN

ISSN 1838-675X eISSN 1838-6768

Keywords

Amelioration, Auger trenching, Compaction, Compost, Economics, Grain yield, Lime, Sandy, Soils

Disciplines

Agribusiness | Agricultural Science | Agronomy and Crop Sciences | Biochemistry | Natural Resources and Conservation | Natural Resources Management and Policy | Organic Chemistry | Plant Biology | Soil Science

Abstract

Context. Crops grown on deep sands on the south coast of WA are limited by soil physical and chemical properties including compaction and poor nutrition. Aims. Crops grown on deep sands on the south coast of Western Australia are limited by soil physical and chemical properties including compaction and poor nutrition. Our aim was to determine what effects deep-placed organic amendments have on soil properties and crop production in a deep sand and whether such amendments are profitable. Methods. A long-term field trial was conducted over nine years (2015–2023) to investigate soil amendments including lime (0 and 2 t ha−1 ) and composted chicken litter (0, 10 and 20 t ha−1 ) with and without incorporation in trenches (0.1 m wide, 0.5 m deep spaced at 0.9 m) in an incomplete factorial design on crop yields, soil chemistry, soil physical properties, root growth and economics. Key results. Grain yields were increased by more than 1 t ha−1 yr−1 where compost and lime were incorporated to 0.5 m. Grain yields for the highest yielding treatments were at or near their rainfall limited yield potential. The yields for surface applied compost did not differ to those that were trenched. The yield increases were attributed to higher nutrient (N, P, K, S) supply, higher pH and organic carbon, reduced bulk density and soil strength within the trench lines, along with increased root activity. The time taken for the compost applied treatments to exceed the cumulative profits of the Control treatment ranged within 19–29 years assuming current prices, costs and yield trends. Conclusion. Reduced bulk density and soil strength associated with trenching was found to persist within the trench lines for at least six years resulting in increased root growth at depth. The addition of composted chicken litter, either surface spread or incorporated in trenches increased grain yields more so than trenching alone. Implications. The compost treatments, although having the highest grain yields, were not commercially viable at the rates applied. The trenched treatments had higher cumulative yields than those treatments that were not trenched. In the absence of compost, the trenched treatments were the most profitable with discounted returns AUD282 to AUD931 ha−1 higher than the Control over nine years.

Recommended Citation

Hall DJM and Edwards TJ (2025) Trenching and compost sustain grain yield increases over nine years on deep sands but at a cost. Soil Research 63, SR24221. doi:10.1071/SR24221