Dr Jian Jin1, Dr Roger Armstrong2, Dr Peter Sale1, Dr Caixian Tang1
1Department of Animal, Plant and Soil Sciences, AgriBio, La Trobe University, Melbourne , Australia, 2Department of Economic Development, Jobs, Transport & Resources, Horsham, Australia
A range of subsoil physicochemical constraints limit root penetration, nutrient and water uptake and crop yields throughout large areas of cropping soils in western Victoria. Adding large quantities of nutrient enriched organic matter (also known as subsoil manuring) has been shown to ameliorate such constraints, but the mechanisms underpinning this crop response are not well understood. Two field trials were established at Tatyoon (high-rainfall zone; 550 mm annual rainfall) and Kiata (medium-rainfall zone; 400 mm annual rainfall) in Victoria in 2018 with four treatments: (1) Control; (2) gypsum, deep-banded at a depth of 30 cm in the subsoil (Gypsum-subsoil) (3) chicken manure pellets, top-dressed on the soil surface (Manure-topsoil) and (4) chicken manure pellets, deep-banded in the subsoil (Manure-subsoil). The effect of these amendments on photosynthesis, leaf chlorophyll, leaf area and biomass, and root morphology of wheat were investigated. Rainfall at both sites was below average (Decile 1-2) and significant treatment effects occurred only at the high-rainfall Tatyoon site. At the Tatyoon site, the manure-subsoil resulted in a 22.5% increase in grain yield (8.12 t/ha), followed by manure-topsoil (7.53 t/ha), gypsum-subsoil (6.64 t/ha) and control (6.63 t/ha). At Kiata, however, there was no treatment effect on grain yield, with an average of 2.72 t/ha. At Tatyoon, gypsum-subsoil and manure-subsoil tended to increase root length in the 28-42 cm section of the soil profile at anthesis. The photosynthetic function of leaves continued for a longer period after anthesis with the manured treatments compared to the control. Greater leaf N concentrations recorded in these treatments suggest that greater N uptake facilitates C assimilation and yield formation by enhancing leaf photosynthesis and prolonging leaf greenness. Future investigations on the association between SOM, soil structure and soil moisture dynamics, and water-use efficiency should provide more insights into the efficacy of these treatments.
Biography: Jin received his PhD in soil science from La Trobe University in 2014. He is currently a postdoctoral fellow working on the GRDC project “Understanding the amelioration processes of the subsoil application of organic and other amendments in the Southern Region”.