NGN Action learning on crop response to acid subsoil stratification and amelioration benefits.

This investment focuses on a range of solutions that adress subsurface soil acidification to ensure crop yields and crop choice are not limited.

Past research has demonstrated that agricultural lime is the best option to ameliorate acidity (e.g., Woodruff, C.M. 1948). However, in south-east Australia, the adoption of extension messages of the 1990s which promoted rules of thumb of 2.5 tonnes/ha every 10 years or liming rates just sufficient to remove aluminium toxicity (e.g. to pH 5.0 CaCl2) has been shown to be ineffective in addressing subsurface acidity. In addition, some growers have ignored these messages altogether, believing that the cost of lime is prohibitive. Current on-farm acid soil management programs are often reactive, focusing on amelioration of existing 'problems', (i.e severely acidic acid soils) rather than a prophylactic liming approach. They ignore acidification of highly productive soils that should be prioritised for early intervention to prevent subsurface acidification and gradual loss of production potential. This is particularly relevant to soil types most suitable for pulse production and other sensitive crops such as barley. A lack of attention to topsoil pH has led to the development of subsoil acidity, with low soil pH often in the 10-20 cm layer.
The investment is led by Dr Jason Condon and involves a number of grower groups including; FarmLink, Holbrook Landcare Network and Central West Farming Systems. The investment outcome is to: by August 2025 have an additional 10% of grain growers in southern and central NSW understand the financial benefits of liming surface soils to above 5.5 (CaCl2) to address subsoil acidity.