Now is the time to be thinking about soil testing. Soil testing is important as it gives you a guide for existing soil nutrient levels. The test results can be used to make fertiliser decisions and gives you the confidence that you are applying adequate fertiliser to meet target yield and protein. Soil testing is important to monitor soil phosphorus, organic carbon and pH.

With the dry seasons and lower crop yields there may still be high levels of phosphorus in the soil and there may be an opportunity to reduce phosphorus rates slightly and associated costs. However, if you cut back phosphorus rates in 2007 due to the dry season of 2006 then rates of phosphorus may need to be increased in 2008.     

Monitoring soil pH is important on those soils on the eastern half of the northern agricultural district that are prone to soil acidification.  Soil acidification is due to the use of acidifying/nitrogen fertilisers, removal of plant and animal products such as hay and wool and low buffering soils. Once the soil pH falls less than 5.0 – 5.5 then this can restrict the productivity of crops and pastures. Regular applications of lime should be applied to maintain soil pH.

If soil pH levels have dropped and you want to raise the soil pH levels, then the amount of lime to apply will depend on the current soil pH, the target pH, soil texture and lime quality. The amount of lime required to raise the pH by one unit for a sandy loam is in the order of 3.0 tonnes/hectare. 

Soil testing is a small cost to pay to monitor your soil nutrient and pH levels. Soil testing kits are available from any PIRSA office.  

AUTHOR: Andrew Harding, Senior Soil Land Management Consultant, Rural Solutions SA

CONTACT: Andrew Harding, Rural Solutions SA Clare Office, Telephone (08) 8842 6231, Mobile 0417 886 835, Email harding.andrew@saugov.sa.gov.au