Does addressing soil constraints change crop nutrition requirements? DAFWA researcher Craig Scanlan runs field trials in central and northern WA. The trials investigate links between soils, seasons and crop nutrition. The focus is how incorporating lime affects yield response to fertilisers. Soil mixing to treat water repellent soils is also explored.
The soils at the research sites are Tenosols and Kurosols. All sites had soil phosphorus (P) and potassium (K) levels above critical ranges.
Lime and nutrients
The change to soil pH from liming drives effects on soil nutrients. Plant available P is most responsive to pH change. Less change happens to available Kand nitrogen (N). Trace elements were least sensitive to pH change.
When soil pH increases, even low rates of P fertiliser can increase yield. Grain yield is very sensitive to P rate when soil pH is below 5.
Increasing soil pH boosts soil K retention as Cation Exchange Capacity (CEC) rises.
Soil inversion can overcome water repellency in soils. Deep ploughing or rotary spading mixes topsoil into the subsoil. Nutrients, organic matter and soil amendments move with the topsoil. This might change yield response to P and K fertiliser.
Treating water repellency hasn’t affected response to P and K yet. Autumn seasonal conditions seem to control yield effects from soil mixing. In a dry autumn, soil inversion can increase grain yield. In wetter conditions, no yield advantage was seen.
This video was recorded at the More Profit from Crop Nutrition II meeting in Sydney, 2017.
Liebe Group, West Midlands Group, DAFWA, GRDC