27 August 2019

Tillage and Nutrition - finding the balance

A $14.6 million, multi-partner, crop nutrition investment strategy is being rolled-out in the western region. The project is focusing on new thinking and research ...

sandy soils typical to parts of Western

Australia and found in South Australia's and Victoria's memory country create considerable and costly grain constraints in W a water repellency resulting in low nutrition use efficiency and poor crop establishment effects around ten million hectares water-repellent soils in Western Australia are fairly common in the West Midlands region in the central wheat belt and also on the south coast so the main problem with water appellant is that it leads to uneven wedding of the soil and inefficient use of rainfall and ultimately lower grain yield lwas annual price tag put on lost production through water repellents is estimated at 250 million dollars GID see is investing in a multi-million dollar soils and crop nutrition strategy aimed at managing nutrition after ameliorating these kinds of soil constraints so through the GRDC and deeper project we are focusing on how removing soil constraints changes soil nutrient supply but also how it changes crop demand the effective inversion tillage on grain yields compared to phosphorus and potassium management is a research focus increasingly growers are

turning to inversion tillage to bury topsoil and bring more wettable soils to the surface there's a number of approaches that growers use to manage water balance soils so farro sowing claying and inversion tillage as examples but we're most interested in the inversion tillage because generally water-repellent soils are quite stratified and inversion tillage makes a major change to the position of the nutrients in our soil importantly the tillage treatments especially rotary spading had a greater impact on yield the nutrient management treatments and that seem to be about improved wettability of the soil profile and the influence of that on soil potassium if I was already the work that we've done today using colored traces to quantify where soil from different layers ends up after inversion tillage has shown that moldboard plow generally does the best job of inverting soil and that you can vary 70 to 80 percent of your topsoil usually at ten to thirty centimeters and with rotary spading you're likely to end up with thirty percent or so of your topsoil remaining in the surface but it

does a better job of mixing the different layers Craig says part of the yield benefit and response to rotary spading was due to some extent to improved access by crops to nutrients such as potassium which allows plants to use water more efficiently clearly by removing a soil constraint you're increasing yield and changing nutrient demand but from a nutrient supply point of view potassium supply seems to be where the main changes are caring after ameliorating these soils the addition of lime to water repellent soils can prove helpful but falls short of addressing planned access to potassium we included lime as a treatment to try and increase subsoil cation exchange capacity and decrease the rate of leaching of potassium and while we did increase subsoil cation exchange capacity it didn't increase the soil k supply through the crop growers are encouraged to measure water repellents prior to and after soil amelioration practices such as spading to better understand the consequences or benefits of improving water infiltration the soil testing is a valuable way for estimating soil nutrient supply and what your fertilizer

requirements might be and one of the questions we had going into this project was whether they would still hold true poor soils that have been ameliorated and an interesting outcome from our long-term field experiment is that the calibration for potassium in particular still holds true it's early days yet but progress is being made to help growers better balance tillage and nutrition on water-repellent sands we're a year into the project and got a couple of years to go our work so far is clearly showing that removing the constraint increases yield potential and nutrient demand and will continue with a series of experiments that quantifies our soil nutrient supply is changed by removing soil constraints go to the description bar below for the latest information links and resources