Now is the time to book in soil testing for your farm. The results are an important tool for planning rotations, testing for moisture and understanding the nitrogen (N), phosphorus and micronutrients (copper, zinc etc.) status of your soil. This aids in decision making around fertiliser inputs during the growing season.
High stubble loads produced in 2016 led to increased mineralisation throughout the 2017 growing season where many paddocks ended up with high N reserves. With similar conditions on many farms during 2017, growers could be facing a familiar scenario.
Just how much is contributed is difficult to predict at the start of a growing season, however knowing the soil N status prior to sowing can help growers adjust their N fertiliser applications as the season progresses.
The increased N mineralisation that results from a year with high soil organic matter and crop residues, contributes to the total crop N requirement.
As a general rule, warm temperatures, moist soil and a good supply of organic matter generate conditions conducive to mineralisation. These rates are high over summer however the process continues throughout the year. In spring, it peaks in line with increases in soil temperature but only in the presence of moist soil.
A rapidly growing crop under ideal conditions (mid spring, ample moisture, warm temperatures) will need 4-5kg/ha/day of N where, under the same conditions, peak mineralisation could amount to 1kg/ha/day.
This highlights how ‘getting it right’ with tactical N fertiliser application can achieve real efficiencies and therefore savings, at key crop growth stages, like at sowing and during the stem elongation phase (GS30-39).
BCG will again be conducting soil sampling in 2018 as a commercial service to growers, please find the flyer here, contact the office on (03) 5492 2787 for more information.
Further research about nutrient management can be found here: https://www.bcg.org.au/planning-nutrition-for-2016/.
Resources:
https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2016/02/factors-influencing-nitrogen-supply-from-soils-and-stubbles Author: Vadakattu V.S.R Gupta (CSIRO Agriculture, Waite Campus, Adelaide) | Date: 09 Feb 2016
https://grdc.com.au/news-and-media/news-and-media-releases/south/2015/01/understand-the-factors-that-affect-mineralisation Author: Alistair Lawson | Date: 19 Jan 2015
