Spring Newsletter - October 2017
ESN: Environmentally Smart NitrogenESN or Environmentally Smart Nitrogen is a new development in Nitrogen fertilizer. It is a urea granule comprised of 44% nitrogen contained within a flexible polymer coating. This coating protects the nitrogen from loss mechanisms and releases nitrogen in response to soil temperature.
ESN’s polymer membrane allows moisture to diffuse into the granule, creating a nitrogen solution. The solution moves out through the membrane at a rate that is controlled by soil temperature and matches the nitrogen demand of the growing crop.
One of the main benefits of ESN is its flexibility to be used at sowing as well as for topdressing. The unique polymer coating allows you to apply ESN granules at planting without significant risk of seed burn. Typically, rates of 60 kg ESN/ha may be used at sowing (equivalent to about 100 kg urea/ha), in combination with 80-100 kg starter fertiliser (such as MAP or DAP).
ESN releases its N in response to conditions that trigger plant growth. It can be applied over a range of times during the year & works well in a variety of weather conditions:
- wet conditions (ESN’s polymer coating stops leaching while inhibitors may be affected by excess moisture),
- dry conditions (ESN will conserve its N until enough moisture is available).
As a result, ESN is less prone to Nitrogen losses due to leaching, volatilization & denitrification. ESN’s polymer coated granule is designed to protect the N and allow it to release over 50 - 80 days. Around 15-25% N will be released from ESN granule in the first week, with the remainder over the next 50-70 days. Typical release in soil at this temperature would be about 25 to 30% in the first two to three weeks.
If applying ESN in a situation where some immediately available N is needed, we suggest blending ESN with sufficient soluble N, such as a urea.
Independent pasture trial results available
Tired of the limited information provided in glossy pasture variety brochures? Southern livestock producers now have access to quantitative data about the performance of pasture varieties at their fingertips, with the launch of the Pasture Trial Network (PTN) website.
The Pasture Trial Network (PTN) is based on a set of independently run pasture trials to evaluate pasture species performance (seasonal dry matter production) & persistence. The trials are audited to ensure that they are conducted under the strict protocols. These trials are designed to bring creditability to the pasture seed industry while allowing producers and advisors to make better decisions based on evidence.
These trials started in 2014 on the back of the Pasture Variety Trial Network initiative started by Meat & Livestock Australia (MLA) in collaboration with pasture seed companies in 2011. The Pasture Trial Network has now conducted over 90 trials across 30 sites in Australia, evaluating 9 different pasture species.
To view the results from the Pasture Trial Network for various phalaris, cocksfoot, Lucerne, perennial ryegrass & tall fescue varieties, you can now view information from your closest trial via the following website: http://tools.mla.com.au/ptn
Legume nodulation & soil acidity
A recent survey of legume nodulation across 220 paddocks over four regions (Central West, Central Tablelands, Riverina & Monaro) showed at least 90% of these sites had inadequate nodulation. Most paddocks contained sub clover, with a few annual medics & Lucerne.
Whilst several factors have been attributed to poor legume nodulation (including low Sulphur & herbicide residues), soil acidity appears to be a major contributing factor. Most paddocks tested had a soil pH below the level considered suitable optimum for healthy Rhizobia function. Table 1 below (from Hackney et. al, 2017 Grasslands Society of NSW Conference Proceedings), shows a higher soil pH requirement for the legume plant in contrast to Rhizobia. To sum up, for optimal legume growth & nodulation, soil pHCaCl in the top 10cm (where most of the Rhizobia live) should be around 5.5 as a minimum. We often aim for a soil pHCaCl around 5.0 for optimum growth of introduced species, however it is important to aim slightly higher to gain the benefit of effective nodulation in our pasture legumes. In addition:
- keep an eye on Sulphur levels in your soil tests (not just Phosphorus);
- watch plantback periods for herbicides such as sulfonyl ureas (Logran, Ally, Brushoff) & clopyralid (Lontrel).
Only in this way can we hope to maximize our pasture’s true potential through efficient legume nodulation & Nitrogen fixation.
& Now for the weather…..
The Bureau of Meteorology indicates rainfall outlook over the spring/summer period is likely to be neutral conditions. However, two models indicate the likelihood of a brief, late-starting LaNiña over the summer. If La Niña does form, rainfall outlooks remain neutral due to competing climate drivers.
Following a brief period of warming, tropical Pacific surface waters cooled significantly in the past fortnight, and hence the central to eastern tropical Pacific Ocean is now generally cooler-than-average. Atmospheric indicators of ENSO, including the Southern Oscillation Index (SOI), trade winds and cloudiness near the Date Line, are also approaching La Niña levels.
Table 1: The tolerance of various species of pasture legume & their associated rhizobia to a range of soil pH(CaCl) & indicative productivity (poor-shown in red; sub-optimal-shown in orange; optimal-shown in green) at specific soil pH (from Hackney et. al, 2017 Grasslands Society of NSW Conference Proceedings).
The 30-day Southern Oscillation Index (SOI) to 22 October is +13.0 (90-day value +7.1).