by Bill Crabtree, Agronomist and General Manager of 4Farmers
The 800 kg/ha wheat yield increase from 2 L/ha of Aquifer (see graph) has created much discussion and enthusiasm. This wetter trial showed dramatic visual differences from the start. It was on a very water repellent sand, and all rates gave a 2-3 fold emergence increases over the nil. It was kept weed free and therefore the thin nil plots were able to compensate well to yield near 2 t/ha.
This graph shows the yield increases for both Aquifer and SE14. The high rate of 8 L/ha was not quite as good as 2 L/ha. This contrasts my old work with wetter only (no humectant) where on shallow duplex soils I got increasing yield benefits to 50 L/ha. This informs us as to how the humectant component might be working. It makes us ponder.
Humectant can suck water to it like clay
Humectants can also work against us in marginal moisture (if over several weeks) and with different placement options. Understanding these issues will help us to hit more goals than make losses. Questions on X have helped the thinking process. Arguably, this trial suggests a mild yield penalty at 8 L/ha and when not put near the seed. So this invites caution as the humectant will not always help. We need to pick winning opportunities.
One farmer north of Merredin last year reported that using 2 L/ha Aquifer on his canola in a wettable dry soil placed with the seed gave him a small yield penalty, verified by his yield date. He thinks the very small amount of rain (<2mm) events that he had in May and June, combined with the humectant, bound up the small amount of water and kept it from the seedling (choking the seed). This could help explain the variable results that farmers sometimes see. Knowing this risk helps us be more targeted with Aquifer. If he had got 5 mm post seeding and not 2 mm, then the result could have been very different.
This issue was also highlighted in our wheat trial where we put 2 L/ha on the surface and it reduced wheat emergence and yield compared to when being placed with the seed (2.25 vs 2.75 t/ha). Note that both these adverse results came from off label use.
Remember that this Mindarabin trial was in sandy, repellent soil, with some subsoil moisture and with restricted evaporational loss (acting like a mulch) and very poor light rains after a mid-June seeding. So, this is all good news for farmers with a similar scenario and with Aquifer cost being so affordable you can take courage and get Aquifer at 2L/ha with your seed – not just with canola as this data shows – but all crops.
Urea & UAN burns emerging crops
Of course, it is simple to put UAN down with the Aquifer in a single shoot system. But UAN is a salt and it can make water less available. Further, it does gas off and burn the emerging seedling. So, farmers have learnt to either cut back the rate of UAN or change to a twin liquid system. Or they run the gauntlet.
For those who received Tropical Cyclone Mitchell’s rain you will have received good, mineralised N from the summer rain. So, perhaps your need for the UAN with the seed is diminished, and a better would be with UAN on early post emergent weed control.
The key to a high yielding crop is good, early, safe establishment. The 50% urea component in the UAN can hurt the crop if it is near the seed. Our data encourages placing Aquifer near the seed.
The urea rate trial, placed with wheat seed done on Geoffrey Marshall’s Hyden farm in 1999 is still very useful. I placed urea with wheat – down the one tube to push the limits the rates were 0, 40, 80, 120, 160 and 200 kg/ha. You can see every rate (in photo). The plot left of centre had zero urea added to the left of that it had 40 then 80 then 200 kg/ha (it killed everything). Sadly, the site was 100% frosted, so there was no yield data.
This work shows 40 kg/ha can do serious damage to wheat. In another trial I added N-Butylthiophosphoric triamide (NBPT) and it halved the damage. We do have our own formulation available. So will it help reduce UAN burn when placed with the seed?
The twin system option
It might be smart to invest in a twin system. My latest brainwave, which might have merit as discussed on X, requires a twin liquid system. In this case consider placing 2 L/ha of Aquifer (humectant plus wetter) with the seed and say 200 mL/ha of Aquifer 4 (predominantly wetter) behind the press wheel with the UAN.
This way the UAN will be drawn into the topsoil above the seed, reducing volatilisation. It can then convert to a stable ammonium (NH4+) ion and with a wetting front it will dilute itself downward. Perhaps NBPT will help this to be more efficient. Doing this will allow the humectant to maximise drawing water from below (after a summer rain) and greatly reduce the risk of the UAN burning, salting or chocking the seed. Lots of ideas to test here. But by knowing how it works I believe we can champion some worthwhile improvements in emergence.
For more info and a chat please call us at 4Farmers on 9356 3445.