Article taken from British Dairying magazine
Forage maize trials in Norfolk have illustrated the potential benefits of using a nitrogen stabiliser to boost cob weights.
Forage maize offers an excellent food source for dairy cows with high starch levels and energy characteristics and high dry matter yield potential. However optimising yield from crops 'can be helped by using N-Lock, a nitrogen stabiliser from Dow AgroSciences. It can deliver significant benefits, by protecting fertiliser input to when the crop really needs it later in its lifecycle.
Location, good seedbed preparation, soil pH and selecting the best variety are all key factors to consider when growing forage maize. However, it is nutrient application that plays a vital role and, in particular nitrogen. As most, if not all nitrogen, is applied at the establishment or early stages of the crop, often there is insufficient nitrogen remaining during the latter stages of crop development and hence is often a limiting factor on reaching crop yield potential. This is a particular challenge for modern varieties that have greater yield potentials than their predecessors. When nitrogen fertilisers are applied to the soil, a nitrification process takes place where the ammonium-nitrogen is converted to nitrite (NO2) by nitrosomonas bacteria, and then to nitrate (NO3) by the bacteria nitrobacter. Ammonium is positively charged and is attracted to the negatively charged soil particles, so it cannot be lost from the soil rooting zone by leaching away after heavy rain-fall. However nitrite and nitrate are negatively charged and so are repelled by the negatively charged soil particles. When nitrogen is in the nitrite and nitrate forms, the nitrogen can be lost through the soil profile by leaching and in wet conditions can denitrify and be lost to the atmosphere as greenhouse gases. Keeping nitrogen in the ammonium form enables the nitrogen to be attracted to the soil particles so that the nitrogen remains in the rooting 'zone. N-Lock works by inhibiting the nitrosomonas bacteria preventing them from converting the ammonium to nitrite, and hence pre-venting the conversion to nitrate.
It is this inhibition of the bacteria that in effect stabilises the nitrogen, meaning less nitrate can be leached away from the crop's root zone, and so is available for longer into the growing season, helping optimise the yield and quality potential. It's a real win-win situation, which gives agronomic, economic and environmental benefits. Last year Agrovista conducted a variety trial to show the performance of 56 forage maize varieties, and the benefits of including N-Lock as an application at a two hectare site at Great Ellingham, Norfolk. The site had a sandy clay loam soil, medium but bordering on the lighter section. The land was prepared and fresh cattle farmyard manure applied at eight tonnes per hectare and ploughed in with the cover crop. Fertiliser was then applied as 40kg of nitrogen as a seed bed fertiliser followed by 20kg of nitrogen and sulphur with post-emergence herbicide. A Sumo cultivator was run through the soil just prior to drilling to loosen the soil up and create a seedbed.
Drilling took place straight after. The weather at drilling was just right—dry and warm. The maize was drilled on 10th April 2015 and the drill calibrated to drill to 38,000 seeds. Once calibrated all seeds were drilled at the same rate to deliver 10 rows per variety. The crop was drilled at 90 degrees to plot length and treatments were overlaid to stop a variety having a tramline effect. Pendimethalin was applied pre-emergence at 2.5 litres per hectare of a 400g /litre strength product on 12th April 2015. The site was not rolled. Agrovista's adjuvant Remix was tank mixed with the pendimethalin to improve herbicide performance. On the same day the N-Lock was applied to one strip of 12 metres at the full rate of 2.5 litres per hectare. In practice all three products could be applied together as they tank mix well and this would save on going over the land twice. N-Lock needs to be incorporated into the soil within 10 days of application, either by light cultivation, or with 12mm of rain. In this situation, the day after application it did rain extensively with 14mm of rain on 13th April which was ideal.
The maize varieties were following a crop of rye so it was a robust post-emergence treatment with mesotrione + nicosulfuron for grass (nicosulfuron) and broad-leaved weed (mesotrione) control. This product gives an excellent broad spectrum of control. Application was made at the crops 4-true leaf stage at the rate of 1.5 litres per hectare on 26th May. The trials plots comprised:
• 12m N-Lock trial—applications as per above
• 12m Untreated plot
• 12m azoxystrobin + propicona-zole applied at 8 true leaves for disease control on 10th June at 1.0 litre per hectare.
After the applications the crop was left and monitored. In the N-Lock treated crop there was no real visual difference in the crop up to the 5th leaf but the 5th leaf did appear to be thicker and wider on the treated side of the trial. How-ever, in the N-Lock treated crops the later varieties had bigger cobs with more grains pollinated. In the early variety groups-11 to 9—cob sizes were similar but the spindle was visibly bigger with more grains around the cob.
""Regarding N-Lock I was pleased with its performance in this for-age maize variety trial," explained Agrovista's agronomist Craig Green. ""I had always treated it with a bit of ""muck and mystery"" but Dow has got it right. When used on nitrogen limiting soils it works well. ""It certainly seems to prolong what little nitrogen there might be in the soil and it seems to have benefits in the maize. ""Average cob weight in the N-Lock treated varieties was consistently higher than in the untreated and showed a marked increase in Ramirez, Kougar, Dualto. Hobbit and Absalon varieties," he added.