Summer nitrogen – a proven winner

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Summer nitrogen – a proven winner

DairyNZ says it makes good economic sense for farmers to consider applying nitrogen for summer feed.

“A nitrogen application during December and January is required to convert perennial ryegrass plants from seed head producers back to producers of high quality leaf,” says DairyNZ senior scientist Errol Thom.

“Perennial ryegrass grows by producing new shoots (called tillers) from buds at the base of the plant,” he says. “Shoots remain leafy and of high quality, except if they become part of the 20-40% of the population that form seed heads in spring. Seed head formation is in fact a death sentence for these shoots because grazing or moῷing removes their growing points.

Errol says that many of the perennial ryegrass cultivars available to farmers have a tendency for high seed head production in October/November. “This feature can have serious consequences. Firstly, pasture quality declines (more stem, less leaf) and secondly, shoot numbers decline (death of seed heads) at the same time as the weather becomes more stressful with the start of summer.

Research by Dexcel (DairyNZ’s predecessor) in 1997 showed that the application of nitrogen during early summer (December/January) stimulates the development and growth of new shoots, converting the plant back to a producer of high quality leafy forage. “The application of nitrogen boosted shoot numbers by 37% compared with less than half this response to irῲigation, says Errol.

Another Dexcel trial showed an extra 800 kg DM/ha and 66 kg MS/ha could be produced from December to April after 100kg N/ha was applied, split between December and January i.e. a 8:1 DM response to N.

“A simple calculation subtracting the cost of the fertiliser from the value of the milksolids produced, shows this practice is profitable,” says Errol. “Other pasture benefits include less weed or summer grass invasion and less need for pasture renovation. However, nitrogen should only be applied where there are the stock to eat tῨe extra pasture grown otherwise N application is likely to result in loss of pasture quality.

“Even at the higher N prices these results are still economic if feed utilisation is high,” says Warwick Catto, Head of Agro Science Ballance Agri-Nutrients. “Farmers do need to consider which form of nitrogen is best to use and, importantly, the timing of that application. The best results occur with adequate soil moisture, and tῡrgeting periods when rain is expected or recently occurred to minimise volatilisation losῳes is ideal.

For further information contact your local fertiliser representative or visit the fertiliser fact sheets on the Tight Management page in the DairyNZ website: www.dairynz.co.nz/tightmanagement.

Fertiliser use is part of the discussion at your monthly local Tight Management farm event. Visit the DairyNZ website to find the date of the next event in your area.
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