Nitrogen (N) helps pasture bounce back after a drought. Getting pasture back on track after drought is crucial for animal production and profit, as well as ongoing pasture persistence.

Drought causes many spring tillers to die or become stressed, and summer tillers do not emerge. “Supporting autumn tillering is important to prevent pastures thinning out over winter and becoming vulnerable to weed invasion. This could reduce production and start a cycle of decline,” says Ballance Science Extension Officer Joshua Verhoek.

“Drought doesn’t affect all pastures equally, so they’ll need to be treated differently when the drought breaks.” Pastures dominated by productive species, with plants still alive or the crown of the plant at ground level, recover well with support. Those with weeds and large bare patches need regrassing.

The best time to apply N

“While it’s traditionally been advised to wait until pasture begins to recover from drought before applying N fertiliser, more recent research suggests that N applied after the first significant rains produces a similar pasture response to deferring it until further rain has fallen,” says Josh. The research, commissioned by Ballance and independently performed and reported on, was on droughtaffected land in the Bay of Plenty and Hawke’s Bay, and indicated that any N not immediately used is not lost, and produces a pasture response when more rain arrives.

“So the current recommendation is to apply N fertiliser to any live pasture as soon as the first drought-breaking rains fall, so you’re not missing any opportunity for growth in this critical period.” SustaiN®, which does not need 5 to 10 mm of rain within eight hours of application to reduce volatilisation losses, is an ideal N option for such conditions, or PhasedN®, containing SustaiN® and sulphur.

How to mitigate against risks

Drought followed by rain (or moist overcast days) is when the risk of nitrate poisoning is greatest, but certain practices can reduce the risk. “Avoid grazing within three weeks of applying N, or minimise intake one to two weeks after drought-breaking rain. If stock must be put on high risk pastures, the risks of nitrate poisoning can be reduced by limiting access overnight and in the morning, when nitrate levels are highest, feeding well on low nitrate feeds such as straw hay or silage before grazing, and stocking lightly to avoid hard grazing, as the lower parts of stems have the highest nitrate levels. These measures will protect recovering pastures as well as stock.”

“While applying N to dry ground is not ideal, if it’s your only opportunity, it will not leach but a small percentage could still be lost through volatilisation, and using SustaiN® minimises this loss.”

Fertiliser for regrassing

"Regrassing will be needed for pasture that’s beyond recovery. Assuming your base fertility is fine, you’ll need DAP or a similar starter product to drill with seed, followed by post-emergence N, provided growing conditions are good".

Josh Verhoek is a Science Extension Officer at Ballance Agri-Nutrients. For more information on post drought recovery - please contact your Nutrient Specialist.

To view our latest Fact sheet on ‘Post-drought feed management & dealing with feed shortages’ click here.