Night nappies have a greater absorption capacity, they can require a little more effort to remove the heavy urine load from the nappy. This along with a good wash routine will prevent smells and the development of ammonia.
The nappy can be put straight into a pre wash cycle first thing in the morning, or put in the daily pre wash cycle that evening. This is a suitable option if using a 60 degree cycle that lasts at least an hour, with a good quality detergent. This option is works better in Front loaders, as they tend to produce better results than Top loaders, however if it works in your Top Loader and it is easier, then use this option.
Or hand washed in hot water with a small amount of laundry detergent, spun in the washing machine and dry pailed.