Disruption of normal plant growth increases the probability for nitrate accumulation in leaves, stems and stalks. Plant damage from insects and certain weed control chemicals. Immaturity at harvest. In hay, enzymes continue to reduce nitrate for a short time during curing. Little further change occurs after the moisture becomes low enough to allow storage.
Microorganisms reduce the nitrate if incomplete drying or rewetting occurs.
In silage, anaerobic fermentation causes some nitrate reduction after ensiling. However, toxic, colorless gases may also be present. Since nitrogen oxides are heavier than air, accumulations may occur in the silo, silo chutes, around the base and in areas with little ventilation. Juices draining from silos may contain a high concentration of nitrate. Delay in harvesting of an immature crop for silage may result in a decreased nitrate content if further growth and grain development occurs.