Nutrients need to be applied as accurately as possible to the zone of uptake, before or at the time that the crop needs them. Failure to ensure that each plant gets the right balance of nutrients can spoil crop quality and reduce yield.
Pre-planting fertilisers are either broadcast or banded. Generally, banded fertilisers give the best results.
When broadcasting fertiliser it is essential to ensure that it is evenly distributed. Small variations in distribution of plus or minus 10% will result in yield losses of up to 1.3t/ac.
When banding fertilizers it is important to keep the fertilizer away from the seed pieces. On low Cation Exchange Capacity (CEC) soils the band should be 10 cm (3.9 in) below and 10 cm to the side of the seed piece. On higher CEC soils the fertilizer band can be placed closer to the seed piece. (e.g. 7 cm or 2.8 in to the side and below the seed). Fertilizer must not be banded beside the seed piece, as germination will be reduced. See image below:
Nutrients need to be accurately timed to coincide with critical growth stages; for example calcium at tuber initiation. Because different varieties initiate tubers at different times, it is important to visually check when the first tubers are being formed in order to ensure maximum nutrient efficiency.
With drip irrigation small quantities of nutrients are fed throughout the growing season. The irrigation tape must be placed near the top of the ridge to ensure good soil water and nutrient management in the potato root zone.
Overhead systems such as center pivots, allow growers to feed soluble fertilizers constantly throughout the watering period.
Foliar nutrient applications need to be applied with sufficient water to give good canopy coverage and penetration, but not to the point of run off.