Internal disorders such as IRS (internal rust spot or internal brown spot - IBS) can be reduced by a good calcium supply, in the form of calcium nitrate, at ridging or during tuber initiation. Experience shows that ensuring there is a minimum of 0.15% calcium in the peel, improves potato skin finish, boosts disease tolerance and minimizes IRS (Russet Burbank, USA).
Strengthening the tuber cell wall with calcium can help reduce the severity of Erwinia soft rot in storage.
Calcium also reduces the level of tuber skin diseases including black scurf and powdery scab leading to better skin finish. But high levels of free calcium in the soil, e.g. from recently applied lime, may increase the level of common scab (UK trials).
High levels of calcium in the tuber also reduce bruising risks at harvest and subsequent transportation. Varieties vary in their calcium uptake, as USA studies show.
Using calcium nitrate rather than ammonium nitrate minimizes bruising damage. In some varieties, damage can be halved.
The use of calcium in crops grown for seed boosts the following crop’s performance. A mother tuber enriched with calcium is faster growing and in better condition, thereby boosting yield per plant.
Calcium is a key component of cell walls, helping to build a strong structure and ensuring cell stability. Calcium enriched cell walls are more resistant to bacterial or fungal attack. It is critical during cell division and expansion, and is therefore essential prior to, and during, the rapid growth phase of tubers.
Calcium also helps the plant adapt to stress by influencing the signal chain reaction when stress occurs. It also has a key role in regulating the active transport of potassium for stomatal opening. It is particularly effective at helping reduce summer heat stress, minimizing wilting and leaf damage. Where this happens, yield improvements of 30% have been recorded.
|Calcium at potato growth stages|
|Ridging and hilling||Good skin quality, internal rust spot reduction, stress tolerance - drought / heat|
|Tuber initiation||Good skin quality, internal rust spot reduction, stress tolerance - drought / heat|
|Bulking||Improves skin finish and reduces disease impact|