The curse of Blossom End Rot is caused by insufficient calcium. Insufficient calcium is not usually due to a shortage of calcium itself but to a lack of water. Water being the method by which calcium travels round the plant. No water to carry it – no calcium.
But what if there were insufficient calcium in the soil – how can this addressed? By liming i.e adding lime to the soil.
Lime is usually added to the soil to raise its pH, to increase the alkaline balance of a soil. This is especially true of sandy soils where rain and water wash easily through, taking or ‘leaching’ nutrients with them. Calcium is what makes a soil alkaline.
And calcium is introduced into the soil in the form of lime. ( It helps at this point, to disassociate any links your mind might make to small, green, citrus fruit, think instead of those limes as ‘red herrings’ in this context.)
And calcium is also the nutrient needed to build a plants’ cells – and if cells are properly built – BER doesn’t occur.
In this day and age useful (and not so…) products come with catchy and solution-orientated names. So lime, with its simple (and pH misleading) name is a bit of mystery. Here I try and decode it. It starts with quarried chalk or limestone. And then becomes :
Calcium carbonate – ordinary lime (CaCO3). Ground to a fine powder and variously referred to as: garden lime/carbonate of lime/ground limestone/ground chalk.
Quicklime or burnt lime – calcium oxide – chalk or limestone heated in a lime kiln.
Slaked or hydrated lime – calcium oxide – treated with water, making it calcium hydroxide.
But no matter how treated, all limes revert to calcium carbonate when incorporated into soil.
Dolomitic Lime, slightly different, in that it is ground from quarried rock and in addition to calcium contains magnesium.
So all these limes raise the alkalinity of the soil and are a source of calcium. One thing not to do though is apply any kind of lime to the soil at the same time as incorporating manure. They react with each other and result in valuable nitrogen being lost (from soil to atmosphere) in the form of ammonia.