Nitrogen, Nitrogen Deficiency, Low Nitrogen, Mineral Deficiency, Nutrient Deficiency
Most soils are deficient in nitrogen, which is why gardeners have to supplement their media with fertilisers and manure. Soil lacking organic matter can cause nitrogen deficiencies in plants. It can also occur when no fertiliser or too little fertiliser is applied to crops. A garden with no peas or beans, or, possessing lots of Brassica plants will probably experience nitrogen-deficiencies. Likewise, using peaty soils can cause the same problems. Nitrogen is essential for healthy growth because it's one of the main elements found in proteins and many other plant-components.
Leaves don't grow to full size.
Brassicas can produce yellow, red or purplish tints.
Symptoms appear on older leaves first, spreading upwards.
Growth becomes stunted or weakened.
Flowering and fruiting may be delayed. Less flowers/ fruits are produced.
Before or during planting, be sure to use a nitrogen-containing fertiliser. Remember to reapply as per manufacturers instructions. It's recommended applying nitrogen-containing fertilisers following heavy rainfall or following harvest. A more organic approach would be to use manure or compost from the compost bin, which is sufficient for a steady release of nitrogen and is not as readily 'leached' as with artificial fertilisers.