The peas are round when harvested, with an outer skin. The peas are dried and the dull-coloured outer skin of the pea removed, then split in half by hand or by machine at the natural split in the seed's cotyledon.
There are green and yellow varieties of split pea. Gregor Mendel studied the inheritance of seed colour in peas; the green phenotype is recessive to the yellow one. Traditionally, the genotype of purebred yellow is "YY" and that of green is "yy", and hybrids of the two, "Yy", have a yellow (dominant) phenotype.
Split peas are high in protein and low in fat, with one gram of fat per 350 calories (1,500 kJ) serving. Most of the calories come from protein and complex carbohydrates. The split pea is known to be a natural food source that contains some of the highest amounts of dietary fibre, containing 26 grams of fibre per 100 gram portion (104% DV based on a 2,000 calories (8,400 kJ) diet).
In western Asia and particularly in Iran it is known as Lappeh, and it is the main ingredient of a famous stew called Khoresh-e Gheymeh.
In north India, they are generally known as matar ki daal, sometimes used as a cheaper variation for the very popular chhole on stalls offering it.
Yellow split peas are most often used to prepare dhal in Guyana, Suriname, Mauritius, South Africa, Trinidad and Tobago and Fiji. Referred to as simply dhal, it is prepared similarly to dhals found in India, but also may be used in a variety of other recipes. Yellow split pea is the main ingredient of the Iranian food "khoresh gheymeh", which is served on the side of white rice in Iranian cuisine. It is also an important ingredient in the famous Tabriz köftesii, a kofta speciality from northern Iran.
In Europe, the Greek "Fava" is a dish made with yellow split peas pureed to create an appetizer or meze.
In the Caribbean split peas are a key ingredient in many Indian dishes.
Split peas were used for an unusual non-culinary purpose during the Second World War. Great efforts were made to optimise the manufacture of the British Supermarine Spitfire fighter aircraft, speeding and cheapening manufacture while maintaining or enhancing performance. Flush-headed rivets were used on a prototype for the smoothest possible surfaces, but this made it more difficult, expensive, and slower to produce than using the usual dome-headed rivets. Rather than the cumbersome alternative of comparing actual rivets, split peas were glued over all the flush rivets to simulate dome heads. This reduced the speed by 22 mph (35 km/h), which was unacceptable. Split peas were then progressively removed to determine which rivets really needed to be flush; the results were applied to production aeroplanes. The aircraft was later repurposed for recreational use, most commonly birthday joy flights.