Lupins are legumes belonging to the family Leguminosae and the sub‐family Papilionaceae which contain approximately 12 000 species. Since they are legumes, lupin plants develop root nodules containing bacteria which turn nitrogen from the air into nitrates and can be used by the plant as a nutrient. This means that the lupin crop can be grown with little use of fertilizer.
Lupins are a very old crop. Two species have been cultivated for 3 000 years in the Mediterranean basin and parts of South America. These species have large seeds which can be used as grain and the modern cultivated lupins are all large‐seeded varieties.
Lupins stand 0.3 – 1.5 metres tall while some other species can reach 3 metres and some even up to 8 metres in height. The colours of the leaves are green to a grey‐green with some species bearing silver hairs. The leaf is divided into 5 – 28 leaflets with the flower produced in dense whorls which are 1 – 2 cm long. The fruit is a pod containing several seeds. The crop can be used as a forage crop or for the grain as they contain a full range of amino acids. It is becoming more and more recognised as a cash crop or as an alternative to soyabeans.
Table 1: Shows the different species and common names
One interesting fact about the large‐seeded species of lupins is that they have different numbers of chromosomes. These are the genetic material carried in the nuclei of the plant cells and means that they cannot be cross‐bred to produce hybrids.
Lupins have always been recognised for their ability to grow on very poor soil and that they improve both the structure and nutrient content of soils. Since they are legumes, a crop of lupins will add nitrogen to the soil. The ancient Egyptians, Greeks and Romans used the crop for green manuring, the seeds for stock feed, human food and use in medicines. The old types of lupins contained an alkaloid poison in the seeds and had to be steeped in water and boiled before being eaten. Modern lupins are selected free of this alkaloid poison and are called ‘sweet lupins’ and are widely grown in Poland, Russia, Australia and the Cape region of South Africa.
CLIMATE AND SOILS
Lupins like an average day temperature of 20 – 25o C and night temperatures of 10 ‐ 15oC. Temperatures above 26oC result in increased abortion of flowers and young pods. Lupins are a cool season crop that can be grown under dryland conditions in the high altitudes of Kwa‐Zulu Natal. In other areas the crop can be grown in winter under irrigation and will tolerate cool conditions and frost well. Lupins are a hardy plant.
The crop does well on coarse‐textured, well‐drained soils that are acid. They are suited to sandy soils and if grown on neutral or alkaline soils suffer from the deficiency of a number of induced trace elements and minerals, particularly iron, manganese and cobalt. Lupins are very sensitive to water logging and require a deep soil as the taproot may reach a depth of 2.5m.
PLANTING DATES, POPULATION AND SPACING
Planting in the cool summer areas should be from mid‐October to mid‐December after good rains have started. In the winter growing areas, the crop needs to be planted from mid‐April to mid‐May. Lupins should be planted at a depth of 30 – 50 mm below the soil surface. If the seeds are sown any deeper one runs the risk of causing damping off and seed rot.
Seed can be sown in drills with row spacings of between 37 and 45 cm or more often broadcast and harrowed in with light harrows. Seed drilled at the rate of 75 – 100 kg/ha will give a plant population of between 150 000 – 200 000 plants/ha or at a rate of 100 – 150 kg/ha will give a plant population of 200 000 – 400 000 plants/ha.
The seeds need to be inoculated before being planted. The inoculant should be applied as slurry. Dissolve 5 grams of the sticker methyl cellulose in 500 ml of water with 250 grams of inoculant added to the mixture. This should be sufficient to mix with 50 kg of seed.
Lupins are legumes and are normally sown without any nitrogen provided the seed has been properly inoculated. Crops being harvested for seed can be given a small amount of nitrogen in the seedbed to establish the crop before the root nodules are formed. Once nodulation starts the plants will provide their own nitrogen.
Maintenance level of 20 kg/ha of phosphorus is required. Fertilisation should be subject to a soil analysis and fertilized accordingly.
Weeds can be controlled by an effective herbicide programme. These are some chemicals that are registered for the use on lupins:
Diflufenican: is used for broadleaf weeds as a pre and post‐emergent herbicide and sprayedat a rate of 150 ml/ha on soils that contain less than 20% clay and 200 ml/ha on soils which have a clay content greater than 20%.
Quizalofop: is used as an early‐post emergent and used at a rate of 350‐500 ml/ha in 150 –300 litres of water/ha.
Cycloxydim: is used as a post‐emergent of grasses and sprayed at a rate of 0.4‐2 litres/ha.
4. PESTS AND DISEASES
Lupins are attacked by nematodes (eelworms) and not be grown in the same rotation as tobacco, dry beans, soyabeans or sunflowers. Nematode attack can be prevented by growing the crop on clean ground or fumigating the soil before planting. Lupin Maggot Flies, Aphids and Budworms also attack the crop and can be killed by spraying with an insecticide. The chemical terpenic polymer can be used at a rate of 50 ml/100 litres of water with a dosage of 500 litres/ha of water mixture to ensure a full coverage of the plants.
Lupins are subject to the following fungal diseases:
Brown Leaf Spot; Grey Leaf Spot;
Fusarium Wilt; and Mildew.
These can be prevented by spraying the crop with a fungicide such as Penconazole at a rate of 300 ml/ha with a spray volume of 300 – 500 litres/ha of water. Lupins are attacked by Mosaic Virus spread by aphids and seed selected from disease‐free stock.
The main control measure for disease and insect pests in lupins is to plant resistant varieties, ensure the seed have been certified and rotate with maize or wheat for at least 2 seasons before planting. The diseased plant material and other plant debris should be deep ploughed into the soil to break the cycle.
The crop can be harvested in any of the following ways:
Ploughed in as a green manure before the seeds form in the seed pots. This enriches the soil by adding both organic matter and nitrogen from the breakdown of the nodules on the roots of the plants. When used this way the crop is broadcast as a catch crop;
Grazed by cattle or sheep or cut and fed as green roughage; and
Allowed to mature and harvested for the seeds which can be picked and removed from the pods by hand, or the use of combine harvesters which are suitable for wheat and soyabeans. The crop is ready to harvest when once the pods have turned a creamy brown.
Seeds of bitter lupins contain 1 – 20% of alkaloid poisons. These can cause acute intoxication in both man and cattle and can be fatal. However, no poisoning has been reported from alkaloid‐free or sweet lupin seeds.
The main value of lupin seed is the high protein content together with fairly high levels of crude fibre. The seed coat contains nearly all the fibre and very little protein so that removing the seed coat reduces the fibre and increases the protein content of the seed meal. Both the protein and fibre have a high digestibility for all classes of stock and particularly pigs, lambs and dairy cows. The table below gives figures for the average composition of lupin seeds together with figures for protein and oil of seeds. The figures for soya bean meal are included for the purpose of comparison.