Lathyrus Farming: Cultivation and Health Implications

Lathyrus (Lathyrus sativus), commonly called grass pea or khesari dal, is one of the oldest cultivated pulse crops in the world. It holds a unique position in Indian agriculture – valued by resource-poor farmers for its extraordinary resilience, yet controversial because of a naturally occurring neurotoxin in its seeds. Grown primarily as a catch crop on residual moisture in harvested paddy fields, this hardy legume thrives where most other crops simply cannot survive. Let’s understand what makes this crop both promising and problematic, and how modern science is working to make it safer.

What is Lathyrus sativus? 🔗

Lathyrus sativus belongs to the Fabaceae (legume) family and goes by several names – grass pea, chickling pea, chickling vetch, Indian pea, and khesari. It is a much-branched annual plant with slender stems growing 25-120 cm tall, pinnate leaves, and attractive blue, pink, or white flowers. The flat, oblong pods contain wedge-shaped seeds that are white, pale green, or grey-brown in colour.

Historically, grass pea was likely first domesticated in the Balkan region around 6000 BCE, and archaeological evidence of Lathyrus seeds has been found in ancient sites across Turkey, Iraq, and India. Today, it is cultivated widely in South Asia, East Africa, and parts of Europe. In India, the major grass pea growing states include Chhattisgarh, West Bengal, Bihar, Madhya Pradesh, and Odisha.

Why is Lathyrus called the “insurance crop”? 🔗

Grass pea has earned the nickname “poor man’s pulse” or “insurance crop” for good reason. It produces reliable yields even when all other crops fail. Here is what makes it so resilient:

Drought tolerance: The crop thrives in low-rainfall regions and can grow on residual soil moisture alone. It performs best with 400-650 mm of annual rainfall but can withstand severe moisture stress that would destroy lentil or chickpea crops.

Waterlogging tolerance: Unlike most pulses, Lathyrus can tolerate waterlogged conditions during its early growth stage, which is exactly why it works so well as an utera (relay) crop sown into standing rice before harvest.

Minimal input requirement: It requires very little investment in terms of fertilisers, pesticides, or irrigation. According to ICARDA, its low cost of cultivation and suitability for conservation agriculture make it ideal for smallholder farmers.

Soil improvement: As a legume, grass pea fixes atmospheric nitrogen through root nodules. According to India’s Directorate of Pulses Development, it contributes about 36-48 kg/ha of nitrogen to the soil for the succeeding crop.

Nutritional profile of khesari dal 🔗

Grass pea seeds are highly nutritious, which is why they remain an important food source for millions of people despite the health concerns. The seeds contain approximately 26-32% protein, 53-55% carbohydrates, and are rich in essential minerals and dietary fibre. The fat content is very low at around 0.9%.

In India, the seeds are traditionally dried, split, and consumed as dal or mixed with wheat flour to make rotis. In Ethiopia, the flour is used for preparing sauces that accompany injera (flatbread), while in Bangladesh and Nepal it goes into flatbreads like roti and pakoda. The leaves and immature pods are also used as vegetables. Beyond human food, grass pea straw and foliage serve as valuable animal fodder, and the crop is sometimes grown purely for livestock feed, especially in countries like Australia.

Agronomic practices for Lathyrus cultivation 🔗

Climate and soil requirements 🔗

Lathyrus is a rabi season (winter) crop that prefers temperatures between 15°C and 25°C from sowing through harvest. It grows well in all types of soils except highly acidic ones, but it particularly thrives in heavy soils, low-lying areas, loamy soil, and deep black soils – fields that are often unsuitable for other pulse crops.

Cropping systems and land preparation 🔗

The most common method of growing Lathyrus in India is the utera (paira/relay) cropping system. In this system, the seeds are broadcast directly among standing rice plants about 10-15 days before the paddy harvest, typically in the last week of September or first week of October. The grass pea then germinates and grows on the residual moisture after the rice is harvested. Under this method, no tillage is required.

When sown as a pure crop after rice harvest (late October to early November), one deep ploughing followed by cross harrowing and planking is recommended to prepare a fine seedbed.

Seed rate, spacing, and seed treatment 🔗

The seed rate varies depending on the sowing method. For broadcast sowing in the utera system, 70-80 kg/ha is used. For line sowing as a pure crop, the requirement drops to 40-60 kg/ha, with a recommended spacing of 30 cm × 10 cm.

Before sowing, seeds should be treated with Thiram at 3 g/kg of seed to protect against fungal diseases. After fungicide treatment, inoculation with Rhizobium and PSB (phosphate-solubilising bacteria) culture at 5-7 g/kg of seed enhances nitrogen fixation and phosphorus availability.

Nutrient management 🔗

Under the utera system, the crop utilises residual fertility from the preceding rice crop. However, grass pea responds well to phosphorus application. For normal sowing, the recommended fertiliser dose is 100 kg DAP + 100 kg gypsum per hectare, applied as a basal dose 2-3 cm below the seed using a ferti-seed drill. A foliar spray of 2% urea at the flowering and pod formation stages can also boost yield.

Irrigation and water management 🔗

Lathyrus is predominantly a rainfed crop grown entirely on residual soil moisture. However, if the crop faces severe moisture stress, one supplemental irrigation at 60-70 days after sowing can significantly improve production.

Weed management 🔗

One hand weeding at 30-35 days after sowing is generally sufficient. Alternatively, fluchloralin (Basalin) 45 EC at 0.75-1 kg a.i./ha can be applied as a pre-plant incorporation herbicide for effective chemical weed control.

Harvesting and yield 🔗

The crop is ready for harvest when pods turn brown and grains reach the dough stage with about 15% moisture content. Plants are cut, sun-dried for several days, and threshed manually or by trampling. Clean seeds should be dried to 9-10% moisture for safe storage. A well-managed pure crop can yield 8-10 quintals/ha, while the utera system typically gives 3-4 quintals/ha.

The health risk: lathyrism and the ODAP neurotoxin 🔗

The biggest concern with Lathyrus consumption is lathyrism, a neurodegenerative disease caused by a toxin called β-ODAP (β-N-oxalyl-L-α,β-diaminopropionic acid) present in the seeds. This neurotoxin affects motor neurons in the spinal cord and, when consumed in large quantities over an extended period, leads to irreversible spastic paralysis of the lower limbs in adults and can cause brain damage in children.

The key point is that lathyrism does not occur from occasional or moderate consumption. Research indicates that the disease develops when grass pea accounts for more than 30-40% of a person’s caloric intake for at least three months, especially in conditions of overall malnutrition. This pattern has historically been seen during famines and droughts, when impoverished communities had nothing else to eat.

In 1961, India banned the sale and storage of grass pea under the Prevention of Food Adulteration Act, though the ban was not uniformly followed across all states. Cultivation was never banned since farmers argued the crop was essential for animal feed, and household consumption continued, especially in eastern and central India.

An important complication: stress increases toxin levels 🔗

ODAP concentration is not fixed – it increases in plants grown under stressful conditions such as drought, salinity, and nutrient deficiency. This creates a dangerous paradox: the very famine conditions that force people to rely heavily on grass pea are also the conditions that raise the toxin content in the seeds.

Making grass pea safer: low-ODAP varieties 🔗

Significant scientific effort has gone into developing grass pea varieties with reduced neurotoxin content. Traditional varieties contain 0.5-2.5% β-ODAP, whereas modern improved varieties have brought this down to levels considered safe for consumption.

Collaborative breeding programmes between ICARDA and national research systems in India have yielded notable results. Key low-ODAP varieties released in India include:

Pusa-24: One of the earliest low-toxin varieties, released in 1966, with about 0.2% ODAP content. It served as the foundation for further breeding work.

Ratan (BioL-212): Released in 1997, developed from the Pusa-24 background with very low ODAP (below 0.1%) and recommended for the North East Plain Zone and Central Zone.

Prateek and Mahateora: Later varieties with ODAP content below 0.1% and yield potential of up to 1.5 tonnes per hectare.

Similarly, Bangladesh has released BARI Khesari-1 and BARI Khesari-2 varieties, and Ethiopia has released the Wasie variety – all with less than 0.10% β-ODAP.

In 2015, an expert committee comprising ICMR, ICAR, CSIR, and FSSAI recommended that the ban on grass pea sale be lifted in light of these safer varieties. As of early 2026, Indian Agriculture Minister Shivraj Singh Chouhan has confirmed that research is advancing to introduce newer, even safer varieties to the market, with ongoing multi-location trials testing stability of low-ODAP traits across different environments.

Reducing toxin levels through processing 🔗

Even with traditional high-ODAP varieties, simple food processing techniques can significantly reduce the neurotoxin content:

Soaking and discarding water: Soaking seeds for 6-24 hours and then throwing away the water can reduce ODAP by 80-90%.

Boiling and steaming: Moist heat treatment denatures certain anti-nutritional factors and further reduces toxin levels.

Fermentation and germination: Both lactic acid fermentation and sprouting before cooking are effective methods for lowering ODAP content.

Mixing with other cereals: Consuming grass pea as part of a diverse diet alongside cereals and antioxidant-rich foods reduces the risk significantly.

These traditional detoxification methods, combined with dietary diversification, make moderate grass pea consumption reasonably safe. However, during famine conditions – when water for soaking and fuel for boiling are also scarce – these precautions are often not practical, which is why breeding low-ODAP varieties remains the most critical long-term solution.

Pest and disease management 🔗

Lathyrus is relatively hardy against pests and diseases compared to other pulses, but a few common problems can affect the crop:

Aphids: Both adults and nymphs suck sap from leaves, causing browning and curling. Spray Dimethoate 30 EC at 1.7 ml/litre or Oxydemeton methyl 25 EC at 1 ml/litre of water.

Rust (Uromyces fabae): Pink to brown pustules appear on leaves and stems. Growing early-maturing varieties, seed treatment with Carbendazim at 2 g/kg, and spraying Mancozeb 75 WP at 2 g/litre help manage the disease.

Downy mildew and powdery mildew: These fungal diseases affect aerial parts and can be controlled with Mancozeb sprays or Wettable Sulphur at 3 g/litre.

The future of grass pea in Indian agriculture 🔗

Despite its controversial history, Lathyrus sativus has a strong case for revival. India has millions of hectares of rice fallows – land that sits idle after the kharif rice harvest – where grass pea can be grown as a second crop with virtually no additional investment. ICARDA estimates that at least 0.5 million hectares of rice fallows could be brought under grass pea cultivation, boosting both pulse production and farmer incomes.

With climate change making rainfall more unpredictable and droughts more frequent, a drought-proof, waterlogging-tolerant, nitrogen-fixing pulse crop becomes even more valuable. The development of low-ODAP varieties like Ratan, Prateek, and Mahateora, combined with ongoing research into genetic modification to further reduce or eliminate the toxin, is gradually removing the health stigma attached to this crop.

The challenge now is scaling up seed production and distribution of improved varieties, educating farming communities about safe processing methods, and finalising regulatory clearances for commercial sale across all Indian states.

What do you think? Given that low-toxin varieties now exist and simple processing can further reduce risk, should India fully lift the ban on khesari dal and actively promote it as a climate-resilient pulse? Could grass pea play a bigger role in addressing India’s protein deficiency, especially among economically weaker communities?

References

1. https://en.wikipedia.org/wiki/Lathyrus_sativus
2. https://www.feedipedia.org/node/285
3. https://icarda.org/media/news/grasspea-back-menu-indias-agriculture
4. http://dpd.gov.in/Lathyrus.PDF
5. https://en.wikipedia.org/wiki/Neurolathyrism
6. https://www.downtoearth.org.in/food/rumoured-forbidden-it-s-time-to-banish-fears-around-khesari-dal-and-relish-the-nutritious-legume-92976
7. https://icarda.org/publications/29993/genetic-improvement-grass-pea-low-neurotoxin-b-odap-content
8. https://www.sciencedirect.com/science/article/pii/S2214514116300629
9. https://www.prokerala.com/news/articles/a1726751.html