Grafting and polyhouses improve tomato yields for Indian smallholders

A study led by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) has found that combining vegetable grafting with protected cultivation can significantly improve yields and profitability for smallholder farmers in India.

Published in Frontiers in Agronomy, the research examined tomato farming using naturally ventilated polyhouses, a low-cost greenhouse alternative. When grafted tomato seedlings were planted under polyhouse conditions, yields increased by nearly 64% compared to non-grafted tomatoes grown in open fields. The study attributed the higher output to extended harvest periods, improved plant vigor, and greater resilience to heat and soilborne diseases.

Vegetable grafting involves attaching a high-yielding scion to a disease-resistant rootstock. In this case, the rootstock used was Solanum torvum, which is known for its tolerance to abiotic stress and soil pathogens. The approach is already common in East Asia but remains underused in most Indian smallholder systems.

The economic returns also favored the combined method. Grafted plants grown in polyhouses delivered the highest net income and benefit-cost ratios among the treatments tested. Researchers cited improved photosynthetic performance, larger leaf area, and more consistent fruit development as factors contributing to higher output and returns.

The trial is part of a broader program between ICRISAT and the Andhra Pradesh state government, aimed at increasing smallholder incomes through horticulture. According to the study, productivity gains ranged from 30% to 150% across different locations and crop cycles.

Scaling hurdles remain despite promising results

While agronomic benefits are clear, broader adoption faces cost and logistics constraints. Building a naturally ventilated polyhouse with drip irrigation over one acre costs roughly Rs. 18 lakhs ($21,600). Establishing a grafted seedling production unit adds another Rs. 3.5 lakhs ($4,200). Grafted seedlings themselves cost between Rs. 1.5 to Rs. 2.5 ($0.018 and $0.030 respectively) apiece, depending on production scale and technology used.

These costs present a barrier for smallholders, even with subsidies covering up to 50% of infrastructure expenses under India’s national horticulture program. In addition, the labor-intensive nature of grafting and a shortage of skilled workers further slow scale-up efforts.

Despite these challenges, some private nurseries have begun producing grafted seedlings commercially. In one example from Karnataka, a nursery trained under a government-supported program scaled up to produce 50,000 grafted seedlings monthly. But such examples remain limited.

Researchers argue that success on a wider scale will depend on stronger public-private partnerships, targeted financial incentives, and farmer training programs. Standardized protocols and expanded extension services are also seen as key to reducing entry barriers and ensuring consistent plant quality.

While the study focused on tomatoes, researchers say the grafting method is applicable to other vegetables, including eggplant, cucumbers, and melons. As climate change increases production risks, the technique offers a non-GMO, science-based method for improving both resilience and returns in vegetable farming.