Dhaka's residents can taste fresh vegetable as much as over 10 per cent of the demand through rooftop gardening.
Experts and officials said more than 10,000 hectares of space can be brought under rooftop gardening.
From such gardening, the city can get at least 0.14 million tonnes of vegetable free from chemical fertilisers and pesticides.
The yearly demand for vegetable in the city of 15.0 million population is nearly 1.36 million tonnes, according to the state-run Directorate-General of Food (DGoF) office.
Experts said to bring the maximum space of rooftops under farming, the government should have a building guideline for the architects, engineers and owners.
Dr M A Sobhan, agricultural scientist and also a rooftop gardener at Ahmednagar under Mirpur Section-1, has made garden on his rooftop comprising nearly 3-decimal (two katha) space.
He said the garden is meeting a notable volume of his vegetable demand.
"I'm growing vegetables like brinjal, lady's finger, pointed gourd, bitter gourd, chili, herbal plants like tulsi, basok, aloe vera in my garden," he said.
"Cow-dung and compost fertiliser is being used while turmeric, neem, custard-apple leaf etc are used as pesticides," he said.
Dr Sobhan collects 6 to 7 kilograms of vegetables per month from his rooftop.
"If one can manage good soil and use of natural manure, the production can be same as that of crop field," he added.
Deputy Director of the Department of Agriculture Extension (DAE), Dhaka District, Md Manzurul Hannan said there are 10,000 hectares of fallow rooftops under Dhaka South and North City Corporations.
He said: "If the rooftop spaces can be brought under cultivation, we can get at least 0.14 million tonnes of vegetable every year."
He said that the number of rooftop gardens is increasing in the capital.
"The DAE has taken programmes to encourage people, specially the retired officials, for gardening." he said.
According to DAE, in the metropolis, Tejgaon industrial area has 7,294 hectares of cultivable rooftop spaces of which only 15 hectares are occupied with gardens.
In Mohammadpur cultivable space is 654 of which 154 hectares are engaged in farming, in Gulshan, available rooftop spaces are 390 hectares of which 120 hectares are in use for farming.
An official in Mohammadpur Agricultural area, Md Abdulla Al Mahmud, informed the FE that in 2012, some 1100 buildings had garden on rooftop. The number increased to 2,580 in 2014.
He said garden of an 18ft/18ft rooftop can meet annual vegetable demand of a five-member family.
Agricultural officer of Tejgaon Md Ahidur Rahman said 2100 buildings in Tejgaon are now occupied with gardens. The number was less than 200 a decade back.
Dr Najim Uddin, senior scientific officer of vegetable division at Bangladesh Agricultural Research Institute (BARI), said every building should have to be designed in a way that allows rooftop gardening.
He said the farmland is reducing alarmingly per year so urban agriculture is now unavoidable.
"In a city like Dhaka, there is no chance of horizontal expansion of farming. We have only option to explore agriculture vertically," he said.
"The government should give special emphasis on rooftop farming not only in Dhaka but also in other big cities like Chittagong, Narayanganj, Gazipur," he said.
Meanwhile, joint secretary of Bangladesh Poribesh Andolon, an organisation working for environmental rights, Architect Iqbal Habib said the government should frame building guidelines for the architects, engineers and owners to ensure maximum rooftop space for farming.
"After using a land for making a building, 40 per cent of space remains on the rooftop for gardening. So, the city development authority (RAJUK) should not allow any residential infrastructures not having space for rooftop gardening," he said.
tonmoy.wardad@gamil.com
