Monika Parajuli 

Urbanisation has become a common phenomenon all over the world. Nepal falls under one of the top ten fastest urbanising countries in the world.
Urban population in Nepal is reported to be 19.74 per cent in 2018, according to the World Bank's collection of development indicators. The majority of population is concentrated in the Kathmandu Valley.
Amidst the growing urbanisation, we are losing our agricultural lands and the need for feeding population is increasing every minute. The cultivable land in Nepal has decreased by 30,334 hectares in the fiscal year 2016/17 (Source: Data of economic activities, Nepal Rastra bank).

A Challenge
It has become a challenge to maintain food security in coordination with the alarming population growth. In the urban areas, rooftop farming has emerged as a favourable option to tackle this situation.
Rooftop farming, popularly known as "Kaushi Kheti" is the cultivation of different food crops in the roof of buildings which is usually done in the city areas where there is no adequate agricultural lands. Rooftop gardens provide nutritious food all around the year sufficient for both high income and low-income households.
A wide range of fruits and vegetables like spinach, cucurbits, cauliflower, citrus, tomatoes, garlic, onions, guava, strawberries, herbs and spices can be grown on vacant spaces on the rooftops.
Rooftop farming comprises of various techniques such as Aeroponic Agriculture (agriculture done in the air without soil), Hydroponic Agriculture (agriculture done in a nutrient solution without using soil) and traditional agriculture (agriculture done in soil). The plants can be kept on container pots, fish crates (foams), drums, plastic jars, bottles and plastic bags. Moreover, the whole of the floor can be filled with soil for higher density planting by waterproofing the concrete roof. For people who want a more sophisticated and well-managed rooftops gardens, Tower garden i.e, a vertical hydroponic or aeroponic growing system can be maintained.
For the planting material, garden soil can be replaced by mixing it with 40 to 50 per cent of compost manure or straw to reduce the weight content of the soil. Coco peat, vermiculite, perlite, rice hulls and sand can be an alternative for the regular garden soil as they are more stable, water retaining and of lighter weight content.
When the heavy garden dirt is used, the excess moisture from it could damage the concrete floor and in extreme conditions, could even cause roof collapse. The planting material should contain required nutrients, balanced PH and should have a good water retention and provide sufficient air for the plants to breathe. It is important for the material to be heavy and stable enough to resist wind and water but not so heavy as to compromise the structure of the floor.

Direct Sun Rays
As the rooftop is elevated at a certain height, it gets direct sun rays and strong wind which could be harmful to the plants. Installation of green roofs has become quite common as they act as an insulation layer, maintain coolness, protect the plants for direct sunlight and provides shade. Green roofs retain more than 60% of rainwater which can be collected and used later on for irrigation. For the protection from direct strong wind, thin shade cloth, netting or some shelter and windbreaks can be used. By differentiating the biodegradable and non-degradable kitchen waste of the households, compost manure can easily be made which aids fast and healthy growth of the plants.
Rooftop farming increases the availability of healthier and nutritious food in the city area and also promotes local production. Special off-season vegetables can be produced by maintaining suitable green-house conditions. Fresh products can be easily marketed locally and it helps reduce the transportation cost and post-harvest losses. Rooftop farming not only provides us with fresh, organic and chemical fertilizer free products but manages to play a significant role in urban environmental management as well. It has been reported that air pollution has been decreased in local areas surrounding rooftop gardens.
The annual loss of primary forest has been of 151 hectares in 2018AD and sums up to 3,437 hectare from 2002-2018 AD. (Source: Deforestation statistics for Nepal, rainforests.mongabay.com). Deforestation and urbanisation have deteriorated the environment and increased the possibility of natural calamities every year.

Easy Alternative
Rooftop farming is any easy alternative to restore greenery in the places lacking cultivable lands. It helps enhance the urban landscape and promotes greenery in the cities. Studies have found that exposure to natural vegetation and greenery has ultimately led to have benefits on psychological and mental health of people. The increased fuel and energy use in the urban areas has led to global warming and climate change. Rooftop garden helps to make the city eco-friendly and also cools down the building leading to decreased carbon emissions.
In the current time, most of the residents of the city areas can be seen readily doing planting in their roofs and terraces. Rooftop farming is getting a traction in the urban areas because it is easy to handle, economic and has an array of health and environmental benefits. It makes the city green, eases waste management, enhances the air quality and easily provides unadulterated, fresh and nutritious food products.

(Parajuli is a BSc. Agr. student)