Experts at the National Horticultural Research Institute of Nigeria (NHRIN), Idi-Ishin, Ibadan, have sounded caution on suitability of roof harvested rainwater as source of irrigation.

The experts who commented on this issue included the Head, Farming Systems Research, NHRIN, Dr. Akintola Olayiwole Akin and Prof. Sangodoyin A.Y. both of the institute in a joint paper made at the 2010 annual seminar of Centre for Technical Agriculture (CTA) in South Africa between November 21 and 26 at the Premier Hotel, Gauteng Province.

In the paper which dwelt on “The Suitability of Domestic Roof Harvested Rainwater as source of Irrigation Water for Homestead Gardening,” they said that homestead gardening could be a way of ensuring good quality foods in developing countries.

They pointed out that contamination of surface and shallow water source is a big challenge but the use of Domestic Rood Harvested Rain Water (DRHRW) could be an alternative source, noting that previous work on DRHRW had focused on quantity rather than quality of harvested rainwater.

Therefore, they concentrated in this case study on quality of DRHRW under varying environmental conditions in relation to its use for irrigation of homestead garden.

For them, the methodology deployed included site study of an area in Ibadan and Lagos in Southwestern Nigeria and Port Harcourt in South-south region of Nigeria.

Also, they said, the study covered residential area in Ibadan, industrial area in Lagos and gas flaying zone in Port Harcourt city, stressing that samples were collected at 12 locations per city in three replicates from four different roof materials across three ages of roofs in service conditions at about 1.5m above the ground surface.

These samples were prepared and handled in line with the standard procedures outlined by John-de-Zuane and World Health Organisation in 2004.

Results, they stated were microbiological quality via Escherichia coli, which was isolated from almost all the samples considered.

“The value was observed to be below the infection dose and would be of major concern only if the water is used to irrigate fruit crops and the fruits are eaten without washing,” they advised.

On the Pseudomonas fluorescence which was detected in 25, 50 and 70 per cent respectively in the samples, they said, were from residential, industrial and gas flaring regions in that order.

A Domestic Rood Harvested Rain Water that is contaminated with Pseudomonas Fluorescence, they said, for instance, could be a good source of irrigation water and may assist the farmer in curtailing the problem of nematode invasion thereby increasing crop yield.

Age of the roof and type, they maintained do not have major impact on the distribution of e. Coli and P. Fluoresce.

As postulated by the experts, especially Akintola in a chat with the media, the chemical quality such as Lead and Cadmium have various results.

He elucidated that Lead, for instance, was detected in 62 per cent of samples from residential and all the sample from industrial and gas flaring zones.

Equally, he said that Cadmium was detected in all the samples from industrial area as well as in 69 and 84 per cent of samples from residential and gas flaring areas.

Despite the detections, Dr. Akintola said that it does not pose any risk to its being use to irrigate homestead gardening.

“On the other hand, it is an indication of its suitability for irrigation purposes,” he said, insisting that the concentration of iron detected is within the safe mode recommended for use by notable health authorities for use even for potable uses.