Incorporating Rain Water Harvesting into the Green house Farming

Abstract

A greenhouse is a structure where crops could be grown under controlled conditions. A greenhouse is needed in experimental determination of optimum conditions under which a crop(s) will perform the best. Rainwater may be used to water the crops inside a greenhouse.

A 9m x 6m green house of roof slope 20 degree was constructed according to standard recommended by FAO/SIDA. The roof plan area was determined and quantity of harvestable water was calculated using standard formula. Gutter brackets were fabricated in the Department of Agricultural Engineering, LAUECH. Roof gutter size was determined using standard equation. The roof gutter was attached to the fascia board of the roof, using the gutter bracket at a slope of 1.5% and projection of 0.12m Water from the storage tank was diverted to inside the green house with the aid of pipe network and a tap.

The results of rainfall analysis indicated that Ogbomoso has a mean annual rainfall of about 1.2m with a standard deviation of 0.27m and a coefficient of variation of 0.002m, which indicated that the rainfall is fairly well distributed. The rainfall pattern was found to be bimodal in nature, peaking in the month of June and October. The roof plan area was found to be 40m square. The theoretical harvestable water was found 36m square per annum. The required gutter diameter was determined to be 0.086m but a commercially available gutter diameter 0.1m was used.

Rainwater from greenhouse roof, if well harvested and stored, may be used to water the plants inside the greenhouse. Adequate storage facility needs to be provided for harvested rainwater. Experimental crops of known crop water requirement should be grown in greenhouse with the harvested rainwater.