The Goilala District lies north of Port Moresby, covering a total land area of about 7,254 square kilometre (km2). The district is characterized by very rugged topography.
The District Headquarter in Tapini is accessible through the Goilala Highway that leads into the mountains from the Hiritano Highway at Aoropokina.
The climate of the District is largely influence by its physiographic setting especially the effect of the Owen Stanley Ranges. Mean annual rainfall ranges from 2000 mm on the plains to 4000 mm up towards the high mountain ranges. The annual mean temperatures range from a maximum of 320 to a minimum of 190. Further inland towards higher altitudes the temperature decreases to 160 maximum at the upper scale and 90 at the lower scale or minimum.
The major landform types include mountains (6851 km2), flood plains (301 km2), hills (32 km2) and plains and plateaus (70 km2).
More than 70 % of the district comprises deeply dissected valleys and mountains. The major river systems include the Kunimaipa and Alabule Rivers, Auga Dilava Udaba river systems that flow towards the Central coast especially the Kairuku Hiri District. Vegetation along this river systems leading into the low lands comprises mostly natural vegetation, grassland areas with pockets of woodlands, scrub-lands, swamp woodlands and mixed herbaceous swamp vegetation.
Soils of the district are categorized into four main groups according to the dominant physical factor. Thus the major soils of the district are moist, wet, shallow and peat soils. The fertility of the soils are determined by the factors of soil formation especially parent material and climate. Representative soil profile chemical data indicate the soils of the district to be naturally fertile
Various crops were evaluated for their suitability in the district using the PNG Land Evaluation System (PNGLES). Suitable crops include Arabica coffee (4243 km2)), vanilla (1153 km2), cardamom (3554km2), pyrethrum (3672 km2), chilli (3785 km2), potato (2272 km2), citrus (3415 km2), pepper (1812 km2), and pineapple (3785 km2).
Livestock development at a village to medium scale has a potential with an area of 1509 km2 identified as moderately suitable.
In general the climate and soils pose no major constraints to agriculture development. However, the biggest constraints are associated with the physical setting of the district – it being very rugged in nature couple with this lack of proper basic infrastructure such as roads.
Rainfall is high throughout the year and may vary over short distances from 3000 to 4000 mm (McAlpine, et al 1983, PNGRIS, 1997). In general rainfall increases from the western ranges (Tapini) to the eastern ranges (Woitape) from than 2000 to 4000 mm and is fairly evenly distributed during the high and low rainfall months. Mean monthly rainfalls are generally > 100 mm with the wettest time of the year being December to March. A short dry spell occurs during the months of June to August where mean monthly rainfall may range from 60 mm (Tapini) to 113 mm (Fane).
Temperatures depend on altitude. Temperature decreases as altitude increases at a lapse rate of 0.5 degree per 100 m rise in elevation. The highest point in the district is 2400 amsl. The mean maximum temperatures at lower altitudes (300-600 m) range between 30-32 degrees. The mean minimum temperature ranges between 19-23 degrees. At the increased altitudes, over 2400 amsl, the mean maximum ranges between 16-19 degrees while the minimum temperature ranges between 9 and 7 degrees. Frost occurs occasionally and may have an effect on crops.
Data from the wet and dry bulb temperature taken between 0900 and 1500 hours daily are used to calculate relative humidity (RH). As a general trend RH, decreases as altitude increases. However, RH for the Goilala district is consistently high with values between 80-85 % and an annual relative index around 82 % (McAlpine et al, 1983). Seasonal variation is between 3 and 7 % due to the higher altitudes.
The vegetation of Goilala district comprises mostly of the natural forest types. These consist of coniferous lower montane forest, medium crown lowland hill forests, lower montane forests, small crown lowland hill forests, mixed herbaceous swamp vegetation and open forest plains. Grassland vegetation make up 3.3 % while 1 % comprise of the swamp woodland and mixed herbaceous vegetation.
The geology underlying the Goilala District is complex. Several rock types have been identified using the PNGRIS (1995) data. These are mostly of Tertiary origin overlain by Quaternary volcanic deposits. (Bleeker, 1983) These include the low grade Owen Stanley metamorphics, low-grade volcanics, mixed undifferentiated metamorphic, coarse-grained sedimentary, basic to intermediate volcanic, fine grained sedimentary rocks. Holocene alluvial deposits underlie the back swamps and flood plains.