Assessment of the quality and reserves of bat guano at Chipongwe and Kapongo caves near Lusaka as fertiliser material

There are many bat guano deposits in Zambia but their characteristics and sizes are not well known. The Chipongwe and Kapongo Caves, located within about forty km south of Lusaka, are developed in the white and grey banded crystalline limestone and dolomite marble of the Lusaka Formation and Mampompo Formation, respectively. The caves were created as a result of dissolution of calcium carbonate. The main objectives of this study were to assess the quantity and quality of bat guano in the two caves. In order to achieve the above objectives, mapping of the caves was undertaken and bat guano samples collected for chemical analysis. Both caves are colonised by bats and as such have accumulations of guano, which have been deposited on the carbonate rocks. The estimated resource of bat guano at Chipongwe Cave is 1218 tonnes averaging 0.46% N, 4.03% P and 0.12% K and at Kapongo Cave is 2822 tonnes averaging 1.94% N, 8.41% P and 1.24% K. The N-P-K ratios for the bat guano from the Chipongwe and Kapongo Caves are 4:34:1 and 2:7:1, respectively. These ratios show that generally bat guano from both caves is relatively depleted in nitrogen and potassium, which are more mobile elements and enriched in phosphorous, a relatively immobile element. The N-P-K ratio for internationally traded bat guano is typically 3-10-1, 8-4-1 and 10-3-1 and such guano has been recommended for fruit trees, vegetables and flowers. The Chipongwe and Kapongo bat guano is similar to the internationally traded guano with N-P-K ratio of 3-10-1 and as such would be suitable for growing vegetables, fruits, flowers and maintenance of lawns.