Assessment of Phosphorous Release from Bat Guano with Respect to Their use as Organic Fertilizers in Crop Production

Abstract

Bat guano from Kisarawe cave A (BGK-A), Kisarawe cave B (BGK-B) and Sukumawera cave (BGS) in Tanzania were studied in a laboratory incubation experiment for 112 days to assess the phosphorus release patterns and establish the pick periods of P mineralization. Total P contents from BGK-A, BGK-Band BGSwere 8.55, 7.03 and 3.45 % respectively. Bat guano from each deposit mixed with soil at varying rates of 0, 10, 20, 40 and 80 mg P 200 g-1soil. The experiment wasarranged as3×5 factorial in randomized complete design (RCD) with three replications. Results showed a gradual increase of P availability from 28 days to 84 days of incubation; followed by a gradualdecrease up to the 112thday of incubation.P release(availability)fromthe studiedguano was in the order of BGK-B < BGS < BGK-A. BGK-A indicated higher potential as an alternative P source for agricultural application. P-source and application rate had a significant interaction effect(P < 0.05) on P release at all incubation intervals when P was applied ata rate of80mg kg-1soil. The soil pH showed very strong negative correlation (r > 0.8) with Preleased in the soilthroughout incubation period.It was concluded that P release from the three bat guano deposits is gradual and reaches the pick in almost three months after application. Thus, guanoshould be applied at least two months before planting for more effectiveness of P release.