Tanzanian Bat Guano as an Alternative Source of Phosphorus for Organic Rice Production

Many tropical and subtropical soils are low in phosphorus. This is partly because of excessive weathering, high phosphorous (P) fixation rates, and low P levels in soil parent materials. Continuous removal of P from soils by crops, coupled with limited application of P fertilizers, is also among the contributing factors for low P in soils. Phosphorus is among the most limiting macronutrient in rice (Oryza sativa L.) production. This study was conducted to evaluate the suitability of bat guano collected from Kisarawe (BGK-A and BGK-B) and Sukumawera caves (BGS) in Tanzania. The screen-house experiment at the Sokoine University of Agriculture was designed as a 4 × 6 factorial experiment conducted as a randomized complete block design (RCBD). Guano and triple superphosphate (TSP) were used as standard fertilizer at six P application rates. The yield of rice in response to applied TSP was comparable to applied guano but in the order TSP > BGK-A > BGS > BGK-B. All parameters increased with an increase in applied amounts of P from guano and TSP. Besides this study revealed the significant (P = .05) interaction between P sources and P rates on plant height (PH), micronutrient concentration and dry matter (DM). The study showed the correlation between grain yield (GY) and other crop components of dry matter (DM), the number of panicles (NP), Panicle height (PAH), plant height (PH) and number of tillers (NT). A significant and positive correlation was found for the GY-DM (r = 0.58, P = .05), GY-PAH (r = 0.65, P < .001), and GY-NT (r = 0.420, P = 0.1). But strong positive correlation was found between GY-PH (r = 0.76, P < .001) and GY-NP (r = 0.84, P < .001). It was concluded that studied guanos can be used as an alternative source of P, especially for smallholder farmers.