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

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-B and BGS were 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-1 soil. The experiment was arranged in 3×5 factorial experiment 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 slow decrease up to the 112th day of incubation. P release (availability) from the studied guano 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 at 80 mg kg-1 soil.  The soil pH showed very strong negative correlation (r > 0.8) with P released in the soil throughout incubation period. It was concluded that P release from the three bat guano deposits in soils is gradual and reaches the pick in almost three months after application. Thus, it should be applied at least two months before planting for more effectiveness of P release

Factoring labour when comparing in situ rainwater harvesting technologies for semi-arid areas of central Tanzania

Published online: 08 Feb 2023Erratic rainfall, high evapotranspiration rates and droughts are major factors limiting crop production in semi-arid areas. Tied ridges that have crossed ties within the furrow are among the physical soil and water conservation measures. During the 2018/19 and 2019/20 seasons, we examined the efficacy of repaired tied ridges for maize crop (Zea mays) and sorghum (Sorghum bicolor) in Kongwa district of Tanzania as an alternate labour saving strategy for managing climate risks associated with variable rainfall. Treatments consisted of three tillage methods: conventional tillage (CT) which involved the preparation of a flat seedbed using handhoe, annually constructed tied ridges (ATR) and tied ridges that had been constructed during the previous season and had been repaired (residual tied ridges–RTR). Data were collected on labour requirements and crop performance. RTR increased economic returns by 29% and 80% over ATR and CT, respectively. Maize grain yield shows a trend of RTR >ATR>CT with values ranging from 2465 kg ha−1 to 4185 kg ha−1 (P 0.05). The use of RTR is recommended because of low labour requirements and greater economic benefits than CT and ATR under maize cropping systems

Maize response to leguminous biomass composted with phosphate rocks in the northern zone of Tanzania

A study was conducted to evaluate maize response to leguminous biomass composted with phosphate rocks (PRs) in a split plot design. Field experiments were conducted at Wang’waray Farmers Training Center (F.T.C) located in Babati District of Manyara region in the Northern zone of Tanzania between December 2013 and June 2015. Three leguminous (Crotalaria juncea, Lablab purpureus and Mucuna pruriens) strips were cultivated in 2013/14 to produce a biomass which was harvested at flowering to early podding stage and air dried. Air-dry biomass was composted with PRs from Minjingu (medium reactive PR) and Panda Hill (low reactive PR). Maize response to different treatments was evaluated across the field strips in 2014/15 season. The strips previously used to produce leguminous biomass were used as main plots and each strip was divided into seven subplots receiving different treatments at random. A medium term maize variety SC. 627 was used as a test crop. Average maize grain yields obtained from Crotalaria, Lablab and Mucuna strips reached 5.3, 4.5 and 4.0 t ha-1, respectively and were statistically different (P=.05). Application of Minjingu or Panda Hill PR alone didn’t increase maize grain yield above the control while Minjingu PR applied with urea or composted with biomass increased maize grain yield by 2.40 and 1.58 t ha-1, respectively above the control. Application of Panda Hill PR with urea or composted with biomass increased grain yield by 1.20 and 1.06 t ha-1, respectively above the control. The observed differences (0.82 and 0.14 t ha-1) were not statistically significant indicating that biomass composted with PR was as effective as the PR applied with urea