Mapunda, Hugo Gido2026-07-282026-07-282011https://www.suaire.sua.ac.tz/handle/20.500.14820/7861DissertationThe assessment of residual effect of long term use of NPK plus B formulation on tobacco yield and quality involved soil sampling from four districts; Urambo, Uyui, Tabora and Sikongc. There were two experiments each one with six treatments: pot experiment at ARI Tumbi had three replications while Held experiment al Ntalikwa village had four replications. Data collected were; leaf length, green and dry weights grade index and nutrients concentration in plant leaves. The results showed that; total nitrogen was very' low (0.03 to 0.18%). Phosphorus was low to medium (5.62 to 60.83 mg/kg soil). Exchangeable potassium was. low to very' high (0.06 to 0.81), exchangeable calcium was very' low to high (0.01 to 4.4). The cation exchange capacity (CEC) of the soils was low; 6.4 to medium 23.33 me/100 g soil. Tobacco grown in Isenga soils (sandy soils) and Kikungu soils (Alfisols) had good performance in T2 (40.5 mg N kg’1 ) while Tobacco grown in Mbuga soils (Vertisols) had good performance in T3 (recommended rate 300 mg N kg’1, 238 mg P kg’1, 598 mg K kg’1 and 3 mg B kg’1 soil). The increase in rates of NPK+B and CAN, Mg, Zn caused death of tobacco in treatments 4, 5 and 6 possibly due to B toxicity. In the field experiment the current formulation, T3 (NPK + B (10:18:24 +0.1 and 5 g CAN) produced below treatment 4, 5, and 6. Dry' weight yield and quality' increased in treatments with higher rates of NPK+ B formulation with Zn and Mg than the current recommendation. The highest yield was from T6 (2488.12 kg ha’1). Residual nutrients T1 yielded 1411.89 kg ha’1 of dry leaf of tobacco. In general, low residual nutrients in Tabora soils need new formulations which include Mg and Zn to improve yield and quality of tobacco.enSoil samplingResidual effectNPK plus B formulationTobacco yieldThesis