Effectiveness of Poly-Hallite (Poly 4) Fertilizer Material in Maize and Tomatoes Production in Selected Agro-Ecological Zones of Tanzania.

Polyhalite (K2SO4.MgSO4.2CaSO4.2H2O) is a new fertilizer in Tanzania and needs to be assessed for its effectiveness before being allowed for use by farmers. Six and three field experiments were conducted to assess the effectiveness of Polyhalite fertilizer using maize (Var. Situka) and tomato (Var. Chanya), respectively. The experiments were laid as completely randomized block design in eastern Tanzania. The exchangeable K contents in soils varied from 0.29 to 0.58meq 100g^-1 which were not sufficient for growth of both crops. The treatments tested at different rates for maize and tomato were Control, DAP, DAP + Poly 4 (a), DAP + Poly 4 (b), DAP  + Poly 4 (c), DAP + MoP (a), DAP + MoP (b), and DAP + MoP (c). While there was no effect for fertilizer application for plant diameter and number of fruits in two sites, there was a significant effect (P≤ 0.05) for fertilizer application for plant diameter and number of fruits of tomato in one site. The weight of tomato fruits was higher by application of Poly 4 but statistically (P≤ 0.05) similar to that of Muriate of Potash in one site and vice versa in another site. In the remaining site, weight of tomato fruits was statistically (P≤ 0.05) higher by application of Muriate of Potash than that of Poly 4. With regards to maize, while plant height and stem diameter were significantly increased by application of all fertilizers, plant biomass and maize grain yields were significantly (P≤ 0.05) increased by application of Poly 4. It is thus concluded that Poly 4 fertilizer is as effective as Muriate of Potash and in most cases it is more superior in improving yield components and increasing yields of both maize and tomato