Effects of Different Phosphorus Fertilizers on Rice (Oryza sativa L.) Yield Components and Grain Yields

A study to investigate the effects of phosphorus (P) from Minjingu Phosphate Rock (MPR), Minjingu mazao and Triple Super Phosphate (TSP) fertilizers under irrigated rice (Oryza sativa L.) production was conducted in two sites of Lekitatu village, Meru district, Arusha region, Tanzania. The fertility status of the soils and their suitability for rice production at two experimental sites were evaluated based on technical indicators of soil fertility. The major soil fertility limitations included low soil organic matter, low total nitrogen and medium available phosphorus hence the rice soils in Lekitatu village were categorized as of low fertility status and moderately suitable for rice production. A Randomized Complete Block Design (RCBD) with three replications was adopted. Phosphorus was applied at the rates of 0, 20, 40 and 60 kg P ha-1 as MPR, Minjingu mazao and TSP. Nitrogen was applied uniformly at a rate of 60 kg N ha-1 as urea to the MPR, Minjingu mazao and TSP treatments plots taking into account the 10% N contained in the Minjingu mazao fertilizer. The P fertilizers were broadcasted and incorporated into the soils before transplanting the rice seedlings and N was applied at two equal splits, namely at tillering and panicle initiation stages. The ranges in yield components between the control (0 kg P ha-1) and the highest levels of P (60 kg P ha-1) were 23.47 – 64.97, 23.47 – 66.17 and 23.47 – 60.03 cm plant heights, 12–22, 12–19 and 12–22 number of tillers per plant, 7.67–25.97, 7.67–26.83 and 7.67–30.20 tha-1 dry matter yields, 3.97 – 15.70, 3.97 – 17.03 and 3.97 – 15.77 tha-1 straw dry matter yields and 1.5–8.63, 1.5–9.23 and 1.5–10.43 tha-1 grain yields for MPR, TSP and Minjingu mazao, respectively. The P fertilizers applications increased rice yield components as the levels of P increased from 0 to 60 kg P ha-1 for all P sources. The yield components increased significantly (P<0.05) with increasing rates of P application. The increases were due to increased availability and uptake of plant nutrients particularly P. Based on the generated yields data, it was thus concluded that: Minjingu mazao at the rates of (40 to 60 kg P ha-1), MPR and TSP at a rate of 60 kg P ha-1, respectively could be adopted for increased and sustainable rice production in Lekitatu village.