Assessment of soil fertility status of selected paddy growing areas of Tanzania
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Date
1997
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Sokoine University of Agriculture
Abstract
Nitrogen, phosphorus, zinc and iron deficiency or limited availability are the main soil fertility constraints limiting rice yield worldwide. The objective of this study was diagnostic to develop criteria for assessing the fertility status of the selected rice growing areas of Tanzania in terms of the availability of the above nutrients. Soil samples were collected from 10 different areas where rice is grown for both laboratory analyses and a glasshouse experiment. The laboratory analyses included the screening of suitable indices for available N, P, Zn and Fe total N, P, Zn Nitrogen availability was assessed by in soils. OC and the alkaline-KMnO4 indices, P by Bray-1, Olsen and the filter paper strip methods while available Zn and Fe were assessed by 0 . IN HC1, 0.005M DTPA at pH 7.3 and 0.01M EDTA-(NH4) 2CO3 at pH 8.6. (Oryza sativa L). The response of rice variety Super India to these nutrients was assessed in a glasshouse experiment where plants were grown for 51 days. The results showed that all the soils used in this study were deficient in N and hence required fertilization with N while 60% of the soils responded to P application. All the soils had adequate levels of K and Zn although three of the soils appeared to be borderline cases between adequate and deficient. The extractable Fe content was very high in all soils. Of the nutrient availability indices tested, OC correlated significantly with the DM yield while Olsen extractable P was found suitable for P assessment with a critical level of 20 mg/kg soil. None of the indices tested was found for suitable Zn and Fe assessment. Basing on these results, OC and Olsen methods were recommended for use in assessing N and P availability in the soils, respectively. No reliable extractant for micronutrients Zn and Fe was obtained in this study. Field experiments are recommended to confirm these findings.
Description
Dissertation
Keywords
Soil fertility, Paddy growing, Rice growing, Nitrogen, Phosphorus, Zinc, Iron