Abstract:
This study was carried out to assess the suitability and effectiveness of gypsite as soil amendment in release of Ca and S. This is because besides the high potential of gypsite in improving crop yields in some countries, its use in Tanzanian agricultural soils is limited. This is attributed largely to few researches on their agricultural potentials. The gypsite samples used in this study were collected from Pindiro, Makanya, Itigi and Msagali sites. The X-ray fluorescence (XRF) method was employed to analyze the chemical compositions of the composite samples. Using maize as a test crop, pot experiment was conducted to assess crop response to gypsite application at different rates. In addition, incubation study was conducted for 56 days on the solubility of gypsite in release of S in soil solution. The XRF results showed that the gypsites from the four sites varied in amounts of gypsum content from 35.76 to 82.36% for gypsite from Itigi and Pindiro respectively. The contents of S were 15.32, 13.26, 10.52 and 6.65 % for Pindiro, Msagali, Makanya and Itigi gypsites respectively. Calcium contents was 11, 9.5, 7.6 and 4.8% for Pindiro, Msagali, Makanya and Itigi gypsites, respectively. Pindiro and Msagali gypsite sources were selected for pot experiment due to having high S and Ca percentage. Results from pot experiment indicated that maize plant height and shoot dry matter were significantly higher by 22% and 27.2%, respectively for soil amended with Pindiro and Msagali gypsites compared to maize grown in none amended soil. After pot experiment, the postharvest soil analysis indicated that on the average residual S increased by 5 for soil amended with Pindiro and 2 times for soil amended with
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Msagali gypsite while Ca increased by 19.6 and 21.7% for soil amended with Pindiro and Msagali gypsites, respectively, compared to control. In addition, incubation results revealed that solubility of gypsites for Pindiro and Msagali were high (178 to 579 and 165.1 to 492.2 mg S kg-1) respectively. Gypsites from Pindiro and Msagali are effective in improving Ca and S availability for plant growth, also gypsite application has acidifying effect to the soils. In this study gypsite application reduced the pH by 0.4 units. However, field trials using different soil types and various crops are recommended in order to make concrete recommendations on use of these soil amendments.
