Effects of some amendments on soil properties and maize yield grown in sodic soil: a case study of Mto wa Mbu, Arusha, Tanzania
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Date
2003
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Publisher
Sokoine University of Agriculture
Abstract
A study was conducted at Mto wa Mbu, Arusha, Tanzania to evaluate the effects of some amendments on soil properties and yield of maize grown in sodic soils. The soil of Mto wa Mbu was classified as sodic with a clay loam texture. The soil was characterized in this study for its physical and chemical properties prior to planting maize as a test crop. The soil laboratory analytical data showed that the soil was alkaline, clay loam textured and compact (bulk density ranging from 1.39 to 1.45 gem'3). The soil pH ranged from 9.80 to10.45, ECe from 1.6 to 3.57 dSm'1 and ESP ranged from 92 to 99%. Total N, available P, % OC, exchangeable Ca, Mg, CEC, and DTPA extractable Cu, Zn, Fe and Mn were in the low range while exchangeable K and Na were high. In the field a randomized complete block design was used to evaluate the effects of the amendments using maize as a test crop. Gypsum was applied at 0, 7.5, 15, 22.5 and 30 tha’1 and sulphur at 0, 1.4, 2.9, 4.3 and 5.7
tha'1, corresponding to 0, 25, 50, 75, and 100% of laboratory gypsum requirement. The amendments were surface mixed at 0-15 cm depth. The rates of farmyard manure were 0 and 20 tha’1. Prior to soil incorporation, the amendments (FYM and gypsum) were analyzed for their chemical properties. In gypsum treated plots maize grain yields ranged from 0 (control) to 1.32 tha’1. The maize grain yields in sulphur amended plots ranged from 0 to 0.32 tha’1 and that of FYM treated plots ranged from 0 to 0.35 tha’1. When gypsum and sulphur were combined with FYM the maize grain yields ranged from 0 to 1.42 and 0 to 0.53 tha’1 respectively. Therefore, maize grain yield was significantly higher in gypsum and FYM when applied alone than in sulphur amended plots. But it was much higher when gypsum and sulphur were mixed with FYM. Application of sulphur caused only slight yield increases, but was more effective when combined with FYM. The economic analysis showed that the application of amendments was uneconomical due to low maize grain yield. At the end of growing season the soil was analyzed to evaluate the residual effect of the amendments on soil properties. Available P, ECe, % OC, total N exchangeable bases, CEC in the plots amended with gypsum, sulphur and FYM increased in the top 15 cm of soil relative to the control. Soil pH and ESP in all treated plots was significantly reduced except in S25 and S50 treatments. Bulk density in all amended plots was not significantly different to the control. DTPA extractable Zn, Fe, Cu and Mn increased slightly following the application of amendments. Regression analysis between soil variables and maize grain yield showed that soil pH and Ca were significantly affected the yield (P<0.05). ECe was slightly correlated with the yield. The rest of the variables (P, % OC, Total N, excahngeable bases and DTPA extractable Zn, Fe, Cu, Mn) were notlinearly correlated with the yield. Though maize grain yields from the treated plots were low compared to that of normal soils which range from 1.2 to 2.4 tha'1, the results from the field suggested that, the amendments especially G100 + FYM can ameliorate sodicity and
produce satisfactory plant growth and yields.
Description
Dissertation
Keywords
Soil properties, Maize yield grown, Sodic soil, Mto wa mbu, Arusha