Effects of Different Limes on Soil Properties and Yield of Irish Potatoes (Solanum tuberosum. L) in Burera District, Rwanda
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The problem of acidic soils is complex and threatens food production in many parts of Africa and Rwanda in particular. Rwanda is a small land locked country in sub-Saharan Africa and its population density is currently the highest in the region and continues to grow. Agriculture supports 82% of the population and hence it is the most important sector that needs to be explored in order to enhance food security. The major objective of this study was to evaluate the quality of agricultural and local liming materials, their effects on selected soil physical and chemical properties and yield of Irish potatoes in Burera district. This was achieved through a laboratory based quality analysis and a field experiment. The field trial followed a randomized complete block design (RCBD) with three replications and it was established in September, 2011. The treatments comprised of the four lime materials (Agricultural lime, Karongi, Musanze and Rusizi liming materials) applied at three levels (1.4, 2.8 and 4.2 t ha-1 of CaCO3 equivalent) and control. Soil properties were monitored over a period of 16 weeks (112 days) after limes application. The data collected were subjected to analysis of variance (ANOVA) and t-test. The findings showed that, agricultural and Rusizi limes had the highest CCE (86.36 % and 85.46%, respectively). In terms of fineness factor (FF), agricultural lime and Musanze lime had higher FF compared to other limes. Lime rate of 2.8 t ha-1 of Musanze and agricultural limes had similar and highest effects in increasing soil pH. At the rate of 2.8 t ha-1 they increased the soil pH by 0.65 and 0.64 units, respectively. On the other hand, at a rate of 4.2 t ha-1, Rusizi lime had a higher Lime Efficiency (LE) (102.3%) in increasing soil pH than Musanze and agricultural lime (LE of 100% respectively). Lime rate of 4.2 t ha-1 of agricultural, Rusizi and Musanze limes reduced exchangeable Al. The effectiveness of Musanze lime at the rate of 2.8 t ha-1 had the highest LE (100.8%) among all the limes making it the best in reducing exchangeable Al, while Karongi lime was the poorest. Lime rate of 4.2 t ha-1 of agricultural lime had the highest effect in increasing available phosphorus compared to other limes while Karongi lime had the lowest effects in increasing available phosphorus. Lime application rate of 1.4 and 4.2 t ha-1of agricultural lime significantly (p<0.001) reduced the ECEC. At the rate of 2.8 t ha-1, agricultural and Musanze limes increased 0.24% and 0.21% of total nitrogen, respectively. Notably, all lime rates of Karongi lime were the lowest in increasing total nitrogen. Musanze lime had higher Relative Agronomic Efficient (RAE) than other local limes. At a rate of 1.4 t ha-1, Musanze lime had 113.04% of RAE, an indication of yield increase by 13.03%. Economically, lime rates of 1.4t ha-1 of Musanze lime had the highest economical efficiency (121.81%), which makes it to be more economically efficient than other limes and rates. Therefore, this study recommends the use of Musanze lime applied at a rate of 2 to 4 t ha-1 in acidic soils of Burera district.