Effect of agronomic practices using organic amendments on selected chemical properties of soils in Chipata and Kasama, Zambia
In Zambia, most crops are mainly produced by small scale resource poor farmers who rely on soils with inherently low fertility. When soil productivity declines farmers put affected fields on fallow to allow the fertility to regenerate, and open up new fields. This type of farming is not sustainable due to the increasing human population. To improve the regeneration of soil fertility a number of organic amendments have been introduced. There is however limited information on the effect agronomic practices that use organic amendments on chemical properties of soils in Zambia. A study was conducted to assess the effect of some organic amendments on selected chemical properties of two Ultisols in Kasama and soil productivity of Zambia. Field crop trials laid out in a Completely Randomized Design (CRD) were set up in the 2015/16 to 2016/17 agricultural seasons with maize as the test crop at the two sites. Treatments used in Kasama were pigeon pea, tephrosia vogelii alley cropping, traditional fundikila, modified fundikila, and chemical fertilizers. In Chipata, pigeon pea, tephrosia vogelii alley cropping, sun hemp, cattle manure, and chemical fertilizer were used. At the end of each season, soil samples were collected from research plots and tested for soil organic matter (SOM), CEC, pH, exchangeable acidity, total N, available P and exchangeable K. Maize grain yields were also recorded. After two growing seasons, no significant differences (p > 0.05) in SOM were observed among treatments in Chipata. In Kasama SOM significantly (p < 0.05) increased from 2.28 to 2.96 % on plots under modified fundikila, but not on plots with other treatments. No significant differences in CEC were observed among treatments at both sites. Significant (p < 0.05) increases in total N levels were observed treatments with organic amendments in Chipata, while in Kasama significant (p<0.05) increases were only it treatments with pigeon pea and traditional fundikila. A significant (p< 0.05) increase in soil pH was observed in treatments with organic amendments in Chipata, but not in Kasama. No significant changes (p > 0.05) in exchangeable acidity, available P and exchangeable K were observed among treatments at both study sites. Maize grain yield was found to be significantly and positively correlated with exchangeable K, (p < 0.01, r = 0.81), and soil pH (p < 0.05, r = 0.61), and significantly negatively correlated with exchangeable acidity (p < 0.05, r = -0.55) and total N (p < 0.01, r = - 0.74) in Kasama. No significant correlation was observed between selected soil chemical properties and maize grain yield in Chipata. The use of organic amendments did not significantly change the CEC, exchangeable acidity, available P and exchangeable K of soils after two growing seasons at both sites. It however significantly increased levels of total N in the soils at both sites and increased the pH at one site. The effects of applying organic amendments on soil chemical properties generally varied with site indicating that the potential success of agronomic practices that use organic amendments to improve soil fertility depends on the soil and other ecological conditions. Key words: Modified fundikila, traditional fundikila, alley cropping, cow manure, sunn hemp
Soil fertility -- Chipata district -- Zambia, Soil fertility -- Kasama district -- Zambia, Soil fertility
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