Browsing by Author "Kahimba, Frederick Cassian"

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Combining biochar with low rate of chemical fertiliser boosts maize biomass yield, regardless of tillage system, under humid conditions
(jarts, 2019) Kiobia, Denis Olgen; Graef, Hannah A; Reuben, Paul; Kahimba, Frederick Cassian; Graef, Frieder; Eichler-Löbermann, Bettina; Silayo, Valerian C.K.
Biochar application to soils increases biomass and crop yields, especially with rates higher than 100 t ha −1 . Yet, there is limited knowledge on the combined effect of biochar and chemical fertiliser under different tillage systems. The objective of this study is to investigate the effect of maize-cob biochar (BC) (rates of 5 and 10 t ha −1 ) combined with chemical fertiliser micro-dosing (MD) at a rate of 25 % of the recommended quantity on total shoot dry matter (DM) and plant height of maize cultivated under flat (F) and tied-ridge (R) practices during a humid season in Tanzania. The results indicate that combining 5 t ha −1 BC with 25 % MD increases DM at harvest by 83 % (4.16 t ha −1 ) compared to the control (2.27 t ha −1 ) and was in the same range as the DM obtained from the treatment with the recommended fertiliser rate (100 % FD). The treatments with single applications of 25 % MD, 5 t ha −1 BC, and 10 t ha −1 BC only tended to exceed the control of DM yield. Therefore, we recommend that small-scale farmers aiming at DM for livestock or grain yield with limited access to chemical fertilisers to combine biochar with 25 % MD, rather than applying biochar or low chemical fertiliser rates alone.
Root-zone soil moisture redistribution in cropping systems under freeze-thaw conditions
(University of Manitoba, 2008) Kahimba, Frederick Cassian
The availability and distribution of soil moisture within the root zone is a key factor in ensuring better crop growth performance and attaining improved yield. The soil moisture is influenced by farm management practices such as cover cropping that affect the freeze-thaw processes during the fall. This in turn may influence accumulation and redistribution of soil moisture during the winter, and thereafter, the soil’s response to thawing during spring, and availability of soil moisture for the subsequent season. The impact of cover cropping systems on soil temperature, infiltration, and soil moisture redistribution due to soil freezing and thawing was investigated. In addition, the effect of cover crop on the within-season and subsequent-season crop performance and yield was also investigated. Time Domain Reflectometry (TDR) and Neutron Scattering (NS) methods were used to measure the unfrozen and total water contents, respectively. Soil temperature was measured using thermocouples embedded in the soil profile. Soil moisture and soil temperature data were collected from August 2005 to September 2007. Laboratory calibration of the TDR miniprobes indicated the maximum cable length for the RG-58 50 Q coaxial cable to be 40.0 m when 35 mm TDR miniprobes were used. Since the TDR was found to overestimate the liquid water content at soil temperatures below 25°C, a method to correct the field measured TDR soil moisture for temperature effects was developed. During soil freeze-up, water from unfrozen soil layers below the freeze front migrated towards frozen layers above. Compared to non-cover crop treatment, the cover crop treatment did not freeze earlier during the fall, froze to a shallower depth during the i