Combining biochar with mineral fertilizer to enhance maize productivity on Striga hermonthica infested farmlands
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Low soil fertility and high Striga (Striga hermonthica) infestation are major constraints to maize yields in eastern Uganda. Application of fertilizers is paramount to replenish lost nutrients and increasing maize yields but has not been successful at controlling Striga damage. Integrated Soil Fertility Management (ISFM) has been advanced as alternative technology. Biochar (BC) increases organic carbon reserves in soil, which is key component for ISFM on sandy soils like in eastern Uganda. Therefore, the study determined the effect of BC application with inorganic fertilizers on i) Striga infestation (count and biomass) and ii) maize yield in Striga infested farmlands. The experiments were planted on 34 different farmers’ field each as a replicate (RCBD) for seasons 2016A, 2016B and 2017A. The treatments were: i) no input (control), ii) NK (P omission), iii) NPK, iv) NPK+1 ton BC ha-1, v) NPK+5 ton BC ha-1 and vi) NPK+IR (positive control). Data was collected on Striga infestation (count and biomass) at 10 WAP and grain yield at physiological maturity. Treatment effects were determined with ANOVA using linear mixed models in R statistical software. Mean separation was done using contrasts at 5 % level of significance. The Biochar-inorganic NPK fertilizer integration did not significantly (P > 0.05) reduce Striga infestation. Maize yield doubled following application of inorganic fertilizer. Biochar input did not significantly (P > 0.05) increase the effectiveness of NPK fertilizer on Striga infestation and maize yield, except on fields with low or negative responses to NPK fertilizer. There was successive increase in maize yield following Biochar-NPK fertilizer unlike sole NPK application even when Biochar was only applied once (one-time application) and NPK applied per season. This indicated that Biochar reduced loss of nutrients which were released in subsequent season. A one-time application of Biochar also had similar mean effect on maize yield with seasonally purchased IR maize on Striga hermonthica infested fields.