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The objective of this study was to screen the potential of four plant growth promoting rhizobacteria (PGPR) for growth promotion in sorghum (Sorghum bicolor) and suppression of Striga hermonthica development. Bacillus subtilis Bsn5, B. subtilis GBO3, B. amyloliquefaciens FZB42 and Burkholderia phytofirmans PsJN were evaluated under controlled conditions in growth chambers. After 28 days of growth, the effect of selected PGPR on sorghum plant height, leaf chlorophyll (SPAD) value, biomass dry matter (DM), number of germinated and attached Striga plants and number of Striga plants that developed tubercles was analyzed. Inoculated Striga-free sorghum plants were significantly taller, with higher leaf chlorophyll SPAD values and higher dry matter than uninoculated Striga-free plants. However, there were no differences in sorghum height, SPAD value and DM between inoculated and uninoculated Striga-infected sorghum plants. In the absence of PGPR inoculation, differences in DM were observed between Striga-free and Strigainfected sorghum. Compared to the untreated control, Striga seed germination was lower in the sorghum plants treated with B. subtilis GBO3 and B. amyloliquefaciens FZB42. Of the germinated Striga seeds, the percentage that attached to the sorghum plant was lowest (23%) in the B. subtilis GBO3 treatment. The percentage of dead Striga tubercles in the PGPR treatments ranged between 35 and 59%, compared to 3% in the untreated control. This study identified B. subtilis GBO3, B. amyloliquefaciens FZB42 and Burkholderia phytofirmans PsJN with promising potential to promote sorghum growth and suppress Striga.

We evaluated the effect of NaCl-induced salinity and successive urine fertilization on changes in cultivation substrate chemical properties in a greenhouse study. The substrate was composed of an equal volume ratio mixture of bio-waste compost, quartz sand and silty loam soil. Salinity was imitated by adding NaCl solutions to a known substrate weight achieving three target salinity treatments of EC e 1.3 (S0-no NaCl), 4.6 (S1) and 7.6 (S2) dS•m −1. Cultivation substrate had been cropped with two cycles of maize (Zea mays L.) (crop cycles I and II) and fertilized with human urine at N amounts of 0 (U0-no urine), 180 (U1) and 360 (U2) mg•kg −1 substrate in the first cycle and half of the urine-N dosages in cycle II. Substrate samples collected at the end of each cycle were analyzed for pH KCl , EC e , exchangeable and water extractable cations (Na + , K + , Ca 2+ , Mg 2+), cation exchange capacity, water extractable anions (Cl − , 3 NO − , 2 4 SO − , 4 PO 3−) and exchangeable sodium percentage (ESP). Exchangeable Na + , K + and Ca 2+ were significantly (p < 0.05) affected by salinity x urine interaction. EC e significantly increased by 7.3, 5.3 and 7.6 dS•m −1 in the S0, S1 and S2 treatments following an increase in urine from U0 to U2. In the S0 treatment, ESP increased in the order U0 < U1 < U2. Extractable 3 NO − and Cl − were significantly affected by crop cycle, salinity and urine interactions (p < 0.05) whereas the effect of urine fertilizer on extractable 2 4 SO − and 4 PO 3− depended on crop cycle alone. There was a tendency towards increasing soil sodicity with mounting urine fertilization. The level of NaCl salinity and the amount of urine applied are important determinants of substrate chemical properties. Adoption of appropriate management techniques to avoid salinity/sodicity build up should be included in urine fertilization planning.