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Purpose This research work described the effect of organic waste (poultry manure) on soil cumulative infiltration rate (CIR), soil organic matter (SOM), and maize performance on two contrasting alfisols of southwestern Nigeria. Methods Six treatments of poultry manure were applied in split at 0 Mg/ha, 2 Mg/ha, 4 Mg/ha, 6 Mg/ha, 8 Mg/ha, and 10 Mg/ha, in replicate under a completely randomized design to clay loam (CL) and sandy clay loam (SCL) soils, at 3, 6, 9, and 12 weeks after the initial application. Results The results showed significant increases (P < 0.05) in CIR, SOM, and maize performance compared to the control in both soils. Poultry manure at 10 Mg/ha recorded the highest SOM which was significantly (P < 0.05) different from other application rates in both soils. The mean values for SOM in SCL were between 0.67 and 3.75% for 0 Mg/ha and 10 Mg/ha, while the mean values recorded for CL were between 0.80 and 4.35% at 0 Mg/ha and 10 Mg/ha. Poultry manure reduced CIR in the SCL, but improved CIR with increasing rates on CL. Poultry manure at 4-10 Mg/ha increased the maize shoot biomass significantly (P < 0.05). However, the application rate of 6 Mg/ha manure recorded the highest fresh shoot biomass, while 8 Mg/ha increased dry shoot biomass in both soils. Conclusion This study indicated that poultry manure applied at 10 Mg/ha gave the best results in improving CIR, SOM, and maize performance on different soil types.

Purpose Biochar and inorganic fertilizer when co-applied have been reported to increase crop yield and enhance soil fertility. However, studies on this complementary effect on soil properties and rain-fed upland rice performance in Sub-Saharan Africa are still scanty. Methods Field factorial studies conducted over 2 years was set up to investigate the interactions between rice husk biochar and inorganic nitrogen (N) fertilizer on a sandy clay loam Alfisol. A two-factor (4 × 4) in RCBD where rice husk biochar was incorporated at four doses, 0, 3, 6, and 12 t/ha −1 , inorganic N fertilizer (urea) at four rates, 0, 30, 60 and 90 N kg/ha −1 , and their combinations was adopted. Results Results showed that combination of biochar and N fertilizer exerted significant (P > 0.05) interactive effect on rice harvest index, grain and straw yield and N-use efficiency. Interaction between biochar and N fertilizer increased agronomic efficiency by 140% and grain nutrient recovery by 191% over 2 years. Combination of biochar and N fertilizer reduced soil bulk density, increased water holding capacity and soil chemical status such as pH, N, P, K, Corg, Ca, ECEC and base saturation, all within the top 10 cm depth of the soil. Conclusions Overall, the results established that rice husk biochar can be used as a soil conditioner to enhance upland rice yield on an Alfisol. The combined dose of 3-6 t/ha −1 biochar and 30 kg/ha −1 of N fertilizer is thus recommended for upland rice farmers in the study area.

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Field studies were conducted over 2 years to determine the response of soil microbial biomass pool to biochar and N fertilizer combinations in a rain-fed rice cropping system. Biochar was applied at four doses: 0 t ha −1 , 3 t ha −1 , 6 t ha −1 and 12 t ha −1 in combination with N fertilizer at four rates: 0 kg ha −1 , 30 kg ha −1 , 60 kg ha −1 and 90 kg ha −1 to a Typic Paleustalf Alfisol. Soil samples from two depths (0-10 and 10-20 cm) were collected to determine microbial biomass C (MBC), N (MBN), P (MBP), MBC/N ratio, MBC/P ratio, soil CO 2 flux, microbial qCO2, cultivable bacterial and fungal abundance. Biochar and N fertilizer combination effects on MBC, MBN and MBP pools were dependent on biochar doses, N fertilizer rates and soil depth. MBC/N and MBC/P ratios were decreased after 2 years. Soil CO 2 flux was maximum at post-seeding stage of rice plant, while decreasing trends occurred at active tillering and harvest stage. Increasing doses of biochar irrespective of its combination with N fertilizer rates decreased CO 2 flux and microbial qCO2. Combinations of biochar and N fertilizer increased fungal/bacterial ratio and induced a shift to a more fungal-dominated population after 2 years. Our results suggest that combination of biochar doses (3-12 t ha −1 ) with N fertilizer rates had stimulatory effects on microbial biomass pools and activity with positive implications for organic carbon accumulation, nitrogen (N) and phosphorus (P) retention in tropical soils.