Among agricultural soil amendment that can enhance crop productivity and soil sustainability is biochar. Hence, two-year field experiments were conducted on a sandy loam Alfisol at Owo, southwest Nigeria, to evaluate the effects of biochar produced from hardwood on soil physical and chemical characteristics, erosion potential, and cocoyam (Xanthosoma sagittifolium (L.) Schott) yield. The study was a 2 × 4 factorial experiment with two years (2017 and 2018) and four biochar levels (0 (control), 10, 20, and 30 t ha−1). The treatments were laid out in a randomized complete block design with three replications. Results indicated that biochar application significantly in both years improved yield of cocoyam and soil physical (bulk density, porosity, moisture content, mean weight diameter (MWD) of soil aggregates, dispersion ratio, and infiltration rate) and chemical (soil organic matter, pH, N, P, K, Ca, Mg, and CEC) properties and erosion resistance. Soil characteristics and cocoyam yield improved with level of biochar from 0–30 t ha−1. When 2018 is compared with 2017 in term of soil loss, in the amended plots, 2018 reduced soil loss by 7.4, 20, and 73.5%, respectively, for 10, 20, and 30 t ha−1biochar, whereas there was an increase of 2.7% soil loss in the control plot in 2018 compared with 2017. Therefore, application rate of 30 t ha−1 biochar is considered as suitable for severely degraded soil because this application rate efficiently improves cocoyam yield and soil properties and reduces soil loss.

Use of organic manures to meet the nutrient requirement of crop would be an inevitable practice in the years to come for sustainable agriculture since organic manures generally improve the soil physical, chemical and biological properties. Hence, field experiments were carried out in 2017 and 2018 to compare the impact of different organic manures and NPK fertilizer on soil properties, growth, yield, proximate and mineral contents of okra (Abelmoschus esculentus L.). The treatments each year 2017 and 2018 consisted of: rabbit manure, cow dung, poultry manure, green manure [Mexican sunflower (Tithonia diversifolia Asteraceae)], pig manure, NPK 15-15-15 fertilizer applied at 120 kg N ha−1 and a control (no manure/inorganic fertilizer). The seven treatments were laid out in a randomized complete block design with three replication. Organic manures and NPK fertilizer increased the soil organic matter (OM), N, P, K, Ca and Mg (NPK fertilizer did not increase OM, Ca and Mg significantly), growth, yield, minerals, protein, ash, carbohydrate and mucilage contents of okra fruit as compared with control. Organic manures improved okra yield compared with NPK fertilizer. Okra growth and yield parameters were significantly higher in 2018 compared with 2017. Control, rabbit manure, cow dung, poultry manure, green manure, pig manure and NPK fertilizer in 2018 increased the pod yield of okra by 9.7%, 35.3%, 57.9%, 36.2%, 39.2%, 45.5% and 3.2%, respectively compare with the same treatment in 2017. Amongst various organic manures, poultry manure produced significantly higher plant growth, yield, mineral and proximate composition of okra because of its high soil chemical properties which could be related to its lowest C: N ratio, lignin and lignin: N ratio. Results also showed that okra grown during high intensity rainfall has higher yield but with reduced quality except its mucilage content. Therefore, planting of okra with poultry manure under moderate rainfall will enhance the health benefit from the fruit, however, those that desire its mucilage content planting during high rainfall is recommended.

AbstractBiochar has a low chemical composition and is recalcitrant to degradation. For good soil fertility and nutrient use efficiency of crops it becomes imperative that addition of a fast releasing nutrient source to biochar be sought. Therefore, studies were conducted in 2017 and 2018 to evaluate the effects of biochar with poultry manure (PM) and NPK fertilizer on soil properties, growth and yield of ginger. Treatments evaluated were: biochar applied alone at 15 t ha-1 , PM applied alone at 15 t ha-1, NPK fertilizer applied alone at 200 kg ha-1, biochar applied at 15 t ha-1 with poultry manure applied at 15 t ha-1 (B+PM), biochar applied at 15 t ha-1 with NPK fertilizer applied at 200 kg ha-1 (B+NPK) and a control with no amendment whatsoever. The experimental design was a randomized complete block design with three replications. Biochar, PM, NPK fertilizer alone or B+PM and B+NPK improved soil physical and chemical properties, growth and yield of ginger compared to no amendment (control). NPK fertilizer did not improve soil physical properties nor increased pH, OM, Ca and Mg significantly. B+PM and B+NPK improved soil physical and chemical properties, growth and ginger yield compared to their sole forms. Although B+PM had better soil physical properties, B+NPK increased yield and growth of ginger compared to B+PM. B+NPK increased the yield of ginger by 12.2% and 10.6% in 2017 and 2018, respectively compared with B+PM. B+NPK also increased the yield of ginger by 49.2% and 50.3% in 2017 and 2018, respectively compared to biochar alone. This was related to high presence of nutrients in B+NPK especially N and K which are important for ginger rhizome formation.

Two field experiments were conducted concurrently in 2019. The study investigated the effects of single and combined application of wood biochar (WB) and cow dung biochar (CDB) with green manure (GM) on soil properties, performance, and tuber qualities of tiger nut. The treatments consisted of: CDB at 10 t ha−1, WB at 10 t ha−1, GM—Tithonia diversifolia at 10 t ha−1, CDB + GM, WB + GM, control. The six treatments were arranged in RCBD with three replications. CDB, WB, and GM either sole or combined increased moisture content, SOC, nutrient contents, culturable microorganisms, performance, moisture, ash, fiber, and protein contents of the tiger nut compared with the control. CDB has a higher N, C: N ratio, P, K, Ca, Mg, CEC, and pH relative to. CDB alone and CDB + GM increased growth and yield compared with WB alone and WB + GM. CDB + GM has the highest value of growth and yield of tiger nut. GM alone improved growth and yield of tiger nut compared with the two sole biochar treatments. CDB + GM and WB + GM increased growth and yield of tiger nut compared with their sole forms. This was adduced to biochar allowing the retention of nutrients from rapidly decomposing Tithonia within the rooting zone, thereby promoting better effectiveness of nutrient uptake and increase in yield. Therefore, for good soil fertility and tiger nut yield, it is important that the addition of a fast releasing nutrient source to biochar be sought.

For soil fertility maintenance, secondary nutrient such as Magnesium (Mg) is always being neglected. However, its role is critical in the growth, yield, and quality of crops. Therefore, two field experiments were initiated in 2017 and 2018 to evaluate the response of soil chemical properties, performance, and qualities of turmeric (Curcuma longa L.) to Mg fertilizer alone and in combination with poultry manure (PM) and NPK 15-15-15 fertilizer (NPK). The treatments applied were the following: (i) PM alone at 8 t ha−1, (ii) NPK alone at 200 kg ha−1, (iii) Mg fertilizer alone (in form of MgO) at 20 kg ha−1, (iv) PM at 8 t ha−1 with MgO at 20 kg ha−1 (PM + Mg), (v) NPK at 200 kg ha−1 with MgO at 20kgha−1 (NPK + Mg), and (vi) control (no amendment of any kind). PM, NPK, and Mg fertilizers alone or NPK + Mg and PM + Mg increased soil chemical properties, performance (plant height, number of leaves, number of tillers, number of rhizomes, and fresh rhizome weight), and minerals and vitamins C and A contents of turmeric rhizome compared with the control. By averaging 2017 and 2018, Mg fertilizer alone increased the yield of turmeric by 10.8% compared with the control. For this experiment, NPK + Mg increased growth and yield of turmeric compared with other treatments. Also, averaging 2017 and 2018, NPK + Mg increased rhizome yield of turmeric by 13.6% and 10.6% compared with PM + Mg and NPK alone, respectively. Similarly, PM + Mg significantly improved mineral and vitamins contents compared with other treatments. Therefore, for those that desire turmeric rhizome for its nutritive value, PM + Mg is recommended. For those that want quantity, NPK + Mg is recommended.

28Use of organic manures to meet the nutrient requirement of crop would be an inevitable practice 29 in the years to come for sustainable agriculture since organic manures generally improve the soil 30 physical, chemical and biological properties. Hence, field experiments were carried out in 2017 31 and 2018 to compare the impact of different organic manures and NPK fertilizer on soil properties, 32 growth, yield, proximate and mineral contents of okra (Abelmoschus esculentus L.). The 33 treatments each year 2017 and 2018 consisted of: rabbit manure, cow dung, poultry manure, green 34 manure [Mexican sunflower (Tithonia diversifolia Asteraceae)], pig manure, NPK 15-15-15 35 fertilizer applied at 120 kg N ha -1 and a control (no manure/ inorganic fertilizer). The seven 36 treatments were laid out in a randomized complete block design with three replication. Organic 37 manures and NPK fertilizer increased the soil organic matter (OM), N, P, K, Ca and Mg (NPK 38 fertilizer did not increase OM, Ca and Mg significantly), growth, yield, minerals, protein, ash, 39 carbohydrate and mucilage contents of okra fruit as compared with control. Organic manures 40 improved okra yield compared with NPK fertilizer. Okra growth and yield parameters were 41 significantly higher in 2018 compared with 2017. Control, rabbit manure, cow dung, poultry 42 manure, green manure, pig manure and NPK fertilizer in 2018 increased the pod yield of okra by 43 9.7%, 35.3%, 57.9%, 36.2%, 39.2%, 45.5% and 3.2%, respectively compare with the same 44 treatment in 2017. Amongst various organic manures, poultry manure produced significantly 45 higher plant growth, yield, mineral and proximate composition of okra because of its high soil 46chemical properties which could be related to its lowest C: N ratio, lignin and lignin: N ratio. 47Results also showed that okra grown during high intensity rainfall has higher yield but with 48 reduced quality except its mucilage content. Therefore, planting of okra with poultry manure under 49 moderate rainfall will enhance the health benefit from the fruit, however, those that desire its 50 mucilage content planting during high rainfall is recommended. 51

Farmers have not tested their soils for nutrient status and therefore are unaware of the fertility status of their soils. Therefore, a baseline fertility survey of 50 hectares of land of a gravelly Alfisol in the Teaching and Research Farm of Landmark University, Omu-Aran, Kwara State, Nigeria was carried out with a view to identifying soil health constraints and site-specific sustainable land management practices for optimizing crop production. Standard field protocols and laboratory analytical procedures were employed for all sample parameters measured. Results show that the soil textural classes vary from sand to loamy sand, exchangeable acidity, Ca, Mg, K, and Na and the effective cation exchange capacity has the surface and subsurface soil values of 0.0–0.92 and 0.00–0.89 cmol kg−1, 1.6–7.7 and 2.0–5.8 cmol kg−1, 1.2–11.5 and 0.7–8.0 cmol kg−1, 0.09–0.33 and 0.09–0.43 cmol kg−1, 0.0–0.16 and 0.04–0.16 cmol kg−1, 7.2–12.10 and 0.9–12.5 cmol kg−1, respectively. P values lie in the ranges of 2.5–68.9 mg kg−1 and 2.0–37.7 mg kg−1 in the surface and subsurface soils, respectively, organic C values were 0.86–2.81% and 0.68–3.49%, respectively, in the surface and subsurface soils while the values of N were 0.12–0.61% in the surface and 0.11–0.56% subsurface soils. Land evaluation shows that the soils of the project site are very fragile and poor in native fertility. Compound fertilizers low in nitrogen contents but high in phosphorus and potassium are recommended for gravelly Alfisol in a derived savannah ecological zone of the Kwara State, Nigeria to avoid a nutrient imbalance that may create artificial deficiencies of otherwise adequate nutrient elements.

AbstractNutrients use efficiency of plants could be affected by the antagonistic or synergistic effects of two or more elements in the soil leading to decreased or increased yield. Field experiments were conducted in 2017 and 2018 cropping seasons at the Landmark University Teaching and Research farm, Omu-Aran, Nigeria, to determine the interaction between zinc (Zn) and phosphate (P) fertilizers on growth, yield, nutrient elements and some heavy metals composition of groundnut grown on an Alfisol. Treatments consisted of four levels of phosphorus (0, 40, 80 and 120 kg P ha-1) and three levels of zinc (0, 4 and 8 kg Zn ha-1). The experiment was laid out in a Randomized Complete Block Design (RCBD), replicated four times. The following parameters were taken: plant height, plant spread, total biomass, number of pods/plot, weight of pods/plot, number of seeds/plot, weight of seeds/plot. Laboratory analysis of some chemical constituents of groundnut seed was carried out to determine the nutrient and heavy metals composition. Results indicated that application of 8 kg Zn ha-1 and 120 kg P ha-1 had a synergistic effect on the growth parameters and antagonistic effect on the yield, yield parameters, some nutrient elements and beneficial heavy metals. Application of 8 kg Zn and 80 kg P ha-1 is therefore recommended on an Alfisol without necessarily increasing the concentration of non-beneficial heavy metals in groundnut seed.