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Field experiments were conducted at Owo in the forest-savanna transition zone of southwestern Nigeria during 2007 and 2008cropping seasons to study the effect of different levels of poultry manure(0, 10, 20, 30 and 40 t/ha) on soil fertility, leaf nutrient content, growthand tuber yield of two species of yam; namely, white yam (Dioscorearotundata Poir) and yellow yam (Dioscorea cayenensis Lam). Thetreatments were factorially arranged in a randomized block design withthree replications. The soil was deficient in organic matter (OM), total N,available P, exchangeable K, Ca and Mg. The results showed that poultrymanure increased soil and leaf N, P, K, Ca and Mg, and soil OM, growthand tuber yield of the yams compared with the control treatments. Whiteyam produced significantly higher yield than yellow yam. Compared withyellow yam, white yam increased tuber yield by 19%, 26%, 36%, 3% and12%, respectively, for 0, 10, 20, 30 and 40 t/ha poultry manure.Application of poultry manure at 20 t/ha and 30 t/ha significantlyimproved growth and tuber yield of white yam and yellow yam,respectively, compared with the other treatments. These levels of poultrymanure are, therefore, recommended for the two yam species in forest-savanna transition zone of southwest Nigeria. Recommendations ofmanure for yam production should be variety specific.

Degraded soils in humid tropics are characterized by low fertility and high soil erosion potential. Hence, field experiments were conducted during 2018 and 2019 cropping seasons on an Alfisol at Ow...

Use of biochar (B) and poultry manure (PM) as soil amendments can improve the productivity and sustainability of tropical agriculture. Our fieldwork is the first research on the agronomic use of B and PM for the growth of cocoyam in sandy soil of the humid tropics. In this study, the effects of B, PM and their mixture were investigated on soil properties, mineral and nutrient concentrations, growth, and corm and cormel yields of cocoyam during the 2017 and 2018 cropping seasons. The experiment consisted of 4 × 2 factorial combinations of B (0, 10, 20, and 30 Mg ha−1) and PM (0 and 7.5 Mg ha−1). In both years, the application of B and PM either alone or in combination improved soil physical and chemical properties, plant nutritional status, growth, and corm and cormel yields of cocoyam. The combination of 30 Mg ha−1 B and 7.5 Mg ha−1 PM (B30 + PM7.5) gave the highest corm and cormel yields of cocoyam. Pooled over the 2 years, application of B at 30 Mg ha−1 and PM at 7.5 Mg ha−1 (B30 + PM7.5) significantly increased corm yield of cocoyam by 47 and 66%, respectively, when compared with sole PM at 7.5 Mg ha−1 and B at 30 Mg ha−1. Lowest corm and cormel yields were obtained for the unmanure control. The combination of 30 Mg ha−1 B and 7.5 Mg ha−1 PM is recommended for soil fertility management and cocoyam production in the rainforest agroecology of SW Nigeria.

Field experiments were conducted during the 2017 and 2018 cropping seasons, to evaluate the effects of biochar (B) and poultry manure (PM) on soil physical and chemical properties, leaf nutrient co...

Biochar 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.

Tillage and use of organic manure are essential agronomic practices that affect soil properties and have a direct impact on soil sustainability and crop productivity. Hence, a five-year (2012 to 2016) field trial was carried at two sites (Owo — site 1 and Uso — site 2), in the forest-savanna transition zone of southwest Nigeria to assess the effect of tillage and poultry manure on soil physical and chemical properties, growth and yield of ginger (Zingiber officinale Roscoe). The study was a 2 × 5 × 5 factorial experiment with three replicates. The treatments were five tillage methods; zero tillage (ZT), manual ridging (MR), manual mounding (MM), ploughing plus harrowing (P+H), and ploughing plus harrowing twice (P+2H) and five levels of poultry manure (PM) (0, 5.0, 10.0, 15.0, 20.0 t ha−1). Soil bulk density (BD) increased, while soil water content (WC) decreased with increase in tillage intensity, whereas soil OM, N, P, K, Ca, and Mg reduced with increase in tillage intensity, thus ZT conserved soil OM and nutrients the most, and increased nutrient uptake. Soil OM and nutrient concentrations was lowest under the P+2H treatment due to leaching, oxidation, and increased biological activity. The ZT, MR, and MM treatments prompted quicker growth and higher rhizome yield. As PM increased from 0 to 20.0 t ha−1 soil BD and WC tend to improve and soil pH, OM, N, P, K, Ca, and Mg increased. The 15.0 t ha−1 PM gave the highest soil K, Ca, and Mg values. Site 1 had significantly higher growth and yield parameters of ginger compared with site 2. Growth and yield parameters of ginger increased with increase in PM level up to 15.0 t ha−1. Among all tillage cum manure treatments, ZT+15.0 t ha−1 PM gave the highest values of growth and yield parameters of ginger.

Alfisols, the dominant soil order in southwest Nigeria in which crops are grown possess unfavorable peculiarities such as low inherent fertility and acidity. These limitations can be ameliorated by tillage and organic manuring. Therefore, field experiments were conducted during the 2014 and 2015 cropping seasons to assess the effects of tillage methods and maize cob ash (MCA) on soil properties, yield, growth, mineral, and vitamin C contents of okra fruit. The experiment consisted of 3 × 3 factorial combinations of three tillage methods {zero–tillage ZT, manual ridging MR, and plowing plus harrowing P+H} and three rates (0.0, 3.0, and 6.0 t ha−1) of application of MCA. Tillage methods and MCA influenced soil physical and chemical properties, performance, mineral and vitamin C contents of okra fruit significantly. MCA increased soil K, Ca, Mg, okra yield, growth, mineral and vitamin C contents of okra fruits up to 3 t ha−1 level after which there was a decrease. The order of reducing bulk density and soil chemical properties, increasing porosity, yield, growth, mineral and vitamin C contents of okra was: ZT > MR > P+H. Tillage appears to be indispensable for sustainable okra production on Alfisol of southwest Nigeria. Growth and yield of okra in this study was dependent on soil physical properties and chemical properties such as pH, OM, N, and K. Combination of P+H and 3 t ha−1 MCA produced better yield, growth, mineral and vitamin C contents of okra compared with other combinations of tillage with MCA. Addition of MCA to either P+H or MR is important to reduce the limitation of acidity associated with tropical Alfisol.

The nutritional effects of green manure on soil and crop plants depends on residue quality. Hence field experiments were carried out during the cropping seasons of 2015 and 2016 to compare the impact of different green manures and NPK 15-15-15 fertilizer on soil properties, growth, yield, mineral and vitamin C composition of okra (Abelmoschus esculentus (L.) Moench). The experiment each year consisted of four green manure (GM) types {Pawpaw (Carica papaya L.) leaves, Neem (Azadirachta indica A. Juss.) leaves, Moringa (Moringa oleifera Lam.) leaves, and Mesquite (Prosopis africana Guill., Perr. & A. Rich) Taubert leaves}, NPK 15-15-15 fertilizer and a control. The six treatments were arranged in a randomized complete block design with four replications. Application of GMs reduced soil bulk density and increased soil organic matter (OM), N, P, K, Ca, Mg, growth and yield of okra compared with the control. NPK fertilizer did not reduce soil bulk density and increase soil OM, but did increase soil N, P, K, Ca, Mg, growth and yield of okra compared with the control. Mesquite increased growth and yield of okra compared with NPK fertilizer and other GMs. This was due to increased availability of N and K in the soil at the level of this treatment. Using the means of the two years and compared with the control and NPK fertilizer, Mesquite increased pod yield of okra by 214 and 53%, respectively. Also GMs and NPK fertilizer increased okra mineral and vitamin C contents compared with the control. Moringa had the best fruit quality in terms of higher K, Ca, Fe, Zn, Cu, and vitamin C contents compared with other GMs and NPK fertilizer. Therefore, for those that desire to grow okra for the quality of its fruits, Moringa (Moringa oleifera) is recommended, however for those that desire quantity, Mesquite (Prosopis africana) is recommended. Keywords: Bulk density, Moringa oleifera, Carica papaya, Azadirachta indica, Prosopis africana

Fallowing is considered an important management strategy for the restoration of soil productivity. Therefore, a three-year fallow of pigeon pea (Cajanus cajan), mexican sunflower (Tithonia diversifolia) and elephant grass (Pennisetum purpureum) was established at Landmark University, Nigeria between 2016 – 2019. Leaf nutrient concentrations of maize (Zea mays) planted with soils taken from each fallowed plots after three years were also determined. The experimental design was a randomized complete block design with three replications. Soil samples were collected from each fallow plots for physical and chemical analysis (bulk density, porosity, moisture content, particle size, dispersion ratio, soil erosion loss, soil organic matter (SOM), total N, available P, exchangeables K, Ca, Mg, CEC and pH.) before and at the end of the experiment. Means of data collected were separated using Tukey's HSD test at p = 0.05. Tithonia fallow improved soil properties and leaf nutrient concentration of maize compared with Pennisetum and Cajanus fallows. The order was Tithonia > Pennisetum > Cajanus. This was adduced to the regular return of plant residues to the soil in Tithonia fallow which resulted in high SOM (Tithonia increased SOM by about 23%, 7.5%, and 20%, respectively, compared with the initial soil, Pennisetum and Cajanus fallows) and increases soil N, P, K, Ca, Mg, CEC and pH and also stabilized soil structure by increasing porosity, moisture content and reducing bulk density, dispersion ratio, and soil loss. Therefore, plant species of high nutrient contents and high return of biomass to the soil are necessary for quick restoration of soil productivity in a derived savanna ecology., Cajanus cajan, Tithonia diversifolia, Pennisetum purpureum, SOM, fallow, soil chemical properties, soil physical properties

Research information on the effects of biochar and poultry manure on the growth, yield and concentrations of nutrients in edible portions of sweet potato is rare, as essential nutrient concentrations in crops can affect human health. Hence, field experiments were carried out for two growing seasons (2019 and 2020) at two degraded sites using a randomized complete block design in a factorial layout with three replications to evaluate the effects of biochar (B), poultry manure (PM) and their combined application on leaf nutrient concentrations, root storage minerals, growth and yield of sweet potato. Each year, the experiment consisted of 4 × 3 factorial combinations of biochar (0, 10.0, 20.0 and 30.0 t ha-1) and poultry manure (0, 5.0 and 10.0 t ha-1). The results showed that the sole application of B and PM and their combined application, improved sweet potato leaf nutrient concentrations, root storage minerals, growth and yield of sweet potato. In both years, there were significant interactions of B and PM (B × PM) on leaf nutrient concentrations, root storage minerals, growth and yield of sweet potato that were determined, indicating the potential of B in enhancing PM use efficiency and improving better use of the nutrients in the PM. It was found that the highest application rate of 30.0 t ha-1 B and 10.0 t ha-1 PM (B30 +PM 10) gave the highest leaf nutrient concentrations, root storage minerals, growth and yield of sweet potato at both sites. Averaged over two years, the highest application rate of B at 30.0 t ha -1 and PM at 10.0 t ha-1 (B30 +PM 10) significantly increased tuber yield of sweet potato by 108, 147, 196, 89, 124 and 220%, compared with B alone at 30.0 t ha-1 (B30 +PM 10), B alone at 20.0 t ha-1 (B 20 +PM 0 ), B alone at 10.0 t ha-1 (B10 +PM0), PM alone at 10.0 t ha-1 (B30 +PM10), PM alone at 5.0 t ha-1 (B0 +PM5) and no application of B or PM (control) (B 0 +PM 0 ), respectively. Lowest leaf nutrient concentrations, root storage minerals, growth and yield was obtained for the control. The study indicated that B in combination with PM have the potential to improve sweet potato growth and yield, leaf nutrient concentrations and root storage minerals of sweet for human health in severely degraded soils. The results of this work should be verified for different soil types, crops and agroecological zones. Future research should focus on long-term field studies to fully understand the behaviour of biochar under natural circumstances. The use of variable rates of biochar, poultry manure and their combine application on should also be considered.

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.

SUMMARYGreen manures (GM) as an alternative to inorganic fertilizer offer considerable potential as a source of plant nutrients and organic matter (OM). Hence, field experiments were carried out during 2015 and 2016 cropping seasons to compare impacts of GM and NPK (15:15:15) fertilizer on soil properties, growth, fruit yield, mineral, lycopene and vitamin C contents of tomato (Lycopersicon esculentumMill). GMs were composed by green tender stems and leaves of pawpaw (Carica papayaL.), neem (Azadirachta indicaA. Juss.), moringa (Moringa oleiferaLam.) or gliricidia (Gliricidia sepium(Jacq.) Kunth ex Walp.) and applied at 5 Mg ha−1, whereas NPK was applied at 300 kg ha−1and there was a no fertilizer plot (control). Application of GMs reduced soil bulk density and increased soil OM, N, P, K, Ca, Mg, growth, number of fruits and fruit yield of tomato compared with the control. NPK fertilizer had no effect on soil bulk density and soil OM, but it increased soil fertility and tomato yield as compared with the control. When comparing treatments, the highest tomato yield and best cost:benefit ratio were obtained with gliricidia as GM. The GMs and NPK fertilizer increased mineral, lycopene and vitamin C contents in tomato fruits and the highest K, Ca, Fe, Zn, Cu, lycopene and vitamin C contents in tomato fruits were found with moringa as GM. Our results revealed that GM has potential to improve soil properties, tomato yield and quality, being an alternative for cropping management.

A field experiment was conducted over two years to evaluate the effects of biochar (B) and poultry manure (PM) on soil properties, leaf nutrient concentrations and root yield of radish. The experim...

A field experiment was conducted in the forest-savanna transition zone of Nigeria from May to July 2014 and September to November 2015 to determine the impacts of poultry manure (PM) and NPK fertilizer on soil physical properties, and growth and yield of carrot (Daucus carota L.). The five treatments included no manure or fertilizer (control); 10, 20, and 30 megagrams (Mg)·ha-1 of PM; and 300 kg·ha-1 of 15 N-15 P-15 K fertilizer. All levels of PM reduced soil bulk density and temperature, and improved total porosity and moisture content compared to the NPK fertilizer and the control. Plant height, number of leaves, root diameter, root length, and fresh root yield in the PM and NPK fertilizer treatments were improved compared to the control. Growth and yield parameters of carrot plants treated with 20 and 30 Mg·ha-1 PM were higher than the other treatments. The 10 Mg·ha-1 PM and NPK fertilizer treatments produced similar growth and yield responses. There was an interaction for year (Y) × fertilizer (F) on plant height, number of leaves, and fresh root yield. Relative to the control 10, 20, or 30 Mg·ha-1 PM and NPK fertilizer increased fresh root yield of carrot by 39.9%, 62.0%, 64.9%, and 37.3%, respectively. The 20 Mg·ha-1 PM treatment best improved soil properties and carrot productivity as indicated by the benefit-to-cost ratio.

The type of materials used as mulch and season of application may determine its impact on soil physical and chemical properties and crop yield. Hence, field experiments were carried out during 2015 (dry) and 2016 (wet) cropping seasons to determine the effect of various mulch materials on soil properties, leaf nutrient composition, yield and growth of okra (Abelmoschus esculentus (L.) Moench). The experiment consisted of four mulch materials (a) Pueraria phaseoloides, (b) Mucuna pruriens, (c) Pennisetum purpureum), (d) Panicum maximum and a control (no mulch application). The five treatments were arranged in a randomized complete block design with four replications. Application of mulch reduced bulk density, soil temperature and increased porosity, soil moisture content, pH, OM, soil and leaf N, P, K, Ca, Mg, pod yield and growth of okra compared with the control. Legume mulch materials (LMM) (Pueraria and Mucuna) produced higher values of OM, N, P, K, Ca and Mg compared with grass mulch materials (GMM) (Pennisetum and Panicum) in both seasons. GMM significantly (p ≤ 0.05) reduced bulk density and soil temperature and increased porosity and moisture content compared with the LMM in 2015. The correlation coefficient showed that the yield of okra in 2015 was dependent on soil physical properties while the yield in 2016 was dependent on soil chemical properties. GMM in 2015 produced 49% and 158% higher pod yield compared with LMM and the control, respectively. LMM increased the pod yield of okra in 2016 by 56% and 122% compared with GMM and the control, respectively. Therefore the use of grass materials as mulch in the dry season and the use of legume mulches during the wet season maximized yields

Tillage, biochar, poultry manure, NPK fertilizer and their combined application could improve soil quality, sustainability and carrot productivity. The effects of two tillage treatments: conventional tillage (CT) and reduced tillage (RT) each combined with 30 Mg ha−1 biochar (B), 10 Mg ha−1 poultry manure (PM), 300 kg ha−1 NPK 15-15-15 fertilizer, 150 kg ha−1 NPK 15-15-15 fertilizer +15 Mg ha−1 biochar +5 Mg ha−1 poultry manure and a control (no biochar/poultry manure/NPK fertilizer) on soil properties, growth and carrot yield were investigated. The research was carried out for two consecutive growing seasons (2018 and 2019) at Owo in the forest-savanna transition zone of Nigeria on a sandy loam. The experiment was laid out in a randomized complete block design in a factorial combination of ten treatments and replicated three times. Reduced tillage had relatively lower soil bulk density, penetration resistance, dispersion ratio and temperature, and had significantly higher (p = 0.05) soil aggregate stability, mean weight diameter, porosity and water content than conventional tillage and these resulted in higher soil pH, organic C, N, P, K, Ca and Mg, growth and fresh root yield of carrot compared with conventional tillage. Reduced tillage increased fresh carrot root yield by 2.3 Mg ha−1 and 2.6 Mg ha−1 for the first and second growing seasons, respectively, compared with conventional tillage, which corresponded to a 11.1% increment for both years. Application of biochar alone, poultry manure alone and complementary application of NPK fertilizer, biochar and poultry manure decreased soil bulk density, penetration resistance, dispersion ratio and temperature and increased soil water content, porosity, aggregate stability and mean weight diameter whereas NPK fertilizer did not improve these soil physical properties. Biochar alone, poultry manure alone, NPK fertilizer alone and combined application of NPK fertilizer, biochar and poultry manure increased soil total N, available P, and exchangeable K, Ca and Mg concentrations compared with the control. Application of biochar alone improved soil pH, OC, K, Ca and Mg better than the NPK fertilizer. Poultry manure improved soil pH, OC, N, K, Ca and Mg better than the NPK fertilizer. Combined application of NPK fertilizer, biochar and poultry manure at sub-optimal rates gave higher soil N, P, K, Ca and Mg concentrations, higher plant, number of leaves, root length, root diameter and fresh carrot root yield compared with NPK fertilizer or biochar or poultry manure alone. Compared with control, NPK fertilizer alone, biochar alone, poultry manure alone and mixture of NPK fertilizer, biochar and poultry manure increased fresh carrot root yield by 43, 24, 46 and 76%, respectively. Reduced tillage in combination with NPK fertilizer, biochar and poultry manure gave the highest fresh carrot root yield. The results indicated that reduced tillage in combination with NPK fertilizer, biochar and poultry manure prove to be an effective and sustainable management strategy for improving soil quality and carrot yield than conventional tillage in combination with NPK fertilizer, biochar and poultry manure.

SUMMARYTillage and use of organic manure are important agronomic practices that sustain high crop and soil productivity. Hence, a three-year (2007 to 2009) study was conducted to evaluate the effect of site, tillage and poultry manure (PM) treatments on soil and plant nutrients composition, growth and yield of cocoyam (Xanthosoma sagittifolium). The study was a 2 × 5 × 5 factorial experiment with two sites (Owo – site 1 and Obasooto – site 2), five tillage methods; manual clearing (MC), manual ridging (MR), manual mounding (MM), ploughing plus harrowing (P+H) and ploughing plus harrowing twice (P+2H) and five levels of PM (0, 2.5, 5.0, 7.5, 10.0 t ha−1). Treatments were replicated thrice. Soil OM, N, P, K, Ca, Mg and leaf nutrients reduced with increase in tillage intensity, thus MC conserved soil nutrients the most, and increased nutrient uptake. Soil and plant nutrient concentration was lowest under the P+2H treatment. The MC, MR and MM treatments led to faster growth and higher tuber yield. As PM increased from 0 to 10.0 t ha−1 soil pH, OM, soil and plant N, P, K, Ca and Mg increased. The 7.5 t ha−1 PM gave the highest leaf K, Ca and Mg values. Owo site had significantly higher yield and growth parameters of cocoyam compared with Obasooto site. Yield and growth parameters of cocoyam increased with increase in PM level up to 7.5 t ha−1. Out of all tillage cum manure treatments, MC+7.5 t ha−1 PM gave the highest values of yield and growth parameters.

Field experiments were carried out during 2012 and 2013 cropping seasons on an Alfisol (Oxic Tropuldalf) at Owo in the forest – savanna transition zone of southwest Nigeria to evaluate the effect of different ti llage systems (zero tillage (ZT), ploughing plus harrowing (P+H) and ploughing plus harrowing twice (P+2H), and with or without Tithonia diversifolia mulch (TM) on soil properties, growth and yield of cocoyam. The experiment was laid out in a randomized co mplete block design in a factorial combination of six treatments that were replicated three times. Among the tillage systems, zero tillage had the highest soil moisture content (12.3%), lowest soil temperature (31.8 ° C) and lower soil bulk density (1.36 Mg m - 3 ) and higher total porosity (48.7%) that was similar to P+H. ZT also produced the best values of soil chemical properties, growth and yield of coco yam compared with P+H and P+2H. P+2H had the highest soil bulk density (1.56 Mg m

Field experiments were conducted at Owo, southwest Nigeria to select organic fertilizer treatments most suitable for sustaining high soil fertility and yam productivity on a nutrient-depleted tropical Alfisol. Eight organic fertilizer treatments were applied at 20 t ha−1 with a reference treatment inorganic fertilizer (NPK 15–15–15) at 400 kg ha−1 and natural soil fertility (control), laid out in a randomized complete block design with three replications. Results showed that organic fertilizers significantly increased (p = 0.05) tuber weight and growth of yam, soil and leaf N, P, K, Ca and Mg, soil pH and organic C concentrations compared with the NSF (control). The oil palm bunch ash + poultry manure treatment increased tuber weight, vine length, number of leaves and leaf area of yam by 66, 25, 21 and 52%, respectively, compared with inorganic fertilizer (NPK) and 37, 22, 19 and 44%, respectively, compared with poultry manure alone. Sole or mixed forms of organic fertilizers showed significant improvemen...

Plant materials differ in their chemical composition, rate of decomposition and suitability as mulch materials. Experiments were conducted during 2006–2007 and 2007–2008 cropping seasons for early yam cultivation at Owo in the forest–savanna transition zone of southwest Nigeria to study the effect of Chromolaena odorata and Tithonia diversifolia mulches applied at 0.0, 5.0, 7.5, 10.0 and 12.5 t ha−1 on soil chemical properties, leaf nutrient composition, growth and tuber yield of white yam (Dioscorea rotundata Poir). Both C. odorata and T. diversifolia mulches reduced soil bulk density and temperature; increased concentrations of soil organic matter (SOM), total N, available P, exchangeable K, Ca and Mg, leaf N, P, K, Ca and Mg; enhanced growth and yield of yam compared with control. The values of SOM, total N and available P and leaf N and P concentrations increased with increasing mulch rate. C. odorata mulch and T. diversifolia mulch applied at 10.0 and 7.5 t ha−1, respectively, was found to be suitabl...

In Nigeria, information is lacking regarding the most suitable tillage method in extensive yam production. Hence, five tillage methods were compared at two sites in 2008–2010 with reference to their effects on soil physical and chemical properties, leaf nutrient concentrations, growth and tuber yield of yam (Dioscorea rotundata Poir) on Alfisols at Owo (site A) and Akure (site B), south-west Nigeria. The tillage methods were: zero tillage (ZT), manual ridging (MR), manual mounding (MM), ploughing + harrowing (P + H) and ploughing + harrowing + ridging (P + H + R). P + H + R had lower soil bulk density than other tillage methods and resulted in higher leaf N, P, K, Ca and Mg and yam tuber yield. In ZT, bulk density, soil moisture content, soil organic C, N, P, K, Ca and Mg were significantly higher and temperature lower than other tillage methods. Results of multiple regressions revealed that bulk density significantly influenced the yield of yam rather than soil chemical properties. Compared with MR, MM, ...

Field experiments were conducted during 2013, 2014 and 2015 cropping seasons at Rufus Giwa Polytechnic, Owo, Ondo State, southwest Nigeria. The objective of the investigation was to determine the effect of Cocoa Pod Ash (CPA) and Poultry Manure (PM) applied solely and their combined form, as sources of fertilizers on soil properties, leaf nutrient composition, growth and yield of yam. Three soil amendments: CPA, PM (sole forms), CPA and PM (mixture), were applied at 20 t ha-1 with an inorganic fertilizer (NPK 15-15-15) at 400 kg ha-1 as a reference and a natural soil fertility, NSF (control). The five treatments were arranged in a randomized complete block design with three replications. The test soil was slightly acidic, low in organic carbon (OC), N, P, K, Ca and Mg. Results showed that soil amendments significantly increased (p = 0.05) tuber weights and growth of yam, soil and leaf N, P, K, Ca and Mg, soil pH and OC concentrations compared with the NSF (control). The mixture of CPA+PM treatment increased tuber weights of yam by 36%, compared with inorganic fertilizer (NPK) and 19%, compared with PM alone. Sole PM increased tuber weight of yam by 15%, compared with NPK. Sole or mixed forms of soil amendments showed remarkable improvement in soil physical properties, nutrient availability, compared with NPK and the NSF (control). Integrated application of CPA at 10 t ha-1 + PM at 10 t ha-1 was the most effective treatment in improving soil physical properties, increasing nutrient availability and yam performance than sole application of any of the fertilizer materials., {"references":["S.K. Hahn, D.S.O. Osiru, M.O. Akoroda and J.A. Otoo, \"Yam production and its future prospects\". Outlook Agriculture, 16(3):105-110, 1987.","C.A. Okoh, \"The effect of mulching on soil physico-chemical properties and the yield of white yam\", Tropical Journal of Root Tuber Crops, 4(2):24-31, 2004.","T.M. Agbede, \"Effect of tillage on soil properties and yam yield on an Alfisol of southwestern Nigeria\", Soil Tillage Research, 86(1):1-8, 2006.","G.C. Orkwor, R. Asiedu and I.J. Ekanayake, \"Food Yams: Advances in Research. International Institute of Tropical Agriculture (IITA), Ibadan, National Root Crops Research Institute, Umudike, Nigeria, 249 p, 1998.","G.O. Obigbesan, A. A. Agboola and A.A.A. Fayemi, \"Effect of potassium on tuber yield and nutrient uptake of yam\", In: J. Cock, R. MacIntyre and M. Graham (Eds.). Proceedings of the 4th Symposium of the International Society for Tropical Root Crops, CIAT, Cali, Colombia, 1-7 August 1976, pp. 104-107, 1976.","G.O. Obigbesan, \"In: Potassium Workshop\", Oct. 1980, IITA, Ibadan, Nigeria, 1980.","S.O. Ojeniyi, \"Effect of goat manure on soil nutrient and okra yield in a rainforest area of Nigeria\", Applied Tropical Agriculture, 5:20-23, 2000.","T.M. Agbede, A.O. Adekiya and J.S. Ogeh, \"Effects of organic fertilizers on yam productivity and some soil properties of a nutrient-depleted tropical Alfisol\", Archives of Agronomy and Soil Science, 59(4-6):803-822, 2013.","O.A. Egunjobi, \"On the possible utilization of discarded cocoa (Theobroma cacao L.) pod husks as fertilizer and nematicides\", Proceedings of the 5th International Cocoa Research Conference, CRIN, Ibadan, Sept. 1-9, 1975, pp. 541-547, 1976. \n[10]\tH.K. Adu-Daapah, J. Cobbinah and E.O. Asare, \"Effect of cocoa pod ash on the growth of maize\", Journal of Agricultural Science, 122:31-33, 1994.\n[11]\tD.I. Akanni and S.O. Ojeniyi, \"Effect of different levels of poultry manure on soil physical properties, nutrient status, growth and yield of tomato (Lycopersicon esculentum)\", Research Journal of Agronomy, 1:1-4, 2007.\n[12]\tL.S. Ayeni and M.T. Adetunji, \"Integrated application of poultry manure and mineral fertilizer on soil chemical properties, nutrient uptake, yield and growth components of maize\", Nature and Science, 8(1):60-67, 2010.\n[13]\tL. Degras, \"The yam: a tropical root crop. London: Macmillan/ The Technical Centre for Agricultural and Rural Cooperation, 1993.\n[14]\tG.O. Obigbesan and A.A Agboola, \"Uptake and distribution of nutrients by yams (Dioscorea spp) in western Nigeria\", Experimental Agriculture, 14:349-355, 1978.\n[15]\tSoil Survey Staff, \"Keys to soil taxonomy\", 11th Edition. Agriculture Handbook, No. 436. United States Department of Agriculture and Natural Resources Conservation Service, Washington DC, 2010. \n[16]\tFAO, \"World reference base of soil resources\", World Soil Resources Report 84. Foods and Agriculture Organisation of the United Nations, Rome, 1998.\n[17]\tT.M. Agbede and A.O. Adekiya, \"Effects of poultry manure on soil fertility, growth and yield of white yam and yellow yam\". University of Khartoum Journal of Agricultural Sciences, 20(3):286-303, 2012.\n[18]\tE.U, Onweremadu, I.I Ibeawuchi and C.I. Duruigbo, \"Land evaluation and productivity of organically-fertilized crop mixtures in a degraded soil\", Nature and Science, 6(1):34-42, 2008.\n[19]\tM. Pansu and J. Gautheyrou, \"Handbook of Soil Analysis\". Mineralogical, Organic and Inorganic Methods. Springer-Verlag, Berlin Heidelberg, New York, 995pp, 2006.\n[20]\tW. Horwitz, Editor, \"Official Methods of Analysis of the Association of Official Analytical Chemists International\". 16th Edition. AOAC International, Gaithersburg, MD; 1298pp, 1997.\n[21]\tH. Shiwachi, C.C. Okonkwo and R. Asiedu, \"Nutrient deficiency symptoms in yams (Dioscorea spp)\", Tropical Science, 44:155-162, 2004.\n[22]\tE.A. Akinrinde and G.O. Obigbesan, \"Evaluation of the fertility status of selected soils for crop production in five ecological zones of Nigeria\", In: O. Babalola (Ed.). Proceedings of the 26th Annual Conference of Soil Science Society of Nigeria; 2000 Oct 30 – Nov 3; Ibadan, pp. 279-288, 2000.\n[23]\tM.I. Onwuka, V.E. Osedeke, and N.A. Okolo, \"Amelioration of soil acidity using cocoa husk ash for maize production in Umudike area of southeast Nigeria\", Tropical and Subtropical Agroecosystems, 7:41-45, 2007. \n[24]\tJ.S.C. Mbagwu and A. Piccolo, \"Changes in soil aggregate stability induced by amendment with humic substances\", African Journal of Biotechnology, 5:1058-1061, 1989.\n[25]\tE.I. Moyin-Jesu, \"Evaluation of different organic fertilizers on the soil, leaf chemical composition and growth performances of coffee seedlings (Coffee arabica L.)\", African Journal of Science and Technology (AJST)), Science and Engineering Series, 9(2):105-112, 2008.\n[26]\tL.S. Ayeni, M.T. Adetunji, S.O. Ojeniyi, B.S. Ewulo and A.J. Adeyemo, \"Comparative and cumulative effect of cocoa pod husk ash and poultry manure on soil and nutrient contents and maize yield\", American-Eurasian Journal of Sustainable Agriculture, 2(1):92-97, 2008.\n[27]\tK. Agyarko and E.K. Asiedu, \"Cocoa pod husk and poultry manure on soil nutrients and cucumber growth\", Advances in Environmental Biology, 6(11):2870-2874, 2012.\n[28]\tE.O. Adeleye and L.S. Ayeni, \"Effect of cocoa pod ash and poultry manure combinations on soil and plant nutrient contents and performance of maize – Screenhouse Experiment\", Researcher, 2(12):51-56, 2010.\n[29]\tS.O. Ojeniyi, M.A. Awodun and S.A. Odedina, \"Effect of animal manure amended spent grain and cocoa husk on nutrient status, growth and yield of tomato\", Middle-East Journal of Scientific Research, 2(1):33-36, 2007.\n[30]\tJ.N. O'Sullivan, \"Yam nutrition: Nutrient disorders and soil fertility management\", Australian Centre for International Agricultural Research (ACIAR) Monograph No. 144, Canberra, 112 pp, 2010."]}

An experiment was carried out for three consecutive years at Owo, southwest Nigeria. The objective of the investigation was to determine the effect of Cocoa Pod Ash (CPA) and Poultry Manure (PM) applied solely and their combined form, as sources of fertilizers on soil properties, leaf nutrient composition, growth and yield of cocoyam. Three soil amendments: CPA, PM (sole forms), CPA and PM (mixture), were applied at 7.5 t ha-1 with an inorganic fertilizer (NPK 15-15-15) at 400 kg ha-1 as a reference and a natural soil fertility, NSF (control), arranged in a randomized complete block design with three replications. Results showed that soil amendments significantly increased (p = 0.05) corm and cormel weights and growth of cocoyam, soil and leaf N, P, K, Ca and Mg, soil pH and organic carbon (OC) concentrations compared with the NSF (control). The mixture of CPA+PM treatment increased corm and cormel weights, plant height and leaf area of cocoyam by 40, 39, 42, and 48%, respectively, compared with inorganic fertilizer (NPK) and 13, 12, 15 and 7%, respectively, compared with PM alone. Sole or mixed forms of soil amendments showed remarkable improvement in soil physical properties compared with NPK and the NSF (control). The mixture of CPA+PM applied at 7.5 t ha-1 was the most effective treatment in improving cocoyam yield and growth parameters, soil and leaf nutrient composition., {"references":["D.F. Uwah, A.U. Udoh and G.A. Iwo, \"Effect of organic and mineral fertilizers on the growth and yield of cocoyam (Colocasia esculenta (L.) Schott)\", International Journal of Agricultural Sciences, 3(1):33-38, 2011.","A.O. Adekiya, T.M. Agbede and S.O. Ojeniyi, \"The Effect of three years of tillage and poultry manure application on soil and plant nutrient composition, growth and yield of cocoyam\", Experimental Agriculture, pp. 1-11, 2015. doi: 10.1017/S0014479715000253.","B.A. Ndon, N.H. Ndulaka and N.U. Ndaeyo, \"Stabilization of yield parameters and some nutrients components in cocoyam cultivars with time in Uyo, southeastern Nigeria\", Global Journal of Agricultural Science, 2(2):74-78, 2003.","I C. Onwueme and T.D. Sinha, \"Field Crop Production in Tropical Africa, CTA Ede\". The Netherlands, pp. 1-480, 1991.","D. Som, \"Handbook of Horticulture, Indian Council of Agricultural Research\", New Delhi, pp. 507-508, 2007.","J.O. Erhabor and W. A. Molindo, \"Assessing nutrient potentials of a soil continuously cropped with Xanthosoma sagittifolia (L) in Onisere, Ondo State, Nigeria\", Agricultural Journal 5(4):269-272, 2010.","G.O. Obigbesan, A. A. Agboola and A.A.A. Fayemi, \"Effect of potassium on tuber yield and nutrient uptake of yam\", In: J. Cock, R. MacIntyre and M. Graham (Eds.). Proceedings of the 4th Symposium of the International Society for Tropical Root Crops, CIAT, Cali, Colombia, 1-7 August 1976, pp. 104-107, 1976.","G.O. Obigbesan, \"In: Potassium Workshop\", Oct. 1980, IITA, Ibadan, Nigeria, 1980.","S.O. Ojeniyi, \"Effect of goat manure on soil nutrient and okra yield in a rainforest area of Nigeria\", Applied Tropical Agriculture, 5:20-23, 2000.\n[10]\tT.M. Agbede, A.O. Adekiya and J.S. Ogeh, \"Effects of organic fertilizers on yam productivity and some soil properties of a nutrient-depleted tropical Alfisol\", Archives of Agronomy and Soil Science, 59(4-6):803-822, 2013.\n[11]\tO.A. Egunjobi, \"On the possible utilization of discarded cocoa (Theobroma cacao L.) pod husks as fertilizer and nematicides\", Proceedings of the 5th International Cocoa Research Conference, CRIN, Ibadan, Sept. 1-9, 1975, pp. 541-547, 1976. \n[12]\tH.K. Adu-Daapah, J. Cobbinah and E.O. Asare, \"Effect of cocoa pod ash on the growth of maize\", Journal of Agricultural Science, 122:31-33, 1994.\n[13]\tD.I. Akanni and S.O. Ojeniyi, \"Effect of different levels of poultry manure on soil physical properties, nutrient status, growth and yield of tomato (Lycopersicon esculentum)\", Research Journal of Agronomy, 1:1-4, 2007.\n[14]\tL.S. Ayeni and M.T. Adetunji, \"Integrated application of poultry manure and mineral fertilizer on soil chemical properties, nutrient uptake, yield and growth components of maize\", Nature and Science, 8(1):60-67, 2010.\n[15]\tB. Osundare, \"Effect of fertilizer types and varying population on the performance of cocoyam\", Moor Journal of Agricultural Research, 5(1-2):7-12, 2004.\n[16]\tJ. Vicente-Chandler, H. Irizarry and S. Silva, \"Nutrient uptake by taniers as related to stage of growth and effect of age on yields of the Morada variety\", Journal of Agriculture of University of Puerto Rico, 66(1):1-10, 1982.\n[17]\tSoil Survey Staff, \"Keys to soil taxonomy\", 11th Edition. Agriculture Handbook, No. 436. United States Department of Agriculture and Natural Resources Conservation Service, Washington DC, 2010. \n[18]\tFAO, \"World reference base of soil resources\", World Soil Resources Report 84. Foods and Agriculture Organisation of the United Nations, Rome, 1998.\n[19]\tT.M. Agbede, \"Effect of tillage on soil properties and yam yield on an Alfisol of southwestern Nigeria\", Soil Tillage Research, 86(1):1-8, 2006. \n[20]\tA.O. Adekiya, S.O. Ojeniyi and T.M. Agbede, \"Poultry manure effects on soil properties, leaf nutrient status, growth and yield of cocoyam in a tropical Alfisol\", Nigerian Journal of Soil Science, 22(2):30-39, 2012.\n[21]\tS.O. Ojeniyi, O.A. Amusan and A.O. Adekiya, \"Effect of poultry manure on soil physical properties, nutrient uptake and yield of cocoyam (Xanthosoma sagittifolium) in southwest Nigeria\", American-Eurasian Journal of Agricultural and Environmental Science, 13(1):121-125, 2013. \n[22]\tA. Agueguia, \"Non-destructive estimation of leaf area in cocoyam (Xanthosoma sagittifolium (L.) Schott)\", Journal of Agronomy and Soil Science, 171(2):138-141, 1993. \n[23]\tM. Pansu and J. Gautheyrou, \"Handbook of Soil Analysis\". Mineralogical, Organic and Inorganic Methods. Springer-Verlag, Berlin Heidelberg, New York, 995pp, 2006.\n[24]\tW. Horwitz, Editor, \"Official Methods of Analysis of the Association of Official Analytical Chemists International\". 16th Edition. AOAC International, Gaithersburg, MD; 1298pp, 1997.\n[25]\tN.R. Hulugalle, R. Lal and O.A. Opara-Nadi, \"Effect of tillage system and mulch on soil properties and growth of yam (Dioscorea rotundata) and cocoyam (Xanthosoma sagittifolium) on an Ultisol\", Journal of Root Crops, 11(1-2):9-22, 1985.\n[26]\tT.M. Agbede, \"Nutrient availability and cocoyam yield under different tillage practices\", Soil Tillage Research, 99(1):49-56, 2008.\n[27]\tS. Kabeerathumma, B. Mohankumar and P.G. Nair, \"Nutrient uptake and their utilization by yams, aroids and coleus\", Technical Bulletin Series 10, Central Tuber Crops Research Institute (CTCRI), Thiruvananthapuram, Kerala, India, 1987. \n[28]\tE.A. Akinrinde and G.O. Obigbesan, \"Evaluation of the fertility status of selected soils for crop production in five ecological zones of Nigeria\", In: O. Babalola (Ed.). Proceedings of the 26th Annual Conference of Soil Science Society of Nigeria; 2000 Oct 30 – Nov 3; Ibadan, pp. 279-288, 2000.\n[29]\tM.I. Onwuka, V.E. Osedeke, and N.A. Okolo, \"Amelioration of soil acidity using cocoa husk ash for maize production in Umudike area of southeast Nigeria\", Tropical and Subtropical Agroecosystems, 7:41-45, 2007. \n[30]\tJ.S.C. Mbagwu and A. Piccolo, \"Changes in soil aggregate stability induced by amendment with humic substances\", African Journal of Biotechnology, 5:1058-1061, 1989.\n[31]\tE.I. Moyin-Jesu, \"Evaluation of different organic fertilizers on the soil, leaf chemical composition and growth performances of coffee seedlings (Coffee arabica L.)\", African Journal of Science and Technology (AJST)), Science and Engineering Series, 9(2):105-112, 2008.\n[32]\tL.S. Ayeni, M.T. Adetunji, S.O. Ojeniyi, B.S. Ewulo and A.J. Adeyemo, \"Comparative and cumulative effect of cocoa pod husk ash and poultry manure on soil and nutrient contents and maize yield\", American-Eurasian Journal of Sustainable Agriculture, 2(1):92-97, 2008.\n[33]\tK. Agyarko and E.K. Asiedu, \"Cocoa pod husk and poultry manure on soil nutrients and cucumber growth\", Advances in Environmental Biology, 6(11):2870-2874, 2012.\n[34]\tS.O. Ojeniyi, M.A. Awodun and S.A. Odedina, \"Effect of animal manure amended spent grain and cocoa husk on nutrient status, growth and yield of tomato\", Middle-East Journal of Scientific Research, 2(1):33-36, 2007."]}

SUMMARYExperimental data on tillage requirement of cocoyam (Xanthosoma sagittifolium) are needed to identify the most suitable tillage methods for managing the fragile Alfisols of the humid tropics to ensure sustained productivity. Hence, five tillage methods were compared as to their effects on soil physical and chemical properties, and growth and yield of cocoyam on an Alfisol at Owo in the forest-savanna transition zone of southwest Nigeria. The experiment consisted of five tillage methods: manual clearing (MC), manual ridging (MR), manual mounding (MM), ploughing + harrowing (P + H) and ploughing + harrowing twice (P + 2 H) were used for three years at two sites in a randomized complete block design with three replications. In the first two years (2007 and 2008), P + H produced the least soil bulk density and highest growth and yield, whereas in the third year (2009), MC produced the lowest soil bulk density and best performance of cocoyam. Manual clearing produced the best values of soil chemical properties in 2008 and 2009. Averaged over the three years, P + H, MR and MM had lower soil bulk density hence better growth and yield compared with P + 2 H and MC. Over the three years MC, MM, MR and P + H increased cocoyam cormel yield by 10, 21, 23 and 32%, respectively, over P + 2 H.The corresponding increases in corm yield were 7, 15, 13 and 21%, respectively. The multiple regressions revealed that bulk density and moisture content significantly influenced the yield of cocoyam. Soil chemical properties were not significant. Bulk density rather than soil chemical properties dictated the performance of cocoyam in an Alfisol of southwest Nigeria. Soil quality was degraded by P + 2H. For small farms, either MR or MM is recommended while P + H is recommended for large-scale farming of cocoyam.

Field experiments were carried out at Owo, southwest Nigeria to evaluate the effect of different tillage practices (zero tillage with mulch (ZTM), row tillage (RT) and conventional tillage (CT), and with or without oil palm bunch ash plus poultry manure (OBA+PM) on soil chemical properties, growth and yield of ginger. The experiment was laid out in a randomized complete plot design with three replications. Soil chemical properties, growth and fresh rhizome yield reduced with frequency/intensity of tillage imposed while application of OBA+PM increased them. Among the tillage practices, the highest fresh rhizome yield (15.0t ha-1) was produced by ZTM which was significantly different from other tillage practices. Among the tillage – OBA+PM combinations, the most satisfactorily yield (20.1t ha-1) was produced by ZTM+OBA+PM while the lowest yield (15.7t ha-1) was in CT+OBA+PM., {"references":["National Root Crops Research Institutes (NRCRI), \"Ginger\nProgramme\", An Overview. National Root Crops Research Institute,\nUmudike, Nigeria, 2009.","S. O. Ojeniyi, \"Comparison of Row Tillage and No Tillage and Manual\nMethods. Effect on Soil Properties and Cowpea\" In: Proceedings of the\n12th Conference of International Soil Tillage Research Organization, pp.\n141-145, IITA, Ibadan, 1991.","A.O. Adekiya and T.M. Agbede, \"Soil Physical Properties and Chemical\nProperties and Cocoyam yield under Different Tillage Systems in a\nTropical Alfisol\", Experimental Agriculture, 47(3):477-488.","F.N. Ikpe and J.M. Powel, \"Nutrient Cycling Practices and Changes in\nSoil Properties in the Crop Livestock Farming System of West Niger\nRepublic of West Africa\", Nutrient Cycling Agroecosystems, 62:37-45,\n2003.","A.O. Ano and J.A. Agwu, \"Effect of Animal Manure on Selected Soil\nChemical Properties (1)\", Nigerian Journal of Soil Science, 15:14-19,\n2005.","Li Lujiu, Chen Fang, Yao Dianli, Wang Jiajia, Ding Nan and Liu Xiyu,\n\"Balance Fertilization for Ginger Production – Why Potassium is\nimportant\", Better Crops, 94(1):25-27, 2010.","A.K. Sadanandan, K.V. Peter and S. Hamza, \"Role of Potassium\nNutrition in Improving Yield and Quality of Spice Crops in India\", In:\nN.S. Pasricha and S.K. Bansal, Eds., Potassium for Sustainable Crop\nProduction. Potash Research Institute of India, Gurgaon, Haryana and\nInternational Potash Institute, Switzerland, pp. 445-454, 2002.","N. Van Duivenbooden, C.T. de Wit and H. Van Keulen, \"Nitrogen,\nPhosphorus and Potassium Relations in Five Major Cereals Reviewed in\nRespect to Fertilizer Recommendations Using Simulation Modeling\",\nResearch, 44:37-49, 1996.","National Root Crops Research Institute (NRCRI) \"Annual Report\",\nUmudike, Nigeria, National Root Crops Research Institute, pp. 6, 1982.\n[10] National Root Crops Research Institute (NRCRI), \"Ginger Production\nExtension Bulletin\", National Root Crops Research Institute, Umudike,\nNigeria, 2005.\n[11] U. Omoti, C.R. Obatolu and J.A. Fagbenro, \"Complementary Use of\nOrganic and Inorganic Fertilizers for Tree and Forest Crops\", First\nNational Organic Fertilizer Seminar, Kaduna, March 26-28, FMA/NFC,\n1991.\n[12] M.A. Awodun, S.O. Ojeniyi, A. Adeboye and S.A. Odedina, \"Effect of\nOil Palm Bunch Refuse Ash on Soil and Plant Nutrient Composition and\nYield of Maize\", American- Eurasian Journal of Sustainable Agriculture,\n1(1):50-54, 2007.\n[13] A.O. Adekiya and T.M. Agbede, \"Growth and Yield of Tomato\n(Lycopersicon esculentum Mill) as Influenced by Poultry Manure and\nNPK Fertilizer\", Emirates Journal of Food and Agriculture, 21 (1):10-\n20, 2009.\n[14] T.M. Agbede and A.O. Adekiya, \"Effects of Poultry Manure on soil\nFertility, Growth and Yield of White Yam and Yellow Yam\", University\nof Khartoum Journal of Agricultural Sciences, 20(3):286-302, 2012.\n[15] United State Department of Agriculture (USDA), \"Soil Taxonomy\" 11th\ned. Agriculture Handbook, No.36. Washington DC, United States\nDepartment of Agriculture, Natural Resources Conservation Services,\n869 pp, 2010.\n[16] FAO, \"World Reference Base for Soil Resources. World Soil Resources\nReport 84, Food and Agriculture Organization of the United State,\nRome, Italy, 88 pp, 1998.\n[17] T.M. Agbede, and A.O. Adekiya, \"Tillage Effects on Soil Properties and\nPerformance of Sweet Potato on an Alfisol in southwestern Nigeria\",\nAmerican-Eurasian Journal of Sustainable Agriculture, 3(3):561-568.\n[18] M.E. Pansu and J. Gautheyron, \"Handbook of Soil Analysis.\nMineralogical Organic and Inorganic Methods. New York: Springer –\nVerlag, 993 pp, 2006.\n[19] D.W. Nelson and L.E. Sommers, \"Total Carbon, Organic Carbon and\nOrganic Matter. In: D.L. Sparks, Ed., Methods of Soil Analysis, Part 3.\nSecond ed; SSSA Book Series No. 5, SSSA, Madison, WI, USA, pp.\n961-1010, 1996.\n[20] J.M. Bremner, \"Nitrogen - total\", In: D.L. Ed., Methods of Soil\nAnalysis. Part 3. Chemical Methods. 2nd ed. SSSA Book Series No. 5,\nMadison, WI, ASA and SSSA, pp. 1085-1121, 1996.\n[21] K. Frank, D. Beegle, and J. Denning, \"Phosphorus\", In: J.R. Brown, Ed.\nRecommended Chemical Soil Test Procedure for the North Central\nRegion, North Central Regional Research Publication No. 221 (revised)\nMissouri Agric. Exp. Stn. Columbia, MO, pp. 21-29, 1998.\n[22] J.R. Okalebo, K.W. Gathua and P.L. Woomer, \"Laboratory Methods of\nSoil and Plant Analysis\", A Working Manual. 2nd ed. Nairobi, Kenya,\nTSBF - CIAT, SACRED Africa, KARI, Soil Science Society of East\nAfrica, 128 pp, 2002.\n[23] W. Horwitz, Editor, \"Official Methods of Analysis of the Association of\nOfficial Analytical Chemists International. 16th ed. Gaithersburg (MD):\nAOAC International, 1298 pp, 1997.\n[24] R.G.D. Steel, J.H. Torrie and D.A. Dickey, \"Principles and Procedures\nof Statistics. A Biometrical Approach. 3rd ed. New York: McGraw-\nHill, 869 pp, 1997.\n[25] S.O. Ojeniyi, B.E. Awanlemhen and S.A. Adejoro, \"Soil Plant Nutrient\nand Maize Performance as Influenced by Oil Palm Bunch Ash plus NPK\nFertilizer\", Journal of America Science, 6(12):456-460, 2010.\n[26] T.M. Agbede and S.O. Ojeniyi, \"Tillage and Poultry Manure Effects on\nSoil Fertility and Sorghum Yield in Southwestern Nigeria\", Soil Tillage\nResearch, 104:74-81, 2009.\n[27] S.O. Ojeniyi and F.O. Adekayode, \"Soil Conditions and Cowpea and\nMaize Yield Produced by Tillage Methods in the Rainforest Zone of\nNigeria\", Soil Tillage Research, 51:161-164, 1999.\n[28] T.M. Agbede, \"Nutrient Availability and Cocoyam Yield Under\nDifferent Tillage Practices\", Soil Tillage Research, 99:49-57, 2008.\n[29] J. Mueller-Harvey, A.S.R Juo and A. Wild, \"Soil Organic C, N, S, and P\nafter Forest Clearing in Nigeria: Mineralization Rate and Spatial\nVariability\", Journal of Soil Science, 36:585-591, 1985.\n[30] P.O. Ezekiel and S.O. Ojeniyi, D.O. Asawalam and A.O. Ano, \"Effect of\nOil Palm Bunch Ash on Soil NPK and Root Yield of Sweet and Bitter\nCassava\", Nigerian Journal of Soil Science, 19(1):1-5, 2009.\n[31] T.M. Agbede, A.O. Adekiya and J. S. Ogeh, \"Effects of Organic\nFertilizer on Yam Productivity and Some Soil Properties of a Nutrient-\nDepleted Tropical Alfisol\", Archives of Agronomy and Soil Science,\ndoi, org/10.1080/03650340.2012.683423.\n[32] G.O. Obigbesan, \"Fertilizer: Nigerian Farmers Dilemma\", Inaugural\nLecture University of Ibadan, Nigeria, 37 pp, 1999.\n[33] M.R. Villanueva, \"Technology for Yam and Taro Production in\nSoutheast Asia\", Radix, 8:1-6, 1986.\n[34] M.A. Arshad, B. Lowery and B. Grossman, \"Physical Test for\nMonitoring Soil Quality. In: J.W. Doran and A.J. Jones, Eds., Methods\nfor Assessing Soil Quality. Soil Science Society of America Special\nPublication No. 49, SSSA, Madison, 101:123-142, 2009."]}

Research study on the effect of tillage systems and application rate of poultry manure on sweet potato (Ipomoea batatas) in Alfisol of southwest Nigeria is lacking. Field trials were conducted in 2006, 2007 and 2008 cropping seasons on an Alfisol (Oxic Tropuldalf) at Owo in rainforest zone of southwest Nigeria. The trials consisted of the factorial combinations of two tillage methods (manual clearing and conventional tillage) and four manure levels (0, 5, 10 and 15 t/ha) arranged in a randomized complete block design and replicated three times. Conventional tillage alone (CTo) resulted in lower soil N, P, K, Ca, Mg and soil organic C and better leaf N, P, K, Ca and Mg concentrations, growth and yield of sweet potato compared with manually cleared (MCo) plots. The better performance of sweet potato under conventional tillage (CTo) was adduced to reduced bulk density. Bulk density was negatively correlated with yield. Conventional tillage alone (CTo) improves sweet potato tuber yield by 62, 55 and 42% in 2006, 2007 and 2008, respectively compared with manual clearing alone (MCo). In both the manually cleared and conventionally tilled plots, soil organic C, N, P, K, Ca, Mg and water content increased with amount of poultry manure, while soil pH, bulk density and temperature were reduced. Yields given by 5, 10 and 15 t/ha poultry manure were not significantly different under both manually cleared and conventionally tilled treatments. Conventional tillage plus 5 t/ha poultry manure (CT+5 PM) produced the highest overall yield. Compared with manual clearing alone (MCo) and conventional tillage alone (CTo), conventional tillage plus 5 t/ha poultry manure (CT+5 PM) improved tuber yield of sweet potato by 117 and 43%, respectively. Therefore the use of 5 t/ha poultry manure with conventional tillage is recommended for sweet potato production on an Alfisol of southwest Nigeria.

Four field trials were conducted during the years 2006 and 2007 at Owo, the forestsavannatransition zone in southwest Nigeria, to study the effect of poultry manure (PM), NPK 15-15-15 fertilizer and NPK 15-15-15 fertilizer + poultry manure on the growth and yield of tomato.Seven treatments were applied to the soil: 0, 10, 20, 30, 40 t ha-1poultry manure , 300 kg ha-1 NPK 15-15-15 fertilizer and 150 kg ha-1 NPK 15-15-15 fertilizer + 10 t ha-1poultry manure. These werelaid out in a randomized complete block design and replicated three times. The treatments werecompared on the basis of their effect on soil chemical properties, leaf nutrient content, growth andyield of tomato. All levels of poultry manure and NPK 15-15-15 fertilizer + poultry manureincreased leaf N, P, K, Ca and Mg levels. The soil chemical properties except pH increased withamount of poultry manure. NPK 15-15-15 fertilizer alone did not increase the soil and leaf Ca andMg. All levels of poultry manure, NPK 15-15-15 fertilizer alone and NPK 15-15-15 fertilizer +poultry manure increased the number of leaves, plant height, leaf area, number of fruits and fruitweight significantly. Among poultry manure levels, 30 t ha-1poultry manure gave the highest fruityield. Among the seven treatments, NPK 15-15-15 fertilizer + poultry manure gave the highestyield. On an average over the two years, 10, 20, 30, 40 t ha-1poultry manure, 300 kg ha-1 NPK 15-15-15 fertilizer alone and 150 kg ha-1 NPK 15-15-15 fertilizer + 10 t ha-1poultry manuretreatments increased fruit weight by 19, 36, 51, 14, 20 and 83%, respectively. Results revealed thatpoultry manure is a suitable source of nutrients for tomato especially if applied at 30 t ha-1in theforest-savanna transition zone of southwest Nigeria. The combined use of NPK 15-15-15 fertilizerand poultry manure increased tomato yield compared to the application of NPK 15-15-15 fertilizeror poultry manure alone and is therefore recommended for sustainable productivity. In addition,lesser quantities of poultry manure and NPK 15-15-15 fertilizer would be required, therefore,reducing the amount of money spent on chemical fertilizer

In order to obtain maximum economic value of plant nutrients in poultry manure and increase in tomato yield, field experiments were conducted at Owo, southwest Nigeria, during 2012 and 2013 early cropping seasons to study the effect of two methods (broadcasting on the soil surface and the incorporated) and four times (3 weeks before transplanting (3 WBTP), 0 week at transplanting (0 WATP), 3 weeks after transplanting (3 WATP), and 6 weeks after transplanting (6 WATP) of poultry manure (PM)) applications on soil chemical properties, leaf nutrient concentrations, growth and yield of tomato. The eight treatments were factorially arranged in a randomized block design with 3 replications. Results showed that PM incorporated into the soil produced higher soil organic matter and soil and leaf N, P, K, Ca, Mg, growth and yield (0.9 t ha −1 ) of tomato compared with broadcast method. Also PM applied at 3 WBTP had higher leaf nutrient concentrations and better growth and yield of tomato compared with 0 WATP, 3 WATP and 6 WATP. The higher yield of 3 WBTP was adduced to better synchrony between crop demand and nutrient supply. Using the mean of the two years, 3 WBTP increased tomato fruit yield by 4.0, 2.8 and 1.5 t ha −1 compared with 6 WATP, 3 WATP and 0 WATP, respectively. This yield difference can be economical on large scale tomato production. Therefore application of PM at 3 WBTP with incorporated method is recommended for tomato cultivation in the forest-savanna transition zone of southwest Nigeria.