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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.

The nutrients requirement for Cucurbita pepo L. (summer squash) for optimal yield and quality fruits production can be achieved through adequate nutrient supply. A field experiment was carried out during the cropping season of 2015 and 2016 at Landmark University Teaching and Research Farm, Omu-Aran, Nigeria to investigate the impact of Tithonia diversifolia, poultry manure and NPK fertilizer on the growth, yield, mineral and vitamin C content in the fruit of C. pepo. The experiment consisted of T. diversifolia at 30 tons ha−1, poultry manure at 10 tons ha−1, T. diversifolia at 30 tons ha−1 + Poultry manure 10 tons ha−1, T. diversifolia at 30 tons ha−1 + NPK (20:10:10), NPK (20:10:10) and control (no amendment of any kind) arranged in a randomized complete block design with four replications. The growth and fruit yield of C. pepo using the mean of the two years was increased by 68% and 2% respectively by T. diversifolia + poultry manure as compared to control due to an increase in nutrient availability in the soil with the amendment used. Also, Vitamin C content and Mg value of the fruit was increased by application of T. diversifolia as soil amendments as compared to the control. While the application of NPK fertilizer alone significantly increased the Ca, Mn and Fe contents of fruits. Fruit content of K was increased by 39 % by the application of T. diversifolia + NPK. Therefore, for the purpose of growing squash for the quality of fruits (vitamin C), the use of T. diversifolia at 30 tons ha−1 as organic fertilizer is sufficient for the cultivation, while for growing the crop with interest in quantity, application of T. diversifolia at 30 tons ha−1 + poultry manure at 10 tons ha−1 is recommended.

Field experiments were conducted during 2016 and 2017 cropping seasons in the derived agro-ecological zone of Nigeria to study the combined and sole effect of zinc and boron fertilizers on the growth, seed yield, and quality of groundnut (Arachis hypogaea L). The experiment was laid out in randomized complete block design (RCBD), replicated four times. Three levels of zinc (0, 4, and 8 kg·ha−1) and four levels of boron (0, 300, 600, and 900 ml·ha−1) were combined and evaluated. Groundnut seeds were analyzed at the end of the experiments to determine nutrient elements and some heavy metal contents. Data collected were subjected to Statistical Analysis of Variance using SAS 2000. Treatment means were compared using the Duncan multiple range test at 0.05 level of probability. The effect of zinc was not significant on the vegetative parameters, while application 8 kg Zn·ha−1 significantly increased number of seeds, weight of seeds, seed yield per hectare, and seed quality though the values were similar to the application of 4 kg Zn·ha−1 only on the seed yield and its parameters. Application of 600 and 900 ml B·ha−1 gave higher and statistically similar values for vegetative parameters, yield, and yield parameters, while 600 ml B·ha−1 significantly improved the seed quality. It can therefore be recommended that for optimum yield and seed quality, application of 8 kg Zn·ha−1 combined 600 ml B·ha−1 is sufficient in the study area without increasing the heavy metal concentration of groundnut seed.

Background:The optimum rate of nutrient must be defined with reference to soil properties for individual crops and soil.Objective:Field experiments were carried out in 2015 and 2016 cropping seasons to determine the various levels (0, 40, 80, 120 and 160 kg ha-1) of potassium fertilizer (muriate of potash , KCl), on soil chemical properties, leaf nutrient contents, performance and proximate quality of sweet potatoes (Ipomoea batatasL.).Method:The five treatments were arranged in a randomized complete block design with three replicates.Results:Studies showed that K fertilizer in both the years significantly influenced N, P and K concentrations compared with the control and also increased the soil concentrations of these nutrients from 0 - 160 kg ha-1K fertilizer. However, soil K only increased up to 80 kg ha-1fertilizer after which there was a decrease. There was a reduction in the values of Ca and Mg in the soil as the levels of K increased. Leaf nutrient concentration of the sweet potato was consistent with the values of soil chemical properties recorded. 80 kg ha-1K fertilizer was observed to be the highest value of sweet potato growth and tuber yield after which there was a reduction. The yield decrease was adduced to excessive K application leading to imbalanced sweet potato plant nutrition compared with N, P, Ca and Mg. K fertilizer significantly influenced moisture, vitamin C and carbohydrate compared with the control. The highest values of fibre and protein were obtained at 80 and 40 kg ha-1K fertilizer, respectively. Dry matter and fat contents of the sweet potato reduced by K application from 0 - 160 kg ha-1application rate.Conclusion:For best tuber yield, quality and economic response of K fertilizer to the sweet potato in the agro-ecological zone or in other similar soil conditions elsewhere in the tropics could be achieved by applying 80 kg ha-1K fertilizer.

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

Field experiments were carried out in 2018 and 2019 cropping seasons at Landmark University Teaching and Research farm, Omu-Aran Kwara state, Nigeria, to determine the effect of soil applied Zn-fertilizer, Tithonia diversifolia (Ti), Chromolaena odorata (Ch) and poultry manure (PM) on the performance, yield, minerals and vitamins composition of okra fruits. Treatments were combined and tested as follows:—Control (T1), Control + 10 kg ha−1 Zn (T2), 5 t ha−1 Ti + 5 t ha−1 PM (T3), 5 t ha−1 Ch + 5 t ha−1 PM (T4), 5 t ha−1 Ch + 5 t ha−1 Ti (T5), 10 t ha−1 Ti + 0 kg ha−1 Zn (T6), 10 t ha−1 Ti + 10 kg ha−1 Zn (T7), 10 t ha−1 Ch + 0 kg ha−1 Zn (T8), 10 t ha−1 Ch + 10 kg ha−1 Zn (T9), 10 t ha−1 PM + 0 kg ha−1 Zn (T10), and 10 t ha−1 PM + 10 kg ha−1 Zn (T11). The experiment was laid out in a randomized complete block design with four repetitions. Vegetative, yield and quality parameters of okra were taken. Data were subjected to analysis of variance and means were compared using Duncan Multiple Range Test (DMRT) at p ≤ 0.05. Variations were observed on the vegetative parameters, yield, minerals and vitamin composition of okra among the applied amendments. The combined application of green biomass, poultry manure, and Zn-fertilizer improved all the variables tested as compared to when they were applied singly. Application of Zn-fertilizer to some selected plots significantly increased yield, Zn, Mg and vitamins concentration of okra. Application of 5 t ha−1 Ti + 5 t ha−1 PM + 10 kg ha−1 Zn (T3) and 5 t ha−1 Ch + 5 t ha−1 PM + 10 kg ha−1 Zn (T4) significantly improved all the parameters tested but the use of 5 t ha−1 Ti + 5 t ha−1 PM + 10 kg ha−1 Zn (T3) resulted in optimum yield and at the same time increase minerals and vitamin concentration of okra. The results of this study therefore showed that Tithonia diversifolia (Ti) as green biomass contained and released more and quality nutrients than Chromolaena odorata (Ch) when combined with equal rate of Zn fertilizer and poultry manure.

Micro-nutrients especially zinc can not only increase the yield of sweet potato but can also improve the quality of tubers. Hence, experiments were carried out in 2015 and 2016 cropping seasons to determine the impact of various levels of ZnSO4 fertilizer on soil chemical properties, foliage and storage root yields and proximate qualities of sweet potato (Ipomoea batatas L.). The experiments consisted of 5 levels (0, 5, 10, 15 and 20 kg ha-1) of ZnSO4 fertilizer. These were arranged in a randomized complete block design and replicated three times. ZnSO4 increased (with the exception of P) soil chemical properties compared with the control. N, K, Ca, Mg and Zn were increased up to the 20 kg ha-1 ZnSO4 level in both years. ZnSO4 reduced P concentrations in soil as the level increased. For sweet potato performance, 5 kg ha-1 ZnSO4 fertilizer had the highest values of foliage yield (vine length and vine weight) and storage root yield. Using the mean of the two years and compared with the control, ZnSO4 fertilizer at 5 kg ha-1 increased storage root yield of sweet potato by 17.4%. On fitting the mean storage root yield data of the two years with a cubic equation, the optimum rate of Zn for sweet potato was found to be 3.9 kg ha-1 to achieve the maximum sweet potato yield. In this study, relative to the control, ZnSO4 fertilizer increased moisture and decreased the fibre contents of sweet potato. There were no consistent patterns of variation between the 5, 10, 15 and 20 kg ha-1 ZnSO4 treatments for proximate qualities except that the highest values of fat, protein, carbohydrate and ash was at 5 kg ha-1 ZnSO4.

Field experiments were carried out at the Teaching and Research Farm, Landmark University, Omu-Aran, Kwara State, Nigeria, in the cropping seasons of 2015 and 2016. The soil at the site of the experiment is an Alfisol classified as an Oxichaplustalf or a Luvisol. The trial consisted of sole and combined applications of urea fertilizer (U) applied at 0, 60, and 120 kg·ha−1 and maize cob ash (M) applied at 0, 3, and 6 t·ha−1. The results showed that U and M alone or in combinations increased the soil chemical properties, growth, yield, and mineral composition of okra compared with the control. M alone at 3 t·ha−1 produced optimum soil chemical properties, yield, and mineral composition of okra fruit. U alone at 60 kg·ha−1 produced optimum yield of okra, while growth and mineral composition were increased when urea fertilizer was applied at 120 kg·ha−1. The treatment with U applied at 60 kg·ha−1 in combination with M applied at 3 t·ha−1 (U60M3) produced the highest values of okra yield, while U applied at 120 kg·ha−1 in combination with M applied at 3 t·ha−1 (U120M3) has the highest growth and highest N, K, Ca, Cu, and Fe contents of okra fruit. Compared with the control and using the mean of the two years, U60M3 increased okra fruit yield by 93.3%. Therefore, for viable production of okra in low nutrient soil of the Nigeria derived savanna or similar soils elsewhere, 60 kg·ha−1 U + 3 t·ha−1 M (U60M3) is recommended. However, for improved mineral quality of okra, 120 kg·ha−1 U + 3 t·ha−1 M (U120M3) is recommended.

Purpose: Soils of the experimental area are low in vital nutrients such as nitrogen. Fallow is no longer possible because of increasing pressure on arable land. The limited available chemical fertilizers must be inevitably and judiciously used for optimum yield. The study was carried out to assess the response of sweet sorghum varieties to varying nitrogen fertilizer (N) rates.Research Method: Sweet sorghum varieties (NTJ-2, 64 DTN, SW Makarfi 2006 and SW Dansadau 2007) were alloted to the main plots and nitrogen fertilizer (0, 40, 80, 120 and 160 kg N ha-1) to the sub-plots of a split-plot design, in three replicates. Data on growth and yield characteristics were collected and analysed.Findings: Variations were observed among the four varieties of sweet sorghum; SW Dansadau 2007 had greater growth and yield characteristics. N fertilizer had positive effects on the growth characteristics and ethanol yield of the crop. 80 kg N ha-1 resulted in increase of most parameters and ethanol yield, beyond which there was either no significant difference or a drop in the values of these parameters. Thus the use of 80 kg N ha-1 would result in optimum yield of sweet sorghum in the study area.Limitations: The requirement of 80 kg N ha-1 may not be generalized for the entire southern guinea savanna agro-ecological of Nigeria as the study was carried out only in one location.Originality/Value: These findings would assist farmers in the study area identify the most promising sweet sorghum variety and the optimum fertilizer rate for its production.

The study was conducted to determine the effect of green biomass of Parkia biglobosa and Tithonia diversifolia on growth, yield and vitamin C content of radish (Raphnus sativus L.). The potential of T. diversifolia as green manure has been discovered by a number of researchers while there is paucity of information and research work on the potentials of P. biglobosa in supplying crop nutrients despite the numerous nutrient compositions contained in the leaves. Both P. biglobosa and T. diversifolia are capable of providing adequate biomass for crop growth and sustainability. The contribution of 10 tonnes ha−1 tithonia to the growth and yield of radish was comparable to that of NPK while the potentials of parkia at all rates was not fully expressed in the growth and yield due to its slow mineralisation. Combination of varying levels of P. biglobosa and T. diversifolia also contributed to the growth and yield of radish though the effects were not significant. It can therefore be concluded that the use of T. diversifolia at 10 tonnes ha−1 as organic manure is sufficient for the cultivation of radish as it performed similar to application of 200 kg ha−1 NPK fertilizer and based on the fact that it is readily available and eco-friendly compared to NPK that is costly and may have adverse effect on the environment.

Field experiments were carried out during the 2016 and 2017 cropping seasons at the Teaching and Research Farm, Landmark University, Omu-Aran, Kwara State (latitude 8.9°N and longitude 50°61 E.), Nigeria, to study the effect of some green manures as an alternative to inorganic fertilizer on growth, yield, mineral and proximate composition of radish. Green manure composed of leaves of Vernonia amygdalina and Chromolaena odorata and were applied as follows: 10 tonnes ha−1 vernonia + 0 tonnes ha−1 chromolaena (T1), 7.5 tonnes ha−1 vernonia + 2.5 tonnes ha−1 chromolaena (T2), 5.0 tonnes ha−1 vernonia + 5.0 tonnes ha−1 chromolaena (T3), 2.5 tonnes ha−1 Vernonia + 7.5 tonnes ha−1 chromolaena (T4), 0 tonnes ha−1 vernonia + 10 tonnes ha−1 chromolaena (T5) while in-organic fertilizer (NPK 20:10:10) was applied at 200 kg NPK ha−1 (T6) and there was a control plot (T7). The experiment was laid out in a Randomized Complete Block Design (RCBD) replicated four times. Vegetative, yield and quality parameters of radish were taken. Data collected were subjected to Analysis of Variance (ANOVA) using Statistical Analysis Software (S.A.S), 2000. Treatment means were compared using Duncan Multiple Range Test (DMRT) at 0.05 level of probability. The study showed that application of green manures increased vegetative, yield and yield parameters and were comparable with application of NPK fertilizer while there was a significant increase in the nutritional composition of radish with application of green manures when compared with NPK and control. It can therefore be concluded that application 10 tonnes ha−1 vernonia + 0 tonnes ha−1 chromolaena (T1) as green manure increased vegetative, yield and yield parameters while application 7.5 tonnes ha−1 vernonia + 2.5 tonnes ha−1 chromolaena (T2) improved radish quality.

A field experiment was conducted at the Teaching and Research Farms of Landmark University Omu-Aran, Kwara State of Nigeria, for comparative evaluation of inorganic fertilizer with sole and integrated forms of cocoa pod ash (CPA) and cocoa pod husk powder (CPHP) on soil chemical properties, growth and yield of cucumber in Southern Guinea Savannah Zone of Nigeria. The treatments used for the experiment were control, NPK 20:10:10 (200 kg/ha), 100 % CPA (10 t/ha), 100 % CPHP (10 t/ha), 100 % CPA (10 t/ha) + 100 % CPHP (10 t/ha), 100 % CPA (10 t/ha) + 50 % CPHP (5 t/ha), 50 % CPA + 100% CPHP, and 50 % CPA + 50 % CPHP. At two weeks after planting NPK 20:10:10 was applied to the assigned plots at the rate of 200 kg/ha. Treatments were arranged in Randomised Complete Block Design (RCBD), replicated three times. Data collected were subjected to analysis of variance using SPSS procedure while DMRT at 5% level of probability was used to separate the means. Results showed that treatment with 10 t/ha CPA + 10 t/ha CPHP increased soil chemical properties compared to control. Treatments with 100% CPA + 100% CPHP and 100% CPA + 50% CPHP gave significantly higher and similar values of plant height, number of leaves, number of lateral branches and other yield parameters (fruit number, fruit length, fruit girth, fruit weight and total yield) of cucumber compared to the control. Therefore, the application of 10 t/ha CPA + 5 t/ha CPHP was considered best for growing cucumber in the study area. These cocoa wastes are readily available and eco-friendly compared to NPK that is costly and which may have adverse effect on the environment. Keywords: cocoa pod ash, cocoa pod husk powder, cucumber, soil chemical properties, growth and yield