Response of Mansonia altissima (A. chev.) seedlings to different levels of organic and inorganic fertilizers at nursery stage

INTRODUCTION

Forestry is an important component in the development of any nation. The utilization of forest resources is enormous range from the provision of raw materials to the ever increasing industry for human consumption to production of poles and firewood for domestic usage as well as climate regulation and watershed management.[1] The protection of arable land from degradation and desertification encroachment as well as attendant restoration and recreational stride formed interesting roles of forest. Increase in population and attendant increase in demand for forest and forest products have made plantation forestry attractive in the tropics.

According to FAO (2016),[2] Nigeria is one of the countries with the highest rate of deforestation in the world. It was reported that between 2000 and 2005 the country lost 55.7% of its primary forests at the rate of forest change increased by 31.2% per annum. Although, the continuous degradation of sparse vegetation is as a result of the combination of anthropogenic and natural factors such as windstorm, forest fire, and desertification, among others. Sadly, the activities of illegal and over exploitation of the forest products have resulted to several species extinctions.

Some forest plant species such as Tetrapleura tetraptera (Schumach. and Thonn) Taub, Mansonia altissima A. chev, Dennettia tripetala (Baker F.), Xylopia aethiopica (Dunal A. Rich. y, Irvingia gabonensis (Aubry-Lecomte ex O-Rorke), and Pentaclethra macrophylla (Benth.) have been affected adversely. These species are disappearing at alarming rate. Although, some of these forest plants species can be regenerated by coppicing; seedlings and growing in their natural habitat (in situ) or by transplanting to a suitable place (ex situ) where they can be established.[3] However, most of them are collected from the wild as farmers have not yet integrated them fully into the various traditional farming systems.[2] Although, nursery stocks are one of the major determinants of any plantation establishment successes. Consequently, improving the fertility of nursery soils is essential to guarantee the production of high quality seedlings for plantation establishment.[4]

M. altissima (A. Chev) is the focus of this study which is natively known as “Ofun” in yoruba and it is a tree species in the family Malvaceae of flowering plant. It is a semi-deciduous forest species that grows up to 37 m high with trunk of about 2.5 m girth.[5] It is of the dense semi-deciduous forest in zones with high rainfall up to 1600 mm annually and a pronounced dry season. The southern limit of its distribution area largely corresponds with the transition of semi-deciduous forest to evergreen forest; to the north its distribution extends to patches of dense forest in the savannah. Seedlings are most common on fertile soils on drier sites; they are fairly drought resistant.

The wood (trade names: Mansonia, bété, African black walnut, and pruno) is used for general and high-class joinery, cabinet work, furniture, turnery, decorative veneer, and handicrafts. It is also used in construction for doors and windows, in railway coaches and shop fittings, and for boxes and crates.

In addition, M. altissima (A. Chev) is likely to remain valuable for furniture and decoration, for which there is a stable market and growing demand. Because reliable statistics on production are lacking, it is not possible to estimate the amounts of its timber that can be extracted sustainably. Because of its high value, it is recommended to test and includes M. altissima (A. Chev) in plantation establishment and enrichment programs as well as in agroforestry practices.

M. altissima has been described as vulnerable according to the IUCN Red list of threatened species;[6] it therefore requires urgent conservation attention. Researchers over the years have exploited various means of determining the best growth medium that will support its early growth and eventual plantation establishment but with little or no direction. Conversely, necessitate this study with objective to assess the effect of organic and inorganic fertilizer on early growth of M. altissima (A. Chev) seedlings in the nursery.

METHODS

Forest soil samples were collected from arable areas of the university campus at 0–15 cm depth. The soil samples were bulked, mixed properly to ensure uniformity and sieved to remove large particles, roots, and debris. Cow dungs were collected from the cattle ranch Teaching and Research Farm of the University dried for 8 days and ground into powdery form. Samples of both the soil and cow dung were quarter sized and taken to Forestry and Wood Technology Department Wet Laboratory, Federal University of Technology Akure for soil physicochemical and chemical properties analysis, respectively, using conventional methods for soil analysis as described by Udo (2001).[8]

Two kilograms of topsoil were weighed using mechanical weighing balance and mixed with the organic fertilizer after adequate measurement according to the different levels, then filled into polythene pots of 15 cm × 20 cm. After 2 weeks of adding organic fertilizer, the inorganic fertilizer was weighed using (Analytical Electronic Balance [FA-2104]) and poured inside small sample bottles containing distilled water to dissolve into solution and then added to the soil according to the ratio and levels specified for the study [Table 1]. The organic and inorganic fertilizers were measured using sensitive weighing scale (Analytical Electronic Balance [FA-2104]). The seedlings of M. altissima were pricked from the nursery bed into the polythene pots containing the treatments very early in the morning and allowed to stabilize for 2 weeks before data collection. The different soil media were watered daily in the morning except when there is rainfall. Data on seedling height (cm), collar diameter (mm), leaf area (cm²), and leaf number were recorded at 2 weeks interval from the study. Furthermore, at the completion of the experiment, seedlings from different treatments were selected randomly for biomass assessment, harvested, weighed, and oven dried at 105°C until a constant weight is obtained. Nine treatments were used for this experiment and it was completely randomized with three replicate [Table 2].

Table 1: Level of nutrient applied

Table 2: Treatments and replicates

RESULTS AND DISCUSSION

Effect of Treatments on Seedlings Height

Table 3 presents the results of the effect of the different fertilizer treatments on the early growth height performance of M. altissima seedlings over a period of 8 weeks. From the table, it was observed that seedlings administered with the C₁U₂ (5 g of cow dung and 0.2 g of urea) treatment recorded the highest mean seedling height of 21.18 ± 0.25 cm, followed by C₁U₁ (5 g of cow dung and 0.13 g of urea) with 20.05 ± 2.17 while seedlings administered with C₀U₂ (i.e., 0.2 g of urea only) recorded the least growth with respect to the seedling height, with its highest mean of 16.47 ± 1.54 cm recorded for the 8^th week.

Table 3: Effect of different fertilizer treatments on height and leaf area of Mansonia altissima seedlings in the nursery

Effect on Number of Leaves

From Table 4, it was observed that seedlings administered with the C₀U₁ (0.13 g of urea) treatment recorded the highest mean number of leaves of 6.33 ± 0.58, followed by C₁U₀ (5 g of cow dung) with 6.00 ± 0.00 while the control seedlings (i.e., C₀U₀) recorded the least growth in number of leaves observed for the experiment.

Table 4: Effect of different fertilizer treatments on leaf number and collar diameter of Mansonia altissima seedlings in the nursery

ANOVA for the Effect of Different Fertilizer Treatments on Growth Variables of M. altissima

Table 5 present results for the analysis of variance; there are significant differences among the treatment for seedling height and leaf area but there were no significant differences in the treatment for both leaf number and collar diameter at 0.05 level of significant.

Table 5: Analysis of variance for the effect of different fertilizer treatments on growth variables of Mansonia altissima

Effect of Different Fertilizer Treatments on Biomass Accumulation

Table 6 presents the results for effect fertilizer treatment on the biomass (leaves, shoot, and root) of M. altissima seedlings. From the table, it was observed that seedlings administered with the C₀U₂ (0.2 g of urea) treatment recorded the highest mean weight of 0.45 ± 0.25 g, while the C₁U₂ (5 g of cow dung and 0.2 g of urea) and the control recorded the least mean weight of (0.09 ± 0.01 g) of leaves.

Table 6: Effect of different fertilizer treatments on Biomass Accumulation of Mansonia altissima seedlings

From the table, it was observed that seedlings administered with the C₀U₁ (0.13 g of urea) treatment recorded the highest mean weight of 1.13 ± 0.06g, while the C₂U₁ (10 g of cow dung and 0.13 g of urea) recorded the least mean weight of 0.53 ± 0.05 g.

From the table, it was observed that seedlings administered with the C₁U₂ (5 g of cow dung and 0.2 g of urea) treatment recorded the highest mean weight of 1.48 ± 0.22 g while the C1U0 (5g of cow dung) recorded the least mean weight of 0.2 ± 0.08 g.

ANOVA for the Effect of Different Fertilizer Treatments on the Biomass of M. altissima Seedlings

Table 7 presents the analysis of variance results of the effect of the various fertilizer treatments on the dry biomass of M. altissima seedlings after 8 weeks of planting. From the table, it was observed that treatments were significantly different for dry leaves (P < 0.05) with F_{(8, 96)} = 5.336 and P = 0.002. It was also observed that with respect to the treatment for dry shoot, there is no significant difference (P < 0.05) between the various fertilizer treatments with F_{(8, 96)} = 0.704 and P = 0.685 and there exist significant differences between the treatments for dry shoot (P < 0.05) with F_{(8, 96)} = 15.292 and P = 0.000.

Table 7: Analysis of variance for the effect of different fertilizer treatments on the biomass of Mansonia altissima seedlings after 8 weeks of planting

DISCUSSION

Morphological characteristics are the tangible or visually determinable features of a tree seedling.[9] There are different morphological criteria used to grade seedling quality in the nursery which include; shoot height, collar diameter, leaf area, leaf number, and seedling biomass.[10]

The result of this study revealed that the highest leaf number was obtained from M. altissima seedling treated with urea (6.33 ± 0.58) and this is consistent with Andrew et al. (2019)[11] who studied the response of four species of tropical timber seedlings to urea and Folivert fertilizers in nursery where it was revealed that plants treated with 3 g of urea produced the highest number of leaves in Albizia zygia seedlings. Again, according to Afa et al. (2011)[9] there are positive effects of organic and inorganic fertilizers on early growth characteristics of Khaya ivorensis seedlings treated with urea in nursery.

The findings of this fertilizer experiment showed that when there is adequate fertilizer application to seedlings the yield is always better. This is also in conformity with reports on plantation trees such as Michelia champaca Linn, Tectona grandis (Teak), and Entandrophragma cylindricum Sprague.[4,12]

CONCLUSION AND RECOMMENDATIONS

The result of this study showed that the combination of organic and inorganic fertilizer at different quantities and levels has positive effect on the growth performance M. altissima seedlings at the nursery stage. The results of this fertilizer study conform to the generally accepted response, where application of fertilizers yielded better growth and seedlings quality.

The highest mean seedling height, leaf number, collar diameter as well as all growth variables assessed were recorded from urea application to the seedling of M. altissima. The combination of organic and inorganic fertilizers should be encouraged especially with urea for M. altissima.