INFLUENCE OF INTEGRATED SOIL FERTILITY MANAGEMENT ON THE VEGETATIVE GROWTH PARAMETERS OF ZEA MAYS IN THE GUINEA SAVANNA ECO-ZONE OF GHANA

: All over the world, attention has been drawn to the use of eco-friendly biochar application to improve crop productivity. In Ghana, there are available potential feedstocks left unused and can be used for the production of biochar. Therefore, this study investigated the effect of different rates of rice husk biochar and different rates of inorganic nitrogen (N) on the growth of Zea mays in Nyankpala, Northern Ghana. Field experiments were conducted in the cropping period of 2012. The treatments involved 4 different rates of inorganic nitrogen fertilizer (0 kg Nha -1 , 30 kg Nha -1 , 60 kg Nha -1 and 90 kg Nha -1 ) and 3 different rates of rice husk biochar (0 ton ha -1 , 2 ton ha -1 and 4 ton ha -1 ). The treatments were allocated in a split-plot design with three replications. The vegetative parameters assessed were the number of leaves, plant height and plant girth. Treatments showed a significant (p<0.05) influence on all the traits considered. The combined effects of inorganic nitrogen fertilizer and rice husk biochar significantly influenced the vegetative growth parameters of Zea mays with the maximum values recorded at 4 ton ha -1 rice husk biochar. Yet, this observation corresponds with 2 ton ha -1 rice husk biochar which recorded optimum growth parameters higher rates of rice husk biochar to ensure the appropriate rate of biochar application.


Introduction
Zea mays is the crop with the highest yields per hectare and the second largest commodity crop after cocoa in Ghana. The crop is high yielding and has diversified uses. About 70% of the total maize was produced by small-scale farmers. Average maize yields fluctuate between 1.2 metric ton ha -1 and 1.9 metric ton ha -1 , whereas on-station and on-farm trials suggest that yields averaging between 4 and 6 metric ton ha -1 of maize are attainable in the country. The maize supply in Ghana has been increasing steadily over the past few years with an average supply at 1.4 million metric ton over the period 2005-2010(Ragasa et al., 2014. However, human consumption is rising and competing with the poultry industry and to a lesser extent with the livestock industry. Consequently, the production of maize needs to be increased by adopting integrated soil fertility management practices. Lately, a rising consent has emerged on the need for the application of integrated soil fertility management practices to reverse the negative nutrient balances in cropping systems in agriculture in sub-Saharan Africa (SSA) (Vanlauwe et al., 2015). This know-how can improve soil health, keep land alive and sustain its productive capacity. Biochar is a pyrolyzed by-product of biomass produced at high temperatures (>400°C) with little or no available oxygen. According to international biochar initiatives (IBIs), it is persistently utilised for its agricultural and environmental advantages. It is fine-grained, carbon-rich and porous material which basically consists of nano-structured aromatic compounds systematically arranged like graphite (Sohi et al., 2010). Nearly any type of organic resources can be pyrolyzed into biochar including various types of forest residues (sawdust) (Xu et al., 2012), agricultural residues (corn cob, corn stalk, wheat straw, rice straw, stalk of pearl millet, cotton, mustard, soybean, and sugar beet tailing) (Jindo et al., 2014;Yu et al., 2014;Prabha et al., 2015), and agro-industrial waste (paper mill waste, Jatropha husk, coffee husk, coconut shell and cocoa pod husk) (Dume et al., 2015;Prabha et al., 2015;Munongo et al., 2017). The waning in soil productivity due to increased intensity with low fertilizer inputs has been recognised as one of the core causes of food insecurities in Ghana. To attain food sufficiency, there is an urgent need to manage hitches in soil infertility, advancing crop production in these soils that are essential for social and economic explanations. Applying inorganic fertilizers affords an alternative to overcome soil infertility. However, the sole application of inorganic fertilizers causes degradation of soil health and decreases its productive capacity. The application of organic sources reduces the reliance on expensive fertilizers that sustain and reduce nutrient losses and enhances biological N-fixation. When applied repetitively, soil organic matter accumulates, thus providing a capital of nutrients released slowly, increasing soil buffering capacity (balance between cations and anions), as well as capacity to hold up water (Sheahan and Barrette, 2014). The accumulation of nutrients and buffering capacity are slow processes and their potential benefits are likely to become visible in a long-standing case. The objective of the investigation was, however, to assess the effect of rice husk and inorganic nitrogen fertilizer on the maize growth parameters.

Site description
The field experiment was established throughout the 2012 cropping season at the experimental fields of Savannah Agriculture Research Institute (SARI), Nyankpala in the Northern region of Ghana. The site is located between latitude 9 o 25′ N and longitude 00 o 58′ W. The area has a rain forest belt with an average rainfall of about 1100 mm and a mean temperature range of 33 o C to 39 o C (SARI, 2016). The soil of the experimental site was sandy loam and slightly acidic (Table 1).

Biological materials
Seeds for this experiment were collected from a local variety of maize (Dorke SR). However, the rice husk was collected in Nyankpala in the northern region of Ghana. Rice husk biochar was obtained after pyrolysis at 500 o C using the drum type pyrolyzer (Gul et al., 2015).

Experimental design and treatment
The experiment was carried out in a split-plot design with 12 treatments, each of which was replicated 3 times. Treatments included the application of 0 ton ha -1 , 2 ton ha -1 and 4 ton ha -1 rice husk biochar and four levels of inorganic nitrogen fertilizer: 0 kg Nha -1 , 30 kg Nha -1 , 60 kg Nha -1 and 90 kgNha -1 . Soil preparing comprised a single ploughing and harrowing. The experimental area was 50 m x 50 m (2500 m 2 ) and was subdivided into 3 whole plots of 12.8 m x 12.8 m and each whole plot consisted of 4 sub-plots of 6.4 m x 6.4 m with a working path of 2.0 m in the whole plot and a working path of 1 m in the sub-plot. The biochar was mixed thoroughly with soil at a depth of 10 cm using a hoe (Venkateshet al., 2015) before planting whilst the basal application of triple superphosphate and muriate of potash was incorporated before planting to ensure a sufficient amount of essential nutrients in the soil. Nitrogen in the form of urea was split-applied: 1/3 at 1 week after planting and 2/3 weeks after planting (WAP). Four seeds were planted per seed-bed. Refilling was done 1 week after planting. Maize seedlings were thinned to 2 plants per seed-bed and a spacing distance of 80 cm x 40 cm with a plant population size of 62,500 plants ha -1 . Weeding was done 2 times within the cropping season; the first at 3 WAP and the second at 7 WAP (Table 2). Table 2. Details of treatment combination.

Treatment symbol
Treatment combination T 1 0 ton ha -1 Rice husk biochar + 0kg N ha -1 T 2 0 ton ha -1 Rice husk biochar + 30kg N ha -1 T 3 0 ton ha -1 Rice husk biochar + 60kg N ha -1 T 4 0 ton ha -1 Rice husk biochar + 90kg N ha -1 T 5 2 ton ha -1 Rice husk biochar + 0kg N ha -1 T 6 2 ton ha -1 Rice husk biochar + 30kg N ha -1 T 7 2 ton ha -1 Rice husk biochar + 6kg N ha -1 T 8 2 ton ha -1 Rice husk biochar + 90kg N ha -1 T 9 4 ton ha -1 Rice husk biochar + 0kg N ha -1 T 10 4 ton ha -1 Rice husk biochar + 30kg N ha -1 T 11 4 ton ha -1 Rice husk biochar + 60kg N ha -1 T 12 4 ton ha -1 Rice husk biochar + 90kg N ha -1 Soil sampling and analysis Initial soil samples were collected from thirty-six (36) plots at a depth of 0-15 cm with a soil auger. The samples were bulked together to form a composite sample. The soil samples collected were air-dried, gently crushed and passed through a 2-mm sieve and taken to the laboratory for physical and chemical analyses. Soil pH was measured in a 1:1 soil to water ratio (McLean, 1983). The Walkey and Black procedure was used to determine soil organic content (Walkey and Black, 1934). The nitrogen content was determined using the Kjeldahl digestion and distillation procedure. The cation exchange capacity was determined by the NH 4 OAc method. Calcium and magnesium (Mg) were determined by atomic absorption spectrophotometry while potassium (K) and sodium (Na) were determined by flame photometry.

Characteristics of the biochar
The biochar chemical analysis results presented in Table 3 show that biochar prepared from rice husk that was cultivated in slightly acidic soil also had slightly acidic properties at pH 6.5. The biochar had lower concentrations of Ca, Mg, and Na, however a higher content of ash and organic carbon. The pyrolysis of rice husk increases organic carbon in the materials. Rice husk biochar had ECEC of 13.67 m kg -1 .

Data collection
The data were collected every 2 weeks starting from 2 WAP and terminated at 10 WAP. Randomly, 5 maize plants were selected from individual sub-plots and labelled for measurements. Parameters assessed were the plant height measured from the base of the stem to the last leaf using a graduated ruler, number of leaves was determined by counting the leaves on plant and plant girth was measured at the soil level using a slide calliper.

Data analysis
Effects of different treatments were analysed by analysis of variance. The least significant difference (LSD) test was applied to distinguish the treatment differences (p<0.05) using the statistical software GenStat 18 th edition.

Plant height
There was a general increase in plant height starting from 2 WAP to the end of the experiment (8 WAP) for all the treatment levels (Table 4). Mean differences in height among treatments were significant (p<0.05) at the end of the experiment. The highest mean plant height (32.34 cm) was recorded at T 12 whilst the lowest mean plant height (10.74 cm) was recorded at T 1 . Similar trends were observed at 4, 6 and 8 WAP where mean plant height of maize was significantly higher with the combination of rice husk biochar and inorganic nitrogen fertilizer . The highest mean heights were observed at T 12 , T 11, T 10 , T 9 , T 8, T 7 , T 6 , T 5 from 2 WAP to the end of the experiment at 8 WAP (Table 4). The significant increase in the plant height of maize could be ascribed to the fact that the added rice husk biochar (58.2%) increased the supply and availability of plant nutrients in the soil. This approves the recommendation that higher accessibility of nutrients increases the vegetative growth of plants (Zoghi et al., 2019).

Plant girth
The effect of rice husk biochar on maize girth at different weeks after planting is described in Table 5. It was clear that rice husk biochar and inorganic nitrogen Influence of integrated soil fertility management on the vegetative growth of Zea mays 193 fertilizer had a significant effect on the plant girth. At 2 WAP, the highest plant girth was recorded in the treatment T 12 while the lowest was recorded at T 1. This trend was, however, similar in all phases. It is clear that there is a noticeable difference in plant girth with the highest rate of rice husk biochar treatments compared to 0 ton ha -1 biochar treatments. A comparable result was found by Varela et al. (2013) who stated that an increase in the application of both wood and rice husk biochar improved the stem size of Ipomoea aquatica. They, furthermore, stated that the decomposition of wood and rice husk biochar improved the organic matter content in the soil leading to increase in water holding capacity of soil, thus improving stem diameter.

The number of leaves
Observations made on the number of leaves produced by Zea mays showed an increase from week 2 to week 8 (Table 6). By week 2, mean differences among treatments had already been significant (p<0.05), with T 12 , T 11, T 10 , T 9 , T 8, T 7 ,T 6 and T 5 producing more leaves relative to the treatments in T 1 (Table 6). These differences were still significant (p<0.05) by the end of the experiment. Similar trends were, however, observed from 4 WAP to the end of the experiment at 8 WAP.
Plants that received the highest rate of rice husk biochar and inorganic nitrogen fertilizer recorded a greater number of leaves than T 1 . The application of biochar improved the fertility of the soil and safeguarded the availability of vital nutrients that boosted the vegetative growth of maize. Our findings corroborate with the findings of Ali et al. (2017). 6.56ff 10.83vy 11.89rt 13.00nn T 10 6.57ff 11.02bb 12.34pq 13.56ww T 11 6.75wr 11.48hi 12.75mn 13.86uy T 12 6.95qs 11.93xy 12.92am 14.03zx CV% 0.8 1.6 5.6 5.2 Means with the different letter(s) in a column are significantly different at the 5% level of probability.

Conclusion
The highest vegetative growth parameters were obtained at 4 ton/ha of biochar and inorganic nitrogen fertilizer which were effective at 90 kg N ha -1 and 60 kg N ha -1 . It was, therefore, concluded that the combination of various sources of inorganic and organic nutrients improved the performance of growth parameters of Zea mays rather than the sole use of either the inorganic fertilizers or the organic sources.