Effects of chemical and bio-fertilizers on yield, yield components and grain quality of maize (Zea mays L.)

A field experiment was conducted in two consecutive seasons (2009 and 2010) to assess the effect of two microbial fertilizers, chicken manure, urea and their possible combinations on the performance of a maize variety (Hudeiba 45). The bio fertilizers used were Azospirillum brasilense (A), Azotobacter sp (B) and chicken manure (CM) at a rate of 7t/ha). Urea (46% N) was applied at rates of 120kg/ha (N) and 40kg/ha (T). The combinations used were Azospirillum brasilense with urea (A+T), Azotobacter sp with urea (B+T), A+CM and B+CM in addition to control. The field experiment was laid out in a Randomized Complete Block Design with four replicates. Four seeds were sown in holes with 20 cm between holes in 4×4 m 2 plots with 5 ridges 70 cm apart. Sowing was carried out in the last week of October in 2009 and the first week of November in 2010. The fertilizers were applied on one side of the ridge and plants were irrigated at seven days intervals. Data were collected on cob length, cob diameter, number of rows/cob, number of seeds/row, 100-grain weight, grain yield/plant and grain yield/ha. Data were collected for yield components at physiological maturity and for grain yield after harvesting. The moisture, ash, fat, crude fiber, crude protein, tannins and carbohydrates contents of the grains were determined. Results showed that biofertilizers have significantly (p < 0.05) increased crop productivity. CM increased the grain yield (t/h) by 20 and 30% over the control in 2009 and 2010, respectively. Application of chicken manure solely or in combinations with Azosprillum barasilence or Azotobacter sp have also increased grain yield and its components. The combinations of N2 fixer inoculants with manure and/or urea improved grain quality of maize under field conditions.


INTRODUCTION
Maize (Zea mays L.) or corn is a cereal crop that grown over a wide environmental range .It is considered as a multi-purpose crops that have a lot of uses such as human diet and animal and poultry feed.It can be used as grain, green fodder or silage (Haque, 2003).In developing countries including Sudan maize is a major source of income to many farmers (Tagne et al., 2008).Moreover, the possibility of blending maize with wheat for *Corresponding author.E-mail: somasirmo@gmail.com.Tel: + 249-912765151.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License bread making has also increased the demand of maize in Sudan (Ali et al., 2009).Therefore, farmers are encouraged to incorporate the crop into the farming systems under both irrigated and rain fed agriculture.Nitrogen (N) is generally deficient in Sudan's soils as in most other semi-arid regions.In such regions nitrogen is usually added to the soil in large quantities.Therefore, intensive farming practices that aim at producing higher yield require extensive use of nitrogen fertilization which are costly and create environmental pollutions (Baser et al., 2012).Biofertilizers which are eco-friendly play an important role for supplementing the essential plant nutrients for sustainable agriculture and economy (Mugilan et al., 2011).Moreover, microbial fertilizers can clean the environment, enhance the productive capacity of land and reducing the amount of chemical fertilizer consumption (Hossein and Farshad, 2013) and improve plant growth and health (Raaijmakers et al., 2002).Enhancement of cereals yields by inoculation with nonsymbiotic nitrogen fixing bacteria was recorded by many researchers (Salantur et al., 2006).Azospirillum species have been potentially studied to the greatest extent and appeared to have significant potential for commercial production (Kumaresan and Reetha, 2011).Azotobacter species besides playing a role in nitrogen fixation, it has the capacity to synthesize and secrete considerable amounts of biological active substances like vitamins, gibberellins and auxins (Suhag, 2016).Chicken manure is an excellent source of nutrients and can be incorporated into most of the fertilization programs.Ayeni and Adetunji (2010) reported that, the mean increase in grain yield of maize due to application of poultry manure alone varied between 34 and 68% compared to 11-57% gained by application of NPK fertilizers.Corn is considered as one of the most important cereal crops over the world that needs large quantities of chemicals.In Sudan few reports on the importance of biofertilizers inoculation in increasing maize production and improving the physical and chemical quality of maize grains are available.Therefore, the objective of this study is to estimate the effects of microbial inoculation, chicken manure and urea fertilization on maize grain yield, components and quality.

Site
The field experiment was conducted at the experimental farm of the college of Agricultural Studies, Sudan University of Science and Technology, Shambat (Latitudes 15° 40´ N, Longitude 32° 32´ E and 380 m above the sea level) for two consecutive years (2009 and 2010).Shambat climate is tropical, usually hot and humid in summer and cold and dry in winter.The temperature reached a maximum value (45.9°C) in June and a minimum value (22°C) in January.The temperature usually drops during July to October due to the incidence of the rainy season.The soil of Shambat was analyzed to determine the physical and chemical characteristics according to Richard (1954).Nitrogen was measured using Kjeldahl method as described by Anderson and Ingram (1993).Data are shown in Table 1.

Source of inoculants and biological materials
A variety of maize

Land preparation
The land was disc ploughed, harrowed, leveled and then ridged.
The area was divided into 4×4 m² plots with 70 cm apart five ridges.Four seeds were sown per hole and 20cm distance between holes was maintained.Sowing was carried out in the last week of October in 2009 and the first week of November in 2010.Seeds inoculation was performed by coating the seeds with the charcoal-based inoculants.Gum Arabic was used as an adhesive.Chicken manure was applied at a rate of 7 t/ha, distributed on the ridged-plot and mixed with soil.The plots were then irrigated weekly for two weeks before sowing date.Plants were irrigated immediately after sowing then every seven days interval.Plants were thinned to one plant/hole after a week from sowing.Weeding was carried out manually when needed.The nitrogen content and mineral contents of chicken manure were determined by Kjeldahl method and Atomic Absorption Spectrophotometer, respectively.

Experimental design and data collection
The field experiment was laid out in a Randomized Complete Block Design with four replicates .The treatments used were Azospirillum brasilense (A), Azotobacter sp (B), chicken manure (CM) at a rate of 7t/ha and nitrogen (N) in the form of urea (46% N).Urea was applied at two rates: 120kg/ha (N) and 40 kg/ha (T) , Azospirillum brasilense + urea (A+T), Azotobacter sp + urea (B+T), A+CM and B+CM in addition to the control.Data were recorded using a sample of six plants taken randomly from the outer two ridges in each plot.The data were collected at physiological maturity for yield components and after harvesting for grain yield.The data were collected to measure cob length, cob diameter, number of rows/cob, number of seeds/row, 100-seed weight, grain yield/plant and grain yield(t/ha).For the chemical composition, a sample of seeds (50g) was taken from grain yield of each plot, mechanically ground and 5 g was taken to determine the moisture, ash, fat, crude fiber, crude protein and carbohydrates contents according to the methods of AOAC (1984).Tannins content was estimated quantitatively using modified vanillin HCl method (Price et al., 1978).

Statistical analysis
The data were subjected to standard statistical analysis following the procedures described by Gomez and Gomez (1984).Means were separated for significance using Duncan Multiple Range Test (DMRT).

Grain yield components
The effect of various studied treatments on yield and its components was presented in Tables 2 and 3 for the years 2009 and 2010, respectively.Significant increments of the studied parameters were obtained mostly due to the application of chicken manure in the two years, compared to the control.Moreover, positive association effects due to the combined application of chicken manure with Azospirillum brasilence and/or Azotobacter sp were observed in some studied parameters.It is generally assumed that grain yield was influenced mainly by yield attributing components like length and diameter of cob, number of grains per cob and per row, grain weight, weight of 100 grains and filled and unfilled ratio.
Cob length and cob diameter are parameters that influence the number of grains per cob, grain size and subsequently grain yield.Application of CM increased cob length by 21% over the control in 2009 while in 2010 the treatments did not show significant increase in cob length.Comparison of individual treatments means indicated that maximum cob diameters were recorded for CM in both 2009 and 2010.Therefore, application of chicken manure was found to increase cob length and cob diameter.Such results could be attributed to the more availability and supply of nutrients which might have increased the production and enhanced the transfer of assimilates (Anees et al., 2016).Similarly, application of CM significantly (p < 0.05) increased the number of rows per cob.This result might be attributed to the stimulation effects of chicken manure on cell division and/or cell expansion or cell elongation (Yu et al., 1999).Previously, Farhad et al. (2009) reported that number of rows per cob in maize was significantly (p < 0.05) affected by the application of different levels of poultry manure and the maximum values were recorded when applied at a rate of 12 t/ha.Number of grains/row is an important yield determining factor in maize.CM increased the number of grains/row by 27% and 18% compared to the control in 2009 and 2010, respectively.The combined application of chicken manure and the biofertilizres significantly (p < 0.05) increased the number of grains/row compared to the sole application of each biofertilizer.A + CM increased the number of grains/row by 12% compared to the sole application of A in 2009.Also, B+CM increased the number of grains/row by 22% compared to the sole application of B in 2010.Unexpectedly, the combined application of CM and biofertilizers showed non significant increase in number of grains/row compared to the sole application of CM.It has been previously reported that application of biofertilizer had significant effects on number of grains per row (Tarang et al., 2013).
The results also indicated that maximum 100-grain weight (12.56) was recorded for CM application compared to the other treatments.Moreover, the combined effects of the application of chicken manure with the biofertilizers were superior to the use of biofertilizers alone in 2009.The percentages of increment were 15.07 and 19.42% for A+CM and B+CM, respectively, as compared to the sole application of A and B in 2009.This improvement in 100-grain weight could be attributed to the energy source provided to the microbes via organic manure thereby enhancing biological activities and availability of nitrogen.Similar observation and conclusions were also reported by Abdullahi et al. (2014).As shown in Tables 4 and 5, application of CM solely or in combination with A and B significantly (p < 0.05) increased grain yield/plant and grain yield (t/ha) in both years.CM increased the grain yield (t/h) by 20 and 30% over the control in 2009 and 2010, respectively.Several studies have revealed the positive effects of biofertilizers in combination with organic amendments to increase plant nutrients availability, up take and an increase in crop yield (Abdullahi et al., 2013).In 2009, the integrated application of A and B with 40kgN/ha produced grain yield/plant and grain yield/ha comparable to those obtained by the application of the recommended dose of Urea (120kgN/ha).This promoting effect of Azospirillum brasilense and Azotobacter sp could be attributed to their ability to produce biologically active substances, provide significant amount of available nitrogen through biological nitrogen fixation, improve photosynthesis performance and promote root growth which in turn enhance nutrients and water uptake there by resulting in crop improvement.Similar results were recorded previously by Naserirad et al. (2011) and Tarang et al. (2013).

Grain quality
The measured parameters of grain quality showed different responses towards the different treatments (Tables 4 and 5).In both years, microbial fertilizers, chicken manure and urea did not significantly (P<0.05)affect moisture, ash and dry matter contents of maize seeds.However, the highest values of moisture content (5.85 and 7.28%) were observed in 2009 when CM was applied and in 2010 when Azotobacter inoculum was used.The highest percentages of dry matter contents were recorded in 2009 (94.50%) and (93.45%) in 2010 under the application of B+CM.The highest values of fat contents were recorded in both years under the combined application of A and T. The percentages of increment in fat content were 16.27 and 10.38% over the control in 2009 and 2010, respectively.Fiber content is an important constituent for human food and animal feed.
It is generally affected by environmental conditions, varietal characteristics and fertilizer treatments (Elsheikh and Mohameszein, 1998).The highest fiber contents were 4.11% recorded for B with an overall mean of 3.43 and CV 20.79% in 2009 and 3.04% for A+CM with an overall mean of 2.69% and CV 14.40% in 2010.Protein is the most important biochemical character.The highest percentage of protein content (12.13%) was recorded under the application of CM in both years.Such superior effect was achieved due to the increase of nitrogen supply which has paramount effect in the synthesis of protein (Anees et al., 2016).Tannins content is usually affected by many factors such as genotype, time of harvest and temperature .Tannins have been reported to possess anti carcinogenic and antimicrobial properties as well as anti-oxidant activities.The highest value of tannins content (0.14%) was recorded for A in 2010 and the lowest value (0.04%) was recorded for B+T in both years.
The highest values of carbohydrates were 80.34% recorded for A+CM in 2009 and 78.26% for B+T in 2010.These results indicated that carbohydrate content has increased due to the combined effects of the biofertilizers with either chicken manure or urea.These findings are previously reported by Mahfouze and Sharafeldin (2007) who recorded an increase of the total carbohydrate content by the application of biofertilizers combined with 50% nitrogen fertilizer.However, the combined analysis of variance for yield and its components across 2009 and 2010 (Table 6) indicated highly significant differences between the years (environment) and treatments and non-significant for Y×T interactions for the grain yield and its components except for the number of rows/cob .The combined analysis (Table 7) for grain quality indicated significant difference across the years for moisture, dry matter, fiber, protein and carbohydrate contents.Moreover, significant differences between the treatments and Y×T interaction for protein and carbohydrate contents were recorded.The significant differences in maize productivity observed in the two years indicate the strong environmental impact on the treatments.Our findings were in accordance with the previous reports which highlighted the positive effect of chicken manure in improving soil physical properties which enhances root development, water and nutrients uptake and consequently improve maize yield and grain quality (Brady and Weil, 2005;Habashy and Hemeid, 2011) The promoting effect of Azospillium brasilense and Azotobacter sp besides being nitrogen fixers could be attributed to the biologically active substances produced by these organisms such as auxin, cytokinin and amino acids.

Conclusion
The result of this study revealed that, maize grain yield and components are affected positively by the application of chicken manure and the combined application of nitrogen fixing bacteria with chicken manure or urea.Furthermore, considerable effects on the biochemical attributes used to measure the grain quality were also recorded.Environmental conditions had a clear impact on maize productivity.

Table 1 .
Some physical and chemical properties of Shambat soil.

Table 2 .
Effects of bio and chemical fertilizers on yield and yield components of maize at Shambat in 2009.
Within each column, means have the same letter(s) are not significantly different according to DMRT at 5% level of significance.

Table 3 .
Effects of bio and chemical fertilizers on yield and yield components of maize at Shambat in 2010.
Within each column, means have the same letter(s) are not significantly different according to DMRT at 5% level of significance.

Table 4 .
Effects of bio and chemical fertilizers on biochemical characters of maize at Shambat in 2009.Within each column, means have the same letter(s) are not significantly different according to DMRT at 5% level of significance. *

Table 5 .
Effects of bio and chemical fertilizers on biochemical characters of maize at Shambat in 2010.Within each column, means have the same letter(s) are not significantly different according to DMRT at 5% level of significance. *

Table 6 .
Means some of squires from combined analysis of variance for yield and yield components of maize across 2009 and 2010 =highly significant at 1% level of probability, ** =significant at 5% level of probability, ns= is non-significance. *

Table 7 .
Means some of squires from combined analysis of variance for grain quality of maize across 2009 and 2010.