Effect of Mineral Organic Fertilization and Inoculation with Phosphate- Solubilizing Microorganisms on Growth and Yield of Sorghum (Sorghum bicolor L.)

INTRODUCTION

Sorghum (Sorghum bicolor, L. Moench) belongs to the family Poaceae, including both wild and cultivated sorghum. Sorghum is the fifth important crop among the cereals in the world following rice, wheat, maize and barley in total area planted and production (Musa et al., 2012). Sorghum is the principal cereal that forms an important staple diet throughout the semiarid Asian and African regions (Ahmed et al., 2000).

However, fertilizer management is one of the most important factors in successful cultivation of sorghum plants. Fertilizers can affect the yielding, quality and quantity of plant indexes (El- Zeny, 2004). For instance, organic agriculture is a production management system that aims to promote and enhance ecosystem health, including biological cycles and soil biological activity. It is based on minimizing the use of external inputs, and represents a deliberate attempt to make the best use of local natural resources (Hag Ahmed et al., 2007).

Furthermore, biofertilization is one of the most important factors used to produce product free from mineral contamination. On the other hand, the intensive use of chemical fertilizer (in spite of the importance of N, P in metabolic processed), causes environmental pollution problems, and its high rates lead to decrease in the potential activity of micro flora and the mobility of organic matters. Hence the attention has been, focused on the researches of bio- fertilizers to replace the chemical fertilizers. However, biofertilizers play vital role for increasing the number of microorganisms and accelerate certain microbial process in the rizosphere of inoculated soil pf plants which can change the available forms and nutrients into plants (Mitkess et al., 1996; Ali et al., 2001; Saini et al., 2004 and Musa et al., 2012).

There were significant differences of growth characters, yield and its components except specific leaf area and harvest index obtained when plant were treated with bio-fertilizer. the combined inoculation with Azotobacter vinelandlii and Pseudomonas fluorescens surpassed the single inoculation either in presence of full or double full dose of organic manure in all characters but the positive control of the recommended doses of NPK recorded the highest significant values in all growth characters at all tested plant ages and yield and its components, while the combined inoculation treatment in presence of either full or double full organic matter dose came in the second order (Ahmed et al., 2010).

The use of phosphate solubilizing bacteria as inoculants simultaneously increases P uptake by the plant and crop yield. Strains from the genera Pseudomonas, Bacillus and Rhizobium are among the most powerful phosphate solubilizers. The principal mechanism for mineral phosphate solubilization is the production of organic acids, and acid phosphatases play a major role in the mineralization of organic phosphorous in soil. Several phosphatase-encoding genes have been cloned and characterized and a few genes involved in mineral phosphate solubilization have been isolated. Therefore, genetic manipulation of phosphate-solubilizing bacteria to improve their ability to improve plant growth may include cloning genes involved in both mineral and organic phosphate solubilization, followed by their expression in selected rhizobacterial strains (Rodríguez and Fraga, 1999).

Therefore, the aim of this study is to study the effect of mineral- organic fertilization and inoculation with phosphate solubilizing microorganisms on growth and yield of sorghum (Sorghum bicolor, L. Moench).

MATERIALS AND METHODS

Two field experiments were carried out at the Experimental Farm of the Faculty of Agriculture (Saba Basha), Alexandria University, at Abbes region, Alexandria, Egypt during two successive cropping seasons of 2012 and 2013. The applied experimental design was split plot with three replicates. The main plots were allocated for three mineral- organic fertilizers (FYM) of nitrogen (100 % N (80 kg N/fed.), 75% N + 25% organic and 50% N + 50% organic manure), the sub- plots were occupied by the following four treatment of P- biofertilizers (uninoculation +100% P, Phosphorein + 75% P, Mycorrhizal + 75% P and mixture (Mycorrhizal + Phosphorein + 75% P).

Chemical and physical analysis of the experimental soil sites (0 to 30 cm) are shown in Table (1), according to the method reported by Page et al., (1982). The chemical characteristics of compost manure composition are given in Table (2).

The sub plots consisted of 5 ridges 3.5 meters in length, 60 cm in width and 20 cm between hills. Nitrogen fertilizer was applied at rate of 80 kg N/fed., (100 % N) from urea fertilizer (46% N) 60 kg N/fed., (75% N) and 40 kg N/fed., (50 % N) in two equal doses. The first one applied just before the first irrigation and after thinning and the second one applied just before the second irrigation. Phosphorus fertilizer was applied before planting as Calcium- super phosphate (15.5 % P₂O₅) at the rate of 150 kg. Potassium sulphate (48 % K₂O), was added before the first irrigation at rate of 50 kg K₂O/fed.

Sowing (Sorghum bicolor L., cv. Dorado) was done on 18^th and 20^th of June in 2012 and 2013 seasons, respectively. The preceding crop was wheat in the first season and Egyptian clover in the second season.

The seeds inoculation of biofertilizers (Phosphorein) with each product individually using a sticking substance (Arabic gum 5%) just before planting. Inoculation of A-mycorrhizal fungi for sorghum with fungi (Glomus macrarpium) strain from plant production Dept. (Saba Basha). Alex. Univ., at a rate of 250 ml of infected roots and was mixed with seeds.  

Harvesting time was in 20^th and 22^th of October 2012 and 2013 seasons, respectively.

The following data were recorded in the both seasons.

A- Growth characters

Plant height (cm), leaf area index (LAI), stalk diameter (cm), and number of branches/head according to Watson (1952).

Total chlorophyll was determined by digital apparatus (SPAD-502) according Monje and Bugbee (1992) and Coste et al. (2010) who suggested this equation to transferred SPAD units to mg/m².

 Y = 1.034 + 0.308 * X + 0.11 * X²

where: X= SPAD units

B- Yield and its components

Panicle length (cm), Panicle weight (g), Panicle grain weight (g), 1000- grain weight (g), grain yield (tons/fed.), straw yield (tons/fed.), and biological yield (tons/fed).

C- Grain chemical composition

Grains digested with H₂SO₄- H₂O₂ mixture (Lowther, 1980) and the following determination were carried out in the digested solution to determine the following:

1-    Total N in grains was determined calorimetrically by Nessler's method (Champan and Pratt, 1978).

2-    Total P in grain was determined using vanado- molybdate yellow method (Jakson, 1973).

3-    Total K in grains was determined using the Flame Spectrophotometer.

The obtained data were statistically analyzed using ANOVA and L.S.D. values were calculated to test the difference between the studied treatments according to Gomez and Gomez (1984).

Table (1). Some physical and chemical properties of the experimental soil in 2012 and 2013 season.

Table (2). Analysis of the applied organic manure (Farmyard manure) in 2012 and 2013 seasons.

RESULTS AND DISCUSSION

A- Growth characters

The obtained results given in Table (3), showed clearly that mineral nitrogen + organic manure rates exhibited significant effect on all estimated growth traits during both cropping seasons except the stalk diameter in the first season of the study. Notably application mineral nitrogen + organic manure fertilizer rates resulted in a significant effect on plant height, leaf area, number of branches/head, stalk diameter and total chlorophyll. Also, application (50 % mineral N + 50 % organic manure) gave the highest values of all characters under the study. It could be concluded that the best vegetative growth characters results from the medium percentage compost manure + mineral nitrogen treatment. This finding could be attributed to the mode of action of organic manure in improving the chemical and physical soil characters and increasing nitrogen nutrition as indicated by increased N concentration in plant tissue (Latif et al., 1998). Also, inoculation with biofertilizer plus P significantly increased plant height, leaf area index (LAI), stalk diameter (cm), number of branches/head and total chlorophyll during both seasons (Table 3).

The interaction between mineral + organic manure and P- biofertilization was significant for some growth characters in both seasons Table (3). These results are in harmony with those reported by Agbede et al. (2000), Wang et al. (2003) and Saini et al. (2004).

Table (3). Effect of mineral nitrogen, organic, P- biofertilization and their interaction on some growth attributes

               of Sorghum bicolor L., cv. Doradoin 2012 and 2013 seasons

   N.S.: not significant difference at 0.05 level of probability.

   *       : Significant at 0.05 level of probability.

B- Yield and its components

  The results recorded in Table (4) showed that yield and its components for both growing seasons were, significantly, affected by “mineral + organic manure rates”. Application of (50% N+ 50% organic) significantly increased grain yield/fed in both seasons. It could be concluded that the organic manure is beneficial than inorganic fertilizers because the long term use of the combined application of organic and inorganic fertilizers not only increase the soil fertility through increase in nitrogen availability in soil and nitrogen up take by plants but also have an improvement in grain yield. The previous results agree more or less, with the finding of Wang et al. (2003), Materechera and Salagere (2002), and Hag Ahmed et al. (2007).

The mixture biofertilizer plus P (A- Mycorrhizal + Phosphorein) treatment increased the production of sorghum. However, This could be attributes to more adsorption of nutrients, amino acids, cyotkinins, Gebberellins and sugars that come from adding of bacteria's, AM and P. this reflect more growth activity of nitrogenous compounds, assimilation, forming more growth substances, more cell division and elongation in the merstimatic zones and the direct or indirect role of fertilization treatments on metabolism and photosynthetic process of the plants. Similar finding were reported by Hassanein et al. (1997), Ali et al. (2001), Reda et al. (2004) and Saini et al. (2004).

Data in show the effect of P- biofertilizer inoculation on yield and its components of sorghum characters (Panicle length. Panicle weight, Weight of grain/panicle, 1000- grain weight, grain and straw yields/fed and biological yield/fed) in the two seasons. Yield and its components were improved by the inoculation mixture biofertilizer (A- Mycorrhizal + Phosphorein) + 75% P which caused significant increases which may be attributed to the active role of phosphorus dissolving bacteria and fungi and increasing the endogenous photohormones e.g. IAA, GAs and CKs which play important role of formation a big active system and hence increasing the nutrients uptake photosynthesis rate and translocation as well as accumulation within different plants. This result was in accordance with that obtained by Materechera and Salagae (2002), Saini et al. (2004) and Musa et al. (2012).

The interaction between organic manure + mineral and P- biofertilization was significant for yield and its components in both seasons Table (4).

Figures (1, 2, 3 and 4) conducted that fertilized sorghum plants by 50 % mineral N + 50 % organic N with 75 % mineral P + Phosphorein + Mycorrhizal as mixture recorded the highest mean values  of 1000- grain weight (g) and grain yield (ton/fed).

Table (4). Effect of mineral nitrogen, organic manure and P- biofertilization on some yield and its components of Sorghum bicolor L., cv. Doradoin 2012 and 2013 seasons

    *   : Significant at 0.05 level of probability.