MATERIALS AND METHODS

A field experiment was conducted on a sandy soil conditions at El-khtara, Al Sharqia government, Egypt during the growth season of 2014-2015 to study the effect of nitrogen fertilization from different sources i.e., mineral, organic and bio-fertilizers combined with vermiculite on yield and NPK-uptake by wheat plants (Triticum aestivum cv. Sakha 93). Physical and chemical properties of the investigated soil was analyzed according to the methods described by Richards (1954) and are shown in Table 1.

Mineral nitrogen was added as ammonium sulfate (200 g N kg^–1) at the rate of 0, 119 and 238 kg N ha^–1, respectively in three equal splits. The first dose was after complete germination, while the second and third doses were added after 45 and 60 days, respectively from the first dose. During the preparation of soil for cultivation, the recommended doses of phosphorus and potassium were added for all experimental plots as ordinary super phosphate (65 g P kg^–1) at the rate of 31 kg P ha^–1 and potassium fertilizers were added to the soil as potassium sulphate (410 g K kg^–1) at a rate of 100 kg K ha^–1 before planting. Compost and vermiculite were added and thoroughly incorporated in the soil before planting at the rate of 30 and 4 Mg ha^–1, respectively. Chemical analyses of the compost are shown in Table 1. Seeds were inoculated with Azospirillum brasilense inoculum which has activity in N₂ fixation in the soil and is produced commercially by the Soil Microbiology Unit of the Soil, Water and Environments Research Institute of the Agriculture Research Center, Giza, Egypt. The former factors study i.e., mineral, organic and bio-fertilizers combined with or without vermiculite. Analyses of the vermiculite is shown in Table 1.

Table 1:	Some properties of studied soil, compost and vermiculite
*Soil water extracts 1:1, WHC: Water holding capacity

After preparation of soil for cultivation, the filed was divided into plots each one was 5×10 m. The design was a factorial randomized complete block, involving two factors; factor A: Nitrogen fertilization sources i.e., mineral, organic and bio-fertilizers and factor B: Vermiculite. Therefore, the study contains treatments as follows: Compost+ 238 kg N ha^–1, Compost+119 kg N ha^–1, Compost, biofertilizer +238 kg N ha^–1, biofertilizer+ 119 kg N ha^–1, biofertilizer, 238 kg N ha^–1, 119 kg N ha^–1 and untreated. Previous combinations were applied to plots mixed with or without vermiculite.

At the end of growing season, plant samples were collected and dried at 70°C until constant weight and wet digested using a mixture of HClO₄ and H₂SO₄ for determining some nutrients (Piper, 1950). Dry matter content, nutrient uptake "NPK", protein content and grains yield of wheat plant were conducted. Particle size analysis was determined by the pipette method, bulk density (Klute, 1986), pH and EC were measured in saturated paste extracts (Page et al., 1982), Determination of Ca and Mg was done by atomic absorption spectrophotometry and K and Na by flame emission spectrophotometry, Cation Exchange Capacity (CEC) by the method of Chapman and Pratt (1961) and soil organic matter by wet oxidation (Page et al., 1982).

Statistical analysis: Data was analyzed with analysis of variance (ANOVA) procedures using the MSTAT-C Statistical Software package (Michigan State University, 1983). Differences between means were compared by LSD at 5% level of significant (Gomez and Gomez, 1984).

RESULTS AND DISCUSSION

Yield parameters: Treatments had significant effect on yield and other attributes i.e., straw weight, grain weight, biological yield, harvest index and 1000 grain weight of wheat (Table 2). Yield was significantly higher in the compost+N2 plots combined with or without vermiculite as compared to the other plots. The highest values of yield was 5.32 Mg ha^–1 obtained by compost+N2 combined with vermiculite, while the lowest one was obtained in plants not receiving N-Source i.e., nitrogen mineral fertilization, organic fertilization or bio-fertilizers. Generally, plots receiving compost or bio-fertilizers was more emergence than sole N or control plots. Response to other attributes of wheat i.e., straw weight, grain weight, biological yield, harvest index and the 1000 grain weight followed a similar pattern as that of yield. Superiority of compost+N2 combined with vermiculite over other all treatments occurred with all parameters.

Application of vermiculite under different treatments of N-sources increased straw weight, grain weight, biological yield, harvest index and the1000 grain weight by averages 3, 6, 4.5, 1.4 and 4%, respectively. The favorable effect of vermiculite material on dry matter yield of wheat plants may be due to the positive effect of this material on increasing the available moisture content and hence increasing the availability of nutrients in the soil solution. Obtained results are in agreement with those obtained by Marinova et al. (2012) and Merwad et al. (2013). Martinez-Medina et al. (2009) reported that plants treated with the benmgite-vermiculite formulation showed a higher shoot weight and higher resistance to fusarium wilt disease.

Previous studies justified the positive effects of nitrogen application (Abedi et al., 2010; Ghaderi-Daneshmand et al., 2012) and biofertilizer inoculation (Diaz-Zorita and Fernandez-Canigia, 2009; Kandil et al., 2011). Piccinin et al. (2013) showed that the grain yield of wheat improved when wheat plants were grown with a combination of chemical N and biofertilizer inoculation.

Table 2:	Effect of nitrogen fertilization from different sources combined with vermiculite on yield parameters of wheat plants

Kandil et al. (2011), Wortman et al. (2011), Ghaderi-Daneshmand et al. (2012), Estrada-Campuzano et al. (2012), Liu and Shi (2013) and Namvar et al. (2012) noted that the decrease in biomass production with decreasing supply of N was associated with decreases in both radiation interception and Radiation Use Efficiency (RUE). Nitrogen is known to be an essential nutrient for plant growth and development involved in vital plant functions such as photosynthesis, DNA synthesis, protein formation and respiration (Blackshaw et al., 2005; Rana et al., 2012; Diacono et al., 2013). The growth parameters such as LAI, biomass and leaf photosynthesis significantly decreased due to unsatisfactory N availability (Khan et al., 2007; Azeez, 2009).

Nutrient uptake: The effect of N-fertilization, biofertilizer inoculation and compost on N, P, K and protein of wheat were presented in Table 3. All treatments receiving any or more combinations of the added material showed higher uptake of N, P and K in straw as well as grain compared with control. The highest values of NPK obtained by compost+N2 combined with vermiculite, while untreated plots was the lowest one.

Table 3:	Effect of nitrogen fertilization from different sources combined with vermiculite on N, P and K uptake by wheat plants and protein content

Could be arranged the treatment as following order Compost+238 kg N ha^–1>Compost+119 kg N ha^–1>Compost>biofertilizer+238 kg N ha^–1> biofertilizer+119 kg N ha^–1>biofertilizer>238 kg N ha^–1>119 kg N ha^–1>control.

As shown in Table 3, N application, biofertilizer inoculation and compost had significant effects on protein content of wheat grains. The highest protein content was observed in the application of compost+N2 combined with vermiculite. The highest rate of nitrogen application increased protein content compared to control. Moreover, plants treated with biofertilizer showed more protein content than control. These results are in accordance with the reports of Khan et al. (2007), Sary et al. (2009) and Abedi et al. (2010). Rana et al. (2012) reported an enhancement of 18.6% in protein content with biofertilizer inoculation in wheat. It has been found that in case of an adequate supply of N in the soil, leaf senescence is slower and the plant is able to supply its seeds with N and photoassimilate for a longer period which results in higher protein and grain yield (Azeez, 2009; Abedi et al., 2010).

Application of vermiculite under different treatments of N-sources gave increases of N, P and K uptake in straw of up to 13.6, 15 and 15.5%, respectively and comparable increases in NPK-uptake in grain of up to 18.5, 21.3 and 19.4%, respectively. These results are agreement with those obtained by Merwad et al. (2013) who reported that the application of vermiculite under organic amendments gave the highest values of NPK-uptake by straw and grain of barley plants in sandy soil.

Relationship between nitrogen uptake and grain yield, straw yield and protein: The relationship between nitrogen uptake and grain yield, straw yield and protein under the influence of different treatments were illustrated in Fig. 1 and 2. Overall, there was a positive relationship between nitrogen uptake, grain yield and straw yield of the plant wheat. The correlation coefficient (r) values between nitrogen uptake, grain yield and straw yield of wheat were 0.96 and 0.87, respectively.

Fig. 1:	Relationship between nitrogen uptake, grain and straw yield of wheat plant

Fig. 2:	Relationship between nitrogen uptake and protein

Fig. 3:	Effect of nitrogen fertilization from different sources combined with vermiculite on available nitrogen in soil after harvest

The relationship between nitrogen uptake and protein of wheat plant takes the same positive relationship former trend where more increase nitrogen uptake by wheat plant caused more increase in protein (Fig. 2). The correlation coefficient (r) values between nitrogen uptake and protein was 0.98.

Available nitrogen in soil: Data illustrated in Fig. 3 reveal that values of available nitrogen (mg kg^–1) in the treated soil with nitrogen fertilization from different sources combined with vermiculite after harvest. The treatment of compost+238 kg N ha^–1 combined with vermiculite gave the highest available potassium, while the lowest ones were found with untreated soil. These results are agreement with those obtained by Mohamed et al. (2008) who reported that the addition of compost and taffla to sandy calcareous soil increased N availability in the soil after cultivation. The pattern of comparison among treatments was rather similar to those regarding yields of straw and grains. Use of FYM, wheat straw and green manure in conjunction with fertilizers increased the soil organic carbon, available N, P, K status (Kumar et al., 2012). Significant increases in soil nutrient availability with the application of farmyard manure, paddy straw and green manure along with inorganic fertilizer (Ghosh et al., 2012). Application of vermiculite under different treatments of N-sources gave increases of available nitrogen of up to 14%. These results are agreement with those obtained by Marinova et al. (2012).

CONCLUSION

The results obtained from this study clearly indicated that wheat (Triticum aestivum L.) yield, yield components and protein content of grains had a strong association with the N fertilization, biofertilizer inoculation and compost. Data indicated that application of compost+238 kg N ha^–1 combined with vermiculite giving increases of growth parameters and NPK-uptake of wheat by over that of the other treatments and control. In addition, vermiculite were enhanced effects the former treatments.