Introduction

Foliar spraying is a new method for crop feeding, which micronutrients in form of liquid are used into leaves (Nasiri et al., 2010). It is not a substitute for maintaining adequate levels of plant nutrients in the soil but can be beneficial in certain circumstances. Most commonly, it is recommended for alleviating specific micronutrient deficiencies.  Foliar application of microelements is more beneficial than soil application. Since application rates are lesser as compared to soil application, same application could be obtained easily and crop reacts to nutrient application immediately (Zayed et al., 2011). In recent years, products have been developed that contain growth hormones, natural plant sugars, microorganisms and other ingredients. According to a number of authors, soil fertilization, when combined with foliar feeding, improves both yields and the biological value of vegetables (Osinska and Kolota 1998, Kolota and Osinska 2000). Foliar spraying of microelements is very helpful when the roots can not provide necessary nutrients (Kinaci and Gulmezoglu, 2007; Babaeian et al., 2011). Moreover, soil pollution would be a major problem by micronutrients soil application. As people are concerned about the environment and plant leaves uptake nutrients better than soil application, foliar spraying was created (Bozorgi et al., 2011). Interest in foliar feeding was stimulated during the 1950’s when Tukey and Wittwer at Michigan State University, using radioactive isotopes of known plant nutrients, found that nutrients were absorbed by plant foliage and translocated throughout the plant. In some plants the rate of movement was one foot per hour! They also reported that foliar feeding resulted in about 95 percent efficiency of nutrient use versus only about 10 percent efficiency of nutrient use from soil fertilizer application. There are 2 main paths of entry for foliar nutrients: the cuticle and the stomata.

Cuticle entry: The cuticle is a waxy layer covering leaves, flower petals and fruits. Its primary function is to prevent moisture loss from plants and to protect the plant from injury. It is typically thicker on upper leaf surfaces than on lower leaf surfaces and is impermeable to aqueous (water) solutions; oily solutions will penetrate the cuticle more readily. Cracks can occur in the cuticle and can serve as a port of entry for foliar applications. On young, immature leaves the cuticular layer is not as well developed as an older leaves.

Stomata entry: The stomata of plants are located almost exclusively on the leaves. These pores are only a few millionths of an inch in diameter and their primary function is to breathe for the plant. They allow carbon dioxide, the building block of plants, to pass into the leaf and here the chlorophyll molecules, using sunlight for energy, convert the carbon dioxide molecules into simple sugars. The stomata also allow the by-product of this reaction, oxygen, to escape from the plant. A third function of the stomata is to allow the escape of water vapor that evaporates from the inside of the leaves to cool the plant. Stomata are usually closed at night, and can close during the hottest part of the day. The distribution and occurrence of stomata, as well as their size and shape, varies widely from one plant species to another. Broadleaf crops and tree crops commonly have most of their stomata on the lower leaf surface while grass species may have about the same number on both surfaces. As examples, small white beans commonly have 40,000 stomata per square centimeter on their lower surface and only 3,000 on their upper surface, while sorghum has 16,000 on the lower surface and 11,000 on the upper surface. In horticultural practice, foliar fertilization is also recommended as the most effective method of supplying plants with nutrients under deficiency conditions (Trejo-Tellez et al. 2007). Moreover, Kolota and Biesiada (2000) indicated the possibility of limiting mineral fertilizer use by means of application of foliar fertilization.

Sorghum is the fifth most important cereal crop grown for human consumption in the world being surpassed only by rice, wheat, barley and corn. Sorghum speedfeed is a crop of world-wide importance and is unique in its ability to produce under a wide array of harsh environmental condition (Moghaddam et al., 2007). Most of sorghum grown in Asia and the African tropics is used for human food and also fed to livestock or poultry (Gul et al., 2005). Inorganic fertilizers are important inputs in any agricultural production system and Nitrogen is the essential element required for plant growth in relatively large amounts and its deficiency can result reduce in dry matter, crude protein and grain yield (Ashiono et al., 2005). One factor that continues to be a problem in farming systems is fertilizers management (Khosla et al., 2000). Great efforts have been made to improve sorghum productivity by new cultivars and increasing the efficiency of added fertilizers (Bozorgi et al., 2011). In many cases, aerial spray of nutrients is preferred and gives quicker and better results than the soil (Jamal et al., 2006).

Fertilizers have been proven to play an important role in crop production (Yassen et al., 2010). Although many commercial fertilizers have been shown to increase yields, many of these products are unable to generate a yield increase large enough to cover the input cost of the fertilizer application. Natural propellants have generated a revenue increase per acre that is 2-3 times greater than the input cost of the application. By increasing root development and supplying nutrients directly to the plant, foliar feeding helps the plant achieve maximum growth throughout a variety of adverse growing conditions. The aim of this study was to investigate Stimurel, Force 4-L and Dulzee foliar application effects on Sorghum Speedfeed yield and its components.

Materials and Methods

This study was conducted at Saatlo Agricultural Research Station (37°44 N, 45°10 Ealtitude 1338 m), Iran during the planting seasons of 2010.Generally, climates are dominant in this region. The average annual temperature is 11. 3°C, rain fall is 74.2 mm. The highest relative humidity is 70%. The soils of experimental area as showed in the table 1 were silt clay loam and chemical analysis showed the pH 8 and EC 0.57. The experimental design was a factorial using completely Randomized Block design with 4 replications. Seed was sown by hand in 3-5 cm depth at 166.000 ha in 7 row plots 70 cm apart and 5 m long. Sowing took place on July 2010.

Stimulators

Stimurel: A group of Amino Acid based fertilizers, which act as natural chelation compound, to give growers large and integral choice of fertilizers in all stages of plant growth.

Force 4-L: Is the natural growth stimulator extracted from the Seaweed Ascophyllum nodosum, which contains more than 60 macro and micro elements in addition to natural growth regulators, organic acids and sugars.

Dulzee: Effective foliar Fertilizer which contains Macro and Micro nutrients. The Simulators were purchased from Chemival S.A (Lima, Peru)

Treatments were applied in 3 stages, two, four and six weeks after sown. Analysis of variance of the data from each attribute was computed using MSTATC program. The Duncan’s new multiple range tests at 5% level of probability was used to test among mean values.

Table 1: Physical and chemical analysis of soil.

Results and discussion

Analysis of variance showed that the effect of Stimulators foliar application on panicle length, tiller number, crude fiber, fresh matter and dry weight was significant (p < 0.05), but the effect of foliar application on Number of leaves, Protein(%), Calcium(%)  and Potassium(%) was not significant (Table 2). As seen, all the treatments had positive effects on these factors compared to control. The effect of foliar application showed significant differences in data analysis. Foliar application of Force 4-L and Dulzee had resulted in significant increase in crude fiber (34.55% for Dulzee and 32.73% for Force 4-L), tiller number (1.64 for Dulzee and 2.41 for Force 4-L), fresh matter (10.14 kg/m² for Dulzee and 9.06 kg/m² for Force 4-L), and dry weight (2.17 kg/m² for Dulzee and 1.96 kg/m² for Force 4-L). But foliar application of Stimurel just resulted in significant increase in fresh matter (9.26 kg/m²), and dry weight (1.96 kg/m²) and did not cause any significant effect on the crude fiber properties and tiller number. All the treatments significantly decreased panicle length compared with marker. Number of leaves, Protein (%), Calcium (%) and Potassium (%) was not affected (Table 3). Bozoglu et al. (2007) stated that foliar application of micronutrients could be implemented for higher yield and quality. Zeidan et al. (2006) reported that yield components in lentil are enhanced by foliar application of micronutrients. Due to the enzymatic activity enhancement, microelements effectively increased photosynthesis and translocation of assimilates to the seed.

Table 2. Analysis of variance for the effects of foliar application of Stimurel, Force 4-L and Dulzee on yield and yield components of Sorghum Speedfeed.

^NSNon-significant, *significant at p<0.05 and **significant at p<0.01

Table 3: Mean comparison effect of foliar application of Stimurel, Force 4-L and Dulzee on yield and yield components of Sorghum Speedfeed by Duncan’s Multiple Range Test (DMRT). 

In each column, means with the similar letters are not significantly different at 5% level of probability using DMRT

The most interesting observation in this study was the significant enhancement of fresh matter and dry weight of the plants. As Arif et al. (2006) reported that higher yield could be achievable by foliar application of nutrients which ensures crop dry matter production.

The plant can synthesize amino acids needed to produce plant tissues but consumes energy for its photosynthesis. Amino acids play an important role in photosynthesis, protein synthesis and respiration. It has been found that we can supply plant with ready amino acids, and to save energy and accelerate biochemical reactions and stimulate growth in general, which will lead for better quality and higher yield. Crop roots are unable to absorb some important nutrients because of soil properties, such as high pH, lime or heavy texture, and in this situation, foliar application is better as compared to soil application (Kinaci and Gulmezoglu, 2007). Narimani et al. (2010) reported that microelements foliar application improve the effectiveness of macronutrients. It has been found that microelements foliar application is in the same level and even more influential as compared to soil application. It was suggested that micronutrients could be applied successfully to compensate shortage of those elements (Arif et al., 2006, SeifiNadergholi et al., 2011). These authors found that based on soil properties, foliar spraying could be effective 6 to 20 times as compared to soil application. Resistance to different stresses will be increased by foliar application of micronutrients (Ghasemian et al., 2010). According to results of this research Stimulators can Increase plant ability to absorb nutrient and increase photosynthesis quality. They also enhance protein production in short time with less energy consumption. Since in field situation, soil features and environmental factors which affect nutrients absorption are extremely changeable, foliar application could be an advantage for crop growth. Also, effectiveness of foliar application is higher and the cost of foliar application is lower as compared to soil application. This research highlights the importance of foliar feeding of the crops as a means of correcting nutrient deficiencies that occur during the growing season.

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