ABSTRACT
The effect of using dry microalga (Chlorella vulgaris) as soil additives on the nutrient status and shoot and root growth of maize plants (Zea mays L. var. Triple-hybrid 310) was investigated. Algae were added to the soil before sowing in the rates of 50, 100, 150 and 200 Kg /Fed, in addition to the basic NPK fertilizers. Significant increase in the nutrient taken up by shoots and roots was calculated as a result of adding different alga-levels. Addition of algae has significant increases in root volume, chlorophyll formation, dry weight of shoots and roots as well as plant height. The best treatments were 150 and 200Kg algae/Fed.
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DOI: 10.3923/jbs.2001.475.479
URL: https://scialert.net/abstract/?doi=jbs.2001.475.479
INTRODUCTION
From the agricultural viewpoint, soil is the unconsolidated mineral material on the immediate surface of the earth that serves as natural medium for plant growth. Nutrient supply to the roots is governed by nutrient concentrations in the soil solution, nature of the nutrients, soil moisture status and plants absorption capacity which are related to soil physical and chemical properties (Fageria et al., 1997). Green plant materials proved to improve soil characteristics (i.e. soil moisture holding capacity, aeration, cation exchange capacity, growth of the soil microorganisms etc.) providing favorable conditions in the plant growth medium (Al-Gosaibi, 1994; De Boodt, 1975). Green manures were also found to stimulate root growth and produce good yields (Boussiba, 1987; Marschner and Roemheld, 1996; Mandimba et al., 1998; Paturde and Patankar, 1998; Buragohain and Medhi, 1999; Kumar et al., 1999; Shaaban and Mobarak, 2000).
Dry green algae contain high percentage of macronutrients, considerable amounts of micronutrients and amino acids (El-Fouly et al., 1992). They can be cheaply produced on sewage and brackish water and partially substituted the chemical fertilizers to avoid environmental pollution.
This project was carried out to study the effect of dry microalga Chlorella vulgaris as soil additives on the root volume, shoot and root nutrient content, chlorophyll formation and consequently growth of maize plants under field conditions.
MATERIALS AND METHODS
Experimental design and sowing: A field experiment was conducted at Abu-Dahshan area, Ismailia, Egypt during the seasons 1997/1998 and 1998/1999 as Randomized Complete Block Design (RCBD). Soil was prepared and received super mono-phosphate (15.5% P2O5) at 200 Kg/Fed (1 Feddan = 0.42 hectare). Soil physical and chemical characteristics and their evaluation according to Ankerman and Large (1974) are shown in Table 1. Seeds were sown in May, 1, 1997 and May, 3, 1998 in 50 cm lines at 25 cm distance and 4-5 cm depth at 2-3 seeds per hole and irrigated. The soil was hoed 2 times (before the 1st and 2nd irrigation). Before the 1st irrigation, the plants were thinned to leave 1 plant per hole. Dry microalgae (Chlorella vulgaris) was added to the soil before sowing. Major components and chemical composition of the dry alga are shown in Table 2. NK at 100 unit N/Fed. as ammonium sulfate (20.6% N) and 90 unit K/Fed. as potassium sulfate (48-52% K2O). Dry microalgae was added in the rates of 50, 100, 150, 200 Kg/Fed.
After soil preparation and before fertilization, a representative soil sample was taken.
Table 1: | Mean values of physical and chemical soil characteristics |
A= deficient, B = low, C = adequate, H = high (Ankerman and Large, 1974) |
The sample was air-dried and passed through a 2.0 mm sieve pores. The following analyses were carried out.
Mechanical analysis: By using hydrometer method (Bouyoucos, 1951); pH and E.C (electric conductivity) were determined in soil/water extract (1:2.5) (Jackson, 1973); Calcium carbonate content was determined using Calcimeter method (Black, 1965), and organic matter (O.M.) was determined using potassium dichromate method (Walkley and Black, 1934).
Soil phosphorus was extracted using sodium bicarbonate (Olsen et al., 1954). Potassium (K) and magnesium (Mg) were extracted using ammonium acetate (Chapman and Pratt, 1978), while Fe, Mn, Zn and Cu were extracted using DTPA (Lindsay and Norvell, 1978).
Fourty days after sowing, maize plants were harvested. Plant height was measured (cm) and then, the plants were divided into shoots and roots, washed with tap water, distilled water (containing 0.01 N HCl) and bidistilled water. Root volume was determined using water displacement in a graduated glass cylinder. Maize plant parts as well as the dry algae were oven dried at 70°C for 24 h. Dry weight of maize plant parts was determined and the plants were ground. 1.0 g of both maize plant parts and dry algae was dry-ashed in a muffle furnace at 550°C for 6 h using 3.0 N HNO3. The residue was, then, suspended in 0.3 N HCl.
Protein content of the dry algae was calculated as total nitrogen ×6.25. Algae fat content was determined in its ether-extract using method of AOAC (1965). Total carbohydrate content was determined according to DuBois et al. (1956).
Chlorophyll content was determined before harvesting in leaves using the portable Hydro N-Tester chlorophyll meter.
Table 2: | Major components and chemical composition of dry Chlorella valgaris |
*After El-Fouly et al. (1992) |
Table 3: | Mean values of macro and micronutrients uptake by maize plants as affected with different levels of dry algae as soil additives |
Table 4: | Uptake increase (% over control) of macro- and micronutrients by maize plants as affected with different levels of dry algae as soil additives (mean values) |
Fig. 1: | Mean values of nitrogen, phosphorus, potassium, iron, manganese and zinc concentrations in shoot and roots of maize plants as affected by dry algae as soil additives |
Fig. 2: | Maize root volume (cm3) as affected by different dry algae levels as soil algae additives (columns with same letter are not significantly different, p = 0.05) |
Fig. 3: | Chlorophyll-meter readings of maize levesa as affected by levels as soil additives (values with same letter are not significnatly different, p = 0.05) |
Fig. 4: | Mean dry weight and plant height of maize plants as affected by different algae levels as soil additives (columns with same letters are not significnatly different, p = 0.05) |
Total nitrogen content of maize plant parts and dry algae was determined using Bauschi digestion and distillation apparatus. Phosphorus was photometrically determined in the dry ashed residue using the Molybdate-Vanadate method and measured using the UVNIS Spectrophotometer. Potassium and Ca were measured in the extract using (Jenway PFP7) Flamephotometer. Mg, Fe, Mn, Zn and Cu were measured using the Atomic Absorption Spectrophotometer.
Data were statistically analyzed using Costate Statistical Package (Anonymous, 1989).
RESULTS AND DISCUSSION
Nutrient concentrations and uptake: Nutrient concentrations as affected by different levels of dry algae as soil additives are shown in Fig. 1. According to Fageria et al. (1997), all the determined nutrients were within the adequate range. Phosphorus and micronutrients Fe, Mn and Zn concentrations were slightly increased, especially in roots. This can be explained by the more availability of these nutrients in the root medium as a result of alga additives. The picture is clearer with the nutrient uptake calculations (Table 3, 4). Uptake of all nutrients by shoots and roots were increased. Highly significant positive correlations were found between the increased levels of alga additives and nutrient uptakes. As the high soil pH (which is characteristic for most of the Egyptian soils), algae additives can serve as a soil conditioner improves the physical and chemical characteristics of the soil rendering better nutrient availability. Shaaban and Mobarak (2000) obtained similar results with faba bean plants. Amino acids-containing algae can also act as phytosiderophores facilitating the absorption of micronutrients by the roots (Marschner and Roemheld, 1996).
A direct reason for increasing uptake of nutrients is the significant increases in the root volume caused by adding different levels of dry algae (Fig. 2), which plays a good role in increasing the absorption surface to different nutrients. As the nutrient status of the shoots were improved, chlorophyll formation rate in the leaves was significantly increased (Fig. 3) and together led to more biosynthesis and biomass accumulation.
Growth: Growth expressed in g/plant and plant height is shown in Fig. 4. Both root and shoot dry weight and consequently total dry weight of the plants was found to increase significantly with the addition of increased alga levels. This was also true for the plant height records. The best treatments were 150 and 200 Kg algae/Fed. Increase in dry weight accumulation as well as plant height is a result of improving the nutrient status in the plant tissues caused by the presence of alga material in the root medium. Similar trends were found by Al-Gosaibi (1994) and Shaaban and Mobarak (2000).
It can be concluded that dry microalgae as soil additives improve plant nutrient status, which, in turn enhances all the physiological reactions that lead to a good growth. A quantity of 100-150 Kg dry algae/Fed can improve soil physical and chemical characteristics and save the addition of secondary and microelements required for a good yield. Furthermore, use of such cheap material as a soil additives can improve soil fertility, plant nutrient status, save costs of secondary and micronutrients required for obtaining good yields and leads to less environmental pollution.
ACKNOWLEDGEMENT
The author wishes to thank the staff members of the program "Micronutrients and Plant Nutrition Problems" and its coordinator Prof. Dr. Mohamed M. El-Fouly for their help in the course of the study.
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Reuben Riley Rampersad Reply
Is it possible to state how many replicates were used for each treatment?
Kind regards