2.1 APPLICATION OF SPECIFIC BIOFERTILIZERS IN DIFFERENT CROPS

Application of Rhizobium Inoculant

The effect of inoculants on the growth and yield of legume crops depends on the quality of inoculant, soil properties and application techniques. Generally, inoculants should be used according to the specification on the package and when a legume is introduced into a new area or when the legume is known to have a nodulation problem. The main purpose of inoculation is to nodulate the host legume with a selected rhizobial strain. The inoculant should be of good quality at the time of application.

Commonly, two application methods are used in the inoculation of rhizobial biofertilizers to legumes. This is direct inoculation, where the inoculant is placed in direct contact with the seeds (seed-applied inoculant), and indirect inoculation, whereby the inoculant is placed alongside or beneath the seeds (soil-applied inoculant).

Inoculant is applied to seeds in the following ways:

a) Dusting: With this method, the inoculant is mixed with the dry seeds directly. This may lead to poor adherence of rhizobia to the seeds; the method is least effective.

b) Slurry: The inoculant can be mixed with wetted seeds, or diluted with water and some stickers, e.g. 25% solution of molasses or 1% milk powder. In some cases, gum Arabic, sucrose of methyl ethyl cellulose can be used as stickers.

c) Seed coating: The inoculant can be made into slurry and mixed with the seeds. The seeds are then coated with finely ground lime, clay, rock phosphate, charcoal, dolomite, calcium carbonate or talc. The method has several advantages, such as protection of rhizobia against low pH soil, desiccation, acidic fertilizers, fungicides or insecticides.

In the indirect application method, the inoculant is applied to the soil beneath or alongside the seeds. The method is used when seeds are treated with fungicide or insecticide, and when a high amount of inoculant is needed to outcompete the indigenous rhizobial population. The simplest inoculation is to prepare the liquid formulation of the inoculant and spray to the soil or directly over the seeds after placement. In this case, a high amount of inoculant is needed. Some disadvantages of this method include loss of viability of rhizobia, short storage period and difficulty in the distribution of inoculant.

Application of Non-Symbiotic Nitrogen Fixers Inoculant

Azospirillum

Application of biofertilizers from associative nitrogen-fixing bacteria

Benefits of Biofertilizers

In general, biofertilizers from associative nitrogen-fixing bacteria could be used especially for cereal crops such as rice and wheat, but also for cash crops such as vegetables, fruits, flowers, tobacco, cotton, oilseed, tea and medicinal or herbal crops. BIO-N in the Philippines is a microbial-based fertilizer for rice, corn and other agricultural crops like tomatoes, pepper, aubergine, okra, lettuce, peach and ampalaya. It is a breakthrough technology that promises very significant impact on the country’s farmers in terms of increasing farm productivity and income as well as saving the country’s dollar reserve due to decreased importation of inorganic nitrogenous fertilizers. It is mainly composed of microorganisms that can convert the nitrogen gas into available form to sustain the nitrogen requirement of host plants. The active organisms (bacteria) were isolated from the roots of Talahib, a grass relative of sugar cane. These bacteria, once associated with the roots of rice, corn, sugar cane and some vegetable plants, can enhance their root development, growth and yield.

In China and other FNCA countries, associative nitrogen-fixing bacteria biofertilizers have increased the yields by 10–30% and reduced the use of chemical N fertilizer by 15–25%. It is reported that application of biofertilizer with associative nitrogen-fixing bacteria could enhance the maturation of crops, shorten the vegetation period by 5–10 days and improve the soil quality and soil fertility.

The benefits of biofertilizers with associative nitrogen-fixing bacteria can be seen as follows:

1. Enhance the shoot growth and root development;
2. Improve the yield of host plants;
3. Replace 30–50% of the total amount of N requirement;
4. Make plants resistant to drought and pests;
5. Reduce the incidence of rice tungro and corn earworm attack;
6. Increase the yield and milling recovery of rice.

Application in Cereal crops:

The liquid form is good for rice. At transplanting, immerse rice roots into liquid biofertilizer for 10–15 min before transplanting and spread on paddy soil at the regreening stage at a rate of 1.5–3.0 L per ha. For wheat, immerse the seeds into liquid biofertilizer overnight before sowing, and spread onto wheat leaves at a rate of 1.5–3.0 L per ha with water.

Vegetables:

Solid biofertilizer is spread, band-spread and hole-applied as basal or top dressing. For leaf vegetables such as celery, spinach and cabbage, apply at a rate of 3.75–15.0 kg per ha. For fruit vegetables such as cucumber, aubergine, tomato and melon apply at a rate of 7.5 kg per ha. For root vegetables such as sweet potato, potato, ginger and garlic, apply at a rate of 3.75–15.0 kg per ha.

Fruits:

For fruit trees, 10–20 g, 20–30 g or 30–50 g per plant will be applied to those, respectively, with plant yield less than 50 kg, 50–100 kg and over 100 kg.

Tobacco:

Rates of 6.25 kg per ha are applied. For those where biofertilizer with associative nitrogen-fixing bacteria is applied, the N-fertilizer should be reduced by 20–25%. Mixed application with organic manure should be encouraged because organic manure will benefit microbes.

Corn:

1. Place seeds in a suitable container and moisten with water. Pour a sufficient amount of inoculant, 1 packet of BIO-N for every 3 kg of seeds.
2. Mix thoroughly until the seeds are evenly coated; (a drop or two of sticker, e.g. Tween 20 or APSA may be mixed with water to enhance adsorption of BIO-N onto the seeds).
3. Sow the coated seeds immediately. Be sure not to expose the inoculated seeds to direct sunlight.
4. Depending on the soil analysis, very marginal soils may require a basal application of at least a bag or two of 14-14-14 to a hectare as side dress.

NOTE:

The basal application of organic fertilizer is highly recommended to provide a whole array of other nutrients for a balancing effect. Split application of the recommended inorganic macro-elements has been found effective, e.g. second application of 14-14-14 NPK is done before tasseling.

Rice:

As solid inoculant for direct-seeded rice:

1. Soak seeds overnight in clean water
2. Pre-germinate the seeds in gunny sacks or a suitable container.
3. When radicles (embryonic roots) come out, place the germinants in a suitable container.
4. Pour the required amount of BIO-N and mix thoroughly until the germinants are evenly coated.
5. Sow directly over field or on prepared beds.

As liquid inoculant for dapog bed:

Suspend the required amount of Bio-N in sufficient volume of clean water (e.g. 1 packet Bio-N to 1 gallon water) and evenly drench the seed/seedling-lined dapog bed.

As slurry for transplant seedling:

1. In a suitable container, mix BIO-N with clean water to form a slurry or thick preparation.
2. Prune the roots of seedlings into uniform length and dip for at least 30 min or 1 h before transplanting.

Procedures for Growing Corn using Biofertilizer Inoculated Seeds

A) Seeds

• Use the best seeds for certain locations as recommended by the Department of Agriculture.

B) Land Preparation

• The land is ploughed with a tractor with a depth of 15–20 cm, and then hoed.
• Clear the land from weeds and prepare seedbeds.

C) Seeds Inoculation

• Check the instructions on the biofertilizer pack. For example, one pack of biofertilizer for corn (200 g for 2000 m) and 3 kg of seeds.
• Inoculation is done step by step. Prepare one clean bucket or plastic bag to hold the seeds that are being inoculated. Prepare slurry by mixing a sticker with the inoculant. If sticker is not available, use vegetable oil.
• Mix the slurry thoroughly with corn seeds and let them dry.
• When inoculating seeds, avoid making them too wet. See the procedure on the pack.
• Sweet-corn seeds are commonly coated with fungicide. Use a larger amount of inoculant and plant immediately after inoculation.
• Inoculated seeds are ready to sow. Put the inoculated seeds under shade.

D) Sowing

• Sow the seeds at a planting distance of 75cm x 25 cm.
• To protect seedlings against infestation by seed flies, insecticide is applied to seed holes.

E) Fertilization

• Basal fertilizer, 66 kg/ha of N (urea), 150 kg/ha of SP-36 and 100 kg/ha of KCl are applied at 10 days after planting (DAP), banded in a depth of 5 cm and applied 7 cm in front of plant rows.
• Second N fertilization, 33 kg/ha of urea is applied banded at 10 cm in front of plant rows.

F) Weeding

• Weeding is done before fertilizer application.
• At the second N fertilizer application, the soil and weeds are returned back to plant rows.

G) Pest Management

• Spray the plants with suitable insecticide at the recommended dose as soon as the symptoms of infection appear.

H) Watering

• Corn needs sufficient water at sowing, flowering and grain filling.
• Drainage is made to avoid flooding.

I) Harvesting

• Harvesting could be done at around 96 DAP for corn varieties, and 70 DAP for sweet corn.

Application of Mycorrhizal Inoculant

1. The application rate of VA Mycorrhiza biofertilizer is 10 g or 1 spoonful per plant.
2. VA Mycorrhiza biofertilizer can be used at any stage of plant growth. However, for maximum benefits, it should be applied during the seedling stage or placed at the base of plant holes before planting. After two weeks of application, other suitable fertilizers can be applied.
3. For planting by stem cutting, the growth media are mixed with VA Mycorrhiza biofertilizer prior to planting. The cutting stocks can be transferred to the field one month after roots have developed.
4. For transplanting, simply sprinkle VA Mycorrhiza biofertilizer adjacent to the plant roots and cover with soil.
5. For grown trees, the soil under the plant canopy is trenched or the leaf litter under the tree is removed. About 10 g (1 spoonful) per plant of VA Mycorrhiza biofertilizer is applied to the root hair system and then covered with soil.
6. VA Mycorrhiza biofertilizer can be used in combination with several types of biofertilizers (e.g. Rhizobium biofertilizer, or PGPR).

Application of Phosphate Solubilizers Inoculation

Generally biofertilizers in powder form are applied like organic matter onto the soil. This type is very convenient for users in the management of biofertilizers. Some biofertilizers are costly products for farmers, so their use would be restricted by the specific conditions of agronomy. Microorganisms are generally supplied by producers of biofertilizers, so it is only necessary for the users or farmers to follow the application method recommended by the manufacturers. However, the popular application method is regarded as the next procedure.

Figure 8.1: Vultivation of Phosphate Solubilizers

Two weeks before spore inoculation, the desired seedlings (e.g. oil palm, vegetable, pasture grass) are prepared in suitable containers filled with sandy loam soil.

Improvement of phosphate solubilizers:

An alternative approach for the use of phosphate-solubilizing bacteria as microbial inoculants is the use of mixed cultures or co-inoculation with other microorganisms. Evidence points to the advantage of the mixed inoculations of PGPR strains comprising phosphate-solubilizing bacteria. The effect of combined inoculation of Rhizobium, a phosphate-solubilizing Bacillus megaterium ssp. phospaticum strain-PB and a biocontrol fungus Trichoderma spp. on the growth, nutrient uptake and yield of chickpea were studied under glasshouse and field conditions. Combined inoculation of these three organisms showed increased germination, nutrient uptake, plant height, number of branches, nodulation, pea yield and total biomass of chickpea compared to either individual inoculations or an inoculated control.

On the other hand, it has been postulated that some phosphate-solubilizing bacteria behave as mycorrhiza helper bacteria. It is likely that the phosphate solubilized by the bacteria could be more efficiently taken up by the plants through a mycorrhizal pipeline between roots and surrounding soil that allows nutrient translocation from soil to plant. Considerable evidence supports the specific role of phosphate solubilization in the enhancement of plant growth by phosphate-solubilizing microorganisms. However, not all laboratory or field trials have offered positive results. Therefore, the efficiency of the inoculation varies with the soil type, specific cultivars and other parameters.