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2.6 APPLICATION OF BIOFERTlLlZER ON FRUIT CROPS
The use of biofertilizer, even though not spread on a wide scale for all crops, has witnessed growing awareness among the farmers that production can be increased by the use of biofertilizers in case of cereals, pulses, oil seed and some cash crops like vegetables and sugarcane. Biofertilizers are a recent concept in horticultural crop practices.
Generally, fruit crops have now received more attention than vegetables and ornamental crops. Glomus fasciculatum, Glomus mosseae, Azospirillum, Azotobacter and PSB are found useful for different horticultural crops. Use of biofertilizers, particularly inoculation with Azotobacter, could substitute 50% of the nitrogen requirement of banana and could produce higher yields over full doses of nitrogen application. The absorption of mobile nutrients like nitrogen also increases in association with VAM fungi.
Beneficial effect of Azotobacter and Azospirillum in enhancing the productivity of banana has also been reported. VAM fungi are responsible for more than two-fold increased acquisition of the less mobile nutrient elements like P, Ca, S, Zn, Mg and Cu from the rhizosphere. The high efficiency of AzospiriIlum for fixing nitrogen and better mobilization of fixed phosphorus by VAM even at high temperature can make these highly suited for mosambi (sweet lime). The percent of wilting in VAM-treated trees of guava has been recorded to be lower as compared to that of untreated trees. The content of N, P, K and also of Fe, Mn, Zn and Cu increases due to VAM inoculation. Studies on biofertilizers along with chemical fertilizers have been undertaken for assessment of their effect on the growth, yield and quality in mosambi.
The role of biofertilizers in fruit crops are discussed below.
2.6.1. Effect of biofertilizers on growth characteristics
- VAM significantly increase the growth of plants compared to non-mycorrhizal control and are also effective in increasing the nutrient uptake by plants.
- VAM influence the growth-related characteristics and the yield-related component. About 50% cut-back on the use of phosphorus can be achieved through the use of VAM.
- VAM fungi have been found to be effective in papaya in increasing the plant height, stem girth, petiole length and the number of leaves.
- Mycorrhizal treatment is superior to non-mycorrhizal treatment in pomegranate.
- The Glomus epigaeum (GE) + G. mosseae + Gigaspore calospora mixture has been reported to give the maximum height, root length, number of leaves, dry weight of shoots and roots and mycorrhizal dependency percentage in pomegranate.
- The response of VAM on apple seedlings in combination with VAM, Azotobacter and inorganic fertilizers.
- Dual inoculation with Glomus fasciculatum and Azotobacter chrococcum produces larger plants which have a larger leaf area. In addition, the plant vigour is improved with inoculation of Azospirillum on peach seedlings of cv. ‘Nemaguard’ as compared to control.
- The treatment also leads to increase in plant height, stem diameter, leaf number, plant dry weight and leaf area.
- Greatest percentage increase has been found in seedling height of mango, seedling diameter and number of leaves by treatment with 49 g N, Azotobacter + 48 g N, 32 g N or Azotobacter alone as compared to control.
- Both soil and foliar application of nitrogen in combination with Azotobacter increase the plant height, plant girth, the number of hands, bunches and the number of fingers/hand significantly in banana cv. ‘Robusta’.
2.6.2 Effect of biofertilizers on yield
- Significant increase in the bunch weight and yield of banana has been achieved with Azotobacter and organic manures supplements over 100% fertilizer.
- Azotobacter also enhances shooting and shortens crop duration.
- The application of Azospirillum + 150 kg/ha of N can increase the yield in strawberry by 54%, the number of fruits per plant and the clump weight compared to treatment with 150 kg N alone.
- The microbial inoculants in combination with inorganic manures have been shown to augment the yield and nutrient uptake in several crops.
- Application of biofertilizers (AzospiriIIum, phosphobacteria and VAMF) and organic manure (FYM) increase the bunch weight by 15.3 kg in hill banana var. Virupakshi along and with 75% NPK.
- Nitrogen-fixing bacteria improved the pseudostem circumference and the number of fingers/hand and advanced the flowering time in banana.
- Apple trees treated with phosphorene, active dry yeast and nitrobein at different concentrations showed effective improvement of fruit yield. The improvement was greatest with phosphorus biofertilizers.
- Increase in the number of fruits per plant, total weight of fruits and average fruit weight in strawberry as compared to the control has been achieved by the application of Azotobacter, Azospirillum and phosphate-solubilizing bacteria.
- The yield of sapota is greatly increased due to the application of 75 kg FYM
- 1500 g N + 1000 g P2O5 + 500 g K2O + 12.5 g PSB.
- The benefit–cost ratio is also high as compared to other fertilizer combinations. The inoculation of bacteria (Azotobacter chrococcum as a nitrogen fixer and bio-stimulant) along with N fertilizers between 80–100% favour banana development.
- The use of vermi compost, FYM and biofertilizers like Azotobacter, Azospirillum, VAM increase the production in citrus.
2.6.3 Effect of biofertilizers on soil characteristics
- Plants inoculated with Azotobacter and Azospirillum derive benefits in terms of enhancement in the uptake of NO3-, NH4+, H2PO4-, K+ and Fe2+, enhanced nitrate reductase activity in plants and production of antibacterial and antifungal compounds.
- The combined application of inorganic fertilizers and biofertilizers in banana cv. ‘Barjahaji’ significantly increases the available NPK status, organic C and microbial biomass and dehydrogenase activity in soil after harvest.
- VAM inoculation, either singly or in combination, significantly increases the root or shoot dry weight as well as the P-uptake over non-mycorrhizal treatments.
- Combined inoculation of Acaulospora calospora + G. mosseae + G. margarita and single inoculation of G. mosseae are superior in increasing the dry weight of ber seedlings as compared to other tested inoculation treatments.
- Application of VAM fungi in peach helps in better accumulation of Zn in their tissue.
- The quantities of beneficial microorganisms in the soil increase considerably due to the use of Azotobacter mycorrhiza and phosphorins in banana.
- The commercial yield is also increased by 25–30% and a 50% cut-back on the use of inorganic fertilizers is achieved.
2.6.4. Effect of biofertilizers on quality parameters
- The treatment combination of ¾ P + VAM + N is the best treatment for producing better growth and yield of high quality fruit. This treatment also influences the plant height, trunk diameter, canopy volume, root growth and biomass production as compared to control.
- The effect of biofertilizers (phosphorene, active dry yeast, rhizobacteria and nitrobein) on fruit set and productivity has been investigated on Red Roomy grape vines.
- The use of phosphorene has been found to improve the fruit set and yield as well as the physical and chemical properties of fruits compared to control.
- A fairly high TSS and reducing sugar content have been reported in fruits harvested from Azotobacter-inoculated banana plant cv. 'Giant Governor'.
- The effect of inoculation with Azospirillum and phosphobacteria on the fruit quality of banana (Musa MA) cv. ‘Giant Governor’ by manipulating the doses of nitrogen and potassium fertilizers has been studied. The results show that inoculation of biofertilizers along with application of the recommended dose of fertilizer proves most effective in improving the fruit quality of Dwarf Cavendish banana cv. ‘Giant Governor’.
- The plant growth, yield and fruit quality of strawberry are significantly increased with the application of biofertilizer and nitrogenous fertilizers.
- Maximum TSS content has been observed with Azotobacter inoculation along with 80 kg/ha of N. Inoculation to fruit plants has proved the possibility of curtailing about 50% P fertilizers without reducing the crop yield.
- Nitrogen-fixing biofertiIizers mainly Azospirillum and Azotobacter can fix 20–40 kg N/ha and produce growth-promoting substances like IAA.
- The use of microbial inoculants not only is a low-cost technology, but also takes adequate care of soil health and environmental safety.
Generally, the effect of biofertilizers on fruits and yield is not as striking as that of chemical fertilizers.