Organic nutrients management techniques to raise coconut
By Our Agriculture Correspondent
Incorporation of green leaf manure in the basins is an important aspect in ensuring organic nutrient supply to coconut palms.
COCONUT RESPONDS to organic nutrients well, and a number of practices to grow coconut through organic pathway have been developed at the Central Plantation Crops Research Institute (CPCRI), Kasaragod, Kerala.
According to Dr. George V. Thomas, Head of Crop Production division at CPCRI "one among the important means of organic nutrient supply is growing leguminous green manure plants for sustaining coconut yields. Leguminous cover crops grown in the coconut plantations during the rainy season will protect the soil from direct impact of heavy rains and serve as catch crops. The nitrogen-rich green matter will decompose easily and release the bound nutrients fast".
Leguminous green manure plants, either seasonal or perennial types can add a lot of green matter rich in nitrogen to soil in shortest time because of their ability to associate with atmospheric nitrogen-fixing bacteria, Rhizobium spp. Incorporation of legume biomass has also been found to enhance soil microbial population, population of Vesicular Arbuscular Mycrorrhiza (VAM), soil enzyme activity and carbon mineralization, according to him.
Legume cover crops grown in basins can generate about 15 to 20 kg green biomass per basin and legumes such as Crotalaria spp. grown in the interspaces can generate 3 to 4 tonnes of green biomass per hectare. The perennial green manure plant, Gliricidia is very fast growing, hardy and resistant to regular harvesting of green leaves.
This plant can be grown along the borders of coconut plantations and can help in generating huge quantities of nitrogen-rich green leaf manure.
Application of Gliricidia prunings could help in meeting a major portion of nitrogen, and a part of phosphorus and potassium demand of coconut trees.
Besides, a number of organic wastes from the coconut palm can be effectively recycled to make good compost, which will meet much of the nutrient demands of the coconut trees. Most of the organic wastes from coconut have high moisture holding capacity and can be profitably used as moisture regulators and conservers rather than nutrient sources.
Coconut husks and coir pith can be buried in the trenches in between the rows of palms.
Coir pith has 400 to 600 per cent water holding capacity and this technique will be of immense value in the long-term moisture conservation. In addition, both these materials are rich in potash and would be available to the plants over the years, according to Thomas.
CPCRI has also developed a low-cost vermin-composting technique for converting the biomass from the coconut trees using earthworms of Eudrilus species.
This technology may be tried even in plantations with limited irrigation facilities, as only a limited number of pits or trenches will need to be watered.
In coconut plantations with irrigation facilities, vermin-composting can be done in basins and palms can directly get the benefits.
The average nutrient composition of the vermi-compost is 1.8 per cent nitrogen, 0.216 per cent phosphorus and 0.16 per cent potassium.
The organic carbon content is 17.84 per cent and the carbon-nitrogen ratio is 9.95.
The total microbial counts and beneficial microbes population are also more in the vermin-compost than the base material.
Two types of active nitrogen-fixing bacteria, not commonly isolated from the soils, are found regularly associated with vermin-casts, according to Dr. Thomas. Vermi-compost contains nutrients in easily available forms, in addition to a number of plant growth promoting substances and humic acids.
Being granular and less bulky, it can be easily transported and incorporated into the fields, he says.
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