Liyanage, M. De S.

Coconut Research Institute Repository

U S E S A N D M A N A G E M E N T O F N I T R O G E N F I X I N G T R E E S I N C O C O N U T P L A N T A T I O N S Low productivity and poor returns from a unit of coconut land coupled with price instability of the coconut crop have threatened the sustainability of coconut plantations in Sri Lanka. Over the past three decades, coconut-based farming systems have been introduced by the CRI, for the purpose of increasing land produc­tivity and generating ad­ditional income to the co­conut farmer. M de S Liyanage Coconut Research Institute of Sri Lanka erate rainfall to increase productivity and ac­crue several benefits to the farmer. On fertile soils with favourable climate, farmers are encouraged to grow high value cash crops with a ready market such as Pineapple, Ba­nana, Pepper, Ginger, Be­tel, Cinnamon etc. Nitro­gen Fixing Tree (NFT) species have been intro­duced to areas where these cash crops will not perform well especially on degraded marginal land with less favourable climate such as those in the intermediate and dry zone.(mainly land suitability classes 4 and 5) Since 1987, CRI has attempt^ to grow several nitrogen fixing trees (NFT s) such as Gliricidia sepium, Calliandra callothyrsus, Leucaena leucocephala and Acacia auriculiformis, with the main objective of uti­lizing such marginal coconut land with mod-Figure 1.Gliricidia cultivated in between coconut rows Factors to be considered in selecting NFT s * Compatibility with coconut * Tolerance to partial shade * Ability to grow on degraded soils * Optimum biomass production under cocon­ut shade * Ability to withstand repeated pruning * Good coppicing ability * Use minimum external inputs (eg. fertilizer, pesticides) 4 * Compatibility with coconut The effect of fast growing tree species on coconut yield is an important aspect to be considered in promoting their adoption in co­conut plantations. Data collected over five years have revealed that despite non applica­tion of fertilizer and water to NFT s, there was no detrimental effect on the palm, compared to control blocks. Among species, all except Leucaena showed an improvement in the yield of coconut in the range of 15-20%. * Tolerance to partial shade mass productivity in NFT s could be achieved by pruning trees 1.0 m above ground at 3-4 monthly intervals. For instance.gliricidia is capable of producing 10-15 mt of fresh loppings per year from one hectare of coco­nut land. * Ability to grow on degraded land NFT species have established well and continue to produce satisfactory biomass with­out fertilizer on Andigama soil series which is considered marginal for coconut due to poor physical characteristics of the soil. It has been shown that among NFT s the least reduc­tion of biomass yield under reduced light occurred in Gliricidia (23%) followed by Calliandra whereas biomass of Leucaena was reduced most (56%) by low light, suggesting that it is less shade tolerant. Of all NFT species, Gliricidia has shown to be the most compat­ible species that could be grown in associa­tion with coconut. Figure 2.Use of Gliricidia leaves as green manure * Optimum biomass production under co­conut shade Optimum biomass production can be achieved by tree management. Frequency and height of pruning are important aspects in tree management. Experience has shown that highest bio-* Use of minimum external inputs This is a clear advantage of NFT s as other crops will not perform well without the application of fertilizer and pesticides. These trees have the ability to meet their own nutri­ent requirement by foraging through the soil profile, biological nitrogen fixation and they 5 are practically free of pests and diseases. * Ability to withstand repeated pruning Despite NFT species have been sub­jected to pruning 3-4 times a year and this pro­cess has been re­peated for five c o n s e c u t i v e years,trees con­tinue to perform well and remain productive over the years. requirement of the coconut palm, thus provid­ing about 40% saving on the cost of fertilizer. It will also provide a regular supply of micro-nutrients to the palm. * Coppicing ability The abil­ity of NFT s to produce new shoots after each pruning is re­ferred to as coppicing ability. All NFT s have shown their ability to produce coppice shoots after pruning. Among NFT species, Gliricidia, Calliandra and Acacia have shown better coppicing ability. ROLE OF NFT' S IN COCONUT PLAN­TATIONS * Use of fresh biomass as green manure Figure 3.Gliricidia foliage as animal fodder * Use of fresh biomass as mulch Of the NFTs. prunings of Acacia fol­lowed by Calliandra have shown a greater promise to serve as a surface mulch. With all species, mulching has shown a better effect against bare soil, in terms of moisture conser­vation ability, soil temperature regulation, and weed suppression. Of the NFT species, Gliricidia and Leucaena foliage is particularly rich in nitrogen. It has been shown that application of 35 kg fresh Gliricidia loppings could satisfy the total re­quirement of N and at least 20%' of P and K * Use of fresh biomass as animal fodder Mixing of poor quality grass or rice straw with Gliricidia and Leucaena foliage up to about 30% of the total feed will provide a balanced ratio for livestock, especially dur-6 ing the dry period. Feeding with high protein supplements has given rise to improved intake, better digestibility and weight gains of rumi­nant livestock. Acacia leaf is commonly fed to goats. * Restore and improve soil fertility NFT species have a special ability to grow on marginal lands and improve soil physical, chemical and biological properties, there by improving the productivity of soil and facilitating better growth and yield of coco­nut palms. * UseofNFT's as temporary shade In new plantations, species like Gliri­cidia and Leucaena have been grown together with coconut seedlings to provide temporary shade.especially in dry areas to provide a favourable microclimate for initial establish­ment and growth up to about 3 years from planting. * Use of NFT's as live support Of the NFT's Gliricidia is widely used as a live support for Pepper and Vanilla grown together with coconut. Application of Glricidia loppings arround Pepper could reduce the fer­tilizer requirement of Pepper by about 50%. Considering the easy management and the potential use of NFT's, it is profitable to grow them, especially on marginal coconut lands. / i Specialist Assistance to Develop your Plantation The Coconut Research Institute implements programme known as "Persuasive Extension Programme" to assist coconut growers to develop their plantations with the adoption of new technology. In this programme a group of scientists and extensionists of the Institute meet land owners in their plantations and draw up suitable develop­ment plans in consultation with land owners. In this exercise land owners have an opportunity to discuss their problems and limitations and decide on future development activities. Officers from this institute continue to assist them in the implementation of the proposed development plan and monitor the progress. This is a valuable opportu­nity for growers who wish to improve the productivity of their plantations. If you wish to register to obtain this service, please write to Director, Coconut Research Institute, Lunuwila, Sri Lanka. 7 

Uses and management of nitrogen fixing trees in coconut plantations

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Uses and management of nitrogen fixing trees in coconut plantations

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