The Role of Soil Organisms and Functions in different Coconut based Multiple Cropping Systems
Abstract
Sampling was done in wet and intermediate zones represented by the Walpita and Makandura research centers, respectively. Eleven land use systems were considered for the study; coconut mono culture (CM), bare land (BL) and coconut multiple cropping. Under coconut multiple cropping, nine different intercrops were selected separately for each zones. The treatments were arranged in a randomized complete block design (RCBD) with three replicates (n = 3). The experiment was conducted under mature baring coconut ( >20 years) plantation. Soil Macrofauna was sampled using one transect with three replicates at each land use type using quadrate size (30×30cm) from 0 -30 cm depth and visible organisms were handpicked and preserved in 75% alcohol. Dilute plate technique an d Spread plate technique was used to determine the soil micro organisms’ density. Those techniques were used to cultivate the fungi and bacteria under 10−2 and 10−5 dilution level respectively.
Research identified 12 classes (Crusteacea, Oligochaeta, Hirudinea, Gastropoda, Acarina, Araneida, Scopionida , Chilapoda , Diplopoda , Amphibia, Repteli a) and 14 orders (Hemiptera, Diptera, Coleoptera, Thysanura , Hymenoptera , Lepidotera , Orthoptera , Blattaria , Mantodea , Phasmida , Dermaptera , Isoptera , Siphonaptera , Thysanoptera) of soil organisms. Class insecta shows the high diversity with 14 orders. Colony forming unit (CFU) value of bacteria was higher than that of the fungi value. Findings of intermediate and wet zones’ studies suggested that coconut multiple c ropping systems may have high diversity, abundance and functional role of soil organisms. Both zones studies suggested that coconut multiple cropping systems may increase soil moisture factor, respiration rate, biomass carbon content, organic carbon percen tage, total nitrogen content, organic matter content and C:N ratio in 0-30cm depth other than the coconut monoculture systems. Overall data of two different zones indicated a significant positive correlation of soil organism diversity, abundance and their functional role with cropping system s. Those data can be used as a reliable basic bio indicator for payments for ecosystem services (PES) . It support s to valorize the economic value of the ecological services returned by soil organisms.
Keywords
Download Options
Introduction
Coconut (Cocos nucifera L.) is one the most important crops grown in the humid tropics (Adkins et al., 2005). Extent of lands under coconut cultivation in Sri Lanka which is the fourth of world’s coconut cultivation is about 394,836 hectares and it is about 20% out of the total cultivated extent of land in the country (CDA, 2006).
Soil organisms are an integral part of agricultural ecosystems (Nuria et al, 2008). These organisms may range from large animals and plants to microscopic bacteria (Davari et al., 2010). Presence of diverse community of soil organisms is essential for the maintenance of fertile soils and productive lands for agriculture and forestry. Soil organisms are responsible for a range of ecological functions and ecosystem services including: nutrient cycling and nitrogen fixation, control of pest and diseases, organic matter decomposition and carbon sequestration, maintenance of a good soil structure for plant growth, rainwater infiltration, and detoxification of contaminants (Nuria et. al., 2008).
Ecosystem services are the services provided by the natural environment to benefit both people and other organisms. Payments for ecosystem services (PES) can be essentially defined in terms of payments to land managers or owners to undertake actions that increase the levels of desired ecosystem services (Helen, 2011). More formal definition is ‘‘A PES scheme, simply stated, is a voluntary, conditional agreement between at least one ‘seller’ and one ‘buyer’ over a well defined environmental service or a land use presumed to produce that service” (Wunder, 2005).
However, one of the main gaps in agricultural management systems is the lack of awareness and understanding and hence inadequate management of soil biological processes to maintain and improve soil productivity. A major focus is placed on soil macrofauna, the visible part of the surprisingly rich soil life, and its activities in agricultural soils, as this is, firstly, reasonably representative of soil biodiversity as a whole (including micro and meso-organisms and populations) and, secondly, is the part of soil life that can be readily observed and monitored in terms of effects of various management practices (Nuria et al, 2008).
The organisms (or biota) are a major factor in soil formation and their effects determine many differences between soils. The various soil organisms affect certain soil processes in different ways (Nuria et al., 2008). Soil organisms play a vital role in soil ecosystems and their presence to sustain a healthy soil (Darwin, 1881).
Soil organisms are an integral part of agricultural ecosystems. The presence of a range of a diverse community of soil organisms is essential for the maintenance of productive soils. Soil organisms are responsible for a range of ecological functions and ecosystem services including: nutrient cycling and nitrogen fixation, control of pest and diseases, organic matter decomposition and carbon sequestration, maintenance of a good soil structure for plant growth and rainwater infiltration, detoxification of contaminants. An excessive reduction in soil biodiversity, especially the loss of species with key functions, may result in severe effects including the long term degradation of soil and the loss of agricultural productive capacity (Nuria et al, 2008). Presence of soil organisms is beneficial to agro ecosystems (Edwards and Fletcher, 1988; Lavelle, 1988; Lavelle et al, 1997; Edwards, 1998; Eriksen and Whalen, 2007).
Soil ecologists are still completing the taxonomy and systematic of soil organisms, revealing life history strategies, and just beginning to understand relationships between organisms and their contribution to ecosystem function (Crossley et al., 1992). One exception is that of earthworms and nitrogen fixing bacteria whose relationship to ecosystem function has been known for decades. This apparent lack of knowledge does not, however, diminish the importance of soil organisms (Neher, 1999).
Mesofauna occupy all trophic levels within the soil food web and affect primary production directly by root feeding and indirectly through their contribution to decomposition and nutrient mineralisation (Crossley et al., 1992).
Bio diversity, soil quality and sustainability are considered to be the factors in ecosystem payment. Diversity and abundance of soil organisms that contribute to the bio diversity and their functions are contributed to the soil quality.
The ecosystem assessment will be based on the information diversity and abundance of the soil organisms. Ecosystem assessment can be used to select the most suitable cropping system for particular micro climatic conditions and it is essential for ecosystem payment. In Sri Lanka basic studies have not been done to exploit the ecosystem payment schemes. Therefore this is important to ecosystem assessment and the payment.
Conclusion
Cropping systems have significant impact on soil organism diversity and abundance due to variability of soil quality. Soil organisms diversity, abundance and functional role was > multiple cropping system > coconut monoculture land and lowest at bare land. Multiple cropping system soil was more productive in term of soil organisms’ density and diversity due to high bio mass carbon, SOC, SOM, TN, C : N ratio, litter, and root bio mass content. So multiple cropping systems having the rich ecosystems than coconut monocropping system and bare land. According to this study cocoa + coconut multiple cropping systems represent the richest eco system because it has thick cocoa leaf layer under the crops. Those data can be used as a reliable basic bio indicator for payments for ecosystem services (PES) .
