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How to Reduce Chemical Fertilizer? Way forward for sustainable crop production

14 September 2015 06:30 pm - 0     - {{hitsCtrl.values.hits}}

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Human activities worldwide have been   recognised as the principal contributor to environmental pollution and   climate change that is driving global biodiversity towards extinction. The   alarming increase in the oceanic dead zones during the past few decades is a   clear indicator of this trend. Among the major causes attributed to such   pollution is the widespread use of chemical (reactive) fertilizers. A   resolution has been passed at the 2012 UN Conference on Environment and   Development (Rio + 20) to reduce the use of chemical fertilizer by 20% by the   year 2020.  

The use of chemical (synthetic)   fertilizer is a standard practice in modern -day high input agriculture. Such   inputs without doubt boosted food production to meet the growing demand of an   increasing world population and ward off large sale-starvation. Nonetheless,   continuous and indiscriminate use of chemical fertilizers often in excess of   requirements has not only made food production too costly (particularly for   developing countries) but also increased environmental pollution to alarming   levels and directly contributed to the aggravation of environmental health   problems. The UN publication Global, Environmental Year Book 2003,   stated that more than 160 million metric tons of N-fertilizer ends up in the   oceans annually and this has doubled the ocean’s dead zones (anoxic areas   without aquatic life) since 1990. A more recent publication UNEP Year Book   2014 states that the 150 dead zones reported in 2003 have now increased to   500 dead zones! Usually such dead zones are located near coastal areas   associated with high anthropogenic activities and large effluent discharges   to the oceans including fertilizer wash-offs.

 For example, the Mississippi   River basin in Central US drains runoff from the agricultural heart of   the North American continent and this nutrient-laden runoff is released into   the Gulf of Mexico where a plume of algae and plankton grows explosively. The   decomposing organic debris from the plume consumes so much dissolved oxygen   that 20,000 km2 of the Gulf becomes hypoxic (unable to   support life) each summer. This is the ‘Gulf dead zone’.  More recently (May 13, 2015) a team of   German and Canadian marine biologists has witnessed for the 1st time a dead   zone  even in the deep mid Atlantic   Ocean, indicating that dead zones could spread even to deeper waters.  

In Sri Lanka Dr. Sarath Amarasiri (a   former Director-General of Agriculture) has recently published a book Caring   for Water in which he describes how excessive application of phosphate   fertilizer has significantly increased the P content of four major irrigation   reservoirs in the North Central Province where an alarming increase of   chronic kidney disease of uncertain etiology is prevalent, particularly among   the farming communities. Furthermore it is stated that such P loading leads   to the eutrophication of these water bodies resulting in the formation of   toxin-producing cyanobacterial (algal) blooms. Therefore it has become   imperative that efforts are directed towards the reduction of chemical   fertilizer use without compromising on crop yields. 

The resolution made by world leaders at   the (Rio + 20) conference to reduce the annual use of chemical fertilizer by   20% by 2020 that could save US$ 50 – 400 billion per year in terms of   improvement to human health, climate and biodiversity. It has also been   reported that the value of nitrogen fixed annually by legumes in Australia is   equivalent to three billion Australian dollars. 

Therefore both on economic and ecological   considerations it has become imperative that we look for alternative inputs for   agriculture and food production without compromising on crop yields. This has   renewed interest in the efficient use of organic matter including the   re-cycling of crop residues and enhancement of natural processes such as   biological nitrogen fixation, improving phosphorus uptake through mycorrhizae   and increasing beneficial root associated microorganisms of agricultural and   pasture crops. However, it should be realized that microorganisms play a   critical and vital role in all these alternatives to reduce the use of   chemical fertilizers. This article reveals studies so far carried out at the   National Institute of Fundamental Studies (NIFS), Kandy on research and   development of microbial inoculants for crop production and their potential   in minimizing the application of chemical fertilizers in Sri Lanka.



Rhizobial biofertilizer 
The status of soil microbiology in crop   production in Sri Lanka is rather infantile compared to studies conducted in   many other countries. An attempt to introduce rhizobial inoculant technology   for soybean (Glycine max) cultivation in Sri Lanka through a FAO/UNDP   project (1976 - 1984) did not continue beyond the project period due to the   absence of a low cost, locally available carrier material for transport and   storage of inoculants under farmers’ conditions. This limitation was overcome   by the findings at the NIFS in 1999 of the suitability of modified coir dust   as a carrier material. This breakthrough enabled the field testing and   eventual introduction of inoculants to soybean farmers in 2007. Today around   10,000 acres of soybean is cultivated per season with coir dust -based   rhizobial inoculants prepared by the NIFS that can completely replace the use   of urea fertilizer.
 
Inoculants for vegetable beans (Phaseolus   vulgaris) and mung bean (Vigna radiata) have given positive   results and these are about to be released to farmers. Formulation and   initial testing of inoculants for cowpea (Vigna unguiculata) and   groundnut (Arachys hypogea) are in progress.  

Another area of research that has   commenced for the 1st time in Sri Lanka is the formulation and field testing   of rhizobial inoculants for pasture legumes.    
Studies carried out during the last one   year have shown the potential of these inoculants to replace the application   of urea completely to white clover (Trifolium repens) at  Ambewela   Farms, Ambewela. These studies are currently being repeated to establish their   reproducibility prior to formulating recommendations.  



Bio-film Biofertilizers 
Rhizobial inoculants can replace only   nitrogen fertilizer and they are also confined to leguminous food and pasture   crops. However there are a number of non-leguminous crops including cereals   (vital to national nutrition) on which large amounts of synthetic fertilizers   (N, P, & K) are used. Besides rhizobia, mycorrhizae are used to enhance   phosphorus uptake by plants and microbial preparations are sometimes used as   bio-control and soil conditioning agents. Such usage of microorganisms is not   yet practised on an agronomic scale in Sri Lanka.  

Studies conducted during the past decade   at the NIFS led to the development of inoculants of microbial communities or   microbial consortia which were introduced to the world for the first time as Biofilm-Biofertilizers   (BFBFs).  

They were found to be more effective than   conventional biofertilizers.  Application   of BFBFs together with low levels of chemical fertilizers has been field -tested on a number of crops in several locations and found to be able to   replace 50% of all three (N, P & K) chemical fertilizers in tea, rice,   maize and a number of vegetables without compromising on their yields. 

 These field trials have confirmed that   consortia of beneficial microorganisms improve nutrient uptake by plants   through increased root growth and activity, rhizoremediation, soil moisture   conservation, reduced transpiration and re-establishment of beneficial   rhizosphere microbial communities.  

Realizing its responsibility in   mitigating environmental health problems due to the indiscriminate use of   chemical fertilizers, the Government of Sri Lanka has renewed its interest in   the development of alternative sources of nutrient supplies for crops. Among   them the preparation and widespread application of compost is being   popularized, with the President of Sri Lanka playing a lead role in this new   venture. It should however be realized that the application of compost may   not have the expected impact on the yields of short-term crops like major   cereals (including rice), food legumes and vegetables because the release of   plant nutrients after decomposition is too slow to meet the immediate demand   of such crops. Nevertheless, recent research studies done in other countries (particularly in East Asia)   have produced microbial inoculants aptly termed as Effective Microbial   Inoculants (EMIs) that could accelerate the decomposition of organic matter   including compost. It is imperative that similar studies on research and   development of local EMIs be undertaken as a priority in order to achieve   targeted sustainable, eco-friendly crop production which can minimize the use   of chemical fertilizers.    
  
Considering all these recent research and   developments and the importance of the application of soil microbial   biodiversity in food production in Sri Lanka, it has been proposed to set up   a National Culture Collection of Microorganisms at the NIFS as a repository   of microbial germ plasm that will be available for all microbiological   research and development activities. It is the responsibility of the new   government to use these innovative discoveries to combat chemical   fertilizer in Sri Lanka to save the suffering people and the polluted environment   of the country.  


This article was compiled by Pradeep   Piyathilaka, Communication & Media Officer, Science education &   Dissemination Unit, National Institute of Fundamental Studies, Kandy after   interviewing Prof.S.A.Kulasooriya, Research Scientist, NIFS.   
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