Green Farming: Dr. Avijit Kr. Dutta

Growing Vegetables under Changing Climate Scenario through Organic Farming

Dr. Avijit Kr. Dutta

Introduction

The climatic aberration accentuates agriculture to a highly challenging situation today and organic agriculture has the potential to mitigate such challenges. A significant amount of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) release into the atmosphere through agriculture with a tone of up to 10-12% of global anthropogenic greenhouse gas emissions annually, customarily methane from livestock raising, biomass burning as well as wet cultivation practices generally adopted in paddy farming, whereas, use of synthetic fertilizers leads to nitrous oxide production. Nitrogen (N) in soils and manures leads to N₂O formation during microbial transformation and the situation is often intensified particularly when available ‘N’ exceeds over the requirements of plants, most specifically under wet conditions (Smith and Olesen, 2010). It has been reported that the half of synthetic nitrogen fertilizer-related greenhouse gas emissions could occur in the production phases, while the other half arises from the soil (Tirado et al., 2010) via nitrification and de-nitrification processes (Firestone and Davidson, 1989). When secondary backings viz. land conversion to agriculture, fertilizer production and distribution, farm operations etc. are taken into consideration, then around 17-32% of global anthropogenic greenhouse gas emissions would be contributed by agriculture (Bellarby et al., 2008). Rising of temperatures, altering precipitation patterns and amplified CO₂ levels in atmosphere affect crop production (Long, 2012) with its further intensification towards biological variables like the crop lengths, growth periods and the crop cycle (Ye et al., 2012). Yield declines for the most important crops associated with the climate change phenomenon causing additional price escalations for most of the staples of the world viz. rice, wheat, maize and soybeans (Nelson et al., 2009). Vegetables are rich and cheaper sources of carbohydrates, protein, minerals and vitamins. They play important role in overcoming micronutrient insufficiencies as well as alleviating poverty to millions of people.  et al., 2002; Pimentel et al., 2005; Reganold et al., 2001) and organic agriculture continues function even under unexpected events of climatic disparity by increasing resilience within the agro-ecosystem (Borron, 2006). Resiliency to climate adversities in organic farming is closely linked with farm biodiversity and such enhance biodiversity of organic farming practices allow farms of its natural ecology that enables better respond to changing climate and thereby reduces the risk of harsh climate. For this reason, farmers who increase inter-specific diversity through organic agriculture suffer less damage compared to conventional farmers with monoculture practices (Borron, 2006; Ensor, 2009; Niggli et al., 2008).

Vegetable crops are highly sensitive to environmental indulgences and thereby unpredictable high temperature and uneven rainfall patterns disrupt the normal growth and development of these crops. The climate change is emerging as one of the major bottlenecks for world vegetable production. Therefore, the designing of an agricultural system with lower level of greenhouse gas emission technology which can adapts and responds to the variable climatic situations is a great challenge at present. In this backdrop, organic agriculture can play a vital role to compensate with such climatic vagaries. Best practices adopted in organic agriculture emit less greenhouse gases than conventional agriculture (Mader

Adaptation and mitigation potential of organic vegetables farming       

Organic farming practices have the potential to amend some of the main causes of climate change. The negative effects of drought can reduce through organic farming practices that restore soil fertility and maintain or increase organic matter content of farmland and thus increase productivity (Niggli et al., 2008). Water-holding capacity of soil is enhanced by organic practices that build organic matter, helping farmers withstand drought (Borron, 2006). Chemical fertilizers replacement through organic amendments, recycling of crop residues, incorporation of legume in crop rotations, crop diversification, avoidance of burning crop waste/residues as well as using more organic mulches, bio-inoculants and growth promoting substances of natural origin as vegetable production strategies can build up soil organic matter and offer sustainable carbon credits generation (Bellarby et al., 2008; Niggli et al., 2008a). The potential for generating carbon credits is mainly due to more use of compost, recycling of biomass waste for compost preparation etc. Much amount of carbon get fixed into a more stable form during the process of conversion of organic wastes into compost and the carbon is effectively confiscated that can reduce current global carbon emissions by as much as 10% (Liang et al., 2008; Woolf et al., 2010). In organic agriculture, the demand of nitrogen for crops can encounter through recycling of manures from livestock and crop residues via composting, as well as incorporation of leguminous crops in crop rotation cycles (ITC and FiBL, 2007). Management of crop residues in organic farming practices is a prime consideration and these crop residues are valuable sources of organic carbon besides several essential nutrients as well. It was estimated that tomato, cabbage, turnip residues contains 3.3, 3.6 and 2.3 percent nitrogen with C: N ratios of 12, 12 and 19, respectively (Gaur, 1999). Hence, a sizeable proportion of nutrient needs of agriculture, horticulture, forest and aquaculture can meet through appropriate recycling of a number of wastes and by-products (Tandon, 1995). Surface mulching with organic mulches can help to store more rain water in soil, increases infiltration and decreases evaporation. Such favourable changes in micro-climate reduce soil radiation, vapour pressure deficit and soil temperature (Singh et al., 2011). In the perspective of climate change, proper use of different mulching material helps to combat with the adverse climatic conditions and assures better yield and quality of produce. 

Carbon sequestration in soils through organic agriculture has maximum mitigation potential (Diacono and Montemurro, 2010) and better carbon sequestration can neutralize up to 40% of global greenhouse gas production (Rodale, 2008).

Incorporation of leguminous crops in the rotation is generally advised in organic crop production cycles that can increase soil microbial biomass (Kucey et al., 1988; Wani et al., 1991), improve soil structure (Latif et al., 1992) and increase water-holding capacity (Wani et al., 1994) besides fixation of atmospheric nitrogen into soils. Bio-fertilizers recommended in organic farming can broadly be categorized into three groups viz. nitrogen fixing, nitrogen fixing microorganisms on the basis of their nitrogen fixation mechanisms may be of two types such as symbiotic nitrogen fixer like Rhizobium (for legumes) and non- symbiotic nitrogen fixer or free living like Azotobacter and Azospirillum (for non-legumes); the second category i.e. the phosphate mobilizers convert the insoluble ‘P’ into soluble form and such microorganisms referred to as Phosphate Solubilizing Bio-fertilizers (PSB) and generally include several heterotrophic bacteria (Bacillus, Pseudomonas) and fungi (Aspergillus, Fusarium and Penicillium) and the third category comprises of some fungi that form symbiotic association with plant, called Mycorrhiza, and helps in the absorption of ‘P’, ‘Zn’, ‘Cu’ and ‘Fe’. Among these microorganisms, Vesicular Arbuscular Mycvorrhizae (VAM) fungi are most important that colonize various crop plants. These bio-inoculants suggested in organic farming can mitigate climatic vagaries in various ways. Under stress condition microbial inoculation with Azotobacter, Azospirillum and phosphate solubilizing bacteria produces indole acetic acid, gibberellins and other substances that promote the growth of root hairs and increase total root area of plant which in their turn facilitate nutrients uptake by plants and maintain normal growth (Klopper et al., 2004). Achromobacter piechaudii inoculation in tomato and pepper causes synthesis of ACC-deaminase which enhances salinity tolerance (Grover et al., 2011). Inoculation with Methylobacterium oryzae and Burkholderia sp. reduces nickel and cadmium stress in tomato by reducing their uptake and translocation (Madhaiyan et al., 2007). Tomato and pepper when inoculated with Achromobacter piechaudii ARV8, enhances ACC-deaminase synthesis which incur drought tolerance (Grover et al., 2011). Similarly, Pseudomonas putida, Enterobacter cloacae microorganisms help to synthesis of ACC-deaminase which emphasizes tomato to survive even under flooding situation (Grichko and Glick, 2001), Variovorax paradoxus, Pseudomonas sp. inoculated pea can survive under drought condition (Dodd et al., 2005; Arshad et al., 2008), Pseudomonas mendocina and Glomus intraradices inoculated lettuce showed drought tolerance by improving anti-oxidant status within the crop (Kohler et al., 2008).   

Conclusion

Agriculture should be redesigned in the era of climate change by proper utilization of resources through organic farming with intensive research, training and appropriate policy support for implementation of organic agriculture world-wide. Fluctuating environmental circumstances relentlessly affects agricultural productivity and increases vulnerability to the farming system. The organic farming practices have the potential to ameliorate some of the main causes of climate change. By adopting organic farming the soil carbon levels can be enhanced through carbon sequestration. Again through recycling of organic residues, incorporating legumes in crop rotation, crop diversification, the recycling and utilization of nutrients can be increased that will stimulate efficient utilization of resources and augment sustainability in the farming system under diverse climatic condition to combat emerging climate changes of the world. Above all, organic agriculture approaches are furthermore accessible to small-scale and resource poor farmers as well who depend on locally available resources for their agricultural production.

References

Arshad, M.; Sharoona, B. and Mahmood, T. (2008). Inoculation with Pseudomonas spp. containing ACC deaminase partially eliminate the effects of drought stress on growth, yield and ripening of pea (Pisum sativum L.). Pedosphere, 18:611- 620.

Bellarby, J.; Foereid, B.; Hastings, A. and Smith, P. (2008). Cool farming: Climate impacts of agriculture and mitigation potential. Greenpeace International, Amsterdam (NL), p. 44.

Borron, S. (2006). Building resilience for an unpredictable future: How organic agriculture can help farmers adapt to climate change. FAO, Rome, Sustainable Development Program.

Diacono, M. and Montemurro, F. (2010). Long-term effects of organic amendments on soil fertility. A review. Agronomy for Sustainable Development, 30: 401-422.

Dodd, I.C.;  Belimov, A. A.; Sobeih, W. Y.;  Safronova, V. I.; Grierson,  D. and Davies, W. J. (2005). Will modifying plant ethylene status improve plant productivity in water-limited environments? 4^th International Crop Science Congress. Retrieved from http://www.cropscience.org.au/ icsc2004/poster/1/3/4/510_doddicref.html.

Ensor, J. (2009). Biodiverse agriculture for a changing climate. Practical Action, UK.

Firestone, M.K. and Davidson, E.A. (1989). Microbiological basis of NO and N₂O production and consumption in soils. In: Andreae, M.O. and Schimel, D.S. (Eds.), Exchanges of Trace Gases between Terrestrial Ecosystems and the Atmosphere. John Wiley & Sons, New York.

Gaur, A.C. (1999). Microbial technology for composting of agricultural residues by improved methods. ICAR publication, New Delhi, p.78.

Grichko V. P. and Glick, B. R. (2001). Amelioration of flooding stress by ACC deaminase containing plant growth promoting bacteria. Canadian Journal of Microbiology, 47:77-80.

Grover, M.; Ali, S.Z.; Sandhya, V.; Rasul, A. and Venkateswarlu, B. (2011). Role of microorganisms in adaptation of agriculture crops to abiotic stresses. World Journal of Microbiology and Biotechnology, 27: 1231-1240.

ITC (International Trade Centre UNCTAD/WTO) and FiBL (Research Institute of Organic Agriculture). (2007). Organic farming and climate change. ITC, Geneva.

Klopper, J.W.; Ryu, C.M. and Zhang, S. (2004). Induced systemic resistance and promotion of plant growth by Bacillus spp. Phytopathology, 94: 1259-1266.

Kohler, J.; Herna´ndez, J. A.; Caravaca, F. and Rolda´n, A. (2008). Plant growth promoting rhizobacteria and arbuscular mycorrhizal fungi modify alleviation biochemical mechanisms in water stressed plants. Functional Plant Biology, 35:141–151.

Kucey, R.M.N.; Chaiwanakupt, P.; Arayangkool, T.; Sintwongse, P.; Siripaibool, C.; Wadisirisuk, P. and Boonkerd, N. (1988). Nitrogen fixation (15N dilution) with soybeans under Thai field conditions. II. Effect of herbicides and Water application schedule. Plant and Soil, 108: 87-92.

Latif, M.A.; Mehuys, G.R.; Mackenzie, A.F.; Ali, L. and Faris, M.A. (1992). Effects of legumes on soil physical quality in a maize crop. Plant and Soil, 140: 15-23.

Liang, B.; Lehmann, J.; Solomon, D.; Sohi, S.; Thies, J.E.; Skjemstad, J.O.; Luizao, F.J.;  Engelhard, M.H.; Neves, E.G. and Wirick, S. (2008). Stability of biomass derived black carbon in soils. Geochimica et Cosmochimica Acta, 72: 6096-6078.

Long, S. P. (2012). Virtual Special Issue on food security-greater than anticipated impacts of near-term global atmospheric change on rice and wheat. Global Change Biology, 18:1489–1490.

Mader, P.; Fliessbach, A.; Dubois, D.; Gunst, L.; Fried, P. and Niggli, U. (2002). Soil fertility and biodiversity in Organic Farming. Science, 296: 1694-1697.

Nelson, G.C.; Rosegrant, M. W.; Koo, J.; Robertson, R.; Sulser, T.; Zhu, T.; Ringler, C.; Msangi, S.; Palazzo, A.; Batka, M.; Magalhaes, M.; Valmonte-Santos, R.; Ewing, M. and Lee, D. (2009). Climate change impacts on agriculture and costs of adaptation. Res. Report, International Food Policy Res. Institute, Washington DC., p. 30.

Niggli, U.; Fliessbach, A. and Hepperly, P. (2008). Low Greenhouse Gas Agriculture: Mitigation and Adaptation Potential of Sustainable Farming Systems. FAO, Rome.

Niggli, U.; Schmid, H. and Fliessbach, A. (2008a). Organic Farming and Climate Change. International Trade Centre (ITC), Geneva, Switzerland, p.30.

Pimentel, D.; Hepperly, P.; Hanson, J.; Douds, D. and Seidel, R. (2005). Environmental, energetic and economic comparisons of organic and conventional farming systems. Bioscience, 55(7): 557-582.

Reganold, J. P.; Glover, J. D.; Andrews, P.K. and Hinman, H. R. (2001). Sustainability of three apple production systems. Nature, 410: 926-930.

Rodale (2008). Farm Systems Trial, The Rodale Institute, 611 Siegfriedale Road, Kutztown, PA 19530-9320.

Singh, A.; Singh, D.; Kang, J. S. and Aggarwal, N. (2011). Management practices to mitigate the impact of high temperature on wheat: a review. The IIOAB Journal, 2(7): 11-22.

Smith, P. and Olesen, J. E. (2010). Synergies between the mitigation of, and adaptation to, climate change in agriculture. Journal of Agricultural Science, 148: 543–552.

 Tandon, H. L. S. (1995). Recycling of crop, animal, human and industrial wastes in agriculture. Technical Bulletin. Fertilizer Development and Consultation Organization. New Delhi, India.

Tirado, R.; Gopikrishna, S. R.; Krishnan, R. and Smith, P. (2010). Greenhouse gas emissions and mitigation potential from fertilizer manufacture and application in India. International journal of Agricultural Sustainability, 8: 176–185.

Wani, S. P.; McGill, W. B. and Robertson, J. A. (1991). Soil N dynamics and N yield of barley grown on Breton loam using N from biological fixation of fertilizer. Biology and Fertility of Soils, 12: 10-18.

Wani, S. P.; McGill, W. B.; Haugen-Kozyra, K. L.; Robertson, J. A. and Thurston, J. J. (1994). Improved soil quality and barley grown on Breton loam using N from biological fixation or fertilizer. Biology and Fertility of Soils, 12: 46-54.

Woolf, D.; Amonette, J. E.; Street-Perrott, F. A.; Lehmann, J. and Joseph. S. (2010). Sustainable biochar to mitigate global climate change. Nature Communications, 1: 56.

Ye, L.; Xiong, W.; Li, Z.; Yang, P.; Wu, W.; Yang, G.; Fu, Y.; Zou, J.; Chen, Z.; Van Ranst, E. and Tang, H. (2012). Climate change impact on China food security in 2050. Agronomy for Sustainable Development, doi: 10.1007/s13593-012-0102-0.

                             ***********************************************

 Dr. Avijit Kr. Dutta. Assistant Professor (Horticulture), School of Agriculture and Rural Development F/C: IRTDM, Ramakrishna Mission Vivekananda University