Soil Fertility Advantages of Submerged Rice Cropping Systems

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<ul><li><p>This article was downloaded by: [George Mason University]On: 10 July 2014, At: 02:36Publisher: Taylor &amp; FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK</p><p>Journal of SustainableAgriculturePublication details, including instructions forauthors and subscription information:</p><p>Soil Fertility Advantages ofSubmerged Rice CroppingSystemsK. L. Sahrawat aa Soil Chemistry Laboratory , International CropsResearch Institute for the Semi-Arid Tropics (ICRISAT) , Patancheru 502 324, Andhra Pradesh, IndiaPublished online: 20 Nov 2008.</p><p>To cite this article: K. L. Sahrawat (2008) Soil Fertility Advantages of SubmergedRice Cropping Systems, Journal of Sustainable Agriculture, 31:3, 5-23, DOI: 10.1300/J064v31n03_03</p><p>To link to this article:</p><p>PLEASE SCROLL DOWN FOR ARTICLE</p><p>Taylor &amp; Francis makes every effort to ensure the accuracy of all theinformation (the Content) contained in the publications on our platform.However, Taylor &amp; Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor &amp; Francis. The accuracy of theContent should not be relied upon and should be independently verified withprimary sources of information. Taylor and Francis shall not be liable for anylosses, actions, claims, proceedings, demands, costs, expenses, damages,and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of theContent.</p><p></p></li><li><p>This article may be used for research, teaching, and private study purposes.Any substantial or systematic reproduction, redistribution, reselling, loan,sub-licensing, systematic supply, or distribution in any form to anyone isexpressly forbidden. Terms &amp; Conditions of access and use can be found at</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Geo</p><p>rge </p><p>Mas</p><p>on U</p><p>nive</p><p>rsity</p><p>] at</p><p> 02:</p><p>36 1</p><p>0 Ju</p><p>ly 2</p><p>014 </p><p></p></li><li><p>RESEARCH, REVIEWS, PRACTICES,POLICY AND TECHNOLOGY</p><p>Soil Fertility Advantagesof Submerged Rice Cropping Systems:</p><p>A Review</p><p>K. L. Sahrawat</p><p>ABSTRACT. Wetland rice production systems in Asia are making amajor contribution to the global rice supply. Wetland rice cultivation isoften cited as an example of a sustainable cropping system. Wetland orpaddy rice growing involves land preparation by cultivating in theflooded or saturated state (puddling), followed by transplanting of seed-lings in soils under submerged condition and growing of the crop untiltwo to three weeks before harvest. In other rice-based cropping systems,the land is either dry- or flood-fallowed during the period between twocrops. Afterwards, two or three crops of rice are grown in submerged soilcondition. However, shortage of freshwater is becoming critical for thistraditional lowland rice cultivation. Obviously, there is high potential inexploring rice cultivation under moisture regimes that save water and</p><p>K. L. Sahrawat is affiliated with Soil Chemistry Laboratory, International CropsResearch Institute for the Semi-Arid Tropics (ICRISAT), Patancheru 502 324, AndhraPradesh, India.</p><p>Address correspondence to: K. L. Sahrawat at the above address (E-mail:</p><p>Journal of Sustainable Agriculture, Vol. 31(3) 2007Available online at</p><p> 2007 by The Haworth Press. All rights reserved.doi:10.1300/J064v31n03_03 5</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Geo</p><p>rge </p><p>Mas</p><p>on U</p><p>nive</p><p>rsity</p><p>] at</p><p> 02:</p><p>36 1</p><p>0 Ju</p><p>ly 2</p><p>014 </p><p></p></li><li><p>also increase productivity. Such a situation provides an opportunity tocritically analyze the fertility benefits of submerged rice cropping sys-tems that would help facilitate in making a practical and right choice forgrowing of rice in future. The objective of this paper is to highlight theunderlying principles, which govern the fertility advantages to submergedrice cropping systems. The advantages of growing rice in submergedsoils include a general amelioration of chemical fertility, preferential ac-cumulation of organic matter and improved availability of major, sec-ondary and selected micronutrients. These soil fertility advantages benefitthe long-term maintenance of soil fertility and sustainability of wetlandrice systems. The paper emphasizes the potential of growing wetland ricein monsoon Asia, specifically in poorly drained, waterlogging-prone ar-eas where the water table is shallow (within 30 cm of the soil surface).doi:10.1300/J064v31n03_03 [Article copies available for a fee from The HaworthDocument Delivery Service: 1-800-HAWORTH. E-mail address: Website: 2007 by TheHaworth Press. All rights reserved.]</p><p>KEYWORDS. Aerobic rice and sustainability, amelioration of chemi-cal fertility, lowland rice sustainability, organic matter accumulation,poorly drained soils, soil submergence and nutrient availability</p><p>INTRODUCTION</p><p>Wetland rice production systems in Asia are making a major contribu-tion to the global rice supply (Cassman and Pingali, 1995). The wetlandrice system is often cited as an example of a sustainable system (De Datta,1981; FAO, 1994; Greenland, 1997). Growing of rice in submerged soilsis an integral component of traditional, age-old technology in monsoonAsia (Kyuma, 2004). This method of rice cultivation involves land prep-aration by cultivating the land in flooded or saturated state (termed pud-dling), followed by transplanting rice seedlings into the puddled paddies,and growing of rice in submerged soils until two to three weeks prior toharvest of rice crop.</p><p>However, water shortage experienced in some regions of Asia isthreatening the traditional system of lowland rice cultivation. Hence,there is a need for exploring alternate water management practices thatsave water and at the same time, increase water productivity. Water pro-ductivity is generally defined as the weight of economic yield or grains</p><p>6 JOURNAL OF SUSTAINABLE AGRICULTURE</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Geo</p><p>rge </p><p>Mas</p><p>on U</p><p>nive</p><p>rsity</p><p>] at</p><p> 02:</p><p>36 1</p><p>0 Ju</p><p>ly 2</p><p>014 </p><p></p></li><li><p>produced per unit of water input (rainfall plus irrigation) (Bouman et al.,2005).</p><p>The present water shortage situation for growing rice indeed presentsan opportunity to critically analyze the advantages of submerged ricesystems in maintaining soil fertility for a sustainable rice production.Therefore, the objective of this paper is to highlight the underlying prin-ciples that govern fertility advantages in submerged rice systems. Addi-tionally, recent research developments on comparative evaluation ofrice production under submerged and alternate submerged and non-sub-merged water regimes are reviewed.</p><p>RICE PRODUCTION UNDER FLOODEDVERSUS NON-FLOODED WATER REGIMES</p><p>Before discussing the soil fertility of submerged rice cropping sys-tems, it is important to assess recent research development on compar-ative evaluation of rice production under submerged and alternate watermanagement practices (drained or alternate submerged and non-sub-merged) that have the potential to save water. This discussion attemptsto put into perspective the role of soil submergence on rice productivity,which is based on sustainable fertility maintenance.</p><p>In some regions of Asia, lowland irrigated rice cultivation is increas-ingly threatened by freshwater scarcity and as a result, alternate watermanagement practices are being proposed, considered and evaluated forrice culture. The various water-saving practices proposed and evaluatedinclude: growing of rice under water-saturated soil condition (no freewater on the surface) or under alternate submerged (flooding) and non-submerged water regimes (Tabbal et al., 2002; Belder et al., 2004). Re-cently, a new radical approach proposed, to reduce water inputs in rice,was to grow rice under aerobic soil conditions (aerobic rice) like an irri-gated upland crop, for example, maize or wheat crop. The aerobic ricecrop was grown in unpuddled, unsaturated soil without ponded water(Yang et al., 2005; Bouman et al., 2005). The rice crop was irrigatedto keep the soil water content in the root zone up to the field capacity.More detailed descriptions of water management practice for aerobicrice cultivation are available in papers by Yang et al. (2005) andBouman et al. (2005).</p><p>This section discusses the results of recent research on the evaluationof effects of various alternate non-submerged water regimes compared</p><p>Research, Reviews, Practices, Policy and Technology 7</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Geo</p><p>rge </p><p>Mas</p><p>on U</p><p>nive</p><p>rsity</p><p>] at</p><p> 02:</p><p>36 1</p><p>0 Ju</p><p>ly 2</p><p>014 </p></li><li><p>to submerged water regime on the performance of wetland rice in thefield, as judged by yield, water-use efficiency and water productivity.</p><p>An earlier study found that when lowland rice variety (IR 20) wasgrown in aerobic soil under furrow irrigation at the International Rice Re-search Institute (IRRI) farm in the Philippines, water savings were 55%compared with flooded conditions, but the rice yield drastically de-creased from about 8 t ha1 under submerged water regime to 3.4 t ha1under aerobic condition (De Datta et al., 1973).</p><p>Several subsequent studies from Asia and elsewhere, also report-ed a range in the reduction of rice yields when lowland rice varietieswere grown in aerobic soils compared to under flooded soil conditions(Blackwell et al., 1985; McCauley, 1990; Bouman and Tuong, 2001;Yang et al., 2005). The decrease in rice yields varied depending on theadaptability of the rice varieties to aerobic soils, management of macroand micro nutrients, management of weeds and diseases, such as nema-todes in aerobic soil conditions (George et al., 2002; Coyne et al., 2004;Yang et al., 2005).</p><p>In general, it has been observed that alternate water managementpractices such as alternate submerged and non-submerged water re-gimes save water but reduce rice yields, especially on soils that arefreely drained. However, the performance of rice crops on lowland sitesthat are poorly drained vary from those on freely drained upland sites.For example, in field studies, Diatta and Sahrawat (1997) showed thatthe performance of four rice varieties, along a toposequence in WestAfrica, was influenced by the presence or absence of a perched watertable (within 30 cm of the soil surface). The presence of perched shal-low water table in the growing season increased rice yields and biomassof upland and lowland rice varieties; the lowland rice cultivars out-yielded the upland rice cultivars (Diatta and Sahrawat, 1997).</p><p>Belder et al. (2004) conducted field experiments under irrigatedconditions at two sites, one each in China and the Philippines, to studythe comparative effects of continuous submergence and alternate sub-merged and non-submerged water regimes at two rates of fertilizerN (with no applied N and 180 kg N ha1) on the performance of low-landrice cultivars. The experimental sites had silty clay loam soils, shal-low groundwater tables and low percolation rates. Grain yields of thehybrid and inbred rice varieties ranged from 4.1 to 5.0 t ha1 with noapplied N, and from 6.8 to 9.2 t ha1 with 180 kg N ha1. Biomassand grain yields did not significantly differ between the two waterregimes (continuous submergence and alternate submerged and non-submerged). The amount of water saved with alternate submerged and</p><p>8 JOURNAL OF SUSTAINABLE AGRICULTURE</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Geo</p><p>rge </p><p>Mas</p><p>on U</p><p>nive</p><p>rsity</p><p>] at</p><p> 02:</p><p>36 1</p><p>0 Ju</p><p>ly 2</p><p>014 </p></li><li><p>non-submerged water regime was small (6-14% of total water input and15-18% of irrigation water input). Water productivity ranged from 0.5to 1.48 kg m3 of water input at the two sites. The relatively high valuesof water productivity even at low rice yields (compared with thosereported by Bouman et al., 2005) were likely caused by a larger pro-portion of water being taken up from the shallow groundwater (Belderet al., 2004). There was no significant N by water interaction in theexperiments; this was attributed to the particular hydrological condi-tions at the sites of field experiments. During the periods of non-sub-mergence water regime, the soil remained close to saturation.</p><p>Belder et al. (2004) concluded that hydrological characterization andmapping of Asias lowland rice areas was needed to determine the ex-tent and magnitude of potential water savings that could be made with-out compromising on rice yield.</p><p>More research on improved rice cultivars adapted to aerobic growingconditions is needed. Crop and water management practices need to bedeveloped for the growing of aerobic rice; and there is need to study thesustainability of aerobic rice under continuous cropping (George et al.,2002; Coyne et al., 2004; Bouman et al., 2005).</p><p>The results, from studies thus far, indicate that the yields of rice underaerobic soil conditions, with few exceptions on sites with shallow watertable (Belder et al., 2004), are lower than those in flooded soils. The re-search issues relating to the potential of aerobic rice and its sustainabilityin Asia however, can only be judged by long-term studies in the future,although research in this important area by scientists at the IRRI (Inter-national Rice Research Institute) and their collaborators has begun inearnest (Bouman et al., 2005; Yang et al., 2005). The findings of the on-going and future research should help formulate appropriate water man-agement practices for growing rice with improved water-use efficiencyand water productivity.</p><p>THE STABILIZATIONOF pH IN THE NEUTRAL RANGE AND ITS IMPLICATIONS</p><p>FOR NUTRIENT AVAILABILITY</p><p>Following submergence, the pH of acidic soils increase, while thoseof alkaline soils decrease (Ponnamperuma, 1972; Narteh and Sahrawat,1999). The pH of acidic soils increases following submergence because</p><p>Research, Reviews, Practices, Policy and Technology 9</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Geo</p><p>rge </p><p>Mas</p><p>on U</p><p>nive</p><p>rsity</p><p>] at</p><p> 02:</p><p>36 1</p><p>0 Ju</p><p>ly 2</p><p>014 </p></li><li><p>under anaerobic conditions ferric iron is used as an electron acceptor foroxidizing organic matter and during this process acidity is consumed:</p><p>Fe2O3 CH2O 4 H = 2 Fe2 5/2 H2O CO2 (1)</p><p>In these redox reactions, ferric iron (from amorphous ferric hydroxides)serves as an electron acceptor and the organic matter (CH2O) as theelectron donor. This reaction results in the consumption of acidity andthereby raising the pH.</p><p>A decrease in the pH of alkali or calcareous soils is the result of accu-mulation of carbon dioxide in flooded soil, which neutralizes alkalinity.Moreover the carbon dioxide produced is retained in the flooded soildue to restricted diffu...</p></li></ul>


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