I have devoted more than 35 years to aspects of sustainable management of agriculture and natural resources for increasing food security and environmental quality in developing countries. I served at the International Rice Research Institute (IRRI) from 1980 to 2017 (including 10 years from 2004 to 2015 in India) was an adjunct senior scientist at the Columbia University until 2016. Currently, I am an Adjunct Professor in the Dept of Plant Sciences at the University of California-Davis. I provided leadership to the Cereal System Initiative System for South Asia and the Rice-Wheat Consortium Project that aims to sustainably enhance crop productivity. I was a “Frosty” Hill Fellow at Cornell University (July 07–June 08) and an adjunct professor of Soil Science at the University of the Philippines (1990-2004).
My major areas of interest are biological nitrogen fixation, climate-smart nitrogen management, rice production, conservation agriculture.
I am a fellow of the American Association for the Advancement of Science (AAAS), American Society of Agronomy (ASA), the Soil Science Society of America (SSA), the Crop Science Society of America (CSSA), the Indian Academy of Agricultural Sciences (NAAS), and an associate member of the Philippine Council of Agricultural Research (PARC). I am a recipient of several awards and honors notably, the Third World Academy of Sciences Agriculture Prize 2016, the International Crop Science Award 2015, the International Service in Agronomy Award 2011, International Soil Science Award 2010, International Plant Nutrition Institute Science Award 2009. In 2000 and 2004, the CGIAR awarded the Chairman’s Excellence Science Award for Outstanding Scientific Partnership and the prestigious King Baudoin Award for Outstanding Research to the Rice-Wheat Consortium in which I was the key scientist and IRRI’s coordinator.
- N cycling
- Nitrogen fixation
- Sustainable agriculture
- Food security
Current N-related Projects:
- Climate-smart N management practices in cereal-based system
Key publications related to nitrogen. For a full list, please see the following links:
- Ladha JK*, Tirol-Padre A, Reddy CK, Cassman KG, Verma S, Powlson DS, Van Kessel C, Richter DV. 2016. Global nitrogen budget in cereals: A 50-year assessment for maize, rice and wheat. Scientific Reports 6:19355/DOI:1038/screp19355, 1-9.
- Ladha JK*, Rao AN, Raman A, Padre A-Tirol, Dobermann A, Gathala M, Kumar V, Sharawat YS, Sharma S, Piepho HP, Alam MM, Liak R, Rajendran R, Reddy CK, Parsad R, Sharma PC, Singh SS, Saha A, Noor S. 2016. Agronomic improvements can make future cereal systems in South Asia far more productive and result in a lower environmental footprint. Global Change Biology 22, 1054-1074.
- Ladha JK*, Reddy CK, Padre AT, Kessel CV. 2011. Role of Nitrogen Fertilization in Sustaining Organic Matter in Cultivated Soils. Journal of Environmental Quality. 40, 1756-1766.
- Pathak H, Li C, Wassmann R, Ladha JK*. 2006. Simulation of nitrogen balance in the rice-wheat systems of the Indo-Gangetic Plains: Upscaling using the DNDC model. Soil Sci. Soc. Amer. J. 70: 1612-1622.
- Sreevidya VS, Srinivasa Rao C, Sullia SB, Ladha JK, Reddy PM. 2006. Metabolic engineering of rice with soybean isoflavone synthase for promoting nodulation gene expression in rhizobia. J. Exp Botany 57:1957-1969.
- Sreevidya VS, Hernandez-Oane J Rowena, Rollando S Sullia SB, Stacey G, Ladha JK, Reddy PM. 2005. Expression of the legume symbiotic lectin genes psl and gs52 promotes rhizobial colonization of roots in rice. Plant Science 169: 726-736.
- Ladha JK*, Pathak HP, Krupnik TJ, Six J, van Kessel C. 2005. Efficiency of fertilizer nitrogen in cereal production: retrospect and prospect. Advances in Agronomy 87: 85-156.
- Ladha JK*, Reddy PM. 2003. Nitrogen fixation in rice systems: state of knowledge and future prospects. Plant and Soil 252:151-167.
- James EK, Prasad G, Mathan N, Barraquio WL, Reddy PM, Iannetta PPM, Olivares FL, Ladha JK. Infection and colonization of rice seedlings by the plant growth-promoting bacterium Herbaspirillum seropedicae Z67. Molecular Plant-Microbe Interactions 15:894-906.
- Peng S, Biswas JC, Ladha JK, Prasad G, Chen Y. 2002. Influence of rhizobial inoculation on photosynthesis and grain yield and rice. J. 94:925-929.
- Singh Bijay, Singh Yadvinder, Ladha JK, Bronson KF, Balasubramanian V, Singh J, Khind CS. 2002. Chlorophyll meter and leaf color chart-based nitrogen management for rice and wheat in Northwestern India. J. 94:821-829.
- Chalk, PM, Ladha JK*, Padre A. 2002. Efficacy of three 15N labelling techniques for estimating below-ground N in Sesbania rostrata. Fertil. Soils 35:387-389.
- Prasad, G, James EK, Reddy PM, Ladha JK*. 2002. Herbaspirillum colonization increases growth and nitrogen accumulation in aluminum-tolerant rice varieties. New Phytologist 154:131-145.
- Verma SC, Ladha JK, Tripathi AK. 2001. Evaluation of plant growth promoting and colonization ability of endophytic diazotrophs from deep water rice. Biotech. 91:127-141.
- Tan Z, Hurek T, Vinuesa P, Muller P, Ladha JK, Hurek BR. 2001. Specific detection of Bradyrhizobium and Rhizobium strains colonizing rice (Oryza sativa) roots by 16S-23S ribosomal DNA intergenic spacer-targeted PCR. Appl. Environ. Microbiol. 67:3655-3664.
- Singh U, Giller KE, Palm CA, Ladha JK, Breman H. 2001. Synchronizing N release from organic residues: opportunities for integrated management of N. The Scientific World 1: 880-886.
- Tan Z, Hurek T, Prasad G, Ladha JK, Reinhold-Hurek B. 2001. Novel endophytes of rice form a taxonomically distinct subgroup of Serratia marcescens. Appl. Microbiol. 24:245-251.
- Gyaneshwar P, James EK, Natarajan M, Reddy PM, Reinhold-Hurek B, Ladha JK*. Endophytic colonization of rice by a diazotrophic strain of Serratia marcescens. J. Bacteriol. 183:2634-2645.
- Youssef GY, Rizk YR, Abd El-Fattah FK, Squartini A, Corich V, Giacomini A, de Bruijn F, Rademaker J, Maya-Flores J, Ostrom P, Vega-Hernandez M, Hollingsworth RI, Martinez-Molina E, Mateos P, Velazquez E, Wopereis J, Triplett E, Garcia MU, Anarna JA, Rolfe BG, Ladha JK, Hill J, Mujoo R, Ng PK, Dazzo FB. 2001. The Beneficial Plant Growth-Promoting Association of Rhizobium leguminosarum bv. trifolii with Rice Roots. J. Plant Physiol. 28:845-870.
- Ladha JK*, Dawe D, Ventura TS, Singh U, Ventura W, Watanabe I. 2000. Long-term effects of urea and green manure on rice yields and nitrogen balance. Soil Sci. Soc. Am. J. 64:1993-2001.
- Shrestha RK, Ladha JK*. Recycling of residual soil nitrogen in a lowland rice-sweet pepper cropping system. Soil Sci. Soc. Am. J. 64:1689-1698.
- Biswas JC, Ladha JK*, Dazzo FB. 2000. Rhizobial inoculation improves nutrient uptake and growth of lowland rice. Soil Sci. Soc. Am. J. 64:1644-1650.
- Biswas JC, Ladha JK*, Dazzo FB, Yanni YG, Rolfe BG. 2000. Rhizobial inoculation influences seedling vigor and yield of rice. Agron. J. 92:880-886.
- Saxena SS, Ladha JK*, Gyaneshwar P, Reinhold-Hurek B, Hernandez RJ, Biswas JC. 2000. Evaluation of lacZ and gusA markers to study rhizobial colonization in rice roots. Indian J. Microb. 40:15-20.
- Gyaneshwar P, Reddy PM, Ladha JK*. Nutrient amendments influence endophytic colonization of rice by Serratia marcescens IRBG500 and Herbasprillum seropedicae Z67. J. Microbiol. Biotechn. 10:694-699.
- Thönnissen C, Midmore DJ, Ladha JK, Olk DC, Schmidhalter U. 2000. Legume decomposition and nitrogen release when applied as green manures to tropical vegetable production systems. J. 92:253-260.
- Thönnissen C, Midmore DJ, Ladha JK, Holmer RJ, Schmidhalter U. 2000. Tomato crop response to short-duration legume green manures in tropical vegetable systems. J. 92:245-253.
- Bronson KF, Hussain F, Pasuquin E, Ladha JK*. Use of 15N-labeled soil in measuring N fertilizer recovery-efficiency in transplanted rice. Soil Sci. Soc. Am. J. 64:235-239.
- Dey M, Torrizo LB, Chaudhuri RK, Reddy PM, Ladha JK, Datta K, Datta SK. 1999. Transgenic rice harboring legume ENOD40 Rice Genetics Newsletter 16:147-149.
- Dey M, Datta SK, Torrizo LB, Reddy PM, Ladha JK, Day B, Stacey G. 1999. Integration into rice of a soybean apyrase gene proposed to play a central role in nodulation. Rice Genetics Newsletter 16:145-147.
- Chalk PM, Ladha JK*. Estimation of legume symbiotic dependence: an evaluation of techniques based on 15N dilution. Soil Biol. Biochem. 31:1901-1917.
- Reddy PM, Aggarwal RK, Ramos MC, Ladha JK*, Brar DS, Kouchi H. 1999. Widespread occurrence of the homologues of the early nodulin (ENOD) genes in Oryza species and related grasses. Biochem. Biophys. Res. Commun. 258:148-154.
- Kouchi H, Takane K, So RB, Ladha JK*. Reddy PM. 1999. Rice ENOD40: Isolation and expression analysis in rice and transgenic soybean root nodules. Plant J. 18:121-129.
- Praytino J, Stefaniak J, CmcUver J, Weinman J J, Dazzo FB, Ladha JK, Barraquio W, YG, Rolfe BG. 1999. Interactions of rice seedlings with bacteria isolated from rice roots. Aust. J. Plant Physiol. 26:521-535.
- Kundu DK, Ladha JK*. Sustaining productivity of lowland rice soils: issues and options related to N availability. Nutr. Cycl. Agroecosyst. 53:19-33.
- Malarvizhi P, Ladha JK*. Influence of available nitrogen and rice genotype on associative dinitrogen fixation. Soil Sci. Soc. Am. J. 63:93-99.
- Reddy PM, Kouchi H, Ladha JK*. 1998. Isolation, analysis and expression of homologues of the soybean early nodulin gene GmENOD93 (GmN93) from Rice. Biochimica et Biophysica Acta. 1443:386-392.
- Reddy PM, Ladha JK*, Ramos C. Marilou, Mailet F, Hernandez Rowena, Torrizo LB, Oliva NP, Datta SK, Datta K. 1998. Rhizobial lipochitooligosaccharide nodulation factors activate expression of the legume early nodulin gene ENOD12 in rice. The Plant J. 14: 693-702.
- Shrestha RK, Ladha JK*. Nitrate in groundwater and integration of nitrogen-catch crop in rice- sweet pepper cropping system. Soil Sc. Soc. Am. J. 62:1610-1619.
- Singh U, Ladha JK, Castillo EG, Punzalan G, Tirol-Padre A, Duqueza M. 1998. Genotypic variation in nitrogen use efficiency in medium-and long duration rice. Field Crops Res. 58:35-53.
- George T, Buresh RJ, Ladha JK*, Punzalan G. 1998. Recycling in situ legume-fixed and soil N in tropical lowland rice. Agron. J. 90:429-437.
- Clement A, Ladha JK*, Chalifour, FP, 1998. Nitrogen Dynamics of Various Green Manure Species and Relationship to Lowland Rice Production. Agron. J. 90:149-154.
- Ladha JK*, Kirk GJD, Bennett J, Reddy CK, Reddy PM, Singh U. 1998. Opportunities for increased nitrogen use efficiency from improved lowland rice germplasm. Field Crops Res. 56:41-71.
- Cassman K, Peng S, Olk DC, Ladha JK, Reichardt W, Doberman A, Singh U. 1998. Opportunities for increased nitrogen use efficiency from improved resource management in irrigated rice systems. Field Crops Res. 56:7-39.
- Tripathi BP, Ladha JK, Pandey S. 1997. Economic feasibility, production potential and nitrogen behavior in intensively cultivated rice-based cropping systems in Northern Luzon, Philippines. J. Crop Sci. 22:39-48.
- Yanni YG, Rizk RY, Corich V, Squartini A, Ninke K, Hollingsworth, SP, Orgambide G, Bruijn De FJ, Stoltzfus J, Buckley D, Schmidht TM, Mateos PF, Ladha JK, Dazzo FB. 1997. Natural endophytic association between Rhizpbium leguminosarum by trifolii and rice roots and assessment of its potential to promote rice growth. Plant and Soil 194:99-114.
- Reddy PM, Ladha JK*, So R, Hernandez R, Dazzo FB, Angeles OR, Ramos MC, de Bruijn FJ. 1997. Rhizobial communication with rice roots: induction of phenotypic changes, mode of invasion and extent of colonization. Plant and Soil 194:81-98.
- Stoltzfus S, So R, Malarvizhi M, Ladha JK*, de Bruijn FJ. Isolation of endophytic bacteria from rice and assessment of their potential for supplying rice with biologically fixed nitrogen. Plant and Soil 194: 25-36.
- Barraquio WL, Revilla L, Ladha JK*. Isolation of endophytic diazotrophic bacteria from wetland rice. Plant and Soil 194:15-24.
- Ladha JK*, de Bruijn FJ, Malik KA. 1997. Introduction: assessing opportunities for nitrogen fixation in rice – a frontier project. Plant and Soil 194:1-10.
- Ventura W, Ladha JK*. Sesbania phosphorus requirements when used as biofertilizer for long-term rice cultivation. Soil Sci. Soc. Am. J. 61:1240-1244.