Grain yield reduction in transplanted rice was generally lower than in direct-seeded rice.
Ampong-Nyarko and De Datta (1991) explained that transplanted rice has low potential to yield loss due to its head start over the weeds. Meanwhile, direct- seeded rice has high potential to yield losses because its germinating seeds grow together with weeds (Casimero, 2004). The absence of early flooding to suppress weeds during the initial growth phase, absence of seedling size to compete with weeds, and the uneven stand that provides space weeds to grow further aggravate the vulnerability of direct-seeded rice to weed competition and yield losses (Kumar et al., 2017; Chauhan, 2012).
Correlation and Regression
Density and shoot dry weight of C. diffusa were strongly, negatively correlated to grain yields of TPR (r = -0.990, -0.987) and DSR (r = -0.987, -0.965).
Simple linear regression analysis also indicated that 98.02 and 97.49% grain yield of TPR and 97.41 and 99.64% grain yield of DSR were influenced by the density and shoot dry weight of C. diffusa (Figure 1).
Further analysis showed that the density and shoot dry weight of C. diffusa were significant predictors and contributors to the grain yield of rice at 5% level of significance (density: p = .0012 TPR, p = .0018 DSR) (shoot dry weight: p = .0017 TPR, p = .0078 DSR). The final predictive models for TPR were GY
= -0.8769 (C. diffusa density pot-1) + 27.866 and GY
= -0.0381 (C. diffusa shoot dry weight in g plant-1) + 28.394. For the direct-seeded, GY = -1.2985 (C.
diffusa density pot-1) + 27.248 and GY = -0.0573 (C.
diffusa shoot dry weight in g plant-1) + 28.1.
Knowledge on the weed’s competitive ability helps decide whether control has to be implemented to suppress its growth. In this study, C. diffusa significantly reduced the growth and grain yield of rice under saturated condition implying that control
must be implemented whenever it grows with rice at minimum of 5 densities. In controlling C. diffusa and other perennial weeds of rainfed rice, practicing field sanitation, thorough land preparation, handweeding, and chemical control were regarded as best options by Donayre et al. (2018) and PhilRice (2001, 2007).
They emphasized that practicing field sanitation such as keeping the seedling nurseries, irrigation canals, and field bunds clean and weed-free help prevent entries of volunteer weed seeds and asexual propagules. Furthermore, thorough land preparation and practicing stale-seedbed technique bury weeds under the soil, separate shoots from roots, encourage germination of dormant seeds, desiccate shoots, and exhaust carbohydrate reserves of perennial weeds. In addition, manual weeding and herbicide application are very effective and efficient in removing and eradicating weeds that grow within rows and hills of rice.
Literature Cited
Adalla CB, Magsino EA (2006) Understanding the golden apple snail (Pomacea canaliculata): Biology and early initiative to control the pest in the Philippines. RC Joshi, LS Sebastian (Eds.). In Global Advances in Ecology and Management of Golden Apple Snail. Philippine Rice Research Institute, Los Baños, Laguna, Philippines, pp 199-213
Ampong-Nyarko K, De Datta SK (1991) A Handbook for Weed Control in Rice. IRRI, Los Baños, Laguna, Philippines Baltazar AM, Martin EC, Casimero MC, Bariuan FV, Obien
SR, De Datta SK (1999) Major weeds and dominance patterns in rainfed rice-onion cropping system. Philippine Agricultural Scientist 82(2): 166-177
Beltran JC, Bordey FH, Launio CC, Litonjua AC, Manalili RG, Mataia AB, Relado RZ, Moya PF (2016) Pesticide use and practices. In Bordey FH, PF Moya, JC Beltran, DC Dawe (Eds.). Competitiveness of Philippine Rice in Asia.
Philippine Rice Research Institute, Maligaya, Science City of Muñoz, Nueva Ecija, Philippines, pp 75-86
Casimero MC (2004) Managing weeds in rice. In Redoña ED, Castro AP, Llanto GP (Eds). Rice Integrated Crop Management:
Towards a Rice Check System in the Philippines. Philippine Rice Research Institute, Maligaya, Science City of Muñoz, Nueva Ecija, Philippines, pp 107-119
Caton BP, Mortimer M, Hill JE, Johnson DE (2010) A Practical Guide to Weeds of Rice in Asia (2nd Ed). International Rice Research Institute, Los Baños, Laguna, Philippines Chauhan BS (2012) Weed Management in Direct-Seeded Rice
Systems. International Rice Research Institute, Los Baños, Laguna, Philippines. http://books.irri.org/9789712202940_
content.pdf (accessed July 5, 2013)
Chauhan BS (2013) Effect of weedy rice variants and weedy rice density on the growth and yield of two rice cultivars in the Philippines. Canadian Journal of Plant Protection 1(1):
28-34. http://goo.gl/svRf6O (accessed April 27, 2014) Donayre DKM, Endino-Tayson CA (2015) Competitive ability,
critical period of competition, and density level of Hydrolea zeylanica (L.) Vahl against transplanted-irrigated lowland rice. IAMURE International Journal of Ecology and Conservation 14: 191-214
Donayre DKM, Endino CA, Seville CU, Ciocon IMG (2014) Major weeds and farmers’ weed management practices in rainfed ricefields of Negros, Philippines. Asia Life Sciences 23(1): 137-148
Donayre DKM, Martin EC, Santiago SE, Lee JT (2018) Weeds in Irrigated and Rainfed Lowland Ricefields in the Philippines (2nd Ed). Philippine Rice Research Institute, Maligaya, Science City of Muñoz, Nueva Ecija, Philippines
Donayre DKM, Santiago SE, Martin EC, Lee JT, Corales RG, Kumar V, Janiya J (2019) Weeds of Vegetables and Other Cash Crops in the Philippines. Philippine Rice Research Institute, Maligaya, Science City of Muñoz, Nueva Ecija [EPPO] European Plant Protection Organization (2019) EPPO
Global Database. https://gd.eppo.int
Fabro LE, Barcial PM (2015) Weeds of vegetables. In Dela Cueva FM, Pascual CB, Bajet CM, Dalisay TU (Eds.).
Pests and Diseases of Economically Important Crops in the Philippines. Pest Management Council of the Philippines, Inc. c/o Crop Protection Cluster, University of the Philippines Los Banos, College, Laguna, Philippines, pp 554-580
Fried O, Kuhn I, Schrader I, Sihn NV, Bermeier E (2017) Plant diversity and community composition of rice agroecosystems in Vietnam and the Philippines.
Phytocoenologia 47 (1): 49 – 66. https://www.schweizerbart.
de/papers/phyto/detail/47/87476/Plant_diversity_and_
community_composition_of_rice_agroecosystems_in_
Vietnam_and_the_Philippines (accessed March 16, 2018) Galinato MI, Moody K, Piggin CM (1999) Upland Rice Weeds
of South and Southeast Asia. International Rice Research Institute, College, Laguna, Philippines
Gomez KA, Gomez AA (1984) Statistical Procedures for Agricultural Research (2nd Ed). John Wiley and Sons, USA Heong KL, Escalada MM (1997) A comparative analysis of
pest management practices of rice farmers in Asia. In Heong KL, Escalada MM (Eds) Pest Management of Rice Farmers in Asia. International Rice Research Institute, College, Laguna, Philippines
Kumar V, Opeña J, Valencia K, Thi HL, Son NH, Donayre DKM, Janiya J, Johnson DE (2017) Rice weed management in Southeast Asia. In Rao AN and H Matsumoto (Eds.) Weed Management in Rice in the Asian-Pacific Region. Asian Pacific Weed Science Society; The Weed Science Society of Japan; and Indian Society of Weed Science, India, pp 282-307
Lubigan RT, Moody K (1990) Competition between transplanted rice and Ischaemum rugosum. Journal of Plant Protection in the Tropics 7(3): 147-153. http://goo.gl/U2ZGtP (accessed June 21, 2014).
Magsino G (2015) Weeds of banana and corn. In Dela Cueva FM, Pascual CB, Bajet CM, Dalisay TU (Eds). Pests and Diseases of Economically Important Crops in the Philippines. Pest Management Council of the Philippines, Inc. Crop Protection Cluster, University of the Philippines Los Banos, College, Laguna, Philippines pp 519-553 Mataia AB, Francisco SR (2008) Crop loss assessment and
economic impact of tungro disease in the Philippines. In Tiongco ER, Angeles ER, Sebastian LS. The Rice Tungro Virus Disease: A Paradigm in Disease Management.
Philippine Rice Research Institute, Maligaya, Science City of Muñoz, Nueva Ecija, pp 15-29
Moody K, Escalada MM, Heong KL (1997) Weed management practices of rice farmers in Iloilo, Philippines. In Heong KL, Escalada MM (Eds.). Pest Management of Rice Farmers in Asia. International Rice Research Institute, College, Laguna, Philippines, pp 143-160
Moody K, Munroe CE, Lubigan RT, Paller Jr EC, Barcial PM, Fabro LE, Janiya JD, Magsino GL (2014) Major Weeds of the Philippines (2nd Ed). University of the Philippines Los Baños, Philippines
Oliveira LSG, Dalvi LP, Altoé SC, Rocha LJFN, Oliveira FL (2017). Competition with spreading dayflower (Commelina diffusa L.) can affect the agronomic characteristics and mineral content of common bean grains. Cien. Inv. Agr. 44(2): 121-126 https://scielo.conicyt.
cl/pdf/ciagr/v44n2/0304-5609-ciagr-44-02-0121.pdf (accessed November 13, 2017)
Pablico PP, Moody K (1987) A survey of weeds inn transplanted and wet-seeded rice under rainfed and irrigated conditions.
International Rice Research Newsletter 12(1): 23 Pancho JV, Obien SR (1995) Manual of Ricefield Weeds in the
Philippines. Philippine Rice Research Institute, Maligaya, Science City of Muñoz, Nueva Ecija, Philippines [PhilRice] Philippine Rice Research Institute (2007) Integrated
Pest Management in Rice-Vegetable Cropping Systems.
Philippine Rice Research Institute, Science City of Muñoz, Nueva Ecija
[PhilRice] Philippine Rice Research Institute (2001) Management Options for Ricefield Weeds. Philippine Rice Research Institute, Science City of Muñoz, Nueva Ecija
[PhilRice] Philippine Rice Research Institute (2007) Philippine Rice Production Training Manual. Philippine Rice Research Institute, Science City of Muñoz, Nueva Ecija Rao AN, Chandrasena N, Matsumoto H (2017) Rice weed
management in Asian-Pacific Region: An overview. In Rao AN, Matsumoto H (Eds.). Weed Management in Rice in the Asian-Pacific Region. Asian Pacific Weed Science Society;
The Weed Science Society of Japan; and Indian Society of Weed Science, India, pp 1-41
Rao AN, Moody K (1992) Competition between Echinochloa glabrescens and rice (Oryza sativa). Tropical Pest Management 38(1): 25-29. http://goo.gl/0CHq1C (accessed January 5, 2014)
Raymundo AD (2006) Lost Harvest: Quantifying the Effect of Plant Diseases on Major Crops in the Philippines. University of the Philippines Los Banos, College, Laguna
Savary S, Willocquet L, Elazegui FA, Castilla NP, Teng PS (2000) Rice pest constraints in tropical Asia: Quantification of yield losses due to rice pests in a range of production situations. Plant Disease 84: 357-369
Smith R (1984) Competition of spreading dayflower (Commelina diffusa) with rice (Oryza sativa). Weed Science 32(1):
116-119. https://www.cambridge.org/core/journals/weed- science/article/competition-of-spreading-dayflower- commelina-diffusa-with-rice-oryza-sativa/66787DAF0C4 22AA3D8DD08AE0558C1E6 (accessed March 03, 2017) Steinberg WJ (2008) Statistics Alive. SAGE Publications, Los
Angeles, USA
Swanton CJ, Nkoa R, Blackshaw RE (2015) Experimental methods for crop–weed competition studies. Weed Science Special Issue: 2-11
Yoshida S (1981) Fundamentals of Rice Crop Science. International Rice Research Institute, College, Laguna, Philippines. http://
books.irri.org/9711040522_content.pdf (accessed July 4, 2013)
Quality and Acceptability of Rice: Adlai Blend