Influence of Blast on the Nutrition and Yield of Irrigated Rice in Southern Brazil
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ORIGINAL PAPER
Influence of Blast on the Nutrition and Yield of Irrigated Rice in Southern Brazil Claudio Ogoshi 1 & Filipe Selau Carlos 2 & Daniel Waldow 3 & Fernando Fumagali Miranda 3 & Júlia Lima Reginato 2 & André Ulguim 4 Received: 9 October 2019 / Accepted: 2 March 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract In recent decades, nitrogen fertilization rates have increased significantly in irrigated rice fields in southern Brazil. However, there is a gap in knowledge concerning the use of these high rates of nitrogen fertilization in cultivars with a high yield potential, and susceptible to rice blast. We therefore conducted a field experiment in the 2014/2015 and 2015/2016 crop year to evaluate blast severity, plant tissue nutrition, and yield and grain quality with increasing nitrogen fertilization levels in a rice blast-susceptible cultivar (Guri Inta CL). The experiment had three factors, with factor 1: N doses (0, 60, 120, and 180 kg ha−1), factor 2: sowing dates (early and late), and factor 3: with and without fungicide application. The experimental design was randomized blocks with four replications. The area under the disease progress curve was positively influenced by the increase of N rates in the two crops years. Grain yield had a negative quadratic effect as a function of N rates. Increased N levels reduced the thousand grains weight. Late sowing and non-application of fungicide increased disease severity; there was reduced yield, grain quality, and N use efficiency. It is concluded that the use of N levels greater than 60 kg ha−1 in rice blast-susceptible cultivars in southern Brazil increases disease severity with lower N use, reduces grain yield and grain quality. Keywords Irrigated rice . Plant nutrition . Magnaporthe oryzae
1 Introduction Brazil is the main rice producer outside the Asian continent, and about 75% of total rice production comes from the south of the country in flood irrigation areas (SOSBAI 2018). Rice cultivation in this region presents major challenges (Siddique et al. 2019), especially the occurrence of diseases, which is a limiting factor for the cultivars to attain their productive potential. Since, the earliest reports of rice-related disease damage in southern Brazil, the most widespread concern among growers
* Filipe Selau Carlos [email protected] 1
EPAGRI – Agricultural Research and Rural Extension Enterprise of Santa Catarina, Abílio Franco, 1500, Bom Sucesso, 591, Caçador, Santa Catarina 89501-032, Brazil
2
UFPEL – Federal University of Pelotas, Pelotas, Brazil
3
IRGA – Rio Grande do Sul Rice Institute, Cachoeirinha, Brazil
4
UFSM – Federal University of Santa Maria, Santa Maria, Brazil
and researchers has been rice blast (Ogoshi et al. 2018). This major disease is caused by the fungus Magnaporthe oryzae, formerly known as Magnaporthe grisea (Barr) [anamorph Pyricularia oryzae (formerly called P. grisea (Cooke) Sacc)] (Couch and Kohn 2002), and it can cause disease throughout the rice plant, from the early development stages t
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