-The objective of this study was to assess the development response of cultivated rice and red rice to different increases in minimum and maximum daily air temperatures, in Santa Maria, Rio Grande do Sul State, Brazil. One hundred years climate scenarios of temperatures 0, +1, +2, +3, +4, and +5 o C, with symmetric and asymmetric increases in minimum and maximum daily air temperatures were created, using the LARS-WG Weather Generator, and a 1969-2003 database. Nine cultivated rice genotypes (IRGA 421, IRGA 416, IRGA 417, IRGA 420, BRS 7 TAIM, BR-IRGA 409, EPAGRI 109, EEA 406 and a hybrid), and two red rice biotypes (awned black hull-ABHRR, and awned yellow hull-AYHRR) were used. The dates of panicle differentiation (R1), anthesis (R4), and all grains with brown hulls (R9) were estimated with a nonlinear simulation model. Overall, the duration of the emergence-R1 phase decreased, whereas the duration of the R1-R4 and R4-R9 phases most often increased, as temperature increased in the climate change scenarios. The simulated rice development response to elevated temperature was not the same, when the increase in minimum and maximum temperature was symmetric or asymmetric.Index terms: Oryza sativa, global warming, phenology, simulation, weeds. Impacto do aumento na temperatura média do ar sobre o desenvolvimento do arroz e do arroz-vermelhoResumo -O objetivo deste trabalho foi avaliar a resposta do desenvolvimento do arroz cultivado e do arroz vermelho a diferentes aumentos nas temperaturas mínima e máxima diárias do ar, em Santa Maria, RS, Brasil. Foram criados cenários climáticos de cem anos de 0, +1, +2, +3, +4 e +5 o C, com aumentos simétricos e assimétricos nas temperaturas mínima e máxima diária do ar, usando o Weather Generator LARS-WG e uma base de dados de 1969-2003. Foram usados nove genótipos de arroz cultivado (IRGA 421, IRGA 416, IRGA 417, IRGA 420, BRS 7 TAIM, BR-IRGA 409, EPAGRI 109, um híbrido e EEA 406) e dois biótipos de arroz-vermelho (casca preta aristado e casca amarela aristado). A data da diferenciação da panícula (R1), a antese (R4) e todos os grãos com casca marrom (R9) foram estimados com um modelo não linear. Em geral, a duração da fase emergência-R1 diminuiu, enquanto a duração das fases R1-R4 e R4-R9 aumentaram, com o aumento da temperatura nos cenários de mudança climática. A resposta simulada do desenvolvimento do arroz à elevação da temperatura não foi a mesma, quando o aumento na temperatura mínima e máxima foi simétrico ou assimétrico.Termos para indexação: Oryza sativa, aquecimento global, fenologia, simulação, planta daninha.
Desenvolvimento vegetativo e reprodutivo de cultivares de trigo e sua associação com a emissão de folhas
RESUMOVernalização é o processo pelo qual as plantas são induzidas a florescer através da exposição a temperaturas baixas não congelantes. Funções de resposta à vernalização foram ajustadas para caracterizar trigos de inverno, mas ainda não as foram para trigos brasileiros. Os objetivos deste trabalho foram determinar a sensibilidade à vernalização de algumas cultivares de trigo do sul do Brasil e ajustar uma função não linear de reposta à vernalização para estas cultivares. Foram aplicados oito tratamentos de vernalização (0, 7, 14, 21, 28, 35, 42 e 49 dias de vernalização) em seis cultivares de trigo (BRS Louro, BRS 177, BRS Tarumã, CEP 51, CEP 52 e Nova Era). A cultivar BRS Louro não foi responsiva aos tratamentos de vernalização, na cultivar BRS Tarumã ocorreu forte sensibilidade à vernalização, similar a trigos de inverno, e nas cultivares BRS 177, CEP 51, CEP 52 e Nova Era a resposta à vernalização foi intermediária. Para as cultivares responsivas à vernalização foram ajustadas funções não lineares que podem ser usadas em modelos de simulação do desenvolvimento de cultivares sul brasileiras de trigo com distintos requerimentos em vernalização.Palavras-chave: Triticum aestivum L., modelagem, temperatura, soma térmica, emissão de folhas. ABSTRACT VERNALIZATION RESPONSE OF BRAZILIAN WHEAT CULTIVARSVernalization is a process by which plants are inducted to enter the reproductive phase through an exposure to low nonfreezing temperatures. Vernalization response functions have been proposed for winter wheats, but no indication of vernalization response functions for Brazilian wheats were found in the literature. The objectives of this study were to evaluate vernalization response of some Brazilian wheat cultivars and to fit a vernalization response function for these cultivars. Eight vernalization treatments (0, 7, 14, 21, 28, 35, 42 and 49 vernalization days) and six wheat cultivars (BRS Louro, BRS 177, BRS Tarumã, CEP 51, CEP 52 e Nova Era) were used. The cultivar BRS Louro showed no response to vernalization, BRS Tarumã was strongly sensitive to vernalization, similar to winter wheat, and cultivars BRS 177, CEP 51, CEP 52, and Nova Era presented intermediate vernalization response. For the cultivars that presented some response to vernalization, response functions are presented, which can be used in models for simulating the development of Brazilian wheat cultivars with distinct vernalization requirements.Key words: Triticum aestivum L., modelling, temperature, thermal sum, leaf emergence.
-The objective of this study was to improve the simulation of node number in soybean cultivars with determinate stem habits. A nonlinear model considering two approaches to input daily air temperature data (daily mean temperature and daily minimum/maximum air temperatures) was used. The node number on the main stem data of ten soybean cultivars was collected in a three-year field experiment (from 2004/2005 to 2006/2007) at Santa Maria, RS, Brazil. Node number was simulated using the Soydev model, which has a nonlinear temperature response function [f(T)]. The f(T) was calculated using two methods: using daily mean air temperature calculated as the arithmetic average among daily minimum and maximum air temperatures (Soydev tmean ); and calculating an f(T) using minimum air temperature and other using maximum air temperature and then averaging the two f(T)s (Soydev tmm ). Root mean square error (RMSE) and deviations (simulated minus observed) were used as statistics to evaluate the performance of the two versions of Soydev. Simulations of node number in soybean were better with the Soydev tmm version, with a 0.5 to 1.4 node RMSE. Node number can be simulated for several soybean cultivars using only one set of model coefficients, with a 0.8 to 2.4 node RMSE.Index terms: Glycine max, node appearance rate, vegetative development, V-stages. Melhoria na simulação do número de nós em sojaResumo -O objetivo deste trabalho foi melhorar a simulação do número de nós em cultivares de soja de hábito de crescimento determinado. Foi utilizado um modelo não linear que considera duas abordagens para entrada dos dados de temperatura diária do ar (temperatura média diária e temperaturas mínima/máxima diárias). Foram usados dados de número de nós na haste principal de dez cultivares de soja coletados em um experimento de campo durante três anos (de 2004/2005 a 2006/2007) em Santa Maria, RS. O número de nós foi simulado com o modelo Soydev, que tem uma função não linear de resposta à temperatura [f(T)]. A f(T) foi calculada por dois métodos: pela temperatura média diária do ar, determinada pela média aritmética entre as temperaturas mínima e máxima diárias (Soydev tmédia ), e pela média entre os valores das f(T)s da temperatura mínima do ar e da temperatura máxima do ar (Soydev tmm ). A raiz do quadrado médio do erro (RQME) e os desvios (simulado menos observado) foram as estatísticas usadas para avaliar o desempenho das duas versões do Soydev. A simulação do número de nós em soja foi melhor com a versão Soydev tmm , com um RQME de 0,5 a 1,4 nós. O número de nós pode ser simulado em várias cultivares de soja usando-se apenas um conjunto de coeficientes, com uma RQME entre 0,8 e 2,4 nós.Termos para indexação: Glycine max, taxa de aparecimento de nós, desenvolvimento vegetativo, estádios-V.
Panicle differentiation (DP) is a key developmental stage in rice (Oryza sativa L.) because at this stage plant switches from vegetative to reproductive development and source-sink relation changes to allocate part of the photoassimilates for growing spikelets and kernels. The objective of this study was to determine the main stem Haun Stage (HS) and the number of leaves that still have to emerge until flag leaf at PD in several cultivated rice genotypes and red rice biotypes in different sowing dates. A two-year field experiment was conducted in Santa Maria, Rio Grande do Sul State, Brazil, during the 2005-2006 and 2006-2007 growing seasons, and three sowing dates each year. Nine cultivated rice genotypes and two red rice biotypes were used. PD was identified as the R1 stage of the COUNCE scale, by sampling four plants from each genotype on a daily basis. When 50% of the sampled plants were at R1, the main stem HS was measured in 20 plants per genotype. The main stem final leaf number (FLN) was measured in these 20 plants when the collar of the flag leaf was visible. HS at PD is related to FLN in many cultivated rice genotypes and red rice biotypes, and that at PD, the number of leaves still to emerge until flag leaf is not constant for all the rice genotypes. These findings are not in agreement with reports in the literature.
Polymer coated urea (PCU) have the potential to increase nitrogen (N) use efficiency (NUE) by the release of N following crop demand while reducing losses by volatilization, leaching and denitrification. However, the NUE of PCU is still unclear especially in systems of corn-palisadegrass intercropping. Broadcast application of urea result in ammonia volatilization losses, new technologies must be adopted in order to allow broadcast application of urea. The aim of this research was to evaluate NUE from PCU in the corn-palisadegrass intercropping system and the viability of the broadcast application using PCU. Two field trials were carried out in a 4 × 2 factorial design including fertilization treatments and application forms. Fertilization treatments were: Conventional Urea topdressing (CUT); Conventional Urea at corn planting (CUP); PCU applied at planting to release in 30 days (PCU30); PCU mixture applied at planting to release in 30 and 60 days (PCU30+60); and application forms: broadcast placement and in furrow. 15N-urea was used for the determination of NUE. The corn yield and palisadegrass above-ground biomass were not affected by the fertilization treatments or application forms. PCU did not increase N uptake and the NUE by corn or palisadegrass in relation to urea. The N uptake from fertilizer by palisadegrass intercropped with corn is less than 1% of all N uptake on the intercropping system and at most 2% of the N fertilizer applied. The slow release urea does not enable the broadcast application and its efficiency depended upon the same climatic conditions as those of the conventional urea.
Yield and nutrition of greenhouse-grown strawberries (Fragaria AbstractIn strawberry, potassium fertilization has been little studied, which difficult management strategies for an increasing yield and understanding the use of this nutrient in strawberry crop. The aim of this study was to evaluate the influence of sources and rates of potassium (K) fertilizers on yield, K level and agronomic traits of strawberry cv. Camarosa fruit, carried out under greenhouse conditions. A randomized in a completely block design with four replicates in a factorial arranged 6x3 (six rates of potassium x three sources of potassium fertilizers), was performed. Fertilizers sources used were as follows: potassium sulphate, potassium nitrate and potassium chloride in 0, 60, 120, 180, 240 and 300 kg ha -1 K 2 O doses. An increasing potassium rates have allowed a higher potassium content in leaves and fruits. A higher potassium content in leaves was obtained by KNO 3 (11.70 g kg -1 ). Yield, fruit number per plant and potassium extraction per plant, increased linearly with the evaluated doses and fruit average weight at a dose of 183 kg ha -1 . There was no significant difference among potassium content in leaves. Strawberry production is maximized through potassium fertilization, independent of the source origin.
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