ABSTRACT The aim of this research was to evaluate the physiological and productive aspects of irrigated cassava crop. The statistical design used was randomised blocks, with six treatments and four replications. The used treatments were irrigation levels, based on the crop evapotranspiration – ETC – (L0 = 0% [rainfed], L1 = 40%, L2 = 80%, L3 = 120%, L4 = 160% and L5 = 200% of the ETC) and the analysed physiological variables were: gas exchange, the quantum efficiency of photosystem II (PSII) and the soil plant analysis development (SPAD) index. The growth and crop productivity were also evaluated through of the leaf area index (LAI), the number and productivity of commercial roots and total biomass. In this research, the total irrigation depth was defined as the irrigation depth plus the effective rainfall. The estimated ETC was 1,030 mm over the 12-month production cycle and the greatest value for LAI and SPAD were 7.6 and 57.4, respectively, obtained in irrigated areas with the level of 80% of the ETC. While, in the areas irrigated with 120% of the ETC, were obtained the highest values of root productivity (93 Mg·ha–1), total biomass yield (149 Mg·ha–1) and photosynthetic rate (22.4 μmol CO2·m–2·s–1). On the other hand, with irrigation equivalent at 200% of the ETC were obtained the greatest values of internal CO2 concentration (245 μmol CO2·m–2·s–1), stomatal conductance (0.35 μmol H2O·m–2·s–1) and effective quantum efficiency (0.68).

RESUMO: A determinação da evapotranspiração real da cultura (ETa) é importante para o manejo da irrigação. Os principais métodos e modelos físicos de estimativa da ETa requerem dados que não são facilmente disponíveis. Neste trabalho, obteve-se o coeficiente da cultura (Kc) da laranja lima na fase inicial de desenvolvimento e avaliou-se o desempenho do modelo semi-empírico de Poulovassilis acoplado a um balanço hídrico simplificado na estimativa da ETa. A ETa (medida) foi obtida a partir da variação temporal do conteúdo de água no solo, obtida através da reflectometria no domínio do tempo (TDR). O modelo de POULOVASSILIS et al. (2001) assume que a redução da evapotranspiração da cultura é expressa por uma função exponencial do armazenamento de água do solo e por um coeficiente de ajuste empírico (ca). O armazenamento de água do solo foi obtido através do balanço hídrico (BH), diário e decendial, contabilizando as entradas e saídas de água do sistema. O parâmetro empírico ca foi obtido por modelagem inversa. O valor ótimo de ca obtido por modelagem inversa 0,05 para o BH diário e 0,03 para o BH decendial. O modelo apresentou melhor desempenho para o BH diário, comparável a outros modelos de estimativa da ETa. O Kc médio para fase inicial da laranja lima foi igual a 0,85.

ABSTRACT: Determining actual crop evapotranspiration (ETa) is paramount for irrigation management. The principal measurement methods and physical models generally require crop and weather data that are not readily available. We determined the crop coefficient (Kc) of sweet oranges during the initial development stage and evaluated the performance of the Poulovassilis semi-empirical model coupled with a simple soil water balance for estimating the ETa. The ETa was inferred from the variation in the soil water content over time, measured by time-domain reflectometry. In the Poulovassilis model, the ETa is obtained by multiplying the crop evapotranspiration (ETc) by an adjustment coefficient (ca), which accounts for a reduction in the evapotranspiration caused by soil water depletion. Soil water storage was obtained using the daily and 10-day soil water balances, computed by considering inputs and outputs of water from the system. The empirical parameter, ca, was determined using inverse modeling. The optimal ca value obtained through inverse modeling was 0.05 and 0.03 for the daily and 10-day soil water balances, respectively. The model performed better for the daily soil water balance than the 10-day balance, with performance comparable with the other ETa models. Average Kc during the sweet orange initial crop stage was 0.85.

ABSTRACT The objective of this study was to verify the influence of spraying nozzles on the selectivity of herbicides in eucalyptus seedlings. XR 110.02 and TTI 110.02 spraying nozzles were used for the application of the herbicides: control treatment; oxyfluorfen (150 g ha–1) and saflufenacil (98 g ha–1). The experimental arrangement was a 2 × 3 factorial one (two spraying nozzles × 3 herbicides), using a randomized complete block design with four replications. The application was performed 15 days after transplanting the seedlings. Plant height (PH), stem diameter (SD), number of leaves (NL), total dry matter (DM), leaf area (LA), visual phytotoxicity (P), quantum efficiency of photosystem II - Fv/Fm, electron transport rate (ETR) and SPAD (S) index were evaluated. The XR 110.02 and TTI 110.02 nozzles did not change the selectivity of oxyfluorfen and saflufenacil.

RESUMO As espécies que apresentam potencial alelopático são promissoras na agricultura, ante a perspectiva da identificação e manipulação dos seus metabólitos secundários, para aplicações práticas e, assim, sua utilização no controle de plantas daninhas. Por esta razão, este trabalho teve por objetivo verificar o efeito alelopático e identificar os metabólitos secundários de Canavalia ensiformis L. Sementes de Lactuca sativa, Digitaria insularis, Emilia coccinea e Portulaca oleracea foram utilizadas como receptoras. Para avaliar o potencial alelopático, foi preparado o extrato etanólico da parte aérea (folhas mais caules) da espécie doadora. Os efeitos potencialmente alelopáticos foram avaliados por meio de testes de germinação e crescimento inicial de plântulas. Foi realizada, também, por meio da técnica da Cromatografia Líquida de Alta Eficiência, a identificação dos metabólitos secundários da parte aérea de C. ensiformis. O extrato etanólico causa inibição da percentagem e do índice de velocidade de germinação de L. sativa. A parte aérea de C. ensiformis contém ácidos fenólicos (ácido clorogênico, ácido ferúlico, ácido cafeico), flavonoides (kaempferol, naringina e rutina) e ácidos carboxílicos (ácido cítrico, ácido malônico e ácido aspártico), podendo ser os responsáveis pela atividade alelopática dessa espécie.

ABSTRACT The species that have allelopathic potential are promising in agriculture, with the perspective of identifying their secondary metabolites and manipulating them, for practical applications and thus be used to control weeds. In this context, this work aimed to verify the allelopathic effect and to identify the secondary metabolites in the Canavalia ensiformis species. The Lactuca sativa, Digitaria insularis, Emilia coccinea and Portulaca oleracea species were used as recipient species. To evaluate the allelopathic potential, the ethanolic extract of the aerial part (leaf + stem) of the donor specie was carried out. Potential allelopathic effects were evaluated by germination tests and initial seedling growth. The identification of the secondary metabolites of the aerial part of C. ensiformis was also performed using the High-Performance Liquid Chromatography technique. The ethanolic extract cause inhibition of germination and germination speed index of L. sativa. The aerial part of C. ensiformis contains the compounds belonging to phenolic acids (chlorogenic acid, ferulic acid, caffeic acid), flavonoids (kaempferol, naringin and rutin) and carboxylic acids (citric acid, malonic acid and aspartic acid) they can be responsible for the allelopathic activity of this species.