ABSTRACT Tahiti lime is a species of great economic importance worldwide. In Brazil, production is concentrated in the states of São Paulo and Pará, where it is usually grafted onto the Rangpur lime. This study aimed to analyze the effects of different irrigation depths on the fruit yield, phenology, and gas exchange of Tahiti lime trees grafted onto Swingle citrumelo. Irrigation was performed during the first year at four different irrigation depths in a random block design with five blocks and four treatments to maintain the soil matric potential in the following ranges: T1: below -50 kPa, T2: from -30 to -50 kPa, T3: from -10 to -30 kPa, and T4: above -10 kPa. The flowering, carbon assimilation rate (A), stomatal conductance (gs), transpiration (E), and fruit yield were measured. Fruits were harvested earlier in the most irrigated treatment, T4, and the yield increased from 2.22 to 6.89 kg per plant from T1 to T4. The average fruit weight escalated from 78.6 to 96.1 g from T1 to T4, and carbon assimilation increased from 6.89 to 9.51 μmol CO2m-2s-1 from T1 to T4.

RESUMO A lima ácida Tahiti é uma espécie de grande importância econômica em todo o mundo. Em território brasileiro, a produção concentra-se nos estados de São Paulo e Pará, onde geralmente é enxertada em limão-cravo. Este estudo tem como objetivo analisar o efeito de diferentes lâminas de irrigação na produção de frutos, fenologia e trocas gasosas de lima ácida Tahiti enxertada em citrumelo Swingle. A irrigação foi realizada durante o primeiro ano, com quatro lâminas de irrigação diferentes em um delineamento de blocos ao acaso com 5 blocos e 4 tratamentos, para manter o potencial matricial do solo nas seguintes faixas: T1: abaixo de -50 kPa, T2: de -30 a -50 kPa , T3: de -10 a -30 kPa e T4: acima de -10 kPa. Foram medidos florescimento, taxa de assimilação de carbono (A), condutância estomática (gs), transpiração (E) e produção de frutos. Os frutos foram colhidos mais cedo no tratamento mais irrigado, T4, e a produtividade aumentou de 2,22 para 6,89 kg por planta de T1 para T4. O peso médio dos frutos aumentou de 78,6 para 96,1 g de T1 para T4. A assimilação de carbono aumentou de 6,89 para 9,51 μmol CO2 m-2 s-1 de T1 para T4.

Abstract Sugarcane pre-sprouted plantlets (PSP) production system is an innovative method to enhance crop multiplication rate. Determination of crop evapotranspiration (ETc) is crucial for water requirement identification throughout the plant cycle for irrigation management. ETc can be satisfactorily measured by weighing lysimeters. The objective of the study was to construct and calibrate three low-cost weighing lysimeters to measure ETc of PSP. The built lysimeters had 0.6909 m2 area (1179 mm × 586 mm), with 400 mm depth supported by 3 load cells. Lysimeters calibration showed excellent precision measurements, due to high linear correlation (R2 = 1.0000) between electric signal and equivalent mass, high accuracy, confirmed by mean absolute error between 0.0272 and 0.0382 mm, mean square error between 0.0011 and 0.0024 mm2 and Willmott's index of agreement (d) equal to unit. Maximum hysteresis (0.1951 mm) and hysteresis at full scale (0.4492%) did not compromise the evaluations. Daily ETc measurements showed variation of 0.27 mm among lysimeters and were coincident with daily course of reference evapotranspiration (ETo). The cost of the equipment was low, except for the data acquisition system. Therefore, lysimeters presented low cost and were adequate to measure ETc of PSP in greenhouse-grown.

ABSTRACT: Evapotranspiration (ET) is the main component of water balance in agricultural systems and the most active variable of the hydrological cycle. In the literature, few studies have used the forecast the day before via Artificial Neural Networks (ANNs) for the northern region of São Paulo state, Brazil. Therefore, this aimed to predict the reference evapotranspiration for Jaboticabal, the major sugarcane-producing region of São Paulo state. We used a historical series of data on average air temperature, wind speed, net radiation, soil heat flux, and daily relative humidity from 2002 to 2012, for Jaboticabal, SP (Brazil). ET was estimated by Penman-Monteith method. To forecast reference evapotranspiration, we used a feed-forward Multi-Layer Perceptron (MLP), which is a traditional Artificial Neural Network. Numerous topologies and variations were tested between neurons in intermediate and outer layers until the most accurate were obtained. We separated 75% from data for network training (2002 to 2010) and 25% for testing (2011 to 2013). The criteria for assessing the ANN performance were accuracy, precision, and trend. ET could be accurately estimated with a day to spare at any time of the year, by means of artificial neural networks, and using only air temperature data as an input variable.

O jiloeiro é uma hortaliça tipicamente tropical, com grande exigência térmica e hídrica, representando importância econômica em diversas regiões no Brasil. Objetiva-se com esse trabalho desenvolver e testar modelos para previsão de características fenométricas vegetativas, como altura da planta, biomassa seca e fresca da parte aérea, número de folhas e área foliar por planta, além das relacionadas diretamente à produção, como o número acumulado de frutos (NFRUTOS) e produção acumulada por planta (PAP), em função de graus-dia, para quatro cultivares de jiló, sendo duas comerciais (Esmeralda e Verde Claro) e duas introduzidas pelo IAC (Cardoso e Bernacci). O índice térmico permitiu bons ajustes das regressões lineares apresentando elevados valores de coeficientes de determinação (R2) para a maioria das características estudadas. O teste das equações foi feito com dados do segundo ano produtivo, para as cultivares Cardoso e Bernacci visando às características NFRUTOS e PAP, apresentando bom desempenho devido aos elevados valores de R2 e todas dentro do intervalo de confiança de 95% de probabilidade. Desta forma, o método proposto, ajustado para as cultivares de interesse, torna-se ferramenta relevante para estimações de início e duração de estádios fenológicos, tal como a produtividade final em jiloeiros.

The 'jiló' plant is a typical horticultural crop with a high thermal and water requirement with a bitter flavor fruit and possessing economical importance in several regions of Brazil. The objective of the study was to develop and to validate models for forecasting phenometric vegetative characteristics as the crop height, dry and fresh biomass of the aerial part, number of leaves and leaf area per plant and also the ones related directly to the production as the accumulated number of fruits (NFRUTOS) and accumulated production per plant (PAP), in function of thermal index for four cultivars of 'jiló', being two commercial and two introduced by IAC. The thermal index allowed good adjustments of the linear regressions presenting high values of R2 for most of the characteristics of interest. The validation of the equations was made with data of the second productive year for cultivar Cardoso and Bernacci for the characteristics NFRUTOS and PAP presenting good agreement due to the high values of R2 and all inside the interval of confidence of 95% of probability. The presented method, after adjusted for specific cultivar, can be used as important tool to estimate beginning and duration of phenological stages as well as final yield of crop.