Despite of the agronomic importance for water management, few studies of sugarcane roots have been performed under field conditions during the crop cycle. The aim of this study was to determine the cumulative root density (L A ), root distribution on soil profile and the effective rooting depth (ERD) for three sugarcane cultivars using the minirhizotron method. A field experiment was done with sugarcane cultivars IACSP94-2094, IACSP94-2101 and SP79-1011 grown under subsurface drip fertigation. Soil chemical and physical characteristics were also evaluated. Root evaluations were taken at 38, 58, 123, 185 and 205 days during the second ratoon, considering the soil profile until 0.8 m depth. The highest L A and root growth rates were found up to 0.4 m soil layer for all cultivars. Root growth rate varied during the crop cycle, with the highest values being found between 38 and 58 days after ratoon (DAR). There was a genotypic variation in root growth, with IACSP94-2101 showing the highest L A of 12.9 mm cm

The present study aimed to evaluate the development, yield and quality of four sugarcane cultivars fertigated by subsurface drip system. The experiment was carried out in Campinas-SP, Brazil, from January 2012 to November 2013, with the cultivars SP79-1011, IACSP94-2101, IACSP94-2094 and IACSP95-5000 subjected to daily irrigations. The irrigations depths were applied to bring soil moisture to field capacity. Soil moisture was monitored using soil moisture probes. Samples were collected along the crop cycle in order to evaluate crop development and yield, at the end of the first and second ratoons. Stalk height showed good correlation for the estimation of crop yield, with R2 equal to or higher than 0.96. The cultivar IACSP95-5000 showed the highest yield in the first ratoon. In the second ratoon the highest yield was observed in IACSP94-2101, followed by IACSP95-5000 and SP79-1011. Considering the yield results associated with the technological analysis, such as soluble solids content and apparent sucrose, the cultivar IACSP95-5000 excelled the others in the cultivation under subsurface drip irrigation.

The pre-sprouted sugarcane plantlets (PSP) system aims the production of healthy and vigorous plants in reduced time, reducing the number of stalks needed for planting. Irrigation is used in all PSP system stages and water management plays an important role. Stage 1 acclimation follows the budding stage and lasts for approximately 21 days. At this stage the plantlets are grown within an agricultural greenhouse to improve initial development. The objectives of this trial were: to identify the irrigation management which results in highest plantlet growth; to evaluate if responses to irrigation management depends on the cultivar; to evaluate water consumption and water use efficiency at early stage under PSP system; and to assess the water management effect on substrate water matrix potential and stomatal conductance in the cultivar IACSP95-5000. The experimental design was a split-plot randomized block design with four replications. Treatments applied in the plots were different irrigation depths based on daily reference evapotranspiration (ETo): 96, 80, 64 and 48%, estimated by Penman-Monteith method. In the subplots, there were sugarcane cultivars IAC91-1099, IACSP95-5000 and IACSP97-4039. Irrigation management based on 80% ETo resulted in higher growth, dry mass accumulation and greater leaf area. Water use efficiency was not influenced by irrigation management. IAC91-1099 presented higher overall growth, leaf area and dry mass accumulation. Water consumption was cultivar-dependent in irrigation managements using 80 and 96% of ETo. Water use efficiency was higher in IAC91-1099 and lower in IACSP95-5000. Lower substrate water matrix potential reduced leaves stomatal conductance, impairing IACSP95-5000 plantlet growth.

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CALIBRATION AND ACCURACY OF TWO ELECTROMAGNETIC METHODS OF SOIL MOISTURE MEASUREMENT IN OXISOL     ANDRÉ LUIZ BARROS DE OLIVEIRA SILVA1; REGINA CÉLIA DE MATOS PIRES2; AUGUSTO YUKITAKA PESSINATTI OHASHI3; GLAUCIA CRISTINA PAVÃO4 E GABRIEL CONSTANTINO BLAIN5   1PhD student, Postgraduate in Tropical and Subtropical Agriculture, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. andreluiz.biologia@gmail.com. 2 Scientific researcher, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. rcmpires@iac.sp.gov.br. 3PhD student, Postgraduate in Tropical and Subtropical Agriculture, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. augusto.ohashi@gmail.com. 4PhD student, Postgraduate in Tropical and Subtropical Agriculture, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. glauciapavao@gmail.com. 5Scientific researcher, Agronomic Insitute, 1481 Barao de Itapura Ave, Campinas, P.O. Box: 28, Sao Paulo, Brazil. gabriel@iac.sp.gov.br.     1 ABSTRACT   Accurately measuring soil moisture is an important technological challenge. Sensors development and validation for agricultural applications is a relevant research theme. Electromagnetic techniques have been shown to be useful for soil moisture measurement. However, these techniques typically benefit from calibration. In this context, the aim of this study was to calibrate and evaluate the accuracy and precision of the soil moisture measured by two devices with different electromagnetic principles: Frequency Domain Reflectometry (FDR) e High Frequency Soil Impedance (HFSI) in the laboratory with in oxisol. The probes used were Diviner 2000 and Hidrofarm HFM 1010. Soil moisture was measured using both FDR and HFSI probes. A large variation in soil moisture values occurred during the experiment, as it varied from 0.489 m3 m-3 to 0.077 m3 m-3. Both electromagnetic methods showed good correlation compared to the standard method (gravimetric). HFSI probe overestimated the soil moisture values when compared to the gravimetric method, while FDR underestimated the values.   Keywords: capacitance probes, HFSI sensor, FDR sensor, high frequency soil impedance.     SILVA, A. L. B. O.; PIRES, R. C. M.; OHASHI, A. Y. P.; PAVÃO, G. C.; BLAIN, G. C. CALIBRAÇÃO E PRECISÃO DE DOIS MÉTODOS ELETROMAGNÉTICOS DE MEDIÇÃO DE UMIDADE DO SOLO EM OXISOL     2 RESUMO   Medir a umidade do solo com precisão é um importante desafio. O desenvolvimento e validação de sensores para aplicações agrícolas é um tema de pesquisa relevante. As técnicas eletromagnéticas demonstraram ser úteis para a medição da umidade do solo. No entanto, essas técnicas geralmente se beneficiam da calibração. Nesse contexto, o objetivo deste estudo foi calibrar e avaliar a exatidão e precisão da umidade do solo, medida por dois dispositivos com diferentes princípios eletromagnéticos: Reflectometria no Domínio da Frequência (FDR) e Impedância do Solo de Alta Frequência (HFSI) em laboratório em latossolo. As sondas utilizadas foram Diviner 2000 e Hydrofarm HFM 1010. A umidade do solo foi medida usando as sondas FDR e HFSI. Houve uma grande variação nos valores de umidade do solo durante o experimento, de 0,489 m3 m-3 a 0,077 m3 m-3. Ambos os métodos eletromagnéticos mostraram boa correlação em comparação com o método padrão (gravimétrico). A sonda HFSI superestimou os valores de umidade do solo quando comparada ao método gravimétrico, enquanto a FDR subestimou os valores.   Palavras-chave: sondas de capacitância, sensor HFSI, sensor FDR, impedância do solo em alta frequência.