ABSTRACT Cacao is a species of great economic and social importance. Expanding the area grown with this crop has been limited by its climatic requirements. Agroclimatic zoning for agricultural sector and creation of land suitability maps by fuzzy logic contribute to such production expansion. In this sense, this study aimed to develop rainfall zoning for cacao in Bahia state using the fuzzy logic method. The used data came from rainfall historical series of 519 meteorological stations distributed throughout the state. Geostatistical analyses were used to quantify the spatial dependence degree of studied variable and kriging was used to develop maps representing mean monthly rainfall. These maps were submitted to continuous classification by fuzzy mapping for identification of high-risk areas for cocoa growing based on rainfall. Based on the fuzzy method, the southern mesoregion of Bahia state presented the highest rainfall uniformity, suggesting that this area is more suitable for cocoa growing.

ABSTRACT The aim of this study was to evaluate drip irrigation as a process, by monitoring the average flow applied by the emitter using tools of statistical quality control. Four kinds of drippers were selected, two inline labyrinth type and two online where one of the inline emitters was not self-compensating and the other, self-compensating emitter. The system was installed in the field and tested for 85 hours, using three kinds of treated domestic sewage effluents and tap water. The system was under statistical control when the emitters were new, however none of the drippers reaches the manufacturer's specification for average flow. The online drippers showed more dispersion for individual flow measurements and the non-self-compensating inline dripper was more accurately for this variable. After the end of experiment, irrigation process was not under statistical control for any kind of emitter. When using treated wastewater effluents for irrigation we recommend a first evaluation before 7 working hours, to implement appropriated correcting procedures to reduce clogging and as a result, maintain the process quality.

RESUMO Microaspersores convencionais, geralmente, apresentam variação de vazão ao longo das linhas laterais. O objetivo deste trabalho foi adaptar microtubos a microaspersores não compensantes (instalados em campo) no intuito de melhorar a uniformidade de emissão de vazão ao longo da linha lateral. Microtubos foram adaptados a três modelos comerciais de microaspersores. Testes foram conduzidos em laboratório e em campo para avaliar o desempenho em quatro diferentes vazões: 40; 50; 60 e 70 L h-1 com pressões variando de 75 a 245 kPa. No geral, os emissores avaliados apresentaram coeficiente de variação de vazão (CVq) menor que 5,5% e uniformidade de distribuição maior que 95%. Esses resultados de uniformidade de emissão ao longo da linha lateral são classificados como excelentes. Microtubos atuando como bocal compensante em microaspersores convencionais, já em uso no campo, operaram eficientemente nos microaspersores com vazões de até 70 L h-1 e não alteraram o padrão original de distribuição espacial de água. Pequenas variações da vazão, ao longo da linha lateral, podem ocorrer, porém de forma aleatória, o que é comum em emissores autocompensates devido ao CV de fabricação, indicando que a técnica de microtubos é eficiente no controle da variação de pressão em microaspersores não auto-compensantes.

ABSTRACT Microsprinkler non-pressure compensating nozzles usually show water flow variation along the lateral line. This study aimed at adapting microtubes into non-compensating system of microsprinklers previous installed in the field, as a self-compensated nozzle, to improve the flow uniformity along the lateral line. Microtubes were adapted to three types of commercial microsprinklers. Tests were conducted, both in the laboratory and in field, to evaluate the microsprinkler performance at four different flows (40, 50, 60 and 70 L h-1) under pressure head range from 75 to 245 kPa. Nozzles presented coefficient of flow-rate variation (CVq) lower than 5.5% and distribution uniformity (DU) greater than 95%, which are classified as excellent. The original spatial water distribution of the microsprinkler did not change by using microtube as a nozzle. This device adapted to non-pressure compensating microsprinklers are functional and operate effectively with flows ranging up to 70 L h-1. Small variations at microsprinkler flows along the lateral line can occur, however, at random manner, which is common for pressure-compensating nozzles. Therefore, the microtube technique is able to control pressure variation in microsprinklers.

Propôs-se, neste trabalho, avaliar o risco potencial da vinhaça em proporcionar a salinidade e sodicidade das águas subterrâneas em área de várzea cultivada com cana-de-açúcar. O experimento foi conduzido em uma Usina da Mata Sul de Pernambuco durante o período de dezembro de 2010 a setembro de 2011. O dispositivo experimental adotado foi composto de uma malha georreferenciada de 81 poços de monitoramento distribuídos ao longo de uma área de 7,5 ha constituindo três subáreas com 2,5 ha, todas cultivadas com cana-de-açúcar. Na área foram aplicadas doses equivalentes a 50, 60 e 65 m³ ha-1 de vinhaça de mosto de melaço. Para a avaliação da qualidade da água subterrânea foram realizadas seis amostragens e analisados os parâmetros CE, pH, Na+, Ca2+, Mg2+ e RAS. A aplicação de doses de vinhaça até 65 m³ ha-1, em áreas de várzea, para os parâmetros analisados, não proporcionou riscos de salinização das águas subterrâneas nem, tampouco, a CE e a RAS para a salinidade e sodicidade no período avaliado. O monitoramento dos parâmetros químicos do lençol freático mostrou, ao longo do tempo, redução de suas concentrações em função da precipitação pluviométrica ocorrida no período estudado.

This study evaluated potential risk of vinasse to provoke salinity and sodicity in groundwater in a lowland area under sugarcane crop. The research was carried out in Pernambuco State, in the Northeast of Brazil, from December 2010 to September 2011. A georeferenced grid of 81 wells over 7.5 ha (three subareas with 2.5 ha each) under sugarcane crop was monitored. Vinasse was applied at three rates 50, 60 and 65 m³ ha-1 from molasses fermentation. Quality of groundwater was monitored through six samples along period of plant growing. EC, pH, Na+, Ca2+, Mg2+ and SAR were measured. Rate up to 65 m³ ha-1, in lowland areas, for the variables analysed, provided no risk to groundwater for salinity and sodicity, as well as EC and SAR for salinity and sodicity during the experimental stage. This study showed that rainfall provided reduction of salt concentrations in groundwater under monitoring along the time.

RESUMO Nesse trabalho foi estudado o limite da concentração eletrolítica (TEC) em dois solos distintos do estado de Pernambuco. O experimento foi conduzido no Laboratório de Química e Salinidade do Solo da UFRPE. Cada tipo de solo foi acondicionado em cinco funis de Buchner, os quais foram submetidos aos tratamentos compostos por cinco soluções com CE de 0,5; 1,0; 2,0; 4,0 e 8,0 dS m-1. Em cada funil foram adicionadas soluções com relação crescente de NaCl/CaCl2 para obter 10 valores crescentes de relação de adsorção de sódio (RAS), de 0 a 100. As soluções foram aplicadas por meio de sistema tipo “frasco de Mariotte”, mantendo-se carga constante de ~2 cm (potencial de pressão). Após percolado um litro de solução, iniciou-se a coleta do volume drenado num intervalo de tempo conhecido, até o fluxo constante. Os dados foram usados na equação de Darcy, calculando-se a condutividade hidráulica saturada dos solos (Ksat) e, com modelo matemático, calculou-se a TEC, com uma redução de 20% da Ksat. Com o aumento da RAS, observou-se comportamento similar nos dois tipos de solo, no que se refere à redução da Ksat, embora o decréscimo relativo desta tenha sido maior no solo com elevado teor de argila, quando a RAS foi igual a 100.

ABSTRACT This research studied threshold electrolyte concentration (TEC) of irrigation water and its effect on the infiltration rate of two contrasting soils from Pernambuco state, Brazil. The experiment was conducted in the Soil Chemistry and Salinity Laboratory of Federal Rural University of Pernambuco. Each soil was packed in five Buchner funnels, where one funnel from each soil was submitted to treatment with solution of electrical conductivity (EC) of 0.5, 1.0, 2.0, 4.0 or 8.0 dS m-1. For each funnel containing soil, an increasing ratio of NaCl to CaCl2 was applied in a treatment solution to achieve 10 increasing values of sodium adsorption ratio (SAR) from 0 to 100. These solutions were applied through a Mariotte bottle, with a constant hydraulic head of ~2 cm (pressure potential). After a liter of solution had drained, in the flux was collected for a known time interval, until steady state was reached. Darcy’s equation was used to calculate saturated hydraulic conductivity (Ksat) and a mathematical model used to calculate the TEC as a 20% reduction in Ksat. By increasing SAR similar behavior was noted between the two soils, whereby Ksat decreased, although the relativedecrease in Ksat was greater for SAR of 100 in the soil with higher clay content.