Guilherme Vieira do Bomfim

Characterization and selection method of Venturi injectors for pressurized irrigation

Venturi-type chemigation injectors are widely used due to their advantages: they do not require electric power and are cheap to operate. However, they also generate considerable energy losses which affect the pressure in the system. The correct characterization of these systems requires pressures to be correctly set at the inlet, injector and outlet points in relation to main and injected solution flows. These analytical relationships, as described in the International Organization for Standardization’s standard ISO 15873:2002, can be obtained theoretically, although it is recommended that the manufacturer should determine the real behavior of the injector by operational tests. These relationships should also be provided graphically in the form of nomograms in order to facilitate the association of the variables involved and the subsequent selection of a specific model or class and type of assembly. In order to make the right choice, it is also necessary to have precise information on the irrigation sub-units that it feeds and the grower’s fertilization program.

IRRIGATION DEPTHS AND YIELD RESPONSE FACTOR IN THE PRODUCTIVE PHASE OF YELLOW MELON

Local knowledge about irrigation management in yellow melon can promote higher precision to water supply for irrigation purposes, increasing productivity and reducing production costs. The aim of this study was to evaluate the effects of different irrigation depths for yellow melon production and on yield response factor to water (Ky) in the productive phase. The experiment was carried out in Fortaleza, state of Ceara, Brazil, in complete randomized blocks with six treatments, four replicates and six plants per plot. Treatments were applied from intermediate (III) to final (IV) physiological state with water depths equivalents to 25%, 50%, 75%, 100%, 125% and 150% of the crop evapotranspiration (ETc). Ky was calculated according to FAO-33 report methodology in the range from 25% to 100% ETc. The variables analyzed were number of fruits per plant, polar and equatorial diameters, fruit fresh weight, commercial yield, skin and pulp thickness, and soluble solids. Treatments influenced the number of fruits per plant, equatorial diameter, fruit fresh weight, commercial yield, and soluble solids. The best results were reached with commercial yield equal to 32.2 Mg ha-1, 1.46 fruits per plant, equatorial diameter equal to 16.3 cm, fruit fresh weight equal to 2.3 kg and soluble solids equal to 12 oBrix with 100.3% ETc in the productive phase. The crop was tolerant to water supply reduction on the productive phase (Ky < 1) through daily irrigation with controlled water deficit.

Formas de aplicação e doses de inseticidas sobre Aphis gossypii (Glover) (Hemiptera: Aphididae) em melão amarelo

Para aperfeicoar o manejo fitossanitario de pragas na cultura do melao (Cucumis melo L.), objetivou-se avaliar os efeitos de formas de aplicacao e doses de inseticidas sobre a eficiencia de controle quimico do pulgao A. gossypii. O experimento foi realizado em 2010, na cidade de Fortaleza, Ceara, com melao amarelo cultivado em condicoes de campo. O delineamento experimental foi em blocos ao acaso, arranjo fatorial 2 x 4, com quatro repeticoes e parcelas de seis plantas. Os tratamentos foram duas formas de aplicacao (pulverizacao costal manual e insetigacao por gotejamento) e quatro doses de inseticida (0; 50; 100; 200% da dose recomendada pelo fabricante). Os inseticidas acefato e tiametoxam, testados separadamente, foram aplicados em manejo de rotacao de grupos quimicos. A eficiencia de controle foi avaliada sete dias apos o uso de cada inseticida. O acefato nao apresentou diferenca significativa entre as formas de aplicacao, atingindo eficiencias de controle de 88,95 e 84,09% com 100 e 200% da dose recomendada, respectivamente. O tiametoxam nao diferiu significativamente quanto as formas de aplicacao e doses testadas, apresentando eficiencia de 100% em todos os tratamentos. Atualmente, no Brasil, a utilizacao de acefato no melao esta limitada a aplicacao mecanizada devido ao risco de contaminacao. Diante dessa limitacao, o controle do pulgao em meloeiro amarelo pode ser realizado via insetigacao por gotejo ou pulverizacao costal manual, devendo-se empregar, preferencialmente, 100% da dose recomendada de tiametoxam.