Sistema computadorizado para preparo e aplicação de soluções nutritivas com base na estimativa da transpiração do tomateiro cultivado em casa de vegetação / Computer system for preparing and applying nutrient solutions with base on the transpiration estimate of tomato cultivated in greenhouse

AUTOR(ES)

Antônio José Steidle Neto

DATA DE PUBLICAÇÃO

2007

RESUMO

In soilless and hydroponic culture, continuous monitoring and frequent adjusts of the fertilizer concentration in nutrient solution to be delivered are essential to optimize plant growth. In this work, low cost electronic circuits were proposed, calibrated and validated for real time measurements of electrical conductivity from 0.10 to 10.15 dS m-1 and temperature with purpose of compensation from 10 to 40 C. In addition, two techniques of preparing, adjusting and applying nutrient solutions were evaluated in tomato plants cultivated in sand substrate under greenhouse conditions. The first technique, denoted automatic system, utilized the Penman-Monteith evapotranspiration model as decision support regarding the suitable nutrient solution concentration and appropriate time intervals between application events. The second technique, denoted conventional system, utilized manually adjusted nutrient solutions and fixed intervals between fertigation events. Despite an increment of 16% in the tomato productivity cultivated under the automatic system as compared to the conventional one, production variations among plants, possibly due to cultivar characteristics, increased the experimental error and then prevented the identification of statistical differences of the fruit size, total soluble solid contents and total and commercial productivity. Additionally, the automatic system provided better results regarding irrigation water use efficiency, which was 45% superior to the conventional system. In this way, the results suggest that the automatic system has an enormous potential to reduce fertilizer use, labor and environmental problems associated with the discard of effluents from soilless and hydroponic culture.

ASSUNTO(S)

fertigation condutividade elétrica greenhouse culture in substrate fertirrigação transpiração transpiration electrical conductivity sistemas de controle cultivo em substrato agrometeorologia casa-de-vegetação control systems

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