Hi,
I have experience for 15+ years in electronics/embedded development. I have several years of advanced AVR/arduino development, including library development from scratch. Practically all Arduino boards used, like: 2009, 2010, UNO, MEGA, NANO, MICRO, MINI and others like DigiSpark (attiny85) and DUE (ARM Cortex-M3). Several shields used like Ethernet (W5100, ENC28J60, etc.) with various IP protocols implementation, various graphical TFTs with and without touchscreen and various BUS types (parallel, SPI, I2C, etc.), all kinds of sensors and buses, serial and parallel memories, etc.
I propose using an arduino Mega2560, using its 16 analog inputs for the soil moisture sensors, 16 other I/Os for connecting relays to control the water pumps and a "datalogger" shield (SD card and RTC) for recording/replaying a CSV file. An ESP8266 based interface (ESP-12 module) for wifi support. For air temperature/humidity a simple DHT11, with an I/O for controlling a fan (relay or power transistor).
Further details to be discussed in case I get awarded. This bid is only for firmware development and documentation - in case a prototype in needed, can be arranged later at extra cost.
If you are interested in my bid, please let me know some more details about your project and I'll be able to answer you back telling if I'm up to the task or not.
PS: tambem sou Português, mas respondi em inglês por questões de coerencia :)
Best regards,
Carlos.