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With the development of technologies such as the Internet of Things and Big Data, agriculture is entering the digital age. Modern information technology and intelligent equipment are the development direction of agriculture. In this paper, a remote-control system for greenhouse environment was developed based on Raspberry Pi, MySQL and Android. The system consists of a greenhouse control system (subsystem A), an environment monitoring system (subsystem B), a MySQL remote database (subsystem C), and an Android monitoring software (subsystem D). The subsystem A is used to implement automatic fertigation and collect data from subsystem B, which will be uploaded to cloud server database (subsystem C). The subsystem B is used to monitor the environmental parameters in the greenhouse such as air temperature/humidity, soil temperature/humidity etc. The subsystem C is used for storage of greenhouse environment data and communication between subsystem B and subsystem D. The subsystem D is used for data visualization including real-time display, storage and analysis of greenhouse environmental data, and remote control of fertigation system including the EC/pH control of the fertigation solution, irrigation scheduling, and fertigation settings. A proportional-integral-derivative (PID) control algorithm is used for the fertigation process of the subsystem A. The low-power LoRa technology is used for subsystem B to achieve low-power long-distance data transmission, which is especially suitable to greenhouses. All monitoring settings can be operated remotely by users.

Nitrogen (N), phosphorus (P), potassium (K), and water are four crucial factors that have significant effects on strawberry yield and fruit quality. A quadratic regression orthogonal rotation combination experiment that involved 36 treatments with five levels of the four variables (N, P, and K fertilizers and water) was executed to optimize the fertilization and water combination for high yield and quality. SSC/TA ratio (the ratio of soluble solid content to titratable acid) was selected as the index of quality. Results showed that the N fertilizer was the most important factor, followed by water and P fertilizer, and the N fertilizer had a significant effect on yield and SSC/TA ratio. By contrast, the K fertilizer had a significant effect only on yield. N×K fertilizer interaction had a significant effect on yield, whereas the other interactions among the four factors had no significant effects on yield and SSC/TA ratio. The effects of the four factors on the yield and SSC/TA ratio were ranked as N fertilizer > water > K fertilizer > P fertilizer and N fertilizer > P fertilizer > water > K fertilizer, respectively. The yield and SSC/TA ratio increased and then decreased when NPK fertilizer and water increased. The optimal fertilizer and water combination was 22.28–24.61 g/plant Ca (NO3)2⋅4H2O, 1.75–2.03 g/plant NaH2PO4, 12.41–13.91 g/plant K2SO4, and 12.00– 13.05 L/plant water for yields of more than 110 g/plant and optimal SSC/TA ratio of 8.5–14.