Jizhang Wang

Integration of an environment information acquisition system with a greenhouse management expert system

Abstract A real‐time environment information acquisition system is essential if models and vegetable‐crop information are to be integrated with a greenhouse management expert system for good decision making. Our greenhouse management expert system has four functional modules: (1) cultivation techniques, (2) pest and disease diagnosis and prevention, (3) nutrient deficiency diagnosis and fertilisation, and (4) environment control. The hardware and software of the environment information acquisition system are incorporated into the expert system, which also offers a multi‐interface for sensors and is easily extended and maintained. Implementation was accomplished with the whole system to ensure its reliability and applicability for expert system, on‐line decision making. The results show that a dynamic integration of a greenhouse management system and an environment information acquisition system can supply sufficient information for good control strategies and for decision‐support.

Modeling the Wetting Patterns in Cultivation Substrates under Drip Irrigation

ABSTRACT Liu, Z.; Li, P.; Hu, Y., and Wang, J., 2015. Modeling the wetting patterns in cultivation substrates under drip irrigation. Information on the depths and widths of the wetted zone of substrate is a pre-requisite for the design and operation of drip irrigation systems. A semi-empirical model was developed using the dimensional analysis method to simulate the geometry of wetted substrate zone under drip irrigation. The simulated values of the wetted width and wetted depth were compared with those obtained through field experiments to test model applicability. Statistical analysis revealed that the values of Mean Square Error, Mean Error and Model Efficiency were 1.11 cm, 0.53 cm and 80.6% at least respectively. For the prediction of wetted width and depth of substrate T1 and T2, therefore, the develop model can be used to describe wetted substrate patterns under drip irrigation system with an emitter.

Wetting patterns and water distributions in cultivation media under drip irrigation

The infiltration and distribution of water in two cultivation media are examined.The wetting body is shaped like a rotating projectile.The maximum horizontal migration radius occurs at 3-6cm below the medium surface.The smaller irrigation flow is more suitable for irrigation in the test substrates.Models were used to express the migration distance and the size of wetting body. The infiltration and distribution of water in two kinds of cultivation media are examined under different conditions of drip irrigation in terms of flow, volume, and initial medium water content and the models were used to express the horizontal migration distance and the vertical migration distance, and express the size of the wetting body indirectly. The results show that in different media, the wetting body is shaped like a rotating projectile, whose maximum horizontal infiltration radius occurs at 3-6cm below the medium surface. Under drip irrigation of the same volume, the volume of the medium wetting body declines while the horizontal and vertical migration rates of the medium wetting front both rise with increasing irrigation flow; additionally, there are declines in medium water content, and water content increment at the same position. Under drip irrigation of the same duration, increasing irrigation flow leads to increases in the volume of the medium wetting body, horizontal and vertical migration rates of the medium wetting front, surface medium water content, and the medium wetting range. Under drip irrigation at the same flow, there are increases in the width and depth of the medium wetting body, declines in the migration rate of the medium wetting front, and horizontal rises in the progressively decreasing rate of medium water content as the irrigation volume increases. Under drip irrigation of the same duration, the horizontal migration rate of the medium wetting front rises while the vertical migration rate of the medium wetting front declines with increasing initial medium water content; correspondingly, medium wetting body tends to flatten gradually as a whole, and the increment of medium water content at the same position is diminished.

Studies on Photosynthesis Model of Mini-Cucumber Leaf in Greenhouse

Photosynthesis (Pn) is the most important parameters in greenhouse climate control system based on model. Temperature and radiation are important climate factors affecting crop photosynthesis rate. The purpose of this study is to quantitatively investigate the effects of both temperature and photosynthetically active radiation (PAR) on the cucumber Photosynthesis rate. Experiments with different weather were conducted in greenhouse of Jingkou Institute of Vegetable. The results show that under the fine and cloudy weather, the curve of photosynthesis had two peaks, with an obvious midday depression at 11:00am–12:00am. But under the rainy weather, there is no depression. Based on experimental data, the relationship between photo-temperature and photosynthesis were established. The coefficient of determination (R 2) of the model is 0.953. And when temperature was 28.7°C, PAR was 1311μmolm-2s-1, the photosynthesis would reach to a maximum value of 20.13 CO2μmolm−2s−1. The model developed in this study can predict photosynthesis with different temperature and radiation. And it also can give the optimum parameters of greenhouse climate control.

Decision Support System for Greenhouse Environment Control Based on Model

Greenhouse environment control and manage mainly emphasize on the growth of crop, and seldom take into account the cost of control. In this research, the decision support system (DSS) of greenhouse environment control based on model is put forward. In this system, models included greenhouse crop growth model, greenhouse control effect model and control cost model. Then knowledge-base, model-base and database are established including the aspects of crop growth, environment control in greenhouse. Based on those, the software of greenhouse environment control decision support system (GHMDS) is developed. With consideration to both crop growth and economic profits, the system combined the advantages of “Model Based Reason (MBR)” and “Knowledge Based Reason (KBR)”. By this system, the optimized dynamic parameters of environment control under different weather conditions and crop growth stage can be given. And it also can forecast market period, growth stage. Connected with greenhouse controller, it can realize intelligent control. The simple man-machine interface of GHMDSS makes the user more convenience and more applicable in greenhouse crop and climate management practices.