Models have played an important role in scientific research for a long time. The crop models try to simulate the functioning of the atmosphere-soil-plant system with the help of computers. These models can be effective tools in research, education and solving agricultural and environmental protection related problems. The 4M package includes a crop model and several accessories that help to operate the model. The 4M crop model is a daily-step, deterministic model that simulates the water and nutrient balance of the soil, the soil-plant interactions and the plant development and growth. To mention some examples: (1) The package can be used in education to carry out 'zero-cost' virtual agricultural experiments and to challenge and enhance the system oriented thinking of the students. (2) In research it can be used for designing experiments and estimating the present and future characteristics of the investigated system. (3) In practical applications the package can be used to prepare agro-technological advise (fertilization, irrigation, etc.) for farmers, and to carry out economical analyses on farm level.

crop model, estimation method, education