Benjamin Crljenković, a master’s student at the University of Sarajevo, spent the last semester working on his master’s thesis. The title of the candidate’s master’s thesis was “Comparative analysis of different software models for determination of irrigation requirements in maize”, and the mentor during its preparation was Assoc. Dr. Sabrija Čadro from the University of Sarajevo.of Sarajevo and the University of Banja Luka

In the introduction of the paper, Benjamin points out the importance of water, especially focusing on its importance in agriculture as one of the largest consumers of fresh water, which is explained through examples of the positive effect of irrigation on many aspects of plant production. The importance of water is then placed in the context of the challenges humanity is currently facing, with climate change being highlighted. In such conditions, as stated, a more rational use of water resources is needed, which can be achieved by a detailed analysis of the hydrological cycle. These analyzes are based on balancing the content of water in the soil, and for this purpose today there is a large number of software tools, applications and models available and they can even have a much wider use than just the above mentioned. At the end of the introduction, the issues of the research and the answer to the previously defined challenges are briefly presented.

The defined basic goal of the research is to determine the possibility of using several different software models for calculating the irrigation requirements in the maize crop, i.e. giving recommendations for the choice of software models according to different groups of users. In accordance with the set goal of the research, several specific goals were defined


  1. collection of data on climatic factors on the sample plot,
  2. collection of data on land factors on the sample plot,
  3. setup and use of software models to calculate crop irrigation requirements under the exact conditions as recorded during the experiment, and
  4. comparison of values generated by different software, analysis and comment of the obtained results.

The methodology of the work shows primarily the area and the crop on which the research was carried out, through a group of observed meteorological, pedological and agronomic characteristics. The research was carried out in the period from May to October 2021, at the test site of the Faculty of Agriculture and Food in Butmir, near Sarajevo, on the BL-43 hybrid maize crop that was sown for the purpose of a joint experiment within the project “Promoting SMART Agricultural WATER Management in Bosnia and Herzegovina – SMARTWATER”.

After collecting and preparing the mentioned data, it was imported into four used software models and tools for estimating irrigation requirements, namely: CROPWAT 8.0, EXCEL-IRR, AquaCrop v6.1 and SIMDualKc. The results of the modeling, that is, the products of the use of software tools, are later presented through evapotranspiration values, soil water depletion or its state of humidity, as well as the irrigation requirements or the scheduled irrigation dates.

The year in which the research was carried out was extremely dry, where, in addition to the high temperatures compared to the multi-year average, there was also a lack of precipitation during the entire vegetation period. Precipitation for the vegetation period of 2021 at the research location was 189 mm, while the multi-year average is 403 mm. The determined type of soil at the research location is alluvium, clay loam textural class. Therefore, it is a heavier type of soil, with a maximum depth of root penetration of up to 1.2 m. Maize (hybrid BL-43) was sown on May 7, and harvested on September 30, 2021, which means that the growing season lasted a total of 147 days. Sowing was done at an inter-row spacing of 70 cm, and the row spacing was an average of 25.7 cm, which resulted in a total of 55,580 plants per hectare.


Different results were obtained based on the software models used, the specifics of preparation, volume and data entry means. First of all, with the daily value of crop evapotranspiration, significant variations in the calculated crop evapotranspiration are noticeable in different models at the beginning of the growing season. By comparing the average values of ETc and the values obtained by individual models, a high correlation was found. The correlation factor for CROPWAT and EXCEL-IRR was 0.99, while for SIMDualKc it was 0.96 and 0.94 AquaCrop. Although these are relatively high factors, which prove the similarity of the results of all the models used, a greater variation in the values generated by SIMDualKc and AquaCrop is noticeable.

The models also differ in the distribution of irrigation requirements by months of vegetation duration, i.e. the total amount of water needed. The highest irrigation requirements were obtained with simpler models – CROPWAT and EXCEL-IRR, where they amounted to 360 mm, slightly less with SIMDualKc (330 mm), and the lowest values were given by AquaCrop, only 270 mm. A different number of irrigations events was obtained, so CROPWAT and EXCEL-IRR predict 12 meals each, SIMDualKc 11, and AquaCrop only nine.

It is important to emphasize that, although different amounts of required water and the number of irrigations events were estimated, the soil water depletion never fell below the limit of readily available water. This confirms the correctness of each of the models used. Based on the preparation and use of these four models, it was concluded that each of them has certain advantages and that practical application depends on the type of user and available data. For example, farmers will prefer to use simple models such as CROPWAT and EXCEL-IRR, while researchers and professionals will use more precise models such as SIMDualKc and AquaCrop.

Based on the research results, the following conclusions were drawn:

  1. There is a big number of different models and tools for calculating evapotranspiration and simulating soil water balance, and they differ in complexity, approach, methods used, purpose, etc.,


  2. Different software tools have different requirements regarding input parameters, which can be a problem for users, especially in the absence of meteorological and other measuring stations,


  3. Despite the fact that they use the same method for calculating the reference evapotranspiration, all the models used have different results of calculating the evapotranspiration of the crop and accordingly propose different irrigation terms,


  4. By comparing the CROPWAT, EXCEL-IRR, AquaCrop and SIMDualKc models, it was determined that there are no large deviations between the values calculated using the four mentioned software tools,
  5. Since the use of all models achieves satisfactory results, it is recommended that farmers, non-professionals and inexperienced users use simpler tools for determining irrigation requirements, such as EXCEL-IRR or CROPWAT,


  6. More demanding models – AquaCrop and SIMDualKc should be refined, in order to be more intuitive and facilitate users’ daily use.


Master’s thesis defense took place on September 14, 2022, before a three-member committee consisting of prof. dr Drena Gadžo, prof. Dr. Jasmin Grahić and Assoc. Dr. Sabrija Čadro, and with a successful defense the candidate obtained an academic and professional title of Master of Plant Production.

As a participant in the SMARTWATER project, Benjamin attended summer schools and advanced courses that were held during the first two years of the project’s implementation, and the acquired knowledge was very useful during the definition and creation of the master’s thesis. Due to all of the above, he expresses great gratitude for the opportunity of being directly involved in the activities of the project “Promoting SMART Agricultural WATER Management in Bosnia and Herzegovina – SMARTWATER”.